A.ferrooxidans对高硫煤矸石去除酸性水体中Cr(Ⅵ)的强化作用

The enhancement of Acidithiobacillus ferrooxidans on the removal of Cr(Ⅵ)from acid coal mine drainage by high-sulfur coal gangue

本研究考察了Acidithiobacillus ferrooxidans(A.ferrooxidans)联合高硫煤矸石(富含FeS2)对模拟煤矿酸性水体中Cr(Ⅵ)的去除效果.结果表明,处理Cr(Ⅵ)初始浓度为50mg/L的模拟煤矿酸性废水(pH=2.5)时,投配率为6.67~33.33g/L高硫煤矸石可使Cr(Ⅵ)去除达到良好效果.50mg/LCr(Ⅵ)在24h内即可完全被高硫煤矸石中的FeS2还原成Cr(Ⅲ),且在反应终点时(120h),6.67,13.33,33.33g/L高硫煤矸石对还原产物Cr(Ⅲ)的吸附去除率分别为7.1%、20.2%、29.1%.然而,在高硫煤矸石的还原和吸附作用下,大部分的Cr仍以Cr(Ⅲ)形式残留在酸性水体中,且高硫煤矸石的大量投加也给水体带来了Fe^2+、Fe^3+、SO4^2-等二次污染物.在高硫煤矸石-Cr(Ⅵ)体系中引入A.ferrooxidans和9K培养基后,A.ferrooxidans介导的Fe^2+生物氧化及产物Fe^3+水解矿化过程可促进部分Fe^2+、Fe^3+、SO42-等向次生铁矿物(包括施氏矿物和黄钾铁矾)转变,从而使模拟酸性水体中残留的Cr(Ⅲ)通过次生铁矿物的吸附或共沉淀作用被清除.在A.ferrooxidans强化作用下,模拟煤矿酸性废水中Cr(Ⅵ)在96h即可达到99.4%的去除率.

The removal efficiency of Cr(Ⅵ)in simulated acid coal mine drainage(ACMD)was investigated through Acidithiobacillus ferrooxidans combined with high-sulfur coal gangue(rich in FeS2).Results showed that in stimulated ACMD(pH=2.5)with 50 mg/L Cr(Ⅵ),and 6.67~33.33 g/L of high-sulfur coal gangue could achieve the ideal effect on Cr(Ⅵ)removal.50 mg/L of Cr(Ⅵ)could be completely reduced to Cr(Ⅲ)by Fe S2 at 24 h.7.1%,20.2%and 29.1%of Cr(Ⅲ)was removed via absorption by 6.67,13.33,and 33.33 g/L high-sulfur coal gangue at 120 h,respectively.However,after the reduction and adsorption of high-sulfur coal gangue,most of Cr remains in simulated ACMD as Cr(Ⅲ),and large amount of high-sulfur coal gangue also led to secondary pollutants(Fe^2+,Fe^3+or SO42-).After the introduction of A.ferrooxidans and 9 K medium into high-sulfur coal gangue and Cr(Ⅵ)system,A.ferrooxidans mediated Fe^2+biooxidation and Fe^3+hydrolytic mineralization promoted the conversion of Fe^2+,Fe^3+or SO4^2-to secondary iron minerals(including schwertmannite and jarosite),so that residual Cr(Ⅲ)was removed by adsorption or co-precipitation.Under the enhancement of A.ferrooxidans,the removal efficiency of Cr(Ⅵ)in simulated ACMD could reached as high as 99.4%in 96 h.