Spontaneous separation of Pb from PbSO_(4)-coprecipitated jarosite using freeze-thaw cycling with thiourea  

硫脲冻融循环法分离硫酸铅-黄钠铁矾共沉淀物中的铅

作　　者：Jun PENG Yang-jin WEI Mei-qing SHI Jia-hui WU Qing-wei WANG Zhang LIN Hui LIU Xu YAN 彭俊;魏杨金;史美清;吴佳蕙;王庆伟;林璋;刘恢;颜旭(中南大学冶金与环境学院,长沙410083;国家重金属污染防治工程技术研究中心,长沙410083)

机构地区：[1]School of Metallurgy and Environment,Central South University,Changsha 410083,China [2]Chinese National Engineering Research Center for Control&Treatment of Heavy Metal Pollution,Changsha 410083,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第3期1019-1030,共12页中国有色金属学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51904355,51825403);the National Key R&D Program of China(No.2020YFC1909201)。

摘　　要：To separate Pb from PbSO_(4)-coprecipitated jarosite,a novel thiourea-induced freeze-thaw cycling(T-FTC)process was investigated.Results show that distributed PbSO_(4)particles are pressed and aggregated around the jarosite particles by T-FTC.Under the freezing-concentration effect of T-FTC,the reaction between PbSO_(4)and thiourea is also promoted,forming lead thiourea sulfate(Pb-tu).As the cycles of T-FTC increase,PbSO_(4)around jarosite disappears for the reaction of forming Pb-tu.After 12 cycles of T-FTC,a spontaneous separation is observed between Pb-tu and jarosite,i.e.,Pb-tu is separated into the upper layer while jarosite-rich phases remain in the lower layer.Due to this spontaneous separation,leaching toxicity of the jarosite coprecipitates is reduced by 73.7%.These results suggest that T-FTC process can achieve the separation of Pb from PbSO_(4)-coprecipitated jarosite and is a promising approach for removing and recovering metals from iron-rich jarosite residues.采用硫脲冻融循环法分离硫酸铅-黄钠铁矾共沉淀物中的铅。研究结果表明,在硫脲冻融循环过程中,共沉淀物中混杂的硫酸铅逐渐在黄钠铁矾表面聚集,同时通过冷冻浓缩作用促进硫酸铅与硫脲反应,形成硫脲铅(Pb-tu)新物相。随着冻融循环次数的增加,黄钠铁矾周围的硫酸铅不断转化为Pb-tu,直至反应完全。12次冻融循环后,黄钠铁矾和Pb-tu发生自发分层现象,即黄钠铁矾沉于底部,而Pb-tu浮在黄钠铁矾的上层,从而实现铅的分离。分离后黄钠铁矾沉淀的浸出毒性比分离前降低了73.7%。本研究表明,硫脲冻融循环法在分离硫酸铅-黄钠铁矾共沉淀物中的铅和铁矾渣中有价金属回收方面具有较大的应用潜力。

关 键 词：jarosite residues PbSO4 freeze-thaw cycling THIOUREA SEPARATION 

分 类 号：X75[环境科学与工程—环境工程] TF812[冶金工程—有色金属冶金]