Ionic membranes obtained by radiation grafting for the use in waste treatment

The selectivity of polyethylene-Styrene/Maleic anhydride graft copolymer membranes LDPE-g-P(Sty/MAn) prepared by γ irradiation towards different metal ions such as Fe, Cu, Cd and Pb was studied for its possible use in waste water treatment. The sorption capacity of metal ions by the sorbent membranes via their functional groups was determined by using atomic absorption, X-ray fluorescence and UV spectrophotometry. The effect of immersion periods needed for maximum capacity, pH of the feed metal solution and degree of grafting on the sorption capacity were also investigated. Improvement in the chelation property of the grafted membranes was also carried out by further chemical treatment with hydroxylamine-HCl and thiosemicarbazide. The selectivity of untreated grafted films towards Fe3+ is pronounced in feed solution containing Fe3+, Pb2+, Co2+, Cd2+ and Cu2+. The selectivity of the treated grafted films with hydroxylamine-CHl towards Fe2+ is more remarkable. The introduction of thiosemicarbazide groups in the Sty/MAn graft chains resulted in transfer of the membrane selectivity from Fe3+ to Cu2+. Also, the recovery of Hg from aqueous solution that contain other metal ions was studied. Thermal stability of the untreated and metal ion containing grafted copolymers was determined using TGA and DTA. TGA results showed that the thermal deposition of the grafted copolymer in the presence of chelated Cu2+ occurred at higher temperatures than that for the grafted copolymer. Thermal stability for the membrane that contains metal ions is of the order Cu>Cr>Fe> free metal grafted membranes. These grafted membranes possessed good properties toward metal chelation and practical interest for the waste water treatment of heavy and toxic metals