Effect Of Soil PH And Redox Potential Co-driven On The Adsorption State Of Copper On Graphene Oxide Surface

Graphite oxide oxide（GO）,as a new carbon based nano material,has the characteristics of fast adsorption rate and large adsorption capacity for heavy metal pollution in the water and soil environment,which shows a broad application prospect.Research has shown that GO prepared by chemical methods consists of a carbon layer with local defects（bw GO）and oxidized fragments（OD）attached to its surface,with binary composition characteristics.The adsorption of heavy metals by GO is mainly achieved through the cooperation of chemical bond between oxygen containing radicals and heavy metal ions that are distributed on the surface of bw GO sheet,layer edge,pore edge and OD surface.Under the action of alkalinity,the peeling of OD on the surface of GO leads to the desorption of heavy metals;Under the action of reducing potential,GO undergoes deoxygenation reduction,greatly reducing its adsorption capacity and leading to the desorption of heavy metals.Up to now,the relevant research is limited to the influence of pH or Eh,and the synergistic change of pH and Eh is a typical water chemical process in the soil planting layer.The desorption characteristics of heavy metals adsorbed on GO surface during the change of pH+Eh are still blank.Conduct research on this issue in order to provide theoretical support for the development of GO heavy metal pollution control technology.In this study,the reduction of GO,stripping of OD,and the process and effect of desorption of the resulting adsorbed state Cu under pH+Eh modulated conditions were achieved by an electrochemical workstation and a simulated soil column using Cu（Ⅱ）as the target pollutant,and the main results of the study are as follows:（1）The Cu²⁺adsorption capacity of GO and reduced graphene oxide（reductive GO,r GO）mainly comes from the oxygen-containing functional groups on their surfaces,which is consistent with the proposed secondary adsorption kinetic model and belongs to chemisorption;the pH value has a significant effect on the degree of reduction of r GO;（2）During the conversion of redox potential Eh from 200 m V to-200 m V,the adsorbed Cu（Ⅱ）on the surface of GO-Cu（Ⅱ）was desorbed due to the reduction of oxygen-containing functional groups on the GO surface,and the resolved Cu existed mainly as free Cu（Ⅱ）ions in the system at pH=4;in the system at pH=7,it existed as free Cu（Ⅱ）and complexed OD-Cu（Ⅱ）;at pH=8,it was mainly desorbed as complexed OD-Cu（Ⅱ）and stabilized in the liquid phase;（3）The migration of OD in the background solution can be explained by the classical DLVO theory,and the coexisting Cl^-1 and Cl O₄^-1 anions in the solution have little effect on the migration of OD;the penetration rate of OD increases from 70%to 80%when the pH of the permeate in the soil column increases from 4 to 8,while the penetration rate of OD-Cu（Ⅱ）increases from 57%to 63%.