Phosphate recovery through the redox cycling process using cerium-based adsorbents: High capacity and high stability

The application of various surface-modified and nano-sized metal-based adsorbents has demonstrated impressive efficiency in phosphate recovery and reuse. However, current research predominantly focuses on the material properties and phosphate adsorption efficiency, often overlooking methods to optimize the phosphate adsorption process. In this research, we introduce a strategy to enhance phosphate removal by modulating the valence state of cerium hydroxide nanoparticles (CHN) through a redox process. Using a simple reduction method with vitamin C, the Ce(III) content and surface hydroxyl groups increased significantly in CHN, resulting in a substantial improvement in phosphate adsorption. The maximum adsorption capacity of vitamin C-treated cerium hydroxide nanoparticles (VC-CHN) reached 113.4 mg P g⁻¹ , 2.2 times higher than untreated CHN. Furthermore, adding a small amount of persulfate (PDS) to the alkaline desorption solution significantly optimized the phosphate desorption process, effectively mitigating the inhibition caused by natural organic matter (NOM). This redox modulation strategy allowed the CHN adsorbent to maintain excellent reusability in natural water containing complex chemical species. Therefore, modulating redox processes offers a novel and effective approach for removing and recovering phosphate using metal oxide adsorbents.