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    • Effect of Microwave Modification on Activated Carbon and its Adsorption of Methanol

      2014, 41(7):78-83.

      Keywords:microwave modified activated carbon adsorption methanol
      Abstract (1066)HTML (0)PDF 0.00 Byte (0)Favorites

      Abstract:Activated carbon (AC) was modified with microwave irradiation at 600, 700 and 800 ℃respectively. Specific surface area and pore size analyzer, Boehm titration and Fourier transformed infrared spectroscopy were used to measure the physicochemical properties of the activated carbons. Fixed-bed adsorption experiments were conducted at 10 ℃ with methanol as the adsorbate. The research shows that, after microwave modification, the specific surface area and total pore volume of activated carbons decrease slightly, but the micropore specific surface area increases remarkably. With the rise of temperature, large numbers of surface acidic functional groups of activated carbons resolve and surface basic functional groups are formed gradually. Both the Langmuir equation and Freundlich equation can well describe the adsorption of methanol on the activated carbons. Pseudo-second-order kinetic equation describes the dynamic adsorption process of methanol most suitably, which illustrates that methanol adsorption is a physical and chemical composite adsorption process, and adsorption is affected by the surface functional groups of the activated carbons. The fitting result of intra-particle diffusion model is divided into three linear stages: surface adsorption stage, asymptotic adsorption stage and adsorption equilibrium stage. After microwave modification, the adsorption energy of activated carbons for methanol increases, and the adsorption energy is proportional to the contents of surface nitrogen groups of the activated carbon.

    • Adsorption of Toluene on Activated Carbons with Acid Modified

      2013, 40(5):92-98.

      Keywords:modified activated carbon surface functional groups pore structure adsorption kinetics adsorption energy
      Abstract (1007)HTML (0)PDF 0.00 Byte (0)Favorites

      Abstract:Commercially activated carbon was treated with 1mol/L nitric acid, 1mol/L sulfuric acid and 1mol/L hydrochloric acid respectively. The physicochemical properties of these modified activated carbons were described with Boehm titration, Fourier transformed infrared spectroscopy (FTIR) and BET surface area measurement. Fixed-bed adsorption experiments were conducted under the same experimental conditions at 283K, where toluene was activated as adsorbates. Adsorption capacity on modified activated carbons was conducted, combining the calculation of dynamics and adsorption energy. The results have shown that the total amount of acid groups increased after acid modification and the pore size distribution is different from the unmodified activated carbon. The adsorption capacity of toluene on acid modified activated carbon shows the following order: N-AC,S-AC,AC, Cl-AC. The pseudo-second-order kinetic equation is better than the pseudo-first-order kinetic equation to describe the adsorption process of toluene on the modified activated carbons. Acid modification can increase the percentage of micropore and enhance the rate of adsorption. With the increase of adsorption energy, it is hard for the modified activated carbons to join toluene.

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