电解氧化法处理黄金冶炼厂选冶废水

Treatment of selection and smelting wastewater from gold smelter by electrolytic oxidation

采用电解氧化法处理同时含有高浓度氰化物与COD的黄金冶炼厂选冶废水,主要考查了外加电压、溶液pH、电解时间及极板间距等因素对氰化物和COD去除率的影响,充分利用原水中Cl^(-)的阳极氧化效应,深入探讨了电化学氧化过程及污染物氧化去除机理。结果表明,随着外加电压和电解时间的增大,氰化物和COD去除率逐渐增大。以石墨为阳极,钛合金为阴极,采用一阴两阳电解体系对废水进行氧化,当电压为4.5 V、初始pH为7、电解时间为3 h、极板间距为1.5 cm的条件下,总氰化物(CNT)、COD、SCN^(-)及Cu的去除率最高可达99.6%、96%、99.9%与99.2%。电解过程中体系pH逐渐降低,电场作用下定向迁移至阳极附近的污染物去除主要归因于HClO及ClO^(-)的间接氧化作用,当pH大于5.0时以HClO的氧化为主,ClO^(-)的氧化为辅,而pH小于5.0时则主要是HClO的氧化。电解氧化过程中约有36.17%的Cu与SCN^(-)形成CuSCN沉淀而被除去,剩余的铜则扩散至阴极沉积析出。GC^-MS分析表明,烷烃类、酯类、酮类等大分子的C=C键、酯基、羰基等化学键和官能团被氧化断链成小分子物质,随后继续被氧化为H2O、CO_(2)和N2。

The electrolytic oxidation method was used to treat the selection and smelting wastewater from gold smelter containing both high concentrations of cyanide and COD, the effects of applied voltage, solution pH,electrolysis time and plate spacing on the removal rate of cyanide and COD were studied. The anodic oxidation effect of Cl-in raw water were fully used to deeply explore the electrochemical oxidation process and pollutant oxidation removal mechanism. The results showed that with the increase of applied voltage and electrolysis time, the removal rates of cyanide and COD gradually increased. With graphite as the anode and titanium alloy as the cathode, the one-cathode and two-anode electrolysis system was taken to oxidize the wastewater, and the maximum removal rates of the total cyanide(CNT), COD, SCN^(-)and Cu could reach 99.6%, 96%, 99.9% and 99.2%, respectively, when the voltage was 4.5 V, the initial pH was 7, the electrolysis time was 3 h, and the plate spacing was 1.5 cm. During the electrolysis process, the pH value of the system gradually decreased, and the removal of pollutants that directionally migrated to the anode under the action of the electric field was mainly attributed to the indirect oxidation of HClO and ClO^(-), at pHs higher than 5.0, HClO oxidation was the main pathway, while ClO^(-)oxidation was an auxiliary one, at pHs lower than 5.0, only HClO dominated the oxidation. During the electrolysis and oxidation process, the CuSCN precipitate was formed through the reaction of 36.17% Cu with SCN^(-), which could be removed accordingly. The surplus of Cu diffused to anode and the electrodeposition occurred. GC-MS test indicated that the chemical bonds and function groups such as C=C bond, ester group, carbonyl group in large molecular organics such as paraffins, ester and ketones were oxidized and degraded into small molecular organics, then were continuously oxidized to H2O、CO_(2)and N_(2).