Experimental Study Of The Adsorption Of Arsenic(?) To The Amino-modified Carbon Nanotubes/polyaniline

Low concentration of arsenic contamination is one of the problems affecting the safety of drinking water.To promote the As(?)adsorption capacity on carbon nanotubes(CNTs),the modification of CNTs was conducted in this study.Firstly,CNTs were modified with oxidation and amination,followed by reaction with polyaniline(PANI)to obtain amino-modified carbon nanotube/polyaniline(NCNTs/PANI).And the optimum modified conditions of the NCNTs/PANI were determined by the As(?)removal rate in micro-polluted water after the treatment of adsorption.Both the modified and pristine carbon nanotubes were observed by scanning electron microscope to compare their morphological differences.Their specific surface,functional groups and molecular structure were also determined.The results show that the tubular shape partially dissolves,and polyaniline is supported on it,forming porous material with bigger specific surface area.The total pore volume,average pore size of NCNTs/PANI increased,and the surface oxygen and nitrogen-containing groups all increased after modification.The NCNTs/PANI was used to remove As(?)from aqueous solution,and the effects of NCNTs/PANI dosage,temperature,initial pH,contact time,initial concentration of As(?)and coexisting anion on the removal of As(?)were investigated.The enhanced adsorption behavior of NCNTs/PANI for As were further studied.Under the experimental conditions,large NCNTs/PANI dosage and longer time can make better removal rate of As(?)by NCNTs/PANI.The increased temperature could significantly shorten the adsorption equilibrium time.The initial pH has significant effects on the As(?)removal rate,while the coexisting anions have a negligible effect on As(?)adsorption.The removal rate of As(?)by NCNTs/PANI is better than that by natural CNTs.The As(?)saturation capacity of NCNTs/PANI is 1.4 times as large as that of natural CNTs.Moreover,The addition of oxidant can further improve the As(?)removal rate,indicating that the adsorption has a synergistic effect of oxidation.The adsorption isotherms of NCNTs/PANI fitted well with the Langmuir,Freundlich and Temkin model at different temperatures.The adsorption of As(?)on NCNTs/PANI was an endothermic,entropy-increasing and spontaneous process with the coexistence of physisorption and chemisorption.The kinetic data fitted well with the pseudo-first-order and pseudo-second-order kinetic model,which demonstrated that chemical adsorption was the main mechanism,such as the supported active groups can chelate As(?)by chemical bond.The NCNTs/PANI has well adsorption capacity for As(?)in quueous solution,and the method of prepared NCNTs/PANI is simple and convenient,which provides a new method for solving the problem of low concentration of As(?)pollution in drinking water.