Facile fabrication of bioinspired hierarchical porous MOFs for selective adsorption of Congo red and Malachite green from vegetables and fruits juices

Abstract

The dye pollution in environmental water and food caused by industrial production and illegal addition is a serious problem worldwide, which endangers ecosystem, food safety and human health. To effectively overcome these challenges, a magnetic bioinspired hierarchical porous MOFs (BHP-MOFs) based on ZIF-8, Fe3O4 and three-dimensional graphene was successfully prepared for selective adsorption of Congo red (CR) and Malachite green (MG) from aqueous solutions. The surface morphology, physicochemical structure and composition of BHP-MOFs were characterized by SEM, TEM, FT-IR, XRD, Zeta potential, TGA and VSM analysis. The prepared BHP-MOFs exhibited a large specific surface area (225.522 m2/g), high pore volume (0.248 cm 3/g) and superparamagnetism, which made it an efficient adsorbent for fast adsorption of CR and MG. The adsorption kinetics studies showed that the adsorption mechanism of CR and MG followed the pseudo-second model and the adsorption process fitted well to Langmuir isotherm equation. Thermodynamic experiments have shown that the adsorption process is spontaneous and endothermic. The maximum adsorption capacities of CR and MG were 176.06 and 448.43 mg/g, respectively. Under the optimum conditions, BHP-MOFs were successfully used as magnetic adsorbents for the removal of CR and MG in environmental water and fruit juices, with removal efficiency ranged from 97.09% to 76.00%. The reusability of the BHP-MOFs was repeated with seven cycles and removal efficiency remained at 63.01% and 82.20% for CR and MG, respectively. It is proved that BHP-MOFs composite has excellent adsorption capacity for dyes and has a wide application prospect in practical applications.