Hydrometallurgy, 26 ( 1991 ) 115-133 115 Elsevier Science Publ ishers B.V., Ams te rdam

The performance of a 500 Amp rotating cylinder electrode reactor. Part 2" Batch recirculation

studies and overall mass transport

D. R o b i n s o n a'* a n d F .C. W a l s h b'*'* aSteetley Engineering Ltd., P.O. Box 20, Brierly Hill, West Midlands, UK

bDepartment of Pure and Applied Chemistry, University of Strathclyde, Glasgow, U.K.

(Received March 15, 1990; revision accepted June 2, 1990)

ABSTRACT

Robinson, D. and Walsh, F.C., 1991. The performance of a 500 Amp rotating cylinder electrode re- actor. Part 2: Batch recirculation and overall mass transport. Hydrometallurgy, 26: 000-000.

The performance of a 500 A pilot plant Rotating Cylinder Electrode Reactor (RCER) is examined, in the batch recirculation mode, for copper removal from an acid sulphate liquor. The RCER involved a cathode of diameter 0.258 m and length 0.254 m (electroactive area 0.198 m 2) which was rotated at 750 m i n - ~.

Electrolysis conditions were as follows. Reservoir copper level: 0-500 mg dm -3 in 0.5 mol dm -3 H2SO4 at 35 ° C; reactor outlet copper concentration: 4-255 mg dm-3. Under pseudo-potentiostatic control of the cathode, copper concentration, current and cell voltage were monitored for 180 min while recirculating a batch of volume 436 dm -3 at a steady flow rate of 25 dm 3 m i n - ~.

It is shown that, under the experimental conditions used, the reactor system could be modelled as a continuous stirred tank reactor (CSTR) involving a mass transport controlled reaction, in the batch recycle mode. Deviations from predicted behaviour are discussed in the case of the concentration and current histories.

In addition to the average mass transport coefficient (0.22 cm s- l ), the cumulative cathode current efficiency (75-79%) and normalised space velocity (19 m 3 m -3 h - l for a fractional conversion of 0.9 ) are calculated as "figures of meri t" which help to characterise the reactor's performance.

It is shown that a generalised, empirical mass transport correlation for single pass and batch recycle trials may be reduced to simplified expressions which describe the relative reactor performance at different temperatures and rotation rates.

1. I N T R O D U C T I O N

In Part 1 of this paper [ 1 ] cathode potential against cell current and single pass data were presented for a 500 A pilot plant rotating cylinder electrode reactor.

*Now at: ICI plc, Chemicals and Polymers Limited, P.O. Box 8, The Heath, Runcorn, Cheshire WA7 4QD. **Author for correspondence. Present address: D e p a r t m e n t of Chemistry, Por t smouth Poly- technic, Whi te Swan Road, Po r t smou th PO1 2DT.

0 3 0 4 - 3 8 6 X / 9 1 / $ 0 3 . 5 0 © 1991 - - Elsevier Science Publ ishers B.V.

1 16 D. ROBINSON AND F.C. WALSH

[out , f

V T

Ein,o ~ Cin,t

Cin ,f )

••[[L A =71d I

K L

Vcelt

Fig. 1. Diagram of the batch recirculation mode of operation for a RCER, showing the flow loop between the catholyte and reservoir.

Data from the same reactor, in the batch recycle mode of operation, on the removal of copper, via cathodic deposition from 0.5 mol dm -3 H2SO 4 is con- sidered here. This mode of operation (Fig. 1 ) provides important data on fundamental laboratory studies and practical plant operation. Reactor per- formance, based on measurements of cathode current efficiency and mass transport, is examined for a wide range of copper concentrations. The batch recycle mode [2,3 ] can also be used for practical operations which aim at the complete removal of dissolved copper; for example, some effluent control op- erations and the treatment of spent process liquors.

2. EXPERIMENTAL M E T H O D

The electrochemical reactor construction, together with its electrical and flow systems have already been described in Part 1. To imitate batch recir- culation decay, additions of copper concentrate to the reservoir were stopped. The dissolved copper concentration decreased with time due to its cathodic removal in the RCER. Measurements of Ci. and Cout were made at frequent intervals for a period of 170 min. Electrolysis conditions were fixed so that Q=25 dm 3 min -~, T=35°C, Vv=436 dm 3 and to=730 min -1. The initial reservoir concentration was 500 mg dm-3.

PERFORMANCE OF A 500 AMP RCER PART 2 | 1 7

3. CONCENTRATION TRIALS IN BATCH RECYCLE MODE

3.1 Concentration histories

In the absence of reservoir dosing, the system behaved as a CSTR under mass transport control in the batch recycle mode (Fig. 1 ). Under these cir- cumstances, the copper concentrat ion histories at the terminals of the RCER may be described by:

1

This equation is an approximation [ 3 ] but has been shown to describe the behaviour of systems such as the experimental RCER adequately [2 ]. The conditions necessary for this to be valid include:

(a) A well-stirred reservoir. In practice a bypass loop in the pump system provided effective mixing.

(b) Vceu << VT. In practice 18.7 << 436 dm 3, (table 3 [ 1 ] ). (c) Ideal CSTR behaviour. Taking logarithms of eq. ( 1 ):

1 ln Ci,,t=ln C, n,O--[~T (1--1+ KLA/Q) ] (2)

Equation (2) predicts that a plot of In Cm,t versus t should be linear, having an intercept of In Cin,0 on the vertical axis, and of slope r where:

Q 1 r +KLA/Q) ( 3 ) =w(l-1

An overall value Of Kk may be obtained, from a simple rearrangement, as:

KL=AQ( 1 1 1) (4) + (rVT/Q) Recalling the relationship between Cin and Co,~ (eq. (7) [ 1 ] ), the reactor outlet concentration history may be described as follows:

I Cou~,t - zFQ- Cin.t ( 5 )

or:

Cout,, = Cout.O exp r ( 6 )

or taking natural logarithms:

In Co.t.t = In Cout,O + r ( 7 )

] | 8 D. ROBINSON AND F.C. WALSH

Thus both In Cout,t and In Cin,t should decrease in a linear fashion with time with a constant separation, which is given by the logarithmic version of eq. (7) [1]att imet:

In Cin,t-ln Co~,,~=ln ~ (8)

C/mg dm -3

103 i 1 I I I I I I

10 2

101

I00 l

0 140

t / min

°i

I I I I I 1 I ] 20 40 60 80 100 120 160 180

Fig. 2. Copper concentration histories during a batch recirculation experiment; • = Gin , 0 = Cout;

Q = 2 5 dm 3 m i n - l ; T = 3 5 ° C ; VT=436 dm3; o9= 750 min -~.

PERFORMANCE OF A 500 AMP RCER PART 2 1 1 9

As Fig. 2 indicates, this behaviour is observed for 0 min< t< 80 min. For longer times (and hence lower Cout values, Cout < 20 mg dm-3) , the slope of the curves progressively decreases. This behaviour may be attributed to a pro- gressive change in the rate-determining process; away from complete mass transport control and towards chemical effects. A contributory factor may be the redissolution of copper, which would significantly increase Cout at low levels of dissolved copper. From Fig. 2, the slopes at t< 80 rain may be used

IL/A 10 3

10'2

101

1 I I I I I I I

100 I I I I I I I I 20 40 60 80 100 120 1z,0 160

t / rain

Fig . 3. C e l l c u r r e n t v e r s u s t i m e r e l a t i o n s h i p c o r r e s p o n d i n g t o Fig . 2.

80

120 D. ROBINSON AND F.C. WALSH

to calculate KL, according to eq. ( 3 ). A least squares analysis of the data gave a KL value of 0,29 cm s-1 for both the C~n and Cout curves.

If the logarithmic form of eq. ( 12 ) [ 1 ] is taken into consideration, then eq. (8) may be written:

In Cin,t- ln Cout,t=ln (1 +KLA/Q) (9)

Thus the separation of the In Ci, and In Cout curves of Fig. 2 should be In ( 1 +KLA/Q), which is a constant.

The limiting current for copper deposition, Ii may be calculated according to eqs. (8) and (9) (in [ 1 ] ) as before. Fig. 3 shows a semilogarithmic plot OflL versus time. 1L should decay in an analogous fashion to Coot, as required byeq. (3) [ l ] .

IL/A &O0

300

200

100

• o

50 100 150 200 250 300

Cou f / mg dm -3

Fig. 4. Limit ing current as a funct ion of outlet copper concentra t ion: batch recirculat ion mode. o9= 750 r a in - ) ; T = 3 5 ° C .

PERFORMANCE OF A 500 AMP RCER PART 2

3.2 Current-time relationships

121

Expressions describing the l imit ing current history may be obta ined by combin ing eqs. (14) and ( 12 ) in [ 1 ] to give:

Can - Cou, =fR = 1 Cin 1 I+KLA/Q (10)

The l imit ing current writ ten in terms of the concentra t ion change across the reactor (via eq. (7) in [ 1 ] ) becomes:

IL=zFQ ( f i n - Cout) (11)

A combina t ion of eqs. (10) and ( 11 ) yields:

1 IL=zFQC, n(1 I+I~A/Q) (12)

Equat ion ( 12 ) may be writ ten for the specific t imes of 0 and t:

IL,o= ZFQC~n,O( 1 + KLA/ Q ) ( 13 )

IL,~=zFQCin,t( 1 +KLA/Q) (14)

Substi tut ing Cm f rom eq. ( 1 ) into (14) gives:

IL,t = zFQ( 1 + KLA/Q)Cin,o e x p - rt (15)

where r has already been defined by eq. (3) . Taking natural logari thms of eq. ( 15 ):

In Ic,t= [In Cin,O zFQ(1 +KLA/Q)] --rt (16)

I feq. ( 1 3 ) is taken into considerat ion, this may be rewrit ten simply as:

I n / c a = In IL,O - - rt ( 17 )

A plot of In IL,t versus t ime should therefore be linear, having a slope r and an intercept of In IL,O-

Figure 3 indicates that such behaviour is valid when t< 80 min. F rom the slope of t < 80 min, KL is calculated - via eq. ( 17 ) - as 0.29 em s- 1.

A plot OflL as a funct ion of Cout was linear (Fig. 4), as expected from eq. ( 4 ) [ 1 ]. F rom the slope the average KL was calculated as 0.22 cm s - i.

Figure 5 shows the decline of cell voltage and cell current with time.

1 2 2 D. R O B I N S O N A N D F.C. W A L S H

- Ecell/V 1 0 / I I I I I I I i

8

6 Ca)

z,

2 • • • a - -

0 I [ i 1 I I I I I

I/A I I I I r i I I - -

3 0 0

2 0 0 I -- (b)

100 - --

0 / V vs SC E ~E c /

I [ + I I I l n - -

Ec

450500 ~ ) [ c )

&O0 1 I I I I _ _ t I I _ _

20 40 60 80 100 120 II,0 160 180 t / m i n

Fig. 5. Measured electrolysis parameters as a function of time. Batch recirculation mode under pseudo-potentiostatic control. (Common time axis.) (a) The cell voltage, Ece.; (b) the cell current, I; (c) the cathode potential, Ec; T= 35 °C; o9= 750 rain-1.

4. DISCUSSION

4.1 Mass transport and conversion data

In o r d e r to r a t iona l i se the m a g n i t u d e o f KL a n d its con t ro l by selected ex-

PERFORMANCE OF A 500 AMP RCER PART 2 123

perimental variables, it is necessary to generate expressions which describe the mass transport controlled deposition of copper in a RCER.

A generalised approach [ 4-15 ] may be used in which a dimensionless cor- relation of the following form is considered:

KL b S t = ~ = a R e Sc c (18)

Assuming, in accordance with Holland [ 8 ], that a and c have fixed values of 0.079 a n d - 0.644:

St = 0.079 Re b Sc -0"644 (19)

For small, hydrodynamically smooth, RCEs, it has been shown that b = - 0.30 [ 14,15 ]. A modified Chil ton-Colburn type of expression may then be used to describe mass transport:

sJD = S t S c 0"644 = 0.079 Re-°3° (20)

For the special case of metal powder deposition, Holland [ 8 ] has assigned a very different value to b. An exact value cannot be stated as it depends on the metal, the electrolyte composition, the electrolysis conditions (including temperature and cathode type/surface finish) and cell geometry [6-8,16]. For copper powder deposition from acid sulphate liquors at 60 °C (in a vari- ety of RCERs ), Holland [ 8 ] has assigned an averaged value: b = - 0.08. Thus:

pjo=Sl S¢°644=0 .079 R e - ° °8 (21)

The experimental data obtained in the present study are plotted in the form o f j o against Re on log-log axes (Fig. 6); eqs. (20) and (21) have been su- perimposed. Several comments may be made about this figure:

( 1 ) The experimental data concern only a limited range of Re (and hence a limited jD range also).

(2) For any given value of Re, there is an appreciable variation in the val- ues ofjD. While some of this is due to experimental scatter, the large part of the variation may be attributed to an inherent degree of randomness in the nature of the metal powder deposition.

( 3 ) The data fall relatively near the line described by eq. (21 ). (4) In comparison with the line describing mass transport to a small, hy-

drodynamically smooth RCE, the present data involve a much higher range of Re values.

(5) The experimental data show markedly enhanced mass transport in comparison with eq. (20); this enhancement is increased at higher Re values.

The enhancement in the mass transport may be attributed to an increase in both the electroactive area for deposition and the hydrodynamic shear due to roughness formation. It is convenient, for the purposes of calculation, to as- sume that no change in surface area occurs. This is equivalent to assuming

124 D. ROBINSON AND F.C. WALSH

103 J'l] = 103 S t Sc 0 6 6 4

101 i I i i i i I I I I I I I I

10 0

10 -1

H O L L A N D

E T W

/~ = 22 . I 2 6.( 28,5

10 -2 i i J ~ , , I , I J J ~ , ~ I ~

10 5 10 6 10 7 R e

Fig. 6. Overall mass transport correlation (modified Chilton-Colburn factor versus rotational Reynolds number) log-log plot. ETW=eq. (20) after Eisenberg, Tobias and Wilke [ 14,15 ] (the highest Re was approximately 2.5 X 10s). Holland = eq. (21), (the lowest Re was approxi- mately 2.5)< 105).

that the enhancement in the observed value o f I is due solely to an improved KL i.e., A is constant in eq. ( 1 ) [ 1 ]. This approach is consistent with that adopted e lsewhere [ 1 1 -13 ]. The degree o f enhancement o f mass transport due to metal powder deposit ion:

PERFORMANCE OF A 500 AMP RCER PART 2 1 25

Re-°°8 p J D ~ReO.22 (22)

= sJD" -Re-°3° -

may be quantified by a comparison of eqs. (20) and (21 ). As indicated in Fig. 6, 2 has approximate values in the range 22-28 for the

present data. The variation in 2 at a given Re strongly suggests the need for extensive pilot trials on any new reactor to characterise the precise range of JD and hence the reactor performance as described by KL andfR.

Equation (21) is empirical and may be considered to be a useful (if only approximate ) expression for a wide range of experimental conditions. It may now be reduced to several simplified forms. For example, the mass transport coefficient may be expressed as:

KL=0.079 URe -°'°s Sc -0"644 (23)

Thus, data may be correlated by plotting KL as a function of the right hand side of equation (23). The result should be a straight line through the origin. Such a plot is a t tempted in Fig. 7, which once again indicates the variation in KL for a particular value of Re.

In the present work, expressions showing the effect of co and T are particu- larly relevant. For a constant solution composit ion and temperature, v and D are constant and therefore Sc is constant. Equation (23) then simplifies to:

KL ~C U R e - ° °8 (24)

and as Re= Ud/v, for constant d:

KL(x: U 0"92 (25)

Thus, comparing KL values at the peripheral velocities of U2 and Ul (cor- responding to 0) 2 and 0)! ):

2KL {U2"~ 0"92

a=~K~k= k ~ - J (26)

I f o) 2 = 750 m i n - 1 and 0)1 = 240 m i n - ~ are compared then eq. ( 26 ) predicts a = 2.85. In practice, the value was 2.6 _+ 0.3.

If the effects of temperature are considered it is seen that this variable ef- fects v and D in a complex fashion; it therefore influences Re and particularly Sc. For a fixed rotational speed, eq. (23) reduces to:

KL ~ R e - ° ° 8 Sc -0.644 (27)

and the relative mass transport at temperatures T2 and T1 may be calculated via:

fl 2KL T2Re -°°8 7-2 Sc0"644 = ~ L - - TI Re-°°ST, S£°644 ( 2 8 )

126

K L /crn s -1 0 . 6 - -

0 , 5

0,4 - -

0.3 --

0,2 --

0.1

0 0

I [

,41'./" /

- - I I / i T / T H E O R Y

7

4 6 9 ~

500

920

1688

I 1 I I I l 0.1 0.2 0.3 0.4 0.5 0.6 0.7

x / c m s -1

D. ROBINSON AND F.C. WALSH

Fig. 7. Mass transport coefficient as a function ofx where x=0.079 U, Re-O°8, Sc-O.644 Solid line = prediction from eq. (23).

This gives a value o f 2.25, which is slightly higher than the exper imenta l value o f 2.0.

4.2 Other important data

The ca thode cur ren t eff ic iency for coppe r r emova l via depos i t ion has al- ready been desc r ibed by eqs. ( 10 ) and ( 1 1 ) [ 1 ]. A cumula t ive value o f ¢~ at

PERFORMANCE OF A 500 AMP RCER PART 2 127

l t / A h

220 I I I I / /~

THE 200 - -

180

'160

140

120

100

80

60

40

20

o I I I 1 I I 0 100 200 300 400 500 600

8 E t / mg dm -3

700

Fig. 8. Electrical charge versus overall concentration change, batch recirculation trials. V v = 4 3 6 dm3; T = 3 5 ° C ; ~o= 750 r n i n - L

time t may be expressed via:

It= zFACVT (29) ~cum

Therefore, a plot of / t against AC should be linear, pass through the origin and have a slope of 2 FVT, if ~ is unity. Figure 8 shows such a plot for data ob- tained in the batch recirculation mode. Data deviate significantly from the theoretical line only at high AC values (and hence for longer periods of time) due to two possible effects:

128 D. ROBINSON AND F.C. WALSH

IL/A 350

300

250

200

1 50

100

50

I r I r I r / - / I /

/ . / c o o

, I I I I I I 50 100 150 200 250 300 350

i /A gO0

Fig. 9. Limiting current for copper removal as a function of cell current, batch recirculation trials. Solid line = unity interval current efficiency; limiting currents have been calculated f rom

interval Cout values.

( 1 ) hydrogen evolut ion was a significant secondary reaction; ( 2 ) redissolution o f active copper powder occurred in the acidic catholyte

due to corrosion:

Cu = Cu 2 ÷ + 2 e - anodic corrosion reaction ( 30 )

½02 + 2H ÷ + 2 e - = H 2 0 cathodic corrosion reaction ( 31 )

Cu + ½ 02 + 2H ÷ = Cu 2 ÷ + H 2 0 overall corrosion reaction ( 32 )

The second effect would be expected to be particularly important at low Cou t levels (i.e. over a longer period o f t ime and higher values o f AC) .

A more precise value for ~ may be calculated by considering the interval values:

PERFORMANCE OF A 500 AMP RCER PART 2 1 29

zFACVT I A t = - - (33)

~int

Oint=int~ -Cu (34)

Figure 9 shows a plot Ofintlcu against I; the data points all fall below the line corresponding to q~= 1, with the greatest deviations occurring at high currents.

An alternative way of using current efficiency data is shown in Fig. 10 where ~int is plotted as a function of Cout. Significant variation occurs at a given Coot, but the overall trend towards low ~)int values at low Corn is clear. Under exper-

I I 1 I

¢in~

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0,3

0.2

0.1

I I I I I 0 50 100 150 200 2 50 300

Cou t / mg dm -3

Fig. 10. Interval current efficiency versus outlet copper concentration, batch recirculation data.

130 D. ROBINSON AND F.C. WALSH

imental conditions, values of 0 i n t > 0 . 5 w e r e only realised at Cou,>> 30 mg dm -3.

Several other "figures of merit" may be calculated in order to quantify the reactor performance. A simple parameter which can act as a measure of com- pactness is the projected cathode area per overall unit cell volume:

A 1980 As-- V - 4000=0.05 cm -1 (35)

Under idealised conditions, with the inter-electrode gap reduced to zero:

zMI 4 As--*zc( d/2 )2l- d

In the present case, d=24.8 and As~0.16 cm - l . In practice, the required anolyte and catholyte compartments occupy a significant space, which is re- flected in the experimental As value of 0.05 cm - l .

The electrolytic power consumption per unit mass of copper deposit, E~, may be expressed via:

EceHI At E s - (36)

Am

From Faraday's laws:

Am =Mlcu At/zF ( 37 )

and:

E S ~ "

E s =

Ecell I z F IcuM (38)

Ecell Z F om (39)

The value of 0 may be calculated from conversion data. Realising that:

Am/t=ACQ (40)

Then:

Ecell I Es= (41)

Q(C~n-Cout)

0 may be taken to be either an interval or cumulative value. For the single pass reactor trials, in the range 100< Cout< 175 mg dm -3 (and using 0cure) Es -8 .3 _+ 0.6 kWh kg-1. This figure may appear high in comparison to con- ventional copper electrowinning cells, where 2 kWh kg-1 would be a more typical figure. It should be recalled, however, that parallel plate electrowin- ning cells utilise relatively pure electrolytes with high levels of dissolved cop- per (typically 20-60 g dm-3) ; and that copper removal is not continuous.

P E R F O R M A N C E O F A 500 AMP RCER PART 2 l 3 1

TABLE 1

The "figures of merit"

Parameter Value

0 ... . 75-79% (C,,,t 100-175 mg dm -3) A~ 0.05 c m - Es 8.3 kWh kg- l p~ 1 9 m 3 m 3 h - I

Note: these figures are strongly dependent upon the electrolysis conditions, particularly the con- centration of dissolved copper in the reactor and the cathode potential [ 18 ]. All single pass trials except As.

These conditions may be contrasted with the present reactor, where low cop- per levels can be treated with an acceptable current efficiency, and copper removal is continuous.

The performance of the RCER with regard to the treatment of liquor con- taining copper may be scrutinised using the "normalised space velocity" which has been formalised by Kreysa [ 17 ]:

I0 ( in) p n __ A C V T z F log1 o ~Cout/

Effectively, p~ refers to the number of volumes of liquor which can be treated in a unit volume of the reactor in unit time, with fR= 0.9. If the right hand side of eq. (42) is multiplied by 3600, the convenient units of m 3 m -3 h-1 result; a typical experimental value for single pass trials was 19 m 3 m-3 h - I

The various "figures of merit" are summarised in Table 1. These may serve as the basis for future comparisons with different reactors.

ACKNOWLEDGEMENTS

Much of the experimental work reported for Parts 1 and 2 of this paper was carried out at Ecological Engineering Ltd; the technology of this company has since been acquired by Steetley Engineering Ltd.

Valuable contributions to the experimental programme were made by Messrs. R.J. Phillips (mechanical engineering) and J.W. Mason (chemical analysis). Financial support was partly provided by the NRDC (now part of the British Technology Group ). The authors are grateful to Steetley Engineer- ing Ltd, for permission to publish and to Mrs M. Lynch for typing the manu- script. The proprietary rights for the Eco-Cell technology have recently been acquired by van Aspert bv (Consulting Engineers), Kastanjeweg 68,5401 JP Uden, The Netherlands.

132 D. ROBINSON AND F.C. WALSH

NOMENCLATURE

a,b,c As .4 f~ell

Cou, ('in,o Cin,t AC d D Ec E~ Ecell

Es A F 1 l(:u IL /L,O IL,t

~JD pJD KL I m M Q r t At T U t~r [~-ell Z

constants in eq. (18) projected cathode area per unit space occupied by the reactor projected cathode area ( = ndl) copper concentration in the reactor (cell) copper concentration at the reactor inlet copper concentration at the reactor outlet initial copper concentration in the reservoir copper concentration in the reservoir at time t concentration change diameter of rotating cylinder diffusion coefficient of cupric ions cathode potential versus SCE open-circuit cathode potential versus SCE cell voltage specific electrolytic energy consumption fractional conversion in the system Faraday Constant ( = 98485 A s mol- ~ ) c u r r e n t

current used in copper deposition limiting current for copper deposition limiting current at time zero limiting current at time t modified Chilton-Colburn factor for a smooth deposit modified Chilton-Colburn factor for a powder deposit mass transport coefficient effective length of cathode mass of copper molar mass of copper volumetric flowrate slope (defined by eq. (3)) time time interval temperature of catholyte reservoir peripheral velocity of rotating cylinder cathode effective volume of tank effective volume of reactor number of electrons

O~

B 2 ~int ~cum p~ P

defined by eq. (26) defined by eq. (28) defined by eq. (22) interval cathode current efficiency for copper deposition cumulative cathode current efficiency for copper deposition normalised space velocity kinematic viscosity of electrolyte

R c

Sc St

Reynolds Number ( = Ud/v) Schmidt Number ( = v/D) Stanton Number ( = KL/U)

PERFORMANCE OF A 500 AMP RCER PART 2 [ 33

REFERENCES

1 Robinson, D. and Walsh, F.C., The performance of a 500 Amp rotating cylinder electrode reactor. Part 1: Current-potential data and single pass studies. Hydrometallurgy, 26 ( 1991 ) 93-114.

2 Gabe, D.R. and Walsh, F.C., In: Proc. Am. Inst. Chem. Eng. Syrup. (Cleveland, Ohio). Electrochem. Soc. Symp. Ser. 83-12 (1982), pp. 314-366.

3 Walker, A.T.S. and Wragg, A.A., Electrochim. Acta, 22 ( 1977): 1129-1134. 4 Gabe, D.R., J. Appl. Electrochem., 4 ( 1974): 91-108. 5 Gabe, D.R. and Walsh, F.C., J. Appl. Electrochem., 13 ( 1983): 3-22. 6 Holland, F.S.,Brit. Pat. 1444367 (1976). 7 Holland, F.S., US Pat. 4028199 (1977). 8 Holland, F.S.,Chem. lnd. (London) (1978):453. 9 Gabe, D.R. and Walsh, F.C., Proe. Am. Inst. Chem. Eng. Symp. (Cleveland, Ohio), Elec-

trochem. Soc. Symp. Ser. 83-12 (1982), pp. 367-383. 10 Gardner, N.A. and Walsh, F.C., In: R.E. White (Editor), Electrochemical Cell Design,

Plenum Press, New York (1984), pp. 225-258. 11 Gabe, D.R. and Walsh, F.C., J. Appl. Electrochem., 14 ( 1984): 555-564. 12 Gabe, D.R. and Walsh, F.C., J. Appl. Electrochem., 14 ( 1984):565-572. 13 Gabe, D.R. and Walsh, F.C., J. Appl. Electrochem., 15 ( 1985): 807-824. 14 Eisenberg, M.,Tobias, C.W. andWilke, C.R.,Chem. Eng. Prog. Symp. Ser.,51 (1955): 1-

15. 15 Eisenberg, M., Tobias, C.W. and Wilke, C.R., J. Electrochem. Soc., 101 ( 1954): 306-319. 16 Holland, F.S., Robinson, D. and Walsh, F.C. (1979) (unpubl.). 17 Kreysa, G., Electrochim. Acta, 26 (1981): 1693-1694. 18 Pletcher, D. and Walsh, F.C., Industrial Electrochemistry. Chapman and Hall, London,

2nd ed. (1990).