Photochemical reduction and selective recovery of Cr(VI) from electroplating wastewater by starch biomass

Hexavalent chromium (Cr(VI)) is a hazardous and mobile contaminant noted for its severe environmental impacts. This research presents a low-cost, efficient, and eco-friendly method that utilizes starch extracted from Maranta arundinacea (arrowroot) for the selective recovery and discarding of chromium (VI) from electroplating effluents driven by a visible light photochemical procedure. This method alleviates the transition of harmful and toxic Cr(VI) into the less toxic and more stabilized trivalent chromium (Cr(III)), which eventually forms firm coordination complexes with the arrowroot starch along with functional groups such as hydroxyl groups ( OH) and ether groups (C O C), as verified by FTIR and XPS analyses. Noticeable structural alteration in the starch matrix was observed upon interaction with chromium ions. At pH 3.0, the process achieved a maximum removal limit of 98.3 %, but at pH 10.0, the efficiency decreased markedly to 3.2 %. Additionally, within the tested concentration range of 10–50 mg/L, the extraction efficiency remained at or above 90 %. In the presence of competing ions such as Ca, Cu, Zn, and Ni, chromium was selectively removed. Furthermore, when the starch dosage was increased from 50 mg to 450 mg, the efficiency was enhanced by approximately 55 % to nearly 95 %. This increase in dosage promoted the faster reduction within 300 min. The entire approach is environmentally benign, generating no secondary waste, and thus making it a viable and sustainable option for industrial-scale wastewater treatment. These results demonstrate the potential value of arrowroot starch as an efficient material for sustainable and economical chromium remediation. • Starch-derived adsorbent was engineered for efficient photochemical reduction of Cr(VI) into Cr(III). • Oxygen content and pH-dependent surface chemistry enhanced the adsorption performance of arrowroot starch • Surface hydroxyl functionalities acted as principal sites for Cr(VI) coordination and redox transformation. • Pyrolysis of Cr-loaded starch biomass enabled selective recovery of bound chromium. • A sustainable and low-cost strategy for the remediation of Cr(VI) from electroplating wastewater was proposed.