Regeneration of ortho-chlorophenol-exhausted activated carbons with liquid water at high pressure and temperature
ABSTRACT A study was undertaken of the regeneration of three activated carbons exhausted with ortho-chlorophenol. The regeneration process was carried out using liquid water at 623 K and 150 atm in the absence of oxygen. The efficiency of this procedure was analyzed by determining the rate and amount of ortho-chlorophenol adsorbed in successive adsorption-regeneration cycles. The present procedure showed a much greater efficiency than that reported for chemical and/or thermal regeneration. Effects of this regeneration on the adsorption kinetics, adsorption capacity and textural characteristics of the carbon were investigated. The increase in adsorption capacity of the regenerated carbon compared with that of the original carbon seems mainly due to the opening of porosity during the regeneration treatment.
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ABSTRACT: Adsorption of organic molecules from dilute aqueous solutions on carbon materials is a complex interplay between non-electrostatic and electrostatic interactions. Non-electrostatic interactions are essentially due to dispersion and hydrophobic interactions, whereas the electrostatic or coulombic interactions appear with electrolytes when they are ionized at the experimental conditions used. Both interactions depend on the characteristics of the adsorbent and the adsorptive and the solution chemistry. Among them the carbon surface chemistry has a great influence on both electrostatic and non-electrostatic interactions, and can be considered one of the main factors in the adsorption mechanism from dilute aqueous solutions. In this paper the current knowledge about the fundamental factors that control the adsorption process from aqueous phase will be presented.Carbon 12/2004; 42(1):83-94. DOI:10.1016/j.carbon.2003.09.022 · 6.20 Impact Factor
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ABSTRACT: An investigation was performed for the regeneration of three granular activated carbons (GACs) exhausted with acid orange 7 (AO7). The three GACs were made from different materials, i.e. coconut shells, almond nucleus and coal. The AO7 adsorption process was carried out in a continuous-flow adsorption column. After adsorption, the AO7-saturated GAC was dried at 120 degrees C, then regenerated in a quartz reactor by 2450 MHz microwave (MW) irradiation at 850 W for 5 min. The efficacy of this procedure was analyzed by determining the rates and amounts of AO7 adsorbed in successive adsorption-MW regeneration cycles. Effects of this regeneration on the structural properties, surface chemistry and the AO7 adsorption capacities of GAC samples were examined. It was found that after several adsorption-MW regeneration cycles, the adsorption rates and capacities of GACs could maintain relatively high levels, even higher than those of virgin GACs, as indicated by AO7 breakthrough curves and adsorption isotherms. The improvement of GAC adsorption properties resulted from the modification of pore size distribution and surface chemistry by MW irradiation.Water Research 01/2005; 38(20):4484-90. DOI:10.1016/j.watres.2004.08.031 · 5.53 Impact Factor
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ABSTRACT: Adsorption equilibrium, kinetics, and column dynamics of chlorophenols [2‐chlorophenol (2‐CP) and 2,4‐dichlorophenol (2,4‐DCP)] dissolved in water were studied using a hydrophobic resin, XAD‐1600, without ion‐exchange functional groups. In addition, a hydrophilic nonionic polymer resin, XAD‐7, and an activated carbon, F400, were chosen for comparative analysis. Adsorption equilibrium data were correlated with the well‐known Langmuir, Freundlich, and Sips isotherms. The adsorption amount was in the order of F400 > XAD‐1600 > XAD‐7. Desorption from polymeric resins adsorbed with chlorophenols was conducted by using two organic solvents [methanol and isopropyl alcohol (IPA)] as desorbates. The intraparticle diffusion mechanism was assumed to be the surface diffusion or pore diffusion. It was found that the diffusivity in desorption step was considerably slower than the diffusivity in adsorption step within polymeric resins. To confirm the possibility of the resin as a sorbent for the removal of chlorophenols, adsorption breakthrough curves were measured under key operating conditions, such as concentration, flow rate, and column length. A simple dynamic model was also formulated to describe both the adsorption and desorption breakthrough curves of chlorophenols.Separation Science and Technology 01/2005; 39(9):2041-2065. DOI:10.1081/SS-120034190 · 1.17 Impact Factor