A.A. Sarhan

Adsorption of Cu(II), Co(II), and Ni(II) ions by modified magnetic chitosan chelating resin

Cross-linked magnetic chitosan-isatin Schiffs base resin (CSIS) was prepared for adsorption of metal ions. CSIS obtained was investigated by means of FTIR, (1)H NMR, wide-angle X-ray diffraction (WAXRD), magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of cross-linked magnetic CSIS resin toward Cu(2+), Co(2+) and Ni(2+) ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetic parameters were evaluated utilizing the pseudo-first-order and pseudo-second-order. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 103.16, 53.51, and 40.15mg/g for Cu(2+), Co(2+) and Ni(2+) ions, respectively. Cross-linked magnetic CSIS displayed higher adsorption capacity for Cu(2+) in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded cross-linked magnetic CSIS were regenerated with an efficiency of greater than 88% using 0.01-0.1M ethylendiamine tetraacetic acid (EDTA).

Adsorption of Cu(II), Hg(II), and Ni(II) ions by modified natural wool chelating fibers.

The graft copolymerization of ethyl acrylate (EA) onto natural wool fibers initiated by potassium persulphate and Mohrs salt redox initiator system in limited aqueous medium was carried out in heterogeneous media. Ester groups of the grafted copolymers were partially converted into hydrazide function groups followed by hydrazone formation through reaction with isatin. Also the application of the modified fibers for metal ion uptake was studied using Cu(II), Hg(II) and Ni(II). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

Immobilization of horseradish peroxidase on modified chitosan beads

A method has been developed to immobilize horseradish peroxidase (HRP) on modified chitosan beads by means of graft copolymerization of polyethylacrylate in presence of potassium persulphate and Mohrs salt redox initiator. The activity of free and immobilized HRP was studied. FTIR spectroscopy and scanning electron microscopy were used to characterize HRP immobilization. The efficiency of the immobilization was investigated by examining the relative enzymatic activity of free enzyme before and after the HRP immobilization. The obtained values were found to reach 98.4%. The results show that the optimum temperature of immobilized HRP was 45 degrees C, which was identical to that of free enzyme, and the immobilized HRP exhibited a higher relative activity than that of free HRP over 45 degrees C. The optimal pH for immobilized HRP was 10, which was higher than that of the free HRP (pH 9.0), and the immobilization resulted in stabilization of enzyme over a broader pH range. The apparent kinetic constant value (K(m)) of immobilized HRP was 3.784 mmol ml(-1), which was higher than that of free HRP. On the other hand, the activity of immobilized HRP decreased slowly against time when compared to that of the free HRP, and could retain 65.8% residual activity after 6 consecutive cycles.

Ionotropically cross-linked pH-sensitive IPN hydrogel matrices as potential carriers for intestine-specific oral delivery of protein drugs.

Background: The oral delivery of proteins and peptide drugs is considered a major challenge. These types of therapeutics are readily degraded, if taken orally, due to the harsh high acidity of stomach and enzymatic attack in the upper small intestinal tract. Methods: Water-soluble copolymers of sodium acrylate (AAs) grafted onto carboxymethyl cellulose (CMC) were prepared and characterized using Fourier transform spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained graft copolymers were then used in a combination with sodium alginate to develop a new series of pH-sensitive interpenetrating polymeric network (IPN) hydrogels through ionotropic gelation with divalent ions (Ca2+). Morphology of the developed hydrogels was investigated using SEM. Swelling characteristics, at distinct compositions, were also studied at 37°C in two consecutive buffer solutions of pH 2.1 and 7.4 (similar to that of gastric and intestinal fluids, respectively). The release profiles of bovine serum albumin, as a model protein, from test IPN hydrogel films were studied in simulated gastric and intestinal fluids. In addition, the drug release process was confirmed by means of SEM. Results: Swelling studies of the developed IPN hydrogels at different pH values confirmed their pH-sensitive nature. The equilibrium swelling extents of the hydrogels were found to be dependent on the grafting yield of CMC/AAs graft copolymer. The IPN hydrogels attained equilibrium swelling percentages in the range 445–740%. In addition, the amount of bovine serum albumin released within 2 hours in pH 2.1 was relatively low (less than 18.1%). This amount increased up to 68% after 8 hours in pH 7.4. Conclusions: From the obtained preliminary data, it seems that the IPN hydrogels developed in this contribution can be tailored to act as good potential carriers for oral delivery of protein drugs. These hydrogels showed a promising protection of protein drugs from the harsh acidity of stomach and, at the same time, they conferred sustained drug release in the intestinal fluid.

Grafting Study and Antifungal Activity of a Carboxymethyl Cellulose Derivative

Graft copolymerization of appropriate monomers onto cellulose and its derivatives can enhance their characteristics and consequently expand their potential applications. Carboxymethyl cellulose (CMC) was prepared and characterized by FTIR spectroscopy and XRD. Graft copolymerization of acrylic acid sodium salt (AAs) onto CMC using ammonium persulfate (APS) as a free radical initiator was carried out under nitrogen atmosphere in aqueous solution. Occurrence of grafting was confirmed by comparison of FTIR spectra of CMC and the graft copolymers as well as the XRD patterns and thermal analysis. The effects of concentration of AA, temperature, concentration of APS and reaction time on the grafting yield were investigated by determining the grafting percentage and grafting efficiency. With other conditions kept constant, the obtained optimum grafting conditions were: CMC = 0.2 g, [AAs] = 2 mM, [APS] = 7.5 mM, temperature = 70°C and reaction time = 2 h. A preliminary study was then carried out to evaluate the antifungal activity of the prepared graft copolymer. This preliminary investigation of the prepared graft copolymers showed that they may be tailored and exploited to expand the utilization of these systems in medical applications.

Enantiopure N-sulfonylamino alcohols and their copolymers as chiral auxiliaries for the highly enantioselective allylboration of aldehydes

Abstract Enantioselective synthesis of homoallylic alcohols by nucleophilic addition of chirally modified allylboron reagents to aldehydes was investigated. Reaction of enantiopure N -sulfonylamino alcohols ( 1a, 1b, 3a, 4a ) with triallylborane gave the chiral allylboration reagents. Aldehydes were converted to enantioenriched homoallylic alcohols with the reagents. Polymer-supported chiral allylboron reagents were also prepared from triallylborane and crosslinked polymers having chiral N -sulfonylamino alcohol moieties ( 5–8 ). These polymeric reagents reacted with aldehydes to give optically active homoallylic alcohols in high chemical yield with high enantioselectivities. Optical yield up to 92% ee was obtained by the use of polymeric chiral ligand 7 derived from d -camphor. The potential of this type of approach in asymmetric synthesis is discussed.

Application of Crosslinked Ionic Poly(Vinyl Alcohol) Nanogel as Adsorbents for Water Treatment

Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu2+) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu2+ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb2+) and cadmium (Cd2+) were tested. The maximum of Cu2+ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents.

Phase transfer catalyzed reactions of crosslinked chloromethylated polystyrene with vanillin

Abstract Chloromethylated polystyrene was reacted with vanillin under phase transfer catalyzed conditions. This reaction was performed under different conditions, including variations of the phase transfer catalysts, the reaction solvent, the type of base, the reaction time and temperature. In addition, the effect of the reaction technique (i.e., solid–liquid–liquid and solid–liquid–solid systems) on the reaction conversion was studied. Polymer-supported vanillin was evaluated for its utilization in polymer analogue conversions by performing condensation reactions of the aldehyde functionality with malononitrile, ethyl cyanoacetate, cyanoacetamide, cyanothioacetamide, 2-aminophenol, hydrazine hydrate and hydroxylamine hydrochloride. In all cases, the reactions were followed up by means of FTIR spectroscopic analysis.

Adsorption studies of Cu2+ onto poly (vinyl alcohol)/poly (acrylamide-co-N-isopropylacrylamide) core–shell nanogels synthesized through surfactant-free emulsion polymerization

ABSTRACT Poly (vinyl alcohol) (PVA) nanoparticle core and poly (acrylamide-co-N-isopropylacrylamide) P(AAm-co-NIPAm) hydrogel shell were fabricated to produce well-defined PVA/P(AAm-co-NIPAm) core–shell nanogels using Surfactant Free Emulsion Polymerization (SFEP). The nanogel was characterized by the FTIR, TEM TGA thermogram and SEM techniques. The adsorbent was utilized for Cu2+ removal from aqueous solution. Batch adsorption process indicated that 0.9 mol% PAAm nanogel exhibited higher adsorption affinity toward Cu2+. The kinetics parameters were investigated according to the pseudo-first-order, pseudo-second-order and intraparticle diffusion rate models. The adsorption equilibrium match with Langmuir adsorption isotherm rather than Freundlich isotherm. The Cu2+ loaded nanogels were effectively desorbed using 0.1 mol/l from HCl as stripping agent.

Studies on the alkylation of polymer-supported ambident anion derived from indane-1,3-dione

Abstract The behavior of polymer-supported ambident anions derived from indane-1,3-dione towards alkylation under various conditions has been studied. Particularly, factors that may affect the yields of isolated products and their compositions have been considered. Almost exclusively the di- C -alkylation product could be isolated after relatively long reaction time. This unusual tendency toward di- C -alkylation is extensively discussed on the basis of the effect of reduced reaction time on the composition of resulting products in addition to a comparative study of mono- C -versus di- C -alkylation in indane-1,3-dione with the acyclic analogous dibenzoylmethane.