Reactive extraction of phenol from aqueous solution using tri-octylamine dissolved in alkanes and alcohols

Extraction of phenol (0.053 mol·kg− 1) from wastewater is performed with trioctylamine (TOA: 0.023-0.091 mol·kg− 1) dissolved in four solvents (decane, octane, decan-1-ol, and octan-1-ol) at a constant temperature of 298 K. The effect of TOA concentration and type of diluent on the removal efficiency of phenol have been derived. Results show that the neutral phenol molecule is effectively extracted by TOA into the organic phase at higher concentration of TOA than lower one. The equilibrium extraction results are presented in terms of distribution coefficient (D), degree of extraction (%E) and loading ratio (Z). Maximum value of D (= 12.25) with %E = 92.45% is observed at the highest concentration of TOA (0.091 mol·kg− 1) with octan-1-ol. A mathematical expression for the determination of D at equilibrium is presented by applying the mass action law. This model equation is used to graphically determine the equilibrium constant (KE) and the stoichiometric coefficient (n) of extraction. Also, the individual equilibrium constants (K11, K21 and K12) for the phenol-TOA complexes formed are estimated from the regression of the experimental results. The highest value of complexation constant (KE = 2.3) is found with TOA in octan-1-ol. Phenol molecules are extracted by TOA + decane or octane with simultaneous formation of 1:1 and 2:1 solvates, and by TOA + decan-1-ol or octan-1-ol by making 1:1 and 1:2 complexes in the organic phase. The extraction power of TOA in terms of D decreases in the order of octan-1-ol > decan-1-ol > octane > decane.