Treatment of real wastewater: Kinetic and thermodynamic aspects of cadmium adsorption onto surfactant-modified chitosan beads

Chitosan (CS) beads of d = 3.7 +/- 032 mm diameter containing 97-98% water content were prepared and modified using sodium dodecyl sulfate (SDS) in such a way to form surfactant bilayers on CS beads surface to fabricate surfactant-modified chitosan (SMCS) beads. The characterization of adsorbents was carried out by advanced analytical tools. Adsorption isotherms over a particular range of Cd2+ concentration (10-100 mg/L) in Cd2+ containing distilled water (CCDW) and with varied dose (0.18 to 1.8 g/L) in real wastewater (RWW) were obtained in batch conditions. Kinetic data complied with pseudo-second order model for both the waters. The isotherm data showed that Langmuir model better fitted to the experimental data for CCDW while followed Freundlich isotherm for RWW. Maximum adsorption capacity obtained for CCDW was 125.0 mg/g (C-0 = 10-100 mg/L) and 18.0 mg/g when applied to the RWW containing 10.0-11.0 mg/L of Cd2+. The adsorption parameters for Cd2+ removal in RWW were quite different from CCDW. For instance, the optimum dose value increased from 0.45 to 0.9 g/L due to the presence of other contaminants in RWW. It was found that the adsorption of Cd2+ onto SMCS beads was favorable and spontaneous in CCDW as well as in RWW. (C) 2019 Elsevier B.V. All rights reserved.