الفهرس 
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Abstract
The present work focuses on the modification of chitosan with isonicotinic aldehyde to give hydrogel I or with epichlorohydrin or sodium tripolyphosphate via ionotropic gelation processes under the same reaction conditions to give hydrogel Ie, and nanohydrogels II, IIe respectively. Chitosan was modified with bentonite or nano-bentonite to give chitosan composite and nanocomposite derivatives hydrogels III and IV respectively, however chemical modification of chitosan with isonicotinic aldehyde via Schiff base formation in presence of bentonite or nanobentonite yielded chitosan composite and nanocomposite derivative hydrogels IIIn and IVn respectively. The prepared hydrogels were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (X-Ray), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning electron microscopy (SEM), and swelling behavior. Adsorption studies for removal of heavy metal ions from aqueous media and the biological activity for the new hydrogels were studied. Results of evaluation of the prepared chitosan derivatives hydrogel for metal ions uptake showed that the maximum adsorption capacity amounted to 68 and 22 mg/l and the highest efficiency for adsorption of cobalt and mercuric ions from aqueous solution by hydrogel IVn at 10 h (93.2%) and (97.8%) respectively, whereas the adsorption capacity of hydrogel IVn increased with the increase of the initial concentration ofheavy metals ions ranging from 0.4 to 1 g/l. However, modified chitosan derivative hydrogels IIIn and IVn showed remarkable MIC and MBC towards Gram-positive (B. subtilis) (19.5, 38) μg/ml compared to the standard antibiotic Ciprofloxacin (19, 38) μg/ml respectively.