Recyclable adsorbents of iron and lanthanum co-modified clam shells for phosphorus removal from domestic sewage: characterization and mechanisms

This research focused on creating a recyclable magnetic adsorbent, termed La@Fe-CCS, which was modified with lanthanum (La) to improve its efficiency in removing phosphate. The process involved integrating lanthanum into an iron (Fe)-based clam shell matrix (Fe-CCS). This study showed that La@Fe-CCS demonstrated superior adsorption capabilities within a pH range of 3-8 compared to Fe-CCS. Coexisting ions and humic acid (HA) had limited effects. La@Fe-CCS also exhibited rapid adsorption kinetics, achieving equilibrium within 20 min. It showed a theoretical maximum adsorption capacity of 43.61 mg/g, which was substantially higher than that of Fe-CCS (5.79 mg/g). XPS and FTIR analyses indicated that phosphate removal by La@Fe-CCS involves ligand exchange between surface hydroxyl groups and phosphate, as well as intrasphere complexation. In real domestic sewage, La@Fe-CCS achieved over 95% total phosphorus (P) removal. These results suggest that La@Fe-CCS is a highly efficient adsorbent for practical P remediation applications.