Modulating the polyamide nanofiltration membrane using a tert-Butyl N-(2-aminoethyl)carbamate in the aqueous phase of interfacial polymerization for enhanced desalination

The current study is carried out to modulate the growth of the polyamide active layer by using tert -Butyl N- (2-aminoethyl)carbamate (Boc-EDA) as an aqueous additive to the piperazine (PIP) containing aqueous phase. Owing to the presence of amino groups and an amide bond in Boc-EDA, it can potentially interact with PIP to control interfacial polymerization (IP) and hence the growth of the polyamide active layer. These changes in the polyamide active layer are observed as variations in surface morphology and topology, as studied by scanning electron microscopy and atomic force microscopy, respectively. Compared with the control EDAM-0 (2 wt% PIP) membrane, the Boc-EDA-incorporated membranes have a smooth surface composed of small, closely spaced ridges and valleys, attributed to altered diffusion kinetics during IP. Direct confirmatory evidence for the participation of Boc-EDA in the IP reaction with TMC was obtained from proton nuclear magnetic resonance (¹H NMR) spectroscopy. In addition, the reaction of Boc-EDA with certain benzoyl chloride groups on trimesoyl chloride (TMC) may reduce the degree of crosslinking. As a result, the EDAM-2 (2 wt% PIP + 2 wt% Boc-EDA of PIP) membrane shows enhanced desalination performance with a permeance of 3.40 L m⁻² h⁻¹ bar⁻¹ compared to the control membrane having a permeance of 2.58 L m⁻² h⁻¹ bar⁻¹. In the case of rejection of Na₂SO₄, the EDAM-2 shows a rejection of 98.5% compared to 94.1% in the case of the EDAM-0 control membrane. The EDAM-2 membrane maintained Na₂SO₄ rejection, reaching 97.6% after 30 h of continuous crossflow filtration. Moreover, the EDAM-2 rejected 97.5% of the MgSO₄.