Adsorption and removal of a selected emerging contaminant, carbamazepine, using Humic acid, Humasorb and Montmorillonite. Equilibrium isotherms, kinetics and effect of the water matrix

Abstract

Carbamazepine is an antiepileptic drug that is not easily degraded in the environment. In this study, the removal of carbamazepine, an emerging contaminant, dissolved in deionized water and wastewater matrices by means of their adsorption onto Humic Acid, Humasorb and Montmorillonite was investigated. The effect of various parameters including adsorption time, adsorbent dosage, and initial adsorbate concentration was determined. The optimum exposure time for the removal of carbamazepine by Humic Acid was 30 min and by Humasorb and Montmorillonite were 2 h, in both distilled and wastewater. The maximum percent removal of carbamazepine by Humic Acid, Humasorb and Montmorillonite in deionized water was 90.5 ± 3.1%, 85.2 ± 2.3% and 83.8 ± 4.5% and in wastewater was 87.0 ± 1.5%, 87.3 ± 5.1% and 78.2 ± 1.2%, respectively, when the initial concentration of carbamazepine was 20 µg/mL and the mass of absorbent 100 mg in 10 mL samples. Three isotherms models including Langmuir, Freundlich, and Elovich were applied to the experimental data. It was found that the adsorption isotherms for the two adsorbents best matched Langmuir model indicating surface adsorption from deionized water (R2= 0.986 for Humic Acid, R2 = 0.955 for Humasorb and R2 = 0.865 for Montmorillonite) as well as from wastewater (R2 = 0.893 for Humic Acid, R2 = 0.949 for Humasorb and R2 = 0.984 for Montmorillonite). According to the kinetic studies, the pseudo-second-order kinetic model better fits to the removal of carbamazepine by the three adsorbents from both water matrices. However, pseudo-second-order model cannot exclusively explain the experimental data trend, but it could be explained by diffusion.