Synthesis and Characterization of Metal Oxide– <i>Prosopis Juliflora</i> Activated Carbon Nanocomposites for the Removal of Cr ⁶ ⁺ From Aqueous Solutions

ABSTRACT Prosopis juliflora (mesquite) is a widespread invasive species in India that threatens native biodiversity, rangelands, and agro‐pastoral livelihoods by forming dense thickets, exhausting water resources, and suppressing native flora. The aim of this study is to develop and evaluate sustainable, biomass‐derived adsorbents by converting the invasive plant Prosopis juliflora into activated carbon and further enhancing its adsorption performance through metal oxide functionalization (CuO, Fe 2 O 3 , and ZnO). Specifically, to investigate the comparative efficiency, adsorption behavior, and removal mechanism of these metal oxide–Prosopis juliflora activated carbon nanocomposites for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions under varying experimental conditions. In this study, activated carbon derived from Prosopis juliflora was prepared through calcination at 600°C and subsequently used to synthesize metallic oxide nanocomposites via the co‐precipitation method. These nanocomposites were applied as adsorbents to get rid of hexavalent chromium (Cr 6+ ) ions from aqueous solution. The materials were characterized by IR, BET, SEM, and XRD analyses. Among the composites, PJAC@CuO exhibited the highest Cr(VI) removal efficiency, followed by PJAC@Fe 2 O 3 and PJAC@ZnO. The maximum removal of Cr 6+ ions at 100 mg L −1 was attained at pH 2.3, 1.5, and 3.3 and a sorbent dose of 2.75 gL −1 for PJAC@CuO, PJAC@Fe 2 O 3 , and PJAC@ZnO, respectively. The ideal contact times of 120 min for PJAC@ZnO, 100 min for PJAC@CuO, and PJAC@Fe 2 O 3 were observed. The isotherm studies reveal adsorption following the Freundlich model (R 2 = 0.856–0.950), indicating heterogeneous and favorable adsorption at low Cr(VI) concentrations. The Dubinin–Radushkevich model confirms a physical adsorption mechanism, with adsorption energies ranging from 9.71 to 13 kJ/mol. Overall, PJAC@CuO showed the best adsorption performance, suggesting that Prosopis juliflora ‐based nanocomposites are effective, sustainable materials for treating Cr(VI)‐contaminated wastewater.