Li Qinyi, Shi Weiyu, Yang Qingyuan
School of Geographical Sciences, Southwest University, Chongqing 400715, PR China; Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing 400715, PR China.
School of Geographical Sciences, Southwest University, Chongqing 400715, PR China.
J Hazard Mater. 2021 Jun 15;412:125168. doi: 10.1016/j.jhazmat.2021.125168. Epub 2021 Jan 16.
Classically, stable covalent bonding cannot occur between heavy metal cations and clay surface O atoms. However, the classical theory ignores the effect of the electric field arising from clay surface charges on the orbitals of surface O atoms. This article studies the adsorption behavior of heavy metal cations (Pb, Cd, Cu, and Zn) on charged montmorillonite surfaces from a new theoretical foundation based on the quantum mechanics analysis of surface O atoms in this electric field, which reveals that polarization-induced covalent bonding is a strong adsorption force. The strength of polarization-induced covalent bonding can be controlled by regulating the energy of the lone-pair electrons of surface O atoms, which depends on solution pH, electrolyte type, electrolyte concentration, temperature or dielectric constant of medium, etc. The mathematic relationship between the energy of lone-pair electrons of surface O atoms and electric field arising from surface charges was established through quantum mechanics analysis; and correspondingly the mathematical relationship between the polarization-induced covalent bonding energy and surface potential also was established for different heavy metal cations. The finding of the new adsorption force will have important impact on both theoretical research and removal/deactivation approaches of heavy metal cations.
传统上，重金属阳离子与黏土表面的O原子之间无法形成稳定的共价键。然而，经典理论忽略了黏土表面电荷产生的电场对表面O原子轨道的影响。本文基于对此电场中表面O原子的量子力学分析，从新的理论基础研究了重金属阳离子（Pb、Cd、Cu和Zn）在带电蒙脱石表面的吸附行为，结果表明极化诱导共价键是一种强大的吸附力。极化诱导共价键的强度可通过调节表面O原子孤对电子的能量来控制，而这取决于溶液pH值、电解质类型、电解质浓度、温度或介质介电常数等。通过量子力学分析建立了表面O原子孤对电子能量与表面电荷产生的电场之间的数学关系；相应地，也建立了不同重金属阳离子的极化诱导共价键能与表面电位之间的数学关系。这一新吸附力的发现将对重金属阳离子的理论研究以及去除/失活方法产生重要影响。
