Generally speaking, the treatment technologies for electroplating wastewater can be divided into four categories, namely chemical method, physical method, physicochemical method, and biochemical method. At present, the chemical method with relatively low cost and mature technology is the main method, while other processing methods are appropriately supplemented.
The overall principle for treating electroplating wastewater is to divide and treat different water qualities. It is generally divided into chromium containing wastewater, cyanide containing wastewater, and comprehensive wastewater containing heavy metal ions. Chromium containing wastewater. Cr6+in electroplating wastewater is reduced to Cr3+with Na2S2O5, and then precipitated with Hydroxide ion to remove it. Wastewater containing cyanide and alkali. Cyanide in wastewater usually exists in the form of free CN -, HCN and various metal complexes with different stability [Zn (CN) 4] 2-, [Cu (CN) 3] -, etc., which are further oxidized and removed after adding Sodium hypochlorite oxidant. Comprehensive wastewater. As long as the appropriate pH value is adjusted, a considerable amount of hydroxide precipitation will be generated in the comprehensive wastewater containing heavy metal ions. Solid liquid separation. After the reaction, the effluent flows into the inclined tube sedimentation tank, allowing various hydroxides to settle quickly in the inclined tube area. The overflow water from the upper part is filtered by a sand filter before reaching the standard for discharge. The sludge from the lower part is treated by a plate and frame filter press.
The electroplating process should adopt various pollution reduction technologies, with a clean production process as the goal, and transform end treatment into full process control. On the premise of ensuring product quality, use low toxicity or non-toxic substances as much as possible. At the same time, the use of chemical agents and the production of sludge during wastewater treatment should be minimized as much as possible in the process. It is also possible to reduce the pollution of electroplating wastewater by reducing the concentration of plating solution and treatment solution. Try to achieve closed circuit circulation, so that water can be recycled and reused, reducing emissions.
At present, the treatment of electroplating wastewater in China is still relatively weak. It is necessary to study and choose reasonable treatment methods based on reality, in order to achieve the unity of social, economic, and environmental benefits.
