Said S. Elkholy

Metal uptake by a novel bidentate thiosemicarbazide chelating polymer

1-Cyanoethanoyl-4-acryloyl thiosemicarbazide (CEATS) has been prepared and polymerized by a free radical mechanism. The polymer PCEATS has chelating affinity, and metal-uptake capacities were determined for the chlorides of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) in the pH range 1.04–6.0. The extraction experiments show high capacity for Cu(II), (0.26 mmol/g) at pH 5.34 and lower uptake capacities for the other divalent metal ions around pH 5 in buffered solutions, under noncompetitive conditions. However, competitive experiments, performed with solutions containing a mixture of metal chloride salts and acetate buffer, showed a high selectivity for Cu(II) and Cd(II) over other cations. Distribution coefficients determined for the polymer and the metal ions indicate that the Cu(II) complex is more stable than the Cd(II) are and suggest that the stability of the complex decreases rapidly with decreasing pH. Kinetic experiments have shown that uptake of Cu(II), is slow, with t 0.5 = 10 h. Ligand regeneration experiments for Cu(II)-loaded PCEATS performed with 2.00 M H2SO4 have shown that the capacity for Cu(II) stays at the same level after several cycles of consecutive loading and stripping, indicating that the polymer is chemically stable. ESR spectra of Cu(II)–CEATS resin show that there are two different coordination complexes present in the polymer. IR spectra of the Cu(II) complex confirms the bidentate behavior (S, O; N, O) of CEATS and PCEATS (it is supposed that the cations bridge vicinal CEATS ligands through S, O and N, O atoms); the acetate group completes the octahedral coordination. The obtained data suggest that the polymer behaves as a bidentate ligand via the thiocarbonyl, carbonyl and imide groups. PCEATS and its complexes have an inhibitory effect on both the bacterium Azotobacter and the fungus Fusarium oxysporium. The effect on the microorganisms is proportional to the amount of free ligand in the complex.

Chemical and Radiation-Induced Grafting of p-Carboxy N-Phenyl Maleimide onto Chitosan

Chitosan was grafted with p-carboxy N-phenyl maleimide (PCPM) using a redox initiator potassium persulfate (K2S2O8) and sodium bisulfite (NaHSO3) and also by γ irradiation. The effects of monomer concentration, initiator concentration, pH value, and temperature on the extent of grafting were studied. The grafting percentage reached maximum at 1.0 mol/l monomer concentration and an initiator mixture ratio of 0.004:0.004 mol/l of K2S2O8:NaHSO3 respectively. Maximum grafting percentage was achieved at 30.0 KGy using dioxane as solvent. The grafted chitosan samples were insoluble in all known solvents. The complexation of the grafted chitosan with Cd(II) ion at different pH has been investigated using atomic absorption spectrometry. The grafted samples show a higher chelation capacity than chitosan itself. Thermogravimetric analysis of grafted chitosan showed an enhancement of the thermal stability of the graft copolymers.

Grafting of 1-Cyanoethanoyl-4-acryloylthiosemicabazide onto Chitosan and Biocidal Activity of the Graft Copolymers

Chitosan was grafted with a novel monomer 1-Cyanoethanoyl-4-acryloylthiosemicabazide (CEATS). The graft copolymerization was conducted using potassium persulfate (K2S2O8) and sodium bisulfite (NaHSO3) as redox initiators. The grafted samples were characterized by FTIR spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. The data may indicate that grafting has occurred at the surface of chitosan. The grafted samples showed high water swelling. The antifungal behavior of chitosan and its graft copolymers was investigated in vitro and it has been found that grafting with CEATS noticeably enhances the antifungal activity.

The Antimicrobial Behavior of Polyelectrolyte Chitosan-Styrene Maleic Anhydride Nano Composites

A new antimicrobial polyelectrolyte polymer was prepared based on chitosan and alternating styrene maleic anhydride (SMA) copolymer. The SMA was subjected to alkaline hydrolysis, followed by blending with chitosan and chitosan in the nano form which has been prepared by self-assembly technique with particle size 46±0.08 nm. The composition was investigated and characterized by spectral and, thermogravimetric analysis, dynamic light scattering, and transmission electron microscopy. The nano polyelectrolyte complexes and composite were screened for their antimicrobial behavior and showed excellent antifungal as well as antibacterial efficacy against four bacterial and fungal strains. The hydrolyzed styrene maleic anhydride-nano-chitosan exhibited higher antimicrobial activity than the hydrolyzed styrene maleic anhydride-chitosan.