Removal of bisphenol A by adsorption on organically modified clays from Burkina Faso

Abstract

Four cationic surfactants with various length and number of long alkyl chains such as dodecyltrimethylammonium, tetradecyltrimethyl-ammonium, hexadecyltrimethylammonium and didodecyldimethyl-ammonium were intercalated at different concentrations into two natural clays from Burkina Faso via solid-state reaction. Each organoclay was used to explore bisphenol A (BPA) removal from water. Various factors including adsorbent dose, agitation time, concentration, surfactant loading levels, pH and temperature were evaluated. Further, pseudo-first and pseudo-second kinetics, Langmuir and Freundlich isotherms and thermodynamics of adsorption onto organoclays were investigated. The adsorption mechanism was perfectly described by pseudo-second-order kinetic model and Langmuir isotherm. Spontaneous and exothermic processes were associated with BPA removal. This study showed that both physisorption and chemisorption are involved in BPA adsorption. Adsorption capacities ranging from 88 to 127 mg/g were observed at ambient temperature and acidic environment. The ranking of organoclays sorption capacities depends on the surfactant loading level. The pH effect on the adsorption showed a remarkable decrease in the quantity of BPA removed when pH ≥ 10. The BPA amount adsorbed onto the organoclays was not varying significantly for pH < 10. Organoclays prepared via solid-state surfactant intercalation are as effective adsorbents for BPA removal from water as those prepared in aqueous solution through cation exchange.