Quantification of Rate Enhancement Factors of Kaolinite Dissolution by Reaction with Microbes

采用荧光假单胞菌（Pseudomonas fluorescens）对高岭石进行了溶出实验，探讨了细菌对高岭石溶出速率的影响，并阐明了反应机理。用含有卵清蛋白（OVA）的蛋白质体系进行了类似的溶解实验，以证实蛋白质对高岭石溶解速率的影响。细菌系统的溶解实验采用间歇式反应器，含0.2 g高岭石和100 ml 10 mM NaCl溶液，在25℃下，以10^5 ~ 10^9个细胞/ml的细菌进行，时间长达30天。蛋白质体系的溶解实验也采用类似的方法进行，但用0.05、0.1、0.2、0.5和1.0 mg/ml的OVA代替细菌。结果表明，细菌浓度分别为10^5、10^6、10^7、10^8和10^9个细胞/ml时，高岭石的溶出率分别比无细菌对照提高1.6-、2.6-、3.4-、4.6-和10.4倍。随着细菌浓度的增加，溶解铝离子的浓度也比氢氧化铝（如三水铝石）的平衡浓度增加了50倍。对细菌系统溶液中有机分子的化学分析表明，细菌细胞中释放了大量的蛋白质，同时也释放了少量的多糖和有机酸。因此，可以得出结论，这些主要由蛋白质组成的细胞外有机分子通过与高岭石表面相互作用，有助于提高高岭石的溶解速率。它们还通过与溶解的铝离子络合作用导致溶解的铝浓度增加。在含有OVA的蛋白质体系中进行的溶解实验显示，随着OVA浓度的增加，高岭石的溶解率提高了1.5-、2.3-、3.1-、14.2-和16.2倍。这一结果强烈表明，高岭石在细菌系统中的溶解可能通过与细菌细胞释放的细胞外蛋白的相互作用而增强。少

Dissolution experiments of kaolinite in bacterial systems containing bacteria (Pseudomonas fluorescens)were carried out to evaluate the effects of bacteria on dissolution rates and to elucidate the reaction mechanisms. Similar dissolution experiments using proteinic systems containing ovalbumin (OVA) were also performed to confirm the effects of protein on the kaolinite dissolution rates. The dissolution experiments in bacterial systems were performed using batch reactors containing 0.2 g of kaolinite and 100 ml of 10 mM NaCl solution with 10^5 to 10^9 cells/ml of bacteria at 25℃ for up to 30 days. The dissolution experiments of proteinic systems were also conducted using similar methods, however, 0.05, 0.1, 0.2, 0.5, and 1.0 mg/ml of OVA were used instead of bacteria. The results for the bacterial systems indicated that the dissolution rate of kaolinite increased by 1.6-, 2.6-, 3.4-, 4.6-, and 10.4-fold progressively with increasing bacterial concentrations of 10^5, 10^6, 10^7, 10^8 a … More nd 10^9 cells/ml, respectively, relative to the bacteria-free control. The concentrations of dissolved Al ions also increased up to 50 times compared to the equilibrium concentrations of Al-hydroxides such as gibbsite with increasing bacterial concentrations. The chemical analyses of organic molecules in the solutions of bacterial systems revealed that significant amounts of proteins were released from bacterial cells along with lesser amounts of polysaccharides and organic acids. Thus, it can be concluded that these extracellular organic molecules consisting mainly of proteins contribute to the enhancement of the rate of kaolinite dissolution by interacting with the kaolinite surfaces. They also lead to an increase in the dissolved Al concentrations by undergoing complexation with the dissolved Al ions. The dissolution experiments in the proteinic systems containing OVA exhibited greater enhancement in kaolinite dissolution of 1.5-, 2.3-, 3.1-, 14.2-, and 16.2-fold with increasing OVA concentrations. This result strongly suggests that the dissolution of kaolinite in bacterial systems may be enhanced by its interaction with the extracellular proteins released from the bacterial cells by the mechanism of ligand-promoted dissolution. Less