sonocatalytic degradation of antibiotics tetracycline by mn...

Research ArticleSonocatalytic Degradation of Antibiotics Tetracycline byMn-Modified Diatomite

Yiping Guo Xiao Mi Guoting Li and Xi Chen

Department of Environmental and Municipal Engineering North China University of Water Resources and Electric PowerZhengzhou 450011 China

Correspondence should be addressed to Yiping Guo 82275113qqcom

Received 7 September 2016 Revised 28 October 2016 Accepted 23 November 2016 Published 23 January 2017

Academic Editor Mohammad A Al-Ghouti

Copyright copy 2017 Yiping Guo et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Mn-modified diatomite was prepared by wet impregnation and subsequent calcinations processes It was used as catalyst forsonocatalytic degradation of antibiotics tetracycline Characterizations by scanning electron microscopy and X-ray diffractionpattern showed that the morphology and crystal structure of the modified diatomite were similar to these of raw diatomiteDespite containing very limited amount of Mn oxides the Mn-modified diatomite showed much higher sonocatalytic activitythan the raw diatomite The increases in both MnSO4 concentration of the wet impregnation solution and the catalyst dosagecould enhance the degradation of antibiotics tetracycline significantly 119870app values for ultrasonication catalyst adsorption andboth processes combined (010molLMnSO4-modified diatomite) were 122 times 10minus4 000193 and 000453minminus1 respectively whilethe corresponding values of1198772 were 0956 0986 and 0953 respectivelyThese results demonstrated the significant synergetic effectby combining ultrasonication and catalyst adsorption processes The presence of isopropanol KBr and NaN3 quenched a series ofreactive oxygen species sharply indicating the dominant role of reactive oxygen species in the sonocatalytic process In contrastthe addition of Fe(II) enhanced the degradation due to the generation of more OH∙ radicals in the concurrent Fenton reaction Allthe results indicated that Mn-modified diatomite had the great potential for water treatment by sonocatalytic oxidation

1 Introduction

As one of the advanced oxidation processes (AOPs) sono-chemical process has attracted wide attention because it iscapable of degrading a large variety of organic pollutants[1ndash6] It is well known that AOPs are characterized by thegeneration of highly reactive hydroxyl radicals as the mainoxidative species for the breakdown and mineralization oforganic contaminants [7 8] During sonochemical processacoustic cavitation generates hot spots with localized temper-atures and pressures on the order of 5000K and hundredsof atmospheres respectively Thermal dissociation of watervapor into reactive hydroxyl radicals and the formation ofother radicals occur as the following equations [4 9 10]

H2O 997888rarr H∙ +OH∙ (1)

O2 997888rarr 2∙O (2)∙O +H2O 997888rarr 2HO∙ (3)

H∙ +O2 997888rarr HO∙ +O (4)

Accordingly reactive oxygen species (ROSs) such as OH∙and OOH∙ are produced through a series of reactions andcontribute to the decomposition of organic contaminants

However sonochemical process alone has a very limitedefficiency and consumes considerable energy for the decom-position of organic contaminants [5 11] In order to enhancethe degradation performance catalysts are needed to assistsonochemical process which is called sonocatalytic processA number of catalysts have been tested in sonocatalyticprocess [2 5 11 12] It was reported that the efficiency of sono-chemical degradation process can be improved by these cata-lysts dramatically Recently natural diatomitewas also provento be capable of catalyzing the sonochemical degradationof methylene blue and a synergetic effect was also observed[13] As a siliceous and low-cost material abundant in naturalenvironment diatomite has the potential for practical sono-catalytic process because it possesses advantages such as high

HindawiJournal of ChemistryVolume 2017 Article ID 2830138 8 pageshttpsdoiorg10115520172830138

2 Journal of Chemistry

porosity high permeability large surface area and chemicalinertness [14] Meanwhile Mn oxides were proven to be anexcellent catalyst under ultrasonic irradiation as well [15 16]The combination of diatomite with Mn oxides might furtherenhance the sonochemical degradation efficiency due to thepossible synergetic effect In this research manganese oxideswere immobilized onto natural diatomite by wet impreg-nation and subsequent calcinations processes The compos-ite of manganese oxides and diatomite was used for thesonochemical degradation of organic pollutants to evaluatesonocatalytic performance

Tetracyclines are the secondmost widely used antimicro-bial chemicals globally which are widely applied in humantherapy and livestock industry [17] As tetracyclinemoleculesare usually neutral or negatively charged in environmen-tal water conventional techniques such as sand filtrationsedimentation flocculation and coagulation are not veryefficient for tetracycline removal as expected [18] As a resulttetracycline was selected as a target organic pollutant forthe sonocatalytic process in this study Additionally themechanism for the enhanced degradation performance ofsonocatalytic process has not yet been reported in detailHence the oxidation mechanism was indirectly evaluatedby adding scavengers such as isopropanol NaN3 and KBrrespectively The effect of radical promoter Fe(II) was alsoinvestigated concurrently

2 Materials and Methods

21 Materials Tetracycline (TC) was purchased from HefeiBomei Biological Science and Technology Co Ltd (Anhuiprovince China) and it was used without further purifica-tion Diatomite was provided by Linjiang Meston PowderyMaterials Co Ltd (Jilin province China) Other chemicalsused were of analytical grade Deionized (DI) water was usedto prepare all solutions

22 Preparation of Mn-Modified Diatomite A series ofMnSO4 solutions with a concentration gradient of 001 005010 050 and 10molL were used for the wet impregna-tion of the raw diatomite The diatomitesolution ratio was1 g10mLThemixture of diatomite andMnSO4 solution wasagitated in an orbital shaker at 140 rpmand room temperaturefor 24 h The modified diatomite was collected by filtrationand dried at 100∘C overnight Finally the raw diatomite andtreated diatomite were calcined at 500∘C for 2 hThe prepared010molL MnSO4-modified diatomite is denoted as Mn-modified diatomite

23 Characterization The morphologies of raw diatomiteand the Mn-modified diatomite were recorded on a PhilipsQuanta-2000 scanning microscope coupled with an energydispersive X-ray (EDX) spectrometerTheir X-ray diffraction(XRD) patterns were recorded on a Rigaku DMAX-3B X-diffractometer FTIR spectra (KBr pellets) were recorded ona Nicolet NEXUS 470 FTIR spectrophotometer from 400 to4000 cmminus1

24 Sonocatalytic Degradation of TC by Mn-Modified Dia-tomite Degradation of TC was carried out in a beaker for60min The available volume of the beaker was 250mL and200mL of TC solution was added Sonication was performedin a 40 kHz ultrasonic cleaning bath (AS3120A KunshanUltrasonic Instruments Co Jiangsu China) The power ofthe ultrasonic cleaning bath was 50W The water-circulatingunit was used to control water bath temperature

25 Analyses Samples were collected and filtered through a045 120583m membrane before analyzing The concentration ofTC was determined by measuring the maximum absorbanceat a fixed wavelength (360 nm) [19] using an UVmini-1240spectrophotometer (Shimadzu Japan)

The removal efficiency of TC was calculated as

removal efficiency = (1 minus 1198621199051198620) times 100 (5)

The pseudo-first-order kinetics for TC degradation wassimulated as [20]

ln(1198620119862119905 ) = 119870app119905 (6)

where 119862119905 is the TC concentration at time 119905 1198620 is the initialTC concentration and 119870app is the apparent first-order rateconstant

3 Results and Discussion

31 Characterization of Mn-Modified Diatomite The rawdiatomite used was comprised of the discoid plates like lotushead and fragments of these plates Most of the discoid plateswere in the range of 5ndash50120583m These data had been referredto in our previous study [13] As illustrated in Figure 1(a) forthe Mn-modified diatomite there was no significant changein the morphologies after the modification The content ofmanganese element was found to be about 022 (atomicratio) by EDX analysis as presented in Figure 1(b) Thisindicated that only a very limited amount of Mn oxides wasimmobilized onto the diatomite

The XRD patterns of the raw diatomite and the used Mn-modified diatomite were examined and presented in Figure 2The strong and broad peak at 2120579 = 218∘ was related to thediffraction peak of cristobalite (JCPDS number 39-1425)while the weak peak at 2120579 = 266∘ was attributed to quartz(JCPDS number 46-1045) Both the two peaks were themajor characteristic peaks of diatomite Apparently the XRDpatterns of the Mn-modified diatomite were almost identicalto those of the raw one This result demonstrated that thestructure of diatomite was not significantly changed after themodification

The FTIR spectra of the raw diatomite the Mn-modified diatomite and the used Mn-modified diatomitewere recorded in Figure 3 respectively As the content ofsilicon element was found to be about 3334 (atomic ratio)by EDX analysis the absorption bands at 465 and 800 cmminus1were evidently ascribed to the vibrations of SindashO group

Journal of Chemistry 3

(a)

O

C MgAl

Si

AuAuMn

200

800

100

500

600

700

300

900

400

1100

1200

1000

1300

Energy (keV)

00

12

23KCnt

35

46

58

(b)

Figure 1 SEM image (a) and EDX graph (b) of Mn-modified diatomite

a Raw diatomiteb Mn-modified diatomite

b

Inte

nsity

(au

)

a

20 30 40 50 60102120579 (degree)

Figure 2 XRD patterns of raw diatomite (a) and Mn-modifieddiatomite (b)

For both the raw Mn-modified diatomite and the used Mn-modified diatomite after the sonocatalytic degradation theyshared the bands at 556 616 and 724 cmminus1 which could beattributed to the immobilization of Mn oxides [21] Herethe presence of Mn oxides on the modified diatomite wasevidently confirmed

32 Effect of MnSO4 Concentration on the SonocatalyticDegradation of TC As the concentration of MnSO4 used inthe wet impregnation solution for the raw diatomite variedfrom 001 to 10molL the content of Mn oxides immobilizedon the diatomite was expected to increase accordingly Theeffect of MnSO4 concentration on catalytic activity of themodified diatomite in the sonocatalytic degradation of TC

800

465

556

616

724

c

b

Tran

smitt

ance

a

900 800 700 600 500 4001000Wavenumber (cmminus1)

Figure 3 FTIR spectra of raw diatomite (a) raw Mn-modifieddiatomite (b) and used Mn-modified diatomite (c)

was investigated and the results were plotted in Figure 4119870appvalues for the diatomite modified withMnSO4 concentrationof 001 005 010 050 and 10molL were 000341 000384000453 000521 and 000586minminus1 respectively while thecorresponding values of 1198772 were 0930 0930 0953 0916and 0937 respectively Evidently the degradation efficiencyof TC increased with the increase in MnSO4 concentrationbecause of the increased amounts of Mn oxides immobilizedon the modified diatomite As a comparison 119870app value forthe raw diatomite that is when MnSO4 concentration waszero in Figure 4 only achieved 000163minminus1 while 1198772 valuewas 0961 which was only about one-third of 119870app valueon the 010molL MnSO4-modified diatomite However thecontent of Mn element was found to be only about 022(atomic ratio) on the 01molL MnSO4-modified diatomiteIt seemed that the very limited amount of Mn oxides


000

008

016

024

032

ln(C

0C

t)

10 20 30 40 50 600Time (min)

0molL MnSO4

10 molL MnSmolL MnS

O4

05 O4

01 molL MnSO4

005 molL MnSO4

001 molL MnSO4

Figure 4 Effect of MnSO4 concentrations on the sonocatalyticdegradation of TC (conditions catalyst dosage of 160mg in 200mLTC solution and TC concentration of 50mgL at neutral pH)

could enhance TC degradation significantly Due to the factthat the enhancement effect of MnSO4 concentration onlyimproved slightly when MnSO4 was further increased afterthe concentration value of 010molL the 010molLMnSO4-modified diatomite was used in the following study whichwas also denoted as Mn-modified diatomite as mentionedpreviously

33 Synergetic Effect for the Sonocatalytic Degradation ProcessAs reported in our previous study the combination ofdiatomite and ultrasonication could lead to the significantsynergetic effect [13] As presented in Figure 5 the threeprocesses including ultrasonication catalyst adsorption andthe combined process were compared However the TCremovalmechanisms concerning ultrasonication and catalystadsorption were totally different in nature TC was degradedby a series of oxidizing species generated during ultrasonicprocess while its molecules were only transferred fromaqueous solution to the surface of Mn-modified diatomiteduring adsorption process As to the sonocatalytic degrada-tion involving catalyst and ultrasonic irradiation the removalwas attributed to both degradation and adsorption effects119870app values for ultrasonication catalyst adsorption and thecombined process were 122 times 10minus4 193 times 10minus3 and 453times 10minus3minminus1 respectively while corresponding 1198772 valueswere 0956 0986 and 0953 respectively 119870app value forthe combined process was 221 times the one of the sum of119870app values of the other two processes which indicated asignificant synergetic effect as well Meanwhile the degrada-tion efficiency of TC still increased continuously while theadsorption of TC almost achieved equilibriumwithin the firstseveral hours So it could be deduced that the removal ofTC in the combined process was mainly attributed to thedegradation rather than adsorption

UltrasonicationcatalystCatalyst adsorptionUltrasonication

10 20 30 40 50 600Time (min)

000

005

010

015

020

025

ln(C

0C

t)

Figure 5 Synergetic effect for the sonocatalytic degradation of TC(conditions catalyst dosage of 160mg in 200mL TC solution andTC concentration of 50mgL at neutral pH)

10 20 30 40 50 600Time (min)

000

005

010

015

020

025

030

ln(C

0C

t)

10 mg20 mg40mg

80 mg120 mg

Figure 6 Effect of catalyst dosage on the sonocatalytic degradationof TC (conditions TC concentration of 25mgL at neutral pH)

34 Effect of Catalyst Dosage The effect of catalyst dosageon the sonocatalytic degradation of TC was also investigatedas illustrated in Figure 6 The dosages of 10 20 40 80and 120mg in 200mL of solution with TC concentration of25mgL were selected It could be observed that 119870app valuesfor the dosages of 10 20 40 80 and 120mg were 000137000176 000299 000439 and 000517minminus1 respectivelywhile corresponding 1198772 values were 0962 0937 09360921 and 0938 respectively It could be confirmed that the


0

5

10

15

20

25

Rem

oval

effici

ency

()

10 20 30 40 50 600Time (min)

005 molL ISP0 molL ISP 01 molL ISP

001molL ISP

Figure 7 Effect of isopropanol (ISP) on the degradation of TC(conditions catalyst dosage of 60mg in 200mL TC solution and TCconcentration 15mgL at neutral pH and ISP dosages of 001 005and 01molL)

increased catalyst dosage enhanced the TC degradation obvi-ously from Figure 6 which was attributed to the increasedcatalyst sites on the modified diatomite

35 Oxidation Mechanism in the Process of TC Degradation351 Effect of Isopropanol on the TC Degradation Alcoholssuch as isopropanol could scavenge hydroxyl radicals andthey were often used as the quenchers of hydroxyl radicals(OH∙) to evaluate the production and contribution of thehydroxyl radicals [20 22 23] The inhibitive effect of iso-propanol on the oxidation processes could be indicated bythe decline in reaction rate constants As plotted in Figure 7the effect of isopropanol with different concentrations on thesonocatalytic degradation of TC was investigated Typicallythe degradation of TC was sharply decreased as a conse-quence of addition of isopropanol 119870app value in the absenceof isopropanol achieved 000548minminus1 while 1198772 value was0837 In contrast 119870app values at isopropanol dosages of001 005 and 01molL were 000269 000266 and 000239respectively while corresponding1198772 values were 0781 0822and 0819 respectively The presence of isopropanol with001 and 01molL reduced 119870app values by 515 and 572respectively As a series of ROSs such as OH∙ and H2O2were generated during the sonocatalytic process it could bededuced that OH∙ oxidation was absolutely dominant in thedegradation process

352 Effect of KBr on the TC Degradation As a compari-son the effect of KBr with different concentrations on thesonocatalytic degradation of TC was also investigated asillustrated in Figure 8 The degradation of TC was evenmore sharply decreased as a consequence of the addition ofKBr Similarly 119870app values at KBr dosages of 001 005 and01molL were 000238 000224 and 000197 respectively

10 20 30 40 50 600Time (min)

005 molL KBr0 molL KBr 01 molL KBr

001molL KBr

0

5

10

15

20

25

Rem

oval

effici

ency

()

Figure 8 Effect of KBr on the degradation of TC (conditions cata-lyst dosage of 60mg in 200mLTC solution and TC concentration of15mgL at neutral pH and KBr dosages of 001 005 and 01molL)

while corresponding 1198772 values were 0820 0843 and 0800respectively The presence of KBr at the concentration of001 and 01molL reduced 119870app values by 566 and 641respectively

In terms of sonochemical process alcohol is a knownOH∙radical scavenger for the gaseous region andor interfacialregion of the collapsing bubble However differently KBrwas known as a nonvolatile scavenger which could be readilyoxidized by free radicals These free radicals originated fromthe bulk liquid region and possibly were from the interfacialregion of the cavitation bubble [24 25] Accordingly almostall the free radicals could be quenched by KBr If the effectof OH∙ radicals was excluded from the total effect of freeradicals then the difference could be the contribution ofother radicals to the TC degradation which was 69 in thiscase It demonstrated the very limited effect of other oxidizingradical species in the experiment The strong oxidizingcapacity of OH∙ radicals was dominant in the sonocatalyticprocess

353 Effect of NaN3 on the TC Degradation Similarly azide(NaN3) was used as a quencher to scavenge singlet oxygen(1O2) The quenching effect has been a diagnostic tool forevaluating the roles of singlet oxygen [20 26] As shownin Figure 9 the addition of NaN3 actually quenched thedegradation considerably It was well accepted that photo-sensitized reactions of the first excited state O2(1Δ 119892) playeda key role in many natural photochemical and photobio-logical processes As ultrasonic irradiation was proven tobe capable of generating ultraviolet irradiation with wave-length below 375 nm [27 28] the Mn-modified diatomitewas deduced to be excited by the ultraviolet which wasregarded as photocatalytic process Accordingly singlet oxy-gen was definitely an active oxidizing species in sonocatalyticprocess


10 20 30 40 50 600Time (min)

002 molL azide

0 molL azide001molL azide

0

5

10

15

20

25

Rem

oval

effici

ency

()

Figure 9 Effect of azide on the degradation of TC (conditionscatalyst dosage of 60mg in 200mL TC solution and TC concentra-tion 15mgL at neutral pH and azide (NaN3) dosages of 001 and002molL)

Meanwhile 119870app values at azide dosages of 001 and002molL were of 000212 and 000217 respectively while1198772 values were 0856 and 0865 respectively The presenceof azide with concentrations of 001 and 002molL reduced119870app values by 613 and 604 respectively Based onthe above analysis it could be concluded that the reduc-tion trends of 119870app were quite close in the presence of01molL of isopropanol 001molL of KBr and 001molLof NaN3 This indicated that ROSs were absolutely dominantfor the degradation of TC The similar quenching effectswere reported by other researchers in photocatalytic andsonophotocatalytic degradation processes [29] indicatingthe probable photocatalytic oxidation process involved insonocatalytic process as well

354 Effect of Fe(II) on the TC Degradation The effect ofFe(II) a radical promoter was also investigated and demon-strated in Figure 10 Different from quenching effect additionof FeSO4sdot7H2Ocould enhance the sonochemical degradationof various organics whichwas proven by previous studies [2430ndash33] The sonocatalytic process was capable of generatingparticularly higher concentration of H2O2 compared toultrasonication alone [5] Due to the continuous generationof H2O2 in sonocatalytic process Fenton reaction is expectedto occur as follows

Fe2+ +H2O2 997888rarr Fe3+ +OH∙ +OHminus (7)

Fe3+ +H2O2 997888rarr FendashOOH2+ +H+ (8)

FendashOOH2+ 997888rarr Fe2+ +HOO∙ (9)

Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()

0mgL ferrous sulphate10 mgL ferrous sulphate

30mgL ferrous sulphate50mgL ferrous sulphate

Figure 10 Effect of Fe(II) on the degradation of TC (conditionscatalyst dosage of 60mg in 200mL TC solution and TC concentra-tion of 15mgL at neutral pH and FeSO4sdot7H2Odosages of 10 30 and50mgL)

A series of strong oxidants such as OH∙ are transformedconcurrently Similarly 119870app values at FeSO4sdot7H2O dosagesof 10 30 and 50mgL were 000559 000583 and 000655respectively while corresponding 1198772 values were 08230786 and 0800 respectively The presence of 50mgL ofFeSO4sdot7H2O enhanced 119870app value by 195 As a result theaddition of FeSO4sdot7H2O was beneficial for the degradationof TC

4 Conclusion

Mn-modified diatomite was prepared by wet impregnationand subsequent calcination The morphology and crystalstructure of the modified diatomite were not changed appar-ently compared to the raw diatomite Only 022 (atomicratio) of manganese was immobilized on 01molL MnSO4-modified diatomite even though theMn-modified diatomiteshowed particularly higher sonocatalytic activity than theraw diatomite by comparing their degradation performancefor tetracycline The increase in MnSO4 concentration usedin the wet impregnation solution and the catalyst dosageenhanced the degradation significantly The sonocatalyticprocess which combined ultrasonication and catalyst adsorp-tion demonstrated a significant synergetic effect The pres-ence of isopropanol KBr and NaN3 quenched a series ofreactive oxygen species sharply indicating the dominant roleof reactive oxygen species in the sonocatalytic process Incontrast the addition of Fe(II) could enhance the degradationof tetracycline as it facilitated the generation of more OH∙radicals

Competing Interests

The authors declare that there are no competing interests


Acknowledgments

The authors acknowledge the financial support by the Foun-dation for University Young Key Teacher Program of HenanProvince of China (no 2013GGJS-088) Science and Technol-ogy Research Project of Henan Province (no 152102210323)and the High-Level Talent Introduction Project in NorthChina University of Water Resources and Electric Power (no201002031)

References

[1] R Kidak and N H Ince ldquoUltrasonic destruction of phenol andsubstituted phenols a review of current researchrdquo UltrasonicsSonochemistry vol 13 no 3 pp 195ndash199 2006

[2] H Harada ldquoSonophotocatalytic decomposition of water usingTiO2 photocatalystrdquoUltrasonics Sonochemistry vol 8 no 1 pp55ndash58 2001

[3] H Nakui K Okitsu Y Maeda and R Nishimura ldquoEffect ofcoal ash on sonochemical degradation of phenol in waterrdquoUltrasonics Sonochemistry vol 14 no 2 pp 191ndash196 2007

[4] Y G Adewuyi ldquoSonochemistry in environmental remediation1 Combinative and hybrid sonophotochemical oxidation pro-cesses for the treatment of pollutants in waterrdquo EnvironmentalScience amp Technology vol 39 no 10 pp 3409ndash3420 2005

[5] H Zhao G M Zhang and Q L Zhang ldquoMnO2CeO2 forcatalytic ultrasonic degradation of methyl orangerdquo UltrasonicsSonochemistry vol 21 no 3 pp 991ndash996 2014

[6] K Thangavadivel K Okitsu G Owens P J Lesniewski and RNishimura ldquoInfluence of sonochemical reactor diameter andliquid height on methyl orange degradation under 200 kHzindirect sonicationrdquo Journal of Environmental Chemical Engi-neering vol 1 no 3 pp 275ndash280 2013

[7] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999

[8] J Peller O Wiest and P V Kamat ldquoHydroxyl radicalrsquos role inthe remediation of a common herbicide 24-dichlorophenox-yacetic acid (24-D)rdquo The Journal of Physical Chemistry A vol108 no 50 pp 10925ndash10933 2004

[9] N Ertugay and F N Acar ldquoThe degradation of Direct Blue 71 bysono photo and sonophotocatalytic oxidation in the presence ofZnOnanocatalystrdquoApplied Surface Science vol 318 pp 121ndash1262014

[10] Y Asakura M Maebayashi and S Koda ldquoStudy on efficiencyand characterization in a cylindrical sonochemical reactorrdquoJournal of Chemical Engineering of Japan vol 38 no 12 pp1008ndash1014 2005

[11] L M Song C Chen and S J Zhang ldquoSonocatalytic perfor-mance of Tb7O12TiO2 composite under ultrasonic irradiationrdquoUltrasonics Sonochemistry vol 18 no 3 pp 713ndash717 2011

[12] J Wang Z Jiang Z Zhang et al ldquoSonocatalytic degradationof acid red B and rhodamine B catalyzed by nano-sized ZnOpowder under ultrasonic irradiationrdquo Ultrasonics Sonochem-istry vol 15 no 5 pp 768ndash774 2008

[13] G Li R Gao B Wang Z Wu S Ma and Y Zhang ldquoSynergeticeffect for diatomite-catalysed sono-catalytic degradation ofmethylene bluerdquo Journal of the Chinese Ceramic Society vol 43no 4 pp 488ndash492 2015 (Chinese)

[14] M Al-Ghouti M A M Khraisheh M N M Ahmad andS Allen ldquoThermodynamic behaviour and the effect of tem-perature on the removal of dyes from aqueous solution using

modified diatomite a kinetic studyrdquo Journal of Colloid andInterface Science vol 287 no 1 pp 6ndash13 2005

[15] J Ge and J Qu ldquoDegradation of azo dye acid red B onmanganese dioxide in the absence and presence of ultrasonicirradiationrdquo Journal of Hazardous Materials vol 100 no 1ndash3pp 197ndash207 2003

[16] E V Rokhina K Makarova M Lahtinen E A Golovina HVan As and J Virkutyte ldquoUltrasound-assisted MnO2 catalyzedhomolysis of peracetic acid for phenol degradation the assess-ment of process chemistry and kineticsrdquo Chemical EngineeringJournal vol 221 pp 476ndash486 2013

[17] S Kim P Eichhorn J N Jensen A S Weber and D S AgaldquoRemoval of antibiotics in wastewater effect of hydraulic andsolid retention times on the fate of tetracycline in the activatedsludge processrdquoEnvironmental ScienceampTechnology vol 39 no15 pp 5816ndash5823 2005

[18] T Polubesova D Zadaka L Groisman and S Nir ldquoWaterremediation by micelle-clay system case study for tetracyclineand sulfonamide antibioticsrdquoWater Research vol 40 no 12 pp2369ndash2374 2006

[19] R A Figueroa A Leonard and A A Mackay ldquoModelingtetracycline antibiotic sorption to claysrdquo Environmental Scienceamp Technology vol 38 no 2 pp 476ndash483 2004

[20] G Li K HWong X Zhang et al ldquoDegradation of AcidOrange7 usingmagnetic AgBr under visible light the roles of oxidizingspeciesrdquo Chemosphere vol 76 no 9 pp 1185ndash1191 2009

[21] Jaidev R I Jafri A K Mishra and S Ramaprabhu ldquoPolyani-line-MnO2 nanotube hybrid nanocomposite as supercapacitorelectrode material in acidic electrolyterdquo Journal of MaterialsChemistry vol 21 no 44 pp 17601ndash17605 2011

[22] G Li M Zhu J Chen Y Li and X Zhang ldquoProduction andcontribution of hydroxyl radicals between the DSA anode andwater interfacerdquo Journal of Environmental Sciences vol 23 no5 pp 744ndash748 2011

[23] X Zhang D D Sun G Li and Y Wang ldquoInvestigation ofthe roles of active oxygen species in photodegradation of azodye AO7 in TiO2 photocatalysis illuminated by microwaveelectrodeless lamprdquo Journal of Photochemistry and PhotobiologyA Chemistry vol 199 no 2-3 pp 311ndash315 2008

[24] E Manousaki E Psillakis N Kalogerakis and DMantzavinosldquoDegradation of sodium dodecylbenzene sulfonate in water byultrasonic irradiationrdquoWater Research vol 38 no 17 pp 3751ndash3759 2004

[25] D GWayment and D J Casadonte Jr ldquoFrequency effect on thesonochemical remediation of alachlorrdquo Ultrasonics Sonochem-istry vol 9 no 5 pp 251ndash257 2002

[26] C Schweitzer and R Schmidt ldquoPhysical mechanisms of genera-tion and deactivation of singlet oxygenrdquo Chemical Reviews vol103 no 5 pp 1685ndash1758 2003

[27] C Berberidou I Poulios N P Xekoukoulotakis and DMantzavinos ldquoSonolytic photocatalytic and sonophotocat-alytic degradation of malachite green in aqueous solutionsrdquoApplied Catalysis B Environmental vol 74 no 1-2 pp 63ndash722007

[28] L H Thompson and L K Doraiswamy ldquoSonochemistryscience and engineeringrdquo Industrial amp Engineering ChemistryResearch vol 38 no 4 pp 1215ndash1249 1999

[29] S K Kavitha and P N Palanisamy ldquoPhotocatalytic andsonophotocatalytic degradation of reactive red 120 using dyesensitized Tio2 under visible lightrdquo World Academy of ScienceEngineering and Technology vol 73 pp 1ndash6 2011


[30] X Wang Z Yao J Wang W Guo and G Li ldquoDegradationof reactive brilliant red in aqueous solution by ultrasoniccavitationrdquo Ultrasonics Sonochemistry vol 15 no 1 pp 43ndash482008

[31] B Yim Y Yoo and Y Maeda ldquoSonolysis of alkylphenols inaqueous solution with Fe(II) and Fe(III)rdquo Chemosphere vol 50no 8 pp 1015ndash1023 2003

[32] M A Beckett and I Hua ldquoEnhanced sonochemical decompo-sition of 1 4-dioxane by ferrous ironrdquo Water Resources vol 37pp 2372ndash2376 2003

[33] G Shankaraiah P SarithaNV PedamallaD Bhagawan andVHimabindu ldquoDegradation of Rabeprazole-N-oxide in aqueoussolution using sonication as an advanced oxidation processrdquoJournal of Environmental Chemical Engineering vol 2 no 1 pp510ndash515 2014

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CatalystsJournal of


porosity high permeability large surface area and chemicalinertness [14] Meanwhile Mn oxides were proven to be anexcellent catalyst under ultrasonic irradiation as well [15 16]The combination of diatomite with Mn oxides might furtherenhance the sonochemical degradation efficiency due to thepossible synergetic effect In this research manganese oxideswere immobilized onto natural diatomite by wet impreg-nation and subsequent calcinations processes The compos-ite of manganese oxides and diatomite was used for thesonochemical degradation of organic pollutants to evaluatesonocatalytic performance

Tetracyclines are the secondmost widely used antimicro-bial chemicals globally which are widely applied in humantherapy and livestock industry [17] As tetracyclinemoleculesare usually neutral or negatively charged in environmen-tal water conventional techniques such as sand filtrationsedimentation flocculation and coagulation are not veryefficient for tetracycline removal as expected [18] As a resulttetracycline was selected as a target organic pollutant forthe sonocatalytic process in this study Additionally themechanism for the enhanced degradation performance ofsonocatalytic process has not yet been reported in detailHence the oxidation mechanism was indirectly evaluatedby adding scavengers such as isopropanol NaN3 and KBrrespectively The effect of radical promoter Fe(II) was alsoinvestigated concurrently

2 Materials and Methods

21 Materials Tetracycline (TC) was purchased from HefeiBomei Biological Science and Technology Co Ltd (Anhuiprovince China) and it was used without further purifica-tion Diatomite was provided by Linjiang Meston PowderyMaterials Co Ltd (Jilin province China) Other chemicalsused were of analytical grade Deionized (DI) water was usedto prepare all solutions

22 Preparation of Mn-Modified Diatomite A series ofMnSO4 solutions with a concentration gradient of 001 005010 050 and 10molL were used for the wet impregna-tion of the raw diatomite The diatomitesolution ratio was1 g10mLThemixture of diatomite andMnSO4 solution wasagitated in an orbital shaker at 140 rpmand room temperaturefor 24 h The modified diatomite was collected by filtrationand dried at 100∘C overnight Finally the raw diatomite andtreated diatomite were calcined at 500∘C for 2 hThe prepared010molL MnSO4-modified diatomite is denoted as Mn-modified diatomite

23 Characterization The morphologies of raw diatomiteand the Mn-modified diatomite were recorded on a PhilipsQuanta-2000 scanning microscope coupled with an energydispersive X-ray (EDX) spectrometerTheir X-ray diffraction(XRD) patterns were recorded on a Rigaku DMAX-3B X-diffractometer FTIR spectra (KBr pellets) were recorded ona Nicolet NEXUS 470 FTIR spectrophotometer from 400 to4000 cmminus1

24 Sonocatalytic Degradation of TC by Mn-Modified Dia-tomite Degradation of TC was carried out in a beaker for60min The available volume of the beaker was 250mL and200mL of TC solution was added Sonication was performedin a 40 kHz ultrasonic cleaning bath (AS3120A KunshanUltrasonic Instruments Co Jiangsu China) The power ofthe ultrasonic cleaning bath was 50W The water-circulatingunit was used to control water bath temperature

25 Analyses Samples were collected and filtered through a045 120583m membrane before analyzing The concentration ofTC was determined by measuring the maximum absorbanceat a fixed wavelength (360 nm) [19] using an UVmini-1240spectrophotometer (Shimadzu Japan)

The removal efficiency of TC was calculated as

removal efficiency = (1 minus 1198621199051198620) times 100 (5)

The pseudo-first-order kinetics for TC degradation wassimulated as [20]

ln(1198620119862119905 ) = 119870app119905 (6)

where 119862119905 is the TC concentration at time 119905 1198620 is the initialTC concentration and 119870app is the apparent first-order rateconstant

3 Results and Discussion

31 Characterization of Mn-Modified Diatomite The rawdiatomite used was comprised of the discoid plates like lotushead and fragments of these plates Most of the discoid plateswere in the range of 5ndash50120583m These data had been referredto in our previous study [13] As illustrated in Figure 1(a) forthe Mn-modified diatomite there was no significant changein the morphologies after the modification The content ofmanganese element was found to be about 022 (atomicratio) by EDX analysis as presented in Figure 1(b) Thisindicated that only a very limited amount of Mn oxides wasimmobilized onto the diatomite

The XRD patterns of the raw diatomite and the used Mn-modified diatomite were examined and presented in Figure 2The strong and broad peak at 2120579 = 218∘ was related to thediffraction peak of cristobalite (JCPDS number 39-1425)while the weak peak at 2120579 = 266∘ was attributed to quartz(JCPDS number 46-1045) Both the two peaks were themajor characteristic peaks of diatomite Apparently the XRDpatterns of the Mn-modified diatomite were almost identicalto those of the raw one This result demonstrated that thestructure of diatomite was not significantly changed after themodification

The FTIR spectra of the raw diatomite the Mn-modified diatomite and the used Mn-modified diatomitewere recorded in Figure 3 respectively As the content ofsilicon element was found to be about 3334 (atomic ratio)by EDX analysis the absorption bands at 465 and 800 cmminus1were evidently ascribed to the vibrations of SindashO group


(a)

O

C MgAl

Si

AuAuMn

200

800

100

500

600

700

300

900

400

1100

1200

1000

1300

Energy (keV)

00

12

23KCnt

35

46

58

(b)



b

Inte

nsity

(au

)

a

20 30 40 50 60102120579 (degree)




800

465

556

616

724

c

b

Tran

smitt

ance

a





000

008

016

024

032

ln(C

0C

t)

10 20 30 40 50 600Time (min)

0molL MnSO4

10 molL MnSmolL MnS

O4

05 O4

01 molL MnSO4

005 molL MnSO4

001 molL MnSO4





10 20 30 40 50 600Time (min)

000

005

010

015

020

025

ln(C

0C

t)


10 20 30 40 50 600Time (min)

000

005

010

015

020

025

030

ln(C

0C

t)

10 mg20 mg40mg

80 mg120 mg




0

5

10

15

20

25

Rem

oval

effici

ency

()

10 20 30 40 50 600Time (min)


001molL ISP





10 20 30 40 50 600Time (min)


001molL KBr

0

5

10

15

20

25

Rem

oval

effici

ency

()






10 20 30 40 50 600Time (min)

002 molL azide


0

5

10

15

20

25

Rem

oval

effici

ency

()







Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()





4 Conclusion


Competing Interests



Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a)

O

C MgAl

Si

AuAuMn

200

800

100

500

600

700

300

900

400

1100

1200

1000

1300

Energy (keV)

00

12

23KCnt

35

46

58

(b)



b

Inte

nsity

(au

)

a

20 30 40 50 60102120579 (degree)




800

465

556

616

724

c

b

Tran

smitt

ance

a





000

008

016

024

032

ln(C

0C

t)

10 20 30 40 50 600Time (min)

0molL MnSO4

10 molL MnSmolL MnS

O4

05 O4

01 molL MnSO4

005 molL MnSO4

001 molL MnSO4





10 20 30 40 50 600Time (min)

000

005

010

015

020

025

ln(C

0C

t)


10 20 30 40 50 600Time (min)

000

005

010

015

020

025

030

ln(C

0C

t)

10 mg20 mg40mg

80 mg120 mg




0

5

10

15

20

25

Rem

oval

effici

ency

()

10 20 30 40 50 600Time (min)


001molL ISP





10 20 30 40 50 600Time (min)


001molL KBr

0

5

10

15

20

25

Rem

oval

effici

ency

()






10 20 30 40 50 600Time (min)

002 molL azide


0

5

10

15

20

25

Rem

oval

effici

ency

()







Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()





4 Conclusion


Competing Interests



Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


000

008

016

024

032

ln(C

0C

t)

10 20 30 40 50 600Time (min)

0molL MnSO4

10 molL MnSmolL MnS

O4

05 O4

01 molL MnSO4

005 molL MnSO4

001 molL MnSO4





10 20 30 40 50 600Time (min)

000

005

010

015

020

025

ln(C

0C

t)


10 20 30 40 50 600Time (min)

000

005

010

015

020

025

030

ln(C

0C

t)

10 mg20 mg40mg

80 mg120 mg




0

5

10

15

20

25

Rem

oval

effici

ency

()

10 20 30 40 50 600Time (min)


001molL ISP





10 20 30 40 50 600Time (min)


001molL KBr

0

5

10

15

20

25

Rem

oval

effici

ency

()






10 20 30 40 50 600Time (min)

002 molL azide


0

5

10

15

20

25

Rem

oval

effici

ency

()







Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()





4 Conclusion


Competing Interests



Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

5

10

15

20

25

Rem

oval

effici

ency

()

10 20 30 40 50 600Time (min)


001molL ISP





10 20 30 40 50 600Time (min)


001molL KBr

0

5

10

15

20

25

Rem

oval

effici

ency

()






10 20 30 40 50 600Time (min)

002 molL azide


0

5

10

15

20

25

Rem

oval

effici

ency

()







Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()





4 Conclusion


Competing Interests



Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10 20 30 40 50 600Time (min)

002 molL azide


0

5

10

15

20

25

Rem

oval

effici

ency

()







Fe3+ +HOO∙ 997888rarr Fe2+ +O2 +H+ (10)

10 20 30 40 50 600Time (min)

0

5

10

15

20

25

30

Rem

oval

effici

ency

()





4 Conclusion


Competing Interests



Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Acknowledgments


References













































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

sonocatalytic degradation of antibiotics tetracycline by mn...

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