萃余液中有价金属资源化梯级回收试验研究

Experimental study on the step recovery of valuable metals as resources from raffinate

某低品位硫化铜矿生物堆浸—萃取—电积提铜工艺产生的萃余液中酸、铁含量高,且含多种有价金属。采用常规石灰中和处理工艺未能有效回收有价金属,且造成中和渣二次污染风险。针对传统工艺存在的问题,采用“除酸降铁+硫化沉铜+硫化沉锌+树脂回收铝+中和”资源化梯级回收工艺处理萃余液,实现酸性废水处理目标的同时实现有价金属的资源化回收。结果表明:石灰石除酸降铁,在pH=3.0时,铁去除率为98.7%;硫化沉铜,在电位为-50 mV时,铜回收率为90%以上;硫化沉锌,在电位为-150 mV时,锌回收率为90%以上;沉锌后液用离子交换树脂回收铝,制得水合硫酸铝一等品产品;吸附后液采用石灰中和至pH=7.5~8.5,中和渣石膏纯度为98%以上,废水达标排放。该工艺实现了废水中有价金属的资源化利用,降低了固废渣的堆存量,并大大降低了环境风险,经济和技术上可行。

Raffinate generated in bio-heap leaching-solvent extraction-electrowinning operation for copper extraction is high in acidity and iron concentration,and contains many kinds of valuable metals.The conventional neutralization treatment fails to effectively recover metals and causes risks of secondary pollution of neutralization residue.In order to solve the problems in conventional methods,the raffinate was treated by the step-recovery-as-resources process of"acid removal and iron reduction+copper precipitation by sulfuration+zinc precipitation by sulfuration+aluminum recovery in resin+neutrali-zation",which realizes the goal of acidic wastewater treatment as well as recovery of valuable metals as resources.The results show that when pH of limestone used for acid and iron removal is 3.0,98.7%of iron is removed.On the sulfuration condition with redox potential of-50 mV,copper recovery is over 90%;zinc recovery rate is over 90%by sulfuration when the redox potential to-150 mV;the aluminum is recycled in ion exchange resin from post-zinc-precipitation solution and first-class aluminum sulfate hydrate is prepared;post-aluminum-removal solution is neutralized with lime to pH 7.5-8.5,the purity of gypsum is more than 98%in neutralization residue,and the wastewater is discharged meeting the standards.The process is economically and technically feasible,which utilizes valuable metals in wastewater as resources from wastewater,reduces the residue stock and greatly mitigates environmental risks.