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In-situ Regeneration of Spent Activated Carbon used for the Removal of Geosmin and Methyl-isoborneol (G-MIB) in Dwr Cymru Water Supplies / GEORGE ONYEKWERE
Swansea University Author: GEORGE ONYEKWERE
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Abstract
After repeated use, activated carbon becomes spent because of the adsorption of contaminants like trans-1,10-dimethyl-trans-9-decalol (geosmin) and methyl-isoborneol (MIB), pesticides, and natural organic matter, etc.. The adsorption capacity of the activated carbon needs to be replenished for activ...
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Swansea
2021
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| Institution: | Swansea University |
| Degree level: | Master of Research |
| Degree name: | MRes |
| Supervisor: | Tizaoui, Chedly |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa58405 |
| Abstract: |
After repeated use, activated carbon becomes spent because of the adsorption of contaminants like trans-1,10-dimethyl-trans-9-decalol (geosmin) and methyl-isoborneol (MIB), pesticides, and natural organic matter, etc.. The adsorption capacity of the activated carbon needs to be replenished for activated carbon to be re-used as an adsorbent, thus regeneration is required. The common regeneration methods imply moving the activated carbon to dedicated facilities where it is regenerated using thermal and steam processes. These processes are energy-intensive, costly, and have a high carbon-footprint. Due to its strong oxidation power, ozone can potentially be used to regenerate activated carbon in-situ by removing the contaminants. This project evaluated the effectiveness of ozone in the regeneration of granular activated carbon (GAC), focusing on the effect of ozone on the GAC physical and chemical characteristics. GAC was characterised through the iodine number, methylene blue number, Brunner-Emmett-Teller (BET), Fourier transform infrared spectroscopy measurement (FTIR), and the pH point of zero charge to determine the change in chemical and physical properties of the GAC following ozonation. The results show that the pHpzc slightly decreased as GAC is treated with ozone (90 minute) from 9.92 pH to 9.52. However, the iodine and the methylene blue numbers decreased from 3.60 (virgin GAC) to 2.33 mmole/g (decrease of 35.18 %) and from 0.399 (virgin GAC) to 0.198 mmole/g (decrease of 32.27%) after 90 min ozone treatment, respectively. The effect of ozonation at lower exposure times was more beneficial since 30 minute ozonation yielded lower reductions in iodine and methylene blue numbers. The iodine and methylene blue numbers of the 30 minute ozonated samples yielded a decrease of 11.1% and 10.94%, respectively when compared with the virgin carbon adsorption capacity, which suggests exposure time goes through an optimum value. Although this result shows a reduction of the virgin GAC adsorption capacity, 30 minute ozonation of the spent GAC showed increased adsorption capacity of the spent carbon from 1.53 to 1.91 mmole/g, and FTIR analysis proved that the functional groups imparted by the adsorbed species had been fully removed after ozonation. Ozonation of GAC removes the adsorbed contaminants, while it also increases the amount of highly oxidised species, as seen in the FTIR data. This study has also evaluated a new analysis method based on fluorescence, which was able to determine the concentration of G-MIB before and after adsorption on GAC. Overall, this study shows that increasing the concentration of ozone used to treat activated carbon decreases the activated carbon’s adsorption capacity, thus optimisation of the ozone dose and contact time is required. Ozone regeneration of spent activated carbon removes most of the adsorbed contaminants present on the spent activated carbon surface, as evidenced by FTIR results. It can be concluded that ozone regeneration of spent GAC is an effective method for in-situ regeneration of GAC. However, further optimisation of the process is required. |
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| Item Description: |
A selection of third party content is redacted or is partially redacted from this thesis due to copyright restrictions. |
| Keywords: |
Activated carbon, GAC, Ozone, Regeneration, Water treatment, Geosmin and MIB |
| College: |
Faculty of Science and Engineering |