To enhance the oil sorption capacity of polyurethane foam, different amounts of activated carbon (0.5, 1, 2 and 3 wt%) were grafted onto the surface of polyurethane foam. The modified polyurethane foam was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and tensile elongation test. Grafting of activated carbon improved the polyurethane foam toughness and thermal resistance as revealed by tensile elongation and thermogravimetric tests, respectively. Experimental results showed the enhancement of oil sorption capacity and reduction in the water sorption in all cases. The optimal amount of activated carbon on the surface was 1 wt% which enhanced the oil sorption capacity up to 33.2 %. Reusability feature of the optimum sorbent was examined through four cycles of chemical regeneration, and about 85 % of the initial sorption capacity of the modified polyurethane foam was remained at the end. Equilibrium isotherms were analyzed using Langmuir, Freundlich and Redlich–Peterson isotherms using linear and nonlinear regression methods. The Marquardt’s percent standard deviation and hybrid fractional error functions were minimized and normalized to investigate the effect of error criteria to determine the parameters of isotherms. The nonlinear method was found to be more accurate to determine the isotherm parameters, and the Langmuir isotherm was the best-fitting model.