Efficiency of activated carbons and natural bentonite to remove direct orange 39 from water

[Display omitted] The presence of dyes in water is a problem in many industries and removing them efficiently is of great importance. Adsorption using a variety of materials can be performed as an effective way of treating and removing a wide range of contaminants. Direct Orange 39 (DO39) is a recalcitrant compound and its metabolites can be very toxic to aquatic life. In order to compare different materials to remove DO39 dye from water, batch adsorption tests were performed with natural bentonite and two activated carbons (S42 and S46). Using 0.05 g of S42 and S46, 53.05% and 59.48% removals were obtained at pH 7, respectively, while bentonite was able to remove 6.29% under extremely acidic conditions (pH 2). Kinetic data showed a high correlation with pseudo-second order model for all adsorbents. A high correlation was obtained with Langmuir for both activated carbons, while bentonite was better explained by Freundlich model. S46 showed a higher adsorption capacity (147.30 mg g−1) than S42 (135.01 mg g−1). A Freundlich constant (K) equal to 0.49 (mg g−1)·(L mg−1)1/n was achieved with bentonite. Both activated carbons were faster and more efficient to remove DO39, but bentonite can still be an interesting alternative as a cheaper adsorbent.