A novel lanthanum carbonate for low-level phosphorus removal: Adsorption performance and mechanism

The low-level phosphorus (P) removal is increasingly becoming a challenge for P pollution control and prevention. Adsorption is a highly efficient method for achieving low-level P removal. The development of adsorbents with a strong affinity towards P and the study of limiting factors affecting low-level P removal are currently of primary importance. In this study, lanthanum carbonates (LCs) synthesized at different temperatures, designated as LC-80, LC-90 and LC-100, were compared. It was found that the synthesis temperature determined the La species and thus the ion exchange capacity, which further affected the P adsorption capacity of the LCs at low P concentrations. LC-80 and LC-90 were novel LC species (La2O(CO3)2), exhibiting a higher ion exchange capacity. They combined with P through ion exchange to form inner-sphere complexes. LC-100, which was determined as LaCO3(OH), exhibited a lower ion exchange capacity and adsorbed P anions through ion exchange and electrostatic attraction. Moreover, LC-80 and LC-90 displayed greater resistance to pH and co-existing ions, with LC-100 being more susceptible to their negative effects. A five-cycle regeneration operation demonstrated the good recyclability and reusability of LCs. In particular, LC-90 showed the highest P adsorption capacity at low P concentrations due to its strong ion exchange capacity. This remarkable performance allowed LC-90 to achieve an ultra-low P concentration at a lower cost of 283.12 $/kg P, thus making it a promising adsorbent for low-level P removal.

Automated summary

The synthesis temperature of lanthanum carbonates (LCs) affects their ion exchange capacity and P adsorption capacity at low concentrations. LC-80 and LC-90 are novel LC species with higher ion exchange capacity and form inner-sphere complexes with P through ion exchange. LC-100 has lower ion exchange capacity and adsorbs P through ion exchange and electrostatic attraction. The resistance to pH and co-existing ions is greater for LC-80 and LC-90, while LC-100 is more susceptible. A five-cycle regeneration operation demonstrates the recyclability and reusability of LCs, with LC-90 showing the highest P adsorption capacity at low concentrations. The cost-effective performance of LC-90 makes it a promising adsorbent for low-level P removal. Overall rating: 8.5/10.