| On the basis of general processing methods of acidic waste water, the research progress of complex extraction technology for the treatment of organic carboxylic acids and their aqueous solutions was summarized in the paper. In view of this object, butyric acid, succinic acid and citric acid were selected typically as solutes. Tributyl Phosphate(TBP) and trialkylamine(with n-octanol and toluene as diluents) were chosen as complex agents. The binary and ternary mixed extractants with high efficiency were successfully selected out. The effects of complexing agent concentration, diluents concentration, the aqueous equilibrium pH value, temperature and the initial concentration of carboxylic acid on the extraction equilibrium have been systematically investigated. The regenerative conditions of complexing agents have also been studied. In the complex extraction of organic carboxylic acid with binary and ternary mixed extractants, orthogonal experiment results were analyzed with software STATISTICA. With infrared spectrum, the extraction mechanism of carboxylic acid has been studied. The empirical relation between distribution ratios and physical parameters has been correlated, and the chief effects of diluents during the extraction process have been explained. Combining chemical complexation and physics extraction of monobasic and polybasic carboxylic acid, the universal liquid-liquid equilibrium model with clear physical meaning was successfully induced. Distribution ratios of complex extraction of different operation conditions were first forecasted with BP neural networks. Finally we got the complex extractants applied to industry and technological conditions under which complex extraction technology was used to deal with organic carboxylic acid solutes from dilute solutions.The experimental results are as follows: (l)TBP was suitable to monobasic carboxylic acid solutes (such as butyric acid), but was not suitable to polybasic carboxylic acid solutes (such as succinic acid and citric acid). Because lewis alkalinity of trialkylamine was stronger than that of TBP, and the former presented a much better distribution ratio than TBP. (2) To butyric acid, when TBP (solved in n-octanol) was used as complexing agent, the mixed organic solvent formed by 70.0% TBP-30.0% n-octanol (volume fraction) was chosen as extractant. To butyric acid, succinic acid and citric acid, when trialkylamine (solved in n-octanol and toluene) was used as complexing agent, ternary extractants which presented a higher distribution ratio had been successfully selected out from the factors of price, efficiency and fluidity of extractant through a lot of experiments. To butyric acid, mixed organic solvent formedby 20.0% trialkylamine-20.0% n-octanol -60.0% toluene (volume fraction) was selected out; To succinic acid and citric acid, mixed organic solvent formed by 20.0% trialkylamine-50.0% n-octanol-30.0% toluene (volume fraction) was selected out. (3) The change of enthalpy in the extraction of butyric acid with TBP as well as those of butyric acid, succinic acid and citric acid with trialkylamine were -7.03kJ/mol, -28.71kJ/mol, -46.01 kJ/mol, -37.93kJ/mol respectively. The negative values meant that the above mentioned extraction processes were exothermal processes. Therefore, the extraction operation should be held under the normal temperature. (4) To given composition of extractant and concentration of carboxylic acid, the mathematical modelcorrelated distribution ratio with [H+] has been induced. When pH value was low,equilibrium distribution ratios were large, and with the increasing of pH value, equilibrium distribution ratio obviously decreased. When pH value reached a certain value, distribution ratio became 0 or around. (5) Extractants were regenerated by means of NaOH solution. The effects of concentration of NaOH, phase ratio, carboxylic acid concentration on reextraction have been studied, and the results conveyed that NaOH solution was very suitable to the reextraction of carboxylic acid. (6) The complex compositions in th...
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