Adsorption of 2,4-D and carbofuran pesticides using fertilizer and steel industry wastes

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and carbofuran from aqueous solution was studied by using fertilizer industry waste (carbon slurry) and steel industry wastes (blast furnace slag, dust, and sludge) as adsorbents in batch. Adsorption was found to be in decreasing order: carbon slurry, blast furnace sludge, dust, and slag, respectively. Carbonaceous adsorbent prepared from carbon slurry exhibited the uptake capacity of 212 and 208 mg g(-1) for 2,4-D and carbofuran, respectively at 25 degrees C and pH 7.5. Adsorption equilibrium, kinetics, and thermodynamics were investigated as a function of initial pH, temperature, and pesticide concentrations. Equilibrium data fitted well to the Langmuir equilibrium model in the studied concentration range of 2,4-D and carbofuran at all the temperatures studied. Two simplified models, including pseudo-first-order and pseudo-second-order kinetic models, were used to test the adsorption kinetics. Adsorption of 2,4-D and carbofuran on carbon slurry at 25, 35, and 45 degrees C could be best fitted in the pseudo-second-order kinetic model. Pore diffusion was confirmed as the essential rate-control ling step with the help of Bangham's equation. (c) 2006 Elsevier Inc. All rights reserved.