Synthesis And Cationization Modification Of Dicarboxyl Cellulose-based Flocculant

Given a variety of wastewater treatment processes, flocculation is an effective and especially economical technique which plays animportant role in removal of suspended particles, dyes and heavy metals. Chemicals used for flocculation are called flocculants. They can be mainly divided into two main categories: synthetic and natural polymer based flocculants. At present, syntheticflocculants are widely used in wastewater treatment due to their mature production process and excellent flocculation performance. But there are some risks for the synthesis and applications ofthese synthetic flocculants. Some petroleum based monomers contained in synthetic flocculants hold potential toxicity to soil. Their non-biodegradability causes more serious problems to natural environment. In recent years, due to the increasing demand for environ-mentally friendly and safety, considerable attentions are paid to natural polymers which possess positive characteristics ofrenewable, non-toxic, biodegradable and highly reactive.In this work, we took the most abundant natural polymer cellulose in the world as a basic raw material to produce eco-friendlyfunctional materials and chemicals. A series of natural dicarboxyl cellulose flocculants(DCCs) were one-step synthesized via Schiff-base route. At first, NaOH/Urea solution was employed to dissolve the cellulose pulp, and then applied one of the four factors three levels orthogonal experiments to optimize the content of aldehyde. Therefore, preparation of aldehyde group to get the optimal process is: Reaction temperature is 55℃, Reaction time is 3 hours, Sodium periodate relavtive to cellulose weight ratio is 1:1, the concentration of a solution of cellulose was 2%. The resultant product had 1.24 mmol/g aldehyde group content of dialdehyde cellulose. Then, in the original system, we continued to use the remants of urea and sodium hydroxide to react, relying on different hydrolysis time to optimize the content of carboxyl group. Finally, we got five kinds of carboxyl cellulose products: 0.2, 0.6, 0.96, 1.01 and 1.24 mmol/g.By infrared spectroscopy, nuclear magnetic resonance(H NMR and C NMR) to verify the molecular structure of cellulose, thermogravimetric analysis, scanning electron microscope and XRD to explore the morphology and physically properties change of product. Finally dicarboxyl cellulose products was applied in the field of flocculation, and through the experiment we found out dicarboxyl cellulose had excellent flocculation performance, even better than the business of cationic polyacrylamide and polyaluminium chlori de for papermaking wastewater. Thus we could take place of conventional syntheticflocculants to keep safety and of sustainable development environment.Then we modified of dicarboxyl cellulose, by changing the molar ratio of anhydroglucose unit in cellulose to(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride(CTA), to obtain of different degree of substitution of cationic dicarboxyl cellulose.Under the certain reaction temperature 60 ℃, under a certain reaction time of 8 hours, three different substitution degree of the products were synthesized.With the increase of dosage of CTA, substitution degree increased, Zeta potential was also rised.Through infrared spectrum to observe the change of the molecular structure and the scanning electron microscope observation the change of the fiber morphology.We found these three kinds of product had excellent flocculation performance, but under alkaline condition, the flocculation performance became poor or even disappeared. Finally applying these products to industrial dyeing wastewater, through the orthogonal experiment of optimization, we determined the optimum flocculation process. The results showed that cationic dicarboxyl cellulose had an excellently flocculation performance on industrial dyeing wastewater.