JP5431998B2 - Method and apparatus for recovering copper from acidic waste liquid containing copper - Google Patents

Description

  The present invention treats a copper-containing acidic waste liquid containing copper ions, such as an etching waste liquid generated when etching a copper printed board with a cupric chloride etchant and a plating bath liquid renewal waste liquid in the production of electrolytic copper foil. The present invention relates to a method and apparatus for recovering copper.

  As an acidic waste liquid containing copper ions at a high concentration (hereinafter referred to as “copper-containing acidic waste liquid”), an etching waste liquid produced when etching a copper printed circuit board with a cupric chloride etchant, or in electrolytic copper foil production A renewal waste solution of a plating bath is known. These waste liquids have a high copper concentration of about 5 to 20% by mass (hereinafter simply referred to as “%”), while the concentration of coexisting chloride ions and sulfate ions is usually as high as 5 to 30%.

  As a copper recovery process for such a copper-containing acidic waste liquid, a method of using a difference in ionization tendency, for example, reacting with iron scrap to deposit and recovering metallic copper is performed in part. However, this method has a low copper recovery rate from the waste liquid. Further, since a waste liquid containing iron ions eluted by the reaction with copper ions and residual copper ions remains, it is difficult to say that this waste liquid needs to be treated separately and is an efficient treatment method.

  Further, as a general method, there is known a treatment method in which heavy metals are precipitated and removed as a hydroxide by adding an alkaline substance such as sodium hydroxide. Since the water content is high and the amount is large, it is not suitable for the treatment of copper-containing acidic waste liquid having a high copper ion concentration.

  By the way, the present inventors disclosed in Patent Document 1 a method capable of producing and recovering copper oxide by mixing a copper-containing acidic waste liquid and an oxidant and then adding the mixture to an alkaline solution. According to this method, the copper oxide which does not contain a double salt can be manufactured by dripping the liquid mixture of a copper containing acidic waste liquid and an oxidizing agent to an alkaline solution. This is because the copper-containing acidic waste liquid can be neutralized and oxidized while obtaining an appropriate dilution effect.

  The copper oxide obtained by the method of Patent Document 1 can be reused as it is if the required purity of the copper oxide is relatively low. For example, a copper plating bath solution of a printed circuit board can be reused. There was a problem when reusing it as a raw material.

  That is, the chlorine content of the copper oxide used as a raw material for the copper plating bath solution of the printed circuit board is preferably low because the chloride ion concentration of the copper plating bath solution affects the plating state. When copper oxide is used, the chlorine content is a little as high as about 400 mg-Cl / kg-CuO. In order to recycle it as a raw material for copper plating baths, the reaction process is devised to further improve the purity. In addition, a separate process for improving the purity is required.

  Therefore, in order to establish recycling that treats the copper-containing acidic waste liquid and reuses the recovered copper oxide as a raw material for the copper plating bath liquid, the equipment for treating the copper-containing acidic waste liquid and the equipment for improving the purity of the produced copper oxide Is necessary, and the entire facility is complicated.

Japanese Patent No. 4199821

  The present invention treats copper-containing acidic waste liquids, such as copper chloride-containing etching waste liquids and electrolytic copper foil plating bath renewal waste liquids, which have been disposed of as industrial waste, without complicated equipment, and from copper-containing acidic waste liquids. It is an object of the present invention to provide a method and an apparatus for recovering copper oxide having a low chlorine content.

  The present inventors mixed an acidic waste liquid containing a high concentration of copper ions, which is a liquid to be treated, and an oxidizing agent, and then poured and mixed the mixture into an alkaline solution while managing it to be in a predetermined pH range. Then, after exceeding the predetermined time point, while intermittently adding the liquid mixture into the mixing reaction tank, extending the downtime of the addition, the chlorine content of the copper oxide to be generated is increased. The present invention has been completed by finding out that it can be reduced.

That is, the present invention includes the following contents.
(1) In a mixed reaction tank to which a predetermined amount of alkaline solution is supplied, while controlling so that the pH of the liquid in the mixed reaction tank does not temporarily drop to 9 or less, the copper-containing acidic waste liquid and the oxidizing agent The mixed liquid is poured and mixed in the mixing reaction tank to produce an alkaline suspension containing a solid material mainly composed of copper oxide, and the solid material is separated from the alkaline suspension. A method for recovering copper,
When the added amount of the mixed liquid exceeds at least 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary for neutralizing the alkaline solution in the mixed reaction tank, the mixed liquid is poured into the mixed reaction tank. A method for recovering copper from a copper-containing acidic waste liquid, characterized in that the pause time for pouring is 10 minutes or longer while intermittently performing.

  (2) Addition of the liquid mixture is performed intermittently, and the amount of the liquid mixture added is 0.5 equivalent of the amount of copper-containing acidic waste liquid required to neutralize the alkaline solution in the mixing reaction tank. In the case of exceeding the addition pause time, the addition amount of the liquid mixture is equal to the addition pause time of up to 0.5 equivalent of the copper-containing acidic waste liquid amount necessary for neutralizing the alkaline solution in the mixing reaction tank. The method for recovering copper from the copper-containing acidic waste liquid according to the above (1), characterized in that it is 3 times or more.

  (3) Addition of the liquid mixture is intermittently performed, and the pH of the mixed reaction tank is adjusted to 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary for neutralizing the alkaline solution in the mixed reaction tank. After lower than the pH in the state where the corresponding copper-containing acidic waste liquid is added, the suspension time for pouring the mixture is more than 3 times the suspension time for pouring the mixture until the pH is lowered The method for recovering copper from the copper-containing acidic waste liquid as described in (1) above.

(4) In any one of the above (1) to (3), the pH of the suspension in the mixing reaction tank is controlled by adding a mixed liquid of copper-containing acidic waste liquid and an oxidizing agent and / or an alkaline agent. A method for recovering copper from the described copper-containing acidic waste liquid.

(5) The copper according to any one of (1) to (4) above, wherein a mixed liquid of copper-containing acidic waste liquid and an oxidizing agent is supplied to a mixed reaction tank supplied with an alkaline solution dropwise or through a pipe. Method for recovering copper from contained acidic waste liquid.

(6) Means for mixing copper-containing acidic waste liquid and oxidizing agent, means for adding a mixed liquid of copper-containing acidic waste liquid and oxidizing agent to a mixing reaction tank, an alkali agent being supplied, A mixed reaction tank for producing an alkaline suspension containing copper oxide by the reaction of an alkaline agent, and a solid liquid for recovering copper oxide from the alkaline suspension containing copper oxide drawn from the mixed reaction tank in communication with the mixed reaction tank A separation device,
Furthermore,
Means for measuring the total amount of copper-containing acidic waste liquid;
And means for controlling the addition of the mixed liquid according to the total amount of the copper-containing acidic waste liquid,
A facility for recovering copper from a copper-containing acidic waste liquid.

(7) Means for mixing copper-containing acidic waste liquid and oxidizing agent, means for pouring a mixed liquid of copper-containing acidic waste liquid and oxidizing agent into a mixing reaction tank, an alkali agent being supplied, A mixed reaction tank for producing an alkaline suspension containing copper oxide by the reaction of an alkaline agent, and a solid liquid for recovering copper oxide from the alkaline suspension containing copper oxide drawn from the mixed reaction tank in communication with the mixed reaction tank A separation device,
Furthermore,
Means for counting the number of times the mixed liquid of copper-containing acidic waste liquid and oxidizing agent is added;
And means for controlling the addition of the mixture according to the number of times of injection,
A facility for recovering copper from a copper-containing acidic waste liquid.

(8) Means for mixing the copper-containing acidic waste liquid and the oxidizing agent, means for pouring the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent into the mixing reaction tank, an alkaline agent being supplied, A mixed reaction vessel for producing an alkaline suspension containing copper oxide by the reaction of an alkaline agent, and a solid reaction vessel for recovering copper oxide from the alkaline suspension containing copper oxide that communicates with the mixed reaction vessel and is extracted from the mixed reaction vessel. A liquid separator,
Furthermore,
Means for measuring the pH of the mixing reactor;
And means for controlling the addition of the mixed solution according to the pH of the mixing tank,
A facility for recovering copper from a copper-containing acidic waste liquid.

  According to the present invention, direct treatment without diluting a high-concentration copper-containing acidic waste liquid having a copper ion content concentration of 5 to 20%, which has been difficult to process by the generation of double salts, etc. with conventional treatment techniques. Moreover, it can be recovered as copper oxide having a low chlorine content.

  In addition, alkaline solutions and copper-containing acidic waste liquids that are usually used for the reaction tend to react well when the liquid temperature is high, and the chlorine content of the produced copper oxide tends to be low. The acidic waste liquid may be pre-warmed, but according to the present invention, it is not particularly necessary to pre-warm the alkaline solution or the copper-containing acidic waste liquid, and the reaction can be started at room temperature. No heating equipment is required.

  Furthermore, since the copper oxide obtained by the method of the present invention has a low chlorine content as described above and can be used as it is as a raw material for the copper plating bath solution, if the apparatus according to the present invention is installed in the plating factory, Copper can be reused, contributing to resource conservation. Moreover, since it becomes unnecessary to discharge | emit the high concentration copper containing acid waste liquid outside, it contributes also to waste reduction.

  In the treatment process by the method for recovering copper from the copper-containing acidic waste liquid of the present invention (hereinafter referred to as “the method of the present invention”), the liquid in the mixed reaction tank is fed into the mixed reaction tank to which a predetermined amount of alkaline solution is supplied. While the pH of the liquid is temporarily controlled so that it does not drop below 9 or less, a mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent is poured into the mixed reaction tank and mixed to obtain a solid mainly composed of copper oxide. An alkaline suspension containing the product is produced. At this time, the amount of the copper-containing acidic waste liquid and the oxidizing liquid mixture added to the mixed reaction tank is at least 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary to neutralize the alkaline solution in the mixed reaction tank. When it exceeds, it is necessary to intermittently pour the mixed liquid into the mixing reaction tank, and in this case, it is necessary to make the pouring pause time 10 minutes or longer. When the amount of this mixed liquid added exceeds at least 0.5 equivalent of the amount of copper-containing acidic waste liquid required to neutralize the alkaline solution in the mixed reaction tank, the mixed liquid is added to the mixed reaction tank. The reason why the additional pause time is 10 minutes or more will be described below. Copper oxide with a low chlorine content is produced up to 0.5 equivalent of the copper-containing acidic waste liquid, but after the copper-containing acidic waste liquid exceeds 0.5 equivalent, Even if the rest time is 3 minutes, only copper oxide having a high chlorine content (about 200 mg-Cl / kg-CuO) is produced. On the other hand, after the addition amount of the copper-containing acidic waste liquid exceeds 0.5 equivalents, the chlorine content of the copper oxide to be produced is reduced (about 10 minutes) when the suspension time of addition of the mixed liquid is set to 10 minutes or more. (100 mg-Cl / kg-CuO).

  The copper-containing acidic waste liquid to be treated by the method of the present invention is not particularly limited by the copper ion concentration and the anion concentration contained therein, as long as it is an acidic waste liquid containing copper in an ionic state. Specific examples of the copper-containing acidic waste liquid that can be particularly preferably treated by the method of the present invention include, for example, an etching waste liquid generated when etching a copper printed board with a cupric chloride etchant, and a plating bath liquid in the production of electrolytic copper foil. Examples include renewed waste liquids such as high copper ion concentration, chloride ion concentration, and sulfate ion concentration.

  The oxidizing agent used in the method of the present invention is not particularly limited as long as it can oxidize divalent copper ions, and various oxidizing agents can be used. However, since it can be handled as a solution and no components other than water remain after the reaction, hydrogen peroxide, ozone water, or the like is suitable as the oxidizing agent in the present invention. Among these oxidizing agents, hydrogen peroxide is particularly suitable for this application because it does not require a special generator and is easy to handle. The concentration in the case of using hydrogen peroxide as the oxidizing agent is not particularly limited, and for example, a commercially available hydrogen peroxide solution of about 30% is easily available. When ozone water is used as the oxidant, gaseous ozone may be directly blown into the copper-containing acidic waste liquid instead of ozone water.

  Furthermore, the alkaline solution used in the method of the present invention is not particularly limited as long as it is a solution containing an alkaline agent. As the alkaline agent used in the alkaline solution, any of various alkaline agents can be used, and the form thereof may be solid or liquid. For the selection of a specific alkali agent, an alkali metal hydroxide that does not form a sedimentary salt with an anion that may coexist in the solution is suitable. On the other hand, the amount of alkaline solution is determined by the amount of copper-containing acidic waste liquid to be processed. That is, in a small-scale experiment, the ratio of the copper-containing acidic waste solution and the alkaline solution that are neutralized when mixed is determined. In actual processing, it is preferable to determine the amount of alkaline solution required based on this ratio.

  When a solid alkali is used as the alkali agent, there is an advantage that an increase in the amount of waste liquid can be suppressed. When a solid alkaline agent is used, the solid alkaline agent may be preliminarily dissolved in water or the like and then supplied to the mixing reaction tank. It may be dissolved with. Furthermore, as the water for dissolving the solid alkaline agent, a separation liquid separated from the solid by solid-liquid separation described later, a washing waste water generated by the washing treatment of the separated solid, and the like can also be used.

  In the method of the present invention, sodium hydroxide is preferred because it is relatively inexpensive and easily available as an alkaline agent. When sodium hydroxide is used, a solid or solution such as flakes or granules can be used. In the case of using a sodium hydroxide solution, the concentration is not particularly limited. For example, a sodium hydroxide solution having a concentration of about 25% can be used.

  Based on the form summarized above, the case where a hydrogen peroxide solution is used as an oxidizing agent and a sodium hydroxide solution is used as an alkaline solution is taken as an example, and a copper-containing acidic waste solution and a hydrogen peroxide solution are mixed. The reaction of adding “mixed solution” to the sodium hydroxide solution will be described below.

  In the treatment process according to the method of the present invention, first, the copper-containing acidic waste solution and the hydrogen peroxide solution are mixed, and this mixture solution is added to the sodium hydroxide solution to react so that the pH does not fall below 9. Order and management are important.

  When cuprous ions are contained in the copper-containing acidic waste liquid, mixing with the hydrogen peroxide solution before bringing it into contact with the sodium hydroxide solution results in the cuprous ions being oxidized by the oxidizing action of the hydrogen peroxide. Since it is oxidized to copper ions, precipitation of cuprous salts such as cuprous chloride (CuCl) can be avoided even in contact with a sodium hydroxide solution.

  In the method of the present invention, the time required for mixing the copper-containing acidic waste liquid and the hydrogen peroxide solution and reacting the copper ions with hydrogen peroxide depends on the concentration of both, but both are high in concentration. In this case, since the oxidation reaction proceeds promptly, the oxidation reaction proceeds sufficiently even for about 5 to 20 seconds.

  On the other hand, when the copper-containing acidic waste liquid and the hydrogen peroxide solution are mixed, the decomposition reaction of hydrogen peroxide proceeds. The decomposition reaction becomes apparent from the time when about 60 seconds have passed after mixing the both, and proceeds violently with remarkable foaming after 7 to 10 minutes. Although it depends on the concentration of both, for example, when mixed with a hydrogen peroxide solution containing hydrogen peroxide twice the molar amount with respect to copper ions in the copper-containing acidic waste liquid, decomposition of hydrogen peroxide The accompanying foaming decreases after 20 minutes and becomes slight after 25 minutes. When added to the sodium hydroxide solution at this point, the oxidizing agent is decomposed, so water is more than copper oxide. A precipitate containing a large amount of copper oxide is formed.

  From the above, it is preferable to take about 5 seconds to 20 minutes, preferably about 20 seconds to 7 minutes, as the mixing / reaction time of the copper-containing acidic waste liquid and the hydrogen peroxide solution.

  The mixture liquid obtained by mixing the copper-containing acidic waste liquid and the hydrogen peroxide solution may be continuously or intermittently added to the sodium hydroxide solution in the mixing reaction tank, but is preferably intermittently performed. By carrying out like this, reaction to the copper oxide of the cupric ion in a liquid mixture advances rapidly, when pouring a liquid mixture into a sodium hydroxide solution and neutralizing. As a method of pouring the mixed liquid, for example, a method of dropping into a mixed reaction tank or a method of supplying the mixed liquid into the liquid through piping is applicable.

  On the other hand, the method of pouring the sodium hydroxide solution is not particularly limited except that it is supplied so as not to be mixed with the mixed solution before reaching the mixed reaction tank. The method of injecting continuously is mentioned. The sodium hydroxide solution can be poured into the mixing reaction tank without heating.

  Next, the reaction between the mixed solution of the copper-containing acidic waste liquid and the hydrogen peroxide solution and the sodium hydroxide solution will be described. Here, in order to avoid the formation of a double salt, it is necessary to carry out the reaction under conditions where the copper concentration as ions is dilute. Moreover, in order to advance the oxidation reaction of copper ions quickly, it is desirable to carry out the reaction under alkaline conditions where the reactivity of the oxidizing agent is high. Therefore, the pH of the liquid in the mixed reaction tank is temporarily 9 or less. Do not go down. It is necessary to manage to 11.5 preferably. Examples of the method for controlling the pH include a method in which a mixed solution of a copper-containing acidic waste liquid and an oxidizing agent is poured into a mixed reaction tank little by little and / or a method in which the mixture is managed by adding an alkali agent. .

  In the state where the pH of the liquid in the mixed reaction tank is controlled as described above, the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent is poured into the mixed reaction tank and mixed, and copper oxide is the main component. It is possible to recover the copper by producing an alkaline suspension containing the solid matter and separating the solid matter from the alkaline suspension, but by further processing as follows: A solid material mainly composed of copper oxide having a low chloride ion content is obtained.

  The method of the present invention, in the above recovery, in the mixed reaction tank when the added amount of the mixed liquid exceeds at least 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary for neutralizing the alkaline solution in the mixed reaction tank. While the liquid mixture is intermittently added to the liquid, the pouring pause time is 10 minutes or longer, preferably 30 minutes. Thereby, the chlorine content rate of the produced copper oxide can be reduced. Here, the intermittent pouring of the mixed liquid is to alternately pour the mixed liquid and pause the mixed liquid. In addition, when the mixed solution is intermittently poured, it is desirable to continuously stir the mixed reaction tank.

  In addition, until the addition amount of the mixed solution reaches at least 0.5 equivalent of the amount of copper-containing acidic waste solution necessary for neutralizing the alkaline solution in the mixing reaction tank, the amount of the mixed solution added to the sodium hydroxide solution On the other hand, if the amount is small enough, the copper-containing acidic waste liquid is neutralized and oxidized while obtaining an appropriate dilution effect.Therefore, the pouring method is not particularly limited, and it may be continuous or intermittent. May be added, but intermittent injection is preferred. Examples of the intermittent pouring condition include a condition in which the pouring is 3 minutes and the rest time is 3 minutes.

  The pause time for pouring can be set based on the addition amount of the mixed solution, the pH of the reaction mixture layer, the number of times of addition of the mixed solution, etc., and can be determined, for example, as follows. That is, while the addition of the mixed solution is intermittently performed, the addition amount of the mixed solution is added up to 0.5 equivalent of the amount of copper-containing acidic waste solution necessary for neutralizing the alkaline solution in the mixing reaction tank. The suspension time is 3 minutes, and the addition pause time when the equivalent exceeds 0.5 equivalents is at least three times the addition pause time up to 0.5 equivalents of the copper-containing acidic waste liquid amount, preferably 10 Just double it.

  One of the more specific embodiments is a method of intermittently adding the mixed solution, corresponding to 0.5 equivalent of the amount of copper-containing acidic waste liquid that neutralizes the alkaline solution supplied to the mixed reaction tank. Until the amount to be added is added, the mixing time interval (resting time) of the mixed solution is 3 minutes, and after exceeding 0.5 equivalent, the mixing time interval (resting time) of the mixed solution is 10 minutes. As mentioned above, Preferably the method of setting it as 30 minutes is mentioned. The time required for pouring the mixed solution is 3 minutes. Here, the reason why the suspension time for pouring the mixed liquid is increased with 0.5 equivalent as a boundary will be described below. As shown in the results of the comparative example described later, when the mixed solution is poured up to the equivalent of 0.5 equivalent with the pouring pause time being 3 minutes, a copper oxide having a chlorine content of less than 100 mg-Cl / kg-CuO is produced. it can. However, the chlorine content increased to about 200 mg-Cl / kg-CuO when the quiescent time of addition to 0.8 equivalent was set to 3 minutes (control series of Examples). On the other hand, when 0.5 eq is used as a boundary, the pause time for addition to 0.5 equivalent is 3 minutes, and when the pause time for addition is more than 0.5 equivalent to 0.8 equivalent is 30 minutes (Run 3 in Example) was able to improve the chlorine content to less than 100 mg-Cl / kg-CuO. Summarizing these findings, the suspension time of pouring when the amount of the acidic waste liquid containing copper that neutralizes the amount of alkaline solution supplied to the mixing reaction tank exceeds 0.5 equivalents is reduced to 0.5 equivalents. Therefore, it was determined that making it longer than the suspension time of the addition was effective in reducing the chlorine content of the recovered copper oxide.

Moreover, the setting method of the additional pause time of another aspect is as follows. A method in which the addition of the mixed solution is intermittently stopped, and the pH of the mixed reaction tank is equivalent to 0.5 equivalent of the copper-containing acidic waste liquid amount necessary for neutralizing the alkaline solution in the mixed reaction tank After being lower than the pH in the state where the acidic waste liquid is added, the suspension time for pouring the mixture is more than 3 times the suspension time for pouring the mixture until the pH is lowered, preferably This is a method of 10 times.
In addition, when the pH of the mixed reaction tank is higher than the pH in the state of adding the copper-containing acidic waste liquid corresponding to 0.5 equivalent of the copper-containing acidic waste liquid amount necessary for neutralizing the alkaline solution in the mixed reaction tank In this case, the pause time for addition may be 3 minutes.

  In this embodiment, the pH of the alkaline agent solution in a state where 0.5 equivalent of the copper-containing acidic waste liquid is added can be specifically determined by the following method. That is, in an experiment on a small scale in advance, a copper-containing acidic waste liquid is added to the alkaline solution to be used, and a neutralization curve is measured. From here, the pH of the alkaline solution when 0.5 equivalent of the copper-containing acidic waste liquid is added is obtained, and this pH may be used as a guideline for setting the rest time.

  Furthermore, as another method for setting the rest time, the amount of the mixed solution added and the pH of the mixed reaction tank correspond to the number of times the mixed solution is added. A method for setting an additional pause time can also be mentioned.

  In any setting method of the pause time, when the number of times of pouring is small, the amount of the mixed liquid, that is, the copper-containing acidic waste liquid is increased, and the dilution effect when mixed with the alkaline solution in the mixing reaction tank is increased. Get smaller. In this case, there is a possibility that copper ions in the mixed solution are not oxidized to copper oxide and copper hydroxide is generated, and it is preferable to determine an appropriate number of times of injection in advance through experiments on a small scale.

  In the method of the present invention, the completion of the treatment is not particularly problematic at any point as long as a solid mainly composed of copper oxide is generated. However, the amount of the mixed solution added is not limited to the alkaline solution in the mixing reaction tank. The amount is 0.5 equivalent or more, preferably 0.8 equivalent of the amount of copper-containing acidic waste liquid required for neutralization. When the reaction is stopped with an addition amount of less than 0.5 equivalent of the copper-containing acidic waste liquid, copper oxide having a low chlorine content can be recovered, but since the supernatant of the reaction slurry has a high pH, Copper remains or the amount of alkaline agent solution required increases. On the other hand, when the copper-containing acidic waste liquid exceeds 0.8 equivalent, the pH of the supernatant of the reaction slurry is close to 7, so that the alkaline agent solution can be used effectively, but the chlorine content of the recovered copper oxide There is a problem that becomes high.

At the end of the treatment, the pH of the liquid in the mixing reaction tank is desirably between pH 9 and 11.5. This is because Cu ²⁺ is produced when the pH is less than 7, and ionic copper such as CuO ₂ ²⁻ is produced when the pH exceeds 11.5. Therefore, both have a copper ion concentration in the solution in the mixed reaction tank. In such a state, the copper concentration of the separated liquid after solid-liquid separation of the purified copper oxide also increases, so that the copper recovery rate deteriorates and the process of removing copper from the separated liquid This is because it is further required. On the other hand, if the pH is lower than 9, the chlorine content of the recovered copper oxide becomes high, and a separate refining operation is required for reuse. Thus, by maintaining the solution in the mixed reaction tank in a state where the copper ion concentration is low, a dilution effect by this can be obtained, and the formation reaction of copper oxide from copper ions by the oxidizing agent by avoiding the formation of double salts Can be maintained and progressed well. Therefore, it becomes possible to deposit copper oxide efficiently.

  After completion of the reaction in the mixing reaction tank, if necessary, stirring is performed for the same amount of time as the resting time. Then, an alkaline suspension containing a solid material containing copper oxide as a main component is drawn out, and the solid suspension (mainly Solid-liquid separation into copper oxide) and separated liquid. For solid-liquid separation, for example, filtration separation, centrifugation, sedimentation separation, etc. can be applied.

  The solids separated from the alkaline suspension are reused because the solids coexist with the alkaline agent contained in the alkaline suspension and the high-concentration salts produced by the neutralization reaction. In order to recover the solid material for the purpose of the above, it is preferable to recover the purified solid material by repeating washing treatment such as water washing a plurality of times in order to wash away salts and increase the purity of the recovered material. The treated water used for the washing treatment includes clear water having a low salt content, such as tap water and industrial water.

  The purified solid thus obtained contains at least 95% or more, generally 98% or more of copper oxide. Moreover, if the reaction conditions are set appropriately, the chlorine content of the purified solid can be reduced to less than 100 mg-Cl / kg-CuO.

  By carrying out the method of the present invention described above, it is possible to generate and recover a solid content mainly composed of copper oxide and having a reduced chloride ion content from the copper-containing acidic waste liquid.

Next, an apparatus used for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram showing an embodiment of a copper recovery apparatus when the present invention is carried out. In the figure, 1 is a copper-containing acidic waste liquid treatment facility, 2 is a mixing reaction tank, 3 is a mixing tank, 4 is a solid-liquid separation apparatus, 5 is a solids purification apparatus, 6 is a purification slurry transfer pump, and 7 is a separation liquid transfer pump. , 8 is a washing drainage transfer pump, 9 is a pH meter, 10 is a stirrer, 11 and 12 are three-way valves, 13 is a copper-containing acidic waste liquid supply pipe, 14 is an oxidant supply pipe, 15 is an alkaline agent supply pipe, and 16 is Stirrer 17 is a controller for controlling valves 18, 19 and 20, 18 is a valve for controlling the supply of a mixed liquid of copper-containing acidic waste liquid and oxidizing agent, and 19 is a valve for controlling the supply of copper-containing acidic waste liquid. , 20 is a valve for controlling the supply of the oxidizing agent, 21 is a valve for controlling the supply of the alkaline agent, 22 is a controller for controlling the valve 21, 23 is a copper-containing acidic waste liquid storage tank, 24 is an oxidizing agent storage tank, 25 Has an alkaline agent storage tank Show.

  In the copper recovery facility shown in FIG. 1, the valve 21 is first opened, a predetermined amount of alkaline agent is supplied from the alkaline agent storage tank 25 through the alkaline agent supply pipe 15 to the mixed reaction tank 2, and an alkaline solution is prepared therein. To do. On the other hand, in the reaction tank 3, the valves 19 and 20 are opened, and the copper-containing acidic waste liquid and the oxidizing agent are supplied to the reaction tank 3 from the copper-containing acidic waste liquid storage tank 23 and the oxidizing agent storage tank 24. In the reaction tank 3, after mixing the copper-containing acidic waste liquid and the oxidant for a predetermined time, the valve 18 is opened, and the mixed reaction tank 2 in which the alkaline solution is stirred by the stirrer 10 is added to the mixed liquid of the copper-containing acidic waste liquid and the oxidant. Supply. At this time, in the mixed reaction tank 2, the pH is measured with the pH meter 9, and when the pH drops, the valve 21 is opened by controlling with the controller 22 so as to maintain the pH 9 or higher, and the alkaline agent is stored in the alkaline agent. The mixed reaction tank 2 is supplied from the tank 25 through the alkaline agent supply pipe 15.

  Further, the amount of the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent is controlled by the controller 17 from the flow rate (not shown) provided in the supply pipe for the copper-containing acidic waste liquid and the number of times of injection. To do. Then, the time interval for supplying the copper-containing acidic waste liquid and the oxidizing agent to the reaction tank 3 and the time interval for supplying the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent to the mixing reaction tank 2 are as follows. It is controlled by the controller 17 by opening and closing. It is also possible to control the addition of the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent by using a variable flow rate pump instead of each valve. In this case, it is possible to continuously add the mixed liquid of copper-containing acidic waste liquid and oxidizing agent by setting the pump flow rate to a flow rate that can maintain a state in which the dilution effect of the mixed solution by the alkaline agent is obtained. is there.

  The reaction is repeated a predetermined number of times with the addition of the copper-containing acidic waste liquid and the oxidizing agent mixture, and after the final addition, the reaction is terminated after a pause. After completion, the alkaline suspension containing copper oxide in the mixed reaction tank 2 is sent to the solid-liquid separation device 4 by the separation liquid transfer pump 7 and separated into a solid and a supernatant. Since the supernatant liquid has a low concentration of soluble copper, it is discharged into sewers and public water areas after simple neutralization and then treated as a general wastewater treatment facility in the factory. Moreover, since the alkali agent remains in the supernatant, it is possible to effectively utilize the alkali agent by supplying the mixture 7 again to the mixing reaction tank 2 using the pump 7. On the other hand, the solid matter from the solid-liquid separation device 4 is sent to the solid matter purification device 5 and washed. Further, it is separated into solid and liquid and recovered as a purified product.

  FIG. 2 is a system diagram showing an embodiment of a copper recovery apparatus when another embodiment of the present invention is implemented. In the figure, 1 is a copper-containing acidic waste liquid treatment facility, 2 is a mixing reaction tank, 3 is a mixing tank, 4 is a solid-liquid separation apparatus, 5 is a solids purification apparatus, 6 is a purification slurry transfer pump, and 7 is a separation liquid transfer pump. , 8 is a washing drainage transfer pump, 9 is a pH meter, 10 is a stirrer, 11 and 12 are three-way valves, 13 is a copper-containing acidic waste liquid supply pipe, 14 is an oxidant supply pipe, 15 is an alkaline agent supply pipe, and 16 is A stirrer, 18 is a valve for controlling the supply of a mixed liquid of copper-containing acidic waste liquid and oxidizing agent, 19 is a valve for controlling the supply of copper-containing acidic waste liquid, 20 is a valve for controlling the supply of oxidizing agent, and 21 is an alkaline agent. , 23 is a copper-containing acidic waste liquid storage tank, 24 is an oxidant storage tank, 25 is an alkaline agent storage tank, 26 is a controller that controls the valves 18, 19, 20, and 21. Show.

  In the copper recovery facility shown in FIG. 2, the valve 21 is first opened, a predetermined amount of alkaline agent is supplied from the alkaline agent storage tank 25 through the alkaline agent supply pipe 15 to the mixed reaction tank 2, and an alkaline solution is prepared therein. To do. On the other hand, in the reaction tank 3, the valves 19 and 20 are opened, and the copper-containing acidic waste liquid and the oxidizing agent are supplied to the reaction tank 3 from the copper-containing acidic waste liquid storage tank 23 and the oxidizing agent storage tank 24. In the reaction tank 3, after mixing the copper-containing acidic waste liquid and the oxidant for a predetermined time, the valve 18 is opened, and the mixed reaction tank 2 in which the alkaline solution is stirred by the stirrer 10 is added to the mixed liquid of the copper-containing acidic waste liquid and the oxidant. Supply. At the same time, the pH of the mixed reaction tank 2 is measured by the pH meter 9, and when the pH is lowered, the valve 23 is opened by controlling with the controller 23 so as to maintain the pH 9 or higher, and the alkali agent is stored in the alkali agent storage tank. 25 is supplied to the mixing reaction tank 2 through the alkaline agent supply pipe 15.

  Further, after supplying the mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent, the pH of the mixed reaction tank 2 is measured with the pH meter 9. Depending on the measurement result of this pH, the time interval for supplying the copper-containing acidic waste liquid and oxidant to the reaction tank 3 and the time interval for supplying the mixed liquid of copper-containing acidic waste liquid and oxidant to the mixing reaction tank 2 The controller 17 is controlled by opening and closing 18, 19, and 20.

  The reaction is repeated a predetermined number of times with the addition of the copper-containing acidic waste liquid and the oxidizing agent mixture, and after the final addition, the reaction is terminated after a pause. After completion of the reaction, the alkaline suspension containing copper oxide in the mixed reaction tank 2 is sent to the solid-liquid separation device 4 by the separation liquid transfer pump 7 and separated into a solid and a supernatant. Among these, since the alkaline agent remains in the supernatant, the alkaline agent can be effectively utilized by supplying the mixed reaction tank 2 again using the pump 7. On the other hand, the solid matter from the solid-liquid separation device 4 is sent to the solid matter purification device 5 and washed. Further, it is separated into solid and liquid and recovered as a purified product.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples at all.

Example 1
Recovery of copper from copper etch effluent:
61 L of copper etching waste solution (pH: 1.2, copper ion concentration: 137 g / L, chloride ion concentration: 257 g / L: hereinafter referred to as this was generated when etching a copper printed board with a cupric chloride etchant. The treatment of “copper etching waste liquid”) was carried out with the apparatus shown in FIG. A 30% hydrogen peroxide solution was used as the oxidizing agent, and a 25% sodium hydroxide solution was used as the alkaline agent.

  In Example 1, in order to set the mixing reaction tank pH at the end of the treatment (reaction end) to 9 or more, the copper etching waste liquid amount (1 equivalent) necessary for neutralizing 25% sodium hydroxide to pH 7 is as follows. 0.8 equivalent copper etching waste solution was supplied to the mixing reaction vessel, and the mixed solution of the copper etching waste solution and the hydrogen peroxide solution was added to the sodium hydroxide solution intermittently in 8 times. The rest period after injection is set to 3 minutes for each Run until the first 5 times (corresponding to 0.5 equivalents), 10 minutes for Run 1 from the 5th to 7th time, 20 minutes for Run 2, and 30 minutes for Run 3 did. Further, the eighth run (corresponding to 0.8 equivalent) was added to each Run to complete the reaction. After completion of the reaction, each Run was continuously stirred for 30 minutes. In addition, the time required for pouring the mixed solution was set to 3 minutes for each Run (for example, FIG. 3 shows the time interval for pouring in Run 3). For comparison, the control series in which the rest time after pouring was fixed at 3 minutes was also processed, and the chlorine content of the recovered copper oxide was compared and evaluated.

<Device>
A stirrer 10 and a pH meter 9 were installed in the mixing reaction tank 2 having a capacity of 370 L. Moreover, the effective volume of the mixing tank 3 in this test apparatus was 10L. The pH meter 9 has a function of measuring the pH of the liquid in the mixed reaction tank 2. In addition, although this test apparatus was equipped with control which maintains pH9 or more, in actual processing, pH was always maintained at 11.5 or more. The stirrer 10 is a ribbon stirrer because it is necessary to stir a high-viscosity suspension containing copper oxide just before the end of the reaction.

<Preliminary test>
Prior to the treatment, neutralization treatment was performed on a small scale in order to obtain the minimum amount of 25% sodium hydroxide solution relative to the amount of copper etching waste liquid to be treated. When the copper etching waste solution was added to the 25% sodium hydroxide solution little by little and the pH with respect to the added amount of the copper etching waste solution was measured, a neutralization curve as shown in FIG. 4 was obtained. From FIG. 4, the amount of the copper etching waste solution for neutralizing 1 mL of 25% sodium hydroxide solution to pH 7 (thick line in FIG. 4) was about 1.15 mL. From this result, the mixing ratio for mixing the copper etching waste solution used in this example with the amount of 25% sodium hydroxide solution to pH 7 was 1.15: 1 in volume ratio.

<Processing operation>
Prior to the treatment, 88 L of tap water was supplied to the mixing reaction tank 2 in order to secure the minimum amount of liquid necessary for stirring the inside of the mixing reaction tank 2. Thereafter, the operation of the agitator 10 was started, and a 25% sodium hydroxide solution 68 L was poured into the mixed reaction tank 2 from the alkaline agent supply pipe 15. After the sodium hydroxide was added, the inside of the mixing reaction tank 2 was stirred, and the pH of the solution was 14 and the liquid temperature was about 25 ° C.

  Next, 7.6 L of unheated copper etching waste liquid was supplied to the mixing tank 3. At the same time, 2.5 L of a 30% hydrogen peroxide solution was supplied to the mixing tank 3. After supplying the copper etching waste liquid and the hydrogen peroxide solution to the mixing tank 3, the mixture was stirred for 3 minutes by the stirrer 16 and mixed.

  After completion of the stirring, 10.1 L of a mixed liquid of copper etching waste liquid and hydrogen peroxide solution was poured into the mixed reaction tank 2. The mixed solution was poured into the mixing reaction tank 2 over 3 minutes. During this addition, the mixing reaction tank 2 was stirred so that the pH in the system was uniform. After completion of the addition of the mixed liquid of the copper etching waste liquid and the hydrogen peroxide solution, stirring of the mixed reaction tank 2 was continued for 3 minutes in each series. After completion of the stirring, 7.6 L of copper etching waste liquid and 2.5 L of hydrogen peroxide solution were mixed and poured into the mixing reaction tank 2 for a total of 5 times. When the pouring operation was completed five times, the supply amount of the copper etching waste liquid was 38 L in total, and the supply amount of the hydrogen peroxide solution was 12.5 L in total. Moreover, the pH of the mixing reaction tank 2 was about 13.4.

  After the pouring operation was completed five times, the resting time of the pouring operation was 3 minutes for the control series, 10 minutes for Run1, 20 minutes for Run2, and 30 minutes for Run3, and stirring was continued during the resting time. Thereafter, 7.6 L of copper etching waste liquid and 2.5 L of hydrogen peroxide solution were mixed, and the operation of pouring and pausing into the mixing reaction tank 2 was repeated three times in total to complete the reaction. When the stirring was continued for 30 minutes after the completion of the reaction, the total supply amount of the copper etching waste liquid was 60.8 L, and the total supply amount of the hydrogen peroxide solution was 20 L. Moreover, the pH of the liquid in the mixing reaction tank 2 was about 11.5, and the temperature of the reaction slurry was 34 ° C.

  Immediately after this, a part of the suspension containing the solid matter mainly composed of copper oxide (hereinafter referred to as “suspension”) is extracted from the lower part of the mixing reaction tank 2 by the transfer pump 6, and the suspension The solid and the liquid were separated by the solid-liquid separation device 4, and a filtrate and black sludge were obtained.

  The obtained black sludge was washed with water, dried, and evaluated by powder X-ray diffractometry. As a result, it was confirmed that copper oxide was the main component (FIG. 5). Table 1 shows the relationship between the chlorine content and the suspending time.

  From Table 1, in Run3 where the rest time from the 1st to 5th injection was 3 minutes and the rest time from the 5th to 8th injection was 30 minutes, the chlorine content decreased to less than 100 mg-Cl / kg-CuO did. From the above results, it was possible to produce copper oxide of quality that can be reused as a raw material for the copper plating bath by extending the pouring interval according to the number of times of pouring. In addition, the soluble copper density | concentration of the filtrate was less than 1 mg / L, and it was the water quality which can be discharged | emitted only by the neutralization process. On the other hand, the control series in which the suspending time of the pouring was 3 minutes from the pouring to the 1st to 8th pouring had a high chlorine content and was about 200 mg-Cl / kg-CuO.

Example 2
In Example 2, in the lab scale test, the chlorine content of the recovered copper oxide when the reaction end point pH was higher than that in Example 1 was evaluated.

  In the test operation, first, 1000 mL of 25% sodium hydroxide solution was placed in a beaker and stirred. Next, 115 mL of the copper etching waste solution and 54 mL of 30% hydrogen peroxide solution were mixed while stirring, and this mixture was poured into the sodium hydroxide solution over 3 minutes. After the end of pouring, the pouring operation was suspended for 3 minutes until the start of the next pouring. During the series of operations, the mixed solution in the beaker was constantly stirred. This addition / stirring was made into one set.

  Thereafter, the copper etching waste solution and the hydrogen peroxide solution were poured into the sodium hydroxide solution and the stirring operation was repeated 5 sets. At this time, the total processing amount of the copper etching waste liquid is 577 mL, which corresponds to 0.5 equivalent of the copper etching waste liquid amount for neutralizing the sodium hydroxide solution prepared in the beaker. After completion of the reaction, stirring was continued for another 30 minutes. Then, when pH of the suspension containing the solid substance which has the produced | generated copper oxide as a main component was measured, it was 13.1. This suspension was subjected to solid-liquid separation, and black sludge was recovered. Further, the black sludge was washed with water and dried to recover black brown copper oxide.

  When the chlorine content of the recovered copper oxide was measured, it was 98 mg-Cl / kg-CuO, and it was possible to produce copper oxide of a quality that could be reused as a raw material for the copper plating bath. However, in Example 2, the amount of the 25% sodium hydroxide solution necessary for treating the copper etching waste liquid is about 1.6 times that in Example 1, so that the amount of the alkaline agent used is increased. On the other hand, after recovering the copper oxide sludge from the suspension after the completion of the reaction, a supernatant of high alkali (pH 13 or more) remained as compared with Example 1, and the alkali agent was not effectively utilized. Moreover, the soluble copper concentration of this supernatant was about 25 mg / L, and it was necessary to remove copper in addition to the neutralization treatment in order to discharge it. Therefore, it was found that the reaction end point pH of the suspension is preferably 12 or less.

  As described above, when a mixed solution of copper etching waste liquid and aqueous hydrogen peroxide solution is intermittently added to a sodium hydroxide solution at room temperature, the chlorine content rate from the copper etching waste liquid is extended by extending the time interval of the addition. Was able to recover and produce low copper oxide.

  According to the present invention, copper in acidic copper waste liquid containing a high concentration of copper, such as etching waste liquid and electrolytic plating bath renewal waste liquid, is efficiently separated as an insoluble oxide in water while avoiding the formation of double salts. The copper solid material that can be recovered and contains the recovered copper oxide as a main component is reusable as a plating material or the like.

  Therefore, the present invention can be used as an economical method for recovering copper from an acidic copper waste solution in the etching industry and the plating industry.

The figure of the processing apparatus of the copper containing acidic waste liquid in this invention. The figure of the processing apparatus of the copper containing acidic waste liquid in another embodiment of this invention. Explanatory drawing of the time interval of the addition in Run3 of Example 1. FIG. The neutralization curve of the copper etching waste liquid in Example 1 and a sodium hydroxide solution. 2 is a peak chart of X-ray diffraction of produced copper oxide in Example 1. FIG.

1: Copper-containing acidic waste liquid treatment facility 2: Mixing reaction tank 3: Mixing tank 4: Solid-liquid separation device 5: Solid matter purification device 6: Purification slurry transfer pump 7: Separation liquid transfer pump 8: Washing wastewater transfer pump 9: pH Total 10: Stirrer 11, 12: Three-way valve 13: Copper-containing acidic waste liquid supply pipe 14: Oxidant supply pipe 15: Alkaline agent supply pipe 16: Stirrer 17: Controller for controlling the valves 18, 19 and 20 18: Valve for controlling the supply of the mixed liquid of copper-containing acidic waste liquid and oxidizing agent 19: Valve for controlling the supply of copper-containing acidic waste liquid 20: Valve for controlling the supply of oxidizing agent 21: Valve for controlling the supply of alkaline agent 22: Controller 21 for controlling valve 21: Copper-containing acidic waste liquid storage tank 24: Oxidant storage tank 25: Alkaline agent storage tank 26: Valve 18, valve 19, valve 20 and valve 21 are controlled Controller

Claims (8)

In a mixed reaction tank to which a predetermined amount of alkaline solution is supplied, a mixed liquid of a copper-containing acidic waste liquid and an oxidant is managed so that the pH of the liquid in the mixed reaction tank is not temporarily lowered to 9 or less. Is poured into the mixing reaction vessel and mixed to produce an alkaline suspension containing a solid material mainly composed of copper oxide, and the solid is separated from the alkaline suspension. A method,
When the added amount of the mixed liquid exceeds at least 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary for neutralizing the alkaline solution in the mixed reaction tank, the mixed liquid is poured into the mixed reaction tank. A method for recovering copper from a copper-containing acidic waste liquid, characterized in that the pause time for pouring is 10 minutes or longer while intermittently performing the step.   When the liquid mixture is added intermittently, and the amount of liquid mixture exceeds 0.5 equivalent of the amount of copper-containing acidic waste liquid required to neutralize the alkaline solution in the mixing reaction tank More than 3 times the suspension time of the addition of up to 0.5 equivalents of the amount of copper-containing acidic waste liquid required for neutralizing the alkaline solution in the mixing reaction tank. The method for recovering copper from the copper-containing acidic waste liquid according to claim 1.   Addition of the mixed solution is intermittently performed, and the pH of the mixed reaction tank is equivalent to 0.5 equivalent of the amount of copper-containing acidic waste liquid necessary for neutralizing the alkaline solution in the mixed reaction tank. After lowering the pH in the state in which the contained acidic waste liquid is added, the suspension time for pouring the mixture is set to be at least three times the suspension time for pouring the mixture until the pH is lowered. A method for recovering copper from a copper-containing acidic waste liquid according to claim 1.   The copper-containing acidic waste liquid according to any one of claims 1 to 3, wherein the pH of the suspension in the mixed reaction tank is controlled by adding a mixed liquid of a copper-containing acidic waste liquid and an oxidizing agent and / or an alkaline agent. Of copper recovery from the water. 5. The copper from the copper-containing acidic waste liquid according to any one of claims 1 to 4, wherein a mixed liquid of the copper-containing acidic waste liquid and the oxidizing agent is supplied to a mixed reaction tank supplied with an alkaline solution dropwise or through a pipe. the method of recovery. An apparatus for carrying out the method for recovering copper from the copper-containing acidic waste liquid according to any one of claims 1 to 5,
Means for mixing copper-containing acidic waste liquid and oxidizing agent, means for pouring a mixed liquid of copper-containing acidic waste liquid and oxidizing agent into a mixing reaction tank, an alkali agent is supplied, and the mixed liquid and the alkaline agent are added. A mixed reaction tank for producing an alkaline suspension containing copper oxide by a reaction, and a solid-liquid separation apparatus for collecting copper oxide from an alkaline suspension containing copper oxide that is communicated with the mixed reaction tank and drawn out from the mixed reaction tank There,
Furthermore,
Means for measuring the total amount of copper-containing acidic waste liquid;
And means for controlling the addition of the mixed liquid according to the total amount of the copper-containing acidic waste liquid,
A facility for recovering copper from a copper-containing acidic waste liquid. An apparatus for carrying out the method for recovering copper from the copper-containing acidic waste liquid according to any one of claims 1 to 5,
Means for mixing copper-containing acidic waste liquid and oxidizing agent, means for pouring a mixed liquid of copper-containing acidic waste liquid and oxidizing agent into a mixing reaction tank, an alkali agent is supplied, and the mixed liquid and the alkaline agent are added. A mixed reaction tank for producing an alkaline suspension containing copper oxide by a reaction, and a solid-liquid separation apparatus for collecting copper oxide from an alkaline suspension containing copper oxide that is communicated with the mixed reaction tank and drawn out from the mixed reaction tank There,
Furthermore,
Means for counting the number of times the mixed liquid of copper-containing acidic waste liquid and oxidizing agent is added;
And means for controlling the addition of the mixture according to the number of times of injection,
A facility for recovering copper from a copper-containing acidic waste liquid. An apparatus for carrying out the method for recovering copper from the copper-containing acidic waste liquid according to any one of claims 1 to 5,
Means for mixing copper-containing acidic waste liquid and oxidizing agent, means for pouring a mixed liquid of copper-containing acidic waste liquid and oxidizing agent into a mixing reaction tank, an alkali agent is supplied, and the mixed liquid and the alkaline agent are added. A mixed reaction tank for producing an alkaline suspension containing copper oxide by a reaction, and a solid-liquid separation apparatus for collecting copper oxide from an alkaline suspension containing copper oxide that is communicated with the mixed reaction tank and extracted from the mixed reaction tank Because
Furthermore,
Means for measuring the pH of the mixing reactor;
And means for controlling the addition of the mixed solution according to the pH of the mixing tank,
A facility for recovering copper from a copper-containing acidic waste liquid.