Removal of Phosphate by Adsorption with 2-Phenylimidazole-Modified Porous ZIF-8: Powder and Chitosan Spheres

[Image: see text] Due to rapid socioeconomic development, increased phosphorus concentrations can cause eutrophication of water bodies, with devastating effects on environmental sustainability and aquatic ecosystems. In this study, ZIF-8-PhIm was prepared for phosphorus removal using 2-phenylimidazole via the solvent-assisted ligand exchange (SALE) method. The structure and composition of ZIF-8-PhIm were characterized by various methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), (1)H nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis. Compared to the ZIF-8 material, it exhibited a multistage pore structure with larger pore capacity and pore size, increased hydrophilicity, exposure of more adsorption sites, and also stronger electrostatic interaction. Under optimized conditions (T = 298 K, C(0) = 150 mg/L, dose = 0.2 g/L), the adsorption capacity of ZIF-8-PhIm reached 162.93 mg/g, which was greater than that of the ZIF-8 material (92.07 mg/g). The Langmuir isotherm and pseudo-second-order kinetic models were suitable for describing the phosphate adsorption of ZIF-8-PhIm. The main effects of ZIF-8-PhIm on phosphate adsorption were Zn–O–P bonding and electrostatic interactions. It also had good regeneration properties. The ZIF-8-PhIm/CS spheres were prepared using chitosan (CS) as the cross-linking agent. The results of dynamic adsorption experiments on the spheres showed a saturation capacity of 85.69 mg/g and a half-penetration time of 514.15 min at 318 K according to the fitted results.