Preparation Of Chitosan Guandine And Its Application In Water Treatment

Guanidine is a kind of strong organic alkali. It has high stability and good biocompatibility. It has been widely used in medicine, fungicide, surfactant, etc. Guanidine has catalytic action which can be used as alkaline auxiliary agents and catalysts in many synthesis reactions. Recently, guanidine as the medical sterilization appliction has been made widespread interests. In addition, guanidine can be chelated with metal ions. Chitosan is a biocompatible polysaccharide obtained from deacetylation of chitin. It has biocompatibility, excellent hydrophilicity, nontoxic and biodegradable performance. It can chemically or physically entrap various metal ions due to the presence of amine and hydroxyl groups that can serve as the chelating and reaction sites. Therefore, chitosan presents as a very promising material for chelating resins. In this paper, the guanidinated modification of chitosan has been studied and a series of guanidine salts, such as chitosan guanidine, chitosan biguanidine and composites have been prepared. Their applications to the adsorption of Chromium(VI) or MO have been studied. The major results were as follows:1. The preparation of chitosan biguanidine and its application to adsorption of Chromium(VI) from aqueous solutionUsing chitosan and dicyanodiamine as raw materials, chitosan biguanidine hydrochloride was prepared under microwave radiation and chitosan modified adsorbent(GCB) was further prepared by the cross-linked reaction of glutaraldehyde with chitosan biguanidine hydrochloride. The adsorbent was characterized by FTIR, SEM and TGA. The results indicated that GCB had larger surface area that chitosan. The adsorption of Cr(VI) on GCB was systematically studies. The results showed that the maximum adsorption capacity was found at p H 3.6. Adsorption kinetics followed pseudo-second order model. The adsorption isothermic results showed that the isotherm followed the Langmuir isotherm model and the maximum capacity was calculated to be 202.4mg·g-1 at 30 oC. The thermodynamic results manifested that the adsorption was an endothermic and spontaneous chemical process. The coexisting SO42-for the adsorption of Cr(VI) on GCB had greater inhibitory effect than NO3-, Cl-, indicating that GCB absorbed Cr(VI) mainly by electrostatic interaction. The GCB could effectively removed the Cr(VI) in aqueous and been regenerated with 1.5 mol·L-1 KCl / 1 mol·L-1.2. Adsorption of Chromium(VI) on chitosan guanidine nanoparticlesThiourea trioxide was previously synthesized by H2O2 oxidation reaction of thiourea. Chitosan guanidine nanoparticles adsorbent(GCH1) was further prepared by the reaction of chitosan with thiourea trioxide. The adsorbent was characterized by FTIR, XRD, SEM, and TGA. The average size of chitosan guanidine nanoparticles was estimated at 50 nm. The results showed that maximum adsorption capacity was found at p H=3. The kinetic followed the pseudo-second order model. The adsorption date could be well fitted by Langmuir model and the maximum uptake from the Langmuir model was calculated at 155.6 mg·g-1 which was less than that of GCB. The thermodynamic parameters, DHa>0, DGa<0 indicated that the adsorption was an endothermic and spontaneous chemical process. The coexisting anion SO42-or Cl- showed inhibitory effect on the adsorption and the influence of SO42-was higher than that of Cl-. GCH1 can be regenerated by using 1.5 mol·L-1 KCl / 1 mol·L-1 KOH. The Cr(VI) uptake of the adsorber after five asorbed and regenerated recycles keeped still over 86% of the first uptake.3. Preparation of Fe3O4/chitosan-biguanidine and its application on the adsorption of Methyl OrangeFe3O4 nanoparticles were prepared by the conventional co-precipitation method of Fe SO4 and Fe2(SO4)3(mole ratio=1:2), with the addition of concentrated aqueous ammonia. Fe3O4 nanoparticles and chitosan were crosslinked by glutaraldehyde. The composite was obtained and characterized by SEM. It was found that the maximum adsorption capacity was at p H=5. Adsorption kinetics followed pseudo-second order model. Results showed that the adsorption was followed the Langmuir adsorption isotherm and the maximum uptake was 429.9 mg·g-1. The thermodynamic results indicated that the adsorption was an endothermic(DHa=5.09 k J·mol-1) and spontaneous chemical process.