Studies On Reactive Extraction Of Nitrophenol From Solution

Reactive extraction is based on the reversible chemical complexation and it is a separate method of organic compounds, It has the characteristics of physical extraction and chemical extraction. it can make the regeneration of the extraction agent and the recovery of the solute by changing the condition. It has many advantages such as less secondary pollution and low cost and so on.In this work, the reactive extraction equilibrium of o-nitrophenol(ONP), m-nitrophenol(MNP), p-nitrophenol(PNP) using tributylphosphate(TBP) dissolved in solvent naphtha and noctanol has been studied, respectively. The effects of equilibrium pH(pHeq), initial TBP, and PNP concentrations on the distribution ratio(D) and the degree of the back-extraction(E%)were discussed.The TBP/solvent naphtha showed higher D values than that of TBP/n-octanol. The pHeq is a dominant factor influencing the extraction effect. The larger D values were also observed at pHeq in the range of 1.5-4, 1.8-4, 1.6-5 respectively in the reactive extraction of o-, m-, p-NP. The increase of TBP concentration leads to an increase in D values. It is obvious that D values slightly decreased with the increase of initial concentration of nitrophenol. NaOH has a superior back-extraction rate. The back-extraction rate o-, m-, and p-NP can be reached 99.2%, 99.3% by using 20 mmol·kg-1 NaOH, 99.5%, 99.9% by using 50 mmol·kg-1 NaOH, and 99.9%, 99.2% by using 50 mmol·kg-1 NaOH in TBP/solvent naphtha and TBP/noctanol system. The proposed model is feasible and validated to the discussed extraction systems. TBP mainly reacted with neutral o-, m-, and p-NP, resulting in the formation of 1:1 complexes through a hydrogen bond between P=O of TBP and OH of o-, m-, and p-NP, which was confirmed by IR spectra analysis.And this model proves that the fit is in agreement with the experimental value.The pKa and Log P of nitrophenol were discussed on the basis of experiments. The distribution ratio of nitrophenol is increased with the increase of pKa. The increase of Log P value leads to an increase in D values.