A facile route to polyethyleneimine functionalized polyethersulfone membranes for drinking water softening and removal of diverse pollutants

With the rapid development of fine chemical industries and electronics manufacturing industries, a large amount of wastewater containing endocrine disrupters, antibiotics, dyes and heavy metal ions have been discharged into the environment, threatening the safety of drinking water. In this work, polyethyleneimine-polyethersulfone (PEI-PES) copolymer was synthesized via the chain exchange reaction, then blended with polyethersulfone (PES) for the fabrication of polyethyleneimine functionalized polyethersulfone (PEI-PES/PES) membranes via phase separation process. The as-prepared membranes can efficiently remove multiple pollutants from water through the dual mechanism of filtration and surface adsorption of the PEI segments. The membranes are hydrophilic and positively charged, therefore they had well perm-selectivity. Especially, the PEI-PES/PES membrane with PEI loading of 30 wt% in polymers (namely M30) exhibited a good monovalent and divalent ion selectivity with a CaCl₂ rejection of 78.0 % and NaCl rejection of 38.3 % at a water flux of 181 L·m⁻²·h⁻¹, owing to the sieving effect and the Donnan exclusion. In addition, the adsorption kinetics of the as-prepared membranes toward bisphenol A (BPA), tetracycline (Tc), sunset yellow (SY), and copper ion (Cu²⁺) followed a pseudo-second-order model. The corresponding equilibrium adsorption amount of M30 was 8.9, 7.1, 127.6 and 21.9 mg·g⁻¹, respectively. The adsorption performance was almost unaffected by salt and well recycled. The prepared PEI-PES/PES membranes demonstrated significant application potential in saline softening and security guarantee of drinking water.