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In this work, the reactive extraction equilibrium of p-nitrophenol (PNP) using tributylphosphate (TBP) dissolved in solvent naphtha and n-octanol has been studied, respectively. The effects of equilibrium pH (pHeq), initial TBP, and PNP concentrations on the distribution ratio (D) and the degree of extraction were discussed. The TBP/solvent naphtha showed higher D values than that of TBP/n-octanol. The larger D values were also observed at pHeq in the range of 2–5.5. pHeq had negligible influences on the structure of TBP/PNP complexes based on IR spectra analysis. TBP mainly reacted with the neutral form of PNP by forming 1:1 (TBP/PNP) complexes through a hydrogen bond between phosphoryl in TBP and hydroxyl in PNP. The model parameters were calculated by fitting the experimental data. D values calculated from the model were in good agreement with experimental ones. In addition, the back-extraction rate was found to be reached 99.9% using 50 mmol·kg–1 NaOH as stripping agent.

Reactive extractions of o-, m-, and p-chlorophenol (o-, m-, and p-CP) from aqueous solutions using tri-n-butyl phosphate (TBP) dissolved in kerosene were studied. The influences of equilibrium aqueous pH (pHeq) and initial TBP concentrations on distribution ratio (D) were discussed. Effective extractions of CP were observed only under pHeq lower than 7.0. D values increased with the increase of initial TBP concentration. TBP mainly reacted with the neutral form of CP by forming 1:1 (TBP:CP) complex through a hydrogen-bond between phosphoryl in TBP and hydroxyl in CP. The apparent reaction extraction equilibrium constant (K) for o-, m-, and p-CP was found in good linear relationship with the addition of dissociation constant (pKa) and the hydrophobic parameter (Log P) of CP, namely, log K = −0.1171 × pKa + 0.0680 × Log P + 2.5848, suggesting pKa plays a much more important role that affects K than Log P. Back-extraction experiments supported > 95 % CP could be recovered using 0.5 mol·L–1 NaOH as stripping ...

Extractions of 8-hydroxyquinoline (8-HQ) by tributylphosphate (TBP) in kerosene, as well as pure TBP and kerosene, were carried out. The investigations involved the equilibrium pH (pHeq) of 3.0 to 11.5, initial 8-HQ concentrations of (0.5 to 5.0) mmol·L–1, and initial TBP concentrations of (0.05 to 1.0) mol·L–1. The distribution ratio (D) was found to be highly dependent on pHeq, and larger D values appeared at pHeq range of 6.3 to 8.4. The distribution constants (KD) for pure TBP and kerosene were calculated to be 236.6 and 26.98, respectively. The experimental KD for TBP/kerosene was expressed by KD,TBP, KD,kerosene, and the volume fractions of TBP or kerosene. The mix of TBP and kerosene was found to be a nonideal process. The deviation of KD from the ideal is proportional to the product of volume fractions of TBP and kerosene. The (1:1) TBP:8-HQ complex was verified by fitting experimental data, and the apparent extraction reaction equilibrium constant was calculated to be 64.58 L·mol–1. The results a...

Reactive extractions of o-, m-, and p-aminophenol (OAP, MAP, and PAP) using trialkylphosphine oxide/kerosene (TRPO/kerosene) have been studied. The equilibrium aqueous pH (pHeq) and the concentrations of TRPO in organic phases were found to be of important effects on the distribution coefficient (D) of OAP, MAP, and PAP between TRPO/kerosene and water. Infrared spectra results suggested pHeq had no influence on the complexes' structures, and TRPO mainly reacted with neutral aminophenol through forming a hydrogen bond between its P═O and aminophenol OH. An expression of D was proposed, and the apparent reactive extraction equilibrium constants (K) were calculated by fitting the experimental data. The dissociation constant of the OH group of aminophenol (namely, pKa2) played a vital role that affected K, while the hydrophobic parameter (log P) of aminophenol had little effect. K was statistically calculated to be in accordance with the equation of log K + pKa2 = 10.94 under all experimental test conditions....

The extraction equilibrium of picolinic acid using trialkylamine (N235) dissolved in n-octanol at 298 ± 0.5 K has been studied. The factors that affected distribution coefficients (D), such as aqueous equilibrium pH (pHeq), N235 concentration, and diluents, were investigated. As diluents, n-octanol showed higher D values than those of tetrachloromethane and kerosene. The maximum D values appeared at a N235 concentration of 0.4218 mol·L–1, which were in agreement with the results of the apparent alkalinity of N235/n-octanol. The D values were also observed with peak values at pHeq in the range of 4.5–6.0. In addition, D decreased with the increase of the initial picolinic acid concentration. Fourier transform infrared spectrometry confirmed that pHeq had no influence on the complexes’ structure and the extraction reaction belonged to the proton-transfer process. The expression of D was proposed based on the mass action law with reasonable assumptions, and the model parameters were calculated by fitting the...

Extraction of p-aminophenol by trialkylamine, trialkylphosphine oxide, di(2-ethylhexyl)phosphoric acid, and the mixed solvent of trialkylamine + trialkylphosphine oxide in heptane was studied under initial pH values ranging from 3 to 10. Trialkylamine and trialkylphosphine oxide extractants extracted the neutral form of p-aminophenol. Di(2-ethylhexyl)phosphoric acid extracted both neutral and positive forms of p-aminophenol. When the initial pH value was between pKa1 and pKa2, a maximum distribution coefficient occurred. This pH dependence can be explained by the variation of the molar fraction of neutral p-aminophenol with pH value. The mixed solvent consisting of trialkylamine + trialkylphosphine oxide had a higher distribution coefficient than the sum of those of trialkylamine and trialkylphosphine oxide; that is, there was a synergistic effect when extracting p-aminophenol with the mixed solvent.