Study On The Stability Of Lead Adsorbed On Graphene Oxide Surface In Microbial Metabolic Environment

Due to the pollution of surface runoff and the discharge of industrial sewage and wastewater,the pollution of heavy metals in the soil and water environment in my country is becoming more and more serious.The removal of heavy metal pollution in water is usually the adsorption method.Among many adsorbents,Graphene Oxide(GO)has attracted wide attention due to its excellent heavy metal adsorption performance,but the water environmental stability of this adsorption system is also worthy of attention.Shewanella putrefaciens(S.p),which is ubiquitous in the natural environment,has the ability to act electrons on a variety of substances,and can reduce the oxygen-containing groups on the surface of the carbonaceous adsorbent to cause the desorption of adsorbed heavy metals.Aiming at the stability of GO surface-adsorbed lead(GO-Pb(Ⅱ))under S.p metabolism conditions.In this paper,three-dimensional fluorescence spectroscopy,Fourier infrared spectroscopy,XPS spectroscopy and electrochemical methods were used to study the changes of GO-Pb(Ⅱ)system under S.p metabolic conditions,the desorption characteristics of adsorbed Pb(Ⅱ),and The released Pb(Ⅱ)storage morphology is analyzed,and the migration characteristics and influencing factors of the adsorbed Pb(Ⅱ)in the simulated sand layer are discussed and understood.The main findings are as follows:(1)The adsorbed Pb(Ⅱ)desorbed from the GO-Pb(Ⅱ)surface under S.p metabolic conditions,and the reaction reached equilibrium after 72 hours.The biomass concentration and initial pH value were the main influencing factors.The desorption degree of Pb(Ⅱ)under the conditions of 30 mL,20 mL,and 10 mL biomass concentrations were 5.76%,1.87%,and 0.55%,respectively.Under the conditions of initial pH values of 6.0,7.0 and 8.0,the desorption degree of Pb(Ⅱ)was 6.35%,5.76%and 8.54%,respectively.Under the conditions of initial pH values of 6.0 and 7.0,some of the Pb(II)released into the solution formed Pb9(PO4)6 and Pb10(PO4)6(OH)2,respectively.The EPS produced by S.p combines with the released Pb(Ⅱ)to form an EPS-Pb(Ⅱ)complex stably existing in the solution.(2)Through XPS energy spectrum and FTIR characterization,it is found that the release of Pb(Ⅱ)on the GO-Pb(Ⅱ)surface is mainly due to the reduction of OCGs on the GO surface by S.p,which causes the reduction of adsorption sites.In the reaction system with S.p added,the CV curve obtained by the cyclic voltammetry test has a much larger surrounding area than the system without S.p,and there is an obvious redox peak,indicating that the r-obtained by the catalytic reduction of GO by S.p respiration drive r-(GO-Pb(Ⅱ))has good electronic conductivity,which can promote the electron conduction between the microorganism and the electrode,and promote the reduction of the oxygen-containing oxygen on the surface of GO-Pb(Ⅱ)under the conditions of S.p metabolism and cause the release of adsorbed Pb.(3)In the quartz sand filter layer,the migration of EPS-Pb(Ⅱ)is affected by the solution IS,and the recovery rate of Pb(Ⅱ)is different under different backgrounds.Under deionized water,0.001 mol·L-1,0.01 mol·L-1 and 0.1 mol·L-1 ionic strength,the recovery rates of Pb(Ⅱ)were 97.8%,95.25%,84.89%and 78.97%,respectively.Under the background of 10 mL and 20 mL S.p,the recovery rate of Pb(Ⅱ)is 92.4%and 91.8%,which is slightly lower than that of deionized water.With the increase of IS,The mobility of EPS-Pb(Ⅱ)is reduced.