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Magnetic zirconium-based metal–organic frameworks for selective phosphate adsorption from water
- Liu, Tao, Zheng, Shourong, Yang, Liuyan
- Journal of colloid and interface science 2019 v.552 pp. 134-141
- adsorbents, adsorption, anions, carbon, chlorides, coordination polymers, humic acids, iron oxides, magnetic fields, nitrates, pH, phosphates, sodium hydroxide, sorption isotherms, sulfates, temperature, zirconium
- Although adsorbents can effectively remove phosphate from water, most are difficult to separate from water and their phosphate removal efficiencies are adversely affected by coexisting anions or humic acid. Here, a magnetic core–shell composite with Fe3O4 as the core and carbon as the shell (denoted as MFC) was functionalized with a metal–organic framework, UiO-66, and its phosphate adsorption ability was studied. The composite (denoted as MFC@UiO-66) was effectively separated from water within 1 min under an external magnetic field. The kinetics of phosphate adsorption onto MFC@UiO-66 was controlled by the intraparticle diffusion process, suggesting that the Zr in UiO-66 played an important role in phosphate adsorption. The isotherm for phosphate adsorption onto MFC@UiO-66 was well described by the Freundlich model. The adsorbent exhibited higher affinity toward phosphate than toward coexisting anions (e.g., Cl−, NO3−, and SO42−), reflecting high phosphate adsorption selectivity. The adsorption affinity of MFC@UiO-66 to phosphate increased with the increasing temperature, but decreased with increasing pH. The presence of dissolved humic acid negligibly affected phosphate adsorption onto MFC@UiO-66 because of its size-exclusion effects. The used adsorbent was easily regenerated with NaOH solution, and the sorbent displayed stable phosphate adsorption behavior after five regeneration cycles.