Novel hollow beads of carboxymethyl cellulose/ZSM-5/ZIF-8 for dye removal from aqueous solution in batch and continuous fixed bed systems

Abstract

Zeolitic imidazolate frameworks are a class of metal-organic frameworks that are topologically isomorphic with zeolites. In this study, bionanocomposites of carboxymethyl cellulose-based ZSM-5/zeolitic imidazolate framework (CMC/ZSM-5/ZIF-8) hollow beads with different compositions were synthesized and employed as an adsorbent for methylene blue removal from aqueous solution in batch and continuous fixed bed systems. FESEM, FTIR, XRD, and BET measurements have been employed for characterizing the synthetic bionanocomposites. The effect of time and concentration on adsorption processes, regeneration, and reuse investigations were performed. The equilibrium batch adsorption capacities for CMC, CMC/ZIF-8, CMC/ZSM-5, and CMC/ZSM-5/ZIF-8 adsorbents were 12.01, 13.06, 11.53, and 10.49 mg/g, respectively. The batch adsorption was investigated using pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich kinetic models and the results showed that all four adsorbents are consistent with all models but the pseudo-first-order model showed more consistency. The equilibrium continuous adsorption capacities for CMC, CMC/ZIF-8, CMC/ZSM-5, and CMC/ZSM-5/ZIF-8 adsorbents were 10.56, 11.87, 9.29, and 8.15 mg/g, respectively. The continuous adsorption was investigated by Thomas, Adam-Bohart, Yoon-Nelson, Wolborska, and Modified Dose Response kinetic models and the results showed that the adsorbents showed more consistency with models of Thomas, Yoon-Nelson, and Modified Dose Response. Besides, the generation process was successfully assessed in five steps.