Efficient removal of EDTA-Cu by a novel Green Fe-Ca-Al composite metal material coupled with NaClO.

The effective and economical removal of heavy metal-organic complexes remain an urgent challenge in the field of industrial wastewater treatment. In this study, Ca-doped ferrihydrite composites and Ca/Al co-doped ferrihydrite composites were synthesized via a simple one-step co-precipitation method and applied for the oxidative removal of EDTA-Cu in a hypochlorite system. The incorporation of Al significantly enhanced the material's stability. The Fe-Ca-Al composite exhibited a catalytic degradation efficiency of 97 % after 4 reaction cycles, representing a 32 % improvement compared to the Ca-doped ferrihydrite (Fe-Ca). Mechanistic studies revealed that the Fe-Ca-Al composite demonstrated strong selective adsorption of the organic moieties in EDTA-Cu over a broad pH range. Moreover, the oxygen vacancies (Ov) induced by Ca and Al co-doping played a crucial role in the enhanced catalytic performance and efficient removal of EDTA-Cu. These abundant Ov promoted electron transfer and provided numerous surface adsorption sites, facilitating the conversion of O2·- to 1O2. Given that 1O2 can rapidly degrade organic compounds containing amino and carboxyl groups, it shows excellent potential for the treatment of EDTA-Cu. This study presents a highly active and reusable catalyst based on a Ca-Al doping strategy, offering a promising approach for the removal of organic-heavy metal complexes.