Chitosan/polyvinyl alcohol thin membrane adsorbents modified with zeolitic imidazolate framework (ZIF-8) nanostructures: Batch adsorption and optimization

This study presents the fabrication of zeoliticimidazolate framework (ZIF-8)/chitosan/polyvinyl alcohol composite membrane adsorbents for the removal of malachite green dye from aqueous environment. Synthesis of the nanostructure and its incorporation in the membrane body were approved by scanning electron microscopy, dynamic light scattering, X-ray diffraction, BET and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses. The optimal dye removal (84.55%) was tabulated for the membrane with 1 wt% ZIF-8 in the casting dope. Afterward, batch adsorption conditions were optimized for the membrane containing 1 wt% ZIF-8 using central composite experimental design algorithm. The maximum model-predicted removal percentage was found 97.63% at optimal conditions of adsorbent mass of 0.04 g, initial dye concentration of 29.66 mg/L, pH of 6.1. Re-conducting batch adsorption experiment at the model-predicted optimized conditions approved the validity of the developed model by less than 3% uncertainty. The pseudo-second order model and the Langmuir isotherm were satisfactorily describe the kinetic and the equilibrium of the adsorption, respectively. Fundamental thermodynamic parameters, including ΔH⁰, ΔS⁰, and ΔG⁰ were also determined for the adsorption. The results disclosed endothermic nature, favorability, and spontaneity of the adsorption.