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

Abstract

Metal–organic\nframeworks (MOFs) have received special attention\nfrom scientists owing to their excellent adsorption performance. However,\nthe difficulty in separating MOFs from adsorbed metals following use\nhas limited their application. A zeolitic imidazole-based MOF with\nbroad applicability for sorption of Pb­(II) is examined. In this work, a novel adsorbent employing ZIF-8/calcium\nalginate microparticles was prepared using sodium alginate and ZIF-8.\nThis adsorbent was characterized using scanning electron microscopy,\nFourier-transform infrared spectroscopy, X-ray diffraction analysis,\nand X-ray photoelectron spectroscopy. The performance of the ZIF-8@CA\nmicroparticles in adsorbing Pb­(II) from a Pb­(II) solution was investigated,\nand the impacts of the initial Pb­(II) concentration, reaction time,\npH, and reaction temperature on the reaction process were investigated.\nThe results showed that ZIF-8@CA microparticles exhibited a maximum\nadsorption capacity of 1321.21 mg/g at pH 5 after 120 min, and the\nadsorption process was found to fit the Langmuir isotherm model (<i>R</i>² = 0.9856) and the pseudo-second-order kinetic\nmodel (<i>R</i>² = 0.9999). These results showed\nthat the adsorption of Pb­(II) was an endothermic process. The regeneration\nexperiment with ZIF-8@CA revealed that the removal efficiency of Pb­(II)\nwas greater than 80% even after five cycles.