Polyelectrolyte-Enhanced Ultrafiltration (PEUF) Process for Low Level Arsenic Removal: Recovery of Polyelectrolyte from Retentate Stream

Abstract

Removal of low levels of arsenic from contaminated water using the polyelectrolyte-enhanced ultrafiltration or PEUF process technology has been studied. The cationic polyelectrolyte poly (diallyldimethyl ammonium chloride), PDADMAC, was utilized to bind arsenic (in the form of arsenate anion) in contaminated water and the polyelectrolyte-arsenate complex solution was then filtered off (as retentate) by ultrafiltration. The 99-99.9% arsenic removal from synthetic low level arsenic (100 ppb) contaminated water demonstrates that the technology can easily achieve the relatively new international arsenic maximum concentration level of 10 ppb. To make the PEUF process more economical and environmentally friendly, the PDADMAC in the retentate must be recovered. Precipitation of PDADMAC-arsenate solutions with divalent cations has been studied to separate out metal-arsenate compounds leaving free PDADMAC to reuse in the process. The metal-arsenate compound precipitation is strongly affected by divalent metal:As molar ratio, and pH of the solution. The precipitation results also suggest that polyelectrolyte retards formation of the metal-arsenate compounds and affects the size and morphology of the particles formed, thus directly affecting the sedimentation rate of the resulting precipitate.

Crosslinked polyDADMAC gels as highly selective and reusable arsenate binding materials

“…According to the literature, at pH 6, 80% of arsenate ions carry (À1) a charge and the remaining 20% have (À2) charges [13]. Consequently, increasing negative charge increases the electrostatic attraction of the cationic charges, as reported for As removal by water-soluble, linear p(DADMAC) [2,13,15].…”

“…Linear poly(diallyldimethylammonium chloride) (DAD-MAC) is included among the polymers with proven effectiveness for removing As(V). Pookrod et al [2,13,15] also studied linear, water-soluble DADMAC for the removal of As(V), demonstrating that the polymer was indeed effective in this respect. The literature reveals several studies dedicated to the arsenic removal efficiency of hydrogels, such as poly(3-acrylamidopropyl) trimethylammonium chloride (p(APTMACl)) hydrogels [19] and vinyl pyridine-based hydrogels [20].…”

“…In particular, it was observed that polymers with quaternary amine groups were effective for removing As(V) during membrane-assisted studies [1][2][3][4][5][6][13][14][15]. Rivas et al [5] reported the successful removal of arsenic with various watersoluble polymers combined with ultra-filtration using (R) 4 N + X À groups.…”

“…Polymer-assisted removal processes have been extensively studied for the removal of arsenic using both soluble and insoluble polymers [1][2][3][4][5][6][13][14][15][16][17][18]. In particular, it was observed that polymers with quaternary amine groups were effective for removing As(V) during membrane-assisted studies [1][2][3][4][5][6][13][14][15].…”