Binding Mechanisms of As(III) on Activated Carbon/Titanium Dioxide Nanocomposites: A potential method for arsenic removal from water

Abstract

Novel nanocomposite materials where titanium dioxide nanoparticles were inserted into the walls of a macroporous activated carbon were produced and their efficiency for the removal of As(III) from water was compared with pure activated carbon and titanium dioxide nanoparticles. The nanocomposites were synthesized with different molar ratios by using sol-gel method and were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The nanocomposite system showed excellent capability for the removal of As(III) ions from water by considering feasibility, efficiency and cost. The maximum As(III) removal percentages were ∼4.7% at pH 8 for activated carbon, ∼38 % for titanium dioxide at pH 6, and ∼98 % at pH 7 for activated carbon/titanium dioxide (AC/TiO2) nanocomposite, respectively. According to kinetic sorption data, the higher regression coefficients (R2) were obtained after the application of pseudo-second order to the experimental adsorption data for all adsorbent materials. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The maximum arsenic uptake (qmax) value computed from slope of the linearized Langmuir plot was 26.62 mg/g for the adsorption of As(III) onto AC/TiO2 nanocomposite.