Purification and recovery of cyanide-containing wastewater by ion exchange

The ion exchange process was used to recover cyanide from the wastewater of the gold plant, first studied by the Gould Brady Company in the hilly region of central South Africa. The method is an adsorption column packed with an IRA400 ion exchange resin for adsorbing a metal cyanide complex. Followed by the treated with a copper cyanide is used to remove free cyanide same resin column. The latest of Rohm and Hass is the IRA958 strong alkaline propylene resin, which has been used to remove cyanide from cyanide-containing wastewater, and Homestake Mining Company uses cyanide in the wastewater of the gold plant. IRA958 free cyanide but not removed, it is recommended that prior to ion exchange with Fe (OH) ₃ to react to convert ferricyanide.

In the former Soviet Union, a resin containing quinoline (AB _β·γ ^- 12II) and a methylpyridine (ABФ-12II) group was obtained, and the concentrations of cyanide and thiocyanate were obtained from 120 mg/L and 55 mg/L, respectively. After dropping to 0.06-0.30 mg/L, the complex anion is saturated with the soda solution and can be eluted with a soda solution. The zinc carbonate formed is returned to use, thereby converting simple cyanide into complex cyanide. However, this method has the disadvantage of adding excessive amounts of salt to the wastewater, which causes secondary pollution of the wastewater. In order to solve this problem, a method of pretreating an ion exchange resin column has been proposed to carry out the complexation process in the ion exchange phase. This can eliminate the handling of a large amount of sewage.

The Canadian Centre for Minerals and Energy has used a fixed bed to study the suitability of six gold mines. In a group of IRA400 phenol formaldehyde ion exchange resin columns, cyanide is adsorbed in two columns. In these two columns, the resin is of the sulfuric acid type. The first column with 1% H ₂ SO ₄ desorption, H ₂ SO ₄ is an exploded effect of double metal cyanide complexes, and the lean liquid stream through the filler phenolic resin IR120 ion exchange column to adsorb the metal. At the same time, HCN is collected into the NaOH through the column, and the recovered cyanide can be returned to the gold cyanidation process. The metal is desorbed from the cation exchange column with an aqueous solution of saline. Most of the results obtained are that the ion exchange process can reduce the cyanide in the wastewater to below 0.1 mg/L.

Advantages of the ion exchange method: (1) can reduce cyanide and heavy metals to a very low level; (2) can recover cyanide and metal; (3) can remove hydrosulfate. Its shortcomings: (1) the amount of sulfuric acid desorbed is large; (2) HCN gas is dangerous and must be carefully sealed; (3) the resin bed may be blocked by metal deposits; (4) the investment cost is relatively high.