Kinetics of Sodium Sulphite Oxidation Catalyzed by CO₂O₃ and Inhibited by Ethylene Glycol

 

S. Begam, F. Hussain, Jaibir Singh, A. K. Sharma, D. S. N. Prasad*

Department of Chemistry,Govt. P. G. College, Jhalawar-326001, Rajasthan (India)

*CorrespondingAuthorE-mail:dsnp308@gmail.com

The kinetics of the ethylene glycol inhibited Co₂O₃catalysed autoxidation of sulfur(IV) in alkaline medium has been studied and based on the observed results rate law and a free radical mechanism has been proposed.

-d[S(lV)]	=	(k1+ k2[Co2O3]) [S(lV)]
dt		1 + B [ethylene glycol]

 

 

 

1. INTRODUCTION:

The rapid industrial development on all fronts has led to several environmental pollution phenomena and the chemistry is at the back of all these. Of these, acid rain, stratospheric ozone depletion, greenhouse effect and carbon monoxide pollution are the most prevalent. Here we are concerned mainly with the phenomenon of acid rain which is of common occurrence in several industrially developed countries in northern hemisphere. In our own country, the level of SO₂ in atmospheric environment is increasing and, therefore, the danger of acid rain cannot be simply wished away[1].

 

A large number of organic and inorganic chemical species are released in to the atmosphere by anthropogenic and natural sources. The subsequent photochemical and thermal reactions of these species in gas and aqueous phases formthe backbone of the atmospheric chemistry [2].

 

The catalytic role of several metal oxides such as CoO [3]; Co₂O₃[4];Ni₂O₃[5]; CuO[6]; MnO₂ [7]; and Cu₂O [8]; waste product of water treatment plants containing CaO[9-10] cobalt ions (Q. Li, 2014) [11] and carbon nanotubes (Q. Li, 2017) [12], transition metal catalyst (L. Wang, 2015) [13] and cobalt based molecular sieves (L. Wang, 2016) [14] has been reported. The sulfur (IV)-autoxidation reaction is known to proceed via both radical and non-radical mechanisms. (Martin et al) [15]An interesting feature of many radical reactions is that, the reaction rate isinhibitedby organics such as acetic acid, oxalic acid (Irena Wilkosz et al) [16], Alcohols(Ziajka et al), [17] Carboxylic acid (Bostjanpodkrojsek et al[18] formic acid, isopropyl alcohol, isoamyl alcohol, aniline, benzamide, sodium benzoate (Sharma et al⁾ [19-24]ascorbic acid, (L. Wang, 2013)[25] organic compounds, [26] VOC,[27] diesel truck particles[28].

 

In Indian sub-continent the pH of the rain water lies in the range 6.5-8.5 This necessitates a study of the sulfur(IV) autoxidation in the alkaline pH range. In most of the studies the role of organics has been reported in the metal ion catalysed autoxidation of sulfur(IV) in aqueous medium. Very few studies are available on the role of organics on the metal oxide catalysed autoxidation of sulfur(IV) in aqueous medium.This led us to investigate the kinetics of sulfur(IV) autoxidationcatalyzed byCo₂O₃in the pH range 7.8-9.4. The effect of sodium benzoate hasbeen studied inalkaline media to delineate the nature of the mechanism.

 

2.      EXPERIMENTAL:

The experimental procedure was exactly the same as described earlier[29] and is briefly given here. All chemicals used were of reagent grade and their solutions were prepared in double distilled water. The reactions were conducted in 0.15-L Erlenmeyer flasks, open to air and to allow the passage of atmospheric oxygen. The flask was placed in a beaker, which had an inlet at the lower part and an outlet at the upper part for circulating thermostatic water for maintaining the desired temperature, 30±0.1^oC. The reactions were initiated by adding the desired volume of standard Na₂SO₃ solution to the reaction mixture containing other additives such as buffer and catalyst oxide. The reaction mixture was stirred continuously and magnetically at 1,600±100 rpm to allow the passage of atmospheric oxygen and to save the reaction from becoming oxygen mass transfer controlled. The kinetics were studied in buffered medium, in which the pH remained fixed throughout the entire course of reaction. For this purpose, 10 cm³ of buffer made from Na₂HPO₄ (0.08 mol L^–1) and KH₂PO₄ (0.02 mol L^–1) for alkaline mediumwere used (total volume 100m³) for obtaining the desired pH. The kinetics were followed by withdrawing the aliquot samples periodically and titrating the unreacted S(IV) iodometrically in slightly acidic medium as described earlier. The reproducibility of the replicate measurements was generally better than±10%. All calculations were performed in MS Excel.

 

3. Product Analysis:

The qualitative tests showed sulphate to be the only oxidation product. For quantitative analysis , the reaction mixtures containing catalyst and S(IV) in appropriately buffered solutions were constantly stirred for a sufficiently long time so as to ensure complete oxidation of sulphur(IV). When the reaction was complete, Co₂O₃ was filtered out and sulphate was estimated gravimetrically by precipitating sulphate ions as BaSO₄ using standard procedure [30].

 

The product analysis showed the recovery of sulfate to be 98±2% in all cases in agreement with Eq.1.

S(IV)+0.5O₂S(VI)                                                              (1)

 

4. RESULTS:

4.1Preliminary Investigation:

The kinetics of both uncatalyzed and Co₂O₃ catalyzed reaction were studied in alkaline medium in the pH range 7.3-8.8. In both cases, the kinetics was first order in [S(ІV)] and the treatment of kinetics data is based on the determination of first order rate constant k_1, from log [S(ІV)] versus time , t , plots as shown in Fig 1

 

time, min

Fig. 1       The disappearance of [S(IV)] with time in air-saturated suspensions of 100 mlatS (IV)]=2×10^-3 mol L^-1,at 30° C and pH=7.86, (■)[Co₂O₃]=20 mg, [ethylene glycol]=0 ml, (l) uncatalysed and without ethylene glycol (▲) [Co₂O₃]=20mg, [ethylene glycol]=1.5×10^-3mol L^-1

 

4.2 Uncatalysed Reaction:

In this study the reaction was studied without adding Co₂O_3. As it is well known that the uncatalysed reaction is initiated by the trace metal ion impuritiespresent in the reagent samples and distilled water used for the preparationof solutions, so the uncatalysed reaction is initiated by these trace metal ion impurities particularly transition metal ions.

 

4.3Dependence of Sulphite:

The detailed dependence of the reaction rate on [S(ІV)] was studied by varyingit is in the range 1×10^-3 mol dm^-3 to 6×10^-3 mol dm^-3 at pH=7.34, t=30°C in phosphate buffer medium. The kinetics was found to be pseudo first order in [S(IV)] as shown in fig.1, log [S(IV)] v/s. time plots were linear.The value of first order rate constant, k₁ are given in Table-1, are seen to be independent of [S(ІV)] in agreement with the rate law (2).

-d [S(IV)] /dt=k₁ [S(IV)].(2)

 

Table -1The values of k₁ for uncatalysed reaction at different [S(ІV)]atpH=7.34 and t=30⁰C

[S(IV)] mol dm-3	104k1 s-1
0.001		10.5
0.002		10.6
0.004		10.1
0.006		10.5

 

4.4. [Ethylene glycol] dependence:

The major aim of the present study was to examine the effect of organic inhibitors on the autoxidation of S(IV) in alkaline medium so for this purpose ethylene glycol was chosen as the second inhibitor. On varying the [ethylene glycol] from6×10^-3to 1.2×10^-3mol L^-1, the rate of the reaction become decelerated. The nature of the [S(IV)]–dependence in presence of ethylene glycol did not change and remained first order. The first order rate constant k_inhin the presence of ethylene glycol were defined by the following rate law (3)

 

kinh[S(IV)]

=

-d[S(lV)]                                                                                 (3)

dt                           

 

 

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

[ethylene glycol] mol L-1

Fig. 2 Effect of ethylene glycol at [S(IV)]=2×10^-3 mol L^-1 and at 30°C, inphosphate buffered medium

 

The valuesof first order rate constantk_inhin the presence of ethylene glycol decreased, with increasing ethylene glycol in agreement with the rate law.

 

k_inh=k₁ /(1+B[ethylene glycol])                                          (4)

 

where

B is inhibition parameter for rate inhibition by ethylene glycol.

 

By rearranging the equation (4) we get

 

1/ k_inh=1/ k₁ +B[ethylene glycol]/ k₁                                                  (5)

 

In accordance with eq.(5) the plot of 1/ k_inhversus [ethylene glycol] was found to be linear with a non-zero intercept, fig. 4.2. Where intercept=1/k₁and slope =B/k₁.The values of 1/ k₁and B/ k₁were found to be 1.33×10³ s and 2.27×10⁶mol^-1L at pH=7.86, and t=30ºC. The value of slope/intercept gives us the value of inhibition parameter B, which was found to be1.69×10³ mol^-1 L.

 

4.5 Co₂O₃-Catalysed Reaction:

The kinetics of Co₂O₃-catalysedautoxidation ofS(IV) wasstudied in alkaline medium in the absence of inhibitor ethylene glycol.

 

[ethylene glycol] mol L^-1

 

 

 

4.6 [S(IV)] Variation:

The dependence of reaction rate on [S(IV)] was studied by varying [S(IV)] from 1×10^-3 to 10×10^-3 mol L^-1 at two different but fixed [Co₂O₃] of 0.1 and 0.2 g L^-1 atpH=7.86 and t=30°C. The kinetics was found to be first order in[S(IV)]as shown in Fig 1 and log [S(ІV)] versus time plots were linear.

 

4.7 [Co₂O₃] Variation:

The effect of [Co₂O₃]on the rate was studied and the values of first order rate constants k_cat, for S(ІV)-autoxidation was determined at different [Co₂O₃ ] at pH=7.34, t=30°C. The results are given in Table 2.

 

Table. 2The value of k_cat at different [Co₂O₃] at pH=7.80 and t=30ºC

Co2O3(g L-1)	103kcat s-1
0.1	8.8
0.2	13.7
0.3	16.9
0.4	21.8

 

It follows a rate law given by (6)

-d[S(IV)] /dt=k_cat [SIV)]=(k₁+k₂[Co₂O₃ ]) [S(IV)]            (6)

k_cat=k₁+k₂[Co₂O₃ ])                                                               (7)

 

The values of intercept is equal to k₁ and slope is equal to k₂ were found to be 5.1×10^-4 s and 4.01×10^-3 mol^-1 dm^-3 s

 

4.8 Variation of pH:

Variation in pH in the range 7.4 to 8.8 in phosphate buffer medium showed the rate to be independent of pH.The results are given in Table 3. The effect of [buffer] was examined by varying the concentration of both Na₂HPO₄and KH₂PO₄ in such a way that the ratio [Na₂HPO₄]/[KH₂PO₄] remained same, so that pH remained fixed. The values showed that the rate of the reaction to be insensitive to the buffer concentration in Table 3.

 

Table 3 Variation of pH at [Co₂O₃]=0.2 g L^-1,[ethylene glycol]=1.2×10^-3mol L^-1, [S(IV)=2×10^-3 mol L^-1and t=30ºC

[S(IV)]molL-1	[Co2O3] g L-1	[ethylene glycol] molL-1	pH	temp.	104kcat k1+k2[Co2O3]
0.002	0.2	0.0012 M	7.86	30°C	5.84
0.002	0.2	0.0012 M	8.20	30°C	5.90
0.002	0.2	0.0012 M	8.70	30°C	5.78
0.002	0.2	0.0012 M	9.27	30°C	5.82

 

4.9. Variation of ethylene glycol:

To know the effect of ethylene glycol on Co₂O₃-catalysed autoxidation of S(IV), ethylene glycol variation was carried out from.6×10^-3to 1.2×10^-3mol L^-1at two different [Co₂O₃] that is 0.1 and 0.2 g L^-1 but fixed [S(IV)]=2×10^-3 mol L^-1at pH=7.86 and t=30°C.The results indicates that by increasing the [ethylene glycol] the rate become decreases.

A detailed study was carried out for the dependence of rate on [S(IV)], [Co₂O₃], and pH on the reaction in the presence of ethylene glycol revealed that the kinetics remain first order both in [S(IV)] and [Co₂O₃] and independent of pH.

 

Fig. 3Effect of [Co₂O₃] at ethylene glycol=1.2×10^-3 mol L^-1, pH=7.86 and at t=30°C, in phosphate buffered medium

 

A plot between [Co₂O₃] vs first order rate constant is linear (fig.4.4) with non-zero intercept.The value of intercept and slope are found to be 5.27×10^-5 s^-1 and2.68×10^-5 g^-1 L s^-1respectively.Depend upon the observed results the reaction follows the following rate law in the presence of ethylene glycol.

 

-d[S(lV)]	=	(k1+ k2[Co2O3]) [S(lV)]	(8)
dt		1 + B [ethylene glycol]

 

Where kinh	=	k1+ k2[Co2O3])	=	kcat
		1 + B [ethylene glycol]		1+B [ethylene glycol]

 

1	=	1+B [ethylene glycol]
kinh		kcat

 

1	=	1	+	B [ethylene glycol]
kinh		kcat		kcat

 

Table 4The variation of [ethylene glycol] at[S(IV)]=2×10^-3mol.L^-1, [Co₂O₃]=0.1 g L^-1, t=30°C, and pH = 7.86.

[ethylene glycol ]	kinh s-1	1/kinh s
0	8.8×10-4	1137
.6×10-3	5.57×10-4	1590
.8×10-3	4.12×10-4	2110
1×10-3	4.08×10-4	2451
1.2×10-3	3.06×10-4	3049

 

By plotting a graph between 1/k_inhvs [ethylene glycol] gives a linear line with non-zero interceptfig. 4.5.The value of intercept=1/k_cat and slope=B/k_cat from the graph these values are found to be 955×10³ sand 1.54×10⁶mol^-1 Lsrespectively.From these values the value of inhibition parameter B can be calculated, inhibition parameter B=slope/intercept that is B=1.61× 10³mol^-1 L.

 

4.10 Effect of temperature:

To calculate the apparent empirical energy of activation the values of k_obs were determined at three different temperatures in the range 30°C to 40°C. The results are given in table 4.21.By plotting a graph between log kversus 1/t gives us the apparent energy of activation determined to be28.05 kJ mol^-1.

 

Table.5 Effect of temperature on k_obsair saturated suspensions at [S(IV)]=2×10^-3 mol L^-1, [Co₂O₃]=0.2 g L^-1, [ethylene glycol]=1.2×10^-3 mol L^-1,t=30°C, and pH=7.86.

t °C	104kobs,s-1
30	5.84
35	8.13
40	11.33

 

5. DISCUSSION:

KH

In aqueous solution SO₂ is present in four forms, SO₂.H₂O, HSO₃^-,SO₃^2-and S₂O₅^2-,governed by the following equations.

 

SO₂(g)+H₂OSO₂.H₂O(aq)………...(9)

	Kd(1)

 

 

SO₂.H₂O(aq)HSO₃^-+H⁺………….…(10)

	Kd(2)

 

 

HSO₃SO₃^-+H⁺(11)

	K(3)

 

 

2HSO₃^-S₂O₅^2-+H₂O…………….(12)

 

K_H isHenry's constant and K₁, K₂ are acid dissociation constants. K₃ is the formation constant for S₂O₅^2-at 25ºC the values are K_H=1.23 mol L^-1atm^-1, K₁=1.4×10^-2, K₂=6.24×10^-8, and K₃=7.6×10^-2. In this experimental study in pH range (7.86-9.27), S(IV) would be largely present as SO₃^2-. Since the rate of reaction is nearly independent of pH, we have considered only SO₃^2-species to be reactive in the subsequently. In several transition metal oxide catalysed heterogeneous aqueous phase auto oxidation reactions of sulfur(IV), the formation of surficial complexes by adsorption of sulfur(IV) and O₂ on the particle surface and oxidation of sulfur(IV) take place through the intervention of multiple oxidation states has been proposed. In the heterogeneous solid–liquid phase reaction of MnO₂ and S(IV),Halperin and Taube [31] proposed that the sulfite ion makes bond through oxygen atom at the surface of solid MnO₂. In the present study, the dependence of oxygen shows that the formation of surficial complex by adsorption of O₂ on the particle surface of Co₂O₃ through the fast step.

 

In alkaline medium the rate of Co₂O₃ catalysed reaction is highly decelerated by the addition of ethylene glycol like that of ethanol reported by Gupta et al [32] this indicates the operation of a radical mechanism involving oxysulfur free radicals, like SO₃−•, SO₄−•and SO₅−•The inhibition is caused through the scavenging of SO₄−•by inhibitors such as ethanol and benzene, etc.

 

Backstrom (1934)[33]proposed radical chain mechanism of alcohol inhibited oxidation reaction between sodium sulphite and oxygen. The direct experimental evidence for the reactivity of sulphoxy radicals with respect to alcohols were reported by (Hayon et al., 1972)[34]Which resulted in proving the ability of these compounds to react with SO₄−•, whereas reactions with SO₃−• and SO₅−• occurred unimportant.

 

The methanol inhibition of the uncatalysed autoxidation of HSO₃^-was investigated by Connick et al .(1995)[35] to shed more light on a mechanism of initiation in the absence of transition metal ions. Connick and Zhang (1996)[36] showed that in the presence of manganous ions the inhibition by methanol is more complex than indicated by simply adding to the overall reaction mechanism the step by which sulfate radicals are scavenged.

 

As reported by Sharma et al[37-39]. a radical mechanism operates in those reactions in which the inhibition parameter lies the range 10³-10⁴. In this study the value of inhibitor parameter is found to be 1.61×10³, which lies in the same range. This strongly supports the radical mechanism. For the Co₂O₃ –catalysed reaction in presence of ethylene glycol. Based on the observed results including the inhibition by ethylene glycol, the following radical mechanism is proposed which similar to that proposed by Gupta et al in the ethanol inhibition of the CoO catalysed reaction.

 

Co₂O₃+SO₃^2-                                   Co₂O₃.SO₃^2-                                                                                                                                              (13)

Co₂O₃.SO₃^2-+O₂                                 Co₂O₃.SO₃^2-. O₂                                                                                                                                    (14)

Co₂O₃.SO₃^2-.O₂                                                      Co₂O₃+SO₃−•+O₂^-                                                                                                                              (15)

SO₃−•+O₂                                                                                               SO₅−•                                                                                                         (16)

SO₅−•+SO₃^2-                                                           SO₅^2-+SO₃−•                                                                                                                                            (17)

SO₅−•+ SO₃^2-                                                                                       SO₄−•+SO₄^2-                                                                                             (18)

SO₅ ^2-+SO₃^2-                                                                                          2SO₄^2-                                                                                                        (19)

SO₄−•+SO₃^2-                                                                                        SO₄^2-+SO₃−•                                                                                             (20)

SO₄−•+x                                                                 Nonchain product                                                                                   (21)

SO₄−•+ethylene glycol                                         Nonchain product                                                                                   (22)

 

In the mechanism, no role is assigned to O₂^-, which is also known to react with sulfur (IV) slowly. It may disproportionate to form H₂O₂ and O₂ or may be scavenged by impurities. By assuming long chain hypothesis and steady state approximation d[SO₃^-]/dt, d[SO₄^-]/dt and d[SO₅^-]/dt to zeroit can be shown that the rate of initiation is equal to the rate of termination. (Eq. 23)

 

k₁[Co₂O₃(SO₃^2-)(O₂)]=

{k₇[X]+k₈[ethyleneglycol]}[SO₄−•](23)

 

Since the reaction is completely stopped in the presence of [ethylene glycol] at 5 x 10^-2mol L^-1. so The steps (15) and (19) appear to be unimportant.

 

The contribution of propagation reaction (18) been significant in the Co₂O₃ catalysed. Reaction where the autoxidation reaction should have occurred even in the presence of highethylene glycol concentration. But this is not true and the reaction is completed seized in the presence of high concentration of ethylene glycol. This led us to ignore the step (18) and assume only the rate of reaction given by equation                .(24)

 

-d[S(IV)]/dt=R_cat=k₆ [SO₄−•] [SO₃^2-]                            (24)

By substituting the value of (SO₄−•) we get

	Rcat=

 

k₆ k₁ [Co₂O₃. SO₃^2–.O₂] [SO₃^2-]      (25)

                                 k₇[x]+k₈ [ethylene glycol]

 

From equilibrium 13 and 14

	Rcat=

 

                k₆                   K₂ K₁ [Co₂O₃] [S(IV)] [O₂](26)

                {1 + k₁[S(IV)] {k₇ [x]+k₈ [ethylene glycol]}

At fixed O₂, replacing k₆ k₁ k₂[O₂] by k¹ we get

	Rcat=

 

k¹                   k¹ [Co₂O₃] [S(IV)](27)

{1 + k₁[S(IV)] {k₇ [x] + k₈ [ethylene glycol]}

Since we observe a clean cut first order in [S(IV)], The value of K₁ [S(IV)]<<1 so the above rate law can be reduce to

	Rcat=

 

                k¹[Co₂O₃] [S(IV)] (28)

                                k₇ [x]+k₈ [ethylene glycol]

Gupta et al proposed a similar mechanism for the CoO catalysed autoxidation of sulfur dioxide inhibited by ethanol, which lead to the same rate law. By comparing derived rate law with the experimental rate law we observe the similarity in these two.

 

The calculated value of inhibition constant B is 1.61×10³mol^-1 L. which is in the range of10³ to 10⁴. So on the base of calculated value of B, we concluded that ethylene glycol act as an free radical scavenger in the Co₂O₃ catalysed autoxidation of aqueous sulfur dioxide in alkaline medium and a free radical mechanism can operate in this system[40].

 

6.      CONCLUSIONS:

The role of ethylene glycol act as an inhibitor inCo₂O₃catalysed autoxidation of SO₂ in alkaline medium has been found, and based on the observed results rate law a free radical mechanism has been proposed.

 

-d[S(lV)]/dt=

(k₁+k₂[Co₂O₃])[S(lV)]/1+B[ethylene glycol]

 

Based on the experimental results, rate constants and orders of the reactions were determined. The reaction order in SO₂ was pseudo- first order for both reactions in the presence and absence of ethylene glycol

 

7. ACKNOWLEDGEMENT:

The authors pay their sincere gratitude to UGC for grant (MS203/302016/07_08/CRO) Principal, Govt. P.G. College, Jhalawar-Rajasthan (India) for providing necessary research facilities to accomplish this study.

 

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20      Sharma, A.K., Sharma, R., Prasad, D.S.N., Parashar, P., Gupta, A.K.,Ag (I) catalysed autoxidation of S (IV) and its inhibition by isopropyl alcohol in acidic medium,Chem. Sci. Rev.Lett.,2016, 17(5),14-23.

21      Sharma, A.K., Sharma, R., Prasad, D.S.N.,Kinetics and mechanism of uncatalysed and Ag (I) catalysed autoxidation of S(IV) and its inhibition by isoamyl alcohol in acidic aqueous solutions, Int. J. Mod. Sci. Eng. Technol.,2015, 2(12), 31-40.

22      Sharma, A.K., Sharma, R., Prasad, D.S.N., Parashar, P.,The Inhibitive action of Aniline on the autoxidation of sodium sulfite in acidic medium,J. Anal.Phar. Res.,2016, 17(5), 14-23.

23       Sharma, A.K., Sharma, R., Prasad, D.S.N.,The effect of atmospheric aromatic amides on the Ag (I) catalyzed S(IV) autoxidation in aqueous solution,The Experiment,2017, 40(1), 2354-2363.

24      Sharma, A.K., Sharma, R., Prasad, D.S.N., Ag (I) catalyzed oxidation of S(IV) in aqueous solution differing effect of benzoate ions in acidic medium, Curr. Phy. Chem,2017, 7(2),338-347.

25      Wang, L., Ma, Y., Zhang, W., Li, Q., Zhao, Y., Zhang, Z., Macro kinetics of magnesium sulfite oxidation inhibited by ascorbic acid,J. Hazard. Mater.,2013, 258-259, 61-69.

26      Dayal, Y., Gupta, K.S., Role of some organic inhibitors on oxidation of SO₂ in rain water medium, Env. Sc. Pollu. Res., 2014, 21, 3474 -3483.

27      Dayal, Y., Gupta, K.S., The influence of hydroxyl organic compounds on the oxidation of SO₂ by oxygen,Env. Sc. Pollu. Res., 2014, 21, 7808-7817.

28      Meena, V.K., Dhayal, Y., Saxena, D., Rani, A., Chandel, C.P. S. and K. S. Gupta, The influence of diesel—truck exhaust particles on the kinetics of the atmospheric oxidation of dissolved sulfur dioxide by oxygen, Env. Sc. Pollu. Res., 2016, 23, 1-13.

29      A.K. Sharma, S. Acharya, R. Sharma and M. Saxena, Recovery and Reuse of SO₂ from Thermal Power Plant Emission(Chapter), in Book entitled Air Pollution-Monitoring, Modelling, Health and Control, ISBN: 978-953-51-0381-3, DOI: 10.5772/32390. In Tech Open access publisher Croatia (2012).

30      A.K. Sharma, R. Sharma and D.S.N. Prasad, Acid rain chemistry, Catalysis and Inhibition of SO₂ in environment” ISBN 978-3-659-91204-7” LAP lambert Academic Publishing Germany (2017).

31      Gilbert, B. C.; Stell, J. K.; Peet, W. J. and Radford, K. J., Generation and reaction of the chlorine atom in aqueous solution, Journal of Chemical Society Faradey Transactions,1988, 84, 3319-3330.

32      Dogliotti, L. and Hayon, E., Flash photolysis of persulfate ions in aqueous solution. Study of sulfate and ozonide radical anions, Journal of Physical Chemistry, 1967, 71, 2511-2516.

33      Clifton, C. L. and Huie, R. E., Rate constants for hydrogen abstraction reactions of the sulfate radical, SO₄^-, Alcohols, InternationalJournal of Chemical Kinetics,1989, 21, 677-687.

34      Hayon, E.; Treinin, A. and Wilf, J., Electronic spectra, photochemistry and Autoxidation mechanism of the sulfite-bisulfite pyrosulfite systems. The SO₂^-, SO₃^-, SO₄^- and SO₅^-radicals, Journal of American Chemical Society,1972, 94, 47-57.

35      Connick, R. E.; Zhang, Y. X.; Lee, S.; Adamic, R. and Chieng, P., Kinetics and mechanism of oxidation of HSO₃^- by O₂. The uncatalyzed reaction,Inorgnaic chemistry,1995, 34, 4543-4553.

36      Connick, R. E. and Zhang, Y. X., Kinetics and mechanism of oxidation of HSO₃^- by O_2. The manganese(II) catalyzed reaction, Inorganic Chemistry, 1996, 35, 4613-4621.

37      Sharma, A.K., Sharma, R., Prasad, D.S.N., Kinetics of isoamyl alcohol and aniline inhibited uncatalysed and Ag (I) catalysed autoxidation of S (IV) in acidic Medium,Asian J. Research Chem., 2017, 10(3), 251-258.

38      Sharma, A.K. and Prasad, D.S.N., Influence of pH and Organics on Autoxidation of S(IV)Catalyzed by Ag (I),Recent Adv. Petrochem Sci.,2017, 3(1), 1-2.

39      Sharma, A.K., Sharma, R., Prasad, D.S.N., Role of organics in Atmospheric CatalyticAutoxidation of Aqueous Sulphur Dioxide in acidic Medium,Malaysian Journal of Chemistry,(2017), 19(1), 1–12.

40      Begam, S., Husain, F., Prasad, D.S.N., Kinetics of formic acid inhibited uncatalysed and Co₂O₃ catalysed autoxidation of S(IV) in alkaline medium,Der Chemicasinica, 2013, 4(1), 122-13.

 

 

 

 

 

 

 

 

Received on 28.02.2018Modified on 06.04.2018

Accepted on 25.04.2018© AJRC All right reserved