Adsorption of diclofenac by a novel H2SO4-CTAB co-modified granular spent bleaching earth carbon: Preparation, performance and mechanism

Diclofenac (DCF), a widely used pharmaceutical ingredient, exhibits long-lasting properties and significant ecotoxicity in aquatic ecosystems. In this study, a new granular adsorbent, GSBE@C H-CTAB , was synthesized to remove DCF by initially granulating powder spent bleaching earth carbon (SBE@C) with polytetrafluoroethylene (PTFE) emulsion as a binding agent, followed by a co-modification process involving H 2 SO 4 and cetyltrimethyl ammonium bromide (CTAB). The adsorption capacity of the prepared adsorbent for DCF under the best conditions was 4.26 mg/g. In a wide pH range, GSBE@C H-CTAB could maintain a high adsorption capacity and show a good reusability. The presence of the three cations inhibited the adsorption of DCF (inhibition effect: Mg 2+ >Al 3+ >Na + ). The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir isotherm model. From the theoretical evaluation results, it could be inferred that DCF molecules were adsorbed on GSBE@C H-CTAB surface in both horizontal and non-horizontal directions at all operating temperatures. The main mechanisms of adsorption included electrostatic interaction, pore filling interaction, π-π interaction and H bond interaction. The granular adsorbent GSBE@C H-CTAB prepared in this study could effectively remove DCF, treat waste with waste, and solve the problem that powder adsorbent was easy to lose and difficult to recover, which was of great significance for the remediation of polluted water.