Adsorption performance of high-swelling polyacrylonitrile adsorbents on Yb(III) in high-salt wastewater

Rare earth smelting produces a large amount of high-salt wastewater with low concentrations of rare earth ions, causing both waste and environmental pollution. In this study, polyacrylonitrile (PAN) was modified to prepare an adsorbent for recovering rare earth ions from high-salt solutions generated by rare earth industries. Grafting with ethylenediamine improves the hydrophilic swelling property of PAN and increases the adsorption capacity of the adsorbent, while pyridine (PY) modification improves the Yb³⁺ selectivity of PAN in high-salt solution. PY is the main functional group of adsorption. In studies on the adsorption properties of PAN–NH₂–PY, the removal rate of low-concentration Yb (III) ions from high-concentration NaCl solution exceeded 99 %. Analysis of the adsorption mechanism of PAN–NH₂–PY showed that the pyridine group in PAN–NH₂–PY can form stable coordination bonds with Yb³⁺ and YbCl²⁺ ions in high-salinity solution, whereas swelling of the hydrophilic amino group increases the possibility of interaction between the adsorption site and Yb (III) ions.