生物膜与钝化膜的形成对铝土矿细菌脱硅的影响

Effects of biofilm and passivation coating forming on bacterial desilicon from bauxite

生物膜与钝化膜分别可以提高和降低铝土矿细菌溶硅速率.研究了细菌-矿物接触/非触模式下胶质芽孢杆菌HJ07对铝土矿浸出脱硅的影响,分析了浸出过程中铝土矿表面生物膜与钝化膜的形成及对溶硅的影响.结果表明：在铝土矿细菌浸出的前期（0~6d）,Al与Si的溶出主要受间接接触模式的影响,铝土矿表面无生物膜与钝化膜形成;在6~12d内,Si的溶出主要受接触模式的影响,Si的溶出速率明显较非接触模式快,12d后,浸出液中SiO2的浓度比非接触模式的高15mg/L左右,铝土矿表面形成了明显的生物膜;在8~12d内,接触模式下Al的溶出速率明显变缓,非接触模式下明显下降,铝土矿表面有Al2O3沉淀产生;12d后,Si的溶出达到浸出终点,而上清液中Al2O3浓度显著下降;细菌代谢产生的胞外聚合物的絮凝作用下,Al2O3沉淀是铝土矿表面钝化的主要原因.生物膜的形成可以促进铝土矿细菌溶硅,Al2O3沉淀所形成的钝化膜对Al与Si的溶出有明显的抑制作用.

Bacteria can promote and stop silicon dissolution from bauxite by biofilm and passiva- tion coating, respectively. The effect of Bacillus mucilaginosus HJ07 on desilicon of bauxite was studied in the microbe-mineral contact /uncontact model, and the effects of biofilm and passivation coating forming on bacterial desilicon was investigated. The results show that A1 and Si are mainly dissolved by the uncontact mechanism, and there are not biofilm and passiva- tion coating forming on bauxite surface during 6 d leaching. The Si is mainly released by the di- rect contact mechanism, and has higher dissolution velocity than that by the uncontact mecha- nism during a 6-12 d culturing. After 12 d leaching, the concentration of SiO2 is about 15 mg/L higher in the supernatant of contact model than that in the supernatant of uncontact model, and there is obviously biofilm forming on bauxite surface. During a 8--12 d leaching, the rate of A1 dissolution in the contact model slows down with the extension of time, and decreases in the uncontact model, and there is A1203 sediment on bauxite surface. After 12 d leaching, the Sidissolution reaches to finishing point, but the A1203 concentrations in supernatants obviously decrease, especially in that of the contact model. The A12 03 sediment easily generated on baux- ite surface at flocculation of extracellular polymeric substance in leaching supernatants is the main cause of surface passivation of bauxite. The biofilm formation can promote Si dissolution and A1203 passivation coating has an obvious inhibition on A1 and Si dissolution.