ANIONIC CATIONIC MEMBRANES OBTAINED BY A RADIATION GRAFTING METHOD FOR USE IN WASTE-WATER TREATMENT/

Investigations were carried out on different ionic membranes, which we re prepared by radiation-induced graft copolymerization. Cationic (low density polyethylene (LPDE)-g-poly(acrylic acid) (PAAc)) and cationic /anionic (LDPE-g-P(AAc/4-vinyl pyridine (4VP)) membranes) were used to elucidate the possibility of their practical use. The metal uptake vi a their functional groups was determined by using atomic absorption an d X-ray fluorescence. The amount of metal uptake by the prepared membr anes increased significantly as the pH of the metal feed solution incr eased (pH less than or equal to 5.3) and the chelated metal ions were easily desorbed by treating the membrane with 0.1 M HCl for Zh at room temperature. The maximum uptake for a given metal was higher for the cationic/anionic membranes than for the cationic ones. The selectivity of the cationic/anionic membranes towards different metals was invest igated using mixtures of two or three metals in the same feed solution . The membranes showed high selectivity towards Fe(III) ions. Characte rization of the graft copolymers containing metals was determined by t hermogravimetric analysis (TGA) and X-ray diffraction (XRD). TGA resul ts showed that the decomposition of the graft copolymer in the presenc e of chelated metal ion occurred at temperatures above 300 degrees C. The XRD of LDPE-g-P(AAc/4VP) treated with Fe(III) at various concentra tions showed that the crystallinity decreased to a certain limiting va lue. The complexed copolymers could be recycled several times and show ed high selectivity to the Fe(III) ion in the presence of the other me tal ions investigated. This may make such grafted membranes acceptable for practical use in waste water treatment.