SynopsisEquilibrium isotherms have been studied for the adsorption of four dyestuffs, namely, Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 84, onto chitin. Langmuir and Freundlich constants have been determined and the effects of chitin particle size and solution temperature have been investigated. Theoretical isotherms have been compared with experimental data and good agreement was obtained using a composite isotherm of the general form: Ye = XJ(1 +&' em) , where i, j , and m are constants.
The ability of chitosan, prepared from waste prawn shell, to sorb copper (II) ions from aqueous solutions has been studied. Equilibrium studies show that chitosan has a maximum sorption capacity for copper ions of about 40mg/g chitosan. The mass transport characteristics have been investigated by monitoring the kinetics in an agitated batch adsorber. An external mass transfer coefficient and an intraparticle diffusion rate parameter have been determined for a number of system variables including agitation, initial copper ion concentration, chitosan mass, chitosan particle size and solution temperature.
SynopsisChitosan has been prepared from prawn shell and crab shell chitin. The molecular weight of the material derived from prawn shells is higher than that obtained from crab shell. The molecular weight, tensile strength, elongation at the break, and hydrophilic properties of chitosan are extremely dependent on the degree of deacetylation achieved when chitin is hydrolyzed to chitasan. Graft copolymers have been prepared with chitosan and a series of vinyl monomers using both heterogeneous and homogeneous reaction conditions. The hydrophilic properties of chit-can be modified by blending with poly(viny1 alcohol).
EXPERIMENTALChitosan was prepared from chitin derived from two sources, namely from prawn shells (PS) and crab shells obtained from Sigma Chemicals (SG). The crude prawn waste (10 g) was washed and dried as described previ~usly,~ and sieved to give a particle size range of 500-700 pm. The ground shells were treated with four successive portions of 3% sodium hydroxide solution at a liquor ratio of 6 : 1, and at a temperature of 70°C, with rinsing between each treatment. The first two treatments were for 15 min each, and the last two for
SYNOPSISChitin was isolated from prawn shells, and chitosan was prepared from it. The degree of N-deacetylation and the molecular weight were determined using IR spectroscopy and viscometry, respectively. A series of different modified chitosan membranes were prepared by blending with polyvinylpyrrolidone ( PVP ) . These membranes were characterized by various techniques, including differential scanning calorimetry (DSC ) , wide-angle X-ray diffractometry ( WAXD ) , and tensile testing. The physical, thermal, and mechanical properties were evaluated, and the change in these properties upon the addition of PVP into the blends has been discussed in terms of the amorphous and hydrophilic nature of PVP. Hydrophilicity of the blends increases due to the presence of PVP in the chitosan substrate. This helps in breaking the hydrogen bonds in between chitosan molecules and causes the blends to swell in three dimensions.
SynopsisChitin has the ability to adsorb substantial quantities of dyestuffs from aqueous solutions. Consequently, it may be a useful adsorbent for effluent treatment from textile mills. The design procedures for batch and continuous fixed bed adsorption columns have been investigated for four dyestuffs, namely, CI Acid Blue 25 (Telon Blue ANL, Bayer), CI Acid Blue 158 (Neolan Blue 29, Ciba Geigy) CI Mordant Yellow 5 (Eriochrome Flavine A, Ciba Geigy), and CI Dirert Red 84 (Solophenyl Brown 3RL, Ciba Geigy). The main fixed bed system variables studied are bed height, dye flow rate, and chitin particle size, and these effects have been incorporated into a simplified design model.
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