influence of sodium tripolyphosphate concentration on characteristics and performance of polyamide thin layer membrane in cu (ii) removal

in this work, the effect of presence of the sodium tripolyphosphate (stpp), as an inorganic salt, on improving the performance of polyamide (pa) thin layer membranes has been studied. characterization analyses confirmed the presence of the salt on the whole surface structure of the thin layer. different salt loadings resulted in different fluxes and cu (ii) rejections. the thin layer containing 1% w/w stpp showed favorable flux and relatively good rejection for the cu2+ ions. however, the best rejection was obtained for 5% w/w stpp. atomic force microscopy (afm) and scanning electron microscopy (sem) images confirmed the formation of a dense and compact surface in the presence of stpp in the aqueous phase.