Fabrication and Characterization of Novel ZnAl-Layered Double Hydroxide for the Superadsorption of Organic Contaminants from Wastewater

Anyu Li; Hua Deng; Chenghui Ye; Yanhong Jiang

doi:10.1021/acsomega.0c01092

Fabrication and Characterization of Novel ZnAl-Layered Double Hydroxide for the Superadsorption of Organic Contaminants from Wastewater

ACS Omega. 2020 Jun 15;5(25):15152-15161. doi: 10.1021/acsomega.0c01092. eCollection 2020 Jun 30.

Authors

Anyu Li^{1

2}, Hua Deng^{1

2}, Chenghui Ye^{1

2}, Yanhong Jiang^{1

2}

Affiliations

¹ Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Ministry of Education, Guangxi Normal University, Guilin 541004, China.
² College of Environment and Resources, Guangxi Normal University, Guilin 541004, China.

Abstract

An imidazole ester skeleton (zeolitic imidazolate framework (ZIF)) was grown on the surface of a ZnAl-layered double hydroxide (ZnAl-LDH) material to form a porous composite (ZIF-ZnAl-LDH). To understand the adsorption characteristics of the two materials, the effects of pH, adsorption time, and adsorption concentration on the adsorption of Congo red (CR) solution were investigated comprehensively. In addition, ZnAl-LDH and ZIF-ZnAl-LDH were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The results clearly showed that ZnAl-LDH had a lamellar structure with a diameter of approximately 200-500 nm and ZIF-ZnAl-LDH had a regular three-dimensional hexagonal structure. The kinetics and thermodynamics of the CR adsorption by ZnAl-LDH and ZIF-ZnAl-LDH can be described using pseudo-second-order (PSO) and Langmuir models, respectively. The highest value of adsorption capacity obtained from the Langmuir equation was equal to 625.00 and 909.09 mg/g for these two compounds, respectively. The values of the standard Gibbs free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) obtained for these adsorption processes prove that the adsorption of CR by ZnAl-LDH and ZIF-ZnAl-LDH is a spontaneous endothermic process. Furthermore, through the analysis of the characterization results, it is concluded that the adsorption mechanisms of ZnAl-LDH and ZIF-ZnAl-LDH on CR are mainly dominated by electrostatic action, functional group action, surface pore adsorption, and anion exchange.