Sustainable utilization of nutmeg fruit rind waste for Cr(VI) removal and resource recovery from industrial wastewater: An integrated approach

Abstract

The present study demonstrates an innovative circular economic process to repurpose agricultural waste, nutmeg fruit rind into an effective adsorbent followed by its value addition/safe disposal, thereby seamlessly aligning with the principles of green chemistry and sustainable waste management. Low-cost bio-sorbents are one of the most promising substances for pollutant removal in water treatment research. Fruit shells and peels are annoying to the environment because they contribute to solid trash after consumption and add to the daunting challenge of municipal solid waste management. This study investigated the potential of nutmeg fruit rind waste, a readily available agricultural byproduct, for the removal of hexavalent chromium (Cr(VI)) from contaminated streams. The findings highlight the significant removal efficiency of Cr(VI) ions through adsorption onto the nutmeg fruit rind waste, underscoring its potential as an affordable and eco-friendly solution for wastewater treatment. The study showed that pH, adsorbent dosage, adsorbate concentration, contact time, and temperature significantly influence adsorption. The insights into the adsorption mechanism revealed that the electrostatic interaction, hydrogen bonding, ion exchange, and surface complexation primarily contributed to the removal of Cr(VI) ions. The kinetics studies matched well with the pseudo-second-order kinetic model, and the sorption fits the Sips isotherm, while thermodynamic studies confirmed the spontaneity and exothermic nature of the process. The quantitative removal of Cr(VI) and other co-existing heavy metals from real textile wastewater samples was demonstrated. Finally, the spent adsorbent was subjected to anaerobic digestion to recover biogas and Cr(VI), which offers a sustainable solution to mitigate the contamination risk associated with discarding the spent adsorbent while contributing to resource recovery.