Complexation Extraction Of Aminophenol From Its Dilute Solution

The extraction method based on reversible chemical complexation is highlyeffective and selective for separation polar organic solutes from dilute solution. On thebasis of largely literature survey, di(2-ethylhexyl)phosphate(D2EHPA) and tributylphosphate(TBP) were selected as a typical extractant, as well as o-aminophenol,m-aminophenol, and p-aminophenol, were used as solutes extracted. Five dilutes,1-octanol, 2-octanol, chloroform, kerosene, carbon tetrachloride were investigated fortheir abilities to improve extraction properties of D2EHPA and TBP. The effects ofcomplexing agent concentration, the polarity and concentration of diluents, the initialconcentration of solute and the aqueous equilibrium pH on the extraction equilibriumhave been systematically investigated. The effects of aqueous equilibrium pH on thestructure of the complex were discussed. The models for describing the extractionequilibrium that include chemical complexation and physical dissolving simultaneouslyby using mass action law to D2EHPA-aminophenol and TBP-aminophenol wereproposed. With the FT-IR spectroscopy, the spectra of organic phase loaded with aminophenolare determined. These researches show that pH values of system and concentration ofcomplexing agent were mostly factor on extraction equilibrium. Species andconcentration of diluted agents have definite factor on distribution ratio. The moreinitial concentration of aminophenol is, the more the distribution ratio is. There aretwo courses in the extraction process: ion-association and ion-transfered in the D2EHPA-aminphonel, but hydrogen-bond complexation in TBP-aminophenol. Through research on aminophenol extracted with D2EHPA-phosphate and TBP,the characteristics (structure, pKa, pKb, LogP) of amphoteric organic compound, and thefactors of solvent and hydrogen bonds were discussed on extraction equilibrium. Theseresearches show that hydrophobicity parameter is mostly factor on extractionequilibrium. Electronic parameter pKa has a big factor on extraction systems of TBP, buta less factor on extraction systems of D2EHPA. Because there is hydrogen bondbetween chloroform and TBP, it reduces extraction of aminophenol with TBP, sochloroform as dilute agent don't suit in this research. "pH swing effect" is a simple method that it is able to make complexing agentregenerated. Sulfuric acid was selected as regeneration agent on the basis of the soluteand process the part of D2EHPA and TBP systems. The result is satisfying.