Enhanced removal of phosphate from aqueous solutions by MgAl-LDH impregnated with LaFeO3

Abstract

Water eutrophication, driven by excessive phosphate levels, represents a major environmental challenge. Conventional adsorbents exhibit limitations in efficiently removing phosphate ions (P-ions) from aqueous solutions. This study aimed to develop an MgAl-LDH/LaFeO₃ composite as a more effective adsorbent for P-ion removal. The prepared composite was characterized using various techniques, including XRD, FTIR, SEM, and XPS, to verify its successful fabrication. Zeta potential analysis determined the surface charge to be +32.1 mV at pH 2. Results demonstrated a synergistic effect between LaFeO₃ and MgAl-LDH, which significantly enhanced the composite's overall removal efficiency. The optimal pH for P-ion removal was found to be 2, with a high selectivity for P-ions. Phosphate ion removal followed second-order kinetics and fitted well with both Freundlich and Langmuir isotherms, exhibiting a maximum adsorption capacity of 833.3 mg-P per g. Analyses after adsorption clarified that there was a combination of physical and chemical interactions, including electrostatic attraction, complexation, ion exchange, and ligand exchange, in the removal mechanism. Reusability test showed that the composite maintained over 88% removal efficiency after five cycles, confirming its stability and applicability. These findings highlight the superior adsorption capacity of the MgAl-LDH/LaFeO₃ composite, offering an efficient solution for mitigating phosphate pollution.