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Alkaline solution neutralization capacity of soil
Hiroshi Asakura1, Hirofumi Sakanakura, Toshihiko Matsuto
1Fukken Co., Ltd., 2-10-11 Hikarimachi, Higashi-ku, Hiroshima 732-0052, Japan. asakura_hiroshi@yahoo.co.jp
Waste Management (New York, N.Y.)
|April 17, 2010
Summary
Daily cover soil effectively neutralizes alkaline leachates from municipal solid waste (MSW) landfills, preventing heavy metal elution. This buffering capacity is crucial for landfill stability and environmental protection.
Area of Science:
- Environmental Science
- Geochemistry
- Waste Management
Background:
- Alkaline eluate from municipal solid waste (MSW) incineration residue can raise the pH of landfill layers, potentially increasing heavy metal elution.
- Controlling the pH of landfill layers is essential for enhancing stability and preventing the release of hazardous substances.
- Existing MSW landfill leachate typically exhibits a near-neutral pH, partly due to the neutralization capacity of daily cover soils.
Purpose of the Study:
- To evaluate the neutralization capacity of various soil types against alkaline solutions, specifically calcium hydroxide (Ca(OH)(2)) and sodium hydroxide (NaOH).
- To understand the mechanisms behind soil's ability to neutralize alkaline substances found in landfill environments.
- To assess the effectiveness of daily cover soil as a buffer against alkaline leachates.
Main Methods:
- Titration tests were performed to measure the alkali neutralization capacity of different soil samples using Ca(OH)(2) and NaOH solutions.
- The contribution of cation exchange capacity (CEC) to the overall neutralization was assessed.
- Analysis focused on identifying the neutralization mechanisms, particularly pH-dependent charge.
Main Results:
- All tested soils demonstrated similar neutralization capacities for both Ca(OH)(2) and NaOH solutions.
- Cation exchange capacity accounted for less than 30% of the maximum alkali neutralization capacity observed.
- The neutralization process appears to be primarily governed by pH-dependent charge mechanisms in the soils.
Conclusions:
- Daily cover soils possess a significant capacity to neutralize alkaline solutions, including those containing Ca(OH)(2) and potentially other alkaline substances.
- The neutralization is mainly attributed to pH-dependent charges rather than cation exchange.
- Daily cover soils can function effectively as a buffer zone, mitigating the impact of alkaline leachates in MSW landfills.
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