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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472 EISSN: 1735-1472
Vol. 11, No. 4, 2014, pp. 1017-1026
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Bioline Code: st14100
Full paper language: English
Document type: Research Article
Document available free of charge
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International Journal of Environment Science and Technology, Vol. 11, No. 4, 2014, pp. 1017-1026
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Pressure-assisted cyclic washing of heavy-metal-contaminated sediments
Lin, C. E.; Hong, P. K. A.; Chiu, H. Y.; Surampalli, R. Y.; Lin, C. T. & Kao, C. M.
Abstract
Remediation of heavy-metal-contaminated
sediment is often hampered by the availability of heavy
metals to the added chemical agents because the heavy
metals are often shielded by the sediment matrix. Effective
heavy-metal extraction technique becomes an important
factor in enhancing the treatment efficiency. A novel
extraction/washing technique utilizing chelating agent and
elevated pressure in consecutive cycles of compression and
decompression has been developed for heavy-metal-contaminated
sediment washing in the presence of chelating
agent. In this study, the optimal operational conditions of
pressure-assisted cyclic washing of Cu-contaminated sediments
(initial Cu concentration = 23.177 mg/kg) were
determined in a laboratory-scale system. The control factors
included applied pressure level, washing time, applied
chelant [ethylenediamine-tertraacetic (EDTA)] concentration
(0.01–0.5 M), pressure times, and application of consecutive
batches washing. Results from the bench-scale
study showed that up to 70 % of Cu can be removed from
the sediments when 10 atm of pressure was applied for
washing. The efficiency dropped to 55 % when the pressure
dropped to 6 atm. Under the same operational conditions,
the optimal cyclic washing time was 60 min.
Results from the particle size analyses indicate that the
mean particle size dropped from 100 to 50 μm after the
pressure-assisted cyclic washing. Thus, cyclic pressure
caused the fracture of sediment aggregates resulting in the
exposure of Cu to chelating agents. With the assistance of
pressure cyclic system, the total washing time and the
amount of added chemical agent used can be significantly
reduced.
Keywords
Chelating agent; Heavy metal; Pressureassisted cyclic washing; Sediment contamination
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