Preparation of organic solvent nanofiltration membranes by interfacial polymerization with phosphonic acid additives in aqueous phase

Abstract

In this research, several phosphonic acid additives were integrated into the aqueous phase to create organic solvent nanofiltration membranes through interfacial polymerization. The main objective was to examine how varying concentrations of aminotrimethylene phosphonic acid influence the separation efficiency of nanofiltration membranes. The hydrogen bonds were formed between the amino (NH₂) groups in the aqueous-phase monomer (MPD) and the phosphonic acid group, which in turn reduced the rate at which MPD diffused into the organic phase. This process resulted in the formation of a thinner active layer of polyamide (PA), which enhanced the permeance of methanol and other pure solvents. Moreover, the nanofiltration membrane's surface, which was created using phosphonic acid additives, showed enhanced roughness, resulting in the development of elevated polyamide clusters. The addition of hydrophilic groups enhanced the membrane surface's hydrophilicity, allowing for the swift movement of polar solvents. The solvent permeance of nanofiltration membranes exhibited varying degrees of enhancement following the incorporation of phosphonic acid additives. Notably, the permeance for methanol achieved a value of 12.5 L m⁻² h⁻¹ bar⁻¹, while the rejection rate for Rhodamine B (RDB) dyes remained at an impressive 98.5 %. The vitamin B12-methanol solution was continuously filtered for 90 min to obtain a 106 times concentrated solution (from 20 mg/L to 2125 mg/L). This study introduces a novel research methodology for the development of nanofiltration membranes optimized for organic solvents.