The present study is aimed to optimized diluent type, tri-n-butyl phosphate (TBP) composition and temperature for the reactive extraction of p-nitro phenol (PNP) in two different PNP concentration ranges [(0.00036-0.00646) kmol center dot m(-3) and (0.00646-0.01437) kmol center dot m(-3)] as found in industrial effluents. 1-Octanol is investigated as the best diluent with TBP based on COSMO-RS theory. Equilibrium study based on mass action law is performed to find the insights of extraction mechanisms, equilibrium constant (K = 295.12 k center dot mol(-1)) and stoichiometry (m:n = 1:1) as also confirmed by FTIR. Thermodynamic parameters, enthalpy (Delta H degrees), and entropy (Delta S degrees) are determined 27.51 K J mol(-1) and -50.21 J mol(-1) K-1, respectively.