矿物-腐植酸-微生物体系对重金属吸附研究

设施农业中土壤重金属污染问题日趋严重。由于土壤中矿物、腐植酸、微生物等多相组分之间存在交互作用,重金属与土壤单组分体系中所获得的结合机制并不能真实有效地评价其在自然条件下的转化与归趋。本研究以蒙脱石(Mont)和高岭石(Kao)为辽宁蔬菜大棚及农田土壤层状硅酸盐代表矿物,选取胡敏酸(HA)为有机质代表,土著微生物革兰氏阳性枯草芽孢杆菌(Bacillus subtilis,B.s)、革兰氏阴性恶臭假单胞菌(Pseudomonas putida,P.p)为细菌微生物代表,以此三元体系为主要供试蔬菜大棚土壤组分,以Cd~(2+)、Cu~(2+)为目标元素,借助宏观吸附实验,结合X射线衍射(XRD)、衰减全反射-傅立叶变换红外光谱(ATR-FTIR)、扫描电镜(SEM)测试分析了Cd~(2+)、Cu~(2+)在矿物-腐植酸-细菌三元混合物上的吸附机理以及Cd~(2+)、Cu~(2+)在复合体上的结合机制。研究结果表明,蒙脱石/高岭石-腐殖酸、蒙脱石/高岭石-B.s及蒙脱石/高岭石-P.p二元复合体对Cd~(2+)及Cu~(2+)的吸附具有加和性,矿物-腐植酸-微生物三元复合体之间表现为拮抗作用。吸附动力学研究表明矿物、有机质、微生物复合体对重金属的吸附动力学符合准二级动力学模型。体系对Cu~(2+)的吸附能力由强到弱为:B. s P. p Mont/Kao-B. s Mont/Kao-P. p Mont/KaoHA-P.p Mont/Kao-HA Mont/Kao。

Adsorption of heavy metal on the ternary system of minerals-HA-bacteria composites

Soil pollution by heavy metal has been gradually serious in facility agriculture. Due to the interaction of soil minerals, organic matter and microorganisms at natural condition, the combination mechanism between soil single component and heavy metal couldn''t represent the reality of the translocation and transformation of heavy metal in the soil. In this research, mechanical mixture of montmorillonite and kaolinite (Mont:Kao=1:1), Gram-positive(Bacillus subtilis, B.s) and Gram-negative (Pseudomonas putida, P.p), and humic acid (HA) were selected as phyllosilicates mineral in vegetable greenhouse and farmland soil, organic matter and bacteria respectively. Cd²⁺ and Cu²⁺ were taken as the target compounds. The adsorption mechanism and interaction on the binding of Cd²⁺ and Cu²⁺ by the ternary composites of Mont/Kao-HA-bacteria were investigated by macroscopy sorption together with XRD, ATR-FTIR and SEM. The experimental results showed that heavy metal ions had the additivity of sorption on Mont/Kao-HA or Mont/Kao-bacteria system, while the antagonism between heavy metal ions and the ternary Mont/Kao-HA-bacteria system. The kinetics data of Cu²⁺ adsorption on mesoporous goethite fitted well the pseudo-second-order equation. The maximum Cu²⁺ adsorption capacities followed the order:B.s > P.p > Mont/Kao-B.s > Mont/Kao-P.p > Mont/Kao-HA-P.p > Mont/Kao-HA > Mont/Kao.