Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2 ...Sulfamerazine C 11 H 12 N 4 O 2 S NH2 CH3 N N NH S O O 264.30 — 7.00 Sulfamethoxazole C 10 H 11 N 3 O 3 S NH2 H3C NH S

Research ArticleOxidation of Sulfonamides inAqueous Solution by UV-TiO2-Fe(VI)

Yan Ma12 Kejia Zhang34 Cong Li34 Tuqiao Zhang34 and Naiyun Gao1

1State Key Laboratory of Pollution Control and Resource Reuse Tongji University Shanghai 200092 China2Shanghai Urban Water Resources Development and Utilization National Engineering Center Co Ltd Shanghai 200082 China3College of Civil Engineering and Architecture Zhejiang University Hangzhou 310058 China4Key Laboratory of Drinking Water Safety and Distribution Technology of Zhejiang Province Zhejiang UniversityHangzhou 310058 China

Correspondence should be addressed to Kejia Zhang zhangkjzjueducn

Received 2 February 2015 Accepted 14 March 2015

Academic Editor Jie Fu

Copyright copy 2015 Yan Ma et al This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The photocatalytic degradation of sulfonamides in aqueous TiO2suspension under UV irradiation has been investigated using

potassium ferrate as electron acceptors The results showed that the stability of Fe(VI) is dependent on pH significantly andthe stability reduces obviously in the presence of UV-TiO

2 The experiments indicated that Fe(VI) could effectively scavenge the

conduction band electrons from the surface of TiO2 The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be

much faster than that without Fe(VI) The SD SM and SMX concentration was greatly reduced by 892 834 and 820respectively after 10min with UV-TiO

2-Fe(VI) comparing to 652 660 and 719 respectively with Fe(VI) only in the dark

and 713 727 and 760 respectively with UV-TiO2 The pH value of solution significantly influenced the sulfonamides

degradation in UV-TiO2-Fe(VI) system The degradation amount of sulfonamides after 10min was a maximum at pH 7 The

intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested

that a majority of sulfonamides turned into large-molecule products without complete mineralization

1 Introduction

The widespread detection of pharmaceuticals active com-pounds in aquatic environments which are now recognizedas novel pollutants is raising public health concerns dueto the possibility of increased bacterial resistance [1] Sul-fonamides also known as sulfa drugs represent a kind oftypical antibiotics and have been widely used in humanand veterinary medicine to treat and prevent infectiousbacterial diseases [2]These sulfonamides are discharged intoaquatic environment in their original or metabolized formmainly via disposal of expired pharmaceuticals domesticwastewater effluents and excretion [3] It has been reportedthat sulfonamides are present in the concentration rangingfrom 013 to 19 120583g lminus1 in aquatic environment [4] Althoughsulfonamides are present in low concentrations their exis-tence in the environment may cause ecotoxicological effects[5] The water contaminated by antibiotics is incompatible

with conventional water and wastewater treatment methods[6] Thus it is necessary to develop more effective treatmenttechnologies to remove sulfonamides from water

Potassium ferrate (VI) (K2FeO4) is well known for a

long time for its strong oxidizing power in acidic (1198640 =+220V) and basic (1198640 = +072V) solution [7] and forproducing a coagulant (Fe(OH)

3) from its reduced formThe

previous studies indicate that the ferrate oxidation reactionfrom Fe(VI) to Fe(III) includes two sequential intermediatesof Fe(IV) and Fe(V) The studies demonstrated that thereactivity of Fe(V) with compounds is 103ndash105 times morethan Fe(VI) [8 9] which means that the reduction fromFe(VI) to Fe(V) is a critical rate-determining step in thewholereaction and the oxidation efficiency of potassium ferrate canbe enhanced by one-electron reducing agents such as theconduction band electrons (ecb

minus) [10]Photocatalytic water splitting on titanium dioxide (TiO

2)

was first discovered in 1972 [11] Since then a lot of attention

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 973942 10 pageshttpdxdoiorg1011552015973942

2 BioMed Research International

Table 1 The physical and chemical properties of sulfonamides standards

Chemical name Molecular formula Chemical structure Molecular weightDa p119870a [20]p119870a1 p119870a2

Sulfadiazine C10H10N4O2SNH2

N

N NH S

O

O

25027 249 650

Sulfamerazine C11H12N4O2S

NH2

CH3

N

N NH S

O

O

26430 mdash 700

Sulfamethoxazole C10H11N3O3SNH2

H3C

NH S

O

O

NO 25328 174 570

has been paid to photocatalytic degradation of numerousorganic contaminants in water using titanium dioxide inaqueous suspension because of the strong oxidizing powerof the photogenerated holes (hvb

+) of TiO2[12] In the pho-

tocatalytic process inhibiting the ecbminushvb+ recombination

by adding other electron acceptors to the reaction is onestrategy to enhance oxidative efficiency [13] The ecb

minus is agood reductant and Fe(VI) is a strong oxidizing agent Thusthe photoreduction of Fe(VI) may take place through one-electron steps that would result in the formation of Fe(V)Fe(IV) and Fe(III) Consider

Fe (VI)ecbminus

997888rarr Fe (V)

Fe (V)ecbminus

997888rarr Fe (IV)

Fe (IV)ecbminus

997888rarr Fe (III)

(1)

In this study potassium ferrate was used as electronacceptors to capture the electrons from TiO

2photocatalysis

to form Fe(V) while inhibiting the ecbminushvb+ recombina-

tion during photocatalytic reaction Fe(VI) reduction andsulfonamides degradation in aqueous solution were studiedunder different conditions This paper studied the analysis ofthe intermediate products and the pathways of sulfonamidesdegradation in the UV-TiO

2-Fe(VI) system

2 Materials and Methods

21 Materials All chemicals employed in the laboratoryexperiments were purchased as analytical grade and used

without any purificationThemain chemical including potas-sium ferrate (gt90 purity) and sulfonamides includingsulfadiazine (SD) sulfamerazine (SM) and sulfamethoxazole(SMX) (gt99) were purchased from Sigma-Aldrich Thesolutions were prepared with Milli-Q water The Fe(VI)solutions were prepared by adding solid potassium ferrateto 0001mol lminus1 borate0005mol lminus1 Na

2HPO4at pH 92 for

the stability of ferrate solution [9] The stock solutions of SDSM and SMX were prepared at concentration of 2mmol lminus1in 001molsdotlminus1 NaOH Table 1 shows the structure and thephysicochemical properties of sulfonamides

22 Methods

221 Experimental Procedure The stability of potassiumferrate in aqueous solution with different pH values from 70to 113 was determined The buffer solutions were preparedfrom K

2HPO4 KH2PO4 and K

2B4O7sdot5H2O with Milli-Q

water Each experiment the Fe(VI) solution with an initialconcentration of 02mmol lminus1 was prepared by adding agiven quantity of solid K

2FeO4to the respective buffer

solution and the decomposition of samples was observedby determining the concentration of Fe(VI) at different timeintervals

The reaction solutions were prepared in 001mol lminus1buffers to obtain the desired pH values All experiments werecarried out in 250ml beakers at room temperature (25∘C plusmn2∘C) Each experiment lasted for 10min and samples werecollected at different time intervals for SD SM and SMXanal-yses A UV lamp (Philips) with a main emission at 254 nmwas employed in this study The light intensity on to thereaction solution was determined to be 015mWcmminus2 TiO

2

BioMed Research International 3

(anatase nanometre grade lt50 nm BET 80ndash100m2sdotgminus1Aladdin) was used as a photocatalyst The TiO

2catalyst

(500mg lminus1) and potassium ferrate were applied at differentconcentrations for the different experiments Sodium hypo-sulfite solution was added immediately to the sample at eachsampling time to stop any further reaction

222 Analytical Methods The concentrations of potassiumferrate in aqueous solutions were determined by UV-visspectroscopy (Unico WFZ UV-4802H) K

2FeO4dissolved as

FeO4

2minus has the absorption peak at 510 nm and its molarabsorptivity at 510 nm has been determined as 1150Mminus1 cmminus1[14]

The concentration of SD SM and SMX was deter-mined by HPLC (Waters e2695 Separation Module Waters2489UVvisible detector) with a Waters bridge C18 col-umn (150mm times 46mm) and ultraviolet detector settingwavelength of 270 nm at 35∘C Elution was performed witha mobile phase composed of acetonitrilewater with 01formic acid (4060 vv) at a flow rate of 08mLminminus1

Liquid chromatography (Waters e2695 Separation Mod-ule) together with heated electrospray ionization mass spec-trometry (Thermo Finnigan TSQ Quantum) was used todetect the intermediate products of sulfonamides degrada-tion In the LC-HESI-MS-MS analysis sample separationwasconducted on aThermoBasicC18 column (150mmtimes 21mm)at a flow rate of 03mlminminus1 and column temperature of 35∘CChromatographic analyses were carried out using gradientelution with eluent A (acetonitrile) and eluent B (water with01 formic acid) The analysis started with 10 of eluent Aheld for 5min and then was increased linearly up to 40 in15min This composition was returned to 10 of eluent A in3min followed by a reequilibration time of 3min to give atotal run time of 26min The ESI source was set in positiveion detection mode The MS conditions were as follows thespray voltage 35 kV sheath gas pressure 40 psi auxiliary gaspressure 10 psi capillary temperature 270∘C and the massrange is 50ndash500119898119911

In this study total organic carbon (TOC) of samples wasdetermined by TOC analyzer (Shimadzu TOC-VCPH)

3 Results and Discussions

31 Stability of Potassium Ferrate

311 The Effect of Solution pH Aqueous potassium ferratesolutions with an initial concentration of 02mmol lminus1 wereprepared with different pH values from 70 to 113The Fe(VI)concentration was determined by UV-vis spectroscopy every30 s As shown in Figure 1 it is clear that the decompo-sition of Fe(VI) can be described with first-order kineticmodel expressed by the following equation 119889[FeO

4

2minus]119889119905 =

119896[FeO4

2minus] 1198772 values which are greater than 099 for all pH

values (Table 2) also show the applicability of this model todescribe ferrate decomposition

The decomposition kinetic constants are shown inTable 2 indicating that the stability of the ferrate is highly pHdependent and Fe(VI) is more stable in alkaline conditions

ln([

FeO

42minus

]([

FeO

42minus] 0

)

0

minus05

minus1

minus15

minus2

minus25

minus3

minus35

t (s)0 100 200 300 400 500 600

pH = 70

pH = 81

pH = 91

pH = 100

pH = 113

Figure 1 The decomposition of Fe(VI) in aqueous solution([Fe(VI)]

0= 02mmol lminus1)

t (s)0 100 200 300 400 500 600

[FeO

42minus

]([

FeO

42minus] 0

1

08

06

04

02

0

Fe(VI)Fe(VI)-TiO2

Fe(VI)-UVFe(VI)-UV-TiO2

Figure 2 The decomposition of Fe(VI) in aqueous solutionunder UV irradiation ([Fe(VI)]

0= 02mmol lminus1 light intensity =

015mWcmminus2 pH 91 and [TiO2] = 500mg lminus1)

Table 2 The kinetic constants of Fe(VI) decomposition with pH

pH 70 81 91 100 113119896 (times10minus4 sminus1) 491 155 0367 227 4651198772 09975 09987 09972 09981 09988

It is evident that there appeared to be a maximum stability atpH 90ndash100 and Fe(VI) is highly unstable at pH lt7

312 The Effect of UV-TiO2 Aqueous potassium ferratesolutions (02mmol lminus1) were prepared at pH 91The decom-position of potassium ferrate in aqueous TiO

2suspension

under UV irradiation is shown in Figure 2 At high pH(91) potassium ferrate was very stable and adding TiO

2had


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(a)

cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(b)

TiO2Fe(VI)

UV-TiO2UV-TiO2-Fe(VI)

cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(c)

Figure 3The removal of different sulfonamides byUV-TiO2-Fe(VI) ((a) sulfadiazine (b) sulfamerazine (c) sulfamethoxazole [sulfadiazine]

0

= 002mmol lminus1 [sulfamerazine]0= 002mmol lminus1 [sulfamethoxazole]

0= 002mmol lminus1 [Fe(VI)]

0= 005mmol lminus1 pH 7 [TiO

2] = 500mg lminus1

and light intensity = 015mWcmminus2)

little effect on the stability of potassium ferrate without UVirradiation Under UV irradiation the stability of potassiumferrate could be decreased significantly The decomposi-tion rate of potassium ferrate was the highest in aqueousFe(VI) + TiO

2solution under UV irradiation and about

80 of potassium ferrate was decomposed after 10min ofphotocatalytic reaction In UV-TiO

2-Fe(VI) system Fe(VI)

captured the electrons from TiO2to form Fe(V) Fe(IV)

and Fe(III) through one-electron steps which accelerated thedecomposition rate of potassium ferrate

32 Degradation of Sulfonamides in UV-TiO2-Fe(VI) System

321 Sulfonamides Degradation In order to analyse thedegradation of sulfonamides at different conditions a setof experiments was carried out under four conditions(I) TiO

2only in the dark (II) Fe(VI) only in the dark

(III) UV-TiO2 and (IV) UV-TiO

2-Fe(VI) The experimental

results are shown in Figure 3 Figure 3 shows that the finalconcentrations of sulfonamides (SD SM and SMX) werealmost the same with the initial concentration verifyingthat no losses occurred from TiO

2only in the dark The

degradation of SD SM and SMX by ferrate oxidation onlyafter 10min reaction was achieved by 652 660 and719 respectively and the SD SM and SMX degradationby catalytic oxidation alone (UV-TiO

2) was achieved by

713 727 and 760 respectively Under UV irradiationtogether with TiO

2and Fe(VI) the concentrations of SD

SM and SMX were greatly reduced by 892 834 and820 respectively after 10min Due to the interaction ofphotocatalytic oxidation and Fe(VI) oxidation higher rate ofsulfonamides degradation was achieved and the oxidation ofsulfonamides was enhanced greatly in the UV-TiO

2-Fe(VI)

system In this interactive reaction Fe(VI) captured the ecbminus

fromTiO2to formFe(V) which could inhibit the recombina-

tion of ecbminushvb+ simultaneously [10 13] sulfonamides were


Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(a)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(b)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

Fe(VI)UV-TiO2-Fe(VI)

(c)

Figure 4 The removal of different sulfa antibiotics by UV-TiO2-Fe(VI) under different pH values ((a) sulfadiazine (b) sulfamerazine

(c) sulfamethoxazole [sulfadiazine]0= 002mmol lminus1 [sulfamerazine]

0= 002mmol lminus1 [sulfamethoxazole]


0=

005mmol lminus1 [TiO2] = 500mg lminus1 and light intensity = 015mWcmminus2)

quickly degraded by several oxidants including ∙OH hvb+

Fe(VI) and Fe(V) The previous study [8] demonstrated thatthe reaction rate of Fe(V) with compounds is 3ndash5 orders ofmagnitude faster than Fe(VI) As a result the degradationof sulfonamides in the UV-TiO

2-Fe(VI) system could be

accelerated significantly

322 The Effect of Solution pH The experiments wereperformed in the pH range of 5ndash9 As shown in Figure 4the removal of sulfonamides is much higher in UV-TiO

2-

Fe(VI) system than that resulting from ferrate oxidationalone in the pH range of 5ndash9 and the solution pH valuesignificantly influenced the sulfonamides degradation AtpH 7 the removal of SD SM and SMX is the highest inthe pH range of 5ndash9 The possible reason for the increaseddegradation is that this pH (7) is close to the pKa

2values of

SD (65) SM (70) and SMX (57) At this pH SD SM and

SMX are dissociated (Figure 5) Previous studies found thatthe dissociation of the compound increases with increasingpH and deprotonated compounds are more readily oxidizedby potassium ferrate and other oxidants such as ∙OH andhvb+ [15 16]Meanwhile potassium ferrate had amuchhigher

oxidation potential at acidic condition (1198640 = 220V) thanthat at basic conditions (1198640 = 072V) [17] At pHlt7 althoughoxidative ability of ferrate is high the ferrate is highly unstable(Figure 1) Therefore at pH 5 most Fe(VI) is decomposed tomake the removal rate of sulfonamides low In the UV-TiO

2-

Fe(VI) system the ferrate oxidations of sulfonamides wereenhanced most significantly at pH 9 due to the low oxidationability of ferrate

323 Pathways of Sulfonamides Degradation with UV-TiO2-Fe(VI) The formation of intermediates products was dis-cussed in the experiments in which sulfonamides were


Table 3 The main identified intermediates of sulfonamides

Chemical name 119898119911 Molecular structure

Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H

NH2 NH2NH3+ pKa1 pKa2 N

minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)

Figure 5 The protonation and deprotonation of sulfonamides ((a) sulfadiazine (b) sulfamerazine (c) sulfamethoxazole)

degraded in the UV-TiO2-Fe(VI) system The samples were

taken after 10min of reaction and analysed by LC-HESI-MS-MS The main identified intermediates of sulfonamides areshown in Table 3 The 119898119911 values correspond to [M + 1]+ions in the positive mode of LC-HESI-MS-MS Accordingto the results the molecular structures of SD SM and SMXhave molecular weights [M + 1]+ = 251 265 and 254 Fourintermediates have been identified for SD and SM whosemolecular weights were 267 173 96 and 281 and 281 173 110and 295 respectively Five intermediates have been identifiedfor SMX whose molecular weights were 270 288 173 99and 284 The peak corresponding to the molecular weights267 281 and 270 seems to be hydroxylated analogues ofSD SM and SMX As shown in Table 3 it seems that theNndashS in sulfonamides can be cleaved by oxidation of UV-TiO2-Fe(VI) The attack on NH

2group of the aniline moiety

as well as the isoxazole moiety of SMX happened duringthe ferrate oxidation involving a single electron-transfermechanism as shown by Sharma [18] and Huang [19] Basedon these identified intermediate products the pathwaysfor the sulfonamides degradation by UV-TiO

2-Fe(VI) are

proposed schematically in Figure 6The results indicated thata majority of sulfonamides transformed into large-moleculeproducts without complete mineralization Total organiccarbon analysis was performed to observe the mineralizationefficiency of sulfonamides degraded by UV-TiO

2-Fe(VI)

The initial TOC of SD SM and SMX was 2185mgsdotlminus12267mgsdotlminus1 and 2194mgsdotlminus1 respectively and the TOC ofSD SM and SMX after 10min reaction was 2172mgsdotlminus12255mgsdotlminus1 and 2181mgsdotlminus1 respectively indicating that thedegradation of sulfonamides mostly produced intermediateproducts and little mineralization to carbon dioxide in theUV-TiO

2-Fe(VI) system

4 Conclusions

In this study sulfonamides as typical antibiotic chemicalswere studied to be degraded in the UV-TiO

2-Fe(VI) system

The experimental results showed that the decomposition rateof Fe(VI) was highly dependent on pH and the stabilityof Fe(VI) reduced obviously in the presence of UV-TiO

2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)

Figure 6 Proposed degradation pathway of sulfa antibiotics oxidized by potassium ferrate combined with photocatalytic oxidation ((a)sulfadiazine (b) sulfamerazine (c) sulfamethoxazole)

The results also indirectly demonstrated that Fe(VI) couldbe reduced by ecb

minus on the TiO2surface to form Fe(V) and

to inhibit ecbminushvb+ recombination in the UV-TiO

2-Fe(VI)

system which can significantly enhance the removal ofsulfonamides Therefore the combination of photocatalyticoxidation and ferrate oxidation is an effective treatmenttechnology for the treatment of sulfonamides in aquatic envi-ronment In order to identify the formation of intermediatereaction products and clarify the degradation pathways ofsulfonamides in the UV-TiO

2-Fe(VI) system the extension

of sulfonamides degradation and TOC mineralization weremonitored in this study The analyses by LC-HESI-MS-MSand TOC analyzer indicated that a majority of sulfonamidesturned into large-molecule products without complete min-eralization

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This project was supported jointly by National NaturalScience Foundation of China (51208456) the National MajorScience and Technology Project of China (2012ZX07403-0012012ZX07403-002 and 2012ZX07403-003) and Foundationof Key Disciplines of Zhejiang University of Technology (no20130307)

References

[1] F Pomati S Castiglioni E Zuccato et al ldquoEffects of a complexmixture of therapeutic drugs at environmental levels on humanembryonic cellsrdquoEnvironmental Science andTechnology vol 40no 7 pp 2442ndash2447 2006

[2] K Kummerer ldquoAntibiotics in the aquatic environmentmdashareviewmdashpart Irdquo Chemosphere vol 75 no 4 pp 417ndash434 2009

[3] K Kummerer ldquoAntibiotics in the aquatic environmentmdashareviewmdashpart IIrdquo Chemosphere vol 75 no 4 pp 435ndash441 2009

[4] A L Boreen W A Arnold and K McNeill ldquoPhotochemicalfate of sulfa drugs in the aquatic environment sulfa drugs


containing five-membered heterocyclic groupsrdquo EnvironmentalScience amp Technology vol 38 no 14 pp 3933ndash3940 2004

[5] O AH Jones N Voulvoulis and J N Lester ldquoHuman pharma-ceuticals in the aquatic environment a reviewrdquo EnvironmentalTechnology vol 22 no 12 pp 1383ndash1394 2001

[6] O Rozas D ContrerasM AMondacaM Perez-Moya andHD Mansilla ldquoExperimental design of Fenton and photo-Fentonreactions for the treatment of ampicillin solutionsrdquo Journal ofHazardous Materials vol 177 no 1ndash3 pp 1025ndash1030 2010

[7] R H Wood ldquoThe heat free energy and entropy of theferrate(VI) ionrdquo Journal of the American Chemical Society vol80 no 9 pp 2038ndash2041 1958

[8] V K Sharma and B H Bielski ldquoReactivity of ferrate(VI) andferrate(V) with amino acidsrdquo Inorganic Chemistry vol 30 no23 pp 4306ndash4310 1991

[9] V K Sharma ldquoOxidation of inorganic contaminants by ferrates(VI V and IV)-kinetics and mechanisms a reviewrdquo Journal ofEnvironmental Management vol 92 no 4 pp 1051ndash1073 2011

[10] C Li and X Z Li ldquoDegradation of endocrine disruptingchemicals in aqueous solution by interaction of photocatalyticoxidation and ferrate (VI) oxidationrdquoWater Science amp Technol-ogy vol 55 no 1-2 pp 217ndash223 2007

[11] A Fujishima and K Honda ldquoElectrochemical photolysis ofwater at a semiconductor electroderdquo Nature vol 238 no 5358pp 37ndash38 1972

[12] C R Chenthamarakshan K Rajeshwar and E J WolfrumldquoHeterogeneous photocatalytic reduction of Cr(VI) in UV-irradiated titania suspensions effect of protons ammoniumions and other interfacial aspectsrdquo Langmuir vol 16 no 6 pp2715ndash2721 2000

[13] B-L Yuan X-Z Li and N Graham ldquoAqueous oxidationof dimethyl phthalate in a Fe(VI)-TiO

2-UV reaction systemrdquo

Water Research vol 42 no 6-7 pp 1413ndash1420 2008[14] B H J Bielski andM JThomas ldquoStudies of hypervalent iron in

aqueous solutions 1 Radiation-induced reduction of iron(VI)to iron(V) by COminus

2rdquo Journal of the American Chemical Society

vol 109 no 25 pp 7761ndash7764 1987[15] C Li X Z Li and N Graham ldquoA study of the preparation and

reactivity of potassium ferraterdquo Chemosphere vol 61 no 4 pp537ndash543 2005

[16] H Hoigne and H Bader ldquoRate constants of reactions ofozone with organic and inorganic compounds in water IIDissociating organic compoundsrdquo Water Research vol 17 no2 pp 185ndash194 1983

[17] J Q Jiang ldquoResearch progress in the use of ferrate(VI) for theenvironmental remediationrdquo Journal of Hazardous Materialsvol 146 no 3 pp 617ndash623 2007

[18] V K Sharma ldquoOxidation of inorganic compounds by Ferrate(VI) and Ferrate(V) one-electron and two-electron transferstepsrdquo Environmental Science and Technology vol 44 no 13 pp5148ndash5152 2010

[19] H Huang D Sommerfeld B C Dunn C R Lloyd and EM Eyring ldquoFerrate(VI) oxidation of anilinerdquo Journal of theChemical Society Dalton Transactions vol 8 no 3 pp 1301ndash1305 2001

[20] A Kaufmann S Roth B RyserMWidmer andDGuggisbergldquoQuantitative LCMS-MS determination of sulfonamides andsome other antibiotics in honeyrdquo Journal of AOAC Internationalvol 85 no 4 pp 853ndash860 2002


Table 1 The physical and chemical properties of sulfonamides standards

Chemical name Molecular formula Chemical structure Molecular weightDa p119870a [20]p119870a1 p119870a2

Sulfadiazine C10H10N4O2SNH2

N

N NH S

O

O

25027 249 650

Sulfamerazine C11H12N4O2S

NH2

CH3

N

N NH S

O

O

26430 mdash 700

Sulfamethoxazole C10H11N3O3SNH2

H3C

NH S

O

O

NO 25328 174 570

has been paid to photocatalytic degradation of numerousorganic contaminants in water using titanium dioxide inaqueous suspension because of the strong oxidizing powerof the photogenerated holes (hvb

+) of TiO2[12] In the pho-

tocatalytic process inhibiting the ecbminushvb+ recombination

by adding other electron acceptors to the reaction is onestrategy to enhance oxidative efficiency [13] The ecb

minus is agood reductant and Fe(VI) is a strong oxidizing agent Thusthe photoreduction of Fe(VI) may take place through one-electron steps that would result in the formation of Fe(V)Fe(IV) and Fe(III) Consider

Fe (VI)ecbminus

997888rarr Fe (V)

Fe (V)ecbminus

997888rarr Fe (IV)

Fe (IV)ecbminus

997888rarr Fe (III)

(1)

In this study potassium ferrate was used as electronacceptors to capture the electrons from TiO

2photocatalysis

to form Fe(V) while inhibiting the ecbminushvb+ recombina-

tion during photocatalytic reaction Fe(VI) reduction andsulfonamides degradation in aqueous solution were studiedunder different conditions This paper studied the analysis ofthe intermediate products and the pathways of sulfonamidesdegradation in the UV-TiO

2-Fe(VI) system

2 Materials and Methods

21 Materials All chemicals employed in the laboratoryexperiments were purchased as analytical grade and used

without any purificationThemain chemical including potas-sium ferrate (gt90 purity) and sulfonamides includingsulfadiazine (SD) sulfamerazine (SM) and sulfamethoxazole(SMX) (gt99) were purchased from Sigma-Aldrich Thesolutions were prepared with Milli-Q water The Fe(VI)solutions were prepared by adding solid potassium ferrateto 0001mol lminus1 borate0005mol lminus1 Na

2HPO4at pH 92 for

the stability of ferrate solution [9] The stock solutions of SDSM and SMX were prepared at concentration of 2mmol lminus1in 001molsdotlminus1 NaOH Table 1 shows the structure and thephysicochemical properties of sulfonamides

22 Methods

221 Experimental Procedure The stability of potassiumferrate in aqueous solution with different pH values from 70to 113 was determined The buffer solutions were preparedfrom K

2HPO4 KH2PO4 and K

2B4O7sdot5H2O with Milli-Q

water Each experiment the Fe(VI) solution with an initialconcentration of 02mmol lminus1 was prepared by adding agiven quantity of solid K

2FeO4to the respective buffer

solution and the decomposition of samples was observedby determining the concentration of Fe(VI) at different timeintervals

The reaction solutions were prepared in 001mol lminus1buffers to obtain the desired pH values All experiments werecarried out in 250ml beakers at room temperature (25∘C plusmn2∘C) Each experiment lasted for 10min and samples werecollected at different time intervals for SD SM and SMXanal-yses A UV lamp (Philips) with a main emission at 254 nmwas employed in this study The light intensity on to thereaction solution was determined to be 015mWcmminus2 TiO

2



2catalyst



2FeO4dissolved as

FeO4








4

2minus]119889119905 =

119896[FeO4




ln([

FeO

42minus

]([

FeO

42minus] 0

)

0

minus05

minus1

minus15

minus2

minus25

minus3

minus35

t (s)0 100 200 300 400 500 600

pH = 70

pH = 81

pH = 91

pH = 100

pH = 113


0= 02mmol lminus1)

t (s)0 100 200 300 400 500 600

[FeO

42minus

]([

FeO

42minus] 0

1

08

06

04

02

0

Fe(VI)Fe(VI)-TiO2









2suspension


2had


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(a)

cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(b)

TiO2Fe(VI)


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(c)


0




2] = 500mg lminus1
















2) was achieved by




2-Fe(VI)





Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(a)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(b)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9


(c)





0=







2-


2values of




2-






Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References





























2catalyst



2FeO4dissolved as

FeO4








4

2minus]119889119905 =

119896[FeO4




ln([

FeO

42minus

]([

FeO

42minus] 0

)

0

minus05

minus1

minus15

minus2

minus25

minus3

minus35

t (s)0 100 200 300 400 500 600

pH = 70

pH = 81

pH = 91

pH = 100

pH = 113


0= 02mmol lminus1)

t (s)0 100 200 300 400 500 600

[FeO

42minus

]([

FeO

42minus] 0

1

08

06

04

02

0

Fe(VI)Fe(VI)-TiO2









2suspension


2had


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(a)

cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(b)

TiO2Fe(VI)


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(c)


0




2] = 500mg lminus1
















2) was achieved by




2-Fe(VI)





Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(a)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(b)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9


(c)





0=







2-


2values of




2-






Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References




























cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(a)

cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(b)

TiO2Fe(VI)


cc 0

10

08

06

04

02

00

t (min)0 1 2 3 4 5 6 7 8 9 10

(c)


0




2] = 500mg lminus1
















2) was achieved by




2-Fe(VI)





Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(a)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(b)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9


(c)





0=







2-


2values of




2-






Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References




























Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(a)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9

(b)

Rem

oval

()

100

80

60

40

20

0

pH5 7 8 9


(c)





0=







2-


2values of




2-






Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References






























Sulfadiazine

267NH2

NH2

N

N SO

O

NH

HON

N SO

O

NH

OH

173 NH2HO SO

O

96 NH2

N

N

281NO2

N

N SO

ON

H

Sulfamerazine

281

NH2NH2

CH3CH3

N

N SO

O

NH

OH N

N SO

O

N

H

HO

173 NH2HO SO

O

110NH2

N

N

H3C

295

NO2

CH3

N

N N SO

OH

Sulfamethoxazole

270NH2 NH2

H3C H3CN S

O

O

O N

H

OH

N SO

O

O N

HHO

NH2H3C N S

O

O

O N

H

O

288NH2H3C N S

O

O

O N

HHO

HO


Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References




























Table 3 Continued


173 NH2HO SO

O

99NH2H3C

O N

284NO2H3C N S

O

O

O N

H


minus

N

N SO

O

N

N SO

ONH

N

N SO

ONH

(a)

NH2NH2

CH3CH3CH3

NH3+

pKa1 pKa1Nminus

N

N N SO

OH

N

N N SO

OH

N

N SO

O

(b)

NH2NH2H3C H3C H3C

NH3+

pKa1 pKa2NminusN S

O

O

O N

H

N SO

O

O N

HSO

O

O N

(c)






2-Fe(VI) are


2-Fe(VI)


2-Fe(VI) system

4 Conclusions


2-Fe(VI) system


2


N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References




























N

N SO

ONH

N

N SO

ONH

OH

Fe(VI)N

N SO

ONH

S

O

O

N

N

SO

OHO

+

N

N

SO

OHO

N

N

OH

N

N SO

ONH

HO

SO

OHO

HO

N

N

HO

++

+

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH

∙OH

∙OH

∙OH∙OH

∙OH

(a)

Fe(VI)N

N SO

ONH

SO

OHO

SO

OHO

+

SO

OHO

OH

N

N SO

ONH

HO

SO

OHO

N

N

HO

++ +

N

N SO

ONH

N

N SO

ONH

OH

N

N

N

N

N

N

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH

∙OH

CH3

CH3

CH3

CH3

H3CH3C

H3C

H3C

(b)

Figure 6 Continued


NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References




























NH2

NH2

NH2

NH2

NH2NH2

NH2NH2

NH2

NH2

NH2

NH2

NO2

NO2

∙OH∙OH

∙OH

∙OH

∙OH∙OH

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

H3C

Fe(VI)

SO

OHO

SO

OHO

+SO

OHO

OHSO

OHO+

++

N SO

O

O N

H

N SO

O

O N

H

OH

O N

O N

N SO

O

O N

HHOHO

O N

HOHO

O N

N SO

O

O N

H

O

N SO

O

O N

H

+

ON

O

+

(c)





2-Fe(VI)






Acknowledgments


References

















































Documents

Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2 ...Sulfamerazine C 11 H 12 N 4 O 2 S NH2 CH3 N N NH S O O 264.30 — 7.00 Sulfamethoxazole C 10 H 11 N 3 O 3 S NH2 H3C NH S