Efficient separation of phosphate ions in water using tris(hydroxymethyl)aminomethane modified polyaniline-p-phenylenediamine composite membrane

In this study, polyaniline-p-phenylenediamine (PAPD) was employed as an amino monomer to fabricate a polyaniline-p-phenylenediamine composite membrane (PAPD/PES) with a nanoparticle-like surface morphology. Additionally, we used interfacial polymerization of Tris(hydroxymethyl)aminomethane (THAM) to hydroxylate the PAPD/PES composite membrane, resulting in the formation of a TPAPD/PES composite membrane. THAM is an economical and environmentally friendly monomer, rarely used for surface modification of composite membranes through interfacial polymerization. Following the introduction of THAM, a significant abundance of hydroxyl groups appeared on the membrane’s surface, enhancing its hydrophilicity and electronegativity. This, in turn, improved both flux and rejection capabilities. Simultaneously, the introduction of THAM led to the formation of a hydration layer growing on the membrane’s surface, further enhancing its antifouling performance. The optimal polymerization concentration (0.5 mol/L) of THAM was used to synthesize the TPAPD/PES composite membrane, resulting in a flux of 84.18 L m −2 h −1 bar −1 , which was 1.46 times higher than that of the PAPD/PES composite membrane before polymerization. Additionally, the phosphate rejection rate was determined to be 92.14 % (with an initial phosphate concentration of 10 mg P/L). Long-time running and operating pressure tests results confirmed the remarkable stability of the TPAPD/PES composite membrane. Furthermore, the phosphate separation property of the TPAPD/PES composite membrane was evaluated using real wastewater samples (with an initial phosphate concentration of 1.03 mg P/L) as the research object. After separation, the permeate displayed a phosphate concentration of 0.28 mg P/L, meeting the first-class A standard for urban sewage treatment in China (0.5 mg P/L). This indicates that the prepared TPAPD/PES composite membrane has significant potential for practical application.