Chemistry for Sustainable Development 17 (2009) 341�350 341

Current Density and Solution Flow-Through Rate InfluenceUpon the Dynamics of Copper Deposition onto ElectrodesMade of Fibrous Carbon Materials

V. K. VARENTSOV1,2, S. I. YUSIN1,2 and V. I. VARENTSOVA1

1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences,Ul. Kutateladze 18, Novosibirsk 630128 (Russia)

E-mail: vvk@ngs.ru

2Novosibirsk State Technical University,Pr. K. Marksa 20, Novosibirsk 630092 (Russia)

(Received November 11, 2008; revised December 12, 2008)

Abstract

Dynamics of electrolytic copper extraction from sulphuric acid electrolyte onto fibrous carbon electrodeswith uniform distribution of initial electrical conductivity throughout the electrode thickness has beenstudied depending on the electrical conductivity of a fibrous carbon electrode, dimensional current density,the flow rate and the direction of solution feeding into the electrode as applied to the technology of copperextraction from the recovery bath of an automatic line of a galvanic manufacture.

Key words: fibrous carbon electrode, electrolysis, sulphuric acid solution, dynamics of copper deposition,current density, solution flow-through rate, deposit distribution

INTRODUCTION

Galvanic manufacture is one of the basicconsumers of the salts of nonferrous metalsand, as a consequence, a source of wastewa-ter containing toxic compounds of these met-als. A considerable part of toxic metal ions en-ters into wastewater with washing solutionsformed due to washing the products obtainedafter the operations of metallization, pickling,clarification, passivation, and etchings. Along-side with this a considerable amount of expen-sive reagents, including pure metal salts canbe lost [1, 2]. An efficient method allowing oneto neutralize simultaneously solutions, contain-ing toxic compounds of metals as well as toutilize and reuse extracted metals consists inperforming the electrolysis with cathodes madeof fibrous carbon materials (FCM) [2�8, 9]. Elec-trolysis with fibrous carbon electrodes (FCE) ismost efficient for the treatment of solutionscontaining metal ions with the concentration

amounting to several tens or several hundredsmilligrams per litre. Such content of metal ionsis just inherent in washing solutions.

The papers [2, 8, 9] validate and demon-strate a high efficiency of electrolysis with FCEin the process of metal extraction from wash-ing solutions of a recovery bath of automatedlines for metallizing workpieces as well as inthe manufacture of circuit boards. Their use ispromising since it provides solving the ques-tions of environmental safety and resourceeconomy in electroplating.

The conditions of electrolysis should providethe deposition of the highest possible amountof metal per FCM mass unit and a high effi-ciency of the process. The latter assumes theextraction of the metal introduced into a re-covery bath with pieces under washing for theperiod between two consecutive washing pro-cedures [2, 8, 9]. Due to the fact that the con-centration of metal ions in the recovery bathis maintained at certain level (100�200 mg/L)

342 V. K. VARENTSOV et al.

Fig. 1. Process flow diagram for electrolytic copper extraction from a recovery bath with closed cycle.

the metal current yield is high. The process flowdiagram is presented in Fig. 1 [2, 8].

The major factors influencing the efficiencyof the process are presented by FCM electricalconductivity, dimensional current density, rateand a direction of the solution flow rate throughthe bulk of an electrode, the electrode thick-ness. Studies on the effect of these factors aswell as determining the scale of their influenceupon parameters of the process represent oneof the primary goals of the theory and prac-tice of FCM application to the electrochemicaldeposition of metals from solutions.

The purpose of the present work consistedin studying the dynamics of electrochemicalcopper deposition onto electrodes made of FCMwithin a wide range of initial electrical con-ductivity of FCM composing an electrode de-pending on the current density, the rate and adirection of the solution flow rate through theelectrode bulk (at the fixed electrode thickness)as applied to electrochemical copper extractionfrom solutions of the recovery bath of a gal-vanic manufacture automatic line, as well as inthe estimation of changing the parameters de-scribing the electrolysis process in time depend-ing on the factors listed.

EXPERIMENTAL

The scheme of performing the experimentssimulates the process of metal electrolytic ex-traction from the solutions a recovery bath ofgalvanic manufactures [2, 8, 9]. The solutionexposed to electrolysis with the composition ofCu 0.16, H2SO4 25, (NH4)2SO4 80 (in g/L) andthe volume amounting to 250 mL circulated be-tween a tank with the solution (recovery bath)

and an electrolytic cell (electrolyser). The spe-cific electrical conductivity of the solution wasequal to 0.101 Sm/cm.

The constant concentration of ions of themetal under extraction in the tank maintainedwithin a certain narrow range ((0.16±0.03) g/L)was provided via the addition of a certain vol-ume of the basic copper-plating electrolyte withthe composition of Cu 15, H2SO4 25, (NH4)2SO4

80 (in g/L) every 5�15 min depending on therate of copper extraction. The total volume ofelectrolyte in the experiment remained constant.The concentration of copper ions in the solu-tion was determined employing the method ofdirect voltammetry with the use of a renew-able graphite microelectrode [10].

We studied electrochemical copper extrac-tion for electrodes with constant initial electri-cal conductivity all over the thickness depend-ing on the dimensional current density (500�2500 À/m2), flow-through rate of the solutionamounting to 0.1�1.0 mL/(s ⋅ cm2), initial elec-trical conductivity of FCM composing the elec-trode equal to (1.8 ⋅ 10�6�4.6 ⋅ 10�1 Sm/cm).

Electrochemical copper deposition was car-ried out under galvanostatic conditions. Cathodicpolarization was performed using a B5-47 di-rect current power supply. The scheme of theelectrolytic cell is described in [3, 4]. The cath-ode was 6 mm thick; it consisted of five FCMlayers, the anode represented a platinum wire,the lead represented a plate made of punchedtitanium covered with a thin layer of copper.We used the model of back solution feedinginto the electrode with a backside lead. The sideof the electrode adjoining to the punched leadwas denoted as a backside, whereas that be-ing nearby to the anode was considered as a

CURRENT DENSITY AND SOLUTION FLOW-THROUGH RATE INFLUENCE UPON THE DYNAMICS OF COPPER DEPOSITION ONTO ELECTRODES 343

TABLE 1

Characteristics of carbon fibrous materials

Material κ, Sm/cm r, µm Sp, cm2/cm3 ε Density, g/cm3

VNG-50 0.46 6.0 280 0.92 0.169

VINN-250 0.1 4.5 270 0.94 0.110

ANM 1.5 ⋅ 10�2 6.1 311 0.91 0.152

KNÌ-450 1.8 ⋅ 10�6 6.1 250 0.92 0.115

Carbonetkalon ÒK-24 0.41 3.5 750 0.87 0.265

Note. κ is specific electric conductivity of FCM; r is the radius of fibres composing the FCM; Sr is the reactionsurfacearea; ε is porosity.

frontal side. The electrode thickness was deter-mined basing on a possible electrode stack con-sisting of five layers being close to the highesttpossible electrode thickness used in the indus-try [2, 4, 6�9].

The parameters of FCM employed for com-posing are presented in Table 1. The methodsfor determining the values of specific electri-cal conductivity κ, reaction surface area Sr andporosity ε are described in [4]. The basic atten-tion in choosing the materials was given to theirspecific electrical conductivity.

Each FCM layer composing the electrode wasweighed using analytical balance before andafter electrolysis within the accuracy of 0.0001.After electrolysis, the electrode was washedwith distilled water being dried then in a dry-ing oven at the temperature of 80 îÑ to obtainconstant mass. The mass of metal deposited wasdetermined from the difference in FCM massbefore and after electrolysis.

The ratio between the mass of copper de-posit to the mass of FCM for each layer wascalculated according to the formula: d = mCu/mFCM; the ratio between the total deposit massand the mass of entire FCM was calculated ac-cording to the formula

5 5

Cu _ FCM _1 1

/i ii i

m m= =

∆ = ∑ ∑Here mCu_i is the mass of metal deposited ontoone layer of the electrode, g; mFCM_i is the massof the FCM layer before electrolysis. Alongsidewith these, the rate of copper deposition wascalculated in the following manner:U = mCu/(τSel)Thus the current yield of copper (CY) for totalelectrolysis time can be expressed as

5

Cu _ eq1

CY /(ii

m F JM=

τ)= ∑

where

5

Cu _1

ii

m=∑ is the total mass of copper,

deposited onto entire electrode, g; τ is electrol-ysis time, h; Sel is the sectional area of theelectrode, cm2; F is the Faraday number; J isthe intensity of current, A; Ìeq is the molarmass of copper equivalent, g/mol.

In order to estimate the uniformity of met-al distribution over the thickness of FCE weused a commonly known criterion such as theroot-mean-square deviation [11] which was cal-culated according to the formulas

5

Cu _ av Cu _1

15 i

i

m m=

= ∑

52

RMS Cu _ Cu _ av1

1 (5

)ii

H m m=

= −∑Here mCu_av is the average mass of copper,deposited onto the FCM layer, g; mCu_i is themass of copper on each FCM layer, g. All thecalculations were performed with the use ofMicrosoft Office Excel 2007.

RESULTS AND DISCUSSION

The efficiency of the process of metal elec-trochemical deposition onto FCE depends on theproperties of the electrode � solution system,the conditions of electrolysis, the electrode sys-tem design. In this connection, it is importantto establish the influence of the factors listedupon the process parameters for metal electro-chemical deposition onto FCE.

344 V. K. VARENTSOV et al.

Fig. 2. Copper mass to FCE mass ratio (mCu/mFCM) depending on the electrode thickness at the dimensional currentdensity 500 (a), 1500 (b) and 2500 A/m2 (c). Duration of electrolysis, min: 60 (1), 120 (2), 180 (3), 390 (4), 420 (5); B iselectrode backside; FCM is presented by VNG-50.

Fig. 3. Copper mass to FCE mass ratio (mCu/mFCM) depending on the electrode thickness at the dimensional currentdensity 500 (a), 1500 (b) and 2500 A/m2 (c). Duration of electrolysis, min: 60 (1), 120 (2), 180 (3), 420 (4), 540 (5); B iselectrode backside; FCM is presented by ANM.

Effect of initial FCE conductivity

Figures 2 and 3 demonstrate the results ofstudying the dynamics of copper deposit dis-tribution over electrode thickness for FCM withhigh and low initial electrical conductivity, re-spectively, at different values of the dimen-sional current density. Similar results were ob-tained for the electrodes made of all the FCMpresented in Table 1.

The analysis of the results has demonstrat-ed that the process of electrolysis results in

changing the distribution of copper deposit overthe electrode thickness inherent in each kindof FCM. At short electrolysis times and at thedimensional current density amounting to 1500and 2500 À/m2 metal is distributed over theelectrode thickness in a relatively homogeneousmanner. An increase in electrolysis time till themoment characterizing the �saturation� of theelectrode with metal (a considerable decreasein the solution flow rate through the electrodeor ceasing the solution flowing-through), canconsiderably change the �picture� of metal

CURRENT DENSITY AND SOLUTION FLOW-THROUGH RATE INFLUENCE UPON THE DYNAMICS OF COPPER DEPOSITION ONTO ELECTRODES 345

Fig. 4. Changing in the copper extraction rate U (à), the current yield of copper CY (b), root-mean-square deviationÍRMS (c) and the ratio between the mass of deposited copper and the mass of electrode mCu/mFCM (d) during theelectrochemical extraction of copper, depending on the dimensional current density (i) for various FCM: KNÌ-450Ì(1), ANM (2), Carbonetkalon ÒK-24 (3), VNG-50 (4). Electrolysis time, min: 420 (1, 2, 4) and 330 (3).

distribution over the electrode thickness as wellas the parameters of the electrolysis process.

Figure 4 demonstrates plots of varying thebasic parameters of the process of electrochem-ical copper extraction depending on the dimen-sional current density for various FCM. Thesedata concern the time of electrolysis determin-ing the electrode �saturation� by metal, repre-senting the integrated characteristics of exper-imental data. It is seen that at the dimensionalcurrent density amounting to 500 and 2500 À/m2

the parameters of the process differ to a con-siderable extent. A similar picture can be seenat the initial stage of electrolysis (less than30 min) for all the values of dimensional cur-rent densities under investigation.

Within the range of the dimensional cur-rent density values of 1000�1500 À/m2, irre-spective of specific electrical conductivity and

the reaction surface area of the material, wehave obtained sufficiently close values of CY,U, mCu/mFCM and HRMS for all the FCM underconsideration. Employing a calculation methodwith the use of known equations [3, 4, 12] ithas been demonstrated that the dimensionalcurrent density of (1250±200) À/m2 results inthe fact that the electrochemical copper depo-sition occurs with the limiting diffusion currentfor all (or almost all) the electrode thickness,which, to all appearance, causes the characterof curves presented in Fig. 4.

Data presented in Fig. 2, a, 3, a and 4, indi-cate that the individual properties of FCM (itsspecific electrical conductivity and the reactionsurface area) are most distinctly exhibited atsmall current density values.

The character of copper deposition onto fi-bres of FCM is presented in electron microscopic

346 V. K. VARENTSOV et al.

TABLE 2

Parameters of copper electrochemical deposition onto electrodes made of FCM. Dimensional current density

being equal to 1500 À/m2, the solution flow-through rate being of 0.4 mL/(s ⋅ cm2))

Material U, CY, % δmax δav ÍRMS τ, min

mg/(min ⋅ ñm2)

VNG-50 1.8 57.9 13.06 10.34 45.4 420

VINN-250 2.1 68.1 27.46 12.54 106.1 420

ANM 1.8 59.3 15.18 10.56 55.1 420

KNÌ-450Ì 1.7 55.4 13.75 9.81 38.5 420

Carbonetkalon ÒK-24 1.8 60.3 6.21 3.66 50.2 330

Fig. 5. Photomicrographs for FCM samples: a � before electrolysis (magn. 2500), b�d � with deposited copper afterelectrolysis for 5 min (b, magn. 2500), 60 min (c, magn. 1000) and 420 min (d, magn. 350).

images (Fig. 5) obtained with the help of JSMT-20 scanning electron microscope. It is seen thatat the initial stage of electrolysis, on the sur-face of FCM fibres there are nuclei formedthose gradually increase in size and overlapamong themselves forming continuous highlyconductive layer of a metal deposit. Alongsidewith this, growing metal islands filling the spacebetween fibres overlap to form additional path-

ways for current flowing. As a consequence,the electrical conductivity of separate parts ofthe electrode increases and, finally, the sameevent happens to the electrode as a whole. Theelectrical conductivity of the electrode to a con-siderable extent exceeds the electrical conduc-tivity of the solution, which results in chang-ing the character of copper deposit distribu-tion over the electrode thickness. According to

CURRENT DENSITY AND SOLUTION FLOW-THROUGH RATE INFLUENCE UPON THE DYNAMICS OF COPPER DEPOSITION ONTO ELECTRODES 347

the experimental data we have obtained earli-er, the formation of continuous deposit whichprovides high electrical conductivity of the elec-trode is observed with the deposition of about1�2 g/g of FCM for the �island� structure ofthe deposit and more than 0.2 g/g of FCM indeposition of a deposit in the form of a thinfilm. The relative mass of copper deposited ontovarious layers of the electrode, does not ex-ceed 3 g/g of FCM for the period less than120 min of electrolysis. Further, this ratio ex-ceeded 3 g/g of FCM to cause forming an elec-trode with high electrical conductivity.

Table 2 demonstrates integrated parametersconcerning the time of electrolysis determin-ing the �saturation� of the electrode with metal.These parameters characterize the process ofcopper deposition onto electrodes made of theFCM under investigation: the process rate (U),the current yield of copper (CY), the relativemass of copper deposited onto one layer of theelectrode (δ), the root-mean-square deviationHRMS. One can see that the most non-uniformdistribution of copper deposit is observed forthe electrode made of VINN-250 with high elec-trical conductivity wherein the maximal valueof (HRMS) is registered; as much as 27.5 g cop-per was deposited onto 1 g of FCM (which cor-responds to one layer). Copper is distributedmost uniformly over the electrode made of FCMwith low electrical conductivity (KNÌ-450Ì),HRMS = 38.5. As much as 13.75 g of copper wasdeposited onto 1 g of FCM (one layer). As faras an electrode made of highly conductive ma-terial (Carbonetkalon ÒK 24) with a lower po-rosity and the highest density, a minimumamount of metal deposited onto the mass unitof material was obtained, and there was a min-imal time required for overstocking the elec-trode with metal.

Effect of solution feeding direction

The direction of feeding the solution intothe electrode influences to a considerable ex-tent upon the parameters of the process ofelectrochemical copper deposition. With chang-ing the direction of feeding the solution intothe electrode from back to frontal one, copperis deposited onto the side of solution feeding

during all the time of electrolysis. With increas-ing the initial electrical conductivity of the elec-trode material from 1.3 ⋅ 10�2 Sm/cm (ANM) upto 4.6 ⋅ 10�1 Sm/cm (VNG-50) the time of elec-trode �saturation� with metal decreases amount-ing to 180 min for ANM and only 90 min forVNG-50. The ratio between the mass of a cop-per deposit and thee mass of the layer variesranging within 6�9 g/g of FCM. The current30�40 %. Thus, the electrochemical copper dep-osition onto FCE with the frontal solution feed-ing into the electrode under the electrolysis pro-cess conditions under investigation is charac-terized by a rather low efficiency, which doesnot allow us to recommend this mode for in-dustrial application.

Influence of solution flow-through rate

One of the important technological param-eters allowing one to influence the process ofthe electrochemical extraction of metals fromthe recovery bath of galvanic manufactureautomatic lines is presented by solution flow ratethrough the bulk of the electrode (or the rateof solution circulation between electrolyser andwashing bath). According to theoretical conceptsconcerning the operation of flow-through bulk-porous electrodes, the electrochemical processis located at the side of feeding the solutioninto the electrode (KmS >> mv) or it is is uni-formly distributed over the electrode thickness(KmS << mv) depending on the ratio betweenKmS and mv (Km is mass transfer factor, S isreaction surface FCE, mv is solution flow-throughvolume rate) [13].

In this case the author of [13] assumes thatthe discharge of an electroactive componentoccurs with the limiting diffusion current allover the volume of the electrode, whereas theelectrical conductivity of the electrode materi-al is much greater than the electrical conduc-tivity of the solution. He did not specified, howmany times KmS is higher or lower than mv.Moreover, the situations when either KmS >mv or KmS < mv, or their values are compara-ble were not considered, let alone the situationwhen the discharge of electroactive componentoccurs out of the limiting diffusion currentmode or at higher current density values. In

348 V. K. VARENTSOV et al.

TABLE 3

KmS value depending on linear solution flow-throughrate, determined via a calculation method

Material of electrode Flow-through rate, mL/(s ⋅ cm2)

0.01 0.1 0.4 1.0 3.0

VNG-50 1.1 2.4 3.9 5.3 9.4

VINN-250 1.0 2.3 3.7 5.1 9.1

ANM 1.2 2.6 4.3 5.9 10.4

KNÌ-450Ì 0.9 2.1 3.5 4.8 7.1

addition, the influence of the ratio betweenthese parameters upon the distribution of elec-troactive component discharge over the elec-trode thickness under gradual �overgrowing�the FCE with metal, i. e. in dynamics when theratio of these components is changing, ap-peared to be with no consideration.

In connection with the foregoing, it is ofpractical and theoretical interest to investigateexperimentally the influence of the solutionflow-through rate upon the efficiency of met-al electrochemical deposition onto FCE in dy-namics. The range of solution flow rate valueschosen amounts to 0.1�1.0 mL/(s ⋅ cm2). Thestudies were carried out at fixed values of thedimensional current density such as 500, 1500and 2500 À/m2 for electrodes made of ANM,VINN-250 and VNG-50.

Let us in more detail consider the resultsobtained for the electrodes made of ANM andVNG-50 at the dimensional current densityequal to 1500 À/m2.

Table 3 demonstrates the results of calcu-lations for KmS depending on mv, performedaccording to [13], for the rates of solution flow-ing-through realized in the industry. Withinentire range under investigation, KmS > mv forall the materials listed in Table 1. As far as dif-ferent materials are concerned, the values ofKmS vary within a narrow range at the samesolution flow-through rate.

As it was indicated above, the dimensionalcurrent density of 1500 À/m2 and the flowing-through rate equal to 0.4 mL/(s ⋅ cm2) result inthe fact that at a considerable part of the elec-trode the ions of copper are reduced in themode of the limiting diffusion current. It is ob-vious that at the flow-through rate amountingto 0.1 mL/(s ⋅ cm2) the discharge of copper ionsshould be accompanied by a considerable hy-drogen evolution, whereas at the rate equal to1.0 mL/(s ⋅ cm2) the reduction of copper ions inthe limiting diffusion current mode is possiblefor a small part of the electrode.

Figures 6, 7 present the results for the stud-ies on the dynamics of copper deposit distri-bution over the thickness of electrodes madeof materials with low (see Fig. 6) and high (seeFig. 7) initial electrical conductivity at differentvalues of the solution flow rate and at the di-mensional current density equal to 1500 À/m2. It

Fig. 6. Copper mass to FCE mass ratio (mCu/mFCM) depending on the electrode thickness at the solution flow-throughrate 0.1 (a), 0.4 (b), 1.0 mL/(s ⋅ cm2 (c). The duration of electrolysis, min: 60 (1), 120 (2), 180 (3), 360 (4), 420 (5), 540 (6);B is electrode backside; FCM is presented by VNG-50.

CURRENT DENSITY AND SOLUTION FLOW-THROUGH RATE INFLUENCE UPON THE DYNAMICS OF COPPER DEPOSITION ONTO ELECTRODES 349

Fig. 8. Copper extraction rate U (à), copper current yield CY (b) and copper mass to FCE mass ratio mCu/mFCM (c)depending on the solution flow-through rate: 1�3 � VNG-50; 1´�3´ � ANM; i, À/m2: 500 (1, 1´), 1500 (2, 2´), 2500 (3, 3´).

is seen that an increase in the flow-through ratefrom 0.1 to 1.0 mL/(s ⋅ cm2) results in changingthe localization of the main part of copper de-posit. A similar character of changing the distri-bution of copper deposit over the electrode thick-ness depending on the solution flow-through ratehas been obtained at the dimensional current den-sity values amounting to 500 and 2500 À/m2.

The rate of copper deposition and its cur-rent yield exhibit an increase with the increasein the solution flow-through rate in the caseof VNG-50 for all the dimensional current den-sity values under investigation, whereas in thecase ANM this phenomenon is observed at 1500and 2500 À/m2 (Fig. 8). These data were obtained

Fig. 7. Copper mass to FCE mass ratio (mCu/mFCM) depending on the electrode thickness at the solution flow-throughrate 0.1 (a), 0.4 (b), 1.0 mL/(s ⋅ cm2 (c). The duration of electrolysis, min: 60 (1), 120 (2), 180 (3), 360 (4), 420 (5), 540(6); B is electrode backside; FCM is presented by ANM.

under the conditions those are close or corre-sponding to so called �saturation� of an elec-trode with metal. At a slow flow-through rateof the solution (0.1 mL/(s ⋅ cm2)) the values ofcopper deposition rate (see Fig. 8, à) and the ra-tio between the mass of copper the mass ofthe electrode (see Fig. 8, c) are close to a consid-erable extent. With an increase in flow-throughrate of the solution one can reveal a discrep-ancy between them. A maximal value of cop-per mass deposited onto the electrode in totalat the flow-through rate amounting to 0.4 mL/(s ⋅ cm2) is observed at 1500 both 2500 À/m2,as well as its decrease is registered for the di-mensional current density equal to 500 À/m2

350 V. K. VARENTSOV et al.

(see Fig. 8, c). With increasing the solution flow-through rate, the ratio mCu/mFCM decreases,and this fact most pronounced for the electrodemade of the material with a low electrical con-ductivity (ANM).

The aforementioned results of the experi-mental studies demonstrate that theoretical pre-mises concerning the distribution of the elec-trochemical process over the electrode thick-ness depending on the ratio between KmS andmv under the conditions of real electrochemi-cal deposition of metal onto FCE have not ob-tained any practical support. So, the electro-chemical deposition of metal onto FCE underreal conditions considered in our work, does notoccur all over the bulk of the electrode in thecase of the limiting diffusion current; the initialelectrical conductivity of FCM does not exceedto a considerable extent the electrical conduc-tivity of the solution (especially during the ini-tial phase of electrolysis); in the course of theelectrochemical deposition of metal, changingis observed concerning the ratio between KmSand mv, as well as the ratio between the electri-cal conductivity values corresponding to the elec-trode material and the solution. The electrochem-ical metal deposition is usually accompanied byparallel reactions of hydrogen ion and oxygenreduction. To all appearance, just the combina-tion of these causes is determining for the con-siderable discrepancy between the results ofexperimental research and theoretical forecasts.

CONCLUSION

The dynamics electrolytic copper extractionfrom sulphuric acid solution was studied for thefollowing composition, g/L: Cu 0.16, H2SO4 25,(NH4)2SO4 80 deposited onto fibrous carbon elec-trodes (FCE) with uniform distribution of ini-tial electrical conductivity over the electrodethickness depending on the initial electrical con-ductivity of the electrode (0.46�1.8 ⋅ 10�6 Sm/cm),the dimensional current density (500�2500 À/m2),the flow rate solution feeding (0.1�1.0 mL/(s ⋅ cm2))into the electrode as applied to the technology of

copper extraction from a recovery bath of gal-vanic manufacture automated line.

It has been established that in the courseof electrochemical deposition, the profile ofcopper deposit over the electrode thickness in-herent in each set of electrolysis conditions andin the kind of FCE exhibits changing. Thereofthe parameters describing the process of elec-trochemical copper deposition (the current yieldof copper, the rate of copper deposition, theuniformity of distribution over the electrodethickness, the specific mass of copper depositedonto FCE) exhibit changing, too. The prevailingeffect on the dynamics of deposit distribution overthe electrode thickness and the parameters ofelectrochemical deposition process under the in-vestigated electrolysis conditions is exerted by thesolution flow-through rate and the dimensionalcurrent density. It has been established that theinitial electrical conductivity of FCM influencesto a lesser extent and its influence is most pro-nounced at low electrolysis duration time and lowdimensional current density.

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