Adsorption of 2,4-Dichlorophenoxyacetic Acid Herbicide from Aqueous Solution by Using Cement Kiln Dust Solid Waste

The current study examined the adsorption of the herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) on cement kiln dust (CKD) which is a solid waste generated in a large quantity from cement industries. This study investigated the impact of contact time, pH (2–11), CKD dosage (1–6 g/100 mL of 2,4-D) and initial concentration of 2,4-D (20 to 120 mg/L) on the performance of CKD. The optimal conditions for the adsorption process were achieved at a pH of 4, a CKD dose of 1 g/100 mL of 2,4-D, a concentration of 100 mg/L and a contact time of 180 min. The adsorption equilibrium data were analyzed using nonlinear curve fitting to fit them to four different adsorption isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich). The Langmuir isotherm model accurately characterizes the equilibrium data, as evidenced by the high determination coefficient (R²) value of 0.9912. The maximum monolayer coverage capacity ( \({q}_{m}\) $q_m$ ) was determined to be 10.47 mg/g. The kinetic data were modelled using the pseudo-first order, pseudo-second order, Elovich, Boyd and intraparticle diffusion models. The kinetics data strongly supports the chemisorption mechanism. The rate-determining step governing the adsorption process was determined to be a mix of external mass transfer and intraparticle diffusion. Because exhaust adsorbent can be reused in numerous applications such as in agriculture and soil stabilization without further treatment, the CKD can be used economically and efficiently (chemisorption nature) for the adsorption of 2,4-D from aqueous solution. This work promotes an environmentally sound solution for managing water contamination.