one Electroplating equipment Environmental pollution characteristics of wastewater from process manufacturing industry
The wastewater from the electroplating process manufacturing industry has complex water bodies. The wastewater contains chromium, zinc, copper, nickel, cadmium and other metal cadmium positive ions, as well as acid, alkali, cyanide and other dirt with very toxic side effects. The sewage from this manufacturing industry has the following characteristics:
(1) The air pollutants with complicated components can be divided into inorganic air pollutants and organic chemical air pollutants.
(2) The transformation of water body is strong, the types of air pollutants in each share of production wastewater are diverse, and the CODcr transformation index is large.
(3) The sewage has a lot of toxic and side effects and contains a lot of positive metal cadmium ions. If the sewage is not immediately discharged, it will cause huge environmental pollution to the surrounding water quality
2. Confirmation of processing technology plan
The production and manufacturing wastewater of an enterprise mainly comes from the acid and alkali solution of the plated parts before plating and the pickling after plating. In addition, sufficient waste acid will be discharged every quarter.
(1) Normalized treatment of production wastewater
① Removal of Cr6+
At present, the key process of chromium containing electroplating wastewater treatment is oxidation reduction reaction precipitation process
The redox reaction method refers to the use of oxidants or strong reducing agents to oxidize or restore the harmful chemical substances in the sewage to non-toxic or low toxic chemical substances. The key of hexavalent chromium in electroplating wastewater is stored in the form of CrO42 -, and Cr2O72 - under the acid-base standard. Reduction reaction is generated under the effect of ferrous ion, and the reduction reaction is rapid. The recovered chromium is stored in the form of Cr (OH) 3 precipitation under the partial alkali standard, and the sludge obtained is mixed precipitation of trivalent chromium and iron hydroxide. The recovery of hexavalent chromium with ferrous sulfate takes full account of the incomplete reduction reaction. The amount of ferrous sulfate used in the operation is 2.3-3 times the amount calculated by the basic theory, so the amount of sludge is large.
