Sorption of 2,4-Dichlorophenoxyacetic Acid from Agricultural Leachate Using Termite Mound Soil: Optimization Using Response Surface Methodology

Abstract

The extensive use of 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide leads to the contamination of surfaces and groundwater. In this respect, it is critical to develop an inexpensive and environmentally friendly adsorbent for 2,4-D-laden agricultural leachate. In the current study, termite mound soil (TMS) from Ethiopia was used as an adsorbent in a batch mode aimed at the removal of 2,4-D from an aqueous solution. The TMS was characterized using Brunauer–Emmett–Teller (BET), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), atomic absorption spectrometry (AAS), and X-ray diffraction (XRD) techniques. The effects of various operating parameters such as pH, contact time, adsorbent dose, and initial concentration were investigated. In addition, the optimization process and interaction effect were studied using response surface methodology (RSM). A high 2,4-D removal percentage (89.6%) was achieved for a 2,4-D initial concentration of 50.25 mg/L at pH 2, an adsorbent dose of 15.25 g/L, and a contact time of 180.5 min. The 2,4-D adsorption isotherms could be adequately described by the Langmuir model (R2 = 0.9687), while the kinetics of the 2,4-D adsorption on the TMS best fit the pseudo-second-order model. Overall the study showed that TMS is an effective adsorbent for the removal of 2,4-D from agricultural leachate.