MOF-based polymeric nanocomposite beads as an efficient adsorbent for wastewater treatment in batch and continuous systems: Modelling and experiment

Herein, a novel polymeric nanocomposite based on zeolitic imidazolate frameworks (ZIFs) was synthesized through a facile one step phase inversion (PI) technique. The prepared PES/ZIF-8/ZIF-67 was employed to remove Malachite green (MG) dye from colored wastewater in both batch and continuous flow systems. The influence of different parameters such as adsorbent dosage, initial MG concentration and solution pH were investigated and the results indicated that the pure PES beads had negligible adsorption, while compositing of this polymer with ZIFs particles removed 99.2% of MG molecules with a significant adsorption capacity (613.2 mg/g). Aromatic-aromatic interactions (pi-pi stacking) between the rings of imidazole ligand and MG dye was dominant adsorption mechanism. Kinetics and equilibrium isotherms studies revealed that batch adsorption experiment followed pseudo-second order and Langmuir models, respectively. In addition, the continuous separation process was evaluated and the breakthrough curves (BTCs) proposed that the longest breakthrough time could be attained within 12 mg/L of inlet MG concentration, 6 cm of fixed bed height and 1 mL/min of flow rate. Several well-known models including Thomas, Bed Depth Service Time (BDST), Adams-Bohart and Yoon-Nelson models were employed to correlate the experimental data obtained from the fixed bed adsorption setup. Moreover, continuous flow adsorption was simulated using Aspen Adsorption (TM) software which can solve the governing differential equations and provide useful information for designing and scaling up the adsorption process to the industrial levels. Consequently, the PES/ZIF-8/ZIF-67 beads with a high adsorption performance have a good application potential for eliminating organic contaminates from wastewater.