Periodate activation and pH regulation using ball-milled metal-oxide-mineral-biochar composite for removal of antibiotics from contaminated water

The inclusion of mineral salts in carbon activators are beneficial for advanced oxidation processes (AOPs). Herein, we present the application of ball-milled biochar with phosphate salt for periodate (IO₄⁻) activation and degradation of antibiotics in contaminated water. Physical characterization results showed that the catalyst is infused with Mg₃(PO₄)₂ and ball-milling increased the specific surface area to 216 m² g⁻¹ from 46 m² g⁻¹ while reducing the particle size to less than 1.0 μ. The optimized system successfully eliminated >99% of diclofenac while maintaining the pH of the reaction medium to circumneutral levels. Scavenger and ESR experiments revealed the degradation is triggered by O₂^•–, ¹O₂ and ^•OH species within the system. Electrochemical studies confirmed electron transfer during diclofenac degradation. The reported system demonstrated high degradation efficiency under both neutral and acidic pH conditions. Based on the by-product analysis, the degradation pathway of diclofenac was elucidated. Further, the toxicity assessment for the identified intermediates showed minimum toxicity of the degraded products. This mineral-biochar composite exhibited promising performance in eliminating other antibiotic substances. Therefore, the present finding highlights the importance of raw materials selection for producing mineral-biochar composite that provide new insights into IO₄⁻ activation for antibiotic removal by maintaining the natural pH.