Synthesis And Application Of Carbamate Starch Derivatives

Starch carbamate is prepared by reacting starch with urea using a solid-state technique and possesses certain property because of the introduction of amide groups. In this thesis, ammonium chloride with low toxicity was chosen to be catalyst, and higher degree of substitution (DS) and higher reaction efficiency of urea were achieved than the traditional process using copper chloride as catalyst. This provides chances for industrial production and application of this low-cost starch carbamate. The best reaction condition was gained from orthogonal tests and the reaction was greatly affected by a little water.Starch phosphate is widely used in various aspects, but conventional hemi-dry process using orthophosphates as ester agents has some drawbacks, such as low reaction efficiency and wastewater pollution. In this thesis, starch phosphate-carbamate (SPC) was prepared by reacting phosphoric acid, urea and starch using a solid-state technique. High reaction efficiency can be achieved using ester agents with low toxicity. This process is simple, green and easy to prepare products with high DS. The DS of phosphate and carbamate groups can be adjusted from 0 to 1.2 and from 0 to 0.4, respectively, by adjusting the molar ratio of materials, and the efficiency of phosphoric acid is over 95% when the DS of phosphate groups varies from 0 to 0.7. Some analytical techniques, such as IR, ¹³C NMR, ³¹P NMR and SEM, were applied for the analysis of the products.Ion exchange method was built to analysis the nitrogen in SPC derivatives, which exists in two forms: amide and ammonium. But there is no paper to give detailed investigation about the difference of two parts of nitrogen and the previous paper only gave total nitrogen content. Ion exchange resin was used to exchange the ammonium in the starch phosphate-carbamate, and then Kjeldahl method was used to determine the content of amide. The ion exchange method was proved to be a universal and feasible method using starch carbamate and starch phosphate. This method found the basis to gain the exact active groups' content of related starch derivatives.Crosslinked starch phosphate carbamates (CSPC) were designed and prepared as adsorbents. Adsorption of Cu(II) and Pb(II) ions on CSPC was thoroughly studied. The adsorption is endothermic, spontaneous in nature and the adsorption equilibrium data correlate well with the Langmuir isotherm model. The methods on adsorption thermodynamic studies for solid adsorbents in solution were summarized and evaluated according to the adsorption equilibrium data of CSPC, which can provide the theory directionfor choosing methods on adsorption thermodynamic studies. IR spectrum and scanning electron microscopy (SEM) was used to investigate the changes of the CSPC before and after adsorption, and the adsorption mechanism was explained. Good reusability and high desorption efficiency were proved according to the repeated adsorption/desorption cycles experiments. CSPC shows higher adsorption capacity and rate than other reported adsorbents, and has the possibility of being an effective adsorbent for industrial use.Starch carbamates were prepared with original cornstarch, oxided starch and hydrolyzed starch, and used to flocculate kaolin suspension. The results show that flocculation efficiency increases with increasing DS of starch carbamates, and decreases with the ionic strength. The best flocculation efficiency was achieved at pH 6. Starch carbamate with low-cost materials, simple preparation process, and good flocculation efficiency is a promising flocculant.