Layered double hydroxides (LDH) are diverse materials with a characteristic
layered structure. As a result of the partial exchange of divalent cations with trivalent
ones, they consist of positively charged hydroxide layers, while anions are intercalated
between the layers to neutralize the charge. This structure gives these materials the ability
to exchange intercalated anions, which can be used for certain applications. Some LDHs
are also semiconductors, which leads to their photocatalytic properties. We can produce
mixed metal oxides by calcination of LDHs.
The aim of my diploma work was to synthesize zinc-aluminium LDH with intercalated
chloride ions, and zinc-aluminium LDH with intercalated carbonate ions. The synthesis
was carried out by the coprecipitation method at constant pH. Sols were prepared from
the synthesized LDHs by peptization, from which thin films were prepared by dip-coating
technique. The thin films were then thermally treated. The structure of the prepared LDHs
was determined by X-ray diffraction.
The sorption and photocatalytic properties of the thin films, thermally treated at 600°C,
were determined. The prepared thin films were immersed in a solution of Plasmocorinth
B dye of known concentration. Then the change of dye concentration with increasing time
was monitored using UV-Vis spectrophotometry. Sorption process was performed in the
dark, while the determination of photocatalytic properties was performed by irradiating
the described system with UV or visible light.
It was found that calcined thin films of Zn-Al LDH, intercalated with carbonate ions, are
an effective sorbent and a partially effective photocatalyst. Thermally treated thin films
of Zn-Al LDH with intercalated chloride ions are an ineffective sorbent, but a very
effective photocatalyst.
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