H. Kamal

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.

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.

Controlling of degradation effects in radiation processing of starch

Corn starch of different physical forms (solid and liquid) was irradiated with 60Co gamma rays and electron beam in the dose range of 50 Gy to 100 kGy to investigate the effect of ionizing radiation on its molecular weight (Mw). Degradation was observed for both solid and liquid states upon radiation. However, degradation of the starch in the liquid state was remarkably greater than that in the solid state. The free radicals that formed during water irradiation must be responsible for such degradation in the liquid form. Thermostated viscometer, rheometer and multi‐angle static laser light scattering were employed to study the changes in the Mw of corn starch that occurred during irradiation at constant temperature and different concentrations. It was observed that electron beam irradiated corn starch has uniform decreasing in Mw and radius of gyration (Rg) in the range of (4.4×107–2.9×107 g mol−1) and (199.3–85.6 nm), respectively. The influence of gas atmosphere on the degradation process during gamma irradiation was studied to find that, the Mw and Rg values were in the range of (4.4×107–1.8×107 g mol−1) and (199.3–120.4 nm) for the oxygen saturated samples, while, they were (4.4×107–1.05×107 g mol−1) and (199.3–85.6 nm) for the argon saturated samples.

Immobilization of Glucoamylase on Polypropylene Fibers Modified by Radiation Induced Graft Copolymerization

Glucoamylase (GA) had been covalently immobilized on polypropylene grafted poly‐acrylamide (PP‐g‐P(AAm)) and polypropylene grafted poly‐acrylic acid (PP‐g‐P(AAc)) fibers by the use of carbodiimide (CDI) as a coupling agent. The polymeric support for enzyme immobilization was prepared using radiation that induced graft copolymerization of acrylamide (AAm) and acrylic acid (AAc) monomers, individually, onto polypropylene fibers followed by chemical treatments. Effects of pH and temperature on the relative activity, as well as storage stability and reusability of the immobilized enzyme, were studied. The kinetic effect of immobilization was also studied to find that, the Km values for glucoamylase immobilized on PP‐g‐P(AAc) and PP‐g‐P(AAm) fibers are 3.4 and 5.88, respectively, i.e., higher than that for free glucoamylase of Km 1.6. An enhancement in the thermal stability of the glucoamylase is observed upon immobilization. The optimum temperature for the immobilized enzyme on both PP‐g‐P(AAc) and PP‐g‐P(AAm) was found to be shifted 5°C higher than that of the free enzyme at 55°C. Investigation of reusability of the immobilized enzyme showed that after 10 cycles the immobilized enzyme retained 60% and 45% of its original activity for PP‐g‐P(AAc) and PP‐g‐P(AAm) carriers, respectively.

Immobilization of glucose isomerase onto radiation synthesized P(AA-co-AMPS) hydrogel and its application

Abstract Isomerization of glucose to fructose was carried out using Glucose isomerase (GI) that immobilized by entrapment into Poly(acrylic acid) P(AA) and Poly(acrylic acid-co-2-Acrylamido 2-methyl Propane sulfonic acid) P(AA-co-AMPS) polymer networks, the enzyme carriers were prepared by radiation induced copolymerization in the presence of (Methylene-bisacrylamide) (MBAA) as a crosslinking agent. The maximum gel fraction of pure P(AA) and P(AA-co-AMPS) hydrogel was found to be 95.2% and 89.6% for P(AA) and P(AA-co-AMPS), respectively at a total dose of 20 kGy. Effects of immobilization conditions such as radiation dose, MBAA concentration, comonomer composition and amount of GI were investigated. The influence of reaction conditions on the activity of immobilized GI were studied, the optimum pH value of the reaction solution is 7.5 and reaction temperature is 65 °C. The immobilized GI into P(AA-co-AMPS) and P(AA) polymer networks retained 81% and 69%, respectively of its initial activity after recycled for 15 times while it retained 87% and 71%, respectively of its initial activity after stored at 4 °C for 48 days. The Km values of free and immobilized GI onto P(AA-co-AMPS) and onto P(AA) matrices were found to be 34, 29.2 and 14.5 mg/mL, respectively while the Vmax Values calculated to be 3.87, 1.6 and 0.79 mg/mL min, respectively. GI entrapped into P(AA-co-AMPS) hydrogel show promising behavior that may be useful as the newly glucose isomerase reactor in biomedical applications.

Characterization and some properties of functionalized graft copolymer

The study involved investigation and characterization of membranes prepared by graft copolymerization of acrylonitrile (AN) and vinyl acetate (VAc) binary monomers onto low density polyethylene (LDPE) and isotactic polypropylene (IPP). The mutual n -irradiation method was used as a grafting technique. IR spectra recorded before and after grafting and also for the chemically treated membranes to elucidate the structural changes occurred due to grafting and chemical treatments. The effects of grafting and chemical treatments on the thermal properties and crystallinity of the prepared graft copolymer have been investigated using DSC, TGA and XRD.