重金属酸性废水处理(一):分步硫化回收砷和铜的工艺研究

Heavy Metal Acidic Wastewater Treatment-Part 1 :Study on Step-by-step Vulcanization Process for Arsenic and Copper Recovery

重金属酸性废水因成分复杂难直接循环利用,直接外排对环境和人体会造成严重污染和危害,因此研究回收重金属酸性废水中有价元素具有重要意义。重金属酸性废水处理方法较多,主要有化学沉淀、离子交换、膜分离、反渗透、吸附法等,但现有方法实际应用效果均不理想,在现有文献分析的基础上,根据山东恒邦冶炼股份有限公司产出的重金属酸性废水成分,提出采用分步硫化法回收重金属酸性废水中的铜和砷。经过多次试验,试验取得较好的回收效果。以重金属酸性废水含铜5.32g/L、砷8.41g/L为原料,对硫化沉铜中关键影响因素机械搅拌转速、硫氢化钠滴加时间、硫氢化钠浓度及用量进行试验考察,确定了最佳工艺条件:机械搅拌器的转速为1100r/min,硫氢化钠理论用量1.4倍,硫氢化钠的质量浓度为20%,控制滴加硫氢化钠的时间2h;根据硫化沉铜条件对沉铜后液进行二次硫化沉砷。采用硫氢化钠理论用量1.2倍时,取得较好的试验效果,重金属酸性废水中的铜、砷回收率都达到99.5%以上。二次硫化后液经除铁-沉锌-三效蒸发,可回收铁渣、碳酸锌和硫酸钠产品,实现重金属酸性废水有价元素的综合回收。

Heavy metal acidic wastewater is difficult to recycle directly due to its complex composition,and directly discharging it to the environment will cause serious pollution and harm to the environment and human body,so it is important to study the recovery of valuable elements in heavy metal acidic wastewater.There are many methods for treating heavy metal acidic wastewater,mainly including chemical precipitation,ion exchange,membrane separation,reverse osmosis and adsorption,but the practical application effect of the existing methods is not ideal.Based on the analysis of existing literatures,step-by-step vulcanization method was proposed to recover copper and arsenic from heavy metal acidic wastewater according to the composition of heavy metal acidic wastewater produced by Shandong Humon Smelting Co.,Ltd.After many tests,good recovery results have been achieved.Taking heavy metal acidic wastewater with copper content of 5.32 g/L and arsenic content of 8.41 g/L as the raw material,the key factors influencing the sulfide precipitation for copper such as mechanical mixing speed,dripping time of sodium hydrosulfide and concentration and dosage of sodium hydrosulfide were tested to determine the best process conditions,i.e. the speed of mechanical agitator is 1100 r/min,the dosage of sodium hydrosulfide is 1.4 times the theoretical amount,the mass concentration of sodium sulfide is 20%,and the dripping time of sodium hydrosulfide is controlled below 2 h.Secondary sulfide precipitation for arsenic was carried out for the liquid after copper precipitation according to the conditions of sulfide precipitation for copper.When 1.2 times the theoretical dosage of sodium hydrosulfide was used,good test effect was obtained,and the recovery rate of both copper and arsenic in heavy metal acidic wastewater were higher than 99.5%.After the secondary vulcanization,the liquid was subjected to iron removal,zinc precipitation and three-effect evaporation to recover iron slag,zinc carbonate and sodium sulfate products,so as to achieve the comprehensive recovery of valuable elements from heavy metal acidic wastewater.