Preparation of novel activated carbons from H₂SO₄-Pretreated corncob hulls with KOH activation for quick adsorption of dye and 4-chlorophenol

Corncob hull was immersed in 25 wt% H₂SO₄ and was carbonized in an oven at 290 °C for 2h to obtain the char. The char was then activated for 1h at 780 °C by KOH at weight ratio of KOH/char of 2.5, 3.0, and 3.5. SEM photos of the carbons revealed that the cell wall of corncob hull was etched into thin film structure. It was shown that the adsorption isotherms of methylene blue and 4-chlorophenol on the carbons were well fitted by the Langmuir equation. Moreover, the adsorption kinetics could be satisfactorily described by the Elovich equation. The normalized standard deviations are less than 2.8%. The high fraction of adsorption amount adsorbed within 1min to that at saturation demonstrated the advantage of the prepared activated carbons. The fraction of adsorption amount within 1min to that at saturation (q₁/q_mon) for the adsorption of 4-CP is high up to 0.807. Such quick adsorption behavior was mainly attributed to the presence of the thin film structure of carbons.