Reactive Extraction of o-, m-, and p-Chlorophenol from Aqueous Solution Using Tri-n-butyl Phosphate in Kerosene

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 (pH(eq)) and initial TBP concentrations on distribution ratio (D) were discussed. Effective extractions of CP were observed only under pH(eq) 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 (pK(a)) and the hydrophobic parameter (Log P) of CP, namely, log K = -0.1171 x pK(a) + 0.0680 x Log P + 2.5848, suggesting pK(a) 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 agent. The work put forward a potential green process for treatment of CP effluents with great importance.