Preparation of organically functionalized silica gel as adsorbent forcopper ion adsorption

A novel adsorbent (AMPS-silica) was synthesized by bounding AMPS (2-acrylamido-2-methylpropanesulfonic acid) onto silicasurface, which functioned with -methacryloxypropyltrimethoxysilane reagent. The adsorbent was characterized by nitrogen adsorption/desorption measurement, thermogravimetric analysis (TGA) and potentiometric titration analysis. The TGA result indicated thatthe surface modification reactions introduced some organic functional groups onto the surface of silica. The surface area of AMPSsilicawas 389.7 m2/g. The adsorbent was examined for copper ion removal in series of batch adsorption experiments. Results showedthat the adsorption of Cu2+ onto AMPS-silica was pH dependent, and the adsorption capacity increased with increasing pH from 2 to 6.The adsorption kinetics showed that Cu2+ adsorption was fast and the data fitted well with a pseudo second- order kinetic model. Theadsorption of Cu2+ onto AMPS-silica obeyed both Freundlich and Langmuir isotherms, with r2 = 0.993 and r2 = 0.984, respectively.The maximum Cu2+ adsorption capacity was 19.9 mg/g. The involved mechanism might be the adsorption through metal binding withorganic functional groups such as carboxyl, amino and sulfonic groups. Cu2+ loaded on AMPS-silica could be desorbed in HNO3solution, and the adsorption properties remain stable after three adsorption-desorption cycles.