Effluents or liquids of percolation from the discharges (leachates) are charged bacteriologically and especially chemically of mineral substances (mineral ions and heavy metals) and organic (volatile fatty acids, humic substances), which can contaminate soil, surface waters and ground waters. The humic substances, called also refractories, are not easily biodegradable and require concentrating them and/or adsorbing them by implementation of expensive processes. Scientists are looking for alternatives to eliminate or recover these substances. The present study investigates the elimination of humic acid from waste water using supported liquid membrane containing trioctyl phosphine oxide (TOPO) in toluene, as extractant. The supported liquid membrane is composed of a flat sheet of cross-linked polydimethylsiloxane (PDMS). In this study we have: (i) optimized the conditions for humic acid species transfer from feed aqueous phase to stripping phase across PDMS/TOPO/toluene supported liquid membrane; (ii) characterized the membrane by using FTIR technique and by determining the flux J, permeability P and diffusion coefficient of the complexed species D. Speciation of the humic acid species in the membrane organic carrier (extractant) phase has also been carried out using theoretically derived equations to elucidate the stoichiometry and mechanism of transport of humic acid across the PDMS/TOPO/toluene supported liquid membrane. Optimum conditions of transport for humic acid have been found to be: pH=3, [NaOH]=0.4 M, Eextraction = 94.67%, E diffusion = 32.5%, J = 1.34 × 10 −4 mg cm −2 s −1 , D = 1.16 × 10 −2 cm 2 s −1 and P = 2.64 cm s −1 . Kinetic parameters calculated from the experimental data have been determined. Thermodynamic functions of the several species transfer from the feed solution to the stripping one through the supported liquid membrane, such us enthalpy, entropy and Gibbs free energies, were determined. Positive values of ∆H and negative values of ∆G indicate respectively the endothermic and the spontaneous nature of the humic acid extraction in aqueous solution.