Dissertation > Environmental science, safety science > The basic theory for the Environment and Science > Environmental Chemistry > Environmental Analytical Chemistry

Hydrolysis Behavior of Diquat in Aquatic Environment

Author PengJuanYing
Tutor YangRenBin
School Hunan Agricultural University
Course Environmental Engineering
Keywords Diquat Hydrolysis Environmental factors Surfactant Inorganic salts Degradation model
CLC X132
Type Master's thesis
Year 2007
Downloads 141
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Diquat is an efficient, broad-spectrum of bipyridyl herbicides, few reports about its chemical behavior in water environment, this paper, through the study of diquat hydrolysis behavior, including the coexistence of environmental factors and waters its hydrolysis, and the establishment of diquat in the river water degradation model, evaluated an enemy of the rational use of paraquat, diquat its environmental safety and forecast river pollution levels to provide a scientific basis. Thesis reads as follows: The first chapter is the introduction, the main hydrolysis behavior of pesticides in the environment related concepts, theories, and research status at home and abroad, and diquat research progress in a brief introduction and commentary also pointed the content and significance of this study. Chapter II study of environmental factors the paraquat hydrolysis behavior of the enemy, and the results show that: (1) Diquat degradation in water can be a reaction rate equation fitting. Is relatively stable in acidic and neutral conditions, but is easily decomposed under alkaline conditions; The diquat hydrolysis half were 238.97,231.05,22.00 d in the pH of 5,7,9 a buffer solution. (2) a Diquat the hydrolysis rate with increasing temperature to accelerate diquat 15,25,35 ℃ temperature pH = 9 buffer solution, the hydrolysis half-life were 36.28d, 22.00d and 14.71d temperature effect coefficient from 1.50 to 1.64. (3) In the conditions of a pH of 7 and 9, the hydrolysis of diquat activation energy is relatively small, respectively for 21.33kJ · mol -1 -1 and 25.89kJ · mol -1 -1 , and the absolute value of the entropy of activation of diquat hydrolysis reaction with temperature increase, showed significant correlation between the average entropy of activation-191.83J · (mol · K) -1 . (4) compared with the pH and temperature, and the the the water enemy paraquat hydrolysis reaction of impact is relatively small. The variance analysis of the experimental results showed that the different sources of water body is the enemy paraquat hydrolysis reaction throughout the pilot phase did not show significant differences. Chapter waters enemy the paraquat hydrolysis behavior of a coexistence, the results show that: (1) the impact of different types of surfactant enemy of paraquat hydrolysis behavior is different. Anionic surface active agent can promote the hydrolysis of diquat SDBS SDBS was added by a not-increased to 300 mg · L -1 , diquat hydrolysis rate constant K values ??respectively increases about 11 times; diquat the half-life is shortened from 192.54d to 16.70d; cationic surfactant CTAB is slowed diquat hydrolysis, the concentration of CTAB was never added increased to 1200 mg · L -1 , a Diquat the hydrolysis rate is reduced to 0.0036d -1 0.0018d -1 , the half-life of 192.54d extend to 385.08d; non-ionic surfactant TW-80 had no significant effect on the enemy paraquat hydrolysis. (2) add to diquat aqueous solution of a strong acid and alkali salt (NaCl the MgCl 2 the CaCl 2 the NaNO 3 ), salting the role of the enemy paraquat hydrolysis inhibition when NaCl, MgCl or 2 , CaCl , 2 , the NaNO 3 solution concentration by not add increased to 1 mol · L -1 , diquat hydrolysis half-life was prolonged by 2.59%, 38.34%, 43.52%, 19.69%; When you add a strong base weak acid salt (NaHCO 3 , Mg (HCO 3 ) 2 , Ca (HCO 3 ) 2 ), Because of the water environment, strong base weak acid saline solution alkaline hydrolysis of paraquat the enemy a catalytic role, when NaHCO 3 , Mg (HCO 3 ) increased to 1 mol · L -1 2 , Ca (the HCO 3 ) 2 solution concentration by not added, the enemy paraquat hydrolysis rate increased 23.67,29.83,33.67 times; When adding a strong acid weak base salt (MgNO 3 , CaNO 3 ), saline solution of a strong acid and a weak base the water environment acidic to the enemy paraquat hydrolysis inhibition Mg (NO 3 ) 2 , Ca (NO 3 ) < sub> 2 solution concentration was not added to 1 mol · L -1 , a diquat hydrolysis half-life was prolonged by 89.12% and 49.74%. Chapter IV using quadratic regression orthogonal rotary diquat in the river water degradation model, and the model is a preliminary analysis and partial validation. The results show that diquat degradation in the river model: y =-13.006-0.001x 1 2 -0.006x 2 2 -0.119 x 3 2 0.003x 1 x 2 -0.015x 1 x 3 -0.005x 2 x 3 0.118x 1 0.128x 2 < / sub> 3.500x 3 , the range of variables: x 1 (T / ° C) = 16.60 ~ 33.40; x 2 (t / d) = 6.70 ~ 23.30; x 3 (C / mg · L -1 ) = 6.80 ~ 13.60. Significant F test results F 1 = 2.715 0.05 (5,8) = 3.69, F 2 = 112.011> F 0.10 (9,13) = 2.16, shows that the regression equation with actual fitting better. The preliminary analysis of the model and the partial validation shows that the model established in this study can be used for a preliminary forecast of diquat river pollution levels. Chapter V of this research work are summarized and discussed and put forward the innovation of this study and areas for further research content.

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