The ability of biological and non-biological adsorbents to remove 2-nitrophenol (2-NP) and 2-chlorophenol (2-CP) from aqueous solutions in batch experiments at room temperature was compared. The marine seaweeds Macrocystis integrifolia Bory (S1) and Lessonia nigrescens Bory (S2) were cross-linked with CaCl(2) to enhance their mechanical properties. Natural bentonite was chemically exchanged with hexadecyltrimethylammonium bromide (B1) and bencyltriethylammonium chloride (B2) to increase their affinity towards organic compounds as well. The adsorption capacity of all of the adsorbents strongly depends on solution pH, whereas equilibrium assays showed a mixed mechanism according to the Langmuir and Freundlich isotherms. The maximum adsorption capacity of 2-NP follows the trend: S1>S2>B2>B1 within the range of 97.37 and 18.64 mg g(-1) whereas for 2-CP, it ranged between 24.18 and 9.95 mg g(-1) with the trend: S1>S2>B2 approximately B1. The importance of the octanol-water partition coefficient as the main factor on the adsorption of these compounds on two different kinds of adsorbents is discussed.