LSST #1494744, VOL 00, ISS 00

Electrocoagulation/electroflotation of real printing wastewater using copperelectrodes: A comparative study with aluminum electrodesSafwat M. Safwat, Ahmed Hamed, and Ehab Rozaik

QUERY SHEET

This page lists questions we have about your paper. The numbers displayed at left can be found in the text of the paperfor reference. In addition, please review your paper as a whole for correctness.

Q1: Au: Corresponding author Email inserted from CATS. Please check.Q2: Au: References were not cited sequentially. Hence, references have been renumbered from Ref.38. Please check.Q3: Au: The disclosure statement has been inserted. Please correct if this is inaccurate.Q4: Au: The CrossRef database (www.crossref.org/) has been used to validate the references. Mismatches between the original

manuscript and CrossRef are tracked in red font. Please provide a revision if the change is incorrect. Do not comment oncorrect changes.

Q5: Au: Please provide missing editor name or institutional editor name, publisher name and publisher location for Ref. [13].Q6: Au: Please provide missing publisher location and publisher name for Ref. [21].Q7: Au: Please provide missing publisher location and publisher name for Ref. [30].

TABLE OF CONTENTS LISTING

The table of contents for the journal will list your paper exactly as it appears below:

Electrocoagulation/electroflotation of real printing wastewater using copper electrodes: A comparative study with aluminumelectrodesSafwat M. Safwat, Ahmed Hamed, and Ehab Rozaik

Electrocoagulation/electroflotation of real printing wastewater using copperelectrodes: A comparative study with aluminum electrodesSafwat M. Safwata, Ahmed Hamedb, and Ehab Rozaika

aSanitary & Environmental Engineering Division, Faculty of Engineering, Cairo University, Giza, Egypt; bPurchasing & Procurement5 Department, Rowad Modern Engineering, Cairo, EgyptQ1

ABSTRACTMost studies investigated electrocoagulation/electroflotation process (EC/EF) using either alumi-num or iron electrodes. The main aim of this study is to investigate the performance of EC/EF totreat printing wastewater under various experimental conditions using copper electrodes. The

10 effects of several variables, including different electrode materials (copper and aluminum), differ-ent current densities, electrolysis time, and spacing between electrodes on the removal efficiencyof various parameters were investigated. The results showed that the maximum removal efficien-cies for COD,TDS, and oil and grease were obtained when using a copper electrode. Themaximum removal efficiencies were obtained at a gap distance of 4 cm.

ARTICLE HISTORYReceived 27 April 2018Accepted 26 June 2018

KEYWORDSElectrocoagulation;electroflotation; copper;aluminum; wastewater

15 1. Introduction

Printing processes are used for several applicationssuch as printing books and newspapers, clothing, cir-cuit boards, and electrical appliances. Wastewater fromprinting can cause environmental risks due to the high

20 chemical oxygen demand (COD).[1Q2] Chemical coagula-

tion and biodegradation are among the conventionalprocesses used for treatment of printing wastewater.[2,3]

For chemical coagulation, large amounts of sludge willbe generated. Treatment of the sludge is expensive, and

25 secondary pollution may occur if it is not handledproperly.[1] Regarding the biodegradation treatment,microbial activity may be inhibited due to the presenceof toxic pollutants in the printing wastewater.[1,4,5]

Consequently, it is essential to treat printing wastewater30 through an innovative and efficient treatment

technology.Electrochemical wastewater treatment technologies

such as electrocoagulation, electro-oxidation, and elec-troflotation are found to be promising technologies for

35 wastewater treatment.[6,7] These technologies are envir-onmentally friendly options that produce low amountsof sludge, do not require chemical additives, and have aminimal footprint.[8,9] Electrocoagulation and electro-flotation can be a substitute for conventional coagula-

40 tion and flotation, respectively, in wastewater treatmentplants.[10] In electrocoagulation/electroflotation pro-cess, sacrificial anodes, such as aluminum, dissolve

due to an applied current, thus producing active coa-gulant compounds.[10] This technology combines the

45benefits of coagulation, flotation, and electrochemistry.-[8] Electrocoagulation/electroflotation (EC/EF) offersmany advantages over traditional coagulation/floccula-tion, such as higher efficiency, shorter retention time,prevention of secondary pollution caused by added

50chemicals, and simple operation.[11,12] Coagulation/flocculation uses chemical coagulants/flocculants suchas metal salts or polyelectrolytes, while EC/EF generatescoagulants in situ through electrolytic oxidation of asacrificial anode material which results in much less

55sludge production.[8] The theories behind coagulation/flocculation and EC/EF are basically the same.[13] Bothmethods remove particles from wastewater by destabi-lizing repulsive forces that keep the particles suspendedin water.[8] When the repulsive forces are destabilized,

60the suspended particles will form larger particles calledflocs that can settle.[8] In EC/EF, a direct current (DC)voltage is applied to an electrochemical cell with anodeand cathode metal electrodes, immersed in wastewateras the electrolyte.[12] There are three main processes

65that happen during the electrocoagulation/electroflota-tion process: (i) oxidation of the anode, (ii) generationof gas bubbles at the cathode, and (iii) flotation andsedimentation of the flocs formed.[14] When a currentis applied to the process, oxidation reactions take place

70on the sacrificial anode producing cations, and reduc-tion reactions that occur on the cathode.[11] Those

CONTACT Safwat M. Safwat safwatms1@hotmail.comColor versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsst.

SEPARATION SCIENCE AND TECHNOLOGY2018, VOL. 00, NO. 00, 1–12https://doi.org/10.1080/01496395.2018.1494744

© 2018 Taylor & Francis

cations form metal hydroxides in aqueous media.[11]

Metal hydroxide species provide effective destabiliza-tion of suspended solids. At the cathode, hydrogen gas

75 is continuously generated. Flocculated particles areformed and pollutants are removed with the aid ofscouring and floating.[12] The removal mechanismcould be via adsorption, charge neutralization, orsweep coagulation.[11,15] In the EC/EF process, the elec-

80 trochemical reactions with metal M as electrodes are asfollows [10]:

At the anode : M ! Mnþ þ ne�; for coagulation

At the cathode : 2H2Oþ 2e�

! H2 þ 2OH�; for flotation

Various types of wastewater have been successfullytreated using EC/EF.[16,17] Previous studies haveshown that EC/EF is a successful treatment process

85 for treatment of industrial wastewater, especially thoseof high strength and toxic materials.[18,19] Onestudy showed that over 97% of heavy metal ions frommetal plating wastewater were removed usingelectrocoagulation.[20] Another study showed that the

90 maximum efficiencies of phenol removal from aqueoussolutions with aluminum and iron electrodes were94.72% and 98.0%, respectively.[21] Removal of phenolfrom oil refinery wastewater was also investigated usingelectrocoagulation with an aluminum screen anode,

95 and the removal efficiency of phenol reached 97%.[22]

In a study investigating the treatment of paper milleffluents using electrocoagulation, the removal efficien-cies using an aluminum electrode were 70% of bio-chemical oxygen demand, 98% of phenol, and 75% of

100 the COD after 7.5 min. While using an iron electrode,the removal efficiencies were 80%, 93%, and 55%,respectively.[23] During treatment of poultry slaughter-house wastewater by electrocoagulation, the removal ofthe COD reached 93% with aluminum electrodes, while

105 the maximum removal of oil and grease obtained was98% with iron electrodes.[24] Treatment of olive oilmill wastewater was also studied using electrocoagula-tion. Under a 30-min retention time, the removal effi-ciency of the COD was 52% and 42% when using

110 aluminum anode and iron anode, respectively.[25]

Electrocoagulation was used to investigate the removalof polycyclic aromatic hydrocarbons in a paper-makingwastewater, and the results showed that the processeffectively removed a total of 86% of polycyclic aro-

115 matic hydrocarbons by mass in the effluent.[26]

Moreover, the electrocoagulation process was able totreat fluoride by reducing its concentration from theinitial 6.0 mg/L to lower than 0.5 mg/L.[27] A group ofresearchers used electrocoagulation to treat baker’s

120yeast production wastewater. The results showed thatthe maximum removal efficiencies of the COD, totalorganic carbon, and turbidity under optimal operatingconditions were 71%, 53%, and 90% for the aluminumelectrode and 69%, 52%, and 56% for the iron electrode,

125respectively.[28] The EC/EF can be used as a pre-treat-ment step to reduce the contaminant loads of highstrength industrial wastewater, such as printing waste-water, prior to the following treatment steps.[8] It isworth noting that most studies investigated EC/EF

130using either aluminum electrodes or iron electrodes asthe sacrificial anode. Since other types of electrodes,such as copper electrodes, showed promising resultswhen used in EC/EF, it is essential to investigate thesetypes with real wastewater to show their performance

135compared to the most widely used electrodes (alumi-num or iron).[29–31] To the best of authors’ knowledge,EC/EF using a copper electrode has not been investi-gated yet in the treatment of printing wastewater.Hence using EC/EF process with copper electrodes

140can be regarded as a new and potential method fortreatment of printing wastewater. The main aim ofthis study is to investigate the performance of the EC/EF process using copper electrodes in batch operatingmode to treat real printing wastewater under various

145experimental conditions using copper electrodes. Theconfiguration of EC/EF process used in this study is thesimplest type mentioned in literature. The effects of theoperating variables, including different electrode mate-rials (copper and aluminum), different current densities

150(CDs), electrolysis time, and spacing between electro-des, on the removal efficiency of several parameterswere examined. These parameters were COD, totaldissolved solids (TDS), and oil and grease. The energyconsumption for the electrocoagulation cell was also

155calculated in this work.

2. Materials and methods

2.1. Characteristics of real printing wastewater

The wastewater used in this study was collected fromthe printing industry in Egypt. The characteristics of

160wastewater are shown in Table 1.

Table 1. Characteristics of wastewater.Parameter Unit Value

pH - 6.8COD mg/l 7150TDS mg/l 6800Total suspended solids (TSS) mg/l 72.5Oil and grease mg/l 385Color - Yellowish

2 S. M. SAFWAT ET AL.

2.2. Electrocoagulation system setup

The EC/EF unit is shown in Figure 1. Batch experi-ments were performed under a constant temperatureof 20°C ± 2°C for 90 min. The EC/EF unit consists

165 of an electrochemical reactor which was a one-literglass beaker with magnetic stirring. The unit con-tained two parallel electrodes connected externallyto a DC power supply. The cathode electrode wasstainless steel, and the anode electrode was either

170 copper (Cu) or aluminum (Al). The submerged sur-face area of each electrode was 28 cm2. The gapbetween the electrodes was 4 cm, but some experi-ments have been performed with 2 and 6 cm gaps.The stirring speed was kept low (100 rpm) to avoid

175 shearing of the flocs.[32] The electrolysis time wasmaintained in the range of 5– 90 min. Four CDs; 7,14, 21 and 28 mA/cm2, were examined. An ammeterand voltmeter were used to check the current inten-sity and the voltage during the EC/EF process.

180 Samples were periodically withdrawn then filteredto eliminate sludge formed during electrolysis forfurther analysis.

2.3. Analysis

Influent and effluent samples were collected for analy-185 sis. In addition, COD, TSS, and oil and grease were

measured according to the standard methods.[33] TheTDS and pH were measured using a multi-meter. Thepollutant removal efficiency (%) after treatment wascalculated using the following formula:

Removal efficiencyð%Þ ¼ ðC0 � CeÞ=C0 � 100

190 where Co and Ce are the influent and effluent con-centrations of pollutants, respectively. The sludgegenerated during the EC/EF process was analyzedusing a Fourier transform infrared (FTIR) spectro-meter. The morphologies of the anode electrodes

195were investigated using scanning electron micro-scopy (SEM). Chemical coagulation tests were con-ducted using the jar test. Copper sulfate andaluminum sulfate (Loba Chemie, India) were usedas coagulants to simulate copper and aluminum

200electrodes. Experiments of conventional coagulationincluded flash mixing for 1.5 min at 100 rpm andslow mixing for 20 min at 30 rpm, followed by a20 min settling period, after which the samples werecollected for further analysis.[34] All chemicals were

205of analytical grade. All experiments were run induplicate, and the results were reported as the aver-age of the measurements.

3. Results and discussion

3.1. Effect of current density on EC/EF

210In the EC/EF process, a CD that determines the rateof hydrogen bubble formation and the growth offlocs was applied between the two electrodes topromote the dissolution of the electrodes to formcoagulant species.[35] The effect of the CD was ana-

215lyzed for copper and aluminum electrodes between7 and 28 mA/cm2. Figures 2 and 3 show the removalefficiencies of the COD and TDS, respectively. Ascan be observed, the rate of removal of the COD forall CDs increased rapidly during the first 10 min.

220Then, the rate of removal efficiency of the CODdecreased due to the desorption phenomenon.[19]

Furthermore, oxidation reactions that promotedthe corrosion phenomena might lead to the forma-tion of stable oxide layers on the surface of anode

225electrodes. These layers caused passivation effects,so decreased the efficiency of EC/EF cell.[36] Themaximum values of the COD removal efficienciesafter 10 min were 60% and 49% for copper andaluminum electrode, respectively. The maximum

230values of the COD removal efficiency after 90 minwhen using copper electrode was around 67% andobtained at a CD of 28 mA/cm2. For the aluminumelectrode, the maximum value of the COD removalefficiency after 90 min was 55% and obtained at CD

235of 21 mA/cm2. At a CD of 28 mA/cm2, the removalefficiency of the COD was higher during the entireperiod when using the copper electrode, while theremoval efficiencies of the COD for CDs of 14 mA/cm2 and 21 mA/cm2 were very close.

240For the TDS removal efficiency, the performanceof the copper electrode was better than that of thealuminum electrode for all CDs. The maximumremoval efficiencies of the TDS after 90 min were24% and 7% for copper and aluminum electrodes,Figure 1. EC/EF unit.

SEPARATION SCIENCE AND TECHNOLOGY 3

245 respectively. During the EC/EF process, the waste-water remains yellowish in color when using thealuminum electrode, while the color changed fromyellowish to blue when using the copper electrode.The blue color was due to the dissociation of copper

250 into the wastewater. The number of ions released asCu2+ or Al3+ depends on the applied CD and deter-mines the amount of the resulting coagulant.Consequently, the rate of formation of metal hydro-xide increased as the amount of metal ions that

255 dissolved into the wastewater increased. Thisincreased the removal efficiencies of both the CODand TDS. Moreover, adsorption of pollutantsoccurred on the surface of metal oxides, hydroxides,and oxyhydroxides.[3,37] The reduction of pollutants

260 could also be due to the destabilization mechanismthat comprises three main steps: compression of thedouble layer, followed by charge neutralization, then

floc formation.[37] Moreover, the increase of CD ledto an increase in the generation of hydrogen bubbles

265and a decrease in their sizes. This results in theremoval of pollutants through flotation. In the caseof the aluminum electrode, the maximum removalefficiency of the COD was not obtained at the max-imum CD used. This might be because higher CDs

270increase the turbulence in the system. Increasing theturbulence can affect the coagulation processbecause the particles will not have enough time toagglomerate and remove the pollutants.

Figure 4 shows the change of pH values over time.275The pH increased for all values of CDs over time. This

might be due to the reactions occurring at the cathode.During the EC/EF process, water molecules receiveelectrons and dissociate into hydrogen bubbles andhydroxyl ions, causing an increase in pH values. The

280increase of pH values in the case of the copper

ab

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80 90

CO

D r

em

ova

l (%

)

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80 90

CO

D r

em

ova

l (%

)

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

Figure 2. COD removal efficiencies over time at various current densities: a) Cu electrode, b) Al electrode.

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90

TD

S r

em

ova

l (%

)

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90

TD

S r

em

ova

l (%

)

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

a b

Figure 3. TDS removal efficiencies over time at various current densities: a) Cu electrode, b) Al electrode.

4 S. M. SAFWAT ET AL.

electrode was more than those for the aluminum elec-trode for all CDs. This indicates that the amount ofdissociation of water molecules in the case of copperelectrode was more than that for the aluminum elec-

285 trode. The higher pH values were obtained for bothtypes of anodes at the higher CDs (21 and 28 mA/cm2),and this is because at high CDs, corrosion of the cath-ode occurs due to the intensive production of hydro-xide anions.[32] Copper is dissolved to produce divalent

290 ions Cu2+ ions, forming copper hydroxide, which ther-modynamically forms at 7.7.[38] For pH values between4 and 9.5, Al(OH)3 (s) predominates.[8] The increase inpH values during EC/EF process favors the formationof these hydroxides. These hydroxides trap the colloids/

295 pollutants in a sweep coagulation manner as they pre-cipitate leading to a higher COD removal.[12]

Figures 5 and 6 show the effluent TSS and oil andgrease when using copper and aluminum electrodes atdifferent CDs. The copper electrode provides the best

300removal efficiency for oil and grease. For oil and grease,intensive fine hydrogen bubbles were formed at a CDof 21 mA/cm2, which adhered to the oil droplets andraised them to the surface the of solution in a sweepingaction called sweep flocculation, as shown in

305Figure 7.[39] The number of flocs formed with thecopper electrode was more than that of the aluminumelectrode at all CDs, leading to more TSS in the effluentfor the copper electrode. Since a high removal of pol-lutants occurred at a CD of 21 mA/cm2, the next

310experiments for both types of electrodes were per-formed at this value of CD.

3.2. Effect of spacing between electrodes

It is known that the gap distance between electrodesaffects the ohmic potential of the EC/EF cell and the

315energy consumption.[9] The effects of spacingbetween electrodes were investigated at a CD of21 mA/cm2. Figures 8 and 9 show the removal

a b

6

7

8

9

10

11

12

13

0 20 40 60 80

pH

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

6

6.5

7

7.5

8

8.5

9

0 20 40 60 80

pH

Time (min)

28 mA/cm2 21 mA/cm2

14 mA/cm2 7 mA/cm2

Figure 4. pH over time at various current densities: a) Cu electrode, b) Al electrode.

0

500

1000

1500

2000

2500

3000

28 mA/cm2 21 mA/cm2 14 mA/cm2 7 mA/cm2

Efflu

en

t T

SS

(m

g/l)

Cu electrode Al electrode

Figure 5. Effluent TSS at various current densities: a) Cu electrode, b) Al electrode.

SEPARATION SCIENCE AND TECHNOLOGY 5

efficiencies of COD and TDS, respectively, for dif-ferent gap distances (2 cm, 4 cm, and 6 cm). The

320 maximum removal efficiencies were obtained at aspacing of 4 cm. Although decreasing the gap dis-tance leads to decreasing the resistance between theelectrodes and increasing the efficiency of the pol-lutant’ removal, this was not the case in this study.

325 When increasing the spacing to 6 cm or decreasingit to 2 cm, the pollutant removal efficienciesdecreased compared to those at spacing of 4 cm.This phenomenon might be due to the configurationof the system. The cross-section of the reactor was

330 circular, and the spacing of 4 cm between electrodeswas approximately equidistant between the two elec-trodes and between each electrode and the edge.This equidistance might lead to two results: i) uni-form distribution of flocs inside the reactor and ii)

335 minimization of the disturbance that could occur tothe flocs during mixing compared to the disturbance

when the electrodes are very close to each other orwhen they are very close to the edges. Moreover, thesmall gap distance between the electrodes led to a

340high electrostatic effect that hinders the particlecollision. More electrochemically generated gas bub-bles caused turbulence, while the big gap distancesignificantly decreased the formation of flocs.-[36,40,41] The behavior during the removal of pollu-

345tants was almost the same for all gap distances. Therate of removal of the pollutants was high duringthe first 10 min, then decreased until the end of theexperiments. The maximum efficiencies of the CODremoval when using the copper electrode for the gap

350distances of 2, 4, and 6 cm were 19%, 65%, and 15%,respectively. The maximum efficiencies of CODremoval when using the aluminum electrode forthe gap distances 2, 4, and 6 cm were 24%, 55%,and 15%, respectively. The maximum efficiencies of

355TDS removal when using the copper electrode forgap distances 2, 4, and 6 cm were 8%, 24%, and 5%,respectively. The maximum efficiencies of TDSremoval when using aluminum electrode for gapdistances 2, 4, and 6 cm were 7%, 3%, and 5%,

360respectively. Removal of the COD and TDS usingthe copper electrode were higher than those whenusing the aluminum electrode for all gap distances.The effluent values of oil and grease in the case ofthe copper electrode were less than those for the

365aluminum electrode as shown in Figure 10. Thevalues of TSS in effluent increased in the case ofthe copper electrode when compared to those valuesobtained from the aluminum electrode. This isbecause the number of flocs formed in the case of

370the copper was more than that formed in the case ofthe aluminum. This confirms that the EC/EF unit

Figure 7. Floatation at the end of EF/EF process using copperelectrode.

0

50

100

150

200

250

300

350

400

450

28 mA/cm2 21 mA/cm2 14 mA/cm2 7 mA/cm2

Efflu

en

t O

il &

gre

ase

(m

g/l)

Cu electrode Al electrode

Figure 6. Effluent Oil and grease at various current densities: a) Cu electrode, b) Al electrode.

6 S. M. SAFWAT ET AL.

0

500

1000

1500

2000

2500

3000

Cu @S=2cm Cu @S=6cm Al @S=2cm Al @S=6cm

Co

nce

ntra

tio

n (

mg

/l)

Effluent Oil & grease Effluent TSS

Figure 10. Effluent Oil and grease, and TSS at various gap distances.

a b

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90

CO

D r

em

ova

l (%

)

Time (min)

S=2cm S=4cm S=6cm

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90

CO

D r

em

ova

l (%

)

Time (min)

S=2cm S=4cm S=6cm

Figure 8. COD removal efficiencies over time at various gap distances a) Cu electrode, b) Al electrode.

a b

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90

TD

S r

em

ova

l (%

)

Time (min)

S=2cm S=4cm S=6cm

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90

TD

S r

em

ova

l (%

)

Time (min)

S=2cm S=4cm S=6cm

Figure 9. TDS removal efficiencies over time at various gap distances a) Cu electrode, b) Al electrode.

SEPARATION SCIENCE AND TECHNOLOGY 7

with the copper electrode performs better than theEC/EF unit with the aluminum electrode.

3.3. Characterization of the by-products obtained375 from the EC/EF by FTIR

To characterize the by-products, FTIR analyses werecarried out. Figure 11 shows the characterizations ofthe sludge samples produced at 21 mA/cm2 using cop-per and aluminum electrodes. It can be observed that

380 FTIR spectra for sludge samples showed some spectro-scopic changes. The finger-prints of the two sludgesamples between 400 cm−1 and 1500 cm−1 were notidentical, confirming the presence of different compo-nents. These different components were due to the

385dissociation of either copper or aluminum electrodesduring the electrocoagulation process. The FTIR spec-tra of the two sludge samples showed a broad andintense band between 3000 cm−1 and 3700 cm−1, indi-cating the presence of an OH group. The presence of

390this group enhanced the adsorption of the counter ionsduring settling. This confirms that adsorption is one ofthe removal mechanisms of the EC/EF process.

3.4. Morphologies of electrodes

The morphologies of copper and aluminum electrodes395were investigated before and after electrocoagulation at

a CD of 21 mA/cm2. Figure 12 shows the SEM imagesof the electrodes before and after the treatment. Forboth the copper and aluminum electrodes, corrosionhappened to the anodes after the EC/EF experiment,

400confirming the occurrence of the treatment process.The surface of the copper electrode contained cracks,while that of the aluminum electrode was rough andcontained dents. The formation of a large number ofcracks and dents in anodes is attributed to the con-

405sumption of metal at active sites of electrodes due tothe generation of oxygen at the surfaces.[42] The corro-sion in the copper electrode was a uniform corrosion,while that for the aluminum electrode was a pittingcorrosion. Uniform corrosion is better than pitting

410corrosion, since it is easier to predict.

3.5. Electrical energy consumption

Key factors, such as energy cost, must be taken intoconsideration in the process optimization. The energyconsumptions required for the treatment of the print-

415ing wastewater versus the operating time at differentCDs is shown in Figure 13. The electrical energy

70

75

80

85

90

95

100

40080012001600200024002800320036004000

Ab

so

rb

an

ce

%

Wave Number (cm-1)

Al Cu

Figure 11. FTIR spectra of by-products.

a b

c d

Figure 12. SEM images of electrodes: a) Cu electrode beforetreatment, b) Cu electrode after treatment, c) Al electrodebefore treatment, and d) Al electrode after treatment.

8 S. M. SAFWAT ET AL.

consumption (EEC) was calculated in terms of kwh/m3

of treated effluent using the following equation:

EEC kwh=m3� � ¼ UIt

V

where U is the average cell voltage (V), I is the current420 intensity (A), t is the time of electrocoagulation treat-

ment (h), and V is the volume of effluent to be treated(l). The results show that energy consumptionincreased with the CD. The values of energy consump-tion for the copper electrode were more than those for

425 the aluminum electrode. The maximum values forenergy consumption were 14 kwh/m3 and 13 kwh/m3

for the copper electrode and aluminum electrode,respectively. The values of the COD removal efficien-cies after 10 min with a CD of 21 mA/cm2 represented

430 more than 90% of the total COD removal efficienciesobtained after 90 min, as observed in Section 3.1. As aresult, 10 min can be considered the optimum condi-tion. The maximum values for energy consumption at aCD of 21 mA/cm2 were 0.86 kwh/m3 and 0.8 kwh/m3

435 for the copper electrode and aluminum electrode,respectively. These values are within the range of valuesmentioned in the literature for energy consumptionwith the electrocoagulation processes, lying between0.002 and 58 kwh/m3.[43] These observations show

440 that the copper anode is more energy demanding thanthe aluminum.

3.6. Performances of chemical coagulation

Copper sulfate and aluminum sulfate were used atdifferent dosages (10 g/l–160 g/l) to investigate the

445 difference in performance between chemical

coagulation and electrocoagulation, as shown inFigure 14. Figure 15 shows the removal efficiencies ofthe COD using chemical coagulants. The values of theCOD removal efficiencies increased with increasing

450coagulant doses. Aluminum sulfate gives better resultswhen compared to copper sulfate. The maximumremoval efficiencies of the COD were 14% and 28%for copper sulfate and aluminum sulfate, respectively.These values are much lower than those obtained using

455electrocoagulation, although the amount of coagulantused is practically very high (160 g/l). These resultsconfirm that the performance of electrocoagulation isbetter than that of chemical coagulation in treatingprinting wastewater.

4603.7. Limitations of the study

The lack of information about concentrations of copperand aluminum ions in the effluent is one of the limita-tions. These ions can cause environmental problems.The concentrations of these ions in effluent were not

0

2

4

6

8

10

12

14

16

0 20 40 60 80

EE

C (

Kw

h/m

3)

Time (min)

CD=7 mA/cm2 CD=14 mA/cm2

CD= 21 mA/cm2 CD= 28 mA/cm2

0

2

4

6

8

10

12

14

16

0 20 40 60 80

EE

C (

Kw

h/m

3)

Time (min)

CD=7 mA/cm2 CD=14 mA/cm2

CD= 21 mA/cm2 CD= 28 mA/cm2

Figure 13. EEC over time at various current densities: a) Cu electrode, b) Al electrode.

Figure 14. Jar test using copper sulfate.

SEPARATION SCIENCE AND TECHNOLOGY 9

465 included in the present study, as the study focused onthe ability of EC/EF process in reducing influent pollu-tants of real printing wastewater. Another limitation isthe time period after which the anode electrodes willneed to be replaced due to dissociation in the solution

470 during treatment process.

4. Conclusion

This work studied the treatment of printing wastewaterusing the EC/EF process. Two different electrodes (cop-per and aluminum) were examined. The results showed

475 that the pollutant removal efficiencies when using thecopper electrode were better than those found whenusing the aluminum electrode. The maximum value ofthe COD removal efficiency was around 67%, obtained ata CD of 28 mA/cm2. For the aluminum electrode, the

480 maximum value of the COD removal efficiency was 55%,obtained at a CD of 21 mA/cm2. The values of pHincreased for all values of CD over time. The maximumremoval efficiencies of the TDS after 90 min were 24%and 7% for the copper and aluminum electrodes, respec-

485 tively. EC/EF process was not sufficient in removal ofcolor, so further treatment is needed to remove colorfrom effluent. The maximum removal efficiencies wereobtained at a gap distance of 4 cm. Characterizations ofthe sludge samples produced at 21 mA/cm2 were carried

490 out by FTIR. The finger-prints of the samples were notidentical, confirming the presence of different compo-nents. The morphologies of the copper and aluminumelectrodes were analyzed before and after electrocoagula-tion. For both copper and aluminum electrodes, corro-

495 sion happened to the anodes after the EC/EF processconfirming the occurrence of metal dissociation. Thecorrosion in the copper electrode was a uniform corro-sion, while that for the aluminum electrode was a pitting

corrosion. The results showed that energy consumption500increased with the CD. The performance of electrocoa-

gulation was better than that of the chemical coagulationin treating real printing wastewater.

Acknowledgments

The authors wish to thank the specialists at Micro Analytical505Center, Cairo University; National Research Center; and the

central laboratory of Egyptian mineral resources authority forhelp with the analyses. This research did not receive anyspecific grant from funding agencies in the public, commer-cial, or not-for-profit sectors.

510Disclosure statement

No potential conflict of interest was reported by the authors. Q3

References

[1] Tung, C.H.; Shen, S.Y.; Chang, J.H.; Hsu, Y.M.; Lai, Y.C. (2013) Treatment of Real printing wastewater with

515an electrocatalytic process. Sep PurificationTechnological, 117 131–136. doi:10.1016/j.seppur.2013.07.028. Q4

[2] Ahmed, S.; Rozaik, E.; Abdel-Halim, H. (2016)Performance of single-chamber microbial fuel cells

520using different carbohydrate-rich wastewaters and dif-ferent inocula. Polish Journal Environment Studies, 252. doi:10.15244/pjoes/61115.

[3] Safwat, S.; Matta, M. (2018) Adsorption of urea ontogranular activated alumina: A comparative study with

525granular activated carbon. Journal Dispers SciencesTechnological. doi:10.1080/01932691.2018.1461644.

[4] Safwat, S.M.;. (2018) Performance of moving bed bio-film reactor using effective microorganisms. JournalClean Products. doi:10.1016/j.jclepro.2018.03.041.

530[5] Ahmed, S.; Rozaik, E.; Abdelhalim, H. (2015) Effect ofconfigurations, bacterial adhesion, and anode surfacearea on performance of microbial fuel cells used for

0

5

10

15

20

25

30

0 20 40 60 80 100 120 140 160

CO

D r

em

ova

l (%

)

Coagulant dose (g/l)

Copper sulfate Aluminum sulphate

Figure 15. COD removal efficiencies over different coagulant doses.

10 S. M. SAFWAT ET AL.

treatment of synthetic wastewater. Water, Air, SoilPollution, 226 (9): 300. doi:10.1007/s11270-015-2567-3.

535 [6] Ahmadzadeh, S.; Dolatabadi, M. (2018) Removal ofacetaminophen from hospital wastewater using elec-tro-fenton process. Environment Earth Sciences, 77(2): 1–11. doi:10.1007/s12665-017-7203-7.

[7] Ahmadzadeh, S.; Modeling, D.M. (2018) Kinetics study540 of electrochemical peroxidation process for mineraliza-

tion of bisphenol a; a new paradigm for groundwatertreatment. Journal Molecular Liq, 254 76–82.doi:10.1016/j.molliq.2018.01.080.

[8] Moussa, D.T.; El-Naas, M.H.; Nasser, M.; Al-Marri, M.545 J.; Comprehensive, A. (2017) Review of electrocoagula-

tion for water treatment: Potentials and challenges.Journal of Environmental Management, 186 24–41.doi:10.1016/j.jenvman.2016.10.032.

[9] Ahmadzadeh, S.; Asadipour, A.; Pournamdari, M.;550 Behnam, B.; Rahimi, H.R.; Dolatabadi, M. (2017)

Removal of ciprofloxacin from hospital wastewaterusing electrocoagulation technique by aluminum elec-trode: optimization and modelling through responsesurface methodology. Processing Safety Environment

555 Protection, 109 538–547. doi:10.1016/j.psep.2017.04.026.

[10] Wang, C.T.; Chou, W.L.; Kuo, Y.M. (2009) Removal ofCOD from laundry wastewater by electrocoagulation/electroflotation. Journal of Hazardous Materials, 164

560 (1): 81–86. doi:10.1016/j.jhazmat.2008.07.122.[11] Barışçı, S.; Turkay, O. (2016) Domestic greywater treat-

ment by electrocoagulation using hybrid electrodecombinations. Journal Water Processing Engineering,10 56–66. doi:10.1016/j.jwpe.2016.01.015.

565 [12] Nguyen, D.D.; Ngo, H.H.; Guo, W.; Nguyen, T.T.;Chang, S.W.; Jang, A.; Yoon, Y.S. (2016) Can electro-coagulation process be an appropriate technology forphosphorus removal from municipal wastewater? sci.Total Environment, 563 549–556. doi:10.1016/j.

570 scitotenv.2016.04.045.[13] Zhang, X.; Lin, H.; Hu, B.; Lin, H.; Hu, B. (2018) The

effects of electrocoagulation on phosphorus removaland particle settling capability in swine manure. InSep. Purif. Technol.Q5

575 [14] Emamjomeh, M.M.; Sivakumar, M. (2009) Review ofpollutants removed by electrocoagulation and electro-coagulation/flotation processes. Journal ofEnvironmental Management, 90 (5): 1663–1679.doi:10.1016/j.jenvman.2008.12.011.

580 [15] Al-Qodah, Z.; Heavy Metal, A.-S.M. (2017) IonsRemoval from Wastewater Using ElectrocoagulationProcesses: A comprehensive review. Sep SciencesTechnological, 6395 (September): 1–28. doi:10.1080/01496395.2017.1373677.

585 [16] Mohamud, A.A.; Çalışkan, Y.; Bektaş, N.; Yatmaz, H.C.(2018) Investigation of shipyard wastewater treatmentusing electrocoagulation process with Al electrodes. SepSciences Technological: 1–8. doi:10.1080/01496395.2018.1449860.

590 [17] Nayır, T.Y.; Kara, S. (2017) Container washing waste-water treatment by combined electrocoagulation –electrooxidation. Sep Sciences Technological: 1–12.

[18] Ahmadzadeh, S.; Asadipour, A.; Yoosefian, M.;Dolatabadi, M. (2017) Improved electrocoagulation

595process using chitosan for efficient removal of cefazolinantibiotic from hospital wastewater through sweepflocculation and adsorption: kinetic and IsothermStudy. Desalin Water Treatment, 92: 21492.

[19] Yoosefian, M.; Ahmadzadeh, S.; Aghasi, M.;600Dolatabadi, M. (2017) Optimization of electrocoagula-

tion process for efficient removal of ciprofloxacin anti-biotic using iron electrode; kinetic and isothermstudies of adsorption. Journal Molecular Liq, 225 544–553. doi:10.1016/j.molliq.2016.11.093.

605[20] Al-Shannag, M.; Al-Qodah, Z.; Bani-Melhem, K.;Qtaishat, M.R.; Alkasrawi, M. (2015) Heavy metalions removal from metal plating wastewater using elec-trocoagulation: kinetic study and process performance.Chemical Engineering Journal, 260 749–756.

610doi:10.1016/j.cej.2014.09.035.[21] Bulletin, F.E.; Sciences, M.; Sciences, M. (2012) Phenol

Removal by Electrocoagulation Process from AqueousSolutions, January. Q6

[22] Abdelwahab, O.; Amin, N.K.; El-Ashtoukhy, E.S.Z.615(2009) Electrochemical removal of phenol from oil

refinery wastewater. Journal of Hazardous Materials,163 (2–3): 711–716. doi:10.1016/j.jhazmat.2008.07.016.

[23] Uǧurlu, M.; Gürses, A.; Doǧar, Ç.; The, Y.M. (2008)Removal of lignin and phenol from paper mill effluents

620by electrocoagulation. Journal of EnvironmentalManagement, 87 (3): 420–428. doi:10.1016/j.jenvman.2007.01.007.

[24] Kobya, M.; Senturk, E.; Bayramoglu, M. (2006)Treatment of poultry slaughterhouse wastewaters by

625electrocoagulation. Journal of Hazardous Materials,133 (1–3): 172–176. doi:10.1016/j.jhazmat.2005.10.007.

[25] Inan, H.; Dimoglo, A.; Şimşek, H.; Karpuzcu, M.(2004) Olive oil mill wastewater treatment by meansof electro-coagulation. Sep Purification Technological,

63036 (1): 23–31. doi:10.1016/S1383-5866(03)00148-5.[26] Gong, C.; Shen, G.; Huang, H.; He, P.; Zhang, Z.;

Removal, M.B. (2017) Transformation of polycyclicaromatic hydrocarbons during electrocoagulationtreatment of an industrial wastewater. Chemosphere,

635168 58–64. doi:10.1016/j.chemosphere.2016.10.044.[27] Khatibikamal, V.; Torabian, A.; Janpoor, F.;

Hoshyaripour, G. (2010) Fluoride removal from indus-trial wastewater using electrocoagulation and itsadsorption kinetics. Journal of Hazardous Materials,

640179 (1–3): 276–280. doi:10.1016/j.jhazmat.2010.02.089.[28] Kobya, M.; Delipinar, S. (2008) Treatment of the

baker’s yeast wastewater by electrocoagulation.Journal of Hazardous Materials, 154 (1–3): 1133–1140. doi:10.1016/j.jhazmat.2007.11.019.

645[29] Prajapati, A.K.; Chaudhari, P.K.; Pal, D.; Chandrakar,A.; Choudhary, R. (2016) Electrocoagulation treatmentof rice grain based distillery effluent using copper elec-trode. Journal Water Processing Engineering, 11 1–7.doi:10.1016/j.jwpe.2016.03.008.

650[30] Song, P.; Yang, Z.; Zeng, G.; Yang, X.; Xu, H.; Wang,L.; Xu, R.; Xiong, W.; Ahmad, K. (2017)Electrocoagulation Treatment of Arsenic inWastewaters: A Comprehensive Review. Vol. 317. Q7

[31] Sirajuddin; Kakakhel, L.; Lutfullah, G.; Bhanger, M.I.;655Shah, A.; Niaz, A. (2007) Electrolytic recovery of chro-

mium salts from tannery wastewater. Journal of

SEPARATION SCIENCE AND TECHNOLOGY 11

Hazardous Materials, 148 (3): 560–565. doi:10.1016/j.jhazmat.2007.03.011.

[32] Attour, A.; Touati, M.; Tlili, M.; Ben Amor, M.;660 Lapicque, F.; Leclerc, J.P. (2014) Influence of operating

parameters on phosphate removal from water by elec-trocoagulation using aluminum electrodes. SepPurification Technological, 123 124–129. doi:10.1016/j.seppur.2013.12.030.

665 [33] APHA. (2005) No Title, American Public HealthAssociation/American Water Works Association/Water Environment Federation: Washington DC.

[34] Zhao, Y.X.; Gao, B.Y.; Cao, B.C.; Yang, Z.L.; Yue, Q.Y.;Shon, H.K.; Kim, J.H. (2011) Comparison of coagula-

670 tion behavior and floc characteristics of titanium tetra-chloride (TiCl4) and polyaluminum chloride (PACl)with surface water treatment. Chemical EngineeringJournal, 166 (2): 544–550. doi:10.1016/j.cej.2010.11.014.

675 [35] Fajardo, A.S.; Rodrigues, R.F.; Martins, R.C.; Castro, L.M.; Quinta-Ferreira, R.M. (2015) Phenolic wastewaterstreatment by electrocoagulation process using Znanode. Chemical Engineering Journal, 275 331–341.doi:10.1016/j.cej.2015.03.116.

680 [36] Garcia-Segura, S.; Eiband, M.M.S.G.; de Melo, J.V.;Martínez-Huitle, C.A. (2017) Electrocoagulation andadvanced electrocoagulation processes: A generalreview about the fundamentals, emerging applicationsand its association with other technologies. Journal

685 Electroanal Chemical, 801 267–299. doi:10.1016/j.jelechem.2017.07.047.

[37] Mollah, M.Y.A.; Morkovsky, P.; Gomes, J.A.G.;Kesmez, M.; Parga, J.; Cocke, D.L.; Fundamentals, P.

(2004) Future Perspectives of Electrocoagulation.690Journal of Hazardous Materials, 114 (1–3): 199–210.

doi:10.1016/j.jhazmat.2004.08.009.[38] Ali, I.; Asim, M.; Khan, T.A. (2013) Arsenite removal

from water by electro-coagulation on zinc-zinc andcopper-copper electrodes. International Journal

695Environment Sciences Technological, 10 (2): 377–384.doi:10.1007/s13762-012-0113-z.

[39] An, C.; Huang, G.; Yao, Y.; Zhao, S. (2017) Emergingusage of electrocoagulation technology for oil removalfrom wastewater: A review. The Science of the Total

700Environment, 579 537–556. doi:10.1016/j.scitotenv.2016.11.062.

[40] Lee, S.Y.; Gagnon, G.A. (2016) Comparing the Growthand Structure of Flocs from Electrocoagulation andChemical Coagulation. Journal Water Processing

705Engineering, 10 20–29. doi:10.1016/j.jwpe.2016.01.012.[41] Hakizimana, J.N.; Gourich, B.; Chafi, M.; Stiriba, Y.;

Vial, C.; Drogui, P.; Naja, J. (2017) Electrocoagulationprocess in water treatment: A review of electrocoagula-tion modeling approaches. Desalination, 404 1–21.

710doi:10.1016/j.desal.2016.10.011.[42] Kamaraj, R.; Vasudevan, S. (2015) Evaluation of elec-

trocoagulation process for the removal of strontiumand cesium from aqueous solution. ChemicalEngineering Researcher Design, 93 522–530.

715doi:10.1016/j.cherd.2014.03.021.[43] Kuokkanen, V.; Kuokkanen, T.; Rämö, J.; Lassi, U.

(2013) Recent applications of electrocoagulation intreatment of water and wastewater—A review. GreenSustain Chemical, 3 (2): 89–121. doi:10.4236/

720gsc.2013.32013.

12 S. M. SAFWAT ET AL.