The fixed bed adsorption of acid dyes on activated carbon was studied. Acid Blue 80 (AB80), Acid Red 114 (AR114) and Acid Yellow (AY117) were selected as adsorbates and Granular Filtrasorb 400 activated carbon (GAC) as the adsorbent. The effect of operating parameters, such as volumetric flowrate, initial dye concentration and mean particle diameter, on the adsorption systems were investigated using mathematical models....[ Read more ]

The fixed bed adsorption of acid dyes on activated carbon was studied. Acid Blue 80 (AB80), Acid Red 114 (AR114) and Acid Yellow (AY117) were selected as adsorbates and Granular Filtrasorb 400 activated carbon (GAC) as the adsorbent. The effect of operating parameters, such as volumetric flowrate, initial dye concentration and mean particle diameter, on the adsorption systems were investigated using mathematical models.

A modified Bed Depth Service Time (BDST) model was initially developed. The modification was made due to the non-equilibrium operation of the fixed beds. The new service time calculated from this new model can be used in the EBRT optimization procedure. Therefore, the effect of operating parameters (i.e. fluid volumetric flowrate, initial dye concentration and mean particle size) on the minimum carbon exhaustion rate and the minimum EBRT were evaluated.

A Film Pore Diffusion Model and a Homogeneous Surface Diffusion Model (HSDM) - with fixed surface diffusivity and variable surface diffusivity - were developed and used to analyse the experimental data. The effective diffusivities in the Film Pore Diffusion Model were determined as remaining unchanged for the variation of operating parameters. A modified correlation of the external mass transfer coefficient (EMTC) was developed in the HSDM study. The surface diffusivities in the HSDM study were found to be concentration dependent. Hence, three types of surface diffusivity correlations with the surface loading were tested. The Darken (1948) model with the Redlich-Peterson isotherm was found to be a suitable correlation model for the acid dyes adsorption of the acid dyes on carbon.

A multicomponent mass transport diffusion model was developed based on the extension of the single component HSDM incorporating the use of the Ideal Adsorbed Solute Theory (IAST) for the prediction of multicomponent equilibrium concentration. The correlation of surface diffusivity to the surface loading was derived based on the experimental multicomponent equilibrium data. There is a discrepancy between the surface diffusivities at zero surface loading determined in the single and multicomponent HSDM analyses. It may be due to inaccuracy of the assumption about the interaction of dye components during the diffusion process. Further work on the multicomponent equilibrium capacity, the combined diffusion model and the temperature effects on the adsorption capacity and the diffusion processes were recommended.