Enhanced abatement of aqueous organic compounds using stratified activated carbon adsorption columns.

摘要

The feasibility of adsorptive removal of single component organic compounds (namely para-chlorophenol and Acid Blue 25) by Calgon Filtrasorb 400 (F400) carbon has been investigated. The Redlich-Peterson and Langmuir isotherm models were found to be the best fit models for describing the equilibrium relationship between the para-chlorophenol and Acid Blue 25 adsorption onto F400 carbon respectively.The agitated batch adsorption data proved that the smaller F400 carbons possessed faster adsorption rates compared to the larger F400 carbons. The two resistance Crank diffusion model was used to predict the batch adsorption data, and provide an estimate of the constant surface diffusivity for use in the Film Homogeneous Surface Diffusion Model implemented for the dynamic adsorption of organics onto F400 carbon in fixed-bed adsorption columns.Four adsorption columns with different column geometry and adsorbent particle stratification are used to examine the dynamic organics adsorption onto F400 carbons. The Bed Depth Service Time (BDST) model is applied and modified to analyse the performance of the columns and the effect of different operating variables. The Film Homogeneous Surface Diffusion Model (FHSDM), which incorporates the film mass transfer and surface controlled diffusion, was applied to describe the organics adsorption mass transfer process within the porous F400 carbons accurately. The FHSDM was found to correlate the breakthrough curves well for para-chlorophenol/F400 carbon and reasonably well for Acid Blue 25/F400 carbon.When combining the effects of adsorption efficiency and the associated pressure drop of each type of adsorption columns tested, the carbon stratified tapered column has been determined to be the most efficient engineering option for removing organics, in which the enhancement of the adsorbent bed in terms of longer breakthrough time and higher saturation percentage is the greatest amongst the four types of columns with reasonably small pressure drop across the fixed-bed column.