Sodium Alginate/UiO-66-NH₂ Nanocomposite for Phosphate Removal

Environmental pollution of phosphorus is becoming increasingly concerning, and phosphate removal from water has become an important issue for controlling eutrophication. Modified metal-organic framework (MOF) materials, such as UiO-66-NH₂, are promising adsorbents for phosphate removal in aquatic environments due to their high specific surface area, high porosity, and open active metal sites. In this study, a millimeter-sized alginate/UiO-66-NH₂ composite hydrogel modified by polyethyleneimine (UiO-66-NH₂/SA@PEI) was prepared. The entrapping of UiO-66-NH₂ in the alginate microspheres and its modification with PEI facilitate easy separation in addition to enhanced adsorption properties. The materials were characterized by SEM, FTIR, XRD, and BET. Static, dynamic, and cyclic adsorption experiments were conducted under different pH, temperature, adsorbent dosage, and initial concentration conditions to assess the phosphate adsorption ability of UiO-66-NH₂/SA@PEI. Under optimal conditions of 65 °C and pH = 2, 0.05 g UiO-66-NH₂/SA@PEI adsorbed 68.75 mg/g, and the adsorption rate remained at 99% after five cycles of UiO-66-NH₂/SA@PEI. These results suggest that UiO-66-NH₂/SA@PEI composite materials can be used as an effective adsorbent for phosphate removal from wastewater.