Ascorbic acid/Fe⁰ composites as an effective persulfate activator for improving the degradation of rhodamine B

An ascorbic acid/Fe⁰ composite (H₂A/Fe⁰)-activated persulfate (PS) process was provided for rhodamine B (RhB) removal. Experimental results demonstrated that the H₂A/Fe⁰-PS system exhibits a rapid and continuous oxidation of organic contaminants, and shows great advantages over the conventional Fe⁰-PS system by significantly improving removal efficiency. This H₂A induced dramatic enhancement for RhB degradation could be attributed to both the reduction and chelating ability of H₂A. The H₂A/Fe⁰ composites were characterized using TEM, FE-SEM, FTIR and XPS, indicating that the obtained H₂A/Fe⁰ composites were prepared successfully. Key factors affecting the treatment were determined for the H₂A/Fe⁰-PS system, including H₂A/Fe⁰ dosage, PS dosage, initial solution pH and temperature. Moreover, radical quenching tests revealed that sulfate radicals (SO₄˙^-), hydroxyl radicals (˙OH) and superoxide radicals (O₂˙^-) were generated in the H₂A/Fe⁰-PS system, and SO₄˙^- was the main radical species responsible for RhB degradation. Finally, possible degradation pathways are proposed. These findings prove that the H₂A/Fe⁰-PS system may provide a simple and effective technology for improving the degradation of refractory organic pollutants.