Hierarchical hollow copper hydroxide nitrate derived from ZIF-67 for efficiency adsorption of tetracycline and methyl orange

Abstract

A novel hierarchical hollow copper hydroxide nitrate (Cu2(OH)3NO3) was synthesized using Zeolitic Imidazolate Framework −67 (ZIF-67) as a template and then etched with copper nitrate at room temperature. The material was employed as an adsorbent to remove tetracycline (TC) and methyl orange (MO) pollutants from water. The amount of copper nitrate used affects the resulting products. When a small amount of copper nitrate is used, the ZIF-67 cannot be etched completely, whereas a large amount damages the frame of ZIF-67. The adsorption kinetics and isotherms were found to be well-fitted by the pseudo-second-order and Langmuir models for both pollutants. Adsorption thermodynamics studies have demonstrated that both adsorption processes are spontaneous, endothermic, and entropy-increasing. The maximum adsorption capacities obtained from the Langmuir model were up to 4075.15 mg·g−1 and 1531.16 mg·g−1 for TC and MO at 308 K, respectively. Following five cycles of adsorption and desorption, the removal efficiency for TC and MO remained at 96.25 % and 87.7 %, respectively. The adsorption mechanisms for TC are primarily attributed to hydrogen bonding and complexation interactions. In addition to these mechanisms, ion exchange between NO3– and MO also plays a significant role in the adsorption of MO.