El-Sayed A. Hegazy

Selective removal of some heavy metal ions from aqueous solution using treated polyethylene-g-styrene/maleic anhydride membranes

Abstract Radiation graft copolymerization of styrene/maleic anhydride (Sty/MAn) comonomer onto low density polyethylene (LDPE) membrane was investigated. The prepared grafted membranes were treated with different reagents containing various functional groups and studied as a matrix for the purpose of water purification from heavy metals. The metal ion uptake by the functional groups of membranes was determined by the use of X-ray fluorescence (XRF) and atomic absorption (AA). The effect of pH of the metal feed solution and immersion period needed for maximum capacity was investigated. The selectivity of different prepared membranes towards some selected metal ions such as Fe, Cu, Pb,… etc. which commonly exist in waste water was determined. The affinity of the treated grafted films to recover Fe(III), Cu(II) or Pb(II) from their aqueous solutions containing other metal ions such as Cd(II), Ni(II) or Hg(II) was studied. Also the selectivity of treated grafted membranes towards Cu(II), Cr(III) and Fe(III) in a mixture was investigated at room temperature and 70°C. It was found that the thiosemicarbazide-, hydroxylamine·HCl- and NaOH-treated grafted films showed high selectivity towards Cu(II), Cr(III) and Fe(III), respectively, at 70°C. However, the selectivity of such treated grafted membranes was remarkable towards Fe(III) at room temperature. The results obtained suggested that the treated grafted membrane possessed good chelating properties towards different metal ions. This suggests that such membranes could be accepted for practical uses.

Adsorption and desorption of phosphate and nitrate ions using quaternary (polypropylene-g-N,N -dimethylamino ethylmethacrylate) graft copolymer

Study has been made on the preparation of functionalized copolymer by grafting N,N-(dimethylaminoethyl) methacrylate (DMAEMA) onto polypropylene (PP) films using gamma-irradiation technique. The effect of monomer concentration and irradiation dose on the grafting yield was studied. It was found that grafting yield increases with increasing the monomer concentration and irradiation dose. Subsequent quaternization of the amine group of PDMAEMA graft chain using different reagents, 1-bromo octadecane, methyl iodide and benzyl chloride, to improve their ionic character was carried out. The grafted PP films were characterized by IR spectroscopy, and mechanical and thermal properties. During the adsorption of phosphate (PO(4)(3-)) and nitrate (NO(3)(-)) ions, the rate of adsorption, pH effect, desorbability and initial feed concentration effect were investigated. It was found that the adsorption of PO(4)(3-) and NO(3)(-) ions increases with increasing the adsorption time up to 10h and decreases with increasing the pH of medium. The desorbability is ranging from 18 to 30%, and it is relatively difficult to desorb PO(4)(3-) and NO(3)(-) ions from the functionalized grafted copolymers. Results showed good possibility for the use of such functionalized grafted film in the field of removal of some anions such as PO(4)(3-) and NO(3)(-) from their media.

Selective separation of some heavy metals by poly(vinyl alcohol)-grafted membranes

A poly(vinyl alcohol) membrane (PVA) was modified by radiation graft copolymerization of acrylic acid/styrene (AAc/Sty) comonomers. The Cu and Fe ion-transport properties of these membranes were investigated using a diaphragm dialysis cell. In the feed solution containing CuCl2 or a mixture of CuCl2 and FeCl3, the PVA-g-P(AAc/Sty) membranes showed high degrees of permselectivity toward Cu2+ rather than toward Fe3+. The permeation of Cu2+ ions through the membranes was found to increase with decrease in the grafting yield. However, as the content of Cu2+ ions in the Cu/Fe binary mixture feed solutions decreased, the rate and the amount of transported Cu2+ through the grafted membrane decreased, with no appreciable permselectivity toward Fe3+. When Fe2+ ions were used instead of Fe3+ ions in the feed solution containing Cu2+, the transport of both Cu2+ and Fe2+ through the membrane was observed. The rate of transport of Fe2+ was higher than that of Cu2+. In addition, it was found that the selective transport of ions was significantly influenced by the pH difference between both sides of the membranes. As the pH of the feed or the received solution decreased, both Cu2+ and Fe3+ passed through the membrane and were transported to the received solution. The role of carboxylic acid and the hydroxyl groups of the grafted membranes in the transportation process of ions is discussed.

Irradiation effects on aromatic polymers: 1. Gas evolution by gamma irradiation

Abstract The effects of gamma irradiation on aromatic polymers, such as polyimides (Kapton, Upilex-R and Upilex-S), poly(aryl ether ether ketone) (PEEK), poly(aryl ether sulphone) (PES), bisphenol A type Udel poly(aryl sulphone) (U-PS) and poly(aryl ester) (U-Polymer), were investigated based on gas evolution. The radiation resistance in terms of gas evolution was in the following order: Upilex-R ⩾ Kapton > PEEK > PES > Upilex-S ⪢ U-PS > U-Polymer. The G values of total gases from these aromatic polymers were 1 100 th to 1 1000 th of the G values from aliphatic polymers. The major component gases were: H 2 and N 2 for polyimides; CO 2 and CO for PEEK; CO 2 , CO and SO 2 for polysulphones; and CO and CO 2 for U-Polymer. The influence of crystallinity on the behaviour and yield of gas evolution was investigated in PEEK. Crystalline PEEK gave lower yield compared to amorphous PEEK. The radiolysis mechanism of gaseous products was discussed based on the structures of the aromatic polymers.

Anionic/Cationic Membranes Obtained by a Radiation Grafting Method for Use in Waste Water Treatment†

Investigations were carried out on different ionic membranes, which were 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 via their functional groups was determined by using atomic absorption and X-ray fluorescence. The amount of metal uptake by the prepared membranes increased significantly as the pH of the metal feed solution increased (pH ≤ 5.3) and the chelated metal ions were easily desorbed by treating the membrane with 0.1 M HCl for 2h 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 investigated using mixtures of two or three metals in the same feed solution. The membranes showed high selectivity towards Fe(III) ions. Characterization of the graft copolymers containing metals was determined by thermogravimetric analysis (TGA) and X-ray diffraction (XRD). TGA results showed that the decomposition of the graft copolymer in the presence of chelated metal ion occurred at temperatures above 300°C. The XRD of LDPE-g-P(AAc/4VP) treated with Fe(III) at various concentrations showed that the crystallinity decreased to a certain limiting value. The complexed copolymers could be recycled several times and showed high selectivity to the Fe(m) ion in the presence of the other metal ions investigated. This may make such grafted membranes acceptable for practical use in waste water treatment.

Preparation and characterization of supported hydrogels obtained by radiation grafting of binary monomers

The preparation and characterization of supported hydrogels obtained by radiation-induced graft copolymerization of styrene/maleic anhydride (Sty/MAn) binary monomers system onto low density polyethylene films were investigated. Attention was focused on the selection of the reaction parameters suitable for the commercial production of such hydrogels. The factors which affect the preparation process and grafting yield are type of solvent, dose rate, total dose, comonomer composition and their concentrations in the diluents. The structure and composition of the grafted chains were also determined. The change in tensile strength and percent elongation at break with degree of grafting was determined for the untreated LDPE-g-P(Sty/MAn) membranes. It was found that the tensile strength improved by grafting but the percent elongation decreased. The change in thermal parameters was measured using differential scanning calorimeter (DSC). The grafted P(Sty/MAn) chains are amorphous in nature and a slight effect on the crystallinity of PE structure was observed. The possibility of the practical uses of such modified membranes was suggested.

Irradiation effects on aromatic polymers: 2. Gas evolution during electron-beam irradiation

The gas evolution caused by electron-beam (e.b.) irradiation of aromatic polymers, such as polyimides (Kapton, Upilex-R and Upilex-S), poly(aryl ether ether ketone) (PEEK), poly(aryl ether sulphone) (PES), bisphenol A type Udel poly(aryl sulphone) (U-PS) and poly(aryl ester) (U-Polymer), has been quantitatively analysed. The radiation resistance in terms of gas evolution was in the following order: Upilex-R ⋍ Upilex-S >Kapton >PEEK >PES ⪢ U-PS >U-Polymer. The component gases evolved from these aromatic polymers by e.b. irradiation were the same and possessed similar behaviour to those produced by gamma irradiation. But differences were found in the G values of some component gases evolved under e.b. irradiation compared with gamma irradiation due to the temperature rise caused by the high dose rate of e.b. irradiation. The effect of molecular structure and chemical unit linkages in the aromatic polymers on gas evolution was investigated. It was found that the biphenyl imide, tetracarboxylic acid anhydride imide, and aryl ether ketone unit linkages exhibited a protective effect against both e.b. and gamma irradiation. But aryl sulphone, isopropylidene aryl sulphone and aryl ester structures are sensitive to radiation. The polyimides and PEEK showed high radiation resistance, which can be of practical importance.

Advances in radiation grafting

Graft copolymerization is an attractive means for modifying base polymers because grafting frequently results in the superposition of properties relating to the backbone and pendent chains. Among the various methods for initiating the grafting reaction, ionizing radiation is the cleanest and most versatile method of grafting available. Ion-exchange membranes play an important role in modern technology, especially in separation and purification of materials. The search for improved membrane composition has considered almost every available polymeric material because of its great practical importance. Grafting of polymers with a mixture of monomers is important since different types of chains containing different functional groups are included. A great deal is focused on the waste treatment of heavy and toxic metals from wastewater because of the severe problems of environmental pollution. Functionalized polymers suitable for metal adsorption with their reactive functional groups such as carboxylic and pyridine groups suitable for waste treatment were prepared by radiation grafting method. More reactive chelating groups were further introduced to the grafted copolymer through its functional groups by chemical treatments with suitable reagents. The advances of radiation grafting and possible uses are briefly discussed.

Improvement of antioxidant activity of chitosan by chemical treatment and ionizing radiation.

Modification of chitosan (CS) to N-maleoylchitosan (NMCS), N-phthaloylchitosan (NPhCS) and sulfonated-chitosan (SCS) was done using maleic anhydride, phthalic anhydride and chlorosulfonic acid, respectively followed by exposing them to γ-rays at different doses. The molecular weights and structural changes of irradiated chitosan derivatives were determined by GPC, FT-IR and UV-vis spectrophotometer. The molecular weights decreased with increasing irradiation dose. Results revealed that the main polysaccharide structure remained after irradiation. To investigate the enhancement of antioxidant activity of chitosan and its derivatives of different molecular weights, radical mediated lipid peroxidation inhibition, scavenging effect of DPPH radicals, reducing power and ferrous ion chelating activity assays were used. Chitosan derivatives with different molecular weights exhibit antioxidant activity. The lower the molecular weights of chitosan and its derivatives, the higher the antioxidant activity. NMCS possessed high scavenging effect on DPPH radicals compared with NPhCS, SCS and ascorbic acid. The irradiated chitosan and its derivatives could be used as natural antioxidants.

Developing the Potential Ophthalmic Applications of Pilocarpine Entrapped Into Polyvinylpyrrolidone–Poly(acrylic acid) Nanogel Dispersions Prepared By γ Radiation

The aim of this study was to improve the stability and bioavailability of pilocarpine in order to maintain an adequate concentration of the pilocarpine at the site of action for prolonged period of time. Thus, pH-sensitive polyvinylpyrrolidone-poly(acrylic acid) (PVP/PAAc) nanogels prepared by γ radiation-induced polymerization of acrylic acid (AAc) in an aqueous solution of polyvinylpyrrolidone (PVP) as a template polymer were used to encapsulate pilocarpine. Factors affecting size and encapsulation efficiency were optimized to obtain nanogel suitable for entrapping drug efficiently. The PVP/PAAc nanogel particles were characterized by dynamic light scattering (DLS), zeta potential, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM), and their size can be controlled by the feed composition and concentration as well as the irradiation dose. Pilocarpine was loaded into the nanogel particles through electrostatic interactions where the AAc-rich nanogels exhibited the highest loading efficiency. The transmittance, mucoadhesion, and rheological characteristics of the nanogel particles were studied to evaluate their ocular applicability. The in vitro release study conducted in simulated tear fluid showed a relatively long sustained release of pilocarpine from the prepared PVP/PAAc nanogel particles if compared with pilocarpine in solution.