Enhanced phosphate removal using hydrated lanthanum and aluminum oxides co-modified quaternized polyaniline nanocomposite: Performance and mechanism.

Through precursor impregnation diffusion and in-situ co-precipitation methods, a quaternized polyaniline-based composite material (HLAO-PN) was synthesized using quaternized polyaniline (PN) as a carrier, hydrated lanthanum oxide LaOOH, and hydrated alumina AlOOH. The adsorption efficiency and mechanism of phosphate removal by HLAO-PN were systematically studied. Characterization results from SEM, XPS, and FT-IR revealed that HLAO-PN exhibited an aggregated granular structure, with La and Al uniformly distributed on the PN carrier. The main mechanisms of phosphate adsorption by HLAO-PN include electrostatic attraction, ion exchange, and ligand exchange. HLAO-PN demonstrated stable and effective phosphate adsorption capacity across a pH range of 2.0-7.0, with a maximum adsorption capacity of 101.6 mg/g at 308 K. Furthermore, it showed strong anti-interference capabilities in the presence of various coexisting substances. The dynamic adsorption experiments in a fixed-bed system indicated that the effective treatment capacities of HLAO-PN for phosphate during the first and second cycles were 2800 and 2650 bed volumes (BV), respectively (from 10.0 mg P/L to below 0.5 mg P/L). Moreover, the exhausted HLAO-PN could be efficiently regenerated in situ by binary NaOH/NaCl solution. After five adsorption-regeneration cycles, the adsorption capacity of HLAO-PN for phosphate was 70.64% of its initial adsorption capacity (93.87 mg/g). This study presents a novel chemical agent for enhancing phosphorus removal from wastewater. PRACTITIONER POINTS: Composite material (HLAO-PN) was synthesized for phosphate adsorption using quaternized polyaniline, LaOOH, and AlOOH. The adsorption capacity of HLAO-PN reaches 101.60 mg/g at 308 K. The main adsorption mechanisms of phosphate by HLAO-PN are electrostatic attraction, ion exchange, and ligand exchange. The fixed bed dynamic adsorption of phosphate by HLAO-PN was investigated which provides a reference for actual wastewater treatment.