Abstract:

In order to solve the problem of standard discharge of high concentration cyanide-containing wastewater in a Guangdong electroplating plant，aiming at the characteristics of high concentration of ferricyanide complex in cyanide-containing wastewater，the advanced treatment technology of two-step precipitation coupled with H₂O₂ oxidation，was used to treat the wastewater with high concentration of cyanide. The effects of the dosage of precipitant and H₂O₂，pH on the removal effect of total cyanide，free cyanide and heavy metal ions were mainly investigated. The results showed that when the conditions were under the mass ratio of the actual dosage of FeSO₄ to the theoretical dosage of 1.5 and reaction pH=8，the mass ratio of the actual dosage of ZnCl₂ to the theoretical dosage of 2 and reaction pH=6，the mass concentration of total cyanide in wastewater decreased from 51 400 mg/L to 1.65 mg/L after the two-step precipitation process using FeSO₄ and ZnCl₂ as the precipitant，respectively. Furthermore，the cyanide-containing wastewater after two-step precipitation treatment was further oxidized by H₂O₂. The mass ratio of the actual dosage of H₂O₂ to the theoretical dosage was 1.8，and the reaction pH was 9. After treatment，the mass concentration of total cyanide could be reduced to less than 0.5 mg/L，and the overall removal rate of total cyanide was nearly 100%. Copper，chromium，zinc could be treated to less than 0.3，0.5，1 mg/L，respectively. Thus，this process also had good treatment effect on heavy metal ions，which could satisfy the first class discharge standard of Integrated Wastewater Discharge Standard（GB 8978—1996）.

Key words: two-step precipitation, advanced treatment, ferricyanide complex, cyanide-containing wastewater

摘要：

为解决广东某电镀厂含氰废水达标排放问题，针对含氰废水中铁氰络合物浓度高的特点，采用两步沉淀耦合H₂O₂氧化工艺深度处理高浓度含氰废水，重点考察了沉淀剂及H₂O₂投加量、反应pH等因素对总氰、游离氰、重金属离子去除效果的影响。结果表明，在硫酸亚铁实际投加量与理论投加量之比（质量比）为1.5、反应pH=8，氯化锌实际投加量与理论投加量之比（质量比）为2、反应pH=6时，高浓度含氰废水经硫酸亚铁和氯化锌两步沉淀处理后，废水总氰质量浓度从51 400 mg/L降低至1.65 mg/L；两步沉淀处理后的含氰废水进一步经H₂O₂深度氧化，H₂O₂实际投加量与理论投加量之比（质量比）为1.8、反应pH=9，处理后总氰质量浓度可降至低于0.5 mg/L，总氰综合去除率接近100%；铜、铬、锌等重金属离子可分别处理至<0.3、<0.5、<1 mg/L，该工艺对重金属离子也具有较好的处理效果，处理后的废水主要指标能够达到《污水综合排放标准》（GB 8978—1996）一级排放标准。

关键词: 两步沉淀, 深度处理, 铁氰络合物, 含氰废水

CLC Number: 

• X703.1