两种典型炭材料对微生物还原含砷水铁矿的影响及其机制研究

Mechanism of two representative carbonaceous materials impact on microbial reduction of arsenic-bearing ferrihydrite

研究了活性炭和生物炭对Shewanella oneidensis MR-1还原含砷水铁矿过程的影响,并探究了这一过程中砷的释放、转化及其在次生矿物中的分布。研究结果表明:在培养初期活性炭和生物炭抑制了含砷水铁矿中铁的微生物还原过程,可能的原因是活性炭和生物炭抑制了菌的生长,荧光染色结果证实了这一过程;在培养中期,微生物逐渐适应培养环境,并使铁还原持续进行,培养结束时活性炭和生物炭显著增加了含砷水铁矿中铁还原的比例。培养基中的磷酸根通过置换作用使水铁矿中的部分砷释放至溶液,而微生物还原含砷水铁矿过程中,活性炭和生物炭抑制了溶液中砷的去除。此外,微生物还原含砷铁矿过程中,依次生成了蓝铁矿和菱铁矿两种次生矿物。SEM-EDX结果表明,在两种次生矿物中,砷主要被蓝铁矿固定。该结果有助于我们从氧化还原的角度评估活性炭和生物炭在农业环境应用过程中的环境效应。

The effect of activated carbon and biochar on microbial reduction of arsenic-bearing ferrihydrite was studied.The results indicated that activated carbon and biochar inhibited microbial reduction of arsenic-bearing ferrihydrite[As(Ⅴ)-FH]at the initial stage,which was ascribed to the microbial cell toxicity of activated carbon and biochar and supported by the fluorescence staining analysis at 48 h.With the prolonging of incubation time,the microbial cell adapted to the culture environment at 120 h,and reduced Fe(Ⅲ)in As(Ⅴ)-FH efficiently.With further increase of incubation time to 246 h,activated carbon and biochar greatly promoted the extent of Fe(Ⅲ)reduction in As(Ⅴ)-FH.Moreover,the removal of As from the supernatant was inhibited by the addition of activated carbon and biochar.The secondary minerals vivianite and siderite were formed in sequence during microbial reduction of As(Ⅴ)-FH,and As was mainly immobilized by vivianite.The study provides a new insight into the mechanism of the effect of carbonaceous materials on the transformation and release of As from As-bearing mineals mediated by microbe in the naturally occurring environment.