#scichallenge2017 In our project, it was aimed to purify wastewaters containing methylene blue component and harmful to environment from methylene blue. For this purpose, synthetic methylene blue waste water was formed and chemically treated by photocatalysis.

1. Photocatalytic Degradation
of Synthetic Wastewaters
Containing Stain
Berat KARATAŞ
Seher Elif MEKİK

2. THE GOAL OF THE PROJECT
In our project, it was aimed to purify wastewaters containing methylene blue
component and harmful to environment from methylene blue. For this purpose,
synthetic methylene blue waste water was formed and chemically treated by
photocatalysis.

3. METHOD
• Photocatalysis
Photocatalytic means, in words, self-cleaning with light. Photocatalysis is also a generic term for all of the
methods used in photocatalytic reactions. These methods involve the conversion of the catalysts activated
by ultraviolet light and the harmful substances in the waste water to harmless substances in the
environment in which they are contained.

4. • Preparation of Standard Solutions
• In order to examine the opening of the methylene blue in the spectrophotometer, a graph of the
absorption and concentration of the methylene blue is needed. For this plot, 7 different standard
solutions were prepared with molarities of 0.005 mM, 0.0075 mM, 0.01 mM, 0.015 mM, 0.02 mM,
0.03 mM, 0.04 mM.

5. Absorption of these solutions in 660 nm spectrophotometer
it was measured. As a result of this measurement,
and a chart of constants was obtained.
According to the Beer Lambert Act,
the concentration linear equation is as follows
it was found.
y = 40735x + 0,0017
R² = 0,9972
Concentrations using absorption data were obtained by the following example calculation.
y=1.2 (measured absorption)
𝑦 =
(1.2 − 0.0017)
40735
= 2.94 × 10−5
𝑀

6. • Preparation of Experimental Groups
After removal of the concentration and absorption graph, different experimental groups were prepared and
time-dependent absorption measurements were made. In these experimental groups, pH value is 5 and
temperature is 30-33 oC. There are three variable effects in the preparation of experimental groups; The
choice of light used for catalyst activation, the amount of catalyst and the pollution of the water were
investigated. Four different experimental groups were constructed to measure the effect of these variables on
the photocatalytic reaction.

7. A) 0.04 mM Methylene Blue + 1 g / L TiO2 Experimental Group
One solution was prepared with 0.04 mM methylene blue and 1 g of TiO2. This solution was left
under the ultraviolet lamp and the photocatalytic reaction was observed.
B) 0.04 mM Methylene Blue + 1 g / L TiO2 Experimental Group
One solution was prepared with 0.04 mM methylene blue and 1 g of TiO2. This solution was left
under the daylight LED lamp and the photocatalytic reaction was observed.
C) 0.08 mM Methylene Blue + 1 g / L TiO2 Experimental Group
One solution was prepared with 0.08 mM methylene blue and 1 g of TiO2. This solution was left
under the ultraviolet lamp and the photocatalytic reaction was observed.
D) 0.04 mM Methylene Blue + 0.5 g / L TiO2 Experimental Group
One solution was prepared with 0.04 mM methylene blue and 0.5 g TiO2. This solution was left
under the ultraviolet lamp and the photocatalytic reaction was observed.

8. RESULTS
• Finding Speed Equation
In order to have a velocity equation, the reaction reaction grade was separately taken as zero and one
was plotted. Zero and first order reaction reactions were also tried for the three experimental groups
performed under ultraviolet light. Zero and first order reaction equations are given below.
Zero Order Reaction
First Order Reaction

9. • Parameters to be Compared
Four different experimental groups were constructed to measure the effect of the three variables on
the reaction. The first and second experimental groups were prepared to measure the effect of
ultraviolet light on TiO2 activation. In the first and third experimental groups, the effect of the
amount of methylene blue, that is, the pollution of the water, on the cleaning time was compared. In
the first and fourth experimental groups, the effect of catalyst amounts on cleaning times was
compared.
A) The Impact of the Light Culet
In order to compare the synthetic wastewater prepared with 0.04 mM of methylene blue and 1 g of
TiO2 according to the effect of the light used in the experiment, one was observed under the
ultraviolet light lamp and the other was observed under the daylight LED lamp. Later, time-
dependent graphs were drawn with absorbance and concentration values obtained to compare
ultraviolet light with daylight LED lamp.

10. Time (min.) Ultraviolet Light - Absorption Ultraviolet Light - Concentration (M) Daylight - Absorption Daylight - Concentration (M)
0 1,627 3,99E-05 1,89 4,64E-05
15 1,336 3,28E-05 1,54 3,78E-05
30 0,602 1,47E-05 1,58 3,87E-05
45 0,45 1,10E-05 1,529 3,75E-05
60 0,449 1,10E-05 1,567 3,84E-05
75 0,312 7,62E-06 1,503 3,69E-05
90 0,328 8,01E-06 1,46 3,58E-05
105 0,246 6,00E-06 1,45 3,56E-05
120 0,098 2,36E-06 1,452 3,56E-05
135 - - 1,347 3,30E-05
150 - - 1,357 3,33E-05
165 - - 1,342 3,29E-05
180 - - 1,369 3,36E-05
195 - - 1,245 3,05E-05
210 - - 1,335 3,27E-05
225 - - 1,274 3,12E-05
240 - - 1,231 3,02E-05
Absorption and concentration values of daylight versus ultraviolet light.

11. Absorption Chart Concentration Chart
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300
Absorption
Time (min.)
UV Lamp

12. • Zero-Order Reaction Assumption
Since the obtained equation gives the slope
velocity constant, the velocity constant is
subtracted from the following equation to find
0.3 × 10−6
𝑀 𝑚𝑖𝑛−1
.
𝑦 = −3 × 10−7
𝑥 + 3 × 10−5

13. • First-Order Reaction Assumption
Since the obtained equation gives the slope
velocity constant, the velocity constant is
found to be 0.02 𝑚𝑖𝑛−1 from the equation
below.
𝑦 = 0.02𝑥 + 0.1071

14. B) Effect of Methylene Blue Concentration
Synthetic wastewater containing 0.04 mM and 0.08 mM methylene blue was added to 1 g of
TiO2 to effect methylene blue concentration treatment. Then the wastewater was treated
with ultraviolet light. Later, time-dependent graphs were drawn with absorbance and
concentration values obtained to compare methylene blue concentrations.

15. Time (min.)
0.00004 Methylene Blue -
Absorption
0.00004 Methylene Blue -
Concentration (M)
0.00008 Methylene
Blue -
Absorption
0.00008 Methylene Blue -
Concentration (M)
0 1,627 3,99E-05 2,384 5,85E-05
15 1,336 3,28E-05 1,601 3,93E-05
30 0,602 1,47E-05 1,48 3,63E-05
45 0,45 1,10E-05 1,185 2,90E-05
60 0,449 1,10E-05 1,023 2,51E-05
75 0,312 7,62E-06 1,005 2,46E-05
90 0,328 8,01E-06 0,722 1,77E-05
105 0,246 6,00E-06 0,717 1,76E-05
120 0,098 2,36E-06 0,652 1,60E-05
185 - - 0,12 2,90E-06
200 - - 0,099 2,39E-06
Absorption and concentration values of the comparison of methylene blue
concentrations

16. Absorption Chart Concentration Chart

17. • Zero-Order Reaction Assumption
Since the obtained equation gives the slope
velocity constant, the velocity constant is
derived from the following equation and is
found to be 0.2 × 10−6 𝑀 𝑚𝑖𝑛−1.
𝑦 = −2 × 10−7 𝑥 + 4 × 10−5

18. • First-Order Reaction Assumption
Since the obtained equation gives the
slope velocity constant, the velocity
constant is found as 0.0152 𝑑𝑘−1 from
the equation below.
𝑦 = 0.0152𝑥 − 0.0796

19. C) Effect of the amount of catalyst (TiO2)
In order to observe the effect of the catalyst in the treatments we made, 1 and 0.5 g of TiO2
were added to the synthetic waste water containing 0.04 mM of methylene blue and two
solutions were formed. These solutions were then subjected to purification by placing them
under the ultraviolet light. Time-dependent graphs were then plotted with the absorption and
concentration values obtained to compare the amount of TiO2.

20. Time (min.)
1 gram of TiO2 -
Absorption 1 gram of TiO2 - Concentration (M) 0.5 grams of TiO2 - Absorb 0.5 g TiO2 - Concentration (M)
0 1,627 3,99E-05 1,67 4,10E-05
15 1,336 3,28E-05 1,456 3,57E-05
30 0,602 1,47E-05 1,312 3,22E-05
45 0,45 1,10E-05 0,7 1,71E-05
60 0,449 1,10E-05 0,614 1,50E-05
75 0,312 7,62E-06 0,595 1,46E-05
90 0,328 8,01E-06 0,432 1,06E-05
105 0,246 6,00E-06 0,430 1,05E-05
120 0,098 2,36E-06 0,292 7,13E-06
135 0,172 4,18E-06
150 0,094 2,27E-06
Absorption and concentration values of TiO2 content comparison

21. Absorption Chart Concentration Chart

22. • Zero-Order Reaction Assumption
Since the obtained equation gives the slope
velocity constant, the velocity constant is
subtracted from the following equation to
find 0.3 × 10−6 𝑀 𝑑𝑘−1.
𝑦 = −3 × 10−7 𝑥 + 4 × 10−5

24. CONCLUSION AND DISCUSSION
• Two different synthetic wastewater containing 0.04 mM of methylene
blue and 1 g of TiO2 were exposed to ultraviolet light and daylight led
lamp to observe the photocatalytic reaction effect of the light selection.
Compared to these two separate test groups, the synthetic waste water
exposed to ultraviolet light was turned on within 120 minutes, but almost
no opening was observed in the synthetic waste water below the daylight
LED lamp. Thus, ultraviolet light is needed to activate TiO2.

25. • As the concentration of methylene blue increases, water pollution increases. Photocatalytic
bleaching of synthetic wastewaters containing methylene blue at two different concentrations,
one of which is twice as high as the other, has been observed. As a result, 0.08 mM methylene
blue waste water was opened at 120 minutes while 0.08 mM methylene blue waste water was
opened at 200 minutes. Based on these data, it has been proven that the concentration of the
dyeing substances which give the waste water coloring effect on the photocatalytic process.

26. • Finally, the effect of the amount of catalyst on the photocatalytic
color development was observed. The methylene blue solution left
to be opened using 1 gram of TiO2 was treated in 120 minutes
while the test group using 0.5 grams took 150 minutes. Accordingly,
the effect of photocatalytic opening of the amount of catalyst was
observed. In addition, since the TiO2 is not soluble in water, it is
expected to precipitate the catalyst while reading the absorption
value, and more waiting time is observed when more catalyst is
used.

27. • In order to obtain the velocity equation, the reaction was assumed to be zeroth and first order,
and graphs were plotted accordingly. Since R2 on the graph shows the reliability of the
obtained trend line, the speed equation was chosen by choosing the one closest to 1. Given
this situation, the methylene blue photocatalytic reaction was considered as the reaction of the
first order, and the rate constant for the three experimental groups was calculated as follows.
Experimental Speed Constants
methods Experiment Group 1 Experiment Group 2 Experiment Group 3
Zero Order Reaction(M
min-1)
0.3 × 10−6
R2=0.777
0.2
× 10−6 R2=0.879
0.3
× 10−6 R2=0.864
First Order Reaction(min-1)
0.02
R2=0.913
0.015
R2=0.945
0.018
R2=0.949

28. RECOMMENDATIONS
As a result of our work, we have observed that photocatalysis works for the
treatment of wastewaters containing methylene blue. We can say that this method
can successfully treat other thiazin dyestuffs because it is included in the thiazin
class among the methylene blue dyestuffs and the method we use in our project
purifies the methylene blue.

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