Study on the adsorption performance and mechanism of modified nano-ZVI on Cd(Ⅱ),Cr(Ⅵ)and Pb(Ⅱ)
In view of the treatment of heavy metal wastewater of[Cd(Ⅱ)],[Cr(Ⅵ)]and[Pb(Ⅱ)],this study modified nano-zero-valent iron(nZVI)by biochar(BC)and bentonite(BE)to obtain BC-BE-NZVI composite material,and explored the adsorption characteristics of the material for heavy metals through ad-sorption experiments.Adsorption kinetics equation,isothermal adsorption equation fitting,XRD and XPS analysis were used to reveal the adsorption mechanism of BC-BE-nZVI on single and compound heavy metal systems.The results show that BC-BE-nZVI has the strongest effect on the removal of heavy metals,and the removal rate of Cd(Ⅱ),Cr(Ⅵ)and Pb(Ⅱ)can reach 96.43％,97.70％and 95.69％,respec-tively,and can adapt to heavy metal wastewater with a wide pH range.The pseudo-second-order kinetic e-quation and Langmuir isothermal adsorption equation are more suitable for describing the adsorption process of BC-BE-nZVI.In the compound heavy metal system,the adsorption process of BC-BE-nZVI is more suitable for Freundlich isothermal adsorption equation,and the competitive adsorption capacity Cd(Ⅱ)is higher than Cr(Ⅵ).In a single heavy metal system,the removal mechanism of Cd(Ⅱ)mainly in-cludes adsorption precipitation,Cr(Ⅵ)is mainly reduction and adsorption,and Pb(Ⅱ)is mainly adsorp-tion precipitation.The adsorption mechanism of the compound heavy metal system is mainly precipitation and complexation.
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