Efficient As(V) removal by alpha-FeOOH and alpha-FeOOH/alpha-MnO2 embedded PEG-6-arm functionalized multiwall carbon nanotubes

Abstract

A novel adsorbents, 6-arm amino polyethylene glycol functionalized multiwall carbon nanotubes (PEG/MWCNT) loaded with alpha-FeOOH (Fe/PEG/MWCNT), and hybrid alpha-FeOOH/alpha-MnO2 nano-deposit (Fe-Mn/PEG/MWCNT) were used for As(V) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on adsorption efficiency was studied. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber-Morris model which predicted intra-particle diffusion as a rate controlling step of overall process. Competitive kinetic study in the presence of interfering ions shows low detrimental effect on both capacity and kinetic of As(V) removal. Thermodynamic parameters showed that the adsorption was spontaneous and endothermic processes. Influences of the pH, iron oxide loading and interfering ions were modeled by using Visual MINTEQ software. High adsorption capacities: 49.39 and 59.78 mg g(-1) were obtained for Fe/- and Fe-Mn/PEG/MWCNT, respectively, and multi-cycle reusability indicated high applicability of obtained material. Two step removal process, in a batch study, was successfully performed by using PEG/MWCNT for cations removal in the first step, and Fe or Fe-Mn/PEG/MWCNT for As(V) removal in the second.