Synchronous gelation and lanthanum introduction using bentonite/PVA/SA as the matrix for efficient phosphate removal from aqueous media: Adsorptive behavior and mechanism study

In this work, bentonite was encapsulated into PVA/SA matrix to fabricate bentonite/PVA/SA aerogel (BPS) using lanthanum (La) as the cross-linking agent. La (III) cross-linking reaction with polymers realized synchronous gelation and lanthanum introduction into the composite, which endowed BPS with efficient phosphate removal performance and convenient separation property. Batch experiments indicated that BPS aerogel could maintain efficient and stable phosphate removal (＞95%) within a wide solution pH range (4–10), and well-performed phosphate capturing of BPS at NaCl and seasalt salinity of 0–4% implied its promising application potential in saline environment. Besides, the good fitness of pseudo-second-order kinetic model suggested chemisorption of phosphate on BPS surface, and film diffusion was the primary rate-limiting step. Isotherm study with the preferred fitness of Sips model suggested monolayer adsorption characteristic of BPS at high phosphate concentration, whereas multi-layer coverage of phosphate occurred at low concentration. Maximum experimental adsorption capacity of BPS was detected as ∼28.9 mg P/g, which was competitive among similar adsorbents. In addition, long-term phosphate leakage detection at varied systematic pH suggested the stable binding of phosphate on BPS. The combined characterization analysis illustrated that multiple function including electrostatic attraction, ligand exchange and Lewis acid-base interaction drove the loading of phosphate on BPS surface. Overall results demonstrated certain potential of BPS aerogel as candidate sorbent for phosphate adsorption from complicated aqueous environment.