Efficient degradation of diclofenac sodium by periodate activation using Fe/Cu bimetallic modified sewage sludge biochar/UV system

Highlights: • Fe/Cu-SBC was fabricated and utilized in heterogeneous PI oxidation process. • 46.7% TOC and 99.7% DCF removal were obtained under Fe/Cu-SBC/UV/PI system. • Synergistic effect of UV and Fe/Cu-SBC promotes the circulation of iron. • The electron transport system was greatly improved by the Fe/Cu bimetallic system. Iron/copper bimetallic nanoparticles based sludge biochar (Fe/Cu-SBC) was prepared by using a modified co-precipitation route. The Fe/Cu-SBC system prepared was subsequently applied to activate periodate (IO₄⁻) to degrade diclofenac sodium (DCF) by using UV light at room temperature (25 °C). The physicochemical properties of both SBC and Fe/Cu-SBC such as morphology, physical properties, crystal structures and functional groups were examined. The type and number of surface functional groups were found to be increased and the catalytic performance was improved by the modification of Fe/Cu bimetallic nanoparticles. The influence of various parameters to evaluate the catalytic efficiency such as periodate (PI) concentration, dosage of catalysts, UV power, initial pH and coexisting anions were investigated. Under the optimized conditions (pH 6.9, UV-power 60 W, PI concentration of 5 mM and 0.1 g Fe/Cu-SBC), it was observed that 99.7% of DCF was degraded with a pseudo-first-order kinetics reaction constant 9.39 × 10⁻² min⁻¹. The radical scavenging experiments showed that IO₃ radicals were the predominantly reactive oxidants in the Fe/Cu-SBC/UV system. Therefore, this investigation provides a feasible alternative for the degradation of PPCPs in wastewater.