Study On The Passivation Of Soil Heavy Metals Montmorillonite/graphene Oxide Composites

Soil heavy metal pollution is becoming more and more serious at home and abroad,and it is harmful to human health through food chain enrichment.Soil is one of the most important natural resources in a country,so we should pay attention to the sustainable management of soil.In situ passivation remediation technology is one of the most suitable methods for heavy metal contaminated soil treatment in China.Therefore,a new efficient and green soil passivator is urgently needed.In this study,the passivator was prepared by sol-gel method,vacuum filtration method and ultrasonic dispersion technology.The montmorillonite/graphene oxide composite(MGB)was prepared by using cationic surfactant benzyl two methyl eighteen alkyl ammonium chloride hydrate(BCH)as binder.The effects of different factors on the adsorption of Cr(?)and Pb(?)on MGB were studied.Finally,the soil around Shuitou Town Industrial Park in Pingyang County of Wenzhou City was used as the test soil to explore the passivation effect of MGB on Cr and Pb contaminated soil.The main results are as follows:Compared with Mt,MGB surface is more rough,with larger interlayer spacing and pore size,and go does not agglomerate.The pHpzc of MGB composite is between 6.0-8.5,COOH and Mt in go form a cross-linking network in adsorbent,and MGB surface has more abundant oxygencontaining functional groups.The adsorption capacity of MGB 10 for Pb(?)is 50.56mg/L,which is 1.41 times of Mt,the adsorption capacity of MGB 10 for Cr(?)is 25.09mg/L,which is 12.87 times of Mt.The adsorption of Pb(?)and Cr(?)by MGB 10 includes physical adsorption and chemical adsorption.MGB 10 adsorbed with Pb(?)was desorbed by simulated acid rain.When pH value of simulated acid rain was 4,the desorption rate was 0.41%.When the pH value of NaOH was 9,the desorption rate was 0.21%.The results of EDS,FTIR and XPS showed that MGB 10 mainly adsorbed Pb(?)and Cr(?)by ion exchange and complexation,and a new hydroxyl absorption peak appeared after adsorption of Pb(?).After adsorption of Cr(?),the surface of MGB 10 has 92.84%Cr(?),and reduction reaction occurred in the process of mgb10 adsorbing Cr(VI).Compared with Mt,MGB 10 had better passivation effect.The passivation efficiency of MGB10 was 100%and 84.38%under the condition of passivation 112d and 3%dosage.The leaching concentration of Pb and Cr(?)did not exceed the class ? water standard(0.05 mg/L).The results showed that the residual content of Pb was higher than that of Cr,and the content of residual and Fe-Mn oxides in the tested soil was higher.The addition of MGB10 had a significant negative correlation with the content of Pb and Cr available in the soil.With the increase of MGB10 dosage,Pb and Cr in the soil transformed into more stable forms;With the increase of MGB10 dosage,the contents of available Si and exchangeable Mg increased significantly,and the exchangeable Mg and available Si were negatively correlated with the contents of available Pb and Cr.