Sequential removal of oppositely charged multi pollutants from wastewater using sugarcane bagasse

Abstract Efficient removal of organic pollutants from water remains a major challenge. In this work, a circular economy strategy is adopted to address critical challenges associated with excessive waste generation, resource limitations, and economic sustainability. Sugarcane bagasse (SCB), an abundant lignocellulosic agricultural waste, was utilized as a sustainable adsorbent for the sequential removal of oppositely charged dyes from aqueous solutions. Pristine SCB was first employed for the adsorption of the anionic dye Alizarin Red S (ARS), and the resulting spent adsorbent (SCB@ARS) was subsequently reused without regeneration for the removal of the cationic dyes Crystal Violet (CV) and Methyl Green (MG). The adsorbents were characterized using point of zero charge (pH PZC ), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). The effects of adsorption parameters, including shaking time, pH, dye concentration, and adsorbent dose, were studied. The maximum adsorption capacities of SCB for ARS and SCB@ARS for CV and MG were 99.38, 136.84, and 452.26 mg/g, respectively. Kinetic, isotherm, and thermodynamic studies indicated that the adsorption process was best described by the linear pseudo-2nd-order and nonlinear pseudo-1st-order kinetic models and the Langmuir isotherm model, and was thermodynamically feasible and spontaneous. The adsorption mechanism was further elucidated using pH PZC and FTIR analyses. Recovery studies in pharmaceutical and real water samples demonstrated removal efficiencies exceeding 90%. A one-way ANOVA statistical analysis was used to evaluate the effect of pH on adsorption. These findings highlight the potential of sequential adsorption using renewable agricultural waste as an effective and sustainable wastewater treatment strategy.