Performance of organoclay in adsorptive uptake of antihypertensive losartan potassium: A comparative batch study using micro-grain activated carbon

Abstract

The antihypertensive losartan potassium is an emerging pharmaceutical contaminant that has been traced in aquatic media; hence, up-to-date water treatment methods are urged. This paper is the first of its kind to examine losartan uptake by adsorption using an organophilic clay, Spectrogel. In comparison, a micro-grain activated carbon (μGAC) was employed. Adsorption kinetics, isotherms and thermodynamics were examined and characterizations were performed. Pseudo-first order, pseudo-second order, external diffusion, surface diffusion and pore diffusion models were adjusted to kinetic data, and Langmuir, Freundlich and Dubinin-Radushkevich models were correlated to isotherms. Adsorption mechanisms were elucidated for surface features and surface chemistry. The latter was unraveled to have a crucial role on losartan removal by Spectrogel. The best adsorbent dosage was stablished as 6 g/L and initial solution pH (2.5-10) had no significant impact on the process. Spectrogel exhibited faster kinetics and superior maximum adsorption capacity (~2200 min, 0.0820 mmol/g) than μGAC (~2600 min, 0.0441 mmol/g). Compared to water or ethanol eluents, methanol showed the highest efficiency as desorption agent (65%). The results indicate that Spectrogel organoclay is a potential non-traditional adsorbent for losartan remediation