Purification of water from barium: its influence, sources and methods of water purification. Method for removing barium from water Ion-exchange method for removing barium from groundwater

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The document establishes a method for measuring the mass concentration of barium in drinking, surface, underground fresh and waste waters by the turbidimetric method with potassium chromate

2 Assigned characteristics of measurement accuracy indicators

3 Measuring instruments, auxiliary equipment and reagents

3.1 Measuring instruments

3.2 Crockery and materials

3.3 Reagents and standards

4 Measurement method

5 Requirements for safety, environmental protection

6 Operator qualification requirements

7 Measurement conditions

8 Preparing to take measurements

8.1 Sampling and storage

8.2 Preparing the instrument

8.3 Preparation of auxiliary solutions

8.4 Preparation of calibration solutions

8.5 Building a calibration curve

8.6 Checking the stability of the calibration characteristic

9 Taking measurements

9.1 Concentration

9.2 Elimination of interfering influences

9.3 Conducting analysis

10 Processing measurement results

11 Presentation of measurement results

12 Checking the accuracy of measurement results

12.1 General

12.2 Operational control of the measurement procedure using the addition method

12.3 Online control of the measurement procedure using control samples

• GOST 12.0.004-90Organization of labor safety training. General Provisions . Replaced by GOST 12.0.004-2015.
• GOST 12.1.004-91System of labor safety standards. Fire safety. General requirements
• GOST 12.1.005-88System of labor safety standards. General sanitary and hygienic requirements for the air of the working area
• GOST 12.1.007-76System of labor safety standards. Harmful substances. Classification and general safety requirements
• GOST 12.4.009-83System of labor safety standards. Fire equipment for the protection of objects. Main types. Accommodation and service
• GOST 6709-72Water distilled. Specifications
• GOST R 51593-2000Water drinking. Sample selection
• GOST R ISO 5725-6-2002Accuracy (correctness and precision) of measurement methods and results. Part 6. Using precision values ​​in practice
• GOST R 51592-2000Water. General Sampling Requirements
• GOST 10929-76Reagents. Hydrogen peroxide. Specifications
• GOST 14919-83Electric stoves, electric stoves and ovens for domestic use. General specifications
• GOST 1770-74Tableware measured laboratory glass. Cylinders, beakers, flasks, test tubes. General specifications
• GOST 25336-82Tableware and laboratory glass equipment. Types, basic parameters and dimensions
• GOST 29227-91Tableware laboratory glass. Pipettes graduated. Part 1. General requirements
• GOST 3117-78Reagents. Ammonium acetate. Specifications
• GOST 3118-77Reagents. Hydrochloric acid. Specifications
• GOST 3760-79Reagents. Ammonia water. Specifications
• GOST 3774-76Reagents. Ammonium chromic acid. Specifications
• GOST 4108-72Reagents. Barium chloride 2-aqueous. Specifications
• GOST 4459-75Reagents. Potassium chromic acid. Specifications
• GOST 61-75Reagents. Acetic acid. Specifications
• Federal Law 102-FZOn ensuring the uniformity of measurements
• PND F 12.15.1-08Guidelines for Sampling for Wastewater Analysis
• GOST R 53228-2008Non-automatic scales. Part 1. Metrological and technical requirements. Tests
• GOST R 8.563-2009State system for ensuring the uniformity of measurements. Techniques (methods) of measurements
• GOST R 12.1.019-2009System of labor safety standards. Electrical safety. General requirements and nomenclature of types of protection

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FEDERAL SUPERVISION SERVICE
IN THE SPHERE OF NATURE MANAGEMENT

QUANTITATIVE CHEMICAL ANALYSIS OF WATER

MEASUREMENT TECHNIQUE
BARIUM CONCENTRATIONS IN DRINKING,
SURFACE, UNDERGROUND FRESH AND
WASTEWATER TURBIDIMETRIC
METHOD WITH POTASSIUM CHROMATE

PND F 14.1:2:3:4.264-2011

The technique is approved for the purposes of the state
environmental control

MOSCOW 2011

The methodology was reviewed and approved by the Federal Budgetary Institution "Federal Center for Analysis and Assessment of Technogenic Impact" (FBU "FTsAO").

Federal Budgetary Institution "Federal Center for Analysis and Assessment of Technogenic Impact" (FBU "FTsAO")

Developer:

Branch of FBU "CLATI in the Far Eastern Federal District" - CLATI in Primorsky Krai

1. INTRODUCTION

This document establishes a method for measuring the mass concentration of barium in drinking, surface, underground fresh and waste waters by the turbidimetric method with potassium chromate.

Measurement range from 0.1 to 6 mg/dm 3 .

If the mass concentration of barium exceeds the upper limit of the range, then dilution of the sample is allowed so that the mass concentration corresponds to the regulated range.

If the mass concentration of barium in the sample is less than 1 mg/dm 3 , the sample must be concentrated by evaporation.

Calcium at a content of up to 45 mg/dm 3 and strontium up to 0.5 mg/dm 3 do not interfere with the determination. Iron more than 1 mg / dm 3 and aluminum are pre-separated with urotropin (clause 9.2).

2 ASSIGNED CHARACTERISTICS OF INDICATORS OF MEASUREMENT ACCURACY

Table 1 - Measurement ranges, values ​​​​of accuracy, reproducibility and repeatability

1 Corresponds to the expanded relative uncertainty with a coverage factor k = 2.

The values ​​of the accuracy index of the methodology are used for:

Registration of measurement results issued by the laboratory;

Evaluation of the activities of laboratories for the quality of testing;

Evaluation of the possibility of using the measurement results in the implementation of the measurement methodology in a particular laboratory.

3 MEASURING INSTRUMENTS, EQUIPMENT, REAGENTS AND MATERIALS

When performing measurements, the following measuring instruments, utensils, materials, reagents and standard samples are used.

3.1 Measuring instruments

Photoelectrocolorimeter or spectrophotometer of any type,

allowing to measure the optical density at l = 540 nm.

Cuvettes with an absorbing layer length of 30 mm.

Laboratory scales of a special or high accuracy class with a division value of not more than 0.1 mg, the maximum weighing limit of not more than 210 g in accordance with GOST R 53228-2008.

Scales technical laboratory in accordance with GOST R 53228-2008.

3.2 Crockery and materials

Measured test tubes P-1-10-0.1 XC according to GOST 1770-74.

Pipettes measured with divisions of 0.1 cm 3.4(5)-2-1(2); 6(7)-1-5(10) according to GOST 29227-91.

Chemical glasses B-1-50 THS according to GOST 25336-82.

Laboratory funnels B-75-110 XC according to GOST 25336-82.

Ashless filters according to TU 6-09-1678-95.

Bottles made of borosilicate glass or polymeric material with ground or screw caps with a capacity of 500 - 1000 cm 3 for sampling and storage of samples and reagents.

Notes.

1 It is allowed to use other measuring instruments, auxiliary equipment, utensils and materials with metrological and technical characteristics not worse than those indicated.

2 Measuring instruments must be verified within the established time limits.

3.3 Reagents and standards

Hydrogen peroxide (30% aqueous solution) according to GOST 10929-76.

Hexamethylenetetramine (urotropine) according to TU 6-09-09-353-74.

Glacial acetic acid according to GOST 61-75.

State standard samples (GSO) of the composition of a solution of barium ions with a mass concentration of 1 mg/cm 3 . The relative error of the certified values ​​of the mass concentration is not more than 1% at P = 0.95.

Notes.

1 All reagents used for analysis must be of analytical grade. or h.h.

2 It is allowed to use reagents manufactured according to other regulatory and technical documentation, including imported ones, with a qualification not lower than analytical grade.

4 MEASUREMENT METHOD

The turbidimetric method for determining the mass concentration of barium ions is based on the low solubility of barium chromate in a neutral medium.

Ba 2+ + K 2 CrO 4 ® BaCrO 4 + 2K +

The optical density of the solution is measured at l = 540 nm in cuvettes with an absorbing layer length of 30 mm. The color intensity is directly proportional to the concentration of barium ions.

5 REQUIREMENTS FOR SAFETY AND ENVIRONMENTAL PROTECTION

When working in the laboratory, the following safety requirements must be observed.

5.1 When performing analyzes, it is necessary to comply with safety requirements when working with chemical reagents in accordance with GOST 12.1.007-76.

5.2 Electrical safety when working with electrical installations is observed in accordance with GOST R 12.1.019-2009.

5.3 The laboratory room must comply with fire safety requirements in accordance with GOST 12.1.004-91 and have fire extinguishing equipment in accordance with GOST 12.4.009-83.

5.4 Performers must be instructed on safety measures in accordance with the instructions supplied with the devices. The organization of training of workers in labor safety is carried out in accordance with GOST 12.0.004-90.

6 OPERATOR QUALIFICATION REQUIREMENTS

Measurements can be performed by an analytical chemist who is proficient in the technique of photometric analysis, who has studied the instruction manual for the spectrophotometer or photocolorimeter, and who complied with the control standards when performing error control procedures.

7 MEASUREMENT CONDITIONS

Measurements are carried out under the following conditions:

Ambient temperature (20 ± 5) °С.

Relative humidity is not more than 80% at a temperature of 25 °C.

Atmospheric pressure (84 - 106) kPa.

AC frequency (50 ± 1) Hz.

Mains voltage (220 ± 22) V.

8 PREPARATION FOR MEASUREMENTS

In preparation for measurements, the following work is carried out: sampling and storage of samples, preparation of the instrument, preparation of auxiliary and calibration solutions, construction of a calibration graph, control of the stability of the calibration characteristic.

8.1 Sampling and storage

8.1.1 Sampling is carried out in accordance with the requirements of GOST R 51592-2000 “Water. General requirements for sampling”, GOST R 51593-2000 “Drinking water. Sampling”, PND F 12.15.1-08 “Guidelines for sampling for wastewater analysis”.

8.1.2 Water sampling and storage bottles are degreased with CMC solution, washed with tap water, nitric acid diluted 1:1, tap water, and then 3-4 times with distilled water.

Water samples are taken in bottles of borosilicate glass or polymeric material, pre-rinsed with sampled water. The volume of the sample to be taken must be at least 100 cm 3 .

8.1.3 If the sample is analyzed within 24 hours, the sample is not preserved. If it is impossible to carry out measurements within the specified time, the sample is preserved by adding 1 cm 3 of concentrated nitric acid or hydrochloric acid (pH of the sample is less than 2) per 100 cm 3 of the sample. Shelf life 1 month.

The water sample should not be exposed to direct sunlight. For delivery to the laboratory, vessels with samples are packed in a container that ensures preservation and protects against sudden temperature changes.

8.1.4 When sampling, an accompanying document is drawn up in the form, which indicates:

purpose of analysis, suspected contaminants;

place, time of selection;

sample number;

sample volume;

position, name of the person taking the sample, date.

8.2 Preparing the instrument

Preparation of the spectrophotometer and photocolorimeter for operation is carried out in accordance with the operating instructions for the operation of the device.

8.3 Preparation of auxiliary solutions

8 .3 .1 Cooking 3M solution ammonium acetic acid

Placed in a beaker 231 g CH 3 COONH 4 , dissolved in distilled water, transferred to a volumetric flask with a capacity of 1 dm 3 and adjusted to the mark with distilled water. Shelf life 3 months.

8 .3 .2 Cooking solution ammonium (potassium) chromic acid With mass shares 10 %

Placed in a glass of 10 g of ammonium or potassium chromate and dissolved in 90 cm 3 of distilled water. Shelf life 3 months.

8 .3 .3 Cooking solution ammonia With mass shares 10 %

Add 20 cm3 of concentrated (25%) ammonia to a 50 cm3 volumetric flask and dilute to the mark with distilled water. The solution is stored in a polyethylene container. Shelf life 3 months.

8 .3 .4 Cooking solution hydrochloric acids (1:1 )

The solution is obtained by diluting concentrated hydrochloric acid (density 1.19 g/cm 3 ) with distilled water in a ratio of 1:1. The shelf life of the solution is 6 months.

8 .3 .5 Cooking solution peroxides hydrogen With mass shares 10 %

16.7 cm 3 of 30% hydrogen peroxide are placed in a volumetric flask with a capacity of 50 cm 3 and brought to the mark with distilled water. Shelf life 3 months.

8 .3 .6 Cooking solution hexamethylenetetramine (urotropin) With mass shares 10 %

Placed in a glass of 10 g of hexamethylenetetramine, dissolved in 90 cm 3 of water.

8.4 Preparation of calibration solutions

8 .4 .1 Cooking main calibration solution With mass concentration ions barium 1 mg / cm 3

As the main calibration solution with a mass concentration of 1 mg/cm 3 GSO of barium composition is used or a calibration solution is prepared from salt.

A portion of 1.7789 g of 2-aqueous barium chloride is transferred into a volumetric flask with a capacity of 1 dm 3 and brought to the mark with distilled water. 1 cm 3 of the solution contains 1 mg of barium ions.

8 .4 .2 Cooking working calibration solution With mass concentration ions barium 0 ,01 mg / cm 3

In a volumetric flask with a capacity of 1 dm 3 place 10 cm 3 of the main standard solution and bring to the mark with distilled water. 1 cm 3 of the solution contains 0.01 mg of barium.

The solution is used freshly prepared.

8.5 Building a calibration curve

To build a calibration graph, it is necessary to prepare samples for calibration with a mass concentration of barium ions from 1.0 to 6.0 mg/dm 3 .

The conditions of analysis must comply with clause 7.

The composition and number of samples for calibration are given in Table 2. The error due to the procedure for preparing samples for calibration does not exceed 2.5%.

Table 2 - Composition and number of samples for calibration

Samples for calibration are introduced into volumetric test tubes with a capacity of 10 cm 3, brought to the mark with distilled water, and the reagents according to clause 9.3 are added. As a blank sample, distilled water is used, which is carried out through the entire course of the analysis.

Samples for calibration are analyzed in ascending order of their concentration. To build a calibration graph, each artificial mixture must be photometered 3 times in order to eliminate random results and average the data. From the optical density of each calibration solution, subtract the optical density of a blank sample.

When constructing a calibration graph, the optical density values ​​are plotted along the ordinate axis, and the barium content in mg / dm 3 is plotted along the abscissa axis.

8.6 Checking the stability of the calibration characteristic

The stability control of the calibration characteristic is carried out at least once a quarter, as well as after repair or calibration of the instrument, when using a new batch of reagents. The means of control are newly prepared samples for calibration (at least 3 samples from those given in Table 2).

The calibration characteristic is considered stable if the following condition is met for each sample for calibration:

where X- the result of the control measurement of the mass concentration of barium ions in the calibration sample, mg/dm 3 ;

FROM- certified value of the mass concentration of barium ions in the calibration sample, mg/dm 3 ;

The standard deviation of within-laboratory precision, as determined by the implementation of the method in the laboratory.

Note. It is permissible to establish the standard deviation of the intralaboratory precision when implementing the methodology in the laboratory based on the expression: = 0.84s R, with subsequent refinement as information accumulates in the process of monitoring the stability of the analysis results.

s values R are shown in table 1.

If the stability condition for the calibration characteristic is not met for only one calibration sample, it is necessary to re-measure this sample in order to exclude a result containing a gross error.

If the calibration characteristic is unstable, find out the reasons for the instability of the calibration characteristic and repeat the control of its stability using other calibration samples provided for by the procedure. When the instability of the calibration characteristic is detected again, a new calibration curve is built.

9 MEASUREMENTS

9.1. concentration

Concentration is carried out if the expected mass concentration of barium in the sample is less than 1 mg/dm 3 .

100 cm 3 of the sample is added to a heat-resistant beaker, 2 drops of hydrochloric acid (clause 8.3.4) (1:1) are added, then the sample is evaporated on a water bath or on an electric stove (using a heat dissipator) to a volume slightly less than 10 cm 3. After the sample has cooled to room temperature, it is neutralized with 2 drops of concentrated aqueous ammonia, then the sample is transferred into a measuring tube, rinsing the beaker with distilled water, and the sample volume is adjusted to 10 cm3. Then proceed according to clause 9.2 in the presence of interfering influences. In the absence of interfering influences, measurements are started (clause 9.3).

9.2 Elimination of interfering influences

The definition is hindered by iron in concentrations of more than 1 mg / dm 3 and aluminum. In their presence, pre-treatment of the sample is carried out. To do this, 10 cm 3 of the test water is added to a heat-resistant glass with a capacity of 50 cm 3, an ammonia solution is added dropwise (according to clause 8.3.3) until hydroxides precipitate, which are then dissolved with a few drops of hydrochloric acid (according to clause 8.3.4).

If iron (II) is present in the sample, then add a few drops of hydrogen peroxide (according to clause 8.3.5) to oxidize it.

Then pour 5 - 10 cm 3 of a solution of hexamethylenetetramine (according to clause 8.3.6). The contents are boiled and evaporated to a volume slightly less than 10 cm 3 , filtered into a measuring tube and washed with distilled water and adjusted to the mark of 10 cm 3 . Next, proceed to the measurement (clause 9.3).

9.3 Conducting an analysis

10 cm 3 of the test water (or a concentrated sample of the test water), 2 drops of glacial acetic acid, 1 cm 3 of an ammonium acetate solution (according to clause 8.3.1), 5 cm 3 of a potassium or ammonium chromate solution (according to clause 1) are added to a measuring tube. 8.3.2). Shake the contents of the tube after adding each reagent. After 30 minutes, the optical density of the solution is measured at a wavelength of 540 nm in a cuvette with an absorbing layer thickness of 30 mm against the background of distilled water. The absorbance of a blank sample is subtracted from the absorbance of the sample.

In the case of colored or turbid samples, the optical density of the test water, measured with respect to distilled water, is also subtracted from the optical density of the sample obtained during the analysis.

10 PROCESSING THE RESULTS OF MEASUREMENTS

10.1 The mass concentration of barium ions X (mg / dm 3) is calculated by the formula:

FROM- the concentration of barium ions, found on the calibration curve, mg/DM 3 ;

10 - volume to which the sample is diluted, cm3;

V- the volume of the sample taken for analysis, cm 3 .

In the event that dilution or concentration of the sample was carried out, the calculation takes into account the dilution or concentration factor.

10.2 If necessary, the arithmetic mean value ( X cf) of two parallel definitions X 1 and X 2

for which the following condition is satisfied:

|X 1 - X 2 | £0.01× r× X wed (4)

where r- repeatability limit, the values ​​of which are given in table 3.

If condition (4) is not met, methods for checking the acceptability of the results of parallel determinations and establishing the final result in accordance with section 5 of GOST R ISO 5725-6 can be used.

10.3 The discrepancy between the results of the analysis obtained in the two laboratories should not exceed the limit of reproducibility. If this condition is met, both results of the analysis are acceptable, and their arithmetic mean value can be used as the final one. The reproducibility limit values ​​are shown in Table 3.

If the reproducibility limit is exceeded, methods for assessing the acceptability of the analysis results can be used in accordance with section 5 of GOST R ISO 5725-6.

Table 3 - Measurement ranges, values ​​of repeatability and reproducibility limits at probability P = 0.95

11 PRESENTATION OF MEASUREMENT RESULTS

Measurement result X(mg / dm 3) in documents providing for its use, can be represented as: X ± D, P = 0.95,

where D is an indicator of the accuracy of the technique.

The D value is calculated by the formula: D = 0.01×d× X. The value of d is given in table 1.

It is acceptable to present the result of measurements in the documents issued by the laboratory in the form: X ± D l, P \u003d 0.95, subject to D l< D, где

X- the measurement result obtained in strict accordance with the prescription of the methodology;

± D l - the value of the characteristic of the error of the measurement results, established during the implementation of the methodology in the laboratory and provided by stability control.

12 CONTROL OF THE ACCURACY OF MEASUREMENT RESULTS

12.1 General

Quality control of measurement results when implementing the methodology in the laboratory provides for:

Operational control of the measurement procedure;

Monitoring the stability of measurement results based on the control of the stability of the standard deviation (RMS) of repeatability, RMS of intermediate (intralaboratory) precision and correctness.

The frequency of control by the executor of the procedure for performing measurements and the algorithms of control procedures (using the method of additions, using samples for control, etc.), as well as the ongoing procedures for monitoring the stability of the measurement results, are regulated in the internal documents of the laboratory.

The resolution of conflicts between the results of the two laboratories is carried out in accordance with 5.33 GOST R ISO 5725-6-2002.

12.2 Operational control of the measurement procedure using the addition method

To to with control standard To.

K k is calculated by the formula:

To k = | X¢ cf - X wed - FROM q |, (5)

where X¢ cf - the result of measurements of the mass concentration of barium in a sample with a known additive - the arithmetic mean of two results of parallel determinations, the discrepancy between which satisfies condition (4);

X cp - the result of the analysis of the mass concentration of barium in the original sample - the arithmetic mean of two results of parallel determinations, the discrepancy between which satisfies condition (4);

FROM d is the amount of the additive.

Control standard To calculated according to the formula

where D l, X ¢ , D l, X are the values ​​of the error characteristic of the analysis results, established in the laboratory when implementing the method, corresponding to the mass concentration of barium in the sample with a known additive and in the original sample, respectively.

Note.

The measurement procedure is recognized as satisfactory if the following condition is met:

To to < К (7)

If condition (7) is not met, the control procedure is repeated. In case of repeated non-fulfillment of condition (7), the reasons leading to unsatisfactory results are found out and measures are taken to eliminate them.

12.3 Online control of the measurement procedure using control samples

Operational control of the measurement procedure is carried out by comparing the result of a single control procedure To to with control standard To.

The result of the control procedure To k is calculated by the formula:

To k = | FROM Wed - FROM|, (8)

where FROM cf - the result of the analysis of the mass concentration of barium in the sample for control - the arithmetic mean of two results of parallel determinations, the discrepancy between which satisfies condition (4);

FROM- certified value of the control sample.

Control standard To calculated according to the formula

To = FROM´d l ´0.01 (9)

where ±d l - characteristic of the error of the analysis results, corresponding to the certified value of the control sample.

The values ​​of d l are given in table 1.

Note.

It is permissible to establish the error characteristic of the measurement results when implementing the methodology in the laboratory on the basis of the expression: D l \u003d 0.84 × D, with subsequent refinement as information accumulates in the process of monitoring the stability of the measurement results.

The analysis procedure is considered satisfactory if the following condition is met:

To to £ To(10)

If condition (10) is not met, the control procedure is repeated. If condition (10) is not met again, the reasons leading to unsatisfactory results are found out and measures are taken to eliminate them.

Description

Barium is an alkaline earth metal. Barium compounds are widely used in the oil, electronics, and paper industries. This element is a silver-white metal with a density of 3.78 g/cu. see. In nature, barium does not occur in its pure form. The most common compounds are barium sulfate and barium carbonate. Barium enters the water from natural sources, only a small proportion can be attributed to human activities. A large concentration of the metal is found in areas where such minerals as witherite and barite occur. The content of barium in water can range from 1 to 20 mg/l, while the permissible concentration of the substance in drinking water according to the standards of the World Health Organization should not exceed 0.7 mg/l, in Russia this figure is at around 0.1 mg/l . Therefore, questions about the content of barium in drinking water and water purification from this element are important. The impact of metal on human health is high. Drinking water with a high content of this substance can lead to increased blood pressure, muscle weakness, and pain in the abdominal cavity. Therefore, the purification of water from this element is so important.

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The owners of the patent RU 2524230:

The field of technology to which the invention belongs

The present invention relates to methods for reducing the concentration of barium in water.

State of the art

Barium often ends up in wastewater during industrial production. The presence of barium in industrial wastewater tends to make it toxic, so it must be removed from the wastewater to ensure proper disposal. If barium is not removed from wastewater prior to disposal, barium can seep into groundwater and soil. Groundwater in the US Midwest contains soluble barium. Barium exposure can cause, among other things, gastrointestinal disturbances, muscle weakness, and increased blood pressure.

It is well known that deposits form on the membrane during water treatment due to the presence of barium. To protect the membrane from the formation of deposits, it is necessary to pretreat, before supplying water to the membrane device, in order to remove barium. Several methods have been developed to reduce the concentration of barium in groundwater and wastewater.

One way to reduce the concentration of barium is the chemical precipitation of barium carbonate by liming the water. However, the precipitation and removal of barium by liming is highly dependent on pH. For precipitation to be effective, the water must have a pH between 10.0 and 10.5. Another way to reduce the concentration of barium is the chemical precipitation of barium sulfate using coagulants such as aluminum or iron sulfate. However, because the barium sulfate precipitation reaction is slow, a two-stage precipitator is needed to remove barium by conventional coagulation.

Another way to reduce the concentration of barium in water involves the use of ion exchange devices. However, ion exchange devices require frequent regeneration of the resin with additional chemicals. Such processing, manipulation and removal of regenerating chemicals is the main disadvantage of this method. To reduce the concentration of barium in water, reverse osmosis (reverse osmosis - RO) installations are also used. However, in RO installations, deposits often form on the RO membrane if barium reacts with other contaminants present in the water to form barium sulfate or barium carbonate. This reduces the efficiency of the RO unit and may damage the membrane. Finally, a method is used to remove barium from water, including the adsorption of barium on magnesium hydroxide. However, this process is also highly dependent on pH. For the adsorption and removal of barium to be effective, the water must have a pH of approximately 11.

All of the methods mentioned above involve several process steps and are complex or expensive. Therefore, there is a need for a simple and cost-effective way to remove barium from water.

The essence of the invention

A method for removing barium from water is disclosed. This method includes forming aqueous manganese oxide and mixing aqueous manganese oxide with water containing barium, wherein the surface of aqueous manganese oxide is negatively charged at a pH of more than 5.0. The negatively charged hydrous manganese oxide comes into contact with water containing barium, and the barium is adsorbed onto the hydrous manganese oxide. Then, the aqueous manganese oxide with adsorbed barium is separated from the water and a treated effluent is obtained.

In one embodiment, the hydrous manganese oxide with adsorbed barium is separated from the water by conventional flocculation and separation methods. In yet another embodiment of the invention, aqueous manganese oxide with adsorbed barium is separated from water by ballast-loaded flocculation and separation.

In yet another embodiment of the invention, this method includes the formation of a solution of aqueous manganese oxide and the supply of this solution in a reactor with a fixed bed of an inert medium. The hydrous manganese oxide solution fed into the fixed bed reactor forms a coating on the surface of the inert medium. Then water containing barium is directed onto the coated inert medium. As the water passes the coated inert medium, the barium from the water is adsorbed onto hydrous manganese oxide on the surface of the inert medium.

In addition, during the removal of soluble barium by adsorption on aqueous manganese oxide, soluble iron and manganese are also removed from water.

Other objects and advantages of the present invention will become apparent and apparent upon consideration of the following description and the accompanying drawings, which merely illustrate the invention.

Brief description of the drawings

On FIG. 1 is a line graph of the adsorption capacity of HMO (hydrous manganese oxide) versus barium cation concentration in water.

On FIG. 2 is a line graph showing the effect of pH on the adsorption capacity of HMO (hydrous manganese oxide) to barium cations in water.

On FIG. 3 is a line graph illustrating the rate of removal of barium from water with HMO.

On FIG. 4 shows a line graph of the adsorption capacity of NMO solutions of various concentrations with respect to barium cations in the presence of competing cations.

On FIG. 5 is a line plot of the adsorption capacity of HMOs to barium cations in water in the absence of competing cations.

On FIG. 6 is a line plot of the adsorption capacity of HMOs for high concentration barium cations in the presence of competing cations.

On FIG. 7 is a diagram of a plant and method for removing barium from water using a mixed bed flocculation plant.

On FIG. 8 is a diagram of a plant and method for removing barium from water using a mixed bed flocculation plant with a ballast load.

On FIG. 9 is a diagram of the plant and method for removing barium from water using a fixed bed plant.

Description of exemplary embodiments of the invention

The present invention relates to an adsorption process for removing dissolved barium from water. To reduce the concentration of barium in water, contaminated water is mixed with a solution of aqueous manganese oxide (hydrous manganese oxide - HMO). The HMO is amorphous in nature and has a highly reactive surface. When water containing barium is mixed with an HMO solution, the dissolved barium is adsorbed onto the reactive surface of the HMO. Then, HMO and adsorbed barium are separated from water and a treated effluent stream with a reduced concentration of barium is obtained.

The isoelectric point of HMO, that is, the point of zero charge (pH pzc), lies between 4.8 and 5.0. The point of zero charge corresponds to the pH of the solution at which the total surface charge of the HMO is zero. Thus, when an HMO is immersed in a solution with a pH of about 4.8 to about 5.0, the surface of the HMO has zero net charge. However, if the pH of the solution is less than about 4.8, there are more protons in the acidic water than there are hydroxyl groups, so the surface of the HMO becomes positively charged. Similarly, when the pH of the solution is greater than about 5.0, the surface of the HMO acquires a negative charge and attracts positively charged cations.

Typical pH of raw groundwater and industrial wastewater is in the range of about 6.5 to about 8.5. Therefore, when untreated barium-containing water comes into contact with an HMO in solution, the surface of the HMO becomes negatively charged and attracts positively charged barium ions, Ba 2+ . The method described herein typically reduces the concentration of barium in water or wastewater to about 50 ppb, and under some circumstances can reduce the concentration of barium to about 20 ppb or less.

During the tests, an HMO solution with a pH of 4.0 was prepared and stirred slowly overnight. Then, various doses of the HMO solution were mixed with water, the barium concentration of which was 1.00 mg/l. No other cations were present in the water. Each dose of HMO was mixed with water for 4 hours. The pH of each reaction mixture ranged from 7.5 to 8.0. The line chart shown in Fig. 1 reflects the adsorption capacity of HMOs with respect to barium cations in water. As shown in the graph, the preferred concentration of the HMO solution is from about 5 to 10 mg/L, with an initial barium concentration in the raw water of about 1 mg/L.

Various pH conditions were also tested to determine the effect of pH on the adsorption capacity of HMOs. An HMO solution was prepared at pH 4.0 and stirred slowly overnight. Then, a solution of HMO with a concentration of 10 mg/l was added to water with a concentration of barium of 1.0 mg/l. No other cations were present in the water. The HMO solution was mixed with water for 4 hours under various pH conditions. The line chart shown in Fig. 2 reflects the optimal pH conditions in terms of the adsorption capacity of HMOs for barium cations in water. As shown in FIG. 2, a pH of about or greater than 5.5 is preferred.

The optimal kinetics of the barium adsorption reaction on NMO was also studied. The HMO solution was mixed with water containing about 1 mg/l of barium. As seen in the line graph shown in Fig. 3, the absorption rate of barium HMO is very high. The adsorption capacity of HMO with respect to barium in the presence of other, competing cations is shown in Fig.4.

The tests described above were carried out with water containing only barium cations. Therefore, an additional test was carried out to determine the effect of the presence of iron cations, Fe 2+ , on the adsorption capacity of HMO towards barium cations. Fe 2+ was aerated in solution at pH 7.5 for 30 minutes. A 1.00 mg/l Ba 2+ solution and a 10 mg/l HMO solution were added to the Fe 2+ solution. The mixture was stirred for 10 minutes, then filtered with a 0.45 µm filter. The concentration of barium in the treated water decreased to 15 µg/L.

In addition, tests were carried out to determine the effect of conjugated oxidation of iron on the adsorption capacity of HMO in relation to barium ions. Fe 2+ and Ba 2+ are mixed together in solution. The Ba 2+ concentration was 1.00 m/L. Then a solution of HMO with a concentration of 10 mg/l was added. The mixture was aerated for 30 minutes at a pH of 7.5. The mixture was then filtered on a 0.45 µm filter. The concentration of barium in the treated water decreased to 90 µg/l.

The barium adsorption process was also tested in the presence of various competing cations. In this example, various doses of HMO were mixed with water containing several different cations for 10 minutes at a pH of 7.5. The contaminants present in the raw water are listed in Table 1 below.

The line graph shown in FIG. 4 illustrates the adsorption capacity of an HMO solution of various concentrations with respect to barium cations in the presence of competing cations.

In the examples described above, when the concentration of the HMO solution was 40 mg/l, the concentration of cations in the treated water decreased even more, as shown in Table 2.

The method for adsorbing barium onto HMOs was also tested on water containing high concentrations of barium and free of competing cations. HMO was mixed with water, the concentration of barium in which was 15 mg/l. The mixture was stirred for 10 minutes at pH 7.5 to 8.0. Various concentrations of HMO were used. The line graph shown in FIG. 5 depicts the adsorption capacity of HMOs for barium cations in the absence of competing cations. As shown in the graph, one of the preferred HMO solution concentrations is approximately 100 mg/L for a barium concentration in raw water of approximately 15 mg/L.

The barium adsorption method was also tested on water containing high concentrations of barium in the presence of competing cations. HMO was mixed with water, the concentration of barium in which was 15 mg/l. The mixture was stirred for 10 minutes at pH 7.5 to 8.0. Various concentrations of HMO were used. The contaminants present in the wastewater stream are listed in Table 3 below.

The line graph shown in FIG. 6 illustrates the adsorption capacity of HMOs for high concentration barium cations in the presence of competing cations.

The barium adsorption method was also tested on high concentration barium water in the presence of competing cations using a 90 mg/L HMO solution. HMO was mixed with water, the concentration of barium in which was 15 mg/l. The mixture was stirred for 10 minutes at pH 7.5 to 8.0. The contaminants present in the wastewater stream and their concentrations in the effluent are shown in Table 4.

A method for removing barium and a plant 1 capable of effectively reducing the concentration of barium in water are explained in FIG. The HMO solution is formed in the HMO reactor 10. Table 5 describes several methods for preparing HMO.

In the embodiment illustrated in FIG. 7, HMO is produced by mixing a solution of potassium permanganate (KMnO 4 ) and a solution of manganese sulfate (MnSO 4 ) in downcomer 12. In one example, 42.08 g KMnO 4 is fed into reactor 10 via line 14, 61.52 g MnSO 4 is fed into reactor 10 via line 16. These reactants are mixed in reactor 10 to form an HMO solution. During this reaction, the optimum pH for HMO formation is from about 4.0 to about 4.5. After HMO formation, NaOH is fed into reactor 10 via line 18 to adjust the pH of the HMO solution to approximately 8.0.

After the initial HMO solution is prepared, some HMO solution is fed from the HMO production reactor 10 to the barium removal reactor 20 through line 28. The dose of the HMO solution entering the barium removal reactor 20 can be controlled using a pump 24. Water containing barium is fed into barium removal reactor 20 via line 26 and mixed with the HMO solution.

In this embodiment, the barium removal reactor 20 has a downcomer 22 for mixing the HMO solution and barium-containing water. As the HMO solution is mixed with water containing barium, the negatively charged surface of the HMO attracts positively charged barium ions, which are adsorbed on the surface of the HMO. Although the reaction time may vary, the preferred reaction time in the barium removal reactor 20 is approximately 10 minutes.

To intensify settling and separation, a mixture of water and HMO with adsorbed barium is sent to a flocculation tank 30 where it is mixed with a flocculant to cause floc formation. The flocculant is added via line 34. In this embodiment, the flocculation tank 30 also has a downcomer 32 for mixing the adsorbed barium HMO with the flocculant. One example of a flocculant is a polymeric flocculant.

In some embodiments of the invention, flocculation may not be required. However, in some cases mixing HMO with adsorbed barium with a flocculant is advantageous because the flocculant causes the HMO with adsorbed barium to accumulate around the flocculant and form flocculation. This intensifies the settling and separation of HMO with adsorbed barium and water.

The treated water containing the flocs flows out of the flocculation tank 30 and enters a solids/liquid separator such as a sump 36. the stream is sent through line 44 for additional processing in relation to other contaminants, if necessary. For example, in one embodiment of the invention, the treated effluent is sent via line 44 to an RO 40 unit for further clarification. The filtrate from the RO 40 unit is withdrawn through filtrate line 46, the waste stream is withdrawn through line 48. Although Figure 7 shows a settler 36 that has collection chutes or thin plates 38, those skilled in the art will appreciate that in some settlers such elements may not be required.

As the flakes settle, they settle to the bottom of the sump 36, where sludge is formed. The slurry is sent by pump 42 to line 50, from where at least a portion of the HMO-containing slurry can be fed to barium removal reactor 20 via line 54 and reused in the plant. The recycled HMO is involved in the additional adsorption of barium from the wastewater stream due to the involvement of unused adsorption centers of the reactive HMO. The remaining sludge may be discharged directly through line 52 or may first be thickened and dehydrated before being disposed of as waste.

In some embodiments of the invention, ballast-loaded flocculation units may be used instead of a conventional clarification device. A ballast-loaded flocculation plant uses microsand or other ballast to form flocculation. Additional details for understanding ballasted flocculation processes can be found in US Pat. Nos. 4,927,543 and 5,730,864, the disclosure of which is expressly incorporated herein by reference.

8 illustrates a plant 100 and a method for removing barium from water using a ballast-loaded flocculation plant. In this embodiment, HMO is produced in reactor 110, which has a downcomer 112. In this embodiment, KMnO 4 is added to HMO reactor 110 via line 114, MnSO 4 is added to reactor 110 via line 116. In addition, NaOH is added to the HMO solution in reactor 110 via line 118 to adjust the pH of the HMO.

After the HMO stock solution is prepared, some HMO solution is fed from the HMO production reactor 110 to the barium removal reactor 120 via line 128. The doses of the HMO solution entering the barium removal reactor 20 can be controlled using a pump 124. Barium-containing water is fed into barium removal reactor 120 via line 126 and mixed with the HMO solution. In this embodiment, the barium removal reactor 120 has a downcomer 122 for mixing the HMO solution and barium-containing water. As the HMO solution is mixed with water containing barium, the negatively charged surface of the HMO attracts positively charged barium ions, which are adsorbed on the surface of the HMO. Although the reaction time may vary, the preferred reaction time in the barium removal reactor 120 is approximately 10 minutes.

Thereafter, the mixture of water and HMO with adsorbed barium is sent to a flocculation tank 130 with a ballast load, where it is mixed with ballast, such as microsand, and with a flocculant in pipe 132. The flocculant is added through line 134, the ballast is fed through line 158. HMO with adsorbed barium collects and accumulates around the ballast, forming flakes.

The treated flake-containing water flows out of the flocculation tank 130 and enters a solids/liquid separator such as a sump 136. the stream is sent for additional processing in relation to other contaminants, if necessary. For example, in one of the embodiments of the invention, the treated effluent is sent to the RO 140 unit for additional clarification. The filtrate from the RO unit 140 is withdrawn through the filtrate line 146, the waste stream is withdrawn through the line 148. Although in FIG. 8 shows a sump 136 that includes collection chutes or traps 138, those skilled in the art will appreciate that some sumps may not require such features.

As the flakes settle, they settle to the bottom of the sump 136, where sludge is formed. The sludge is removed by pump 142, at least part of the sludge can be sent to a separator 156, such as a hydrocyclone. During hydrocyclone separation, the lower density sludge containing HMO with adsorbed barium is separated from the higher density sludge containing ballast. At least a portion of the ballast may be sent to the flocculation tank 130 and reused in this process. Recycled ballast stimulates additional flocculation of HMO with adsorbed barium. The lower density slurry containing HMO with adsorbed barium is withdrawn at the top of the hydrocyclone, a portion of the lower density slurry may be sent to the barium removal reactor 120 via line 154 and reused in the process. The recycled HMO participates in the additional adsorption of barium from the wastewater stream. A portion of the higher density slurry containing ballast may be withdrawn from hydrocyclone 156 and sent to flocculation tank 130 via line 158. The remaining slurry may be discharged directly via line 152 or may first be thickened and dehydrated before being disposed of as waste.

Another embodiment of the invention is illustrated in Fig.9. In this embodiment, the barium is removed from the waste stream in a fixed bed unit 200. In this embodiment, KMnO 4 is added to HMO reactor 210 via line 214, MnSO 4 is added to reactor 210 via line 216. In addition, NaOH is added to the HMO solution in reactor 210 via line 218 to adjust the pH of the HMO. The HMO solution is prepared in the reactor 210 using the downcomer 212. The HMO solution is fed into a fixed bed packed column 220 filled with an inert medium such as sand or carbon. The HMO solution forms a coating on the surface of the inert medium before barium-containing water is fed into the column. The HMO solution can be fed to column 220 via line 224. Excess HMO is withdrawn from column 220 via line 230. Barium-containing water can be fed to column 220 via line 222 at a predetermined hydraulic load in either downflow or upflow mode. .

As the water containing barium comes into contact with the HMO of the inert medium coating, the negatively charged surface of the HMO attracts the positively charged barium ions contained in the water, which are adsorbed on the surface of the HMO. Depending on the column configuration, downflow or upflow, the treated barium reduced effluent is taken at the bottom or top of the column, respectively. The treated effluent is withdrawn from column 220 via line 232, if desired, it can be sent for additional processing in relation to other contaminants. For example, in one embodiment, the treated effluent is sent via line 232 to RO 234 for further clarification. The filtrate from the unit is withdrawn via filtrate line 236, the waste stream is withdrawn via line 238. HMO with adsorbed barium can be removed from the column by backwashing. The backwash fluid is supplied to tower 220 via line 226. The backwash sludge may be removed via line 228 and collected in a sludge storage tank for disposal.

A fixed bed plant, such as the one described above, has the advantage that it can be used as an additional plant site without changing the existing wastewater treatment plant.

In the context of this document, the term "water" refers to any water stream containing barium, including water, wastewater, groundwater and industrial wastewater. As used herein, the term "HMO" refers to all types of hydrous manganese oxides, including hydrous manganese(III) oxide and hydrous manganese(II) oxide. However, hydrous manganese(IV) oxide has a higher adsorption capacity than other hydrous manganese oxides, so hydrous manganese(IV) oxide is preferable for adsorbing barium.

Of course, the present invention may be practiced in other ways than those specifically described herein without departing from the essential features of the present invention. The present embodiments of the invention are to be considered in all respects as illustrative and not restrictive, all changes within the meaning and series of equivalents of this claim are included in the scope of the present invention.

1. A method for removing barium from water, including:
formation of hydrous manganese oxide;
mixing aqueous manganese oxide with barium-containing water so that aqueous manganese oxide is negatively charged at a pH greater than 4.8;
adsorption of barium from water on negatively charged aqueous manganese oxide;
mixing the flocculant with water and aqueous manganese oxide with adsorbed barium;
the formation of sludge, where the sludge contains flakes with hydrous manganese oxide with adsorbed barium; and
separating the aqueous manganese oxide flakes with adsorbed barium from the water and obtaining a treated effluent stream.

2. The method according to claim 1, further comprising obtaining aqueous manganese oxide by one of the following methods:
oxidation of ferrous manganese ion with permanganate ion, oxidation of ferrous manganese ion with chlorine or oxidation of ferrous ion with permanganate ion.

3. The method of claim 2, further comprising:
obtaining aqueous manganese oxide by mixing manganese (II) sulfate with potassium permanganate;
supply of aqueous manganese oxide to the reactor;
mixing aqueous manganese oxide with water containing barium.

4. The method of claim 3, further comprising:
directing manganese(II) sulfate and potassium permanganate to the downcomer, the downcomer having an agitator;
introduction of a downward flow of manganese (II) sulfate and potassium permanganate through a pipe with a downward flow; and
mixing manganese (II) sulfate and potassium permanganate using a stirrer located in a pipe with a downward flow.

5. The method of claim 1, further comprising:
recycling at least part of the sludge; and
mixing a portion of the recycled sludge with hydrous manganese oxide and water containing barium.

6. The method of claim 1, including feeding the treated effluent to a reverse osmosis unit and receiving a filtrate stream and a return stream.

7. The method according to claim 1, including the separation of aqueous manganese oxide with adsorbed barium from water by flocculation with a ballast load.

8. The method of claim 7, wherein the ballast-loaded flocculation comprises:
mixing the flocculant, ballast and aqueous manganese oxide with adsorbed barium to form ballast loaded flakes;
sedimentation of flakes with ballast load to obtain sludge;
supply of sludge to the separator and separation of ballast from sludge; and
ballast recycling to the flocculation plant with ballast load.

9. The method of claim 8, wherein the sludge production comprises:
obtaining a sludge with a lower density and a sludge with a higher density, where the sludge with a lower density contains aqueous manganese oxide with adsorbed barium, and the sludge with a higher density contains ballast; and
separating at least a portion of the lower density sludge from the higher density sludge.

10. The method of claim 9, further comprising:
recycling at least a portion of the lower density sludge containing hydrous manganese oxide with adsorbed barium; and
mixing at least a portion of the lower density recycled sludge with hydrous manganese oxide and barium-containing water.

11. The method of claim 1, further comprising:
formation on an inert material in an installation with a fixed layer of a coating of hydrous manganese oxide;
supplying barium-containing water to the fixed bed plant;
adsorption of barium from water by hydrous manganese oxide coating an inert material; and
receiving a processed effluent stream.

12. The method of claim 1, further comprising treating barium-containing water with hydrous manganese oxide such that the treated effluent has a barium concentration of about 50 ppb or less.

13. The method of claim 12 further comprising treating barium-containing water with hydrous manganese oxide such that the treated effluent stream has a barium concentration of about 20 ppb or less.

14. The method of claim 1 wherein the barium-containing water has a pH of 5.0 to 10.0.

15. The method of claim 1, wherein the concentration of aqueous manganese oxide is approximately 5 to 10 mg/L for every 1 mg/L of barium in the raw water.

16. A method for removing barium from water, including:
obtaining a solution of aqueous manganese oxide in the first tank;

mixing water containing barium with an aqueous manganese oxide solution in a barium removal reactor to form an aqueous manganese oxide solution/water mixture in the barium removal reactor, wherein the pH of the aqueous manganese oxide solution/water mixture is approximately 4.8 or more and causes a negative charge to form on the surface aqueous manganese oxide;
adsorbing barium from water on a negatively charged surface of aqueous manganese oxide in a solution of aqueous manganese oxide/water;

mixing the flocculant with an aqueous manganese oxide solution/water mixture containing adsorbed barium;
floc formation in the hydrous manganese oxide/water mixture, where the flocs contain hydrous manganese oxide with adsorbed barium and the flocs form a sludge;
after mixing the flocculant with the aqueous manganese oxide solution/water mixture, feeding the aqueous manganese oxide solution/water mixture containing flakes into a sump;
settling the sludge in the sump and receiving a treated effluent; and
removal of sludge from the sump.

17. The method according to claim 16, including:
separation from the sludge, at least part of the aqueous manganese oxide with adsorbed barium; and
recycling the separated hydrous manganese oxide with adsorbed barium by mixing the hydrous manganese oxide solution and water containing barium with the separated hydrous manganese oxide with adsorbed barium.

18. The method of claim 16 further comprising forming an aqueous manganese oxide solution having a pH of about 4.0.

19. The method of claim 18, further comprising mixing hydrous manganese oxide with barium-containing water such that the pH of the mixture is about 5.5 or greater.

20. The method of claim 16 further comprising removing iron and manganese from the water by adsorbing the iron and manganese from the water onto a negatively charged hydrous manganese oxide surface.

21. A method for removing barium from water, including:
forming a solution of aqueous manganese oxide in the first tank;
feeding the hydrous manganese oxide solution to the barium removal reactor;
mixing water containing barium with an aqueous manganese oxide solution in a barium removal reactor to form an aqueous manganese oxide solution/water mixture, where the pH of the aqueous manganese oxide solution/water mixture is approximately 4.8 or more and results in a negative charge growth on the surface of the aqueous manganese oxide ;
adsorption of barium from water on the negatively charged surface of aqueous manganese oxide;
supplying the aqueous manganese oxide solution/water mixture to the flocculation tank;
mixing the flocculant and ballast with a mixture of hydrous manganese oxide/water;
the formation of flakes, where the flakes contain ballast and manganese oxide with adsorbed barium;
after mixing the flocculant and ballast with the aqueous manganese oxide solution/water mixture, feeding the aqueous manganese oxide solution/water mixture to the sump;
settling the flakes in a sump to form sludge and treated effluent;
feeding the sludge from the sump to the separator and separating at least a portion of the ballast from the sludge; and
recycling the separated ballast; and mixing the separated ballast with the aqueous manganese oxide solution/water mixture.

22. The method according to claim 21, including:
separation from the sludge, at least part of the manganese oxide with adsorbed barium;
recycling the separated manganese oxide with adsorbed barium; and
mixing the separated manganese oxide with the adsorbed barium and a mixture of aqueous manganese oxide/water.

23. The method of claim 22, including feeding the treated effluent to a reverse osmosis unit and filtering the treated effluent to form a filtrate stream and a return stream.

24. The method of claim 21, wherein the barium removal reactor comprises a downcomer with an agitator located therein, the method comprising:
supplying a solution of hydrous manganese oxide and barium-containing water to the top of the downcomer pipe; and
introducing into this pipe a downward flow of a solution of aqueous manganese oxide and water containing barium;
mixing the hydrous manganese oxide solution and the barium-containing water as the hydrous manganese oxide solution and the barium-containing water move down the downcomer.

25. The method of claim 22, wherein the flocculation tank includes a downcomer containing an agitator, the method comprising using an agitator in the downcomer to mix the flocculant and ballast with the aqueous manganese oxide solution/water mixture.

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In nature, barium occurs only in the form of compounds, and for water, the main route of contamination is natural, from natural sources. As a rule, the content of barium in groundwater is low, but in areas where minerals containing barium occur (barite, witherite), its concentration in water can range from a few to several tens of milligrams per liter. A relatively high barium content is possible only in waters with a low sulfate content.

Barium is a toxic trace element, but is not considered mutagenic or carcinogenic. Water-soluble barium salts are also considered to be dangerous to humans - carbonates, sulfides, chlorides, barium nitrates. Highly soluble toxic barium salts pose the greatest danger in water, but they tend to turn into less toxic and poorly soluble salts (sulfates and carbonates). Barium is not a highly mobile element. It is well sorbed by clay particles, organic colloids, iron and manganese hydroxides, which reduces its mobility in water.

The daily requirement of the human body for barium has not been established, the average daily intake is in the range of 0.3-1 mg. The human body, whose body weight is about 70 kg, contains approximately 20-22 mg of barium.

Not included in the number of essential elements (vital for the body), barium is close in its properties to calcium, which is mainly found in bone tissue, so barium ions can replace calcium in the bones. When entering the human body, even at low concentrations, barium has a pronounced effect on smooth muscles. In small concentrations, it relaxes them, but in large concentrations it reduces them, increasing intestinal motility, causing arterial hypertension, muscle fibrillation and impaired cardiac conduction.

In the course of scientific studies conducted under the auspices of WHO, the relationship between mortality from cardiovascular diseases and the content of barium in drinking water has not been confirmed. In short-term studies in volunteers, no adverse effect on the cardiovascular system was found at concentrations of barium in water up to 10 mg/l.

In turn, USEPA information indicates that even a single use of water, the content of barium in which significantly exceeds the maximum allowable values, can lead to muscle weakness and pain in the abdominal region.

However, it must be taken into account that the barium standard established by the USEPA quality standard (2.0 mg/l) significantly exceeds the value recommended by WHO (0.7 mg/l). The hygienic standards adopted in the Republic of Belarus set an even more stringent MPC value for the content of barium in drinking water (0.1 mg/l).

Laboratory doctor of the laboratory of sanitary-chemical and toxicological research methods A.V. Aniskevich

In domestic and foreign literature, there are numerous data indicating a wide range of effects of barium compounds on the human body. In particular, the effect of barium adversely affects the hematopoietic, cardiovascular and nervous systems, the functions of the liver and gastrointestinal tract are disturbed, and vitamin C is destroyed.

Under production conditions, barium compounds enter the body mainly in the form of disintegration aerosols through the respiratory organs and, to a lesser extent, through the gastrointestinal tract or damaged skin.

The toxicity of barium salts largely depends on the degree of their solubility in water and biological media of the body. The most toxic are compounds such as chloride, nitrate, carbon dioxide, sulfur and barium hydroxide, as well as its oxide and peroxide. Insoluble in water, acids and alkalis, barium sulfate does not have toxic properties. Poisoning with barium compounds can be both acute and chronic in severity.

Acute poisoning is possible when highly soluble barium compounds enter through the mouth or in significant concentrations through the respiratory organs. In this case, the gastrointestinal tract is primarily affected (stomach pain, vomiting, diarrhea), the cardiovascular nervous system (high blood pressure, bradycardia, dizziness, gait and vision disorders, convulsions and paralysis). In severe cases, death from heart failure is possible.

Chronic poisoning occurs with prolonged intake of small amounts of barium compounds in the form of aerosols through the respiratory organs. In particular, the long-term intake of ultrafine barium carbonate into the lungs causes a general toxic effect on the body.

The results of a polyclinic examination of barium production workers and data from experimental studies with chronic inhalation exposure of animals to barium carbonate dust showed that chronic barium intoxication is characterized by impaired vascular tone of the hyper- and hypotonic type, myocardial damage with a change in cardiac conduction function and impaired phosphorus-calcium metabolism in the body . At the same time, the hematopoietic system suffers (decrease in hemoglobin, leukocytosis, thrombopenia) and the protein-forming and detoxification function of the liver is disturbed, and the activity of enzymes is also inhibited.

Prolonged intake of insoluble barium sulphate dust into the lungs causes occupational barite pneumoconiosis in workers. Dust of barium carbonate also has a pronounced fibrogenic effect. Most barium compounds are characterized by a local irritant effect on the skin and mucous membranes - the latter is most pronounced in barium hydroxide.

In an animal experiment, it was found that barium has a pronounced ability to accumulate and lingers in the body for a long time. In addition, the barium ion easily crosses the placental barrier and during lactation can be excreted in mother's milk.

The maximum permissible concentration of aerosols of barium compounds in the air of the working area is set - for absolutely insoluble (barium sulfate) at the level of 6 mg / m 3, for soluble in biological media of the body (barium carbonate) at the level of 0.5 mg / m 3.

Biological role and toxicity.

The biological role of barium has not been studied enough. It is not included in the number of vital trace elements.

All water-soluble barium compounds are highly toxic. Due to the good solubility in water from barium salts, chloride is dangerous, as well as nitrate, nitrite, chlorate and perchlorate. Well-soluble barium salts in water are rapidly resorbed in the intestine.

Symptoms of acute poisoning with barium salts: salivation, burning in the mouth and esophagus. Pain in the stomach, colic, nausea, vomiting, diarrhea, high blood pressure, hard irregular pulse, convulsions, later paralysis is possible, cyanosis of the face and extremities (cold extremities), profuse cold sweat, muscle weakness, especially of the extremities, reaching that the poisoned cannot nod his head. Disorder of gait, as well as speech due to paralysis of the muscles of the pharynx and tongue. Shortness of breath, dizziness, tinnitus, blurred vision.

In case of severe poisoning, death occurs suddenly or within one day. Severe poisoning occurs when 0.2-0.5 g of barium salts are ingested, the lethal dose is 0.8-0.9 g.

For first aid, it is necessary to wash the stomach with a 1% solution of sodium or magnesium sulfate. Enemas from 10% solutions of the same salts. Ingestion of a solution of the same salts (20.0 hours of salt per 150.0 hours of water) in a tablespoon every 5 minutes. Emetics to remove the resulting insoluble barium sulfate from the stomach. Intravenously 10-20 ml of 3% sodium sulfate solution. Subcutaneously - camphor, caffeine, lobelin - according to indications. Warm feet. Inside mucous soups and milk.

Appropriate washing facilities and other sanitary facilities should be provided for workers exposed to toxic soluble barium compounds, and strict personal hygiene practices should be established. Smoking, eating and drinking in the workplace must be strictly prohibited. Floors in work areas should be dense and cleaned regularly. Efforts should be made to reduce the concentration of barite dust in the air to a minimum. In addition, special attention should be paid to the presence of silica in airborne dust.