Document Type

Thesis

Date of Award

12-31-1990

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Dana E. Knox

Second Advisor

John W. Liskowitz

Third Advisor

James M. Grow

Abstract

The relative merits of eight different coal fly ashes for use in the stabilization/Solidification of a waste containing both heavy metals and pentachlorophenol were investigated. Also studied, was the possible use of either untreated or treated (with hexade-cyl ammonium bromide) clay to enhance the stabilization of the organic. The sample composition was : 62% foundry baghouse dust (or 60% if 2% clay as added to the sample), 4.5% cement, 14% coal fly ash, 19.5% water. Pentachlorophenol was chosen as represen¬tative of the organic contamination. All tests were performed after curing the samples at 22°C, 98% Rh for 28 days. The tests consisted of: water content, true density, bulk density, uncon¬fined compressive strength, porosity, and the Toxic Characteris¬tic Leaching Procedure Test (TCLP).

The results showed promising results, based on the physical resistance of the samples and the reduction of the concentration of chromium, lead and cadmium in the leachate. However, after 28 days curing, no differences in the physical or chemical proper-ties could be observed amoung S/S samples made with different fly ashes. Physical tests show an average true density of 2.3, and a strength resistance of about 300 psi. The resitance to the wet/dry testing was excellent, as samples had lost less than 1% corrected cumulative weight loss. However, the resistance to freeze/thaw cycles was not as satisfactory.

A comparison of the results obtained after 28 days, between the untreated and treated clay show that the use of treated clay can enhance the strength and weathering resistance of the cubes. It also reduces the PCP concentration in the leachate by a factor of 10.

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