| China is the biggest country in the textile industrial in the world, and the textile wastewater takes a great proportion in the industry wastewater, the discharge is 14.13×108t/a , which is the the fifth in industrial wastewater statistics , While the emission of printing and dyeing wastewater is about 11.3×108t /a (which occupys 80% of the textile wastewater), discharging 300×104～400×104t every day. With high water volume, complicated water quality, rich content in organic substances, difficult biodegradability, high basic and colority, etc, dyeing wastewater can cause heavy pollution to the water environment. There are a lot of methods treating dyeing wastewater, but the effect is not the same. Adsorption method is very common in the decoloration techniques of dyeing wasterwater. Recently, various kinds of adsorbents have been developed in the treatment of dyeing wasterwater and a good effect has been made.Chitosan, namedβ-(1→4)-2-amino-2-deoxy-D-glucan, contains many–OH and -NH2 groups, which has a strong adsorption of reactive dyes, direct dyes and acid dyes. In addition, with rich sources, it is non-toxic, antibacterial, biodegradability and possible on industrial applications in future. The derivative of chitosan has a good adsorption capacity on dyes, and the main adsorption mechanism is ion exchange, hydrogen bonding effect and physical adsorption which was formed by the internal network structures of the polymers.Acid bordeaux B(ABB) and nylosan yellow N-3RL (NYN) are two kinds of acid dyes imported from abroad, and it is not found any report on the adsorption of these two kinds of dyes by chitosan at home and abroad.This study uses chitosan as the adsorbent, then has an investigatation on the the adsorption properties of these two dyes from water by static adsorption test. To get the best adsorption conditions, it preliminarily discusses the affect on adsorpt effect by the deacelation degree, particle size, dosage of chitosan, contact time, temperature, pH value and stirring speed, then determines the adsorption capacity and type according to Adsorption Isotherm. The result shows that Under the initial concentration of dye waste water 100 mg / L and volume 50 mL , the optimum adsorption conditions of the two dye waste water by chitosan are gained as follows: the deacetylating degree of chitosan is 75%, the particle size of chitosan is 0.054~0.076mm, the dosage of adsobent is 20.0mg , the stirring time is 2.0 hours, the pH value is 6, the stirring speed is 400r/min and the temperature is 10~30℃for ABB, 20~50℃for NYN. Under the optimum adsorption conditions, the adsorption capacity of ABB and NYN are 270.3mg/g和666.7mg/g respectively, and the adsorption process of ABB and NYN fits well with both Freundlich model and Langmuir modelTo enhance the acid resistance of chitosan for high adsorption ability on dyes under low pH value , chitosan beads are prepared as adsorbent, using chitosan as the material, sodium tripolyphosphate(TPP) and epichlorohydrin(ECH) as the cross-linking reagent, and Orthogonal Test Method is used to optimize the preparation conditions. Then, by the chitosan beads, the adsorption properties of two kinds of acid dye, acid bordeaux B(ABB) and nylosan yellow N-3RL(NYN) from water is investigated, and then the regeneration method of chitosan beads is discussed. It is found that the best preparation conditions are gained as follows: the CS mass concentration is 1%, TPP mass concentration is 1%, nECH:ncs=1:1, the crosslinking temperature is 70℃, and time is 6h; the optimum adsorption conditions for two kinds of dyes by chitosan beads are obtained as follows: the particle size of chitosan beads is 0.5mm, the dosage is 20.0mg, the contact time is 16 hours, the pH value is 3, the temperature is 20℃for ABB,30~50℃for NYN, the oscillating rate is 150r/min. Under the optimum adsorption conditions, the adsorption process of ABB and NYN fits well with both Freundlich model and Langmuir model, and the saturated adsorption capacity of ABB and NYN are 714.29mg/g and 769.23mg/g, which exceed the saturated adsorption capacity by chitosan 443.99mg/g,102.53mg/g respectively.The saturated chitosan beads are desorbed by 0.01mol/L NaOH, the regeneration rate is 99.08%,99.35% for each dye, and the beads can be used repeatedly which will reduce the decoloration cost.
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