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State Key Laboratory for Environmental Criteria and Risk Assessment, SKLECRA: SKLECRA2013FP12
Generically Dependent Continuant
RDF description of Cr(VI) adsorption on activated carbon: Mechanisms, modeling and limitations in water treatment - http://orbis.uaslp.mx/vivo/individual/scopus6379
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Cr(VI) adsorption on activated carbon: Mechanisms, modeling and limitations in water treatment
Activated carbon; Adsorption mechanisms; Adsorption modeling; Chromium removal; Water treatment Activated carbon; Activated carbon treatment; Activation energy; Adsorption; Adsorption isotherms; Redox reactions; Surface diffusion; Adsorption energies; Adsorption mechanism; Adsorption process; Batch adsorption tests; Continuous layers; Granular activated carbons; Langmuir models; Surface diffusion model; Chromium compounds
Adsorption of Cr(VI) on highly porous granular activated carbon (GAC) was studied through batch adsorption tests at a very long time, various temperatures and pH 3.5, in order to delineate the adsorption mechanisms, model the adsorption process and assess the applicability of GAC in water treatment. Adsorption of Cr(VI) occurred through a redox reaction with the formation of Cr2O3(s) (Cruz-Espinoza et al., 2012). It is reported for the first time that Cr(VI) adsorption proceeded in two steps. Furthermore, adsorption increased with temperature and reached equilibrium after several hours. In the first step, very fast adsorption occurred with the formation of a nano-size continuous layer of Cr2O3(s) coating on the GAC surface, as revealed by SEM analysis. In the second stage, adsorption occurred at a very slow rate due to the slow diffusion rate through the continuous Cr2O3(s) layer on the GAC surface. The two adsorption steps were successfully described by the surface diffusion model and pore volume diffusion model. The first step is controlled by surface diffusion while the second step by both pore volume diffusion and surface diffusion. A pseudo-activation energy was determined for each adsorption step and found that more adsorption energy is required in the first step than the second step. The adsorption isotherms for various temperatures were fitted well by the Langmuir model. The Cr2O3 layer on the GAC is responsible for its low Cr(VI) adsorption capacity, so a large amount of GAC would be required to treat water with Cr(VI). © 2020 Elsevier Ltd.
Journal of Environmental Chemical Engineering