(12d) Advanced Oxidative Degradation of Benzoic Acid and 4-Hydroxy Benzoic Acid in Aqueous Phase – a Comparative Study
AIChE Annual Meeting
2018
2018 AIChE Annual Meeting
Environmental Division
Advanced Oxidation Processes
Sunday, October 28, 2018 - 4:30pm to 4:50pm
Advanced
Oxidative Degradation of benzoic acid and 4-hydroxy benzoic acid in aqueous
phase a comparative study.
Bhavna
D Deshpandea*, Dr.M.K.N.Yenkieb, Dr.P.S.Agrawalc
a.
Laxminarayan Institute of
Technology.RTMNU,Nagpur.
b. Professor, LaxmiNarayan Institute of Technology.RTMNU,Nagpur.
c. Professor, LaxmiNarayan Institute of
Technology.RTMNU,Nagpur.
*For correspondence - dnd.bhavna@gmail.com
ABSTRACT
Risks to environment and
human health vary considerably depending upon the type and extend of exposure
to hazardous chemicals. Environment protection agencies characterize risk on
the basis of locally measured or predicted exposure scenarios[1].
Benzoic acid and 4-hydroxy benzoic acid are widely used in cosmetic, food
preservatives and pharmaceutical industries[2].
Anthropogenic releases of such chemicals into the environment are primarily
into water and soil. In the present study, advance oxidative processes namely
UV, dark,solar assisted Fenton were investigated for the degradation in
lab-scale photoreactor. The process being highly dependent on experimental parameters,
degradation studies were carried out in order to establish optimum experimental
conditions for the processes studied. The optimum degradation conditions for 4-HBA
by the photo Fenton process are at pH 3.5, [Fe2+] =7 ppm and [H2O2]/[4-HBA]
molar ratio = 2.2, whereas the optimum degradation conditions for BA by the
photo Fenton process are at pH 3.5, [Fe2+] =7 ppm and [H2O2]/[4-HBA]
molar ratio = 2.3.
Keywords:
Advanced oxidation processes; 4-hydroxybenzoic acid; water treatment.
METHODOLOGY
AOPs work on the principal of production of hydroxy radical
in situ, it serves as strong oxidizing agent to oxidize pollutants to nontoxic
inorganic products[4][5][6]. Generally
speaking, chemistry in AOPs could be essentially divided into three parts[3][7][8][9]:
·
Formation of ·OH
·
Initial attacks on target molecules by ·OH and their breakdown to
fragments;
·
Subsequent attacks by ·OH until ultimate mineralization.
Present work was
carried out as follows:
1) Since
both BA and 4HBA show strong absorption peaks in the UV region with high molar
extinction coefficients, UV spectrophotometry was used for the quantitative
determination of their concentration.
2) Optimization
of experimental parameters like pH, Fe++ ,Fe+++concentration
and temperature.
3) The
studied AOPs were also used to study its effectivity for the treatment of
industrial waste effluent from dairy.
RESULTS
Table 1:
Optimisation of amount of H2O2 forthe
oxidative degradation after 90 minutes.
AOP studied |
Substrate |
H2O2 ppm |
% degragation |
AOP studied |
Substrate |
H2O2 ppm |
% degragation |
H2O2+Fe2+ (UVFenton) |
BA |
504
|
45.980
|
H2O2+Fe2+ (UVFenton) |
4HBA |
400 |
62.010 |
560 |
57.879 |
450 |
54.246 |
||||
616 |
39.230 |
500 |
69.868 |
Table 2: Optimisation of amount of Fe2+/Fe+3 for the
oxidative degradation after 90 minutes.
Substrate |
||||||
Benzoic acid |
Fe2+ in ppm |
10 |
8 |
7 |
5.5 |
4 |
% Degradation |
29 |
34 |
57.8 |
37.312 |
49.22 |
|
Fe3+ in ppm |
10 |
8 |
7 |
5.5 |
4 |
|
% Degradation |
34 |
41.67 |
69.39 |
67.529 |
44.596 |
|
4HBA |
Fe2+ in ppm |
10 |
8 |
7 |
5.5 |
4 |
% Degradation |
44.760 |
52.123 |
69.868 |
63.201 |
60.270 |
|
Fe3+ in ppm |
10 |
8 |
7 |
5.5 |
4 |
|
% Degradation |
32.250 |
49.015 |
47.863 |
55.638 |
45.450 |
Table 3.Optimization of Fe2+/Fe3+
for solar Fenton after 90 min
BA Solar Fenton |
Fe2+ (4ppm) |
% Degradation 76.80 |
Fe3+ (4ppm) |
% Degradation 72.86 |
4HBA Solar Fenton |
Fe2+ (4ppm) |
% Degradation 95.25 |
Fe3+ (4ppm) |
% Degradation 83.55 |
Amid
the various processes dark Fenton, photo Fenton, dark Fenton like, photo Fenton
like and solar degradation, studies show that solar is most effective and
efficient process when applies to 4 hydroxybenzoic acid system as compared to
benzoic acid. This shows that substituted benzoic acid is easily degraded as
compared to benzoic acid itself. Batch systems were studied in the lab. Vis- UV
spectrophotometer (Labman) was use to study absorbance at specific interval.
Absorbance of benzoic acid and hydroxy benzoic acid was observed at 272nm and
245nm respectively. As H2O2 shows self-degrading, its degradation
was studied spectrophotometrically using sodium titanium oxalate at 420nm.
It
is observed, that with the increase in Fe ion concentration, % degradation
first increases then decreases, this can be due to the reduced transparency of
the solution, when excess of Fe ions get deposited in the reactor which thereby
requires a process of removal. Fenton process shows best results at acidic pH
(2.5 -3.5). Therefore, optimization is required. All the batch scale
experiments were carried out at room temperature. It is observed with the
increase in temperature, % degradation increases. In the beginning of reaction,
some colored intermediates are perceived which may lead to the increase in
absorption spectra, such intermediate is shot lived and soon degrade, which in
turn depends upon nature of pollute and the condition applied.
AOPs
are welcoming new trends, modified AOPs are more efficient and cost effective.
A lot of research on solar base system are ongoing. Use of non-metallic
elements are doped to enhance photocatalytic activity[10].
To increase the working pH range complex like Fe-EDTA[11],
Fe oxalate[12],
Fe-EDDS[13],
are introduced in waste water for quicker and complete degradation.
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