Hydrothermal sulfate for nitric oxide and formaldehyde. Difference

 

Hydrothermal
methodology was used to synthesize the photocatalytic zinc sulfate microtubes. In
a typical procedure,
2mmol of SnCl4·5H2O and 4mmol of ZnSO4·7H2O
were dissolved into 35mL of deionized water to form two transparent solutions,
respectively. The two solutions were mixed together, and then 2 g of cellulose
acetate (CA) was added to the above mixture under vigorous magnetic stirring
for 10 min. Then 0.5M NaOH solutions were added dropwise into the above mixed
solution until the pH of the suspension was adjusted to 10 under magnetic
stirring. After
heating this suspension in an autoclave for 2 days at 220°C and allowing it to
cool down, filtration was performed to separate the resulting precipitates.
These precipitates were then subjected to washing and drying. By using the same
methodology SnO2 as well as ZnO photocatalyst were also synthesized5.

Measurement of
photocatalytic activity by using continuous flow reactor and reverse phase
column

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Indoor air
pollutants

Degradation of
formaldehyde (HCHO) and nitric oxide (NO)

Continuous flow
reactor and reverse phase column was used to detect the photocatalytic activity
of zinc sulfate for nitric oxide and formaldehyde. Difference in concentration
of pollutants in inlet and outlet stream estimates the degradation activity of
photocatalyst. It has been shown in Fig. 6. that photocatalytic activity of Zn2SO4
microtubes is higher than other photocatalyst used for drawing a comparison i.e.
SnO2 as well as ZnO. As it can been seen from this plot the removal
rate of NO by Zn2SO4 was 69.9% as compare to 42.1% by ZnO
and 33.9% by SnO2.The main reaction involved in oxidation of NO has
been given in following equations. Nitrous and nitric acid are formed as a
result of reaction between NO and reactive radicals16.

NO  + 
4.OH                          NO2  +  H2O 

NO2
 + 
.OH                           NO3
 + 
H+

NO  +  NO2
+ H2O                       
2HNO2

NOX  +  .O2-                           NO3-                                      

 

Fig. 6. Plot betweem concentration of NO and irradiation time

It has been
shown in Fig. 7. that photocatalytic activity of Zn2SO4
microtubes is higher than other photocatalyst used for drawing a comparison
i.e. SnO2 as well as ZnO. As it can been seen from this plot the
removal rate of HCHO by Zn2SO4 was 26.4%. Photocatalytic
oxidation of formaldehyde involves a chain reaction that is regulated by
hydrogen peroxide, hydroxyl radicals and superoxide radical. As a result of
this reaction the product formed may be formic acid or carbon dioxide depending
upon the proportion of number of pollutant molecules adsorbed and holes
generated. The main reaction involved in oxidation of HCHO has been given in
following equations5, 17.

HCHO  +  H2O  +  h+                                   HCHOOH  +  h+     (pollutant molecules adsorbed > holes
)    

HCHO  +  H2O  +  h+                                   CO2  +  h+                (pollutant molecules adsorbed

x

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