Adsorption performance of one- and two-component anionic dyes using core-shell ZIF-8@ZIF-67

The discharge of dye wastewater threatens the ecology and biological health. Adsorption technology is the preferred treatment method and absorbent is core. In this study, a high-performance ZIF-8@ZIF-67 adsorbent was synthesized by epitaxial growth . XRD and TEM demonstrated the successful synthesis of the core-shell ZIF-8@ZIF-67 and BET showed that the specific surface area, pore volume and diameter of ZIF-8@ZIF-67 were 1518.75 ​m 2 /g, 0.65 ​cm 3 /g and 1.71 ​nm, respectively, with microporous being the predominant. The optimum adsorption conditions for the adsorption of Direct Blue-86 by ZIF-8@ZIF-67 were an initial concentration of 150 ​mg/g, a ZIF-8@ZIF-67 dosage of 5 ​mg, and a pH of 8, and the adsorption capacity at this condition was 301.69 ​mg/g. The mechanism of adsorption on Direct Blue-86 has been speculated to be electrostatic interaction , hydrogen bonding , Lewis acid-base interaction, π-π stacking and coordination. The kinetics of adsorption of Reactive Yellow and Congo Red in the two-component system were both consistent with the pseudo-second-order kinetic models , with chemisorption being the rate-controlling step and the adsorption rates of Reactive Yellow and Congo Red were both higher than that of one-component system. Meanwhile, they were more consistent with the Langmuir monolayer adsorption models, with maximum adsorption capacities of 261.10 ​mg/g and 291.55 ​mg/g, respectively, a decrease of 56.66% and 54.52% compared to that in the one-component system.