Tailoring of surface and electronic structure of Sm³⁺-substituted Mn-Co spinel ferrites for magnetically separable and visible light driven multi-pollutant degradation

Antibiotic contamination in water requires photocatalysts that are active under visible light and can be easily recovered after use. Samarium-substituted Mn-Co spinel ferrites are reported as magnetically separable photocatalysts, with emphasis on their cation distribution and lattice bonding. A key novelty is the combined analysis of XRD intensity, XPS, and electron density distribution, which confirms the preferential presence of Sm³⁺ ions at octahedral B sites by replacing Fe³⁺. The structural analysis shows that Sm³⁺ substitution strengthens the A-O covalent bonds and gradually increases the covalent character of the B-O bonds. Optical analysis confirmed that 20 % Sm³⁺ ferrite has strong and two-fold light absorption compared to 10 % sample and reduced bandgap useful for charge separation. HRTEM analysis indicated a better crystallinity at higher Sm³⁺ levels. The 20 % of Sm³⁺ ferrite photodegraded Tetracycline by 98.1 % in 100 min, Norfloxacin, and Ciprofloxacin by 97.1 %, and 92.51 % within 120 min. The incorporation of Sm³⁺ adds localized 4f states, boosting light absorption, aiding charge separation, and strengthening crystallinity. This allows the ferrites to breakdown antibiotics effectively under visible light, mainly through hydroxyl radicals. They also retain magnetic properties, making recovery simple, and combine strong photocatalytic performance with practical reusability.