Metal complexation in near field conditions of nuclear waste repository - stability constant of copper complexation with cellulose degradation products, in alkaline conditions
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Date
2005-11-03
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Abstract
Copper is a stable element and spent fuel component which constitutes the radioactive waste. The reaction of Copper with cellulose degradation products in alkaline conditions was performed to mimic what occurs in near field conditions of nuclear waste repository.
From the characteristics of Cu (II), this thesis aims at inferring the behaviour of radionuclides vis a vis the degradation products of cellulose. The contribution of the present work is therefore the assessment of the stability of the major cellulose degradation product, its affinity for Copper and the extent of the complexation function 13 between Cu (II) and the organic moieties.
The formation of cellulose degradation products was followed by measurement of p11, Conductivity, Angle of rotation, relative abundance of aliphatics and aromatics (E4/E6 ) aid by UV-visible spectroscopy. The TOC was determined using the Walkley and Black titration after respectively 31 weeks and 13 weeks of degradation for the i-eaction mixtures T and A, N. The stability of the major degradation products gave the following figures:
ISA(A): - 13 143.39 <ΔG -10639.88
ISA(N): - Ii 436.45<ΔG< -9103.6.
The study of the characteristics of Gluconic Acid, as a model compound, was carried out in an attempt to give a general picture of the roper ties of cellulose degradation products.
The Complexation between Cu (II) and the organic ligand (Cellulose degradation products) was
performed using UV-visible spectroscopy and Ion Distribution technique.
The Log B value obtained from the complexation studies at 336 nm for 1 = 0. I Ni NaClO4 and
I = 0.01 M NaClO4, falls within a range of 3.48 to 3.74 for the standard reference material
(Gluconic Acid), and within I .87 to 2.3 I, and I .6 to 2.01, respectively for the degradation
Products ISA (A) and ISA(N).
The ion distribution studies showed that:
• In (he absence of the degradation product ISA and at pH = 3.68. 56. 17 % of Cu (II) was bound to the resin.
• In the presence of ISA and at 2.24 ≤ pH ≤ 3.09, 91.5 % of Cu (II) was hound to ISA and 8.5 % to the resin.
The negative logarithm of the acid dissociation constant of the degradation products inferred from Lloyd linear relationship, showed the presence of carboxylic group ---- COOH adjacent to OH group. On the other hand the ionic strength had no influence on the acid capacity of the degradation products because they described a monomeric system.
Description
A Thesis submitted to the Department of Chemistry, College of Science of the Kwame
Nkrumah University of Science and Technology, in Partial Fulfillment of the Requirements for the award of the Degree of Master of Science in Analytical Chemistry, 2005