Stable incorporation of amino-functionalized silver phosphate nanoparticles in the polyamide active layer of desalination membranes for enhanced antifouling properties

Abstract

Various nanoparticles (NPs) have been incorporated into the membrane's active layer. Still, the success of such a decoration depends on the nano-size and homogeneity of the dispersion to be used during interfacial polymerization (IP). The current study aimed to achieve a stable and uniform incorporation of the silver phosphate (AgP) NPs in the membrane's active layer to develop efficient desalination and antifouling properties. Hence, this work was focused on obtaining nano-sized silver phosphate and then purposely decorating the amine (-NH₂) functional groups on the AgP NPs, resulting in F–AgP. These features resulted in a uniform and homogeneous dispersion of the F–AgP NPs in the aqueous phase used for IP. The aqueous phase contained diethylenetriamine (DETA, 3A) as an amine, containing 0.05% wt/v of the F–AgP NPs. The obtained aqueous solution gave a uniform incorporation of the F–AgP NPs in the polyamide active layer upon IP reaction with acid chloride in the organic phase. Two organic phases were used: terephthaloyl chloride (TPC) and trimesoyl chloride (TMC) to obtain F–AgP-3A/TPC and F–AgP-3A/TMC membranes. The obtained membranes showed promising desalination performance, where F–AgP-3A/TPC membranes showed Na₂SO₄ and CaCl₂ rejections of >96%, whereas F–AgP-3A/TMC membrane had 83 and 75% rejections, respectively. The impact of feed temperature revealed a slight decline in Na₂SO₄ rejection to 95.0% and an increase in permeate flux to 29.6 L m⁻² h⁻¹ at 35 $°C$ in the case of F–AgP-3A/TPC. In addition, the stability tests also revealed a stable performance of the membranes in terms of permeate flux and salt rejection over 840 min. The BSA fouling studies showed that after an initial minor decrease in the normalized flux of the membranes, the rejection of Na₂SO₄ remained stable at >96%. Regarding anti-biofouling potentials, both membranes performed equally well, owing to AgP NPs in the active layer inhibiting >99% growth of the gram-positive and negative bacterial colonies.