液体高铁酸钠同时去除电镀废水中氰化物和重金属

采用自制的电化学装置在线制备液体高铁酸钠，然后将制得的高铁酸钠投加到电镀废水中进行处理，考察不同pH值和不同高铁酸钠投加量对废水中总氰化物、Cu2+、Ni2+去除率的影响；对比研究了高铁酸钠氧化法和次氯酸钠氧化法在处理低浓度含氰电镀废水的效果。结果表明，当pH为9~10，高铁酸钠的最佳投加量为0.024~0.048 mmol·L-1时，总氰化物、Cu2+和Ni2+的同时去除率均在90%以上；在处理低浓度含氰电镀废水时，高铁酸钠对总氰化物、Cu2+和Ni2+的同时去除率均明显高于次氯酸钠。这是因为高铁酸钠能够有效地氧化多种络合态的氰化物，包括Cu（CN）43-、Cu（CN）42-、Ni（CN）42-等，使废水中的重金属转变为离子态；然后在碱性条件下，在高铁酸盐还原产物-Fe（OH）3助凝和絮凝作用下，反应生成沉淀，达到同时去除氰化物和重金属的目的。

Removal of cyanide and heavy metals in electroplating wastewater by sodium ferrate

Sodium ferrate was prepared using a self-made electrochemical device and the effects of the pH and ferrate dosage used in the preparation on the cyanide,Cu2+,and Ni2+ removal rates from electroplating wastewater by the prepared ferrate were investigated. The experimental results showed the removal rates of cyanide,Cu2+ and Ni2+ could reach above 90% when pH was from 9.0 to 10.0 and the optimal dose of ferrate was in the range from 0.024 to 0.048 mmol·L-1. The removal efficiencies achieved by ferrate or sodium hypochlorite oxidation for electroplating wastewater with low cyanide concentrations were evaluated. Sodium ferrate was found to be more efficient than sodium hypochlorite for cyanide,Cu2+,and Ni2+ removal. Cu2+ and Ni2+ could be released by the oxidation of the cyanide complex with sodium ferrate. The released metal ions and cyanide were then coagulated and settled by the reductive product of ferrate,Fe(OH)3.