Recyclable adsorbents based on Fe₃O₄ nanoparticles on lanthanum-modified montmorillonite for the efficient phosphate...

Montmorillonite (MMT) clay modified with lanthanum (La) ions and Fe₃O₄ nanoparticles was proposed for the effective removal of phosphate ions from aqueous solution. Characterisation of the adsorbent using FTIR, SEM, XRD, XPS, XRF, BET and VSM techniques were carried out. The effects of initial phosphate concentration, contact time, dosage and pH on the phosphorus adsorption were investigated. La-MMT/Fe₃O₄ exhibited an excellent adsorption capacity of up to 14.35 mg/g, with 97.8% removal within 60 min. Langmuir isotherm model fits well with the equilibrium isotherm data, with a maximum adsorption capacity of 15.53 mg/g at room temperature. The kinetic study was well fitted with pseudo-second-order kinetics, and the adsorption rate was mainly controlled by liquid-film diffusion. The manufactured adsorbent was effectively regenerated using 0.1 M NaOH solutions, with 90.18% adsorption efficiency remaining after six adsorption/desorption cycles. These results demonstrate that La-MMT/Fe₃O₄ provides an example of regenerable high-performance adsorbents for removal of PO₄^3- from wastewater.