Ahmed M. Dessouki

Membranes prepared by radiation grafting of binary monomers for adsorption of heavy metals from industrial wastes

Abstract Preparation of synthetic membranes using simultaneous radiation grafting of acrylic acid (AAc) and styrene (Sty) as individually and in binary monomer mixture onto low density polyethylene (LDPE) has been carried out. The effect of preparation conditions such as irradiation dose, monomer concentration, comonomer composition, and solvent on the grafting yield was investigated. Characterization and some properties of the prepared membranes using different analytical techniques are studied, accordingly the possibility of its practical use in industrial waste treatment is determined. The swelling behavior, electrical conductivity, thermal stability, and mechanical properties of the membranes were investigated as a function of the grafting degree. The prepared cation-exchange membranes possessed good electrical and mechanical properties, high thermal stability and possess good characteristics for separation processes. These membranes have also good affinity toward the adsorption or chelation with Fe 3+ and Pb 2+ ions either in mixture containing other metals or if exists alone in the waste solution.

Crosslinked grafted PVC obtained by direct radiation grafting

Abstract Direct radition-induced grafting of 4-vinylpyridine onto both pure and plasticized poly(vinyl chloride) has been studied. The effect of grafting conditions such as solvent, monomer concentration, irradiation dose, and inhibitor concentration on the grafting yield was investigated. The grafting process was enhanced by using distilled water as diluent and higher degrees of grafting were obtained as compared with other solvents used (benzene, methanol, and a mixture of methanol and water). The homopolymerization of 4-vinylpyridine was reduced to a minimum using ammonium ferrous sulfate and the suitable optimum concentration of the inhibitor was found to be 0.25 wt %. It was observed that the degrees of grafting onto plasticized PVC were higher than those onto pure one, at constant grafting conditions. The diffusibility of the monomer solution through the trunk polymers enhanced at higher monomer concentrations. The higher the monomer concentration the higher the degrees of grafting obtained. The dependence of the grafting rate on monomer concentration was found to be 0.15 and 0.4 order for the grafting onto pure and plasticized PVC films, respectively. The degree of grafting, at the higher irradiation doses, deviated from linearity and it tends to level off due to the recombination of some of the free radicals without initiating graft polymerization. Gel determination in the grafted films was investigated. The gel content in both grafted extracted pure and plasticized PVC films increased with the degree of grafting to reach a certain limiting values.

Anionic membranes obtained by radiation grafting of 4-vinylpyridine onto poly(vinyl chloride)

Abstract Some properties of the membranes obtained by radiation grafting of 4-vinylpyridine onto poly(vinyl chloride), PVC, have been studied. Quaternization of nitrogen atoms in the grafted films was completely achieved by using Mel and HCL as quaternizing agents. The grafted quaternized pure and plasticized PVC films possess much higher water uptake percent than those grafted unquaternized ones. The quaternized grafted films also show higher electrical conductivity than grafted unquaternized ones. Furthermore, the electrical conductivity of Mel- and HCL-quaternized plasticized PVC films was 100 times that those of quaternized pure, at a given degree of grafting. The tensile strength and elongation percent for the trunk films were measured at various irradiation doses in N 2 atmosphere and in air. The mechanical properties of the wet grafted films were also investigated for films having various degrees of grafting. The good swelling behaviour of the grafted quaternized PVC films and the good mechanical strength of the grafted films may make them acceptable for handling and practical use as anion-exchange membranes.

Chemical reactive filter paper prepared by radiation-induced graft polymerization—I

Abstract Chelating filter papers with chemically bonded amidoxime groups were synthesized by radiation-induced grafting of acrylonitrile onto filter paper (W3) followed by chemical treatment with hydroxylamine. The effect of grafting conditions such as absorbed dose, dose rate, monomer concentration and filter paper thickness on the grafting yield was studied. It was found that the degree of grafting increases with increasing absorbed dose and dose rate, and then tends to level off at high doses. The order of the dependence of the initial grafting rate on the dose is found to be of 0.33. An increasing monomer concentration was accompanied by a significant increase in grafting. At high monomer concentration the initial rate of grafting is fast followed by a slow rate. The rate of grafting is controlled by the filter paper thickness and the diffusion of monomer into the interior of the filter paper. Mechanical properties of the prepared filter paper were improved over the ungrafted paper. The amidoxime filter papers were examined for adsorption of uranium concentration ranging between 10–100 ppm.

Physical properties of graft copolymer-metal complexes obtained by radiation grafting onto poly(tetrafluoroethylene-co-perfluorovinyl ether)

Abstract Grafting of aqueous acrylic acid onto poly(tetrafluoroethylene-co-perfluorovinyl ether) films has been carried out using γ-irradiation. Copper and chromium complexes have been prepared by treating the grafted films with aqueous solutions of copper and chromium sulphates. The formation of polymer/metal complexes has been confirmed spectrophotometrically by u.v. and colour measurements. Electrical and mechanical properties of films of the complexes have been studied. Thermal analysis and study of the effect of u.v. on the polymer metal complexes have been also undertaken.

Chelating polymer granules prepared by radiation-induced homopolymerization. I—Kinetic study of radiation polymerization process

Chelating polymer granules containing amidoxime chelating groups were synthesized by radiation-induced homopolymerization of acrylonitrile monomer. The chemical reactive intermediate polyacrylonitrile was treated with hydroxylamine solution to convert the chemical active cyano groups into the amidoxime groups. Kinetic study of the effects of monomer concentration, radiation dose, dose rate, and temperature on the polymerization process was investigated. It was found that at low monomer concentration, the rate of polymerization is roughly independent on the initial monomer concentration, while at high monomer concentration, 35–65%, a marked acceleration on the rate was observed. The order of the dependence of the initial rate of polymerization on the dose rate is 0.77, which deviates from the classical square-root law due to the precipitation of the formed polymer. The conversion percent and molecular weight of the produced polymer are inversely proportional to dose rate at constant radiation dose. The activation energy was found to be 2.7 kcal/mol, and the rate constant of initiation is independent of temperature. The effect of type of solvent on the polymerization was studied. DMF solvent of the closest solubility parameter to the solubility parameter of polyacrylonitrile is the best solvent for the polymerization process.

Ion-containing reverse osmosis membranes obtained by radiation grafting method

Abstract Cationic membranes obtained by radiation grafting of acqueous acrylic acid onto low density polyethylene films followed by alkaline treatment to confer ionic character in the graft chains, were tested for reverse osmosis desalination of saline water. Selected physical properties of such membranes were investigated. The grafted membranes prossess good mechanical and electrical properties. Water uptake for the alkali-treated membrane was much higher than that of the alkali-untreated one. The effect of operation time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection for the grafted membranes was investigated. Such cationic membranes showed good durability, thermal and chemical stability, acceptable water flux and salt rejection which may make them acceptable for practical use in reverse osmosis desalination of sea water.

Post radiation grafting of vinyl acetate onto low density polyethylene films: Preparation and properties of membrane

Abstract Reverse osmosis membranes were prepared by the post radiation grafting of vinyl acetate onto low density polyethylene films. The factors affecting the grafting process such as radiation dose, monomer concentration and temperature on the grafting yield were studied. It was found that the dependence of the grafting rate on radiation intensity and monomer concentration was found to be of 0.64 and 1.4 order, respectively. The activation energy for this grafting system was calculated and found to be 4.45 kcal/mol above 30°C. Some properties of the grafted films such as specific electric resistance, water uptake, mechanical properties and thermal and chemical stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications. The use of such membranes for reverse osmosis desalination of saline water was tested. The effect of operating time, degree of grafting and applied pressure on the water flux and salt rejection were determined. The results showed salt rejection percent over 90% and a reasonable water flux. A suitable degree of grafting of the membrane was determined as well as the optimum applied pressure.

Radiation-induced graft polymermization of acrylamide onto poly(tetrafluoroethylene/ Hexaflouropropylene/vinylidene fluoride) (TFB) films

Abstract Radiation-induced graft polymerization of acrylamide (AAm) onto poly(tetrafluoroethylene/ hexafluoropropylene/vinylidene fluoride) (TFB) films has been investigated. The appropriate reaction conditions at which the graft polymerization was carried out successfully were selected. It was observed that the grafting process was enhanced remarkably by using distilled water as diluent. In this grafting system ammonium ferrous sulphate (Mohrs salt) was used as inhibitor to minimize the homopolymerization of AAm and the suitable concentration of such inhibitor was found to be 3.5wt%. The dependence of the grafting rate on the monomer concentration was calculated to be 2.8 order. Some properties of the grafted films such as water uptake, electrical conductivity, mechanical properties and chemical and thermal stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications.

Radiation initiated grafting onto fluoro polymers for membrane preparation II

Abstract The radiation initiating grafting of acrylamide (AAm) onto poly(tetrafluoroethylene/ hexafluoropropylene/vinylidene fluoride), TFB, films using the post-radiation grafting technique has been investigated. The factors affecting the grafting process such as radiation dose, dose rate, monomer concentration and temperature on the grafting yield were studied. It was found that the grafting yield is strongly dependent on the dose but independent on the dose rate. The dependence of the grafting rate on monomer concentration was found to be of 1.44 order. The results showed a steady increase of the initial grafting rate with temperature, whereas the final grafting yield passes a maximum around 45°C. The Arrhenius plot reveals two straight lines with different slope intersecting around 35°C. The overall activation energy for this grafting system was calculated and found to be 16.5 and 32.4 kcal/mol above and below 35°C, respectively. This behaviour is presumably correlated to a glass transition of the trunk polymer arising from amorphous material under restraint by crystallites. Some properties of the grafted films such a specific electric resistance, water uptake, mechanical properties and chemical and thermal stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications.