Efficient phosphate capture of Fe3O4/UiO-66-NH2/CeO2 in wide pH spectrum

Eutrophication has long been one of the environmental pollution problems, and excess phosphate in water bodies is the main cause of this phenomenon. To solve this problem, magnetic adsorbent with Fe/Ce-loaded zirconiumbased metal-organic framework (Fe3O4/UiO-66-NH2/CeO2) was prepared by co-precipitation, microwave assisted and hydrothermal method. The results showed that different molar ratios of cerium and zirconium were the main influencing factors for phosphate adsorption, and the adsorbent exerted its maximum capturing capacity of 260.8 mg/g of phosphate when Ce:Zr = 4:1. The newly synthesized Fe3O4/UiO-66-NH2/CeO2 was characterized by SEM, XRD, FT-IR, XPS, VSM and TGA. The adsorption process was found to be consistent with the Langmuir adsorption isotherm model and the pseudo-second-order model by batch experiments, indicating that the monolayer chemisorption dominated the adsorption process. Thermodynamic parameters obtained from temperature experiments proved that the phosphate adsorption process is a spontaneous endothermic absorption process and the adsorption experiments with coexisting ions (F-, Cl-, NO3- , SO42-, HCO3- ) showed that the adsorbent has a unique selectivity for phosphate. Unlike most adsorbents previously studied, Fe3O4/UiO-66NH2/CeO2 exhibited consistently efficient adsorption performance over the pH spectrum tested (2 < pH < 10). After five cycles, the adsorbent still maintained favourable adsorption performance. Mechanism of Fe3O4/UiO66-NH2/CeO2 adsorption on phosphate was attributed to electrostatic attraction, ligand exchange and innersphere complexation. Therefore, the prepared Fe3O4/UiO-66-NH2/CeO2 with wide pH suitability will be a promising option for capturing phosphate from wastewater.