Cr(VI) adsorption on activated carbon: Mechanisms, modeling and limitations in water treatment
| Autor: | Changsheng Peng, Alejandro Lopez-Valdivieso, Aurora Robledo-Cabrera, Erika Padilla-Ortega, Yongmei Wang |
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| Rok vydání: | 2020 |
| Předmět: |
Surface diffusion
Chemistry Process Chemistry and Technology Diffusion Langmuir adsorption model 02 engineering and technology 010501 environmental sciences 021001 nanoscience & nanotechnology 01 natural sciences Pollution Redox symbols.namesake Adsorption Volume (thermodynamics) Chemical engineering medicine symbols Chemical Engineering (miscellaneous) Water treatment 0210 nano-technology Waste Management and Disposal 0105 earth and related environmental sciences Activated carbon medicine.drug |
| Zdroj: | Journal of Environmental Chemical Engineering. 8:104031 |
| ISSN: | 2213-3437 |
| DOI: | 10.1016/j.jece.2020.104031 |
| Popis: | 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). |
| Databáze: | OpenAIRE |
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