Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.16 No.1 (March 2015) 13- 20  

ISSN: 1997-4884 

 
 
 
 

Electrochemical removal of copper from synthetic wastewater using 

rotating cylinder electrode 
 

Qasim J. M. Slaiman, *Cecilia K. Haweel and Suha A. Mohammed 

*Chemical Engineering Department, University of Bagdad 

 

Abstract  

   The performance of a batch undivided electrochemical reactor with a rotating 

cylinder electrode of woven-wire (60 mesh size), stainless steel 316, is examined for 

the removal of copper from synthetic solution of o.5 M sodium chloride containing 

125 ppm at pH ≈ 3.5. The effect of total applied current, rotation speed on the figures 

of merit of the reactor is analyzed. For an applied current of 300 mA at 100 rpm, the 

copper concentration decreased from 125 to       mg l
-1

 after 60 min of electrolysis 

with a specific energy consumption of 1.75 kWh kg
-1

 and a normalized space velocity 

of 1.62 h
-1

. The change in concentration was higher when the total applied currents 

were increased because of the turbulence-promoting action of the hydrogen evolution. 

The results suggest that the applied current must represent a compromise between the 

increase in space time yield or normalized space velocity and the increase in the 

specific energy consumption. 

 

Key Words: Electrochemical effluent treatment, rotating cylinder electrode, copper 

removal  

 

 
Introduction 

   Of all the natural resources, water is 

unarguably the most essential and 

precious. Life began in water and life 

is nurtured with water. It is a universal 

solvent and as a solvent, it provides the 

ionic balance and nutrients [1], and 

supports all forms of life. So that any 

pollution in water can be a major 

problem spatially when the pollutants 

are heavy metal ions, although heavy 

metals are natural components of the 

environment but when their 

concentrations increase more than 

normal levels they become potentially 

hazardous [2]. At the last decades, the 

problem has extended due to the 

increasing in industries and the wars 

that there effect keep on many years. 

Heavy metals are elements having 

atomic weights between 63.5 and 

200.6, and a specific gravity greater 

than 5.0 [3]. Copper is an essential 

element needed for human and other 

living organisms, which primarily 

involves several proteins and enzymes. 

Copper is used to make electrical 

wiring, pipes, valves, fittings, coins, 

cooking utensils and building 

materials. It is present in munitions, 

alloys (brass, bronze) and coatings. 

Copper compounds are used also in 

fungicides, algicides, insecticides and 

wood preservatives and in 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 

University of Baghdad 
College of Engineering 



 Electrochemical removal of copper from synthetic wastewater using rotating cylinder electrode 

 
 

  

14                                       IJCPE Vol.16 No.1 (March 2015)             -Available online at: www.iasj.net 
 

electroplating, azo dye manufacture, 

engraving, lithography, petroleum 

refining and pyrotechnics. Copper 

compounds, can be added to fertilizers 

and animal feeds as a nutrient to 

support plant and animal growth. 

Deficiency of copper causes 

demineralization of bones, anemia, 

fragility of arteries, and discoloration 

of skin as well as hair. High 

concentration of copper (above 3.0 

mg/l) in water may lead to 

accumulation of copper in liver and 

lenticular nucleus of brain. Ultimately, 

it may cause hepatic cirrhosis and brain 

necrosis. Renal damage may also occur 

due to accumulation of copper in 

kidney by means of consumption of 

water with high copper concentration 

in excess of permissible limit [4]. 

Wastewaters from metal finishing, 

textile industries, electronics industry 

or washing effluents for remediation of 

soil contaminated with copper may 

contain up to 500 mg/L copper, which, 

depending on the worldwide 

environmental regulations and must be 

controlled to a permitted level before 

being discharged into the environment 

[5]. Where, the permissible limit of 

copper in sources of drinking water 

just like rivers is between 1.5 to 2 

mg/L according to the EU [6]. 

   The electricity has been used to 

treat water firstly in UK in 1889 [7]. 

Electrochemical methods involve the 

plating-out of metal ions on a cathode 

surface and can recover metals in the 

elemental metal state. Electrochemical 

wastewater technologies involve 

relatively large capital utilization. 

However, with the stringent 

environmental regulations regarding 

the wastewater discharge, 

electrochemical technologies have 

regained their importance worldwide 

during the past two decades [8]. The 

applications of electrochemical 

technology in environmental treatment 

are a clean technology and the only 

processes have the ability to recycle 

materials.  

   Because of the rate of the 

electrodeposition was limited by mass-

transport problems hydrodynamic 

electrodes are developed. 

Hydrodynamic electrodes are 

electrodes, which function in a regime 

of forced convection. The advantage of 

these electrodes is increased transport 

of electroactive species to the 

electrode, leading to higher currents 

and thence a greater sensitivity and 

reproducibility. Most of the 

applications of these electrodes are in 

steady-state conditions, i.e., constant 

forced convection and constant applied 

potential or current [9]. Electrodes 

have been rotated at least since 1905 to 

provide some quantitative control of 

solution conviction [10]. Recently, 

some authors have focused attention on 

the electrolytic treatment of copper; 

Reade et al. [11] studied the removal of 

cadmium and copper with a reticulated 

vitreous carbon rotating cylinder 

electrode. A decrease in cadmium 

concentration from 56 ppm to less than 

1 ppm was reported. In a previous 

paper from this laboratory [12] it was 

reported that a packed bed rotating 

cylinder electrode of woven wire 

meshes presents mass transport 

coefficients three times higher than 

those obtained with smooth electrodes 

because of the turbulence-promoting 

action of the meshes. 

   The present study focused on the 

analysis of the behavior of an 

undivided electrochemical reactor with 

a rotating packed bed electrode of 

woven wire meshes for the removal of 

copper and the study of the process 

variables, such as rotation speed, total 

applied currents on the ‘figures of 

merit’ of  the reactor. 
 

 



Qasim J. M. Slaiman, Cecilia K. Haweel and Suha A. Mohammed 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.1 (March 2015)                                15 
 

Experimental Work 
   The experiments were performed in an 

undivided batch reactor, is consisted of 

three electrodes and placed in 2l beaker 

at which the electrolyte 900 ml volume 

has been treated. Cathode electrode 

was used in dimensions as 3.5, 3 cm 

diameter and long respectively. The 

lower part of the electrode was open 

but the upper part was joined to a 

Teflon sleeve in order to orientate the 

electrolyte flow through the mesh. A 

perforated Teflon disc was used on the 

top of the working electrode sleeve, 

centrally positioned, where Teflon 

shaft was passed through it, which is 

used as supporting for the 

electrochemical cell and to distribute 

the electrical connections to the 

electrodes. Four planer graphite anodes 

(10×0.7×5 cm), fixed in Teflon disc at 

the bottom of the anode plates and they 

were fixed from the top with the 

perforated Teflon disc, which is proved 

a good support. The gap between the 

cathode and anode plates was 1.5 cm 

and calomel reference. Figure 1 depicts 

schematically the complete 

experimental arrangement. 

    

 
Fig. 1, General view of the reactor,(1) 

beaker 2l,(2) electrical mixer,(3) 

reference electrode,(4) counter 

electrode,(5) anode electrode,(6) 

digital voltmeter,(7) electrical 

connecter,(8) digital ammeter,(9) 

resistance box,(10) power supply. 
 

   All solutions were prepared using 

AnalaR grade chemicals and distilled 

water. Cupric ion solutions were 

prepared by dissolving copper chloride 

in an aqueous solution of 0.50 NaCl at 

pH 3.5. 

   The concentration of copper ions was 

monitored by atomic absorption 

analysis using an air–acetylene flame, 

in order to determine the variation of 

concentration with time and the 

differential concentration decrease. 

From these data the current efficiency, 

the space time yield, the normalized 

space velocity and the specific energy 

consumption were intended. 
 

The anodic reaction was oxygen 

evolution: 
            

                          ...(1) 

 

The main cathodic reaction is: 
                 

                     ...(2) 

 

and the side reactions were the 

Hydrogen evolution: 
      

        
                          ...(3) 

 

Theory 

   For a rotating cylinder electrode the 

electrolyte is assumed to be well-

mixed at all times. Thus, for a batch 

reactor in the potential range where the 

tin deposition is mass-transfer 

controlled, the change of concentration 

with time is given by [13]. 

 
 ( )   ( )    (     )                     ….(4) 

 

   Consequently, the mass-transfer 

coefficient has to be evaluated in order 

to discuss the results obtained 

experimentally. 

   The fractional conversion and the 

accumulative current  efficiency as a 

function of time are given by, [13,14] 
 

 ( )        (     )                          ….(5) 
and 

 ( )  
     ( ) ( )

 ∫  ( )  
 
 

                                  …..(6) 



 Electrochemical removal of copper from synthetic wastewater using rotating cylinder electrode 

 
 

  

16                                       IJCPE Vol.16 No.1 (March 2015)             -Available online at: www.iasj.net 
 

   Other ‘figures of merit’ used to 

compare the performance of the 

electrochemical reactor are the mean 

value of the space time yield, the 

normalized space velocity and the 

specific energy consumption, which 

were calculated with the following 

equations: 

     ( )  
 ( ) ( )

 
                                  ….(7) 

 

  ( )  
       ( ) 

      
                                      ….(8) 

 

And 

 

  ( )  
∫  ( ) ( )  
 
 

  ( ) ( )
                                   ….(9) 

Results and Discussion 

   Figure 2-A shows the copper 

concentration as a function of time at 

different applied current. For a given 

applied current, there is a pronounced 

decrease in concentration during the 

first stages of the experiments, but at 

longer times, the concentration 

approaches a constant value. A linear 

decay of copper concentration is 

observed clearly but at total applied 

current -250 and -300 mA, a deviation 

from linearity can be seen, and while at 

lower applied currents the decay is 

linear. When the concentration ramp 

linearly with time this means that the 

deposition is under mass transfer 

control, which is a theoretical 

expectation [15, 14], within the 

accuracy normally expected for this 

type of measurements. The 

experimental results, in general, are in 

close agreement with theoretical 

prediction mainly during the beginning 

of the experiments. Although the plots 

of normalized concentration of copper 

as a function of electrolysis time were 

apparently exponential, the expectation 

of linearity for the ln[c(t)/c(0)] against 

time plot was confirmed only for a 

portion of the curve, as shown in figure 

2- B . This behavior was also observed 

 in previous work as for copper [16], 

cadmium [14, 17], tin [13], and lead 

[18]. Where this deviation from 

linearity with time in the deposition of 

copper ions is due to the fact after half-

an-hour more than 90% of copper ions 

had been removed then reduction in the 

current efficiency can be expected. 

   Fig. 3 shows the normalize and the 

linearization of normalized 

concentration of copper as a function 

of time at different rotation speeds. It 

may be observed from figure 3-A that 

the normalized concentrations of the 

copper remain practically slightly 

unchanged throughout the electrolysis 

with different rotation speeds. 

Although in general there are 

reductions of concentrations with time, 

for longer time of deposition there is 

also a deviation from linearity, which 

can be noticed as in the decay 

concentration curves presented in     

Fig. (3). 

 

 
Fig. 2, (A.) Normalized concentration 

of copper (c(t) /co) as a function of 

time. (B) Linearization of normalized 



Qasim J. M. Slaiman, Cecilia K. Haweel and Suha A. Mohammed 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.1 (March 2015)                                17 
 

concentration as a function of time for 

different applied current 

 

 
Fig. 3, (A.) Normalized concentration 

of copper (c(t) /co) as a function of 

time. (B) Linearization of normalized 

concentration as a function of time for 

different rotation speeds. 

  

 
Fig. 4, Cumulative current efficiency 

as a function of time for different 

applied currents at constant rotation 

speed of 100 rpm 

 

   Fig. (4) shows typical curves of the 

accumulative current efficiency as a 

function of time at different total 

applied current. For a total applied 

current of 180 mA the current 

efficiency is close to 100% early in the 

experiment and decreases at higher 

times because the copper concentration 

decreases and the oxygen reduction 

predominates. For higher values of the 

total applied currents, hydrogen 

evolution possibly occurs as cathodic 

side reaction and lower values of 

current efficiencies are measured.  

 

   Fig. (5) and 6 show the mean value 

of the space time yield and the 

normalized space velocity as a function 

of the applied current where there was 

an increasing effect with increase in 

the total applied current can be noticed. 

 

 
Fig. 5, Mean value of the space time 

yield as a function of total applied 

currents at constant rotation speed of 

100 rpm 

 

   Fig. (7) shows the specific energy 

consumption as a function of time for 

different total applied currents. For a 

given applied current, as the solution 

becomes more dilute the current 

efficiency decreases and the energy 

consumption increases. The increase in 

Es when the total applied current 

increases can be attributed to a 

decrease in current efficiency because 

of the onset of hydrogen evolution. 

The specific energy consumption is in 

accordance with values previously 

reported [17, 19]. 

 



 Electrochemical removal of copper from synthetic wastewater using rotating cylinder electrode 

 
 

  

18                                       IJCPE Vol.16 No.1 (March 2015)             -Available online at: www.iasj.net 
 

 
Fig. 6, Normalized space velocity as a 

function of total applied currents at 

constant rotation speed of 100 rpm 

 

 
Fig. 7, Specific energy consumption 

as a function of time for different total 

applied currents at constant rotation 

speed of 100 rpm 

 

Conclusions 

   The following conclusions may be 

drawn: 

 

1. The copper removal from dilute 
aqueous solution can be performed 

efficiently in an electrochemical 

reactor with a three-dimensional 

rotating cylinder electrode of 

woven wire sheet. The total applied 

currents show an emphatic effect 

on the removal rate of copper and 

the increasing in rotation speed 

also increase the removal rate of 

copper. 

2. The copper concentration follows 
the expected theoretical behavior 

during the first stages of the 

experiment. 

3. Hydrogen evolution, as side 
cathodic reaction, is beneficial for 

tin removal because the turbulence 

promoting action increases the 

current for the main reaction and 

enhances the space time yield or 

the normalized space velocity. 

However, at the same time it is 

detrimental to the specific energy 

consumption because the current 

efficiency decreases.  

4. The process shows that the removal 
of copper from aqueous solutions 

does not require addition of 

chemical additives, which reduces 

the cost and makes the process 

efficient and with no chemical 

waste or sludge.  

 

Nomenclature 
ae   reactor specific surface area (m

-1
) 

As  electrode specific surface area (m
-1

) 

C  concentration (mg l
-1

 or kg m
-3

) 

Es  specific energy consumption (W s kg
-

1
 or kWh/kg) 

F  faradaic constant (C mol
-1

)= 96500 

Coulomb 

I  total current (A) 

k  mass-transfer coefficient (m s
-1

) 

M  atomic weight (g mol
-1

) 

sn  normalized space velocity (s
-1

 or h
-1

) 

t  time (min or s) 

U  cell voltage (V) 

V  effective electrolyte volume within 

the reactor 

(m
3
) 

x  fractional conversion 

Greek symbols 

   current efficiency (%) 
   kinematic viscosity (m

2
 s

-1
) 

     charge transfer of the electrode 
reaction  

      mean space time yield (kg m
-3

 s
-1

) 

 

 



Qasim J. M. Slaiman, Cecilia K. Haweel and Suha A. Mohammed 

 

-Available online at: www.iasj.net                    IJCPE Vol.16 No.1 (March 2015)                                19 
 

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20                                       IJCPE Vol.16 No.1 (March 2015)             -Available online at: www.iasj.net 
 

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