Removal of Cr(VI) from Water by Using Schwertmannite-Loaded Lignocellulose Beads from Sugarcane Bagasse

Biosorption is considered a promising method for removing heavy metals from polluted water, benefiting from their abundance, low cost, and environmental friendliness. However, its practical application for Cr(VI) removal was limited, as the biosorbents often lack uniform size or a stable morphology, and Cr(VI) oxidation can destroy active adsorption groups. In this study, lignocellulose beads (LCB) with uniform size (similar to 2 mm) were prepared from sugarcane bagasse using ionic liquids. Additionally, an inorganic structure Schwertmannite (ScH) was synthesized and loaded on LCB, creating permanent active sites for adsorbing Cr(VI) anions. Characterization studies confirmed that ScH@LCB adsorbent possesses excellent properties, such as homogeneous and stable morphology. Batch experiments indicated that the adsorption isotherms confirmed well with Langmuir model, with the maximum adsorption of Cr(VI) of 24.62 mg/g. The linear correlation between the released SO42- and CrO42- adsorption was 0.94, suggesting that the anion-exchange reactions primarily determines the adsorption of Cr(VI) on ScH@LCB. Furthermore, several desorption and regeneration experiments demonstrated that ScH@LCB maintains stable adsorption performance.