(12d) Advanced Oxidative Degradation of Benzoic Acid and 4-Hydroxy Benzoic Acid in Aqueous Phase – a Comparative Study

Advanced
Oxidative Degradation of benzoic acid and 4-hydroxy benzoic acid in aqueous
phase – a comparative study.

Bhavna
D Deshpande^a*, Dr.M.K.N.Yenkie^b, Dr.P.S.Agrawal^c

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.

       
Table 2: Optimisation of amount of Fe²⁺/Fe⁺³  for the
oxidative degradation after 90 minutes.

            Table 3.Optimization of Fe²⁺/Fe³⁺
for solar Fenton after 90 min

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.

REFERENCES

[1]      NHS
Choices, “Health A-Z - Conditions and treatments,” www.nhs.uk, 2016.
[Online]. Available: http://www.nhs.uk/Conditions/Pages/hub.aspx.

[2]      “BENZOIC ACID
AND SODIUM BENZOATE.” .

[3]      C. L. P. S.
Zanta and C. A. Martínez-Huitle, “Degradation of 2-hydroxybenzoic acid by
advanced oxidation processes,” Brazilian J. Chem. Eng., vol. 26, no. 3,
pp. 503–513, 2009.

[4]      W. Gernjak, T.
Krutzler, A. Glaser, and S. Malato, “Photo-Fenton treatment of water containing
natural phenolic compounds Photo-Fenton treatment of water containing natural
phenolic pollutants,” vol. 50, no. FEBRUARY, pp. 71–78, 2003.

[5]      W. H. Glaze,
“Reaction products of ozone: A review,” Environ. Health Perspect., vol.
Vol. 69, pp. 151–157, 1986.

[6]      W. H. Glaze,
J.-W. Kang, and D. H. Chapin, “The Chemistry of Water Treatment Processes
Involving Ozone, Hydrogen Peroxide and Ultraviolet Radiation,” OZONE Sci.
Eng., vol. 9, pp. 335–352, 2016.

[7]      V. K. Saharan,
D. V. Pinjari, P. R. Gogate, and A. B. Pandit, “Advanced Oxidation Technologies
for Wastewater Treatment: An Overview,” in Industrial Wastewater Treatment,
Recycling and Reuse, 2014, pp. 141–191.

[8]      M. Cheng et
al., “Hydroxyl radicals based advanced oxidation processes (AOPs) for
remediation of soils contaminated with organic compounds: A review,” Chemical
Engineering Journal, vol. 284. pp. 582–598, 2016.

[9]      Y. Deng and R.
Zhao, “Advanced Oxidation Processes (AOPs) in Wastewater Treatment.,” J.
Ind. Eng. Chem., vol. 1, pp. 167–176, 2015.

[10]    M. M. Huber et
al., “Oxidation of pharmaceuticals during ozonation of municipal wastewater
effluents: A pilot study,” Environ. Sci. Technol., vol. 39, no. 11, pp.
4290–4299, 2005.

[11]    G. Ghiselli, W.
F. Jardim, M. I. Litter, and H. D. Mansilla, “Destruction of EDTA using Fenton
and photo-Fenton-like reactions under UV-A irradiation,” J. Photochem.
Photobiol. A Chem., vol. 167, no. 1, pp. 59–67, 2004.

[12]    J. Jeong and J.
Yoon, “pH effect on OH radical production in photo/ferrioxalate system,” Water
Res., vol. 39, no. 13, pp. 2893–2900, 2005.

[13]    L. Clarizia, D.
Russo, I. Di Somma, R. Marotta, and R. Andreozzi, “Homogeneous photo-Fenton
processes at near neutral pH: A review,” Appl. Catal. B Environ., vol.
209, pp. 358–371, 2017.