Facile preparation of water-soluble titanium citrate with highly efficient quasi-homogeneous photocatalytic reduction of Cr(vi)

Abstract

A titanium citrate photocatalyst with high photocatalytic activity was prepared using the gel method. It exhibited complete water solubility, maintained stability without gelation or precipitation over a short period, and allowed photocatalysis under quasi-uniform conditions. The structural properties of titanium citrate were analyzed through various characterization techniques, including single-crystal X-ray diffraction (XRD), ¹H, ¹³C nuclear magnetic resonance, and Raman spectroscopy. The single-crystal XRD data revealed the molecular structure of titanium citrate as Ti₈O₁₀(C₆H₅O₇)₄–(H₂O)₁₂·H₂O and the internal structure as Ti₈O₁₀. The photocatalytic performance was assessed using Cr(VI) as the target pollutant, evaluating parameters such as catalyst loading (0.4–1.6 g L⁻¹), initial concentration (20–150 mg L⁻¹), pH (2–6), and the influence of anions. At a catalyst dosage of 0.6 g L⁻¹, the reduction rate of 100 mg L⁻¹ Cr(VI) reached 100% within 40 min of light illumination. Active species trapping and free radical detection demonstrated that photogenerated electrons (e⁻) and •O₂⁻ primarily facilitated the Cr(VI) reduction process. Multiple pathways were studied for the reduction of Cr(VI). This study provides a novel approach for designing efficient and quasi-homogeneous photocatalytic reduction systems for Cr(VI) removal in future research.