Browsing by Author "Almarshed, Mawaheb Saleh Abdullah"

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Studies on synthesis and characterization of novel antimicrobial polymeric hydrogels modified with nano particles for dye removal from industrial wastewater
(Saudi Digital Library, 2019) Almarshed, Mawaheb Saleh Abdullah; Ahmed, Nadia Ahmed Mohamed
Chemical modification of chitosan via its cross linking with different concentrations of novel trimellitic anhydride isothiocyanate was successfully achieved for producing four novel cross linked chitosan hydrogels symbolized by H1, H2, H3, and H4 with increasing cross linking moiety contents, respectively. For further modification, the least cross linked chitosan hydrogel H1 matrix has been filled with three different concentrations of MWCNTs and with four different concentrations of SWCNTs. Their structure was proven via elemental analyses, FTIR spectroscopies, XRD patterns, SEM and TEM microscopies. They were found to be pH- and temperature-responsive materials. Their swell abilities appreciably depend on their cross linking moiety contents, CNTs concentrations, pH value and temperature of the medium. They are more potent against Bacillis subtilis, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Geotrichum candidum, Candida albicans, Aspergillus fumigatus, and Syncephalastrum racemosum than chitosan as illustrated by greater diameters of their inhibition zones and by decreased values of their minimum inhibitory concentrations. Their activities against microbes improved with rising the moiety contents of cross linking. They showed a better potency against Gram positive relative to Gram negative bacteria. Hydrogel H4 and H1/MWCNT composite derivatives showed activities similar or higher than that of the used standard antibiotics against some tested microbes. Thus, incorporation between chitosan, the functional groups of the cross linker and MWCNTs into the same structure is efficiently enhanced the features of chitosan. It is a good way for attaining adequate systems as antimicrobial agents that can be taken as promising candidates in biomedical fields. The hydrogels behave as polyanionic and poylcationic materials. Thus, they could potentially adsorb both the basic and the acidic dyes in various pH media for industrial wastewater treatment. Their adsorption capacity for both anionic Congo Red (CR) and cationic Basic Red v 12 (BR 12) dyes increased significantly with increasing the temperature and with increasing their cross linking moiety contents. Their adsorption capacity for CR dye increases significantly with decreasing the solution pH value. On the other hand, their adsorption capacity for BR 12 dye increases significantly with increasing the solution pH value. Their adsorption for both CR and BR 12 dyes at different temperatures and different dyes solution pH fitted to the kinetic model of pseudo second order. The isotherms of adsorption for CR and BR 12 dyes onto the hydrogels conform to the Langmuir isotherm model indicating the monolayer nature of adsorption. The adsorption of CR and BR 12 dyes onto the hydrogels is an endothermic process. The optimum adsorption capacity of H1/SWCNT3 composite was obtained at 25°C and the adsorption has impeded by temperature rising. It was found that at 25°C the capability of adsorption for BR 12 dye onto H1/SWCNT3 composite is greater by 1.8 times than that obtained onto the parent hydrogel H1. The optimum adsorption capacity of H1/SWCNT3 composite for BR 12 dye was obtained at pH 10. It was found that at pH 7 the adsorption capability for BR 12 dye onto H1/SWCNT3 composite is higher by 1.8 times than that obtained onto the parent hydrogel H1. The adsorption of BR 12 dye by H1/SWCNT3 composite at different temperatures and different dye solutions pH fitted to kinetic model of the pseudo second order. The adsorption isotherm for BR 12 dye by H1/SWCNT3 composite fitted to the Langmuir isotherm model indicating the monolayer nature of adsorption. BR 12 dye adsorption onto H1/SWCNT3 composite is an exothermic process. The regeneration and the reuse of the hydrogels were possible for both dyes.
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