Simultaneous removal of various organic dyes from aqueous solutions using a UiO-67-type metal-organic framework

Water pollution has become increasingly critical with recent economic and industrial developments. Highly efficient methods are required to remove diverse pollutants in factory and domestic wastewater. For efficient wastewater treatment, the removal of various compounds in a single step is desirable. In this study, the adsorption characteristics of UiO-67 were evaluated using four organic dye compounds with different molecular sizes and electrostatic properties, i.e., methylene blue, rhodamine B, methyl orange, and Acid Red 52. UiO-67 showed high adsorption capacity for the four organic dye compounds regardless of ionicity or molecular size. Further, the equilibrium analysis revealed that not only methylene blue and methyl orange but also rhodamine B and Acid Red 52 with large molecular sizes were adsorbed in the pores (main adsorption sites) of UiO-67. The recycling resistance of UiO-67 was studied using a mixture of methylene blue and methyl orange, and UiO-67 was found to exhibit high adsorption capacity for both methylene blue and methyl orange even after four times of recycling. Therefore, UiO-67 is a promising adsorbent that can simultaneously remove compounds with different ionicities and molecular sizes.