Microwave electrodeless lamp assisted catalytic degradation of X-GRL with manganese dioxides:Adsorption and manganese(IV)reductive dissolution effects

摘要

This study focuses on the adsorption and microwave assisted-oxidation of Cationic Blue(X-GRL)on hydrous manganese oxides(delta MnO2)and commercial MnO2(beta MnO2).The effects of X-GRL adsorption and Mn(IV)reductive dissolution are investigated.delta MnO2 exhibits higher adsorbing potential for X-GRL than beta MnO2 does,with dissolved organic carbon(DOC)removal potential(removed DOC at per gram MnO2)of 4.92 and 0.31 mg/g,respectively.The ratio of absorption at different wavelength(A_(202 nm)/ A_(300 nm)/A_(610 nm))and ratio of DOC to A_(610 nm)(R_(DOC)/A_(610 NM))varies after adsorption.This implies the electron transfer between manganese oxides surfaces and X-GRL,which is confirmed by dissolved Mn(II)concentration increase.delta MnO2 exhibits more remarkable oxidizing effect than(3MnO2 does.X-GRL adsorption onto delta MnO2 involves in hydrogen bonding and electrostatic interactions,which is inhibited by Ca~(2+)presence and favored at higher pH.Manganese species(delta MnO2,beta MnO2 and Mn~(2+))facilitates X-GRL degradation and DOC removal in O2/MWL systems,and more significant effects are observed for delta MnO2 due to its combined effects of adsorption and catalysis.The k_(app)(apparent reaction constant)in the initial 10 min with delta MnO2 presence is about 2.5 and 4.2 times higher than that with beta MnO2 and Mn~(2+)presence,respectively.However,with reactions continuing,DOC mineralization is inhibited in heterogeneous systems due to the adverse effect of high dissolved Mn~(2+)concentration.