Facile Fabrication of ZIF-8/Calcium Alginate Microparticles for Highly Efficient Adsorption of Pb(II) from Aqueous Solutions

Metal–organic frameworks (MOFs) have received special attention from scientists owing to their excellent adsorption performance. However, the difficulty in separating MOFs from adsorbed metals following use has limited their application. A zeolitic imidazole-based MOF with broad applicability for sorption of Pb(II) is examined. In this work, a novel adsorbent employing ZIF-8/calcium alginate microparticles was prepared using sodium alginate and ZIF-8. This adsorbent was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The performance of the ZIF-8@CA microparticles in adsorbing Pb(II) from a Pb(II) solution was investigated, and the impacts of the initial Pb(II) concentration, reaction time, pH, and reaction temperature on the reaction process were investigated. The results showed that ZIF-8@CA microparticles exhibited a maximum adsorption capacity of 1321.21 mg/g at pH 5 after 120 min, and the adsorption process was found to fit the Langmuir isotherm model (R2 = 0.9856) and the pseudo-second-order kinetic model (R2 = 0.9999). These results showed that the adsorption of Pb(II) was an endothermic process. The regeneration experiment with ZIF-8@CA revealed that the removal efficiency of Pb(II) was greater than 80% even after five cycles.