细菌在两种土壤矿物表面吸附的热力学分析

运用表面热力学方法和扩展的DLVO理论,对两种典型土壤细菌恶臭假单胞菌(Pseudom onasputida)和枯草芽孢杆菌(Bacillus subtilis)在代表性土壤黏粒矿物高岭石和蒙脱石表面的吸附进行了分析,获得了黏粒矿物与细菌作用的疏水自由能变(ΔGH)和静电力自由能变(ΔGEL)及总自由能变(ΔG)。发现疏水自由能为负,显示疏水作用为引力,有利于细菌在黏粒矿物表面的吸附;而静电力自由能为正,表明细菌-矿物间存在静电斥力。疏水自由能显著大于静电力自由能,表明疏水作用在黏粒矿物对细菌吸附时的贡献大于静电力。两种细菌与两种矿物间的总吸附自由能为负值,意味着细菌在矿物表面的吸附是热力学自发过程。高岭石对细菌的吸附自由能大于蒙脱石对细菌的吸附自由能,表明细菌与高岭石间的亲和力较高,吸附更容易发生,这与化学吸附及滴定量热结果一致。表面热力学方法和XDLVO理论在预测细菌-矿物相互作用中有重要意义,但该方法未考虑多种非DLVO效应,如细胞表面多聚物、细菌鞭毛等在吸附反应中的作用,因此还存在一定的局限性,在揭示细菌-矿物相互作用的热力学机理方面还需与其他研究技术结合。

Surface thermodynamical analysis of adsorption of bacteria on two soil clay minerals

Based on surface thermodynamics and XDLVO theory, free energy changes induced by hydrophobic interactions (GH), free energy changes originated from electrostatic force (GEL) and the total free energy changes in the adsorption of P. putida and B. subtilis on kaolinite and montmorillonite were obtained. The negative values of GH and the positive values of GEL suggested that the hydrophobic force favors, and the electrostatic force unfavors the bacterial adsorption on kaolinite and montmorillonite. The absolute values of GH were much larger than those of GEL, indicating that hydrophobic interactions play a role more important than electrostatic force does in bacterial adsorption. The negative total free energy changes (G) suggested that the sorption of bacteria on clay minerals is a thermodynamically spontaneous process. Greater G values for bacterial adsorption on kaolinite than on montmorillonite indicated higher affinity of the bacteria for kaolinite than for montmorillonite.