Optimization of the adsorption and removal of Sb(iii) by MIL-53(Fe)/GO using response surface methodology†
In this study, a graphene oxide metal–organic framework (MIL-53(Fe)/GO) composite adsorbent was successfully synthesized using a simple method at room temperature. The specific surface area of the synthesized MIL-53(Fe)/GO nanoparticles was 268.43 m2 g−1, with an average pore size of 2.52 nm. The Box–Behnken response surface method was applied to optimize the adsorption time, dosage, pH, temperature, and initial concentration of Sb(III) in the MIL-53(Fe)/GO adsorption treatment employed for synthetic wastewater containing Sb(III). We determined the optimal adsorption conditions and explored the isotherm model, adsorption kinetic model, and adsorption mechanism during the adsorption process. For an optimal adsorption of Sb(III) by MIL-53(Fe)/GO, the adsorption time, dosage, pH, temperature, and initial Sb(III) concentration should be set to 4.86 h, 85.79 mg L−1, 10.00, 39.29 °C, and 10.09 mg L−1, respectively. Under these optimal conditions, the removal rate of Sb(III) will be as high as 97.97%. The adsorption of Sb(III) by MIL-53(Fe)/GO conformed to the Freundlich isotherm adsorption model, and its maximum adsorption capacity was 69.014 mg g−1. The adsorption kinetics process, which is a nonhomogeneous reaction, could be fitted using a quasi-first-order kinetic model. A Fourier transform infrared spectroscopy analysis showed that MIL-53(Fe)/GO hydroxyl and amine groups play a vital role in the adsorption process. MIL-53(Fe)/GO did not exhibit any changes in its adsorption efficiency in the presence of its anion and showed high specificity to Sb(III). XPS characterization showed that Sb successfully adsorbed onto the adsorbent and that no oxidation–reduction reaction occurred during the adsorption process. The adsorption efficiency remained high even after four cycles of use. MIL-53(Fe)/GO is highly recyclable with significant application potential for treating wastewater containing Sb(III).