Adsorption of rare earth ions from highly saline media by a pyridine-modified activated carbon sorbent

During the rare earth smelting and separation process, a substantial volume of high-salt wastewater is generated, within which residual low-concentration rare earth ions not only result in waste but also contribute to environmental pollution. In this work, a selective adsorbent used for the recovery of rare earth ions contained in high- salt solutions from the rare earth industry was designed and prepared by grafting pyridine (PY) onto activated carbon (AC) via the use of 3-aminopropyltriethoxysilane (KH550). The results showed that the prepared adsorbent, AC-NH2-PY, exhibited exceptional efficacy in extracting and segregating rare earth ions within high- salt solutions. The speciation of rare earth elements in a high-salt solution was simulated through Visual MINTEQ under different conditions. Adsorption performance assessments revealed that AC-NH2-PY achieved saturated adsorption capacities of 2.978 mg/g for La3+, 7.847 mg/g for Dy3+, and 9.527 mg/g for Yb3+. AC-NH2-PY could maintain a remarkable adsorption capacity for rare earth ions in salt solutions containing 5 % NaCl and in actual industrial wastewater; moreover, the adsorption capacity of the adsorbent remained greater than 80 % after five adsorption cycles.