What are the common treatment methods for electroplating wastewater?
Electroplating wastewater treatment method can be summarized as: physical method, chemical method, physical chemistry method and biological treatment method.
1 physical method
Physical treatment in waste water is a state of suspension of pollutants by using their own physical sedimentation separation removal way, the material in the whole process of physical and chemical properties do not change, mainly including evaporation concentration method, chromatography.
Evaporation enrichment is the process of reducing the moisture in the bath by evaporation, so as to achieve the solution of concentrated solution and recovery and utilization.
It is commonly used to treat wastewater containing chromium, copper and nickel ions.
The crystallization method is to use the solid-liquid separation principle to precipitate the metal salt in the saturated solution of the salts in the form of crystals to achieve the purpose of removing or recycling the valuable materials.
2 chemical methods
Cic chemical methods is to waste water and chemicals, abolish the toxicity of pollutants, change its physicochemical properties, target pollutants or turned into non-toxic harmless material is easy to be separated from water, in order to achieve the purpose of the removal of contaminants.
The commonly used chemical methods include oxidation treatment, reduction treatment, neutralization treatment, flocculation sedimentation, etc., and the combination of several methods is legal.
(1) reduction method
Reduction method is mainly aimed at the wastewater containing chromium electroplating wastewater, chromium in waste water is mainly exist and Cr3, Cr6, + + two forms, under acid condition, Cr6, + the reducing effect by reducing agent into first Cr3, +, in alkaline conditions, after chromium hydroxide precipitate removal is generated by neutralization precipitation, often using ferrous sulfate, sodium bisulfite, sodium bisulfite, sodium metabisulfite reductant.
The main advantage of this method is that the equipment is simple, easy to operate and management, the sludge sediment is small and easy to be recycled, so it is widely used, and the disadvantage is that it may cause secondary pollution.
Oxidation method is mainly used to deal with cyanide wastewater, mainly alkaline chlorination, electrolysis oxidation, hydrogen peroxide oxidation and ozone oxidation.
A. basic chlorination.
Basic chlorination method, the principle is to use chlorine or liquid chlorine, bleaching powder to oxidize the cyanide in wastewater to C02 and N2 .
There are two stages in the cyanide decomposition of alkaline chlorination: the first stage is to oxidize the cyanide with cyanide, which is called incomplete oxidation, under the strong alkaline environment of pH>10.
In the second phase, under the weak alkaline environment of pH>8.5, the oxidation of cyanate is further decomposed into carbon dioxide and nitrogen, which is called total oxidation.
Defect is liquid chlorine storage difficulties, easy to leak, cause poisoning, active chlorine content is low, large amount of sludge, the water pump is easy to jam, high treated effluent residual chlorine content, to operators harm is bigger, reagent consumption is big, easy to corrode equipment.