Kinetic, adsorption, and thermodynamic study of removal of Cr6+ by iron-rich natural clay minerals
Shilpa Yakkerimath, Raviraj M. Kulkarni, Sanjaykumar V. Divekar, Vaibhav R. Chate, Kunkangar Purandara Bekal
Abstract
The study explores the adsorption behavior of unmodified natural clay as an ecologically acceptable procedure in the treatment of toxic elements such as Cr6+ in wastewater. Batch experiments were conducted by stirring 30 ml of a Cr6+ solution and natural clay for 3 hours at different temperatures, pH, Cr6+ loadings, and concentrations. Characterization of natural clay before and after adsorption was studied by XRD, FTIR, and BET for surface area, SEM, and EDX for surface topography. The Cr6+ content was analyzed by UV-visible spectrophotometer further, the mechanism of the process was illustrated by isotherm and kinetic studies. Cr6+ maximum sorption capacity obtained was 12.3 mg/g at pH 3. The overall process followed the Langmuir model elucidating monolayer adsorption as a major, in addition kinetics study (pseudo-2nd-order) describes accurately that chemisorption is a rate-controlling stage. Thermodynamics measurements indicated a spontaneous and endothermic process involved throughout the adsorption. Therefore, the study highlights the efficacy of unmodified natural clay as an efficient adsorbent for the elimination of Cr6+ from aqueous solution.