Heavy metal separation capacity of a porous methacrylamidophenylalanine containing membrane based on a polyhydroxyethyl methacrylate matrix

Abstract

The abilities of various sorbent materials for heavy metal removal have been reported in the literature. We have developed a novel approach to obtain high metal-sorption capacity utilizing a membrane containing 2-methacrylamidophenylalanine. Metal-complexing ligand 2-methacrylamidophenylalanine (MAPA) was synthesized through the use methacrylo chloride and phenylalanine. Then, poly(2-hydroxyethyhmethacrylate-co-2-methacrylamidophenylalanine) (p(HEMA-co-MAPA)) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA in the presence of the initiator azobisisobutyronitrile. MAPA monomer was characterized by nuclear magnetic resonance spectroscopy. p(HEMA-co-MAPA) membranes were characterized by swelling studies, scanning electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. These membranes have large pores; the micropore dimensions are approximately 5-10 mum. p(HEMA-co-MA-PA) affinity membranes with a swelling ratio of 133.2% and containing 18.9 mmol MAPA/m(2) were used in the removal of the heavy-metal ions of copper, nickel, and mercury from aqueous media containing different amounts of these ions (5-600 mg/L) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the MAPA-containing membranes under noncompetitive conditions were 23.8 = mmol/m(2) for Cu(II), 29.1 mmol/m(2) for Ni(II), and 50.3 mmol/m(2) for Hg(II). The affinity order was Hg(II) > Ni(II) > Cu(II). The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at approximately pH 5.0. Adsorption of heavy metal ions from artificial wastewater was also studied. The adsorption capacities were 11.9 mmol/m(2) for Cu(II), 7.33 mmol/m(2) for Ni(II), and 9.79 mmol/m(2) for Hg(II). Desorption of heavy metal ions was performed using 0.1 M HNO3. The p(HEMA-co-MAPA) membranes are suitable for more than five cycles without noticeable loss of capacity.