Title:
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Adsorption of chromium (VI), aluminium and copper from synthetic multi-component systems
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Adsorption takes place whenever a solid surface is exposed to a gas or liquid, and is characterized by an
increase in fluid density near the interface. Adsorbents have attracted attention in the ongoing effort to
engineer materials that can effectively remove various pollutants from wastewaters. Carbon adsorbents are
a logical choice as an adsorption material due to their low costs and large surface areas. The adsorption of
chromium(VI), aluminium and copper onto commercial activated carbon was studied in a series of batch,
kinetic and column experiments. The adsorption of the three ions was studied separately followed by
studies of the competition between the ions in binary and ternary systems. The experimental data was
utilized to set up models for sorption of chromium(VI), aluminium and copper onto commercial activated
carbon. This was done to enhance the understanding of the governing processes controlling adsorption as
well as to develop a tool to predict the fate of chromium(VI), aluminium and copper in a calcareous
environment. To avoid the precipitation of the ions, the binary and ternary experiments were conducted
without pH adjustment. This thesis has used multiple analytical techniques in order to enhance the
knowledge of Cr(VI), AI(III) and Cu(II) binding to the activated carbon adsorbent and thus attempts to
interpret.the potential binding mechanisms. The changes in adsorbent functional groups and surface
topography after chromium binding were monitored using FT-IR and SEM/EDX analysis. The experimental
studies include: i) evaluation and characterisation of the commercial activated carbon; ii) evaluation and
optimisation of commercial activated carbon removal capability, kinetics and mechanisms toward Cr(VI), AI
(III) and Cu(II) via the batch, kinetic and continuous adsorption systems. From the pH studies, it was
observed that pH 2 produced the highest removal of chromium. The ternary solution at pH 2 showed less
removal of chromium than the other solutions suggesting that the combined -effect of Cu and AI metals was
more considerable. Two common adsorption isotherms, i.e. the Freundlich and Langmuir models As well as
Redlich-Peterson model were employed to describe the adsorptive characteristics of the activated carbon.
The adsorptive kinetic studies revealed that the adsorption of activated carbon followed the pseudo-second
order kinetic models, indicating the adsorption mechanism was dependent on the adsorbate and adsorbent
interaction.
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