苯氧羧酸类农药在高岭石表面吸附的理论研究

构建了高岭石铝氧八面体层表面模型Al₁₃O₄₈H₅₇和硅氧四面体层表面模型Si₁₃O₃₇H₂₂,采用B3LYP/6-31G(d,p)方法, 对其与2,4-二氯苯氧乙酸(2,4-D)、 2,4-二氯苯氧丙酸(2,4-DP)、 2,4-二氯苯氧丁酸(2,4-DB)、 2-甲基-4-氯苯氧乙酸(MCPA)、 2-甲基-4-氯苯氧丙酸(MCPP)和2-甲基-4-氯苯氧丁酸(MCPB)等苯氧羧酸类农药分子间的相互作用及吸附性质进行了研究, 包括优化的几何构型、 结构参数、 吸附能及自然键轨道(NBO)电荷. 八面体层表面的中心原子(OH2, OH3及OH11)与四面体层表面的中心原子(O2, O3及O11)并未表现出明显的吸附活性. 相较于侧链为乙酸基的分子, 含有丙酸基或丁酸基的分子因带有更多的吸附位点而具有较强的吸附性. 研究发现MCPP的吸附性高于MCPA. 结合2,4-D的吸附性高于MCPA的结论, 可以推断2,4-D与MCPA更倾向于吸附在高岭石的硅氧层表面. 因此在农药施用的过程中, 应充分考虑各分子的活性及其与高岭石表面的作用强弱, 确保淋洗对去除农药在土壤中残留的可行性.

Theoretical Studies on the Phenoxyalkanoic Herbicides Adsorption on Kaolinite Surface†

Octahedral(Al—O) surface model Al₁₃O₄₈H₅₇ and tetrahedral(Si—O) surface model Si₁₃O₃₇H₂₂ were constructed, and the B3LYP/6-31G(d,p) level was used to research the interaction and properties including optimal structures, structural parameters, adsorption energies, natural bond orbit(NBO) charge distributions, between Kaolinite and 2,4-dichlorophenoxyacetic acid(2,4-D), 2,4-dichlorophenoxypropanoic acid(2,4-DP), 2,4-dichlorophenoxybutyric acid(2,4-DB), 2-methyl-4-chlorophenoxyacetic acid(MCPA), 2-methyl-4-chlorophenoxypropanoic acid(MCPP), 2-methyl-4-chlorophenoxybutyric acid(MCPB). Simultaneously, adsorption of MCPP on Kaolinite surface was stronger than that of MCPA. Combined with conclusion of experiment that 2,4-D has higher adsorption than MCPA, we can infer that 2,4-D and MCPA tend to be adsorbed on tetrahedral surface. Therefore, interaction of herbicides on Kaolinite should be taken full account of to ensure the feasibility of leaching in removing herbiside residues in the process of fertilization.