| In the article, Carboxymethyl chitosan (CMC) was prepared by a new method of improving temperature stage by stage and two-step alkalization. The product can dissolve in the water easily. We carefully studied the new method that combined effectly improving temperature stage by stage with two-step alkalization. The factors, such as the amounts of alkali and chloroacetic acid, the volumes of isopropyl alcohol, reaction temperature, reaction time, etc., influencing the yield, degree of substitution (DS) and intrinsic viscosity were respectively investigated and discussed confirmedly. And, we got the best conditions of preparing O,N -CMC by single factor tests and tests that was handed in. In the best conditions the viscidity and yield of that product were both better than that of them in the conventional methods, the cost of product was also decreased. And, the CMC products were characterized for DS, viscidity, yield, IR spectra, etc., respectively. Finally, for testing the practicability of CMC, the tests, which CMC was used in the wastewater including paint, were carried out. The result of the CMC in the treatment is better than that of conditional matters in that treatment at the same conditions. So the O,N-CMC is better useful for practicability.At last, the optimized reaction conditions were obtained as: m (chitosan) : m (monochloroacetic acid) : m(sodium hydroxide) = 1:4.4:4.4, reaction temperature 60 ℃, reaction time 4hr, and amounts of isopropyl alcohol 50ml, that is, the ratio of Volume/weight to chitosan was 10:1 respectively. In comparison with the conventional methods, the method showed remarkable increase in the yield and DS values by 15% more and 8% more respectively and decreased the cost of preparation by 10% more. So that had actual meaning for production. Under the optimizedconditions, the yield and DS reached as high as 94.2% and 1.58 respectively, and viscosity could reach 15mPa ? s which was better in the same products.The study of factors influencing DS showed that the amounts of alkali and chloroacetic acid were the key factors influencing the DS. The DS increased and then followed by a decrease with the increase in the amount of alkali > monochloroacetic acid and the reaction temperature.The study of factors influencing definite viscosity showed that the amounts of alkali and chloroacetic acid, and reaction temperature were the key factors influencing the viscosity. Viscosity increased and then followed by a decrease with increasing amounts of alkali, chloroacetic acid. After reached the reaction temperature, the viscosity would decrease sharply with the increase in reaction temperature. Besides, when the amounts of alkali and chloroacetic acid were steady relatively, the reaction temperature and time were more important.The study of factors influencing yield indicated that the amounts of alkali, chloroacetic acid, and reaction temperature were the key factors influencing the yield. The yield increased and then followed by a decrease with increasing amounts of alkali, chloroacetic acid. After reached the reaction temperature, the yield would decrease with the increase in reaction temperature, but before that, the yield would increase; With the increase in reaction time, the yield would increase, but would reach the maximum by supposition. The IR spectra of CMC indicated that the product was O,N -CMC and the carboxymethylation mainly occurred on the oxygen (O) position and few occurred on the amino (N) position.In the oil paint wastewater, the best amount of O,N -CMC which was 40mg/l in that wastewater was determined. By the tests that CMC was used we found that it could get rid of COD, SS and color matter perfectly. The removal rates of them were 89. 2%, 99. 8%, 83. 8%. And the quality of treated oil paint wastewater met the national first-degree drainage standard. This flocculant is of characteristics of good quality and environmental friendship.
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