Research ArticleStudy on the Degradation of Sodium Diethyldithiocarbamate(DDTC) in Artificially Prepared Beneficiation Wastewater withSodium Hypochlorite

Baoyu Cui , Xuetao Wang, Qiang Zhao, and Wengang Liu

School of Resources & Civil Engineering, Northeastern University, Shenyang 110819, China

Correspondence should be addressed to Baoyu Cui; cuibaoyu@mail.neu.edu.cn

Received 12 January 2019; Revised 3 March 2019; Accepted 19 March 2019; Published 4 April 2019

Academic Editor: Tingyue Gu

Copyright © 2019 Baoyu Cui et al. 'is is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

'e degradation of DDTC in beneficiation wastewater has become an increasingly concerned issue due to the serious effects on theenvironment. In this study, the degradation characteristics of DDTC in artificially prepared beneficiation wastewater wereinvestigated by adding sodium hypochlorite as an oxidant, and the influences of different degradation conditions on removalefficiency of DDTC were analyzed systematically. 'e results indicated that the degradation rate of DDTC without sodiumhypochlorite added can reach 88.4% in a stewing time of 6 h. When the dosage of sodium hypochlorite was 400mg·L−1, thedegradation rate of DDTC can reach 91.28% for 1min reaction time under the natural condition of pH value 5.98 and reactiontemperature 25°C. 'e DDTC in the wastewater was firstly degraded into carbon disulfide and diethylamine, and then carbondisulfide was further degraded into CO2, S, or SO4

2−, while diethylamine was degraded into N2 and CO2. 'e research results canprovide a technical basis for the treatment of beneficiation wastewater containing DDTC.

1. Introduction

Flotation is one of the most important methods of mineralprocessing. With the difficulties of infertility and fineness ofore resources, the flotation processing has become extremelycomplex. And thus, the variety and dosage of flotation re-agents used are increasing dramatically [1–4]. DDTC((C2H5)2NCSSNa), as a typical collector reagent of flotationfor sulfide ore, has superior ability of collection, good se-lectivity, and other advantaged performances, and it hasbeen widely used in the flotation process of galena, chal-copyrite, jamesonite, and other minerals [5, 6]. Generally,the DDTC presents the instability in acidic condition as theaqueous solution of DDTC is alkaline. 'erefore, the ap-plications of DDTC centralized more extensively in alkalineconditions [7]. In addition, it is able to obtain a betterflotation technical index contributed by the good adapt-ability of DDTC to the various characteristics of ore, evenwith the lower dosage [8–10]. In the condition of high al-kalinity, the DDTC can obviously improve the separation

performance of lead-zinc sulfide ore, by using less or no toxicsodium cyanide [11, 12].

In recent years, the treatment of beneficiation waste-water, especially the wastewater containing organic chem-icals, is getting notable attention as a contribution toprotecting the environment [13–15]. 'e technical index ofseparation in the whole process will decline when thebeneficiation wastewater containing DDTC is reused di-rectly without special treatment [16, 17]. Direct discharge ofbeneficiation wastewater containing DDTC also brings se-rious damage to the environment [12, 17]. At present, themethods of wastewater treatment containing DDTC mainlyinclude natural degradation, coagulation sedimentation,acid-base neutralization, chemical oxidation, and bio-degradation [12, 16–25]. 'e natural degradation is one ofthe most primitive methods of treating beneficiationwastewater. 'e advantages of this method are simple op-eration and low cost, and the disadvantages are long time-consuming, unstable effluent quality, and large floor space[12, 16, 17]. 'e method of acid-base neutralization not only

HindawiJournal of ChemistryVolume 2019, Article ID 7038015, 8 pageshttps://doi.org/10.1155/2019/7038015

has the same advantages of natural degradation but it isnecessary to provide the available waste in acidic or alkalinenearby, which can achieve the strategy of treating waste bywaste [17–19]. 'e method of coagulation sedimentationutilizes coagulants to degrade organic and inorganic con-taminants within beneficiation wastewater in the form ofsuspension or colloid, even some soluble pollutants andheavy metal ions can also be degraded. 'is method has theadvantages of simplification of process, various selectivityfor coagulants, and high rate of sedimentation but also hasthe disadvantages of large dosage of coagulants, exceedingamount of slags, and limitation of treating residual chem-icals of low concentration, and secondary pollution of theslags is the biggest obstacle to its development [12, 20, 21].Biodegradation, as a focused direction studied methodcurrently, makes use of microorganisms to degrade organicpollutants while adsorbing and degrading heavy metals inwastewater. 'is method is characterized by low cost and nosecondary pollution, while with the disadvantages of largeequipment investments, high operation requirements, andpoor adaptability. It is only suitable for wastewater treatmentwith low concentrations of organic pollutants[12, 15, 19–21]. Chemical oxidation is an effective method toremove organic pollutants from wastewater, with the ad-vantages of variety of oxidants, rapidity of reaction, andgood quality of effluent which make it be one of the mostwidely used methods for treating residual chemical reagentsin beneficiation wastewater, meanwhile with the disadvan-tages of large dosage of oxidants and relatively high cost[12, 21–25]. In conclusion, chemical oxidation is the mostappropriate method for the treatment of the beneficiationwastewater which is of large capacity and complicatedcomposition, with the requirements of stability and rapidityof reusing. Research shows that common oxidants such asozone, hydrogen peroxide, potassium ferrate, and hypo-chlorite all can be used in the processing of chemical oxi-dative degradation of DDTC; a simple comparison of theseoxidants is shown in Table 1 [22–25].

Meanwhile, it can be seen that researches of chemicaloxidative degradation of DDTC mostly focus on the theo-retical field, and there are only a few studies on the deg-radation of DDTC in true beneficiation wastewater or inwastewater similar to the beneficiation wastewater. In thispaper, degradation behavior and products of DDTC inartificially prepared beneficiation wastewater were in-vestigated, with sodium hypochlorite selected as an oxidantdue to the advantages listed and the low impact of residualchlorine on the flotation process [26]. Correspondingly, theinvestigation is to further reveal the mechanism of oxidativedegradation of DDTC and provide a technical basis for thetreatment of beneficiation wastewater containing DDTC.

2. Experimental

2.1. Reagents andMaterials. DDTC ((C2H5)2NCSSNa·3H2O)was obtained from Guoan Chemical Reagent Co., Ltd.(China), and it was prepared for the artificial beneficiationwastewater. Sodium hydroxide (NaOH) and hydrochloricacid (HCl) were selected as the pH regulators, sodium

hypochlorite (NaClO) was selected as the oxidant for en-hancing the degradation property of DDTC, and these threekinds of reagents were all manufactured by Tianjin KermelChemical Reagent Co., Ltd. (China). Sodium sulfate(Na2SO4) was from Sinopharm Chemical Chemical ReagentCo., Ltd. (China). All the above reagents were analyticallypure.

Sodium n-butylxanthate (C4H9OCSSNa) and terpenicoil (C10H17OH) were of technical grade and manufacturedby Tieling Flotation Regent Co., Ltd. (China); they wereauxiliary reagents for the artificially prepared beneficiationwastewater.

2.2. Experimental Methods

2.2.1. Reagents Concentration Test. 'e concentration ofDDTC in artificial prepared beneficiation wastewater wastested by using a UV spectrophotometer (SP-2000, ShanghaiSpectrum Instrument Co., Ltd., China). 'e DDTC solutionof 20mg·L−1 was spectrally scanned to search the strongestabsorption peak. 'en, DDTC solutions of different con-centrations were prepared for separately measuring theabsorbance in matching the strongest absorption peak. Andthus, the standard curve of working of DDTC could beobtained between the concentration and the absorbance.

'e contents of COD (chemical oxygen demand), TOC(total organic carbon), and sulfide in the beneficiationwastewater were analyzed by the Analysis and TestingAgency of Northeastern University, China. Further, mi-crowave digestion method, Vario TOC cube (ElementarAnalysensysteme GmbH, Germany), and methylene bluespectrophotometry method were applied, respectively.'esemethods of tests were not described in detail in this study,and works of literature had made them quite clear [25, 26].

2.2.2. Degradation Process Investigation. 'e artificiallyprepared beneficiation wastewater, with several copies of each50mL in the laboratory, was stirred continuously in a heatingmagnetic stirrer for 30min (SH-3A, Beijing Jinbeide In-dustrial Co., Ltd., China). 'en, the absorbance in matchingthe strongest absorption peak was measured by using a UVspectrophotometer in the condition that the wastewater wasdiluted 5 times after stirring. Also, the degradation rate ofDDTC was calculated to explore the influences of the pHvalue, reaction temperature, dosage of sodium hypochlorite,and the reaction time on degradation efficiency. With thedegradation cost being taken into account, the degradationinvestigation of DDTC in artificially prepared beneficiationwastewater would be conducted as much as possible in thenormal temperature and natural pH value conditions.

2.2.3. Degradation Products Analysis. 'e wastewater wasalso diluted 5 times after reaction and then scanned by usinga UV spectrophotometer including the solution before re-action. 'e degradation pathway and products of DDTCwere analyzed by comparing UV spectra before and after thereaction. During the analysis of the degradation products,

2 Journal of Chemistry

the UV spectrophotometer worked on the condition of ascanning wavelength from 190 nm to 400 nm and an intervalof 1 nm at a medium speed.

2.2.4. Degradation Rate Calculation. �e degradation rate ofDDTC was calculated as follows:

degradation rate �C0 −CC0

× 100%, (1)

where C0 (mg·L−1) is the initial concentration of DDTC andC (mg·L−1) is the residual concentration of DDTC aftertreatment in wastewater.

2.3. Standard Curve of Working of DDTC Solution. �estandard solution of DDTC with concentration of100mg·L−1 was scanned by using a UV spectrophotometer,and the results are shown in Figure 1.

It is presented in Figure 1 that there were three UVabsorption peaks at 202 nm, 256 nm, and 282 nm in thesolution of DDTC. �e maximum absorption peak was at256 nm, which was selected as the characteristic absorptionwavelength of DDTC solution.

Separately, we had taken 2mL, 5mL, 10mL, 20mL, and25mL of standard solution of DDTC with concentration of100mg·L−1, put into �ve volumetric �asks of 100mL, anddiluted with water to the scale line.�e tests of absorbance at256 nmwavelength of each solution were conducted, and thestandard curve of working corresponding to the DDTCconcentration is shown in Figure 2. Furthermore, the linearequation between absorbance (Y) and solution concentra-tion (X) is as follows:

Y � 0.04577X + 0.026,

R2 � 0.9993.(2)

3. Results and Discussion

3.1. Preparation of Arti�cial Bene�ciation Wastewater. In aconcentration plant of lead-zinc, the process of lead-zincseparation after bulk �otation was adopted. Calcium oxidewas selected as the pH regulator, DDTC and sodium n-

butylxanthate were used as collectors, terpenic oil wasemployed as frother, and zinc sulfate and copper sulfate wereemployed as inhibitors and activators of sphalerite, re-spectively.�e test results of wastewater discharged from theover�ow of the thickener treating �nal tailings are shown inTable 2. It is noteworthy that the natural pH value of the

202

282256

0.0

0.2

0.4

0.6

0.8

1.0

Abso

rban

ce

180 200 220 240 260 280 300 320 340160Wavelength (nm)

Figure 1: UV absorption spectrum of DDTC.

Y = 0.04577X + 0.026R2 = 0.9993

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Abso

rban

ce at

256

nm w

avele

ngth

5 10 15 20 250Concentration (mg·L–1)

Figure 2: Standard curve of working of DDTC solution.

Table 1: Simple comparison of common oxidants.

Oxidants Advantages Disadvantages Applicable

Ozone Strong oxidizing ability, no otherreaction by-products.

High equipment cost, toxic whenhigh concentration.

Mainly used as supplement for otherwater treatment methods

Hydrogenperoxide

Strong oxidizing ability, widerange of application.

Preparation and storage process of thereagent is complicated, high

treatment cost.

Suitable for the treatment of lowconcentration and small capacity ofwastewater, used as a pretreatment or

advanced treatment method forrefractory organic wastewater.

Potassiumferrate

Extremely strong oxidizingability, minor secondary pollution,

quick reaction.

Relatively high cost of reagent,high requirement of storage

environment.

A novel method of wastewatertreatment, the �occulation

performance of reduction product ofFe3+ or Fe(OH)3 can a�ect the

bene�ciation process.

Hypochlorite Easy to use, low cost, widerange of application.

High requirement ofstorage environment.

�e most commonly used method ofwastewater treatment.

Journal of Chemistry 3

bene�ciation wastewater was 5.98 rather than alkaline. Fromthe analysis of TOC and content of DDTC, it was clear thatthe bene�ciation wastewater was a mixture of DDTC andother organic pollutants. Furthermore, it could be inferredthat a certain amount of sodium n-butylxanthate and ter-penic oil were mixed from the reagent system of �otation.

In order to study the degradation process and productsof DDTC more accurately in the laboratory and to avoid thein�uences of some uncertain factors, the arti�cial �otationwastewater was prepared according to the analysis results ofbene�ciation wastewater, with the concentration of DDTC100mg·L−1, sodium sulfate 133mg·L−1, sodium n-butyl-xanthate 20mg·L−1, terpenic oil 10mg·L−1, and sodiumsul�de 0.5mg·L−1, respectively.

3.2. Degradation Characteristics of DDTC without SodiumHypochlorite. In order to explore the ability of naturaldegradation of DDTC without oxidant to achieve the rapidrecycling of wastewater or not, the degradation of DDTC inarti�cially prepared bene�ciation wastewater was in-vestigated systematically by changing the pH value, stewingtime, and reaction temperature.

3.2.1. In�uence of the pH Value on the Degradation of DDTC.�e pH value of arti�cially prepared bene�ciation waste-water was adjusted by NaOH or HCl under the condition ofstewing time 1 h and reaction temperature 25°C. �e resultsof degradation characteristics of DDTC in arti�cially pre-pared wastewater of �otation under di�erent pH values areshown in Figure 3.

From Figure 3, the degradation of DDTC was almostconstant at the beginning, with the increase of the pH valueof the wastewater; the degradation property of DDTC �rstlydecreased linearly and then tended to be stable. When thepH value was 2.5, the degradation rate of DDTC reached upto 99.95%, and when the pH value increased to 4, thedegradation rate was 99.91%.With the further increase of thepH value of the wastewater, the degradation rate of DDTCdecreased sharply. When the pH value was 7, the degra-dation rate of DDTCwas just 15.88%. And then, with the pHvalue continuing to increase, the concentration of DDTCalmost remained stable. When the pH value of wastewaterwas 11, the degradation rate of DDTCwas just 12.38%.�us,the DDTC was extremely unstable in the acidic environ-ment, but it was relatively stable in the neutral or alkalineenvironment.

3.2.2. In�uence of Stewing Time on the Degradation of DDTC.Under the condition of pH value 5.98 and reaction temper-ature 25°C, the e�ect of stewing time on the degradation ofDDTC in arti�cially prepared bene�ciation wastewater was

investigated, correspondingly the results are shown inFigure 4.

Figure 4 presents that, with the extension of stewingtime, the concentration of DDTC in wastewater decreasedgradually. �e concentration of DDTC decreased rapidlywhen the stewing time changed from 1 h to 3 h, then de-creased slowly. When the stewing time was 6 h, the con-centration of DDTC in wastewater could reach to11.60mg·L−1, with the degradation rate of 88.4%. However,hours of stewing time were unable to achieve the timelyreuse of the bene�ciation wastewater.

3.2.3. In�uence of Reaction Temperature on the Degradationof DDTC. Under the condition of pH value 5.98 and stewingtime 1 h, the e�ect of reaction temperature on the degra-dation of DDTC in arti�cially prepared bene�ciationwastewater was investigated, and the results are shown inFigure 5.

It can be seen from Figure 5 that the degradation ofDDTC basically followed the Arrhenius equation when thereaction temperature ranged from 25°C to 65°C, corre-spondingly the degradation rate of DDTC increased from30.00% to 66.68%. �en, when the temperature increasedfrom 65°C to 75°C, the degradation rate of DDTC rocketedby 31.79% and up to 98.47%, but such high temperature wasmeaningless for the natural degradation of DDTC.

3.3. Characteristics of Degradation of DDTC with SodiumHypochlorite. �e ability of natural degradation of DDTCwithout oxidant cannot generally satisfy the timely reuse ofthe bene�ciation wastewater. Due to the advantages of so-dium hypochlorite and low impact of residual chlorine onthe �otation process, sodium hypochlorite was added toaccelerate the degradation of DDTC. �e in�uences of thedosage of sodium hypochlorite, reaction time, and reactiontemperature on the degradation of DDTC were investigatedsystematically, where the initial pH value of 5.98 wasmaintained according to the true bene�ciation wastewaterbefore sodium hypochlorite added.

Table 2: Analysis results of the true bene�ciation wastewater.

pH valueContent (mg·L−1)

COD TOC DDTC SO42− Sulphide

5.98 267 139.55 93.75 87.43 0.49

DDTC concentrationDegradation rate

0

20

40

60

80

100

DD

TC co

ncen

trat

ion

(mg·

L–1)

4 6 8 102pH value

0

20

40

60

80

100

Deg

rada

tion

rate

(%)

Figure 3: In�uence of the pH value on the degradation of DDTC.

4 Journal of Chemistry

3.3.1. In�uence of the Dosage of Sodium Hypochlorite on theDegradation of DDTC. Under the condition of pH value5.98, reaction time 1min, and temperature 25°C, the e�ect ofthe dosage of sodium hypochlorite on the degradation ofDDTC in arti�cially prepared bene�ciation wastewater wasinvestigated, and the results are shown in Figure 6.

It can be seen from Figure 6 that the degradation rate ofDDTC increased obviously, with the increase of the dosageof sodium hypochlorite in the scope of experiments. Whenthe dosage of sodium hypochlorite increased from 10mg·L−1to 100mg·L−1, the degradation rate increased from 37.95%to 68.32% with an approximate linear upward trend. Whenthe dosage ranged from 100mg·L−1 to 400mg·L−1, thedegradation rate increased from 68.32% to 91.38%, showinga similar linear relationship presented before, but the up-ward slope of the curve became smaller than the previous

stage. �en, the dosage of sodium hypochlorite had a lesse�ect on the degradation of DDTC even when the dosagecontinuously increased.

3.3.2. In�uence of Reaction Time on the Degradation ofDDTC with Sodium Hypochlorite. Under the condition ofpH value 5.98, the dosage of sodium hypochlorite of400mg·L−1, and reaction temperature 25°C, the in�uence ofthe reaction time on the degradation of DDTC in arti�ciallyprepared bene�ciation wastewater was investigated, asshown in Figure 7.

As is presented in Figure 7, the curve of degradation rateof DDTC was divided into 3 stages with the extension of thereaction time. �e �rst stage was from 1min to 5min, andthe concentration of DDTC decreased rapidly, while thedegradation rate increased rapidly from 91.28% to 99.29%.�e second stage was from 5min to 7min, and the con-centration of DDTC in wastewater remained about the sameas that of the �rst stage. �e third stage was from 7min to11min, and the concentration of DDTC increased slightly.�e reason for the phenomenon above may be that, with theincrease of oxidation time, further degradation of DDTC orits products occurred and that some substances with ab-sorbance at the wavelength of 256 nm were generated.Further research is needed to validate the hypothesis.

3.3.3. In�uence of Reaction Temperature on the Degradationof DDTC with Sodium Hypochlorite. Under the condition ofpH value 5.98, dosage of sodium hypochlorite 400mg·L−1,and reaction time 1min, the in�uence of reaction temper-ature on the degradation of DDTC in arti�cially preparedbene�ciation wastewater was investigated, as shown inFigure 8.

From Figure 8, the degradation rate of DDTC increasedwith the increase of temperature. Further, when the tem-perature ranged from 25°C to 55°C, the degradation rate ofDDTC was approximately linearly dependent on the

DDTC concentrationDegradation rate

0

10

20

30

40

50

60

70

80

DD

TC co

ncen

trat

ion

(mg·

L–1)

30 40 50 60 70 8020Temperature (°C)

20

30

40

50

60

70

80

90

100

Deg

rada

tion

rate

(%)

Figure 5: In�uence of the temperature on the degradation ofDDTC.

DDTC concentrationDegradation rate

0

10

20

30

40

50

60

70

DD

TC co

ncen

trat

ion

(mg·

L–1)

30

40

50

60

70

80

90

Deg

rada

tion

rate

(%)

100 200 300 400 5000Sodium hypochlorite dosage (mg·L–1)

Figure 6: In�uence of the dosage of sodium hypochlorite on thedegradation of DDTC.

DDTC concentrationDegradation rate

0

10

20

30

40

50

60

70

DD

TC co

ncen

trat

ion

(mg·

L–1)

2 3 4 5 61Time (h)

30

40

50

60

70

80

90

100

Deg

rada

tion

rate

(%)

Figure 4: In�uence of the stewing time on the degradation ofDDTC.

Journal of Chemistry 5

temperature. �e degradation rate of DDTC at 55°C reachedas high as 99.13%, and DDTC almost completely degraded.

3.4. Degradation Products of DDTC

3.4.1. Degradation Products of DDTC without SodiumHypochlorite. Under the natural conditions of pH value 5.98and reaction temperature 25°C, the degradation products ofDDTC were investigated without sodium hypochlorite. �escanning results of UV spectrophotometry of each reactionsolution at di�erent stewing time periods are shown inFigure 9.

From Figure 9, with the increase of stewing time, theabsorption peak of arti�cially prepared bene�ciationwastewater gradually decreased at the wavelength of 256 nmand 282 nm, which meant that the degradation of DDTCgradually occurred. And, a new strong absorption peakappeared at the wavelength of 206 nm. DDTC was made byaddition reaction of diethylamine, carbon disul�de, andsodium hydroxide as follows [27]:

CH3CH2( )2NH + CS2 + NaOH + 2H2O

⟶ CH3CH2( )2NCSSNa · 3H2O(3)

�e wavelength of 206 nm was exactly the characteristicabsorption peak of carbon disul�de [28, 29], indicating thatthe main product of DDTC degradation in wastewater wascarbon disul�de as follows:

C2H5( )2NCSSNa +H2O⟶ C2H5( )2NCSSH +NaOH

C2H5( )2NCSSH⟶ C2H5( )2NH + CS2(4)

Figure 9 shows that with the extension of stewing time,the concentration of carbon disul�de increased slightly,indicating the degradation rate of DDTC increasedgradually.

3.4.2. Degradation Products of DDTC with SodiumHypochlorite. �e scanning results of UV spectrophotom-etry of each reaction solution for reaction time 1min atdi�erent dosages of sodium hypochlorite are shown inFigure 10, on the natural pH value and temperature asbefore.

From Figure 10, the peaks at the wavelength of 256 nmand 282 nm almost disappeared under the dosage of sodiumhypochlorite of 100mg·L−1 and more, indicating that mostDDTC had been degraded in wastewater. At the wavelengthof 206 nm, absorption peaks appeared obviously, suggestingthat carbon sul�de existed in the degradation products. �echaracteristic absorption peak of carbon disul�de decreasedwith the increasing dosage of sodium hypochlorite. Whenthe dosage of sodium hypochlorite was 400mg·L−1, theabsorption peak at 206 nm disappeared and the character-istic absorption peak of sulfate at 191 nm presented clearly[29], indicating that carbon disul�de was further degraded

DDTC concentrationDegradation rate

0

1

2

3

4

5

6

7

DD

TC co

ncen

trat

ion

(mg·

L–1)

30 40 50 60 70 8020Temperature (°C)

92

94

96

98

100

Deg

rada

tion

rate

(%)

Figure 8: In�uence of reaction temperature on the degradation ofDDTC.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Abso

rban

ce

200 225 250 275

282256

206

300 325 350

0-0h1-1h2-2h3-3h

4-4h5-5h6-6h

375175Wavelength (nm)

Figure 9: In�uence of stewing time on the UV absorption spec-trum of reaction solution.

DDTC concentrationDegradation rate

0

2

4

6

8

10

DD

TC co

ncen

trat

ion

(mg·

L–1)

3 5 7 9 111Time (min)

90

92

94

96

98

100

Deg

rada

tion

rate

(%)

Figure 7: In�uence of reaction time on the degradation of DDTC.

6 Journal of Chemistry

and the products of decomposition should be CO2, S, orSO4

2−. Further, with the increase of the dosage of sodiumhypochlorite, the characteristic absorption peak of dieth-ylamine became weaker, indicating that the diethylaminewas further degraded, with possible products of CO2 and N2as follows [30]:

CS2 + 2H2O⟶ CO2 + 2H2S

H2S + NaClO⟶ S +H2O + NaCl

H2S + 4NaClO⟶ H2SO4 + 4NaCl

2 C2H5( )2NH + 26ClO− ⟶ 8CO2 + 10H2O +N2 + 26Cl−

(5)

4. Conclusion

�e characteristics and products of degradation of DDTC inarti�cially prepared bene�ciation wastewater were in-vestigated with or without sodium hypochlorite as an oxi-dant. �e conclusions were as follows:

(1) Without adding sodium hypochlorite, the propertyof degradation of DDTC itself was weak and unableto achieve the timely reuse of the bene�ciationwastewater. Under the natural conditions of pHvalue 5.98 and reaction temperature 25°C, the deg-radation rate of DDTC was only 88.4% with thestewing time of 6 h. In the acidic environment,DDTC was easily degraded, while relatively stable inthe neutral or alkaline environments.

(2) �e DDTC in arti�cially prepared bene�ciationwastewater could be degraded by sodium hypo-chlorite e�ectively. Under the natural condition, thedegradation rate of DDTC can reach 91.38% in 1minwith the dosage of sodium hypochlorite of

400mg·L−1. �e degradation rate of DDTC was af-fected observably by the dosage of sodium hypo-chlorite, reaction time, and reaction temperature.Sodium hypochlorite should be an e�ective oxidantfor the degradation of DDTC in true bene�ciationwastewater due to its advantages and weak impact oflow residual chlorine on the �otation process.

(3) Without adding sodium hypochlorite, the degrada-tion of DDTC gradually occurred with the increaseof stewing time. �e characteristic absorption peakof carbon disul�de at 206 nm could be observedclearly, where carbon disul�de was one of the maindegradation products of DDTC in wastewater.

(4) Under the natural condition, DDTC had been almostcompletely degraded when the dosage of sodiumhypochlorite was 100mg·L−1, while carbon disul�deand diethylamine could be acquired from the UVabsorption spectrum. And, with the increase of thedosage of sodium hypochlorite, carbon disul�de wasfurther decomposed into CO2, S, or SO4

2−, while thediethylamine was decomposed into N2 and CO2.�eresearch results can provide a reference for thetreatment of bene�ciation wastewater containingDDTC.

Data Availability

�e data used to support the �ndings of this study areavailable from the corresponding author upon request.

Conflicts of Interest

�e authors declare that there are no con�icts of interestregarding the publication of this paper.

Acknowledgments

�is work was supported by the National Natural ScienceFoundation of China (grant number 51504054), the Fun-damental Research Funds for the Central Universities (grantnumbers N170104016 and N170106004), and the NaturalScience Foundation of Liaoning Province (grant number20170520335).

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0mg·L–1

10mg·L–1

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200mg·L–1

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0.0

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1.4

Abso

rban

ce

200 225 250 275 300

282256

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325 350 375175Wavelength (nm)

Figure 10: In�uence of the dosage of sodium hypochlorite on theUV absorption spectrum of reaction solution.

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