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Method for simultaneous removal of cadmium and thallium in raw water

A technology of raw water and water intake, applied in the direction of chemical instruments and methods, water pollutants, water/sewage multi-stage treatment, etc., to achieve the effect of simple process

Active Publication Date: 2014-04-02
SHENZHEN WATER GRP CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, there is no report on the simultaneous removal of thallium and cadmium pollution in raw water. There are some research reports on the technology of separately removing cadmium and thallium

Method used

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  • Method for simultaneous removal of cadmium and thallium in raw water
  • Method for simultaneous removal of cadmium and thallium in raw water

Examples

Experimental program
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Effect test

Embodiment example 1

[0043] 1) Take 1L of raw water, add sodium hydroxide to adjust the pH value to 8.5;

[0044] 2) Add 0.6mg / L potassium permanganate and react for 5 minutes;

[0045] 3) Add sodium hypochlorite solution, add effective chlorine concentration of 2.0mg / L, and react for 3 minutes:

[0046] 4) Add lime water 25mg / L and react for 1 minute;

[0047] 5) Add 5.0 mg / L polyferric sulfate, react for 20 minutes, precipitate for 20 minutes, and filter.

[0048] When the cadmium content in the raw water before treatment was 25 μg / L and the thallium content was 0.25 μg / L, the cadmium content in the water after precipitation was 2.7 μg / L and the thallium content was 0.05 μg / L, and the removal rate of cadmium during the precipitation process was 89.2% respectively. , 80%; the cadmium content in the filtered water is 0.08μg / L, the thallium content is 0.02μg / L, and the total removal rates are 99.7% and 92% respectively.

Embodiment example 2

[0050] 1) Take 1L of raw water, add sodium hydroxide to adjust the pH to 8.0;

[0051] 2) Add 0.8 mg / L potassium permanganate and react for 5 minutes;

[0052]3) Add sodium hypochlorite solution, the concentration of available chlorine added is 1.5mg / L, and react for 3 minutes;

[0053] 4) Add lime water 30mg / L and react for 1 minute;

[0054] 5) Add 5.0 mg / L polyferric sulfate, react for 20 minutes, precipitate for 20 minutes, and filter.

[0055] When the cadmium content in the raw water before treatment was 20 μg / L and the thallium content was 0.18 μg / L, the cadmium content in the water after precipitation was 1.8 μg / L and the thallium content was 0.04 μg / L, and the removal rates were 91% and 77.8% respectively; The cadmium content in the back water was 0.05 μg / L, the thallium content was 0.02 μg / L, and the total removal rates were 99.8% and 88.9% respectively.

Embodiment 3

[0057] Such as figure 1 Show: and They are the dosing points of sodium hydroxide and potassium permanganate, which are generally set at the water intake or water pumping station. If neither of them has the dosing conditions, they can be set in the mixing tank or flocculation tank of the water plant; The sodium hypochlorite dosing point is located in the mixing tank; if the mixing tank needs to add other chemicals, the dosing point can be moved to the front of the flocculation tank; The lime water dosing point is located in the front section of the flocculation tank; The dosing point of polymerized ferric sulfate is located in the front section of the flocculation tank, after the lime water dosing point. The residence time of the advection sedimentation tank should not be less than 1h, and the residence time of the inclined tube sedimentation tank should not be less than 0.5h. The sand filter uses a quartz sand filter l...

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Abstract

The invention provides a method for simultaneous removal of cadmium and thallium in raw water. The method comprises the following steps: step A, adding sodium hydroxide into raw water, adjusting a pH value to alkalescence and then adding potassium permanganate with a concentration of 0.3 to 0.8 mg / L; step B, adding sodium hypochlorite or liquid chlorine, wherein the concentration of added sodium hypochlorite or liquid chlorine is 0.5 to 2.5 mg / L in term of effective chlorine; step C, adding limewash into raw water having undergone a full oxidation reaction and adjusting a pH value to 8.5 to 9.0; step D, adding a flocculating agent, carrying out a flocculation reaction for 10 to 20 min and then carrying out deposition for at least 0.5 h so as to remove cadmium, thallium and colloids of manganese hydroxide and iron hydroxide through coprecipitation, wherein the pH value of water after precipitation drops to 7.0 to 8.5; and step E, filtering raw water obtained after precipitation by using quartz sand. The invention has the following beneficial effects: cadmium concentration of treated water is as small as the limit of a detection method, i.e., 0.02 mu g / L, or less than 0.02 mu g / L; thallium concentration of treated water is as small as the limit of a detection method, i.e., 0.01 mu g / L, or less than 0.01 mu g / L; and the pH value, manganese ions and iron ions of the treated water all meet requirements prescribed in drinking water quality standards.

Description

technical field [0001] The invention relates to an emergency treatment method for water plants when urban water supply sources are polluted, in particular to a method capable of simultaneously removing cadmium and thallium when water sources are simultaneously polluted by heavy metals cadmium and thallium. Background technique [0002] In recent years, heavy metal pollution incidents have occurred frequently in drinking water sources in my country, especially cadmium pollution. Due to the coexistence of cadmium and thallium in nature, when cadmium pollution occurs in water sources, it is often accompanied by thallium pollution. Cadmium is extremely harmful to human health. Excessive intake will cause irreversible damage to the kidneys and even lead to necrosis of renal tubular cells; "Itai disease"; at the same time, cadmium can also cause damage to the reproductive system and affect children's intellectual development; cadmium is also a carcinogen confirmed by the Internat...

Claims

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Application Information

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IPC IPC(8): C02F9/04C02F101/20
Inventor 张金松刘丽君王长平尤作亮
Owner SHENZHEN WATER GRP CO LTD
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