Optimization of solvothermal synthesis parameters for Bi24O31Cl10: Enhanced photocatalytic performance, degradation pathways, and mechanism of organic pollutants

This study aims to optimize the synthesis parameters of Bi₂₄O₃₁Cl₁₀ to enhance its photocatalytic efficiency for dyes degradation in aqueous media. Bi₂₄O₃₁Cl₁₀ particles were synthesized through a two-step process: solvothermal treatment at varying temperatures (160 °C, 180 °C, 200 °C) and times (12 h, 16 h, 20 h), followed by thermal treatment at 500 °C for 4 h. The influence of pH was also examined. The samples, denoted as Bi₂₄-T-t, were characterized using XRD, SEM, Raman spectroscopy, DRS, and BET analysis to determine their structural, morphological, and optical properties. The optimal sample, Bi₂₄-160-12, synthesized at 160 °C for 12 h with unadjusted pH, achieved a remarkable 99.98 % degradation of Rhodamine B within 50 min under visible light. High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses confirmed molecular decomposition through progressive deethylation and xanthene ring cleavage, leading to mineralization into CO₂ and H₂O. Active species trapping experiments highlighted the roles of superoxide radicals (∙O₂⁻) and photogenerated holes (h⁺) in the degradation mechanism. Bi₂₄-160-12 exhibited excellent stability, maintaining high efficiency over multiple cycles while retaining its crystalline structure. Additionally, its photocatalytic performance was evaluated for the degradation of the pesticide Imazalil under UV light, demonstrating its versatility for treating persistent organic pollutants. These findings underscore the significance of optimizing synthesis parameters to enhance material properties, positioning Bi₂₄O₃₁Cl₁₀ as a promising photocatalyst for water treatment applications.