Kinetic and isotherm studies on adsorptive removal of sulfates by cotton shell derived biochar: Recovery of sulfates from marcasite soil

Abstract

This work illustrates the potential applications of the raw cotton shell (RCS) and cotton shell biochar (CSB) in the remediation of sulfate contaminants from aqueous solvents. Comprehensively, optimal batch and adsorption kinetics of sulfate by RCS and CSB were intensively analyzed and determined by varying the adsorption parameters. For RCS, the optimal series of parameters were at (pH-7, sulfate conc-150 mgL−1, adsorbent dose- 0.5 g and time-150 min). While for CSB optimum conditions were at (pH-9.8, sulfate conc-100 mgL−1, dosage- 0.1 g and time-90 min). The maximum adsorption efficiency for both RCS and CSB was achieved at 86.47% and 90.77%, respectively. Sulfate adsorption by RCS and CSB was examined by isotherm models and kinetic studies. The data are best suited to the Langmuir isotherm model with the highest RCS and CSB sulfate adsorption capability of 61.35 and 153.85 mg g−1 and followed pseudo-second-order kinetics. Box-Behnken design (BBD) based response surface methodology (RSM) model-based analysis of variance test has demonstrated optimum conditions and sulfate adsorption by both RCS and CSB. The recovery studies on sulfates from marcasite soil were evaluated at different doses of RCS and CSB. This study provides insights into the usage of the developed process towards the circular economy of the sulfates.