| The separation technique of extraction based on reversible chemical complexation has high capacity and selectivity for separating the polar organic species from dilute solution.According to the principles of reversible reactive extraction and wide literature survey, Trialkylphosphine-oxide (TRPO) was selected as a typical extractant, kerosene and 1-octanol as diluents, o-Aminophenol (OAP), m-Aminophenol (MAP) and p-Aminophenol (PAP) as solutes extracted. Extraction equilibrium has been studied detailedly and the influences of complex reagent concentration (B0), pH value of aqueous solutions and diluents on distribution ratio D have been discussed. Results show that D increases with the increase of B0, and a maximum D appears in neutral pH. The non-ploar diluents are more favorable for extraction of aminophenols using TRPO.With the FT-IR spectroscopy, the effect of aqueous pH on the complexes structure has been discussed. The complexes structure and the reactive mechanism have also been investigated. IR spectra indicate that the complexes structure is not related to aqueous pH; TRPO mainly reacts with neutral aminophenol and the reaction point is on -OH group; hydrogen bonds may form between TRPO and polar diluents 1-octanol.By using mass action law on TRPO-diluents-Aminophenol system, the expression of equilibrium distribution ratios, including chemical complexing and physical dissolving simultaneously, has been proposed. It reveals that the simulation precision based on the model is satisfied.On the basis of the systemic experimental studies on the extraction of aminophenols using TRPO, influences of the aminophenols'pKa and LogP and the kind of diluents on D have been discussed. It shows that pKa is the key factor which affects D in TRPO/kerosene, while the effect of LogP is not significant; in TRPO/1-octanol, pKa, LogP and hydrogen bonds between TRPO and 1-octanol are all important to the equilibrium, and the hydrogen bonds is the key factor which affects D.
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