Synthesis of ZIF-8/GO for the Removal of Congo Red From Wastewater With a High Salt Concentration

Graphical In this study, the ZIF-8/GO composite was successfully prepared by the one-pot method and applied to the highly efficient removal of CR from high-concentration saline wastewater. The maximum removal ratio was up to 98%. Meanwhile, it was revealed that the removal of CR by ZIF-8/GO depended on hydrogen bonding, electrostatic interaction, and π-π stacking. Dye wastewater is high-concentration salt-containing chemical wastewater. It contains numerous toxic pollutants that are difficult to degrade, and its direct discharge without treatment will cause serious environmental problems. Herein, ZIF-8/GO adsorbent was prepared by the one-pot method to purify wastewater containing Congo red dye (CR). ZIF-8/GO possessed an S BET of 70.252 m 2 /g, pore volume of 0.036 cm 3 /g, and pore size of 3.22 nm. Adsorption experiments of ZIF-8/GO were performed based on various parameters, such as pH, concentration, dose, temperature, and salt concentration. The results showed that the adsorption capacity of ZIF-8/GO was better than ZIF-8 and GO for CR, which the adsorption process of 0.1-ZIF-8/GO (10.0 mg) for CR (50 mg/L) reached equilibrium in 60 min at 35 °C under the high-salt parameter (10 g/L NaCl). And the maximum removal ratio was up to 98%. Adsorption data were fitted using the Langmuir, and Freundlich isotherm models and pseudo-first-order, pseudo-second-order kinetics model and liquid film diffusion model, intra-particle diffusion model. The results indicated that the quasi-second-order kinetic model and Freundlich model were more suitable to describe the adsorption process for the removal of CR by ZIF-8/GO. ZIF-8/GO possesses a high removal ratio and it has promising applications in high-concentration salts-containing wastewater.