碳酸盐矿化菌固结Pb2+的生物矿化

为了研究碳酸盐矿化菌在修复重金属污染过程中的生物矿化作用及其在不同污染体系下对生物矿化的影响,以从南京栖霞山土壤中筛选出的一株耐受Pb的碳酸盐矿化菌株——Bacillus cereus Pb₂₁为研究对象,选用葡萄糖作为底物,采用扫描电子显微镜(SEM)和X射线衍射(XRD)等分析测试手段对其矿化产物进行表征.结果表明:碳酸盐矿化菌可以利用2%葡萄糖底物诱导下的酶化作用将游离态Pb2+转变为稳定态PbCO₃,从而达到修复环境中Pb2+污染的目的.不同污染体系下的生物矿化分析结果显示,随着pH的升高,矿化产物的平均粒径也在变大,由pH为3时的约24 μm增至pH为9时的99 μm.而且,当环境溶液为中性或碱性(pH为7、9)时,矿物生成的速度较快,结晶较好,Pb2+的固结率达到90%以上；而当pH较低(pH为3、5)时,晶体不易成核生长,Pb2+的固结率低于60%.ρ(Pb2+)对Pb2+固结率的影响差异较小,几乎都在90%以上,但是其对矿化产物结构形态的影响较大,随着ρ(Pb2+)的增加,矿化产物的形态越清晰,对微生物矿化固结重金属形成矿化产物也越有利. 

Study on the Consolidation and Mineralization of Pb2+ by Carbonate-Mineralization Bacteria

A Pb-tolerant carbon mineralization strain, Bacillus cereus Pb₂₁, isolated from soil of Qixia Mountain in Nanjing City, was investigated. The role of the isolated strain in the remediation of Pb-polluted soil and its performance in different pollution systems were investigated. In addition, the yielding products of the biomineralization process using glucose as substrate were characterized by means of scanning electron microscope(SEM), X-ray diffraction(XRD), etc. The results demonstrated that the carbonate-mineralization bacteria could transform Pb2+ into PbCO₃ by the substrate-induced enzymatic process and achieve the remediation of Pb-polluted soil. Characterizations of mineralization products under different pollution systems showed that the average particle size of the products increased from 24 to 99 μm with rising solution pH. Moreover, when the solution was neutral or alkaline with pH 7 and 9, the mineralization process was very fast with good crystallized products, and the consolidation rate of Pb2+ mostly exceeded 90%. In contrast, the acidic solution(pH 3, 5) was against the crystal nucleation and growth, with less than 60% of Pb2+ consolidation achieved. In addition, the concentration of Pb2+ did not exert obvious influence on the consolidation rate, which was mostly higher than 90%, but it affected the morphology and structure of mineralization products significantly. Clearer morphology and better consolidation of heavy metals were observed in relatively high Pb2+ concentrations.