Sustainable Remediation of Chromium(VI) Using a Woollen-Flower-Like Bi₂WO₆/Cellulose Nanocomposite under Solar Irradiation

Extensive utilization of hexavalent chromium Cr(VI) in industries such as electroplating, leather tanning, and dyeing has led to severe environmental pollution. To effectively remove toxic Cr(VI) from wastewater, efficient, nontoxic, sustainable photocatalysts have been fabricated. We designed a hierarchical Bi2WO6/cellulose heterojunction material synthesized via the hydrothermal method. The average crystallite size of bare Bi2WO6 (29.98 nm) was significantly reduced in the Bi2WO6/cellulose composite (19.72 nm), resulting in an increased specific surface area of 28.31 m2/g. SEM analysis revealed a wool-like-flower-shaped morphology for Bi2WO6 and a sheet-like structure for cellulose. The optical band gap energies of Bi2WO6, cellulose, and Bi2WO6/cellulose nanocomposite were determined to be 2.43, 2.68, and 2.98 eV, respectively. Among the prepared samples, the 15% Bi2WO6/cellulose nanocomposite demonstrated exceptional photocatalytic performance, achieving 99.89% reduction of Cr(VI) to Cr(III) within 120 min. The photocatalytic reduction reaction followed a first-order kinetic model with a rate constant (k) of 0.0393 min–1, which was more than two times that of pure Bi2WO6 (0.0148 min–1). Scavenger experiments confirmed that •O2– and e– were the primary active species responsible for Cr(VI) reduction. Furthermore, the photocatalyst retained 90% of its original efficiency after five consecutive cycles, demonstrating excellent stability and recyclability. These findings demonstrate that the Bi2WO6/cellulose nanocomposite is a highly effective photocatalyst for the reduction of toxic Cr(VI) into nontoxic Cr(III) ions. This study also highlights a simple, cost-effective strategy for developing robust semiconductor-based photocatalytic systems for wastewater treatment and environmental remediation.