Solar photocatalytic degradation of food dye (tartrazine) using zinc oxide catalyst / Nor Aireen Abd Rahim

Food dyes are used in food processing industries as coloring and additive so that
the food can be stored for a long time. The effluent discharged from the industries
has become a serious issue as it can cause water pollution, harm aquatic life,
nature and also human beings. Solar photocatalytic degradation was widely used
to degrade most of the dyes in wastewater due to its high effectiveness. The
objectives of this study are to investigate the effectiveness of degradation of
Tartrazine using the photocatalytic process by using ZnO as photocatalyst and
sunlight as the irradiation source. Other than that, this study is conducted to
compare the percentage degradation of Tartrazine at different conditions which
are amount of photocatalyst, pH of dye solution, exposure time and presence and
absence of sunlight and photocatalyst. The degradation of Tartrazine was analyzed
by using UV-Vis spectrophotometer. Firstly, to determine the optimum weight of
ZnO, ZnO was added at different weights which were 0 mg, 10 mg, 20 mg, 30
mg, 40 mg and 50 mg. Then, the optimum pH of dye solution was determined by
using different pH which were pH 6, pH 7, pH 8, pH 9, pH 10 and pH 11. From
the absorbance obtained from UV-Vis spectrophotometer, the concentration of
dye in the solution was calculated. Then, the percentage of degradation can be
calculated by using the concentration of dye. The amount of photocatalyst ZnO
must be added at the optimum weight which was 20 mg so that more hydroxyl
radical produced. The optimum pH for the Tartrazine solution was pH 6. The
percentage of degradation of Tartrazine decreased as the pH of the solution was
increased. For the degradation with ZnO catalyst and with solar radiation, the
optimum time obtained was lowest which was 1 hour. This condition also was the
most effective condition compared to other condition because the percentage of
degradation was the highest (93.91±0.57)%. The other conditions used were
presence of catalyst absence of sunlight, absence of catalyst presence of sunlight
and absence of both catalyst and sunlight. Both catalyst and solar radiation were
needed to achieve highest efficiency of photocatalytic process because both
helped in the formation of hydroxyl radical.