The main methods for the production of cyanide-containing wastewater recovery treatment are as follows:
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1. Acidification adding an acid to the wastewater, such as sulfuric acid or SO 2, so that pH = 2 ~ 3 of cyanide and copper, zinc and other transition metal complexes as hydrogen cyanide (of HCN), by blowing the exhaust The gas takes the hydrocyanic acid away with the gas stream and then recovers it by neutralizing HCN with an alkali solution. Reaction formula:
2NaCN+H 2 SO 4 =2HCN↑+Na 2 SO 4
Na 2 Zn(CN)4+2H 2 SO 4 =4HCN↑+Na 2 SO 4 + ZNSO 4
2Na 2 Cu(CN) 3 +2H 2 SO 4 =Cu 2 (CN) 2 ↓+2Na 2 SO 4 +4HCN↑
2Na 2 Cu(CN) 3 (CNS)+3H 2 SO 4 =Cu 2 (CNS) 2 ↓+3Na 2 SO 4 +6HCN↑
The gold ore in domestic and foreign gold mines is commonly used to recover cyanide by acidification method. The satisfactory results are obtained. For example, the Shandong Ciaoyuan Gold Mine Cyanide Plant obtained an acidification treatment of 1236.5 mg/L of cyanide-containing wastewater, and obtained a cyanide-containing 58.1 mg/L index. The recovery of cyanide reached 95.30%, and the return and cost were offset.
2. Zinc Sulfate Method The cyanide and cyanide complexes in the cyanide-containing sewage are precipitated and precipitated by the input of zinc sulfate, and the zinc cyanide product is treated with sulfuric acid to recover the cyanide and zinc sulfate products.
2NaCN+ZnSO 4 = Zn(CN) 2 ↓+Na 2 SO 4
Zn(CN) 2 + H 2 SO 4 = ZnSO 4 +2HCN↑
The Japanese Chuanmu Cyanide Gold Extraction Plant used this method to intermittently recover cyanide. The cyanide salt of the gold removal solution was 1510 mg/L; the sedimentation rate reached 96.7%; the cyanide treatment by cyanide was 92.3%; The hydrogen cyanide gas was absorbed by the alkali solution to obtain a cyanide absorption rate of 95.6%. The total recovery of cyanide was 88%.
3. The ion exchange adsorption method using ion exchangers to exchange capabilities, to adsorb cyanide exchange water, to achieve recovery of free cyanide and cyanide complexed purposes, as CN - and [Cu (CN 3)] 2 -. The method not only can recover useful substances, but also can remove the characteristics of harmful impurities, and is suitable for the recovery treatment of cyanide-containing sewage with low concentration and extremely toxic substances. The law was first successfully applied by the Soviet Union. 