| Résumé: | The quality of drinking water is testified to be satisfactory in most developed countries.
However, the United Nations has reported that 783 million people do not have access to
safe drinking water. Furthermore, only 1% of available water resources can be used as
drinking water. One of the most common pollutants found in drinking water is atrazine
herbicide. Malaysia, being an active player in agriculture consumes large quantity of
atrazine and other pesticides. Atrazine is classified as low toxic herbicides but prolong
consumption leads to cardiovascular and mutagenic effects. The current technology is
via granulated activated carbon (GAC) however it leads to leaching, non-selective and
waste disposal costs. An alternative effective method is by photocatalytic degradation
using semiconductor photocatalyst. The key factor for a successful photocatalytic
activity is to sustain large concentrations of surface active radicals to oxidize pollutants
into simpler and less hazardous substance. In photocatalysis, TiO2 is a preferred
semiconductor as it is cheap, photo-active, stable and is non-toxic. However, the
photocatalytic ability of TiO2 is limited to only a small fraction of solar light (4%) and
hence hampers its activity. Numerous efforts are initiated to improve TiO2 properties
which include anion doping and most recent hydrogenation of TiO2. Nevertheless, the
photocatalytic activity of anion-doped TiO2 was only accessible under UV and visible
light. In addition, hydrogenated TiO2 was reported to possessed rapid electrons and
holes recombination although the optical response was extended towards the infra-red
region. In this work, hydrogenated F-doped TiO2 showed remarkable enhancement for
the photocatalytic degradation of atrazine by a factor of ~8.5 relative to as prepared
TiO2. Within 180 min of photocatalytic activity, more than 95 % of 0.5 mg/l atrazine
was removed. Atrazine removal was shown to exceed those of N,F co-doped TiO2 (85
%), hydrogenated TiO2 (70 %), N-doped TiO2 (70 %), F-doped TiO2 (40 %) and F127-
TiO2 (35 %). F-doped TiO2 was prepared using pluronic F127 as surfactant and
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trifluoroacetic acid as the fluorine precursor, followed by hydrogenation at 500 °C and 1
atm to obtain hydrogenated F-doped TiO2. Acid catalyzed sol-gel method was used to
prepare F-doped TiO2 and other photocatalysts as it allows efficient control of purity,
homogeneity, crystal phase and particle size. In addition, sol-gel method does not
require needs of special equipment and can be conducted at low temperature.
Hydrogenated F-doped TiO2 showed enhanced solar light absorption with ability to
absorb light in the UV, visible and infra-red region. The sustainability of photogenerated
electrons and holes on the photocatalyst surface enables larger formation of
active surface radicals. Furthermore, the synergy between hydrogenation and F-doping
modifies the morphology, crystal structure, surface charge, hydrophilicity, defects and
surface area which were shown to favor the photocatalytic activity. High photocatalyst
reusability up to 10th cycles was achieved. Hydrogenated F-doped TiO2 could serve as a
new potential photocatalyst and thus supports the water industry for the abatement of
recalcitrant organic pollutants. Furtherance, this leads to the possibility in providing safe
drinking water by adapting a more sustainable and feasible approach.
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