Synergistic removal of mixed methyl orange/sunset yellow solution by the graded ZnCrNi-LDHs porous material

Layered bimetallic hydroxide (LDHs) nanomaterials have shown excellent potential in the field of recovery of pollutants from wastewater through anion exchange and surface electrostatic interaction. In this paper, three new ternary ZnCrNi-LDHs with the different graded porous were successfully prepared by controlling the morphology of the layer stacking using triethanolamine as the soft-template, and characterized by SEM, TEM, XPS, TG, BET and XRD. The ZnCrNi-LDHs exhibited higher adsorption capacity for pollutants such as methyl orange, sunset yellow and their mixed solutions. The results showed that there was a good synergistic adsorption effect in the adsorption process of mixed solutions. The maximum adsorption amounts of single methyl orange, sunset yellow, and mixed solutions of methyl orange and sunset yellow were 1834.63 mg·g-1, 1259.79 mg·g-1, 3270.59 mg·g-1 and 3294.38 mg·g-1, which shows that the adsorption amounts about synergistic adsorption effect for mixed solutions is much higher than those of single methyl orange and sunset yellow; Meanwhile, the maximum adsorption capacity is higher than most adsorbents. The pseudo-second-order kinetic model fitted the kinetic data of adsorption, while the equilibrium adsorption isotherm data followed the Freundlich model. The adsorption process contains both surface adsorption and interlayer anion exchange as determined by SEM, XRD, IR and zeta potential analysis. The research not only demonstrates that three ZnCrNi-LDHs materials showed excellent adsorption performance and practical interest as an efficient adsorbent for the removal of methyl orange, sunset yellow, and mixed solutions but also provides a strategy for the removal of mixed dye solutions.