Degradation of dimethyl sulfoxide through fluidized-bed Fenton process

Accepted Manuscript Title: Degradation of dimethyl sulfoxide through fluidized-bed Fenton process Author: Emmanuela M. Matira Teng-Chien Chen Ming-Chun Lu Maria Lourdes P. Dalida PII: DOI: Reference:

S0304-3894(15)00526-9 http://dx.doi.org/doi:10.1016/j.jhazmat.2015.06.069 HAZMAT 16924

To appear in:

Journal of Hazardous Materials

Received date: Revised date: Accepted date:

30-4-2015 17-6-2015 30-6-2015

Please cite this article as: Emmanuela M.Matira, Teng-Chien Chen, MingChun Lu, Maria Lourdes P.Dalida, Degradation of dimethyl sulfoxide through fluidized-bed Fenton process, Journal of Hazardous Materials http://dx.doi.org/10.1016/j.jhazmat.2015.06.069 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

1

Degradation of Dimethyl Sulfoxide through Fluidized-Bed

2

Fenton Process

3 Emmanuela M. Matiraa, Teng-Chien Chenb, Ming-Chun Luc*, Maria Lourdes P. Dalidaa

4 5

a

6

1101 Philippines

7

b

8

Taichung,40724, Taiwan

9

c

10

Department of Chemical Engineering, University of the Philippines Diliman, Quezon City

Department

of

Green

Energy

Development

Center,Feng

Chia

University,

Department of Environmental Resources Management, Chia Nan University of Pharmacy

and Science, Tainan 717 Taiwan

11 12

*corresponding author: Tel: +886-6-2660489, Fax: +886-6-2663411

13

E-mail: [email protected]; [email protected]

14 15 16 17 18 19 20 21

Highlights 

   

Fluidized-bed Fenton resulted in 95.22% DMSO degradation and 34.38% TOC removal. The intermediates formaldehyde and methanesulfinate affected TOC removal. Methanesulfonate was the most difficult to degrade. Methanesulfonate contributed most to residual TOC. Fluidized-bed Fenton degraded DMSO better than conventional Fenton after 5 h.

22 23

Abstract

24

Dimethyl sulfoxide (DMSO), one of the most widely used solvent, was

25

subjected to fluidized-bed Fenton oxidation in this study. Fenton oxidation is

26

considered one of the cheapest advanced oxidation processes due to high availability of 1

1

Fenton’s reagents Fe2+and H2O2, wherein Fe2+ catalyzes hydroxyl radical production

2

from H2O2. Fluidized-bed Fenton process is a modified approach which is also used to

3

address the production of large amount of iron oxide sludge in conventional Fenton

4

process. Parametric study is included in this research using initial conditions of pH 2 to

5

7, 0.5 to 7.25 mM Fe2+, 5 to 87.5 mM H2O2, and 5 to 50 mM DMSO. Fluidized-bed

6

Fenton oxidation of 5 mM DMSO using 68.97 g/L SiO2 carrier at initial conditions of

7

pH 3, 5 mM Fe2+, and 32.5 mM H2O2 resulted to 95.22% DMSO degradation, 34.38%

8

TOC removal and 0.304 mM sulfate/mM DMSO0 production in 2 hours. The study

9

shows that the intermediate product which was most difficult to oxidize and contributed

10

most to the residual TOC was methanesulfonate.

11 12

Keywords: Fluidized-bed Fenton; Dimethyl sulfoxide; Intermediate product

2

1

1. Introduction:

2

In recent years, the thin film transistor liquid crystal display (TFT-LCD) industry

3

increased dramatically in Taiwan. The treatment of its wastewater has become an important

4

concern. TFT-LCD wastewater contains dimethyl sulphoxide (DMSO), monoethanolamine

5

(MEA), and tetra-methyl ammonium hydroxide (TMAH) [1-3]. These organic materials

6

cause the high COD concentration in TFT-LCD wastewater.

7

DMSO is a sulfur-containing organic solvent and has been recently used in many

8

different industries, especially in the TFT-LCD industry, due to its relatively less toxic

9

properties[4]. It is also being used as sulfiding agent for refineries, and as a solvent for the

10

manufacture of pharmaceuticals[5]. Huge production and consumption have been recorded.

11

5000 tonnes of DMSO were produced in Japan per year; while Taiwan imported 900 tonnes

12

from Japan in 2001[6]. United States of America produced and imported 10 million to 50

13

million pounds in 2005[7]. DMSO concentration in TFT-LCD wastewater effluent was

14

found to be 500-800 mg L-1 and lower than 1000 mg L-1 of biodegradable non-DMSO

15

organic compounds[8, 9].

16

In general, DMSO has low toxicity. However, studies have shown that extensive

17

use or exposure to DMSO has negative effect to animals and humans which can be easily

18

absorbed through dermal and oral routes and absorption of other chemicals is enhanced via

19

these routes. In humans, it is an irritant of the eyes, skin, and respiratory system. While in

20

animals, the effects are renal and hepatic lesions, corneal injury, birth defects, and repeated

21

dermal application results in irritation and rashes[10].

22

Moreover, the acute hazard to fish and aquatic invertebrates is based on measured

23

toxicity values for DMSO of 32,300 mg/L and 24,600 mg/L, respectively. Hazard to

24

aquatic plants is based on estimated toxicity values of 400 mg/L[7]. Toxicity level based on

25

LD50 for rats is 18000 mg/kg [11]. U.S. EPA allows discharge of maximum of 0.05 mg/L

26

DMSO. In industries, DMSO is being recycled in original process when its concentration is 3

1

at least 1000 mg/L. While the concentration between 10 to 1000 mg/L is from washing and

2

rinsing processes, DMSO solution should be treated and discharged[6]. There are different

3

methods for treating DMSO-containing wastewater including physiochemical and

4

biological processes. UV/H2O2[12, 13] and ozone-based[13] processes have been evaluated

5

for treating DMSO-containing wastewater but the cost of these physiochemical methods is

6

a great concern when applied to full-scale processes.

7

Biological treatment technologies are not considered effective methods for this

8

target pollutant. Aerobic biological treatment does not decompose DMSO [4] while

9

anaerobic biodegradation leads to production of dimethyl sulfide (DMS), methane thiol

10

(MT) and hydrogen sulfide which are malodorous. DMS and MT also contribute to global

11

warming and acid precipitation[6].

12

With the mentioned limitations of biological treatment methods, advanced oxidation

13

processes (AOPs) are being studied for treatment of DMSO solutions because AOPs are

14

generally not selective in attacking organic pollutant. One of the cheapest kinds of AOPs is

15

Fenton reaction. However, large volume of iron oxide sludge is produced in Fenton process

16

and in subsequent neutralization process[14]. One of the improvements to manage this

17

drawback is fluidized-bed Fenton oxidation which crystallizes iron oxides in the carrier in

18

the fluidized-bed reactor[15], thus, minimizing the production of ferric hydroxide sludge.

19

[16].

20

Several reactions occurring in fluidized-bed Fenton process are: (1) homogenous

21

chemical oxidation (H2O2/Fe2+), (2) heterogeneous chemical oxidation (H2O2/iron oxide),

22

(3) fluidized-bed crystallization, and (4) reductive dissolution of iron oxides [17]. Figure 1

23

shows the mechanisms in fluidized-bed Fenton. Similar reactions that occur both in

24

fluidized-bed and conventional Fenton process, which are homogenous reactions, are: (a)

25

homogenous •OH production from Fe2+ and H2 O2, (b) reaction of organic matter and 4

1

hydroxyl radical, (c) conversion of Fe2+ to Fe3+, and (d) slower conversion of Fe3+ back to

2

Fe2+. Additional reactions in fluidized-bed Fenton process, which are heterogenous

3

reactions, brought about by the presence of carrier are: (e) crystallization of Fe3+ in iron

4

oxide forms initiated by the carrier, (f) production of hydroxyl radical from H2O2 catalyzed

5

by iron oxides, and (g) redissolution of iron oxide to Fe2+ [18].

6

In this study, the degradation of synthetic DMSO wastewater using a fluidized-bed

7

Fenton process was investigated. Included in the study were parametric study, kinetic

8

study, investigation on intermediates, and comparison of performances of fluidized-bed

9

Fenton with conventional Fenton.

10

2. Materials and Methods

11

2.1 Materials

12

Experiments for parametric and kinetic studies were conducted for 2 h. All

13

chemicals were purchased from Merck and Panreac companies. Solutions were prepared

14

using de-ionized water from a Millipore system with resistivity of 18. 2 MΩ cm.

15

Figure 2 shows the batch type reactor. The Fluidized-bed Fenton reactor has

16

dimensions of 5.2 cm diameter and 140 cm height, attached with recirculation pump, and

17

contained perforated plate. 4 mm glass beads were placed below the 2 mm glass beads at

18

the bottom, and pH probe and thermometer were installed at the top. Sampling point was

19

near the recirculation location. The reactor was loaded with 100g of 0.42 to 0.50 mm sand

20

as carriers (0.42 to 0.50 mm sand were obtained using screen with Mesh 35 and 40).

21

2.2 Experimental Methods

22

1.45 mL of 5mM DMSO solution was poured into the reactor containing 4 mm and

23

2 mm glass beads. SiO2 carrier of 0.42 to 0.5 mm diameter was added, followed by the

24

desired amount of FeSO4 7H2O. The recirculation pump was adjusted such that the bed

25

height of the carrier was maintained at 30 cm which was also equivalent to 360 cm/min 5

1

flow and 5.25 cycles per minute. The pH of the solution was then adjusted by adding 0.1N

2

NaOH or 1N H2SO4 into the reactor. Addition of H2O2 started the Fenton reaction process.

3

Samplings were done before the start of the oxidation process, and at specified intervals.

4

2.3 Analytical Methods

5

Prior to analyses of actual samples from Fenton and FB-Fenton processes, calibration

6

curves with r-squared value of at least 0.995 were obtained for each analytical equipment

7

(except for pH measurement) to ensure accurate measurements. Fe2+, H2O2, DMSO, total

8

organic carbon and total iron concentrations were analyzed by UV-vis spectrophotometer,

9

TOC and AA. IC and HPLC were used for the intermediate products analysis for formate,

10

sulphate, and methanesulfonate concentrations.

11 12

3. Result and Discussion:

13

3.1 Controlled Experiments for Fluidized-bed Fenton Process

14

Controlled experiments for the FB-Fenton process were performed to determine the

15

effect of different conditions, such as presence or absence of Fe2+ and H2O2 combined with

16

pH with or without adjustment and due to the SiO2 carrier alone, on the degradation of

17

DMSO. Figure 3 shows the result of the controlled experiments and Table 1 summarizes

18

the removal due to each component.

19

There was 2.89 % DMSO removal due to the presence of the SiO2 carrier of the

20

fluidized-bed reactor. This removal could be attributed to adsorption or complexation of

21

DMSO to the sand for 2 h. However, the removal is considered negligible due to the length

22

of time spent for a very small amount of degraded DMSO, as compared to the rate during

23

advanced oxidation processes.

24

The adjustment of pH to 3 by adding H2SO4 into the reactor resulted in 6.24 %

25

DMSO degradation, thus, removal due to H2SO4 was 3.35 % (2.89% was due to SiO2). The

26

removal obtained when Fe2+ was added to the reactor at pH 3 was 7.79 %, thus, removal 6

1

due to Fe2+ alone was 1.55 %. This is a small decrease and could be ignored as DMSO

2

cannot form complexes with iron or other metal ions according to Tai, et al[19].

3

The removal of DMSO, after adding H2O2 without pH adjustment, was 10.13, thus,

4

7.24 % removal was due to H2O2. As H2O2 is an oxidant, it is expected that its removal of

5

DMSO is higher.

6

The above results show that the effect of pH adjustment, or Fe2+ alone can be

7

considered negligible. For the succeeding experiments, removal of DMSO and TOC were

8

attributed to the fluidized-bed process.

9 10

3.1 Effect of Initial pH

11

Fenton oxidation is a pH dependent process because the solution pH is a significant

12

parameter in the mechanism of HO• generation in the Fenton reaction [20-24]. Its effect on

13

real DMSO wastewater treatment in terms of DMSO removal efficiency by fluidized-bed

14

Fenton reagent was investigated. Generally, Fenton process is conducted in acidic medium.

15

In the previous studies, the increase in pH during the Fenton process leads to coagulation

16

whereby pollutants are removed by complexation of reactions due to the conversion of Fe2+

17

and Fe3+ to Fe(OH)n type structures[25]. Ting et al.[26] reported that 2,6-dimethylaniline

18

concentration decreased from 36 % to 25 % in 2 h when pH was increased from 1.5 to 2.0.

19

The complete removal of 2,6-dimethylaniline was achieved after 140 min at pH 2.

20

Different pH values between 2 to 7 were evaluated. DMSO degradation in varying

21

initial pH are shown in Figure 4. The result showed that the optimal efficiency was reached

22

at 95.22 % DMSO degradation when the initial pH value was 3 with 2 h reaction time.

23 24

Compared to pH 3, initial pH 2 was an inferior condition as it only led to 82.02 %

25

DMSO degradation. The lower degradation efficiency could be due to Fe2+:H2O2 complex

26

formation with low pH value. Reaction of H2O2 and Fe2+:H2O2 complex produces HO∙at a 7

1

very slow rate [27, 28]. Indeed, these formations of complexes reduce the amount of free

2

Fe2+, thus generation of hydroxyl radical as well as degradation of DMSO decreased.

3

At initial pH value of 4 and 7, oxidation efficiency was decreased and the DMSO

4

degradation was only 80.78 % and 39.58 %, respectively. This could mean that the Fe2+:

5

OH- complex [Fe (H2O)4(OH)2] was formed at higher pH value. This complex used up Fe2+

6

for the complex, hence there was limited Fe2+ for HO∙ production from H2O2[27, 28]. In

7

this study, pH 3 was the optimal value. This result was also consistent with previous

8

results[29, 30].

9

3.2 Effect of Initial Fe2+ Concentration

10

Suitable ferrous ion concentration is an important prerequisite in the electro-Fenton

11

process [31]. Generally, the efficiency of Fenton process increased with Fe2+ concentration

12

because the concentration of hydroxyl radicals, which is the main oxidizing agent in the

13

Fenton process, increases with the increase in Fe2+ concentration. According to Wang et al.

14

[32], the presence of Fe2+ significantly improved the COD removal efficiency. The COD

15

removal percentage markedly increased from19.8 % to 43.1 % by externally adding a Fe2+

16

concentration of 0.33 mM. The optimal ferrous amount was 2mM in the 75.2% COD

17

removal[32]. Four different ferrous amounts were applied.

18

From Figure 5, it can be seen that when the initial Fe2+ was increased, the DMSO

19

and H2O2 degradation efficiency also increased dramatically. Scavenging of hydroxyl

20

radical, which is indicated by negative effect of Fe2+ concentration, was not observed in all

21

of the Fe2+ dosage when based on DMSO degradation after 2 h. However, based on initial

22

rates, the scavenging of hydroxyl radical was present when initial Fe2+ was 7.25 mM. This

23

observation implied that a high Fe2+ concentration does not increase the degradation of

24

DMSO in the Fenton oxidation process due to the Fe2+ ion competing against reacted

25

molecules for HO•, as expressed in Eq. (4). 8

1 2

Since the application of 5 mM Fe2+ led to appreciable DMSO degradation in 2 h,

3

this dosage was considered instead of 7.25 mM in succeeding investigation. This is also for

4

lower cost in case the study will be used for future industrial application.

5

3.3 Effect of Initial H2O2 Concentration

6

Increasing the amount of H2O2 improves the Fenton process performance, the excess

7

amount may cause scavenging of hydroxyl radical as shown in Eq (1) to (2). Eq (3) is a

8

recombination of hydroxyl radical rather than scavenging. Fe2+ loading has the same effect

9

as it also enhances the degradation efficiency but scavenge hydroxyl radical when in excess

10

amount, as shown in Eq. (4) [26].

11 12

H2O2 + HO  H2O + HO2

13

HO2 + HO  H2O + O2

k = 1.0 x 1010 M-1 s- (2)

14

HO + HO  H2O2

k = 4.2 x 109 M-1 s-

15 16 17

k = 2.7 x 107 M-1 s-

(1)

(3) Fe2+ + HO  Fe3+ + OH

-

(4)

18 19

According to Ting et al. [26], the initial concentration of H2O2 played an important

20

role in the Fenton process. Removal of COD increases with increase in H2O2 concentration.

21

The increase in the removal efficiency was due to the increase in HO• radical concentration

22

as a result of the addition of H2O2 [26]. Zhang et al. [33] stated that efficiency of hydrogen

23

peroxide for removing organic materials in the leachate decreased with the increase of

24

Fenton's reagent dosage. At a high concentration of H2O2, the decrease in removal

9

1

efficiency was due to the hydroxyl radical scavenging effect of H2O2 and the recombination

2

of the hydroxyl radical [20].

3

TOC and COD removal can be determined from the amount of oxygen in the

4

supplied H2O2. The degradation was not purely caused by Fenton process (using hydroxyl

5

radical) if hydrogen peroxide efficiency (EH) is greater than 100% [30]. The low EH

6

efficiency indicated inefficient scavenging process [15]. Equation 5 is the theoretical model

7

for calculation of EH efficiency with respect to DMSO removal. The value of 0.47 is

8

indicated of disproportion in H2O2 by catalyst which is given 0.5 mole O2 in each mole

9

H2O2 concentration [34]. Table 2 shows the hydrogen peroxide efficiency as increasing the

10

initial concentration of H2O2 on the concentration of 5 mM DMSO.

11 12

Figure 6 shows that the hydrogen peroxide efficiency decreases when there is an

13

increase in H2O2 dosage, even if there is improved DMSO degradation when H2O2 amount

14

increased to 60 mM.

15

Furthermore, EH values greater than 100 % were obtained for the 5 mM and 32.5 mM

16

H2O2 which could be attributed to the action of Fe3+ and H2O2 generating hydroxyphenol

17

radicals. This is a weaker oxidizing agent compared to hydroxyl radical [35].

18

EH 

decrease in concentrat ion of DMSO (mg/L)  100% 0.47 x decrease in concentrat ion of H 2 O 2 (mg/L)

(5)

19

In Figure 6, appreciable DMSO removal were obtained when dosages of H2O2 were

20

32.5 mM and 60 mM. The removal efficiency of DMSO degradation was increased only by

21

2 % when the experiment was conducted at higher H2O2 concentration. In this experiment,

22

the scavenging effect of the excess H2O2 , as described by [17], was evident when at least

23

60 mM was the initial H2O2 concentration. Thus, the H2O2 initial concentration of 32.5 mM

24

was considered and used in further investigation. 10

1 2

3.4 Intermediate Analysis

3

Degradation pathway of DMSO using UV/H2O2 process, studied by Lee et al. [12],

4

is shown in Figure 7. Degradation pathway using ozonation process is similar, as observed

5

by Wu et al. [13]. There are two groups of intermediates in the degradation of DMSO: the

6

sulfur-containing compounds and the non-sulfur containing compounds. The two primary

7

intermediates were formaldehyde (HCHO) and methanesulfinate (CH3SO2-). Formaldehyde

8

is further degradable to formate (HCOO-) and then to carbon dioxide. Meanwhile,

9

methanesulfinate is degradable to formaldehyde and to mehanesulfonate (CH3SO3-).

10

Methanesulfonate is then degradable to sulfate [12]. The involved reactions are shown in

11

Table 3. Methanesulfonate, however, was the most resistant intermediate to degrade. This

12

was determined in the studies of Wu et al. and Lee et al. [12, 20]. The degradation rate

13

constants in Eqs. (12) and (13) indicated that methanesulfonate was the most difficult to

14

degrade.

15

The degradation mechanism and pathway by Lee et al. [12] were used as the basis

16

for the characterization of the intermediates for DMSO degradation via fluidized-bed

17

Fenton reaction. The intermediates are methanesulfinate, methanesulfonate, formaldehyde,

18

formate, and sulfate. Methanesulfinate is considered very reactive with oxidation such that

19

it could be readily degraded to methanesulfonate or formaldehyde [12, 13, 20].

20

Figure 8 shows that there was 0.35 mM sulfate produced for 1 mM DMSO

21

in 5 h. This indicated that 0.35 mM methanesulfonate was converted to sulfate as DMSO

22

degradation pathway indicated that only methanesulfonate was the last intermediate before

23

the final product sulfate. Figure 8 also shows that the methanesulfonate was the most

24

persistent among organic intermediates. This result agrees with previous studies that

25

methanesulfonic acid is the product of advanced oxidation of DMSO. Furthermore, having 11

1

methanesulfonate as the only persistent organic compound would allow biological

2

treatment for downstream processing, since there would be no harmful biodegradation by-

3

products [36]. As observed, DMSO could not be 100 % removed in 5 h. This could be due

4

to the stronger affinity of hydroxyl radical to react with intermediates than with DMSO,

5

such that the generated radical was being used up to degrade first the intermediates that

6

included methanesulfonate.

7 8

Calculated normalized TOC was obtained by summation of all the concentrations

9

of the DMSO and the organic intermediates and products in the corresponding time-

10

profiles. Although the concentration of methanesulfinate was not measured, the normalized

11

TOC and calculated TOC time-profiles in Figure 8 show small difference with each other.

12

This confirmed that methanesulfinate was very unstable, such that it was easy to degrade

13

and it is not accumulated.

14

3.5 Comparison between Conventional Fenton and Fluidized-bed Fenton

15

Processes on DMSO Degradation

16

The following initial conditions of 5 mM DMSO, pH 3, 5 mM Fe2+, 32.5 mM H2O2

17

were used for the DMSO degradation using conventional Fenton to compare its

18

performance with the FB-Fenton process for 5 h. Comparison was based on the time-profile

19

of DMSO removal, TOC removal, remaining H2O2, remaining Fe2+, remaining total Fe, and

20

pH. The results are shown in Figure 9.

21 22

During initial reaction time, the governing mechanism is Fe2+/H2O2. This

23

mechanism is one of two parts of the homogenous oxidation. The other one, which causes

24

much slower oxidation, is another Fe3+/H2O2 mechanism. The homogenous oxidation is the

25

only one present in conventional process; while heterogeneous oxidation, fluidized-bed 12

1

crystallization of Fe(OH)3, and reductive dissolution of iron oxide also occurs in fluidized-

2

bed Fenton process [34]. The heterogeneous oxidation was expected to contribute to

3

contaminant degradation.

4

The resulting conditions in the first 3 min were apparently the same for both

5

conventional and fluidized-bed Fenton processes. This verifies that the homogenous

6

oxidation of Fe2+/H2O2 was the only occurring mechanism during that initial stage.

7

After 3 min, the predominant mechanism was homogenous and heterogeneous

8

Fe3+/H2O2. This is based on the negligible residual Fe2+ after 3 min. Mechanism for the re-

9

dissolution of iron oxide was not visible as there was no time where Fe2+ was detected. This

10

could be because re-dissolution only occurs when peroxide is completely consumed [34].

11

After 80 min, fluidized-bed crystallization became apparent as there was lower

12

residual total iron in the solution. Removal of 35 % and 22 % total iron after 3 h was

13

observed in fluidized-bed Fenton and conventional Fenton, respectively. The 13 %

14

difference was due to the crystallization of Fe(OH)3 assisted by the fluidized bed.

15

Heterogonous Fe3+/H2O2 was evident based on DMSO degradation and TOC

16

degradation. Removal of 42.25 % and 34.0 % TOC was observed in fluidized-bed Fenton

17

and conventional Fenton, respectively. The 8.25 % difference was due to the heterogeneous

18

reaction, while 34.0 % TOC degradation was due to homogenous Fe3+/H2O2.

19

As also shown in Figure 10, the performance of fluidized-bed Fenton process was

20

better than that of conventional Fenton process. After 5 h, the fluidized bed Fenton was

21

able to degrade 96.07 % DMSO and 42.25 % TOC, while conventional process degraded

22

93.67 % DMSO and 34.0 % TOC. Higher H2O2 was consumed in FB-Fenton since there

23

were more intermediates that were produced that used up more H2O2. The pH decrease in

24

both processes was due to the organic acids generated upon degradation of DMSO. These

25

organic acids are methanesulfinic acid, methanesulfonic acid, and formic acid [12]. The 13

1

lower level of final pH in fluidized-bed was due to higher efficiency of degradation that

2

resulted to higher acid production. Both processes encountered fast transformation of Fe2+

3

to Fe3+.

4 5

Moreover, mineralization is the ultimate goal of oxidation; and since sulfate is the

6

sulfur-containing end product for the oxidation, sulfate concentration is one of the basis of

7

performances, as well as TOC. Table 4 shows these performance values, along with other

8

indicators, for the corresponding runs in comparing degradations in conventional and FB-

9

Fenton. Based on the values, it can be stated that fluidized-bed Fenton had better efficiency

10

when compared to conventional Fenton.

11 12

4. Conclusion

13

Fluidized-bed Fenton process is an effective method in degradation of dimethyl

14

sulfoxide in synthetic wastewater. Parametric study shows that increasing the dose of Fe2+

15

favors the DMSO degradation. Favorable DMSO degradation was observed in increasing

16

the H2O2 to a certain dose only due to scavenging reactions. Furthermore, fluidized-bed

17

Fenton oxidation of 5 mM DMSO using 68.97 g/L SiO2 worked at initial conditions of pH

18

3, 5 mM Fe2+, and 32.5 mM H2O2. For initial conditions of pH 3, [Fe2+] of 0.5-5 mM,

19

[H2O2] of 5-60 mM and [DMSO] of 5-50 mM, fluidized-bed Fenton process was better

20

than conventional Fenton reaction in terms of DMSO degradation, and residual total iron.

21

The intermediates of DMSO degradation were formaldehyde, methanesulfinate, and

22

methanesulfonate. The intermediate that was the most difficult to degrade was

23

methanesulfonate, and this contributed most on the residual TOC. This, however, is

24

manageable in biological treatment. Fluidized-bed Fenton process on DMSO degradation

25

was comparable with the performance of conventional Fenton process. After 5 h, the

14

1

fluidized bed Fenton was able to degrade 96.07 % DMSO and 42.25 % TOC, while

2

conventional Fenton process degraded 93.67 % DMSO and 34.0 % TOC.

3

Acknowledgements

4 5 6

This work was financially supported by the Ministry of Science and Technology, Taiwan (Grant: NSC 96-2628-E-041-002-MY3)

7 8 9 10 11

Reference:

12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Methyl Ammonium Hydroxide (TMAH) Containing Wastewater, Semiconductor Manufacturing, IEEE Transactions on, 21 (2008) 486-491. [3] C.-N. Lei, L.-M. Whang, P.-C. Chen, Biological treatment of thin-film transistor liquid crystal display (TFT-LCD) wastewater using aerobic and anoxic/oxic sequencing batch reactors, Chemosphere 81 (2010) 57-64. [4] C.-H. Wu, Adsorption of reactive dye onto carbon nanotubes: equilibrium, kinetics and thermodynamics, J. Hazard. Mater. 144 (2007) 93-100. [5] G. Chemical, DMSO Reaction Solvent Dimethyl Sulfoxide. Technical Bulletin Reaction Solvent Dimethyl Sulfoxide in, 2013. [6] S.-C.J. Hwang, J.-Y. Wu, Y.-H. Lin, I.-C. Wen, K.-Y. Hou, S.-Y. He, Optimal dimethyl sulfoxide biodegradation using activated sludge from a chemical plant, Process Biochem. 42 (2007) 1398-1405. [7] U.S.E.P. Agency, Hazard Characterization Document. Screening-Level Hazard Characterization. Dimethyl Sulfoxide (CASRN 67-685), in: U.S.E.P. Agency (Ed.), 2009. [8] T. Murakami-Nitta, K. Kirimura, K. Kino, Degradation of dimethyl sulfoxide by the immobilized cells of Hyphomicrobium denitrificans WU-K217, Biochem. Eng. J. 15 (2003) 199-204. [9] S.-Y. He, Y.-H. Lin, K.-Y. Hou, S.-C.J. Hwang, Degradation of dimethyl-sulfoxidecontaining wastewater using airlift bioreactor by polyvinyl-alcohol-immobilized cell beads, Bioresource Technol. 102 (2011) 5609-5616. [10] S.E. Gad, D.W. Sullivan Jr, Dimethyl Sulfoxide (DMSO), in: P. Wexler (Ed.) Encyclopedia of Toxicology (Third Edition), Academic Press, Oxford, 2014, pp. 166-168. [11] G. Chemical, DMSO Reaction Solvent Dimethyl Sulfoxide.Technical Bulletin Reaction Solvent Dimethyl Sulfoxide (DMSO). in, 2013.

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[12] Y. Lee, C. Lee, J. Yoon, Kinetics and mechanisms of DMSO (dimethylsulfoxide) degradation by UV/H 2 O 2 process, Water Res. 38 (2004) 2579-2588. [13] J.J. Wu, M. Muruganandham, S. Chen, Degradation of DMSO by ozone-based advanced oxidation processes, J. Hazard. Mater. 149 (2007) 218-225. [14] J. Anotai, M.-C. Lu, P. Chewpreecha, Kinetics of aniline degradation by Fenton and electro-Fenton processes, Water Res. 40 (2006) 1841-1847. [15] S. Chou, C.-C. Liao, S.-H. Perng, S.-H. Chang, Factors influencing the preparation of supported iron oxide in fluidized-bed crystallization, Chemosphere 54 (2004) 859-866. [16] N. Masomboon, C. Ratanatamskul, M.-C. Lu, Chemical oxidation of 2, 6dimethylaniline in the Fenton process, Environ. Sci. Technol. 43 (2009) 8629-8634. [17] J. Anotai, P. Sakulkittimasak, N. Boonrattanakij, M.-C. Lu, Kinetics of nitrobenzene oxidation and iron crystallization in fluidized-bed Fenton process, J. Hazard. Mater. 165 (2009) 874-880. [18] C. Ratanatamskul, S. Chintitanun, N. Masomboon, M.-C. Lu, Inhibitory effect of

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inorganic ions on nitrobenzene oxidation by fluidized-bed Fenton process, J. Mol. Catal. AChem. 331 (2010) 101-105. [19] C. Tai, J.-F. Peng, J.-F. Liu, G.-B. Jiang, H. Zou, Determination of hydroxyl radicals in advanced oxidation processes with dimethyl sulfoxide trapping and liquid chromatography, Anal. Chim. Acta 527 (2004) 73-80. [20] M. Muruganandham, M. Swaminathan, Decolourisation of Reactive Orange 4 by Fenton and photo-Fenton oxidation technology, Dyes Pigments 63 (2004) 315-321. [21] J. Kochany, A. Lugowski, Application of Fenton's reagent and activated carbon for removal of nitrification inhibitors, Environ. Technol. 19 (1998) 425-429. [22] W.Z. Tang, S. Tassos, Oxidation kinetics and mechanisms of trihalomethanes by Fenton's reagent, Water Res. 31 (1997) 1117-1125. [23] W.Z. Tang, C. Huang, Effect of chlorine content of chlorinated phenols on their oxidation kinetics by Fenton's reagent, Chemosphere 33 (1996) 1621-1635. [24] W. Tang, C. Huang, 2, 4-dichlorophenol oxidation kinetics by Fenton's reagent, Environ. Technol. 17 (1996) 1371-1378. [25] M.Y.A. Mollah, R. Schennach, J.R. Parga, D.L. Cocke, Electrocoagulation (EC)— science and applications, J. Hazard. Mater. 84 (2001) 29-41. [26] W.-P. Ting, M.-C. Lu, Y.-H. Huang, Kinetics of 2, 6-dimethylaniline degradation by electro-Fenton process, J. Hazard. Mater. 161 (2009) 1484-1490. [27] S.H. Lin, C.C. Lo, Fenton process for treatment of desizing wastewater, Water Res. 31 (1997) 2050-2056. [28] R.J. Bigda, Consider Fentons chemistry for wastewater treatment, Chem. Eng. Prog. 91 (1995).

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[29] J.-H. Sun, S.-P. Sun, M.-H. Fan, H.-Q. Guo, L.-P. Qiao, R.-X. Sun, A kinetic study on the degradation of p-nitroaniline by Fenton oxidation process, J. Hazard. Mater. 148 (2007) 172-177. [30] I. Muangthai, C. Ratanatamsakul, M.-C. Lu, Removal of 2, 4-dichlorophenol by fluidized-bed Fenton process, Sustain. Environ. Res. (2010). [31] M. Zhou, Q. Yu, L. Lei, G. Barton, Electro-Fenton method for the removal of methyl red in an efficient electrochemical system, Sep. Purif. Technol. 57 (2007) 380-387. [32] C.-T. Wang, W.-L. Chou, M.-H. Chung, Y.-M. Kuo, COD removal from real dyeing wastewater by electro-Fenton technology using an activated carbon fiber cathode, Desalination 253 (2010) 129-134. [33] H. Zhang, C. Fei, D. Zhang, F. Tang, Degradation of 4-nitrophenol in aqueous medium by electro-Fenton method, J. Hazard. Mater. 145 (2007) 227-232. [34] E. Brillas, I. Sirés, M.A. Oturan, Electro-Fenton process and related electrochemical technologies based on Fenton’s reaction chemistry, Chem. Rev. 109 (2009) 6570-6631.

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[35] T.L.P. Dantas, H.J. José, R. Moreira, Fenton and photo-Fenton oxidation of tannery wastewater, Acta Sci. Technol. 25 (2003) 91-95. [36] T. Koito, M. Tekawa, A. Toyoda, A novel treatment technique for DMSO wastewater, Semiconductor Manufacturing, IEEE Transactions on, 11 (1998) 3-8. [37] G.V. Buxton, C.L. Greenstock, W.P. Helman, A.B. Ross, Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

(⋅OH/⋅O− in Aqueous Solution, J. Phys. Chem. Ref. Data 17 (1988) 513-886. [38] R. Flyunt, O. Makogon, M.N. Schuchmann, K.-D. Asmus, C. von Sonntag, OHRadical-induced oxidation of methanesulfinic acid. The reactions of the methanesulfonyl radical in the absence and presence of dioxygen, J. Chem. Soc. Perk. T 2 (2001) 787-792. [39] J.V. McArdle, M.R. Hoffmann, Kinetics and mechanism of the oxidation of aquated sulfur dioxide by hydrogen peroxide at low pH, J. Phys. Chem. 87 (1983) 5425-5429.

Table Captions Table 1. DMSO removal due to each component.

17

1 2 3

Table 2. Hydrogen peroxide efficiency as increasing the initial concentration of H2O2 on the concentration of 5 mM DMSO

4

Table 3. Reactions in DMSO degradation during advanced oxidation process[12]

5 6

Table 4. Values of performance indicators of conventional and fluidized-bed Fenton

7

degradation of DMSO for 2 hours when initial conditions are pH 3, 5 mM DMSO,

8

5 mM Fe2+, 32.5 mM H2O2

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Table 1 DMSO % Removal 2.89

Due to SiO2 carrier

18

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

6.24

H2SO4 + SiO2

3.35

H2SO4

7.79

H2SO4 + SiO2 + Fe2+

1.55

Fe2+

10.13

SiO2 carrier + H2O2

7.24

H2O2

Table 2 Initial concentration of H2O2 5 mM 32.5 mM 60 mM

EH with respect to DMSO 318.43 % 137.07 % 81.96 % 19

87.5 mM

57.68 %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Table 3

33 34 Reaction

k (M-1 s-1)

Equation No.

Ref

DMSO decomposition by •OH 20

6.6 x 109

(6)

[37]

CH3SO-2   OH  CH3SO2  OH

5.3 x 109

(7)

[38]

CH3SO2  O2  CH3S(O)2 O2 

8.0 x 108

(8)

[38]

CH3S(O)2 O2  CH3SO2  CH3S(O)2 O  CH3SO3

6.2 x 108

(9)

[38]

CH3S(O)2 O   CH3SO-2  CH3SO3-  CH3SO2 

1.0 x 108

(10)

[12]

CH3S(O)2 O   CH3SO-2 1.5O2  H2O

3.0 x 107

(11)

[12]

0.8 x 107

(12)

[12]

 1.0 x 104

(13)

[39]

HCHO OH O2 HCOO-  HO2  H

1.0 x 109

(14)

[12]

HCOO-  OH O2  H HO2  H2O  CO2

3.0 x 109

(15)

[37]

(CH3 )2 SO   OH  1.5 O2  HCHO  CH3SO-2  HO2  H Chain-oxidation of methanesulfinate

CH3SO-3  HCHO HSO-3  HO2  H Oxidation of methanesulfonate

CH3SO3-  OH  0.5O2  H  HCHO HSO-3  H2O HSO3-  H2O2  HSO-4  H2O Oxidation of folmaldehyde and formate

1 2 3 4 5 6 7

Table 4

8

sulfate DMSO0

EHDMSO

EHTOC

%

%

25.12

0.099

142.21

11.66

34.38

0.304

137.07

15.09

DMSO removal %

TOC removal %

Fenton

93.12

FB- Fenton

95.22

9 10 11 12 13 14 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Figures Captions Figure 1. Reactions involved in fluidized-bed Fenton process

Figure 1

22

1 2 3 4

Figure 1. Reactions involved in fluidized-bed Fenton process

5 6 7 8 9 10

23

1 2 3

Figure 2. Fluidized-bed Fenton reactor

4 5 6 7 8 9 10

24

Remaining DMSO (C/C0)

1.0

0.8 2+

without pH adjustment, 0 Fe , 0 H2O2 2+ pH adjusted to 3, 0 Fe , 0 H2O2

0.6

pH adjusted to 3,

2+

5 mM Fe , 0 H2O2 2+

without pH adjustment, 0 Fe , 32.5 mM H2O2 0.4

pH adjusted to 3,

2+

5 mM Fe , 32.5 mM H2O2

0.2

0.0 0

20

40

60

80

100

120

Time (minutes)

1 2 3 4 5

Figure 3. Controlled experiments for FB-Fenton Process

6 7 8 9 10 11 12 13 14 15 16 17 18 25

pH = 2 pH = 3 pH = 4 pH = 7

Remaining DMSO (C/Co)

1.0

0.8

0.6

0.4

0.2

0.0 0

20

40

60

80

100

120

Time (minutes)

1 2 3 4

Figure 4. Effect of initial pH: Remaining DMSO when initial conditions were

5

mM Fe2+, 32.5 mM H2O2, and 5 mM DMSO

5 6 7 8 9 10 11 12 13 14 15 16 17 26

1

Remaining DMSO (C/Co)

1.0

0.8 +2

0.5 mM Fe 2.75 mM 5.0 mM 7.25 mM

0.6

0.4

0.2

0.0 0

20

40

60

80

100

120

Time (minutes)

2 3 4 5

Figure 5. Effect of initial Fe2+ concentration: DMSO Remaining when initial conditions were pH 3, 32.5 mM H2O2, and 5 mM DMSO

6 7 8 9 10 11 12 13 14 15 16 17 27

1 2

5.00 mM H2O2

Remaining DMSO (C/Co)

1.0

32.5 mM 60.00 mM 87.50 mM

0.8

0.6

0.4

0.2

0.0 0

20

40

60

80

100

120

Time (minutes)

3 4

Figure 6. Effect of initial H2O2 concentration: DMSO Remaining when initial

5

conditions were pH 3, 5 mM Fe2+, and 5 mM DMSO

6 7 8 9 10 11 12 13

28

1 2 3

Figure 7. Degradation pathway of DMSO during advanced oxidation process[12]

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 29

DMSO Methanesulfonate Sulfate Folmaldehyde Formate

Concentration (C/Cinitial of DMSO)

1.0

0.8

0.6

0.4

0.2

0.0 0

60

120

180

240

300

Time (minutes)

1 2 3 4 5 6

Figure 8. Intermediates and products of DMSO degradation time profile when initial conditions are pH 3, 5 mM DMSO, 5 mM Fe2+, and 32.5 mM H2O2

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 30

1 2

Calculcated TOC Measured TOC

Remaining TOC (C/Co)

1.0

0.8

0.6

0.4

0.2

0.0 0

60

120

180

240

300

Time (minutes)

3 4 5 6 7

Figure 9. Measured and Calculated TOC time profile during DMSO degradation when initial conditions are pH 3, 5 mM DMSO, 5 mM Fe2+, and 32.5 mM H2O2

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 31

1 2 3 4 5 Conventional Fenton process Fluidized-bed Fenton process

1.0

0.8

0.8

Remaining TOC (C/C o)

Remaining DMSO (C/Co)

1.0

0.6

0.4

0.6

0.4

0.2

0.2

0.0

0.0 0

60

120

180

240

0

300

20

40

Time (minutes)

(a)

60

80

100

120

Time (minutes)

(b) 3.5

1.0

0.6

pH

Remaining H2O2 (C/Co)

3.0

0.8

2.5

0.4 2.0

0.2

1.5

0.0 0

60

120

180

240

0

300

60

Remaining total Iron (C/Co)

0.8

2+

240

300

240

300

1.0

1.0

Remaining Fe (C/Co)

180

(d)

(c)

0.6

0.4

0.2

0.8

0.6

0.4

0.2

0.0

0.0 0

60

120

180

240

0

300

60

120

180

Time (minutes)

Time (minutes)

(e)

120

Time (minutes)

Time (minutes)

(f)

6

32

1

Figure 10. Comparison of performances of conventional and fluidized-bed Fenton

2

degradation of DMSO when initial conditions were pH 3, 5 mM Fe2+, 32.5 mM

3

H2O, and 5 mM DMSO

4

33