JP2011053017A - Method of managing concentration of additive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of managing concentration of an additive which can quantitatively evaluate the amount of the additive within an electrolyte in electrolytic refining of copper and easily managing the amount of the additive at an operation field. <P>SOLUTION: The concentration of glue is evaluated by the shape of a polarization curve within a range (A part) of 30-140 mV (vs. SSE), while the concentration of thiourea is evaluated by the shape of a polarization curve within a range (B part) of 180-290 mV (vs. SSE). Concretely speaking, potential is used as an evaluation value indicating transition in the direction of an arrow at a curved part in the A part and current is used as an evaluation value indicating transition in the direction of an arrow at a curved part in the B part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for controlling the concentration of an additive contained in an electrolytic solution for copper electrolytic purification.

  Conventionally, as a method of managing the electrolytic solution composition of electrolytic purification, a method of chemically analyzing the concentration of metal components such as copper and nickel as main components and the concentration of acids such as sulfuric acid and hydrochloric acid has been carried out.

  In addition, chemical analysis can be performed on the concentration of additives such as thiourea and glue, but in general, chemical analysis takes time. In addition, decomposition products of the additive may affect the electrodeposition state, and measurement of the additive concentration by chemical analysis may not always be effective.

  Therefore, conventionally, the hull cell test or the polarization measurement is used for evaluating the concentration of the additive contained in the electrolytic solution. In the Hull cell test, current is applied with the cathode and anode facing diagonally, the current distribution on the cathode is biased, and the electrodeposition state is observed, and thiourea concentration and glue concentration can be evaluated ( For example, see Patent Document 1.) As for the polarization measurement, the electrolyte solution can be evaluated by comparing the shape of the polarization curve with other polarization curves.

  However, in the Hull cell test, it takes time and labor to dry the cathode after energization, and the additive concentration cannot be easily evaluated at the operation site. In addition, polarization measurement is limited to qualitative evaluation of the amount of additive, and it is difficult to obtain a quantitative evaluation as to which additive should be replenished to the electrolyte solution.

JP-A-6-264278

  The present invention has been proposed in view of the above circumstances, and an additive capable of quantitatively evaluating the amount of additive in an electrolytic solution in electrolytic purification of copper and easily managing the amount of additive at an operation site Provides a concentration management method.

  As a result of intensive studies, the present inventors have shown that the amount of additive contained in the electrolyte can be quantitatively evaluated by quantifying the shape of the predetermined potential range of the polarization curve by linear approximation. I found it.

  That is, the additive concentration control method according to the present invention is a method of immersing the working electrode, the counter electrode, and the reference electrode in the electrolyte solution in the additive concentration control method contained in the electrolytic solution of copper electrolytic purification, A polarization measurement step of sweeping and applying a voltage between the electrode and the counter electrode to measure a polarization curve; a first curve portion that curves downward with an increase in the amount of glue in the polarization curve; and downward with an increase in thiourea The second bending portion that is bent in a straight line and the third bending portion that is bent upward between the first bending portion and the second bending portion are linearly approximated by two straight lines, respectively. Analyzing the crossing points of the first crossing point, the second crossing point, and the third crossing point from the one having the highest potential, and determining the amount of glue based on the potential of the first crossing point Difference between the current value at the second intersection and the current value at the third intersection And having a thiourea amount determination step of determining the appropriateness of thiourea amount based on.

  According to the present invention, since the amount of thiourea and the amount of glue can be quantitatively evaluated based on the shape of the predetermined potential range of the polarization curve, the amount of thiourea and the amount of glue can be easily managed at the operation site. Can do.

It is a block diagram which shows the structural example of the electrolytic purification apparatus of copper. It is a block diagram which shows the structural example of a density | concentration management apparatus. It is a figure for demonstrating the change of the polarization curve accompanying the density | concentration change of an additive. It is a figure for demonstrating the determination method of the evaluation value showing the shape of a polarization curve. It is a schematic diagram which shows a working electrode and a counter electrode. It is a schematic diagram which shows the cell for a measurement. It is a schematic diagram which shows the electrodeposition surface of a hull cell test piece. It is a graph which shows the relationship between the evaluation result of a hull cell test, and the evaluation result of this method about a glue concentration. It is a graph which shows the relationship between the evaluation result of a hull cell test, and the evaluation result of this method about thiourea density | concentration. It is a graph which shows the relationship between the defective rate of electrolytic copper, and the evaluation result of the amount of glue of the electrolyte solution used for manufacture of the electrolytic copper. It is a graph which shows the relationship between the defective rate of electrolytic copper, and the evaluation result of the amount of thiourea of the electrolyte solution used for manufacture of the electrolytic copper.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail in the following order with reference to the drawings.
1. Copper electrolytic purification equipment (Figure 1)
2. Concentration management device (Fig. 2)
3. Method for evaluating additive amount based on polarization curve (Figs. 3 and 4)
4). Example 1 (FIGS. 5 to 9)
5. Example 2 (FIGS. 10 and 11)
6). Summary

1. Copper Electrolytic Purification Device FIG. 1 is a block diagram showing a configuration example of a copper electrolytic purification device 10. The electrolytic purification apparatus 10 includes an electrolytic bath 11 for containing an electrolytic solution, a concentration management device 20 that manages the concentration of an additive contained in the electrolytic solution drained from the electrolytic bath 11, and an addition instruction from the concentration management device 20. And an additive supply unit 30 for supplying the additive according to the above. The electrolytic purification apparatus 10 includes a first storage tank 14 that stores the drainage of the electrolytic tank 11, a second storage tank 15 that is supplied with hydrochloric acid, sulfuric acid, and steam, and a pump 16 that circulates the electrolyte. And a supply tank 17 for supplying an electrolytic solution to the electrolytic tank 11.

  A part of the drainage from the electrolytic cell 11 is periodically sampled by the concentration management device 20, and the remaining drainage is discharged to the first storage tank 14. The drainage liquid in the first storage tank 14 is discharged to the second storage tank 15, mixed with hydrochloric acid or sulfuric acid, and the liquid temperature is set to a predetermined temperature by steam. The electrolytic solution in the second storage tank 15 is supplied to the supply tank 17 by the pump 16 and is supplied to the electrolytic tank 11 through the supply tank 17.

  The cathode 12 and the anode 13 are alternately immersed in the electrolytic solution of the electrolytic cell 11. For the cathode 12, for example, copper is electrodeposited on a base plate such as stainless steel so as to have a thickness of about 0.5 to 1 mm and peeled off. For the anode 13, purified crude copper is used. Is used. The electrolytic solution contains copper, hydrochloric acid, sulfuric acid and the like, and further contains glue and thiourea as additives for improving the throwing power and making the crystals finer.

  The concentration management device 20 measures the polarization of the electrolyte drained from the electrolytic cell 11 as described later, and determines whether the amount of glue and the amount of thiourea are appropriate based on the shape of the polarization curve in a predetermined potential range. Further, the concentration management device 20 determines whether or not glue and thiourea can be added according to the determination result, and instructs the additive supply unit 30 to add.

  The additive supply unit 30 includes a glue storage tank and a thiourea storage tank, and adds a predetermined amount of glue or thiourea to the electrolytic solution in the electrolytic tank 11 in accordance with an addition instruction from the concentration management device 20.

  In this way, the electrolytic solution is circulated, and the concentration management device 20 evaluates the amount of the additive based on the shape of the polarization curve of the drainage of the electrolytic cell 11 and replenishes the shortage of the additive. The amount of the additive in the electrolyte is kept within a certain range.

2. Additive Concentration Management Method Next, an additive concentration management method in the above-described concentration management apparatus 20 will be described.

  FIG. 2 is a block diagram illustrating a configuration example of the density management device 20. The concentration management device 20 includes a bathtub 21, a working electrode 23 immersed in the electrolytic solution 22 injected into the bathtub 21, a counter electrode 24, and a reference electrode 25.

  The bath 21 is made of a material having corrosion resistance to acids and alkalis. For example, chemical resistant glass such as a beaker, engineering plastic such as polycarbonate, metal such as stainless steel and titanium, and the like are used. Metals such as copper, stainless steel, and platinum are used for the working electrode 23 and the counter electrode 24, and copper is optimal when measuring a copper electrolyte in actual operation. The reference electrode 25 may be a general-purpose one such as a silver-silver chloride electrode (SSE: Silver / Silver Chloride Electrode) or a saturated calomel electrode (SCE).

  In addition, the concentration management device 20 includes a power source 41 for sweeping and applying a voltage between the working electrode 23 and the counter electrode 24, the potential of the working electrode 23 with respect to the reference electrode 25, and between the working electrode 23 and the counter electrode 24. Polarization is based on the measurement unit 42 that measures the current generated in the power source, the control unit 43 that controls the power supply unit 41 and the measurement unit 42, the potential of the working electrode 23 with respect to the reference electrode 25, and the current generated between the working electrode 23 and the counter electrode 24 A calculation unit 44 that draws a curve and a storage unit 45 that stores calculation results and the like are provided.

  The power supply unit 41 sweeps and applies a voltage between the working electrode 23 and the counter electrode 24, and is controlled by the control unit 43. The measuring unit 42 measures the potential difference of the working electrode 23 with respect to the reference electrode 25 and the current generated between the working electrode 23 and the counter electrode 24. The measurement result is sent to the calculation unit 44, and the polarization curve is analyzed as will be described later. The polarization curve is drawn on chart paper or converted into data and stored in the storage unit 45.

  The control unit 43 sweeps and applies a voltage, and stores the obtained polarization curve in the storage unit 45, and evaluates the additive amount based on the polarization curve stored in the storage unit 45. And the program for notifying the additive supply unit 30 of the evaluation result of the additive amount.

3. Method for Evaluating Additive Amount Based on Polarization Curve Next, a method for evaluating the amount of additive based on the polarization curve measured by the concentration management apparatus 20 described above will be described.

  FIG. 3 is a graph showing how the polarization curve changes as the additive concentration changes. The polarization curve is obtained as a change in the shape of the potential / current curve. The dotted polarization curve in the figure has a low concentration of glue and thiourea, and the solid curve in the figure has a high concentration of glue and thiourea.

  As shown in FIG. 3, when the concentration of glue increases, the polarization curve curves downward in the A part in the range of 30 to 140 mV (vs. SSE) and shifts in the direction of the arrow. That is, the glue concentration affects the decomposition voltage, and as the amount of glue increases, the cathode potential becomes lower and polarizes to increase the decomposition voltage.

  Further, when thiourea increases, the polarization curve is curved downward in the portion B in the range of 180 to 290 mV (vs. SSE) and shifts in the direction of the arrow. That is, the thiourea concentration affects the shape in which the current density stagnates, and as the amount of thiourea increases, the potential range in which the current density stagnates increases, and the value of the current density decreases.

  Therefore, in this method, the glue concentration is evaluated by the shape of the polarization curve of the A part, and the thiourea concentration is evaluated by the shape of the polarization curve of the B part. Specifically, an electric potential is used as an evaluation value representing the transition in the arrow direction of the bending portion in the A portion, and an electric current is used as an evaluation value representing the transition in the arrow direction of the bending portion in the B portion.

  FIG. 4 is a diagram for explaining an example of a method of determining evaluation values in the A part and the B part. In this example, the downward bending portion in the portion A in the range of 30 to 140 mV (vs. SSE), the downward bending portion in the portion B in the range of 180 to 290 mV (vs. SSE), and 110 to 210 mV (vs. SSE). An evaluation value is obtained using an upward curved portion in the range of.

  In the part A, the downward curved part is linearly approximated by two tangents, and the potential as the evaluation value a is obtained from the x coordinate of the intersection A1 of the two tangents.

  In the part B, the upper curved part in the range of 110 to 210 mV (vs. SSE) is linearly approximated by two tangents to obtain the intersection B1 of the two tangents, and the range of 180 to 290 mV (vs. SSE) is obtained. The downward curved portion is linearly approximated by two tangents, and an intersection B2 of the two tangents is obtained. And the difference of the y coordinate of intersection B1 and intersection B2 is calculated | required, and it is set as the evaluation value b. Here, the difference between the intersection point B1 and the intersection point B2 is that even if the current density in the range of 110 to 210 mV (vs. SSE) decreases with the increase in the concentration of glue and thiourea, the current density is stagnant. This is to correctly represent the shape.

  Thus, by calculating | requiring the evaluation value a and the evaluation value b, the transition of the curved part in the arrow direction in the A part and B part accompanying the increase in the concentration of glue and thiourea can be expressed.

  The linear approximation of the curved portion of the polarization curve is not limited to the tangent line, and an approximate straight line may be used. For example, the range of 30 to 60 mV (vs. SSE) and the range of 110 to 140 mV (vs. SSE) of the polarization curve shown in FIG. 4 are linearly approximated by the least square method, and the evaluation value is calculated from the intersection of the two lines. The potential may be obtained. Similarly, the range of 110 to 140 mV (vs. SSE) and the range of 180 to 210 mV (vs. SSE) of the polarization curve shown in FIG. 4 is linearly approximated by the least square method, and the intersection of these two lines is obtained. The range of 180 to 210 mV (vs. SSE) and the range of 260 to 290 mV (vs. SSE) of the polarization curve shown in FIG. 4 is linearly approximated by the least square method, and the intersection of these two straight lines is obtained. You may obtain | require an evaluation value by the difference of the y coordinate of an intersection.

  That is, in the concentration management apparatus 20 shown in FIG. 2, the calculation unit 44 increases the amount of thiourea, the downward curved portion in the range (A portion) of 30 to 140 mV (vs. SSE) curved downward as the glue amount increases. 110 to 290 mV (vs. SSE) curved in the downward direction (B part), and between the downward curved part of part A and the downward curved part of part B, and curved upward 110 The upper curved portion in the range of ~ 210 mV (vs. SSE) is linearly approximated by two straight lines, and the intersection of the two straight lines is defined as an intersection A1, an intersection B1, and an intersection B2 from the noble potential. Then, the calculation unit 44 compares the potential at the intersection A1 with the potential at the intersection A1 obtained in advance using an electrolyte containing an appropriate amount of glue, and determines whether the amount of glue is appropriate. Further, the calculation unit 44 calculates the difference between the current density at the intersection B1 and the current density at the intersection B2, and the current value at the intersection B1 and the current value at the intersection B2 which are obtained in advance using an electrolyte containing an appropriate amount of thiourea. Are compared with each other to determine whether the amount of thiourea is appropriate. The additive supply unit 30 is notified of the discrimination result of the glue amount and the discrimination result of the thiourea amount.

  As described above, by evaluating the amount of the additive in the electrolytic solution based on the polarization measurement result, the concentration of the additive in the copper electrolytic purification process can be easily managed at the operation site.

4). Example 1: Comparison of evaluation results obtained by this method and evaluation results obtained by the Hull cell test In order to confirm the usefulness of this method, the quantitative evaluation by polarization measurement and the quantitative evaluation by the hull cell test were compared for the amount of additive. The electrolyte used was an actual operation having a copper concentration of 45 g / l, a sulfuric acid concentration of 185 g / l, and a liquid temperature of 60 ° C.

4-1. Polarization Measurement For the polarization measurement, a working electrode 231 shown in FIG. 5A and a counter electrode 241 shown in FIG. 5B were used. A rolled copper plate 233 was used as the working electrode 231 and masked with a tape 232 so that the electrode area (Wd × Wd) was 20 mm × 20 mm. Similarly, a rolled copper plate 243 was used for the working electrode 241 and masked with a tape 242 so that the electrode area (Wd × Wd) was 20 mm × 20 mm. Then, the electrode surface of the working electrode 231 and the electrode surface of the counter electrode 241 were opposed in parallel by the measurement cell shown in FIG.

  As shown in FIG. 6A, the rolled copper plate 243 on the counter electrode 241 side and the thin sheet-like sheets 52A arranged at both ends and the lower end of the rolled copper plate 243 are sandwiched between transparent acrylic plates 51A and 51B, and the acrylic plate The portions on the sheet 52A at both ends of 51A and 51B are fixed by long screw bolts and nuts 54, 55 and 56, and similarly, the rolled copper plate 233 on the working electrode 231 side, and the thin plate-like shape disposed at both ends and the lower end of the rolled copper plate 233 The sheets 52B and 53 were sandwiched between transparent acrylic plates 51C and 51D, and the portions on the sheet 52B at both ends of the acrylic plates 51C and 51D were fixed with long screw bolts and nuts 54, 55, and 56 to produce a measurement cell. . Then, as shown in FIG. 6B, the long screw bolts and nuts 54A, 54B, 55A, 55B, 56A, and 56B are adjusted at the six positions on both ends of the acrylic plates 51A, 51B, 51C, and 51D, and the working electrode and the counter electrode The distance D was set to 40 mm. Further, the Lugin tube 251 was arranged so that the tip of the Lugin tube 251 was close to the working electrode 231. An Ag—AgCl electrode was used as a reference electrode connected to the Lugin tube 251.

  The measurement cell shown in FIG. 6 was immersed in an electrolytic solution of an actual operation in a 500 ml beaker, and was polarized using a potentiostat from a potential of 0 mV to a base direction at a sweep rate of 10 mV / sec to create a polarization curve. And the evaluation value a and the evaluation value b were calculated | required by the linear approximation by the tangent mentioned above.

4-2. Hull cell test The hull cell test was carried out by the method described in JP-A-6-264278. The electrolyte of actual operation was put into a Hull cell electrolytic cell having a capacity of 267 ml, and the current was supplied for 1 hour at a current of 2A. A stainless steel plate was used as the hull cell test piece. After completion of electrolysis, the electrodeposited surface of the Hull cell test piece was observed to evaluate the concentrations of glue and thiourea.

FIG. 7 is an electrodeposition surface of the hull cell test piece shown in FIG. 1 of JP-A-6-264278. Concentration Evaluation of glue and thiourea is correlated in electrostatic Chakumen the Hull cell test piece shown in FIG. 7, the length L _F of Novi (F unit) which is correlated to the concentration of glue, and the concentration of thiourea beard The length of (C part) was measured.

4-3. Comparison Results FIG. 8 is a graph showing the relationship between the evaluation results of the Hull Cell test and the evaluation results of the present method for the glue concentration contained in the electrolytic solution in actual operation. The correlation coefficient (R ² ) between the length L _F of Nobi (F section) by the Hull cell test and the reading value (evaluation value) a by this method is 0.8538, which shows that a high correlation is exhibited.

Moreover, FIG. 9 is a graph which shows the relationship between the evaluation result of a hull cell test, and the evaluation result of this method about the thiourea density | concentration contained in the electrolyte solution of a real operation. The correlation coefficient (R ² ) between the length of beard (C section) by the Hull cell test and the reading value (evaluation value) b by this method is 0.8456, which indicates that a high correlation is exhibited.

  In other words, the evaluation results obtained by this method are highly correlated with the Hull Cell test results for both the glue concentration and the thiourea concentration, and the reliability equivalent to the conventional quantitative evaluation method for the Hull Cell test results can be obtained. I understand.

5. Example 2: Relationship between the evaluation result of this method and the defective rate of electrolytic copper In order to confirm the application of this method to actual operation, the relationship between the quantitative evaluation by polarization measurement and the defective rate of electrolytic copper was investigated. The electrolytic copper was taken from an electrolytic cell in actual operation during the period from April 2004 to May 2006, and evaluated by a polarization curve obtained by polarization measurement of the electrolytic solution used for the production of the electrolytic copper. did.

  The polarization measurement was performed in the same manner as described in 4-1. Moreover, the judgment of good / bad electric copper was judged as bad if 30% or more of the entire surface was observed with particles of 10 mm or more on the surface of the electric copper, and good.

  FIG. 10 is a graph showing the relationship between the defective rate of electrolytic copper and the evaluation result of the amount of glue of the electrolytic solution used in the production of electrolytic copper. From this graph, it can be seen that the optimum range of the reading value (evaluation value) a of Nika that reduces the defect of electrolytic copper is 80 to 100 mV.

Moreover, FIG. 11 is a graph which shows the relationship between the defective rate of electrolytic copper, and the evaluation result of the thiourea amount of the electrolyte solution used for manufacture of the electrolytic copper. From this graph, it is understood that the optimum range of the reading value (evaluation value) b of thiourea in which defects of electrolytic copper are reduced is 1000 to 1500 A / m ² .

  That is, by managing the evaluation value “a” for evaluating the amount of glue and the evaluation value “b” for evaluating the amount of thiourea within the above-described optimal numerical range, the electrolytic copper defect rate can be reduced in actual operation.

6). Summary As described above, the evaluation result by this method is used as an index for judging the excessive amount of additive in actual operation by comparing with the evaluation result of the electrolyte containing the appropriate amount of additive. be able to. Moreover, the quality of electrolytic copper can be stably maintained in a good state by maintaining the additive amount in an optimal state using the evaluation result of this method.

  DESCRIPTION OF SYMBOLS 10 Electrolytic refining device, 11 Electrolysis tank, 12 Cathode, 13 Anode, 14 First storage tank, 15 Second storage tank, 16 Pump, 17 Supply tank, 20 Concentration control device, 21 Bath, 22 Electrolyte, 23 Action Electrode, 24 Counter electrode, 25 Reference electrode, 30 Additive supply unit, 41 Power supply unit, 42 Measuring unit, 43 Control unit, 44 Calculation unit, 45 Storage unit

Claims (4)

In the concentration control method of the additive contained in the electrolytic solution of copper electrolytic purification,
A polarization measuring step of immersing the working electrode, the counter electrode, and the reference electrode in the electrolyte, sweeping and applying a voltage between the working electrode and the counter electrode, and measuring a polarization curve;
In the polarization curve, a first curved portion that curves downward with an increase in glue amount, a second curved portion that curves downward with an increase in thiourea, and the first curved portion and the second curved portion. The third curved part that is located between the two parts and that is curved upward is linearly approximated by two straight lines, and the intersection of the two straight lines is defined as the first intersection and the second intersection from the noble potential. And an analysis step as a third intersection point;
A glue amount determining step for determining the suitability of the glue amount based on the potential of the first intersection;
A thiourea amount determination step of determining whether or not the thiourea amount is appropriate based on a difference between the current value at the second intersection and the current value at the third intersection. In the glue amount determination step, the potential of the first intersection point is compared with the potential of the first intersection point obtained in advance using an electrolyte containing an appropriate amount of glue, and the suitability of the glue amount is determined. ,
In the thiourea amount determination step, a difference between a current value at the second intersection and a current value at the third intersection, and a second intersection obtained in advance using an electrolyte containing an appropriate amount of thiourea. The additive concentration control method according to claim 1, wherein the current value and the difference between the current values at the third intersection are compared to determine whether or not the amount of thiourea is appropriate.   3. The additive according to claim 2, wherein in the analysis step, the first bending portion, the second bending portion, and the third bending portion are linearly approximated by two tangent lines, respectively. Concentration management method.   The first bending portion, the second bending portion, and the third bending portion are each in a potential range of 30 to 140 mV of a polarization curve when a silver-silver chloride electrode is used as the reference electrode, 180 to 4. The method for controlling the concentration of an additive according to claim 3, wherein the potential range is 290 mV and the potential range is 110 to 210 mV.

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