Adsorptive removal of Cr(VI) from simulated wastewater in MOF BUC-17 ultrafine powder

Abstract

A water-stable metal-organic framework [Co3(tib)2(H2O)12](SO4)3 (BUC-17) with 2D graphene-like crystal structure was tuned to produce ultrafine powder via the introduction of absolute ethanol. The BUC-17 powders were further characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Zeta potential analysis. The BUC-17 ultrafine powder exhibited excellent adsorption performance toward Cr(VI) from simulated wastewater, in which the maximum uptake capacity is 121 mg g−1 at pH = 4. The kinetics fitting results revealed that the adsorption process is more suitably described by the pseudo-second-order kinetics model. The negative standard free energy change ΔG°, positive enthalpy change ΔH°, and positive entropy change ΔS° of the adsorption process implied that the adsorption between BUC-17 and Cr(VI) was spontaneous and endothermal. As well, the influencing factors of the adsorption process like pH, adsorbent dosage, initial concentration and foreign ions were investigated. Finally, the adsorption mechanism of BUC-17 toward Cr(VI) was proposed.