Simultaneous membrane based solvent extraction (MBSE) and membrane based solvent stripping (MBSS) in HF contactors of a heterocyclic carboxylic acid (HCA) of industrial importance from sulphate solutions with solvent containing trioctylamine (TOA) were studied. An effective transport of HCA was achieved. The proposed reaction-diffusion model gives a much better fit to experimental values than the diffusion model. The mean values of the lumped rate constants of extraction and stripping reactions for HCA are 2.19. 10(-6) and 5.92. 10(6) m.s(-1), respectively. The mass-transfer resistances based on reaction kinetics play a decisive role in MBSE and MBSS of HCA and participate in their overall resistances by about 65 and 40%, respectively.