Utilization of Agricultural Waste as Low-Cost Adsorbents in Dye Wastewater Treatment: Kinetic and Thermodynamic Study

Abstract

In recent years, the treatment of dye wastewater has attracted more attention because of its harmful impact on the environment. Therefore, dye wastewater should be treated using effective treatment methods, such as adsorption, which is widely employed to remediate many dyes from wastewater. This work studied the use of Laurus Nobilis Leaves (LNL) and sawdust (SD) as low-cost natural adsorbents to remediate reactive blue (RB) dye from synthetic wastewater under the influence of their dosages (0.5-5.5 g) for each, pH (3-9), and contact time (10-190 min). The experimental design, analysis of results, and optimization were conducted using Response Surface Methodology (RSM) based on Box-Behnken method (BBM) and the Minitab-Statistical program. The BET and FT-IR tests have been used to characterize these adsorbents, which show that SD-adsorbent includes more pore volume and surface area than LNL-adsorbent. The adsorption isotherms study revealed that Langmuir isotherm was a more fitted model than Freundlich model. Adsorption kinetic shows that the current adsorption process obeys the pseudo-second order model (R2=0.998) compared to the pseudo-first order model (R2=0.973) and the intraparticle diffusion model (R2=0.915). Thermodynamics study revealed that the present adsorption is endothermic, random irregularity at the solid-liquid, and a spontaneous nature. More than 60% of RB-dye removal efficiency was achieved at the optimal conditions, which were 5.5 g of SD-adsorbent, 0.8 g of LNL-adsorbent, pH 3, and 141 min of the contact time. The core results proved that the interaction effect of using multi-natural adsorbents was significant and cost-effective, providing considerable removal of dye from wastewater.