| The applications of cyanide are involved in many industries, with the production and application of cyanide, a large number of cyanide-contained wastewater has been generated. Because of the hyper toxicity of cyanide, the discharge of the wastewater containing cyanide can cause great threat to environment. Recently, the various treatment methods of cyanide wastewater have its own advantages and disadvantages. According to different sources and the properties of cyanide-contained wastewater, all aspects should be considered so as to the best treatment method can be selected. The cyanide-contained wastewater generated from a chemical plant in ChongQing was used as the research object in the paper, based on the fully analysis of the advantages and disadvantages of various treatment methods, the chemical precipitation—Fenton oxidation combined method was chose to deal with the cyanide-contained wastewater according to the characteristics of high concentration of the total cyanide and COD in the wastewater. The best technical parameters through the experimental study will take certain theoretical significance and guiding role in the actual cyanide-contained wastewater treatment process.Using chemical precipitation as the preliminary treatment of wastewater bearing cyanide, though the single factor experiment, the removal rate effect that the effect factors on the easy release of cyanide, total cyanide and COD were investigated., the orthogonal tests were carried out according to the single factor experiment results, and the important degree of influence factors were fixed. Then the optimal operation parameters were determined as: FeSO4·7H2O dosage 1.8 times of the theoretical value, pH value was 6, the response time was 90min. The wastewater was treated by complex precipitation, then the total cyanide in the out water after precipitation can be decreased to about 10mg/L, the removal rate can reach 94% above, meanwhile, the removal rate of COD can reach to 78.85%, then the COD concentration was decreased to 4522mg/L.We use Fenton reagent to oxidize the cyanide and COD in wastewater. Though the orthogonal test,the effect levels that the pH value, the concentration of H2O2 and FeSO4·7H2O, reaction time on the total cyanide and COD removal rate were investigated. Use the Fenton reagent to oxidize complex precipitated water, all influence factors effect on the removal effects of the total cyanide and COD were analyzed though the single factor and the optimal technical parameters were determined. Difference removal efficiency of total cyanide and COD were compared in different initial concentration, the impact on COD removal by the iron ions, copper ions and calcium hydroxide was studied. The results showed that: in the Fenton oxidation phase, the best process parameters are pH=3, the H2O2 dosage is 32.5mg/L, the FeSO4·7H2O dosage is 2.5mg/L, the stirring time is 100min. The cyanide-contained wastewater that though chemical precipitation was treated by Fenton oxidation process, the remove efficiency of the total cyanide can reach over 99%, and removal rate of COD can reach 86% above. In addition, adding the Fe3+ and using Ca(OH)2 regulared the final pH of water can reduce the COD content further, but copper ions can inhibit the oxidation system to some extent.The combined treatment process of chemical precipitation-Fenton reagent oxidation, in Fenton oxidation phase, the pH was regulated after precipitated effluent water directly, using the favorable conditions that the primary treated effluent water's low pH and few Fe2+,Fe3+ remained in the system. the total cyanide concentration in final effluent water dropped to 0.5mg/L below, then achieved first discharge standard of wastewater discharge standards. Meanwhile, COD concentration dropped to about 600mg/L from 21380mg/L, the total removal rate can achieved 97% above.
|
PDF Full Text Request