Study on the efficient adsorption of selenium(III) by hydroxyapatite composite zeolite imidazolium framework-67

Abstract

The enrichment and recovery of rare earth ions is an effective way to achieve sustainable utilization of wastewater resources. Using a simple ultrasound assisted synthesis method, nano hydroxyapatite (HAP) was introduced into ZIF-67 at room temperature to synthesize HAP/ZIF-67 composite materials with rich functional groups. XRD, FT-IR, SEM, XPS, and BET were used to characterize HAP/ZIF-67 composite materials. The effects of pH, time, adsorption dose, ambient temperature and initial concentration on the adsorbent were investigated by static repeated adsorption experiments. The results show that the synergistic effect of the Co-OH, -NH-, -C = N- functional groups in ZIF-67 and the Ca-OH and PO43− groups in nano-HAP improves the adsorption capacity of the composite material. It increased to 461.55mg/g, and the adsorption rate increased to 92.31%. They are 2.41 times higher than HAP and 1.55 times higher than ZIF-67. The adsorption characteristic of Ce3+ on HAP/ZIF-67 composites is more consistent with the Langmuir isotherm model and pseudo-second-order model, which indicate a single-layer, surface-homogeneous chemisorption process for Ce(Ⅲ) adsorption. The adsorption process is a spontaneous heat absorption process according to thermodynamic research. The main mechanism of HAP/ZIF-67 adsorption of Ce(Ⅲ) is surface complexation. After four elution experiments, HAP/ZIF-67 adsorbent has good reusability, indicating that HAP/ZIF-67 is a promising adsorbent in the field of rare earth ion recovery.