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| Titel |
A Sustainable Approach for Acid Rock Drainage Treatment using Clinoptilolite |
| VerfasserIn |
L. Y. Li, W. Xu, J. R. Grace |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020264
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| Zusammenfassung |
| Problems related to acid rock drainage (ARD) occur along many highways of British
Columbia. The ARD problem at Pennask Creek along Highway 97C in the
Thompson-Okanagan region is an ideal site for pilot study to investigate a possible
remediation solution. The highway was opened in 1991. An ARD problem was identified in
1997. Both sides of Highway 97C are producing acidified runoff from both cut rock
surface and a fractured ditch. This runoff eventually enters Pennask Creek, the largest
spawning source of rainbow trout in British Columbia. The current remediation
technique using limestone for ARD treatment appears to be unnecessarily expensive, to
generate additional solid waste and to not be optimally effective. A soil mineral natural
zeolite – clinoptilolite – which is inexpensive and locally available, has a high metal
adsorption capacity and a significant buffering capacity. Moreover, the clinoptilolite
materials could be back-flushed and reused on site. An earlier batch adsorption
study from our laboratory demonstrated that clinoptilolite has a high adsorption
capacity for Cu, Zn, Al, with adsorption concentrations 131, 158 and 215 mg/kg
clinoptilolite, respectively, from ARD of pH 3.3. Removal of metals from the loaded
clinoptilolite by back-flushing was found to depend on the pH, with an optimum
pH range for extraction of 2.5 to 4.0 for a contact time of one hour. The rank of
desorption effectiveness was EDTA > NaCl > NaNO3 > NaOAC > NaHCO3 >
Na2CO3 > NaOH > Ca(OH)2. A novel process involving cyclic adsorption on
clinoptilolite followed by regeneration of the sorbent by desorption is examined for the
removal of heavy metals from acid rock drainage. Experimental results show that the
adsorption of zinc and copper depends on the pH and on external mass transfer.
Desorption is assisted by adding NaCl to the water. A slurry bubble column was
able to significantly reduce the time required for both adsorption and desorption
in batch tests. XRD analysis indicated that the original structure of the sorbent
is retained over multiple adsorption/ desorption cycles. Clinoptilolite in a slurry
bubble column appears to be a promising sorbent for treatment of ARD leachate. |
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