RESEARCH PAPERS : LEACHABILITY OF PB-DOPED SOLIDIFIED WASTE FORMS USING PORTLAND CEMENT AND CALCITE: 3. INSIGHT OF LEACHING MECHANISM

AbstractThe seawater leachability of portland cement solidified cadmium and lead wastes is investigated. The synthetic seawater leachates were analyzed for metals content using atomic absorption spectrophotometry. The pH and alkalinity of the leachate was also measured. The cumulative cadmium release after 46 days of leaching was approximately 1.0 percent of the initial total amount added to the portland cement mixture. Lead was not detected in the leachate. The pH was initially higher and the alkalinity lower and subsequently approached the pH and alkalinity values for seawater after 30 days of leaching.The microstructure of the solidified waste was investigated using the SEM, XRD, MIP and helium pycnometry. Cadmium was detected as cadmium hydroxide while lead was not detected in crystalline form. The total porosity of cadmium and lead wastes were similar however the cadmium waste had a higher volume of pores larger than 0.2 microns.During the leaching process the surficial microstructure of the solidified waste exhibited a dynamic layer of calcite, aragonite and brucite while the internal structure showed large amounts of ettringite crystals in the cadmium waste only which caused excessive expansion and cracking. A proposed leaching mechanism experienced by the solidified waste is related to the microstructural characteristics of the matrix.

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Test Method for Accelerated Leach Test for Diffusive Releases from Solidified Waste and a Computer Program to Model Diffusive, Fractional Leaching from Cylindrical Waste Forms

10.1520/c1308-95r01 ◽

2001 ◽

Author(s):

Keyword(s):

Computer Program ◽

Test Method ◽

Waste Forms ◽

Leach Test ◽

Solidified Waste

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Cementation of Bioproducts Generated from Biodegradation of Radioactive Cellulosic-Based Waste Simulates by Mushroom

ISRN Chemical Engineering ◽

10.5402/2012/329676 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 10

Author(s):

S. B. Eskander ◽

S. M. Abd El-Aziz ◽

H. El-Sayaad ◽

H. M. Saleh

Keyword(s):

Radioactive Waste ◽

Portland Cement ◽

Current Work ◽

Waste Form ◽

Pleurotus Pulmonarius ◽

Long Term Stability ◽

Surrounding Environment ◽

Solidified Waste ◽

Physical And Chemical

The current work was devoted to study the solidification of bioproducts originated from the bioremediation of mixture of solid cellulose-based radioactive waste simulates using a mushroom (Pleurotus pulmonarius), in Portland cement. The obtained solidified waste form was subjected to mechanical integrity qualification after curing periods of 28 and 90 days. Chemical performance of the cement-waste form was also evaluated in different leachant media during 540 days. The results obtained gave useful information about the mechanical, physical, and chemical performances of the final cement-waste form incorporated the radioactive bioproducts. Moreover, it indicated that cement can provide a highly durable form that ensures a long-term stability of the solidified waste material and can act as a first barrier against the release of radiocontaminants from radioactive wastes to the surrounding environment.

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