Visible-light enhanced tetracycline degradation via SnO₂/TiO₂-Ni@rGO ternary heterostructures

This study explores the synthesis, characterization, and photocatalytic performance of a SnO₂/TiO₂-Ni@rGO nanocomposite for tetracycline (TC) degradation under visible light irradiation. The nanocomposite was precisely designed to enhance structural stability, charge transfer efficiency, and catalytic activity. X-ray diffraction (XRD) analysis confirmed the structural integrity of the SnO₂/TiO₂-Ni@rGO composite, demonstrating excellent reusability and resistance to photo-corrosion after multiple cycles. Photocatalytic experiments revealed that the SnO₂/TiO₂-Ni@rGO nanocomposite significantly outperformed individual SnO₂/TiO₂-Ni and rGO catalysts, achieving a remarkable 94.6% degradation of TC within 60 min. The degradation process followed pseudo-first-order kinetics, with a rate constant (k) of 0.046 min^-1. The Z-scheme charge transfer mechanism facilitated efficient separation and migration of photogenerated charge carriers, generating reactive oxygen species such as superoxide (•O₂ ^-) and hydroxyl (•OH) radicals crucial for the oxidation of TC. Radical scavenger studies confirmed that superoxide and hydroxyl radicals were the primary active species. The SnO₂/TiO₂-Ni@rGO composite also exhibited excellent reusability, maintaining high catalytic performance over four consecutive cycles. These findings suggest that the SnO₂/TiO₂-Ni@rGO nanocomposite is a promising candidate for the efficient and sustainable photocatalytic degradation of persistent organic pollutants like TC, offering significant potential for environmental remediation applications.