Modeling the sorption of toxic metals on chelant-impregnated adsorbent

• Published in: AIChE journal 1999-05, Vol.45 (5), p.1135-1146
• Main Authors: Ravindran, Varadarajan, Stevens, Mario R., Badriyha, Badri N., Pirbazari, Massoud
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; General purification processes; Pollution; Wastewaters; Water treatment and pollution
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.690450520

The application of a microporous adsorbent, such as activated carbon impregnated with 8‐hydroxyquinoline (oxine), a chelating agent, to remove toxic metals from the aqueous phase is studied. A pore and surface diffusion model for predicting the dynamics of fixed‐bed adsorbers using oxine‐impregnated carbon is also discussed. The model incorporates adsorption equilibrium and kinetic parameters determined from independent isotherm tests and rate experiments, as well as adsorber column flow characteristics. Three modeling scenarios were employed with reference to intraparticle transport: (a) combined pore diffusion and surface diffusion; (b) pore diffusion alone, suppressing the effect of surface diffusion; and (c) surface diffusion alone, suppressing the effect of pore diffusion. Surface diffusion alone provided reasonably good predictions of the adsorber dynamics, as reflected by results from adsorber experiments. It is postulated that the sorption mechanism could be a combination of film transport of metal ions, followed by surface diffusion into adsorbent particles, and subsequent chelation of metal ions with the oxine molecules sorbed on carbon. The sorbed metals could be completely recovered under acidic conditions during the carbon regeneration process.