Revealing the phosphorus and fluorine adsorption behavior of (modified) vermiculite: Enhancing comprehensive performance in phosphogysum leachate

Abstract

Phosphogypsum leachate, generated through rainfall-induced erosion, contains high levels of soluble phosphorus (P) and fluorine (F), posing serious environmental risks. This study employs a facile modification method that increases the surface area of vermiculite up nearly 100 times, while introducing abundant cation active sites for adsorption of P and F. The A1 adsorbent exhibited the best performance in removing soluble P and soluble F. Under optimal conditions (pH 11, adsorbent dosage of 5.5 g·L^-1, adsorption time of 480  min, and adsorption temperature of 50 °C), the adsorbent exhibited selective adsorption for soluble P and soluble F (with a selective adsorption preference difference of 79.71). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the surface of modified vermiculite covered with dense nanoparticles and stacking pores, which expose more active sites. Combined with X-ray photoelectron spectroscopy (XPS) analysis, the adsorption of P and F occurs primarily through surface complexation via ligand exchange. Regeneration studies revealed that A1 exhibited good desorption and regeneration performance, which retained 75 % of P and 44 % of F adsorption capacity after six regeneration cycles.