铝粉还原污酸中砷新工艺研究

A new process of arsenic removal from acidic wastewater by aluminum powder

由于硫化精矿中砷含量越来越高,致使烟气处理过程产生的污酸中砷含量也越来越高,同时污酸中含有铜、铁等有价金属。目前污酸除砷方法多以除砷为目的,形成的含砷渣属于危废,还需要二次处理。本研究研发了还原除砷新工艺,首先向污酸中加入硫化砷渣进行脱铜预处理并回收铜,然后用铝粉还原脱铜后液中的砷回收砷,最后向脱砷液中加入硫酸钾回收铝,还原后液回收还原剂后采用两段中和法处理。试验研究结果表明,在加入铜离子摩尔量1.1倍的硫化砷渣、反应温度85℃、反应时间3 h的条件下,污酸中的铜含量由2000 mg/L降至196 mg/L,硫化铜渣返熔炼配料系统;在还原温度70℃、还原时间2 h,还原剂用量1.8倍的条件下,砷的还原率大于96%,还原后液中的砷含量低于300 mg/L,得到的砷渣品位大于95%,可用于后续制备高品位单质砷;在硫酸钾用量1.1倍、反应温度常温、反应时间2 h的条件下,溶液含铝3.6 g/L,得到的明矾可达到《工业硫酸铝钾》(HG/T2565—2007)一等品标准。该方法除砷效果好,且能将污酸中的砷转变为具有经济价值的砷产品,还不会产生硫化氢气体,具有应用推广价值。

As arsenic in the sulfide concentrate is getting higher and higher,the arsenic content in the acidic wastewater produced by the flue gas treatment process is also getting higher and higher,and the acidic wastewater contains valuable metals such as copper and iron.At present,the method of removing arsenic from acidic wastewater is mostly for the purpose of removing arsenic,and the arsenic-containing slag formed belongs to hazardous waste and needs secondary treatment.In this study,a new process of arsenic removal by reduction was developed.Firstly,arsenic sulfide slag was added to the waste acid for copper removal and copper recovery.Then,arsenic in the solution was reduced by aluminum powder to recover arsenic.Finally,potassium sulfate was added to the arsenic removal solution to recover aluminum.After recovering the reducing agent,the final solution was treated by two-stage neutralization method.The following conclusions are obtained through experiments.Under the conditions of adding arsenic sulfide slag with 1.1 times molar amount of copper ion,reaction temperature 85℃and reaction time 3 h,the copper content in the waste acid decreased from 2000 mg/L to 196 mg/L,and the copper sulfide slag was returned to the smelting batching system.Under the conditions of reduction temperature of 70℃,reduction time of 2 h and reducing agent dosage of 1.8 times,the reduction rate of arsenic is more than 96%,the arsenic content in the reduced solution is less than 300 mg/L,and the grade of arsenic slag is more than 95%,which can be used for the subsequent preparation of high-grade elemental arsenic.When the amount of potassium sulfate is 1.1 times,the reaction temperature is room temperature,and the reaction time is 2 h,the solution contains 3.6 g/L aluminum,and the obtained alum can reach the first-class product standard of‘industrial aluminum potassium sulfate'(HG/T2565-2007).This method has good arsenic removal effect,and can convert arsenic in waste acid into arsenic products,and will not produce hydrogen sulfide gas,which has application and promotion value.