Adsorption of sulfate in aqueous solutions by organo-nano-clay: Adsorption equilibrium and kinetic studies

CHEN Wei(陈卫)¹, LIU Hai-cheng(刘海成)^{1, 2}

(1. College of Environment, Hohai University, Nanjing 210098, China;
2. Department of Environmental and Municipal Engineering, Henan University of
Urban Construction, Pingdingshan 467036, China)

Abstract:The adsorption of sulfate in aqueous solutions onto organo-nano-clay prepared by natural zeolite and cationic surfactant cetyltrimethylammonium bromide (CTAB) was studied. Parameters such as adsorbent dosage, contact time and temperature were investigated using batch adsorption studies. The results show that the uptake of sulfate increases with the increase of contact time and temperature, and decreases with the increase of dosage. The Freundlich isotherm model is fit to explain the sulfate adsorption onto organo-nano-clay. The maximum adsorption capacity is found to be 38.02 mg/g at 40 °C. The kinetic data fit well the pseudo-second-order and Elovich models with a R² more than 0.98. It is suggested that chemisorption is the rate-controlling step for adsorption of sulfate onto organo-nano-clay, meanwhile both intraparticle diffusion and boundary layer diffusion also contribute as well. Ion-exchange between sulfate anions and bromide ions and complexation between sulfate anions and CTAB cations are responsible for the mechanism of sulfate adsorption.

Key words:organo-nano-clay; cetyltrimethylammonium bromide (CTAB); modification; sulfate; adsorption