Engineered thin film nanocomposite membranes with a polyethyleneimine interlayered sulfonated MXene for superior groundwater desalination†

Abstract

MXenes, advanced 2D layered nanocomposite materials, have exhibited significant potential for enhancing the efficiency and effectiveness of thin film nanocomposite (TFN) membranes in desalination applications. This study aims to develop an efficient TFN membrane for groundwater desalination by integrating a sulfonated polydopamine-functionalized MXene (SPMX) onto a polyethyleneimine (PEI) interlayer. Morphological and functional group analyses of SPMX indicated the alterations in the interlayer spacing of the MXene sheets. Analysis of membrane surface morphology and energy-dispersive X-ray (EDX) spectroscopy confirmed the dispersion of SPMX nanosheets on the TFN surface. The PEI interlayer serves as a pivotal component in interfacial polymerization, facilitating the formation of a thin poly(piperazine-amide) layer and enhancing the anchoring of SPMX. The 0.1 wt% SPMX TFN (iSPMXTFN-2) membrane exhibited a lower contact angle value of 38°, indicating an improvement in hydrophilicity due to SPMX incorporation. The membrane performance analysis revealed that SPMX displayed a superior water permeability of 5.59 L m⁻² h⁻¹ bar⁻¹ and Na₂SO₄ rejection of 97.8%. Additionally, both MXene (iMXTFN) and SPMX TFN (iSPMXTFN) membranes exhibit exceptional antifouling properties against humic acid, calcium sulfate, sodium alginate and bovine serum albumin (BSA) solutions. Incorporation of SPMX into the polyamide layer improved resistance to chlorine attack on poly(piperazine-amide) chains. 0.1 wt% SPMX TFN membranes exhibited superior groundwater desalination performance, with higher flux and a reduced flux reduction ratio of 12%, while achieving removal efficiencies of 90% for SO₄, 66% for Na, and 40% for B. Engineered TFN membranes with PEI-interlayered SPMX demonstrated effective performance as membrane materials in pretreatment for superior groundwater desalination.