Abstract

Various Zeolitic Imidazolate Frameworks (ZIFs), a unique class of metal organic frameworks (MOFs), were prepared and studied for the removal efficiency against the hazardous azo dye eriochrome black‑T (EBT) from water. Two type of ZIF were synthesized, Co-based (ZIF-67) and Zn-based. For each type, four variations with different morphologies were chosen in order to determine the best performing candidate for the further optimization studies. ZIF-67-OAc showed a superior adsorptive EBT removal efficiency compared to the rest herein studied ZIFs. To statistically model the EBT removal, response surface methodology (RSM) using Box-Behnken design (BBD) technique was followed. According to the model, solution/​suspension pH was found to play the most significant role that govern the rate of EBT adsorption. Under optimized condition, where pH, ZIF-67-OAc dose, mixing time, and EBT concentration set to be 6.82, 832.4 mg/​L, 39.95 min, and 100 mg/​L, respectively, a 99% EBT removal was achieved. The equilibrium data best fitted to Freundlich isotherm model, indicating that the dye molecules accumulate in multilayer on the ZIF-67-OAc surface. Based on the Langmuir isotherm model that was also fitted well (R²=0.95), the qmax was found 263.5 mg/​g. Furthermore, EBT adsorption onto ZIF-67-OAc was descripted better with the pseudo-first order kinetic model.