DEVELOPMENT OF ANIONIC CLAYS FOR WATER TREATMENT
Tez Türü: Doktora
Tezin Yürütüldüğü Kurum: Imperial College of Science, Technology and Medicine, Faculty of Engineering, Chemical and Process Engineering, Birleşik Krallık
Tez Danışmanı: Dr. David Whıte
Tezin Onay Tarihi: 2000
Tezin Dili: İngilizce
Desteklendiği Program: Diğer
Özet:
The
main aim of this study is to investigate the feasibility of utilising
hydrotalcite and its derived products as ion-exchangers for the removal of
anionic impurities from aqueous solution. Hydrotalcite is a naturally
occurring, rarely found anionic clay. It has a positively charged layered
structure consisting of two metal oxide layers and an interlayer of carbonate
anions. Hydrotalcites can, therefore,
be used as ion-exchangers. However, the carbonate anion is highly selected by
natural hydrotalcite, making the ion-exchange capacity for other anions very
low. In this project synthetic
hydrotalcite, hydrotalcite-like compounds and thermally treated hydrotalcite
samples were prepared in order to increase ion-exchange capacities and remove
anionic impurities from waters.
The
thesis provides a literature review with an emphasis on hydrotalcite structure and
its environmental applications. The synthesis methods for synthetic
hydrotalcite and its derivatives have been also included. The physical structure and chemical
properties of these anionic clays were characterised using standard
characterisation techniques, such as X-ray diffraction, N2
adsorption and particle size analyses. The preliminary studies on the
characterisation of hydrotalcites indicated that the structure of the clay was
similar to those in literature. Ion-exchange behaviour of hydrotalcites were
also investigated by zeta potential measurements. The anion-exchange capacities
of hydrotalcites were determined by the most common anionic impurities. Tests
on humic acid as an example for organic pollutants were done as well. A series
of batch technique experiments have been carried out for this purpose. The
experimental data show the ability of synthetic hydrotalcites for the removal
of anionic impurities from water. An extended mechanism for co-precipitation in
parallel to ion-exchange mechanism have also been proposed. This mechanism is
used to explain some of the experimental findings. The thesis, finally, recommends
hydrotalcite-like compounds and modified hydrotalcite with a magnetic property
as good materials for water treatment in environmental engineering
applications.