Tuning microscopic structure of La-MOFs via ligand engineering effect towards enhancing phosphate adsorption

Qinqin He; Hongjun Zhao; Zedong Teng; Yali Guo; Xiaonan Ji; Wei Hu; Min Li

doi:10.1016/j.jenvman.2024.120149

Tuning microscopic structure of La-MOFs via ligand engineering effect towards enhancing phosphate adsorption

J Environ Manage. 2024 Feb 27:353:120149. doi: 10.1016/j.jenvman.2024.120149. Epub 2024 Jan 25.

Authors

Qinqin He¹, Hongjun Zhao¹, Zedong Teng², Yali Guo³, Xiaonan Ji³, Wei Hu³, Min Li⁴

Affiliations

¹ Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, China.
² Innovation Academy for Green Manufacture, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China.
³ Shanghai Investigation, Design & Research Institute Co., Ltd., Shanghai, 200335, China; YANGTZE Eco-Environment Engineering Research Center (Shanghai), China Three Gorges Corporation, Shanghai, 200335, China.
⁴ Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, China. Electronic address: minli@bjfu.edu.cn.

PMID: 38278114
DOI: 10.1016/j.jenvman.2024.120149

Abstract

The selection of different organic ligands when synthesizing metal organic framework (MOFs) can change their effects on the adsorption performance. Here, four La-MOFs adsorbents (La-SA, La-FA, La-TA and La-OA) with different organic ligands and structures were synthesized by solvothermal method for phosphate adsorption, and the relationship between their adsorption properties and structures was established. Among four La-MOFs, their phosphate adsorption capacities and adsorption rates followed La-SA > La-FA > La-TA > La-OA. The results indicated that average pore diameter played a key role in phosphate adsorption and there was a positive correlation between average pore diameter and adsorption capacity (R² = 0.86). Coexisting ion experiments showed that phosphate adsorptions on three La-MOFs (La-SA, La-FA and La-TA) were inhibited in the presence of CO₃^2- and HCO₃^-. The inhibition of CO₃^2- was the most pronounced and the results of redundancy analysis pointed out that it was mainly due to the change of pH value. In contrast, La-OA showed enhanced phosphate adsorption in the presence of CO₃^2- and HCO₃^-, and the combination of pH experiments showed that phosphate adsorption by La-OA was increased under alkaline conditions. Further combined with FT-IR, XRD, high resolution energy spectra of XPS (La 3d, P 2p and O 1s) and XANES, the adsorption mechanisms were derived electrostatic attraction, chemical precipitation and inner sphere complexation, and the last two were identified as the main mechanisms. Moreover, it can be identified from XPS 2p that the phosphate adsorption on La-FA and La-OA were mainly in the LaPO₄ state, while La-SA and La-TA mainly existed in the form of LaPO₄·xH₂O crystals and inner sphere complexes. From the perspective of material morphology, this work provides a thought for the rational design of MOFs with adjustable properties for phosphate adsorption.

Keywords: Different organic ligand; Lanthanum; Metal-organic frameworks; Phosphate adsorption.

MeSH terms

Adsorption
Kinetics
Lanthanum / chemistry
Ligands
Metal-Organic Frameworks*
Phosphates / chemistry
Spectroscopy, Fourier Transform Infrared
Water Pollutants, Chemical*

Substances

Phosphates
Metal-Organic Frameworks
Ligands
Lanthanum
Water Pollutants, Chemical