Treatment of industrial effluents: unlocking the adsorption potential of wheat straw ash and biochar for chlorpyrifos removal

Abstract

This work presents a novel approach for the removal of chlorpyrifos (CPF) from wastewater effluents through adsorption onto agricultural wheat straw waste. Wheat straw was thermally treated to convert it into wheat straw ash and wheat straw biochar, which served as bio-adsorbents for chlorpyrifos (CPF) from aqueous media. The effect of different factors, such as the mass of WSA and WSB, the concentration of chlorpyrifos (CPF), contact time, reaction temperature, and the pH of the aqueous chlorpyrifos (CPF) solution, was analyzed to determine the set of optimum conditions at which both WSA and WSB showed their maximum adsorption capacities of 3.44 and 3.60 mg g⁻¹, respectively, which correspond to percentage removal values of 86 and 90%, respectively. The kinetic analysis revealed that the adsorption of chlorpyrifos (CPF) onto WSA and WSB is a pseudo-first-order reaction. The adsorption of chlorpyrifos (CPF) on WSA and WSB strongly obeyed the Freundlich and Temkin adsorption isotherms, whereas a relatively weak correlation was observed with the Langmuir adsorption isotherm due to the multilayered adsorption phenomenon. The thermodynamic parameters indicated that the adsorption of chlorpyrifos (CPF) on WSA and WSB is an exothermic and spontaneous process, accompanied by a decrease in orderliness. A reaction mechanism for the adsorption of chlorpyrifos onto WSA and WSB was proposed based on the electrostatic interactions, whereas a comparative analysis with the previously published adsorption studies was also carried out to establish the efficiency and novelty of the reported method.