EXTRACTION EQUILIBRIUM OFp-AMINOPHENOL WITH TRPO
Extraction equilibrium behavior of p-aminophenol is studied by using TRPO as extractant,and n-octanol or heptane as diluent.The distribution coefficient,D,is measured at various pH values.Mathematics models are proposed to describe the equilibrium behavior based on the physical extraction and reactive extraction of solvent.Results show that neutral p-aminophenol is hydrogen bonded and solvated to TRPO into the organic phase,and D value depends on the fraction of neutral p-aminophenol and TRPO concentration,but does not depend on the diluents apparently.The apparent reactive extraction constant,K,is almost constant in various solvents (about 10 with 10% deviation) except for 20%TRPO/n-octanol condition.The physical distribution constant,m,increased with TRPO concentration,and equivalent to additive of the physical extraction ability of diluent and TRPO.p-Aminophenol can be extracted with both acidic and basic extractants efficiently,the extraction ability shows the order of di(2-ethylhexyl)phosphoric acidTRPOAlamine 336,and their efficient pH region is 2-3,4-5, and 6.5-7.5 respectively.When extraction method is used to separate p-aminophenol solution,the extractant should be selected based on pH value of the practical solution to avoid the adverse effect of salt produced from adjusting pH.