SUITABILITY OF LOCAL CLAYS FOR RADIOACTIVE WASTE DISPOSAL
SUITABILITY OF LOCAL CLAYS FOR RADIOACTIVE WASTE DISPOSAL
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Date
1989-01
Authors
ADELEYE, Solomon Ajibade
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Abstract
Six local clays namely Bomo, Bukuru, Kankara, Manjahota,
Onibode and Upkor were studied for use as wasteform for fixation
of strontium ion in radioactive wastes. The clays were
characterized with respect to cation exchange capacity, organic
carbon content and crystal structure. Then the most relevant
properties of c]ay wasteforms: shrinkage, density and porosity
were studied for Bomo clay and finally, the prepared wasteforms
were tested for leaching characteristics.
Bomo clay had the highest cation exchange capacity (CEC)
of 44.45 and 50.50 meq/l00g for raw and beneficiated respectively.
It was followed by Bukuru clay. The other clays had
rather low CEC values of between 26.1 and 15.32 meq/l00g lor both
raw and beneficiated. Bomo clay contained quartz,
illite and montmorillonite with some muscovite in the raw
sample. While Bukuru clay contained predominantly quartz and
disordered kaolinite. The other clays contained predominantly
kaolinite, illite and quartz minerals. Bomo clay had the best
characteristics for fixation and disposal of radionuclides.
The shrinkages of the wasteforms were generally higher
for the beneficiated than for the raw samples. The bulk density
ranged between 1.80 x 103and 1.94 x 103 kg/m3 and apparent
porosity ranged between 17.2 - 24.2%.
For low strontium concentration of 1587.5 ug/g the mass
fixed in clay mineral varied between 63.0 - 70.9 percent of the
initial mass used for equilibration while 30.0-41.3 was obtained
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for high concentration of 7875 ug/g. The highest percentage
cation loading obtained were 50 and 73 of the total CEC of
Bomo clay for low and high concentrations. Bomo clay gave
promising result of over 99% retention of fixed strontium after
25 days of leaching. The cummulative mass leached for 25
days ranged between 9.0 ug/g for BL1 and 3.5 ug/g for sample BL3
for the low concentration and 20.0 ug/g for sample BH1 and 2.0
ug/g for sample BH3 for high concentration. For beneficiated
sample, the mass leached decreased sharply as temperature
increased from 800-1000 C. The most fixation was obtained by
beneficiating the clay and firing to 1000 C for both low and
high concentrations. However, considerable fixation was
obtained by using a raw clay even at 800 C. The leach rate
approximately obeyed the natural decay law: R = R e
The distribution coefficient, a , generally increased with
increase in temperature. The values ranged between 1632 for
sample BL1 and 4516 for sample BL3 for low concentration and
2566 for sample BH1 and 20478 for sample BH3 for high concentration.
Description
A THESIS
Presented to
The Postgraduate School
Ahmadu Bello University, Zaria
BY
Solomon Ajibade ADELEYE
In Partial Fulfillment of
the Requirements for the Degree
Master of Science (Chemical Engineering)
Department of Chemical Engineering
Keywords
SUITABILITY,, LOCAL CLAYS,, RADIOACTIVE,, WASTE DISPOSAL.