Reduced Metal-Codoped TiO2/LSX Zeolite Catalysis: A Sustainable Solution for Crystal Violet Dye Degradation

Abstract

Water pollution due to synthetic dyes such as crystal violet (CV) poses significant environmental and health risks due to its toxicity and persistence. This study investigates the synthesis of titanium dioxide (TiO2) and TiO2/low silica Type X (LSX) zeolite composites using different TiO2 precursor concentrations (0.1, 0.25, 0.5, and 1.0 M) and metal-doped variants (Ag0/TiO2, Ag0–TiO2/LSX, Fe0/TiO2, and Fe0–TiO2/LSX) via sol–gel and borohydride reduction methods. Characterization techniques used are XRD, FTIR, SEM, EDX, BET, TG-DTG, UV–vis spectroscopy, and TEM and HRTEM analysis. Photodegradation has been carried out in the removal of CV dye from aqueous solutions. LSX due to its high surface area (687.408 m2/g) and TiO2 with a high bandgap of 3.2 eV are found most suitable in UV photocatalysis. Metal doping reduced the band gaps, e.g., from 3.2 eV of TiO2 to 2.64 eV of Ag0/TiO2 and 1.91 eV of Fe0/TiO2, enhancing UV-light responsiveness. Batch adsorption and photocatalytic degradation under dark and UV-assisted radiation revealed that Ag0/TiO2 and Fe0/TiO2 photocatalysts showed the highest removal efficiencies of 97.45% and 84.81%, along with adsorption capacities up to 20.98 and 18.26 mg/g, respectively. The comparatively lower performance of TiO2/LSX composites than that of pure TiO2 and pure Na-LSX is attributed to surface coverage by TiO2, which limited the accessibility of active sites. Challenges such as pore blockage, surface coverage, dealumination, and Ag0 and Fe0 agglomeration necessitate further optimization. These findings highlight the potential of Ag0-and Fe0-doped zeolite composites for sustainable wastewater treatment along with future research needed to enhance scalability and real-world applicability.