Preparation and practical applications of a phosphate capture material with FeO(OH)-loaded polyurethane†

Metal (hydro)oxide particles with efficient phosphate removal properties are widely used in the treatment of eutrophic waters (mainly phosphorus). However, the disadvantages of easy agglomeration and difficult separation limit their application. In this study, a polyurethane sponge (PU) was coated with sodium carboxymethyl cellulose (CMC-Na) to anchor FeO(OH) to prepare a novel functional composite (CFe@PU), which overcame the disadvantages of metal (hydro)oxide particles. The results revealed that the coating process of CMC-Na on the PU surface contributed to loading of FeO(OH) and enhanced the affinity for phosphate. The maximum adsorption capacity of CFe@PU was 21.22 mg phosphate-P per g, which was 1.74 times that of Fe@PU, and the effect of the coating process was significant (P = 0.01). The material displayed remarkable selectivity when exposed to a diverse array of anions and within the pH range of 4–8. The phosphorus removal efficiency by CFe@PU was >71.34% after three regeneration cycles. Investigating the adsorption mechanisms revealed that electrostatic attraction and inner-sphere ligand exchange were involved in the adsorption process. In a lake water experiment, the phosphorus in the CFe@PU treated group decreased from 0.2 mg L⁻¹ to 0.004 mg L⁻¹, limiting algae growth significantly. These results indicated that CFe@PU was a potential adsorbent in controlling eutrophication.