硫自养生物反应器对水中锑酸盐的去除效能和反应机理

The removal of antimonate in aqueous solution in a sulfur autotrophic bioreactor:Performance and mechanism

为了探究硫自养生物过程对水中锑酸盐的去除效能,建立升流式硫自养固定床生物反应器,考察水力停留时间(HRT)对Sb(Ⅴ)和总Sb去除性能的影响,监测分析出水pH值、碱度消耗量变化规律和含硫副产物的产生趋势,利用扫描电镜和拉曼光谱分析表征推测反应机理.结果表明:(1)当进水锑酸盐Sb(Ⅴ)浓度为(1028.07±43.39)μg·L^(-1),HRT为8 h时,经过10~15 d的适应期,反应器对Sb(Ⅴ)去除率可达到94.37%±0.57%,总Sb去除率为47.03%±1.54%,当HRT由8 h缩短为6 h时,反应器对Sb(Ⅴ)去除率可达到90.60%±1.09%,总Sb去除率为12.79%±1.65%.(2)反应器出水硫酸盐超过理论值,表明有硫歧化反应发生,当HRT由8 h缩短为6 h时,碱度消耗量下降至(66.83±6.31)mg·L^(-1),对应pH值降低至7.29±0.09;出水SO_(4)^(2-)浓度出现大幅下降,SO_(4)^(2-)增量由(80.02±1.62)mg·L^(-1)降低至(63.77±1.78)mg·L^(-1),并在20 d后达到稳定.(3)扫描电镜结果表明反应器内球菌和短杆菌数量逐渐增多;拉曼光谱分析结果表明,反应器内沉淀产物为Sb_(2)S_(3)和零价硫的混合物,推测反应机理为锑酸盐在微生物的作用下发生硫自养还原反应,被转化为亚锑酸盐Sb(Ⅲ),而后Sb(Ⅲ)与硫歧化反应产生的S^(2-)生成沉淀Sb_(2)S_(3),从而实现Sb(Ⅴ)的高效还原和总锑的有效去除.研究显示,硫自养生物去除锑酸盐过程受到HRT变化的影响,出水SO_(4)^(2-)超过理论值,硫歧化反应与反应机理密切相关.

An upflow sulfur autotrophic fixed-bed bioreactor was established to investigate the antimonate removal from water by biological process.The effects of hydraulic retention time(HRT)on the removal performance of Sb(Ⅴ)and total Sb,pH,alkalinity consumption and the generation of sulfur by-products were studied.Meanwhile,the reaction mechanism was revealed by using scanning electron microscopy and Raman spectroscopy.Sb(Ⅴ)removal efficiencies stably reached 94.37%±0.57% and the total Sb removal efficiencies were 47.03%±1.54% after 10~15 d of acclimation,under an influent Sb(Ⅴ)concentration of(1028.07±43.39)μg·L^(-1) and a HRT of 8 h.When the HRT decreased from 8 h to 6 h,the removal efficiencies of Sb(Ⅴ)were 90.60%±1.09%,and the total Sb removal efficiencies were 12.79%±1.65%.In addition,results showed that sulfate generation was higher than theoretical value,indicating the occurrence of sulfur disproportionation.When HRT was changed from 8 to 6 h,the alkalinity consumption decreased to(66.83±6.31)mg·L^(-1),and the corresponding pH decreased to 7.29±0.09;There was a significant decrease in SO_(4)^(2-) concentration in the effluent,and the SO_(4)^(2-) increment decreased from(80.02±1.62)mg·L^(-1)to(63.77±1.78)mg·L^(-1),while it was stable after 20 days.Furthermore,scanning electron microscopy images showed that the number of Cocci and Brevibacterium in the reactor gradually increased over time,and results of Raman spectroscopy analysis indicated that the precipitation products in the reactor was a mixture of Sb_(2)S_(3) and S^(2-).It was speculated that Sb(Ⅴ)was reduced to Sb(Ⅲ)by sulfur autotrophic reduction reaction,and then the generated Sb(Ⅲ)reacted with S^(2-) generated by sulfur disproportionation,producing Sb_(2)S_(3)precipitation.Thereby,the total Sb was effectively removed from water.Results demonstrated that the process of sulfur autotrophic antimonate reduction was affected by HRTs,and the effluent SO_(4)^(2-) concentration was higher than the theoretical value.The reaction mechanism for antimonate removal was closely related to the sulfur disproportionation reaction.