Preparation Of Fe-based Nanoparticles And Removal Of Chlorinated Methanes From Aqueous Solution

Carbon tetrachloride?CCl₄,CT?,chloroform?CHCl₃,CF?and dichloromethane?CH₂Cl₂,DCM?have been frequently detected in water environment worldwide,which results in environmental pollution and potential biohazardous having attracted increasing concern.It is extremely urgent to seek efficient technologies and methods for eliminating these contaminants.In this study,Fe-based nanoparticles of sulfide-modified nanoscale zerovalent iron?S-nZVI??sodium carboxymethylcellulose stabilized nanoscale zerovalent iron?CMC-Fe??sodium carboxymethylcellulose stabilized nanoscale zerovalent iron and nickel?CMC-Fe/Ni?and activated carbon fibers supported zerovalent iron and nickel?ACF-Fe/Ni?were synthesized and used to the dechlorinated reduction of CT and CF and the oxidation decomposition of DCM.Several vital parameters and the reaction kinetics were investigated,and the possible degradation mechanism was proposed.The main results are listed as follow:?1?CT could be effectively removed by S-nZVI and CMC-Fe,and the efficiency of CT removal increased with the initial concentration of CT decreasing and reaction temperature increasing.The initial pH had a positive correlation with the reactivity of S-nZVI,whereas had no obvious effect on the reactivy of CMC-Fe.The addition of external solute inhibited the removal of CT in varying degree except for the introduction of Na₂SO₃ accelerating CF degradation.The degradation of CT fitted well with the pseudo-first-order kinetics pattern and the Ea value was low.CF was the principal product of CT dechlorination by direct electron transfer in nZVI system.?2?CF could be effectively removed by CMC-Fe/Ni and ACF-Fe/Ni,and the efficiency of CF removal increased with the initial concentration of CF decreasing,reductant dosage increasing and reaction temperature increasing.The initial pH had a negative correlation with the reactivity of ACF-Fe/Ni,whereas had no obvious effect on the reactivy of CMC-Fe/Ni.The existence of NO₃^-and HPO₄^2-largely inhibited the removal of CF and both of Na₂S and Na₂S₂O₄ almost completely suppressed the reactivity of the two reductants.The degradation of CF fitted well with the pseudo-first-order kinetics pattern.DCM was the main product of CF dechlorination by direct electron transfer and H*attack in Ni sites under Fe-based bimetal system.?3?DCM could be effectively removed in the both S-nZVI+H₂O₂ and ACF-Fe/Ni+H₂O₂ Fenton-like systems.In both systems,the highest efficiency of DCM degradation was achieved at initial pH of 2.0 and increasing or decreasing pH significantly reduced DCM removal efficiency.In the ACF-Fe/Ni+H2O2 system,there was an optimum value of ACF-Fe/Ni dosage and H2O2 concentration for DCM removal,and the deficiency or overdose was not conducive to the removal of DCM.The existence of solute inhibited the degradation of DCM and the inhibition degree of HPO₄^2-and Cl^-was higher.In addition,the quenching experiment and EPR analysis indicated that the·OH produced by the two systems plays a key role in the removal of DCM,and subsequently proposed the possible mechanism of DCM degradation.