JP2005221808A - Method for utilizing photographic effluent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of coping with environment harming factors remaining in a treated effluent after electrolytic oxidation treatment of a photographic effluent, and to provide a method for utilizing the treated effluent. <P>SOLUTION: In the method for utilizing a photographic effluent, the photographic effluent is subjected to electrolytic oxidation treatment using a conductive diamond electrode as an anode and the treated photographic effluent is used as an aqueous sulfuric acid solution. This aqueous sulfuric acid solution is used as an acid extractant or as a flocculant after conversion to aluminum salt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the use of photographic waste liquid (synonymous with photographic processing waste liquid), and more specifically, processed waste liquid that still has an environmental hindrance after waste liquid treatment to reduce the environmental burden of photographic waste liquid. The present invention relates to a method of utilizing this rather than the conversion processing.

  The photographic waste liquid contains a high concentration of BOD, COD, nitrogen and phosphorus, and a large amount of hardly decomposable components remain even by biological treatment or chemical treatment. Photo waste liquid is one of the most difficult to process among various industrial waste liquids, and many processing methods have been disclosed so far, but there are still many problems in terms of removal rate and processing cost. A processing method that does not require much labor for the laboratory is to consign the incineration of the waste liquid to an industrial waste disposal contractor, which is usually performed as a practical means, but the incineration process requires fossil fuel. It is a processing means that involves problems from the viewpoint of environmental conservation.

  Various methods related to biological treatment, chemical treatment and physical treatment have been disclosed for photographic waste liquid treatment methods that do not rely on incineration. Among them, chemical treatment, especially electrolytic oxidation treatment, has restrictions on equipment space and working conditions. This is a waste liquid processing method that can be carried out on-site at a developing laboratory and is advantageous from this point of view.

However, the fixing waste liquid component contains thiosulfate, which is oxidized during the electrolytic treatment to produce sulfuric acid, and the waste liquid is acidified with the progress of electrolysis of the photographic waste liquid. Therefore, it is necessary to take measures against waste acid to dispose of it.
Patent Document 1 discloses a method in which waste sulfuric acid is mixed with carbonated lime, slaked lime, quicklime, etc., and reused as hydraulic gypsum. Patent Document 2 discloses a method in which waste acid is neutralized with steel slag and reused as a structural material containing a hydraulic gypsum component. These waste acid and waste sulfuric acid recycling methods are considered to be effective as a means for reusing waste acid and waste sulfuric acid from the above specified emission sources. Even if it is acidified, the utilization method shown in Patent Documents 1 and 2 cannot be conceived because the photographic waste liquid is a mixture of various organic and inorganic oxidizing and reducing compounds. .

  Furthermore, the electrolytic oxidation treatment of photographic waste liquid has a weak point that the electrode life is reduced due to the consumption due to the corrosion of the electrode. On the other hand, the lead dioxide electrode and heavy metal electrode with excellent oxidation resistance were used. In some cases, the eluted electrode material is an environmentally hazardous substance and there is a risk of new environmental pollution. On the other hand, platinum and platinum / iridium electrodes have strong acid resistance, but the overvoltage for water electrolysis is low, so water decomposition occurs and oxygen is generated, resulting in low decomposition efficiency of environmental load components in the waste liquid. There are inconveniences. Further, when a carbon electrode such as graphite (for example, a glassy carbon electrode), which is a non-metallic electrode, is used as an anode, electrode consumption is excessive, and the electrode life is short. In such an electrode with low electrode consumption, the liquid to be processed is acidified and contaminated with heavy metals, and there is a lack of a method in which the durability of the electrode is satisfied and the photographic waste liquid after electrolytic oxidation treatment does not hinder the environment. It is the actual situation.

  In contrast to this situation, Patent Document 3 discloses that even with the same carbon electrode, a tetrahedral crystal, that is, a diamond-structured carbon electrode (conductive diamond electrode) has a high electrolysis overvoltage of water even with respect to photographic waste liquid. It has been shown that the generation of oxygen is suppressed and the total organic carbon amount and chemical oxygen consumption can be reduced with high electrolysis efficiency. Moreover, the conductive diamond electrode (hereinafter also simply referred to as diamond electrode) has a high degree of oxidation resistance, and is advantageous in that the electrode consumption, heavy metal contamination of the liquid to be treated, and generation of gas are suppressed. However, the photographic waste liquor that has been subjected to electrolytic oxidation treatment is further acidified and does not comply with the general drainage standards as it is, so that it cannot be drained into the sewage system.

The above-mentioned prior art relating to the invention of this application includes the following documents.
JP-A-11-228134 JP 7-178394 A Tokubo No. 3428888

  The present invention has been made from the background described above, and its purpose is to provide a method for dealing with environmental inhibition factors still remaining in the treated waste liquid after electrolytic oxidation treatment of the photographic waste liquid. As a specific means of the above-mentioned coping method, a method of utilizing the electrolytically oxidized waste liquid is presented.

  The present inventor has used a diamond electrode as an anode in the course of earnestly studying a method for utilizing the acidity of a treated waste liquid by reversely utilizing the phenomenon that a photographic waste liquid is acidified during electrolytic oxidation. As a result of further investigations focusing on this fact, it was found that oxidation proceeds to a low pH value not seen in the case of Was able to reach.

(1) A method for utilizing a photographic waste solution, wherein the photographic waste solution is electrolytically oxidized using a conductive diamond electrode as an anode, and the treated photographic waste solution is used as an aqueous sulfuric acid solution.
(2) Whether the photographic waste liquid is a waste liquid containing 0.1 to 5.0% by mass of halide ions or a waste liquid containing 0.1 to 5% by mass of halide ions prior to the electrolytic oxidation treatment. Alternatively, 0.1 to 5% by mass of halide ions is added to the photographic waste solution during electrolytic oxidation treatment, and the method for utilizing the photographic waste solution according to (1) above.
(3) The method for utilizing a photographic waste liquid as described in (1) or (2) above, wherein silver is recovered from the electrolytically treated photographic waste liquid, and then the photographic waste liquid from which the silver has been recovered is used as an aqueous sulfuric acid solution.
(4) The method for utilizing a photographic waste liquid according to any one of (1) to (3) above, wherein aluminum sulfate is obtained by adding aluminum metal or an oxide thereof to the sulfuric acid aqueous solution.
(5) The method for utilizing a photographic waste liquid as described in (4) above, wherein the aluminum sulfate is a flocculant for water treatment.
(6) Utilization of photographic waste liquid as described in any one of (1) to (5) above, wherein electrolytic oxidation treatment of photographic waste liquid is performed in a minilab, and the obtained sulfuric acid aqueous solution is used as a raw material for aluminum sulfate. Method.

The feature of the method of utilizing the photographic waste liquid of the present invention is that, when a diamond electrode is used as an anode when electrolytic oxidization treatment is performed on the photographic waste liquid, the electrolysis of water hardly occurs, so the components of the photographic waste liquid are decomposed at a high decomposition rate. This is because the phenomenon found this time that the solution concentration of the liquid to be treated is reduced and the electrolytic oxidation proceeds to a very low pH level, resulting in a high acid concentration / low contamination aqueous solution, is used for recycling the photographic waste liquid.
That is, a photographic waste liquid that is subjected to electrolytic oxidation using a diamond electrode is sulfuric acid, is strongly acidic with a pH of 3 or less, and has a low coexisting component concentration. However, it can be used as an acid agent in applications where a certain degree of tolerance is acceptable.
The reason for this solution composition is that thiosulfate ions and sulfite ions are oxidized to sulfate ions among the coexisting components, and many organic components are oxidized and decomposed to carbonate ions to form carbon dioxide gas or nitrogen gas. It is thought to be volatilized.

  The electrolytically oxidized photographic waste solution can be used as an acid agent in the chemical industry and other manufacturing processes as an aqueous sulfuric acid solution, and as a phosphoric acid extractant from phosphorus ore, it is converted into aluminum sulfate, a coagulating sedimentation agent, a mordant, It can be used for applications such as cleaning aids.

The effect of the present invention is that the oxidation power is enhanced when 0.1 to 5.0% by mass of halide ions are present in a photographic waste solution, and it is effective for electrolysis of organic components, particularly organic nitrogen compounds. Is large, and is highly effective in highly acidifying the liquid to be treated and reducing impurities. Therefore, when the above-mentioned amount of halide ions is not contained in the photographic waste liquid, it is also preferable to add the halide ions so as to have the above amount during the electrolytic treatment. Further, addition of halide ions may be performed during the electrolytic treatment.
Preferred halide ions are chlorine ions and bromine ions. These counter cations are alkali metal ions and ammonium ions, preferably sodium ions, potassium ions and ammonium ions.
The photographic waste solution contains a silver compound derived from a light-sensitive material, and therefore it is preferable to collect it appropriately. It may be recovered from a bleach-fixing tank or a fixing tank during photographic processing, or from the waste liquid after photographic processing. It may be recovered. In particular, in the latter case, as will be described later in the process of electrolytic oxidation of the waste liquid, the method of collecting the precipitate as a mixed precipitate with iron oxide or the like at the time of removing the precipitate is to obtain crude silver from the obtained precipitate. Since iron oxide is also processed at the same time during the refining process, no additional disposal is required, which is advantageous.
Since the electrolytic oxidation treatment can be automatically performed by a simple operation using an electrolytic apparatus, it can be performed on a small scale in a minilab.

  By using a photographic waste solution that is obtained by using, as a sulfuric acid aqueous solution, a photographic waste solution that is electrolytically oxidized using a conductive diamond electrode as an anode, it is possible to use the electrolytically oxidized waste solution. According to this utilization method, it is possible to treat photographic waste liquid without adversely affecting the environment.

Hereinafter, the present invention will be described in more detail.
[Treatment waste liquid]
Prior to the description of the embodiment of the present invention, the photographic processing waste liquid that is the subject of the invention will be described. The photographic processing waste liquid contains many kinds of waste liquids generated in the photographic industry such as fixing waste liquid or photolithography, in addition to development waste liquid for color photography or monochrome photography. As the fixing waste liquid, the residual liquid from which the dissolved silver is recovered becomes the object of processing. Usually, waste liquids from these various photographic processing steps are collected and processed in a mixed state.
The development waste liquid constituting the photographic waste liquid is the waste liquid discharged from each step of the development processing, and components such as gelatin and photosensitive dye eluted from the photosensitive material during the processing, reaction products generated during the processing, and It is a waste liquid that contains constituent chemicals that have not been consumed by being included in the treatment liquid formulation (details of the treatment liquid formulation will be described later).

  Color developer waste mainly contains developing agents and their oxidation products, alkali agents, buffer agents, preservatives selected from sulfites and hydroxylamine derivatives, alkali halides, etc. Mainly ammonium salt and / or sodium salt, sulfite ammonium salt and / or sodium salt, alkali halide, etc., bleaching waste liquid is bleaching agent such as iron (III) complex salt of polyaminopolycarboxylic acid and reaction product derived therefrom , Alkali halides (rehalogenating agents), buffer salts, etc. The bleach-fixing waste liquid is mainly composed of the same components as those contained in the fixing waste liquid and the bleaching waste liquid, and is discharged from other processes. The waste liquid also contains the functional compounds of those process liquids and the compounds derived therefrom. Therefore, the components of the photographic waste liquid to be processed include components derived from a developer, components derived from a bleaching solution, a fixing solution, and a bleach-fixing solution, which are mixed with a photosensitive material eluate and a reaction product during processing. Agents (carbonates, phosphates, borates, tetraborate, hydroxybenzoates, etc.), color developing agents, sulfites, hydroxylamine salts, carbonates, water softeners, alkylene glycols, benzyl alcohols , Surfactant (alkylphosphonic acid, arylphosphonic acid, fatty acid carboxylic acid, aromatic carboxylic acid, etc.), oxidizing agent (iron (III) EDTA complex salt, 1,3-diamino-propanetetraacetic acid complex salt, etc.), halide ( It contains a wide variety of chemical components such as alkali bromide and ammonium bromide), thiosulfate (sodium salt, ammonium salt), and acetate. Further details of the components derived from the processing liquid of the photographic waste liquid will be described in the section of photographic processing described later.

Various photosensitive material additive components and their reaction products are also eluted from the photosensitive material into the processing solution during the processing. Silver halide elutes into the processing solution as silver complex salts and halide ions, and is accompanied by the photosensitive dye (color sensitizer), fog prevention, chemical sensitization, and other purposes. The nitrogen-containing heterocyclic compound, the compound released from the coupler or DIR compound (in many cases, a nitrogen compound) is eluted in the treatment liquid. Further, the surfactant and the like are eluted from the binder of the photosensitive layer. Further details of the compound eluted from the light-sensitive material are described in the section of light-sensitive material described later.
Therefore, the photographic processing waste liquid has an oxygen-consuming compound, nitrogen compound, sulfur compound, iron complex salt and high salt concentration derived from the processing solution and the photosensitive material as described above. Although this diversity makes effective waste liquid treatment means difficult, the present invention leads to the solution.

The composition of photographic waste liquid varies considerably depending on the type of treatment and the mixing ratio of waste liquid from each step of the treatment, but it is roughly COD 30,000-50,000 mg / l, BOD 5,000-15,000 mg / l, TOC (Total Organic Carbon) The range is 10,000-25,000 mg / l, Kjeldahl nitrogen 10,000-15,000 mg / l, and total phosphorus 100-500 mg / l. The ratio of COD: BOD: TOC is approximately 4: 1: 1.5, which is characterized by high COD, and the element ratio of C: N: P is approximately 100: 100: 1, and is characterized by a high N content.
The photographic waste liquid contains a large amount of hardly biodegradable compounds, making it difficult to treat the waste liquid only by biological treatment means. The main non-biodegradable compounds are bleaching agents and developing agents such as the iron (III) chelates described above.

  The photographic waste solution which is the subject of the present invention contains a sulfur source necessary for sulfation in the form of thiosulfate, sulfite and the like. These are mainly derived from the desilvering treatment solution. Many photographic waste liquids have a total sulfur content of 0.5 to 10 g / L, more often 1.0 to 15 g / L.

In addition, the COD, total nitrogen amount, ammonia nitrogen, and the like of the photographic waste liquid in this specification are indices used as normal environmental data, and are COD _Mn and total nitrogen specified in JIS K0102 (Industrial Wastewater Test Method). The amount is based on the test method for ammoniacal nitrogen. In the case of photographic waste liquid, the amount of ammoniacal nitrogen can be accurately approximated by determining the total nitrogen content of the compound that becomes ammoniacal nitrogen from the prescription value and usage ratio of each processing solution used in photographic processing. This approximate value calculation means may be used.

[Electrolytic oxidation treatment process]
<Adjustment of photographic waste liquid>
In the present invention, it is not always necessary to adjust the pH of the photographic waste solution in advance prior to the electrolytic treatment. As the electrolytic oxidation proceeds, the pH decreases and the acid concentration increases, but the pH may be adjusted in advance to a low value, for example, in the range of 2.0 to 4.0.

  Electrolytic oxidation is most effective when carried out in a state in which the photographic waste solution contains an alkali halide, particularly NaCl, in an amount of 0.1 to 5.0% by mass (based on chlorine ions). Therefore, if the photographic waste liquid is a waste liquid containing, for example, 0.1% by mass or more, preferably 0.1 to 5% by mass of NaCl, it is not necessary to add NaCl further. It is preferable that 0.1 to 5.0% of NaCl is contained in advance, for example, or 0.1 to 5.0% of NaCl is added during the electrolytic oxidation treatment. In the case of adding an alkali halide during the electrolytic oxidation treatment, it is preferable to add the alkali halide before the pH of the waste liquid is lowered to 4.0 or less from the viewpoint of maintaining electrolytic efficiency.

The reason why the effect of the present invention is particularly remarkable when the pH is 4.0 or less and an alkali halide is present is that, in the case of anodization in the presence of an alkali halide, halogen ions such as chlorine ions are present. Although it is oxidized to hypochlorite ions, the equilibrium relationship between hypochlorous acid and Cl ₂ and H ₂ O depends on pH, and the equilibrium moves to the Cl ₂ and H ₂ O side, which is more It is believed to provide a strong oxidizing environment (in the case of bromine ions, hypobromite, Br ₂ and H ₂ O). An increase in the electrolytic oxidation effect in the low pH region and in the presence of NaCl is effective in reducing both the oxygen consumption and the total nitrogen amount, but particularly contributes greatly to the reduction in the total nitrogen amount.

<Electrolytic oxidation operation>
The temperature of the electrolytic oxidation treatment is preferably room temperature or slightly higher than this, the voltage is preferably 5.0 to 8.0 V, and the current density is preferably 0.005 to 1 A / cm ² , more preferably 0.01 to 0.5 A. / cm ² is good. The electrolysis may be either a batch method or a continuous method.
Depending on the degree of electrolytic oxidation treatment, under preferred conditions, this process using a diamond anode reduces the COD in the effluent to 10-90% and to a level that meets the general wastewater standards for the sewerage law. A further great advantage of the electrolytic oxidation treatment is that not only the oxygen consumption expressed by COD but also the total nitrogen amount mainly composed of ammoniacal nitrogen can be effectively reduced.

  A large amount of halide ion is generally present in the photographic waste liquid. Therefore, chlorine ions are oxidized at the anode by electrolysis to produce chlorine, and a part of the chlorine further reacts with water to produce hypochlorite ions, so that the oxidation activity is increased. Therefore, it is preferably applied for the purpose of the present invention. Is done. On the other hand, since the electrolytic solution is highly corrosive, it is necessary to select platinum, ferrite, stainless steel, iron on which an oxide film is rapidly formed, etc., which are corrosion resistant materials that can withstand these components. The cathode material does not directly participate in this electrolytic oxidation reaction, but platinum, stainless steel, etc., which are inactive to the reaction solution, are preferable. In addition, since the reaction solution contains a large amount of suspended components, a rotating cathode is preferable in order to prevent precipitation of the suspended matter on the electrode, cause a uniform oxidation reaction, and increase current efficiency. .

  The anode used for the electrolytic oxidation is a conductive diamond electrode that is excellent in corrosion resistance even in electrolysis at pH 4 or lower, and this enables efficient electrolysis of the hardly decomposable substance in the waste liquid. In the present invention, “conductive diamond electrode” means a diamond electrode having an electrical resistivity of less than 1 MΩcm, but “conductive” may be omitted as long as there is no risk of misunderstanding.

  Diamond, which is the electrode material of the present invention, is a plate of titanium, niobium, tantalum, silicon, carbon, nickel, tungsten carbide, etc., a punched plate, a wire mesh, a powder sintered body, a metal fiber sintered body, etc. The surface may be coated by the method described later, and plate-like diamond may be used as an electrode as it is, but the former is desirable from the viewpoint of cost. In the present specification, the diamond coating layer in the former is referred to as a diamond layer. An intermediate layer is preferably provided between the substrate and the diamond layer for the purpose of ensuring adhesion and protecting the substrate. As the material of the intermediate layer, a metal carbide or oxide constituting the substrate can be used. The substrate surface may be polished to contribute to adhesion and reaction area increase, or conversely roughened. In addition to diamond, the electrode material may contain a small amount of another electrode material.

  As a method for forming the diamond layer on the substrate surface, a hot filament CVD method, a microwave plasma CVD method, a plasma arc jet method, a PVD method, and the like have been developed. Next, a typical hot filament CVD method will be described. An organic compound such as alcohol serving as a carbon source is maintained in a reducing atmosphere such as hydrogen gas, and maintained at a temperature of 1800 to 2400 ° C. at which carbon radicals are generated. At this time, the electrode substrate is placed in another temperature (750 to 950 ° C.) region where diamond is deposited. The preferable organic compound gas concentration with respect to hydrogen is 0.1 to 10% by volume, the supply rate is 0.01 to 10 liters / minute depending on the dimensions of the reaction vessel, and the pressure is 15 to 760 mmHg. The diamond fine particles usually have a particle size of about 0.01 to 5 μm. In the present invention, diamond powder is vapor-deposited on the substrate according to the above conditions to form a diamond layer having a thickness of 0.1 to 50 μm, preferably 1 to 10 μm. To do. This thickness is suitable for preventing the electrolyte from entering the substrate. In order to impart good conductivity to the formed diamond layer, it is necessary to add a small amount of elements having different valences (doping). For example, phosphorus or boron is added in an amount of 1 to 100,000 mg / L, preferably 100 to 10,000 mg / L. About L is contained. As a raw material compound of this additive, boron oxide, diphosphorus pentoxide, etc., which are less toxic are preferable.

  For doping to provide sufficient electrical conductivity, it is preferable to use a plasma enhanced CVD (PECVD) diamond deposition method. Details of the method of manufacturing the doped electrode are described, for example, in Ramesham, Thin Solid Films, Vol. 229 (1993) 44-50. The PECVD diamond layer is boron doped polycrystalline diamond made from a mixture of methane and hydrogen gas activated by microwave plasma. The deposition of diamond layers by this method is well understood by those skilled in the art (see, for example, Klages, Appl. Phys. A56 (1993), 513-526).

Diamond electrodes manufactured by the hot filament CVD (HFCVD) method (see Klages, Appl. Phys. A56 (1993) pp. 513-526) are CSEM SA (Centre Suisse d'Electronique et de Microtechnique SA, Jaquet-Droz 1 , CH- 2007 Neuchatel Switzerland) and is commercially available from Mitsui & Co. Plant Co., Ltd.
As a method for producing the diamond electrode, a chemical vapor deposition method in a vacuum chamber described in JP-A-8-225395, paragraph 0007 is also preferable.

  As a cathode for electrolytic oxidation of photographic waste liquid, any material can be used as long as it has sufficient corrosion resistance and electric conductivity so as not to cause corrosion during the rest period of electrolysis, but a stainless plate or rod is particularly suitable. . However, other electrodes such as carbon electrodes and various metal electrodes can also be used. Appropriate shapes such as a cathode / anode pair shape, a sandwich structure in which the anode is sandwiched between the anodes from both sides, or a multiple-sheet arrangement structure in which the cathodes and anodes are alternately arranged are selected. The shape of the cathode may be any of a linear shape, a rod shape, a plate shape, and the like.

  As one embodiment of the present invention, a conductive diamond electrode can also be used for the cathode. Moreover, when using a conductive diamond electrode for both electrodes, it is preferable to perform electrolysis while reversing the polarity in order to maintain the electrode in a normal state. That is, since calcium ion, magnesium ion hydroxide, and the like adhere to the cathode surface of the electrolytic cell, periodic scale removal is necessary. In order to prevent the adhesion of scales, there have been reported devices for reversing the polarity of electrodes for a very short time (Japanese Patent Laid-Open Nos. 3-109988, 5-4087, 6-63558, etc.). When these methods are used, the deposits on the cathode surface of the electrolytic cell are converted into calcium ions and magnesium ions by reversing the polarity of the electrodes, that is, by positively polarizing the adhesion surfaces of the hydroxides, etc. Electrolysis is possible while redissolving in and removing from the electrode. As long as both poles have the same shape, the reversal interval and time need not be specified.

  The voltage drop during energization at the conductive diamond electrode depends on the resistivity and thickness of the diamond layer, and the resistivity and thickness of the substrate, and the resistance at the connection to the electrode, so the conductivity of the substrate and the diamond layer and The junction to the power supply is preferably designed to be negligible for the overall voltage drop at the electrode assembly.

Since the current density of electrolytic oxidation using a diamond electrode is generally about 10 mA / cm ² and the voltage drop at the electrode is in the range of 10 to 100 V, the power consumption, which is the product of the square of the current value and the resistance value, is extremely high. It becomes large and considerable energy is lost due to resistance heating.
Accordingly, the preferred electrode for the present invention has a sufficiently thin diamond layer thickness (less than 5 μm) and a sufficiently high electrical conductivity so that the diamond layer has a resistivity of less than 1 MΩcm.

However, a more preferred electrode is an electrode having a diamond layer with a resistivity of less than 100 Ωcm and a thickness of less than 1 V with a current density of 100 mA / cm ² . Such an electrode functions at a suitable current density and with little power loss resulting from resistance heating. The most preferred electrode is an electrode having a resistivity of less than 0.1 Ωcm, a current density of 1 A / cm ² and a thickness such that the voltage drop across the electrode is less than 0.1V.

  In the present invention, the structure of the electrolytic cell can be used in various known configurations. That is, it may be a single chamber cell or a divided cell in which the anode and the cathode are partitioned by a film. The simplest embodiment is a single chamber cell. In a single chamber cell, there is no barrier separating the anode and cathode, so the solute is not restricted from moving between the anode and cathode. Such a single-chamber method generally has a possibility that the component oxidized at the anode is subsequently reduced at the cathode, but in the present invention, the electro-oxidative decomposition reaction of the components of the photographic waste liquid is mostly performed. Is the destruction of C—H and C—C bonds and the formation of C—O and O—H bonds, and the oxidized species undergoes almost irreversible oxidation, and thiosulfate and sulfite ions are oxidized to stable sulfate ions. There is no possibility of that risk.

  In a two-chamber cell, a conductive membrane such as an ion exchange membrane, a microfiltration membrane, a semipermeable membrane, or a porous membrane is inserted between the anode and the cathode, and this membrane only allows certain types of ionic species from the anolyte. It can be passed through the catholyte or vice versa. The function of the membrane is to maintain electrical neutrality without mixing the anolyte and catholyte. In addition, if an appropriate film is used, the nature of ions moving through the film can be controlled.

However, since the durability of the membrane is limited in the two-chamber cell, management such as appropriate replacement is necessary so as not to cause fouling.
About the use of a single chamber cell and a two chamber cell, use of a single chamber cell is preferable from the standpoint of simplicity. However, a two-chamber cell is a more preferred form if proper management and process control of the diaphragm is possible.

  For electrolytic oxidation in the present invention, any of a batch method, a recirculation method, and a continuous method may be used, and the most convenient method can be appropriately selected according to the scale of waste liquid treatment and the degree of treatment.

  An electrochemical cell containing a diamond layer electrode keeps the gap between the electrodes as small as possible without creating a direct contact or short circuit between the anode and the cathode. Large interelectrode distances over several centimeters are acceptable, but the preferred interelectrode gap is in the range of 0.1 mm to 50 mm, and the most preferred state is the interelectrode gap in the range of 0.5 mm to 20 mm. .

The electrolytic oxidation of the photographic waste liquid in the present invention is a geometric electrode having a current density of 1 mA / cm ^{2 to} 10 A / cm ² , a flow rate / cell volume ratio of 0.001 to 1000 min ⁻¹ , and an electrode surface area measured by a microscope. It is preferred that the surface area be equal to or greater than the surface, in particular 1 to 5 times the surface of the geometric electrode. More preferably, however, the current density is in the range of 20 mA / cm ^{2 to 2} A / cm ² and the flow rate / cell volume ratio is 0.01 to 50 min ^−1. was ^{50mA / cm 2 ~800mA / cm 2} , flow rate / cell volume ratio is in the range of 1～20Min ^-1, electrode surface area, is the case at least twice the geometric electrode surface area as measured by a microscope.
Although the preferred energization amount depends on the COD of the waste liquid to be treated, it is usually 0.5 MQ or more, preferably 1 to 10 MQ, more preferably 2 to 8 MQ per liter of photographic waste liquid (MQ is megacoulomb). .

<Removal of precipitate>
The pH of the photographic waste solution subjected to the electrolytic oxidation treatment is extremely low, and as a result of the decomposition of the ammonium / iron complex compound in the waste solution, the iron salt is changed into a compound that is hardly soluble in water. In the present invention, from the viewpoint of utilizing the waste liquid after the electrolytic oxidation treatment, it is preferable to remove precipitates generated during the electrolytic oxidation treatment using a sedimentation tank or a filtration device.
In addition to iron sulfide and iron oxide / iron hydroxide, the precipitate contains silver sulfide and silver halide, so that silver can be recovered and reused as a silver resource. The mode of separation and removal by sedimentation or filtration of the precipitate will be described in detail in FIGS.
<Exhaust>
In addition, since acid gases such as sulfurous acid gas and chlorine gas are generated along with the electrolytic oxidation of photographic waste liquid, in the electrolytic oxidation treatment, equipment using a column filled with an adsorbent that can be adsorbed and desorbed, a gas absorption tower, etc. It is preferable to perform electrolysis while collecting the exhaust gas from the exhaust gas.
<Aspects of electrolytic oxidation>
FIG. 1 shows an embodiment of the electrolytic oxidation apparatus used in the present invention equipped with a sedimentation tank, but an apparatus of another embodiment can also be used. In the embodiment shown in FIG. 1, used waste liquid discharged from the developing processor is stored in the waste liquid tank 1. The stored waste liquid is sent to the electrolytic cell 4 through the liquid feed pipe 3 by the liquid feed pump 2, where electrolytic oxidation is performed. The waste liquid containing the generated precipitate in a dispersed state after electrolytic oxidation is returned to the waste liquid tank 1 by the reflux pipe 5, and the used waste liquid and the electrolytically oxidized waste liquid from the developing processor are put into the waste liquid tank. Stored in a mixed state.

  On the other hand, the waste liquid mixed and stored in the waste liquid tank is sent to the sedimentation tank 8 via the liquid feed pipe 7 by the liquid feed pump 6, where sedimentation separation is performed, and the precipitate 9 and the supernatant layer are collected. 10 is separated. The precipitate 9 is extracted from an extraction port (not shown) and sent to the silver recovery means. The supernatant layer 10 is returned to the waste liquid tank 1 by the reflux pipe 18. In this way, an electrolytic oxidation circulation system including the waste liquid tank 1 and the electrolytic tank 4 and a precipitation separation circulation system including the waste liquid tank 1 and the sedimentation tank 8 are formed. The spent waste liquid is repeatedly circulated through both circulation systems to reduce the total nitrogen amount and oxygen consumption and to remove the generated precipitate (including silver). When the indicated potential in the electrolytic cell 4 reaches a specified value, when the current value of the electrolytic cell during constant potential electrolysis reaches a specified value, or when the electrolysis ends when the electrolytic oxidation time reaches a preset time The waste liquid that has been subjected to electrolytic oxidation is discharged from the electrolytic cell 1.

  The settling tank may be used for activated sludge treatment of waste water. The flow of the liquid in the settling tank is not required because it is sufficient that the reflux liquid from the settling tank is sufficiently exchanged in the waste liquid tank. If the flow rate is too high, the settling becomes insufficient. On the other hand, the circulation between the electrolytic tank and the waste liquid tank is preferably faster because liquid exchange (stirring) on the electrode surface is a factor for promoting electrolysis efficiency. FIG. 1 shows an example of such a speed relationship between the electrolytic oxidation circulation system and the precipitation separation circulation system as 5 L / min and 0.1 L / min. This speed relationship is an example, and an appropriate ratio is selected depending on the size of the apparatus.

The mode of the sedimentation separation method is not limited to the batch type mode shown in FIG. 1, but is an embodiment in which an electrolytic cell and a sedimentation tank are connected in series and performed in a continuous mode, and two or more sedimentation separation tanks are serially connected. It is also possible to select a distributed mode and a parallel mode.
Moreover, the system which isolate | separates a sediment with a small apparatus volume for a short time by centrifugal sedimentation can also be used. In addition, depending on the use of the aqueous sulfuric acid solution obtained by electrolytic oxidation, it is not necessary to remove the precipitate.

When the precipitate separating and removing means is a filtration device, the basic configuration of the apparatus is substantially the same as the sedimentation separation method except for the difference in the precipitate separating and removing means, and is not shown here. However, one example thereof is illustrated in the examples (see FIG. 3).
As a filtration membrane (filter) attached to the filtration device, a UF membrane, an RO membrane, a porous polymer single membrane filter, a ceramic single membrane filter, and a pulp fiber filter can be used. Any one having a pore size of 0.05 to 50 μm, preferably 0.1 to 30 μm, more preferably 0.2 to 10 μm may be used.
Specifically, single membrane filters of porous polymers such as vinyl chloride, polyethylene, polypropylene, polybutylene, polysulfone, acrylonitrile, porous glass, unglazed plates, igneous rock plates, ceramic single membrane filters such as foaming nitride, filter paper , 0.01 denier fiber (nylon, polypropylene, polyethylene) fiber filter, and the like. Commercially available products of these filters include various Yumicron membranes manufactured by Yuasa Co., Ltd., Millipore filters manufactured by Millipore (for example, Millipore AA, DA, HA, PH, GS, FG, UC, UM, US, GU, HP). Etc.), Kuraray Co., Ltd. microfiltration filters (SF-301, SF-101, SF-401), Gore-Tex manufactured by Gore-Tex, and the like.

As the filtration method, any method can be used as long as the precipitate can be sufficiently collected by the filtration membrane in a relatively short time. Preferably, it is preferable to filter in a sealed state with a uniform pressure of 0.1 to 0.8 kg / cm ² . As the filtration method using the filtration device, a single-pass method of allowing the liquid to pass through the filter device once is sufficient, but a multi-stage single-pass method, a single-stage to multi-stage circulation method, or the like may be used depending on circumstances. What is necessary is just to select suitably the shape or magnitude | size of the filtration membrane used for this invention according to the objective, a use, etc. More preferably, a bag-type filtration membrane is used, a treatment liquid is introduced from the outside thereof, and a filtrate is flowed out from the inside of the bag-type filtration membrane.

  The separation / removal of the precipitate may be performed by a method in which a sedimentation tank is installed to remove the precipitate. The flow of the liquid in the settling tank only needs to be at a speed at which the liquid is sufficiently exchanged with the waste liquid tank. If the flow rate is too high, the settling is insufficient, which is not preferable. On the other hand, the circulation between the electrolytic cell and the waste liquid tank is preferable because it is a factor of the liquid exchange (stirring) electrolytic efficiency on the surface of the electrolytic cell.

  By the electrolytic oxidation treatment of the previous stage of the present invention, the photographic waste liquid has been processed to a level at which the oxygen consumption and, if necessary, the total nitrogen amount can be discharged to the sewer, and when the electrolytic oxidation proceeds to this level, the generated sulfuric acid concentration becomes rare. It is raised to a level that can be sufficiently applied to various uses as acid sulfuric acid.

[Photo processing solution]
The photographic processing waste liquid applied to the present invention has a photographic processing liquid component as a main component, but the photographic processing waste liquid includes an oxidized form of a developing agent generated in the photographic processing process in addition to a material added to the photographic processing liquid. In addition, reaction products such as sulfates and halides, and trace amounts of gelatin, photosensitive dyes, surfactants and the like dissolved from the photosensitive material are contained.

  The photographic processing solution is used for processing color photographic materials and black-and-white photographic materials. Color photographic materials to be processed include color paper, color reversal paper, color negative film for photography, color reversal film, film negative or positive film, Direct positive color light-sensitive materials can be used, and examples of black-and-white light-sensitive materials include X-ray film, printing light-sensitive material, microfilm, and black-and-white film for photographing.

  Photographic processing solutions include color processing solutions, black-and-white processing solutions, reducers for plate making operations, and developing processing tank cleaning solutions. Black-and-white developing solutions, color developing solutions, fixing solutions, bleaching solutions, bleach-fixing solutions, and image stabilization Liquid and the like.

  The color developer usually contains an aromatic primary amine color developing agent as a main component. It is mainly a p-phenylenediamine derivative, and typical examples are N, N-diethyl-p-phenylenediamine, 2-amino-5-diethylaminotoluene, 2-methyl-4- [N-ethyl-N- (β- Hydroxyethyl) amino] aniline, N-ethyl-N- (β-methanesulfonamidoethyl) -3-methyl-4-aminoaniline. These p-phenylenediamine derivatives are salts such as sulfate, hydrochloride, sulfite, and p-toluenesulfonate. The content of the aromatic primary amine developing agent ranges from about 0.5 g to about 10 g per liter of developer.

  In the black-and-white developer, 1-phenyl-3-pyrazolidone, 1-phenyl-4-hydroxymethyl-4-methyl-3-pyrazolidone, N-methyl-p-aminophenol and its sulfate, hydroquinone and its sulfone Contains acid salts.

  Color and black-and-white developers usually contain sulfites such as sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium metasulfite, potassium metasulfite and carbonyl sulfite adducts as preservatives. These contents are 0 g to 5 g per liter of the developer.

  Color and black and white developers contain various hydroxylamines as preservatives. Hydroxylamines may be substituted or unsubstituted. Examples of the substituent include those in which the nitrogen atom of hydroxyalumines is substituted by a lower alkyl group, particularly N, N-dialkyl-substituted hydroxylamines substituted by two alkyl groups (for example, 1 to 3 carbon atoms). It is done. A combination of N, N-dialkyl-substituted hydroxylamine and alkanolamine such as triethanolamine is also used. The content of hydroxylamines is 0 to 5 g per liter of developer.

  Color and black-and-white developers have a pH of 9-12. Various buffering agents are used to maintain the pH. Examples of the buffer include carbonate, phosphate, borate, tetraborate, hydroxybenzoate, glycine salt, N, N-dimethylglycine salt, leucine salt, norleucine salt, guanine salt, 3,4- Dihydroxyphenylalanine salt, alanine salt, aminobutyrate, 2-amino-2-methyl-1,3-propanediol salt, valine salt, proline salt, trishydroxyaminomethane salt, lysine salt and the like can be used. In particular, carbonate, phosphate, tetraborate, and hydroxybenzoate are excellent in solubility and buffering ability in a high pH range of pH 9.0 or higher, and adversely affect photographic performance even when added to a developer. There is an advantage that there is no (fogging etc.) and it is inexpensive, and these buffering agents are often used. The amount of the buffer added to the developer is usually 0.1 mol to 1 mol per liter of the developer.

  In addition, various chelating agents are added to the developer as an anti-precipitation agent for calcium and magnesium or to improve the stability of the developer. Representative examples thereof include nitrilotriacetic acid, diethylenetriaminepentaacetic acid, nitrilo-N, N, N-trimethylenemethylene phosphonic acid, ethylenediamine-N, N, N ′, N′-tetramethylenephosphonic acid, 1,3-diamino-2 -Propanoltetraacetic acid, transcyclohexanediaminetetraacetic acid, 1,3-diaminopropanetetraacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid . These chelating agents may be used in combination of two or more as required.

  The developer contains various development accelerators. Development accelerators include thioether compounds, p-phenylenediamine compounds, quaternary ammonium salts, p-aminophenols, amine compounds, polyalkylene oxides, 1-phenyl-3-pyrazolidones, hydrazines, and mesoionic types. Compounds, thione compounds, imidazoles and the like.

  Many color paper color developers contain a silylene glycol or benzyl alcohol along with the above color developing agent, sulfite, hydroxylamine salt, carbonate, hard water softener and the like. On the other hand, color negative developers, color positive developers, and some color paper developers do not contain these alcohols.

  The developer often contains bromine ions for the purpose of fog prevention, but a developer containing no bromide ions may be used for a photosensitive material mainly composed of silver chloride. In addition, compounds that give chlorine ions such as NaCl and KCl may be contained as an inorganic antifoggant. In many cases, it contains various organic antifoggants. Examples of the organic antifoggant may include adenines, benzimidazoles, benztriazoles, and tetrazoles. The content of these antifoggants is 0.010 g to 2 g per liter of the developer. These antifoggants include those that elute from the photosensitive material during processing and accumulate in the developer. In particular, the present invention can be effectively treated even in a waste liquid in which the total halogen ion concentration such as bromine ion and chlorine ion is 1 mmol or more per liter of the mixed liquid as described above. This is particularly effective when the bromine ion concentration is 1 mmol or more per liter of the mixed solution.

  Further, the developer contains various surfactants such as alkylphosphonic acid, arylphosphonic acid, fatty acid carboxylic acid, and aromatic carboxylic acid.

  In black-and-white photographic processing, fixing processing is performed after development processing. In color photographic processing, a bleaching process is usually performed between the development process and the fixing process, and the bleaching process may be performed by bleach-fixing (brix) simultaneously with the fixing process. The bleaching solution contains iron (III) or Co (III) EDTA as an oxidizing agent, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, 1,3-diamino-propanetetraacetate, phosphonocarboxylate, other persulfates, and quinones. Etc. are included. In addition, rehalogenating agents such as alkali bromide and ammonium bromide, borates, carbonates and nitrates may be contained as appropriate. Fixing solutions and bleach-fixing solutions usually contain thiosulfate (sodium salt, ammonium salt), acetate salt, borate salt, ammonium or potassium alum sulfite.

  In the processing of a silver halide photographic light-sensitive material, it is common to perform a fixing process or a bleach-fixing process, followed by washing with water and / or a stabilizing process. In the washing process, there may be a problem that bacteria propagate in the processing tank and the generated suspended matter adheres to the photosensitive material. As a solution to such a problem, a method of reducing calcium ions and magnesium ions described in JP-A-61-131632 can be used in washing water. In addition, the isothiazolone compounds described in JP-A-57-8542, siabendazoles, chlorinated fungicides such as sodium chlorinated isocyanurate, and other benzotriazoles, Hiroshi Horiguchi, “Chemistry of Antibacterial and Antifungal Agents” In some cases, the bactericides described in “Technology for Sterilization, Sterilization, and Antifungal of Microorganisms” edited by the Japanese Society for Hygiene and “Encyclopedia of Antibacterial and Antifungal Agents” edited by the Japanese Society for Antibacterial and Antifungal Studies may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely by Examples 1-4, these do not limit the scope of the present invention at all.

<Photo waste liquid sample>
Using the digital minilab FRONTIER340E (manufactured by Fuji Photo Film Co., Ltd.) as a photographic waste solution for testing, print printing is performed from a color negative to a commercially available color paper (Fuji Color Paper Super), and the processing agent CP-49E for Fuji Color Paper is used. Development, bleach-fixing, washing with water, and overflow liquid from each bath, that is, a mixture of development waste liquid, bleach-fixing waste liquid, and water washing waste liquid were used.

<Electrolytic cell>
As an electrolytic cell, “Diacel” (registered product name) equipped with a conductive diamond electrode on the anode purchased from Mitsui & Co. Plant Co., Ltd. was used. The electrode area is 70 cm ² for both the positive and negative electrodes, the distance between the electrodes is 10 mm, and the electrolytic cell volume is 70 cc.
The cathode and the anode were made to face each other, the current density was set to 0.1 A / cm ^2, and the waste liquid tank having a volume of 1 L and the electrolyzed liquid inside the electrolytic cell were circulated by the pump at 2 L / min.

  The electrolytic cell used for the Example is shown in FIG. As shown in FIG. 2, the electrolytic cell is arranged so that the anode 11 and the cathode 12 are opposed to each other with a liquid layer composed of an annular spacer 15 interposed therebetween, and the whole is made up of the disk-shaped outer frames 13 and 14 of polyvinylidene chloride. It has a structure that is bonded together. The disc-shaped outer frames 13 and 14 are provided with liquid passing ports 16 and 17, respectively. The photographic waste liquid is introduced into the lower portion of the anode chamber through the liquid passing port 16, and is electrolytically oxidized to be passed through the upper portion of the electrolytic cell. 17 is sent out.

<Electrolysis>
Prior to electrolysis, 10 g of NaCl per liter of waste liquid was added to the photographic waste liquid, and the pH was used without adjustment. Electrolytic oxidation was performed at a current amount of 30 A while circulating 1 L of the photographic waste liquid at a rate of 2 L / min in the electrolytic cell. The electrolyzer used was a filter provided with a filter membrane for removing precipitates in the waste liquid circulation path. The iron salt / silver salt mixed precipitate generated in the electrolysis process is removed from the waste liquid by this filtration device and sent to a silver recovery system. The waste liquid had a pH of 4 or less after 3 hours from the start of electrolysis, and further decreased to pH 2 while electrolysis was continued. In this state, the pH change almost disappeared, and electrolysis was performed for 24 hours.

FIG. 3 is a schematic configuration diagram of the apparatus used for the test, and a precipitate removing filtration device 26 is provided between the reflux pipes 25 and 28 from the electrolytic cell 24 to the waste liquid tank 21. The waste liquid that has passed through the filtration membrane is recovered to the reflux pipe 28, and the filtration residue is recovered from the outlet 27. The filtration residue was precipitated silver sulfide and iron hydroxide, and the amount of COD _Mn and ammoniacal nitrogen during filtration was analyzed according to the method defined in JIS method (JIS K0102, industrial wastewater test method).
The obtained electrolytically treated waste liquid had a pH of 2.0, COD _Mn of 70 mg / L, and ammoniacal nitrogen content of 210 mg / L. From these values, it was shown that the oxygen-consuming component and the nitrogen-containing component were removed to a level that can be used as an aqueous sulfuric acid solution in many applications that do not require high purity as an acid agent.

The electrolytically treated waste liquid obtained in Example 1 was caused to flow down at the exchange rate (SV, specific volume) 6 from the top of the packed tower packed with bauxite ground to 30 mesh, and the falling liquid was recovered as an aluminum sulfate-containing liquid. The pH of the falling solution was 5.5-8.
When this aluminum sulfate-containing liquid was used as a flocculant for sludge settling in a coagulation sedimentation tank of a waste liquid treatment facility using laboratory activated sludge, the sludge was coagulated and settled at a normal rate, and this was partially used as return sludge. The MLSS during the waste liquid treatment process was successfully managed. That is, it was confirmed that the aluminum sulfate-containing liquid obtained in this example had good separation performance.

The electrolytically treated waste liquid obtained in Example 1 was allowed to flow down at the exchange rate (SV) 6 from the top of the packed tower packed with mordenite (high silica natural zeolite) ground to 20 mesh, and the falling liquid was used as an aluminum sulfate-containing liquid. It was collected. The pH of the falling solution was 6.5-8.
When 1% by volume of this aluminum sulfate-containing liquid is added as a flocculant to a treated wastewater storage tank discharged from a septic tank for domestic wastewater treatment, a transparent supernatant layer is obtained, Good separation results were obtained.

  The phosphate ore containing calcium phosphate as a main component was pulverized by a ball mill to obtain a 120 mesh powder. The packed tower filled with this ore powder is filled with the electrolytically treated waste liquid obtained in Example 1 up to the top, extracted for 24 hours while stirring with bubbles, and then the phosphoric acid concentration of the liquid to be treated is adjusted by a conventional method. As a result of wet quantitative analysis, the phosphoric acid concentration was 1.0 g / L (phosphorus basis).

The electrolytic oxidation treatment shown in Example 1 was performed on-site in a minilab to obtain an electrolytically treated waste liquid, that is, an aqueous sulfuric acid solution.
Subsequently, the sulfuric acid aqueous solution was filled up to the upper end of the tank in a filling tank filled with mordenite (high silica natural zeolite) pulverized to 10 mesh, and complete air blowing stirring was performed for 24 hours. An aqueous solution of sulfuric acid treated with zeolite was extracted from the bottom of the filling tank, cooled to the refrigerator temperature, and recrystallized from aluminum sulfate 18 hydrate.
The obtained crystalline aluminum sulfate 18 hydrate can be used as a photographic processing agent for fixing solution preparation. Moreover, since this hydrate salt is a solid substance and can be easily transported, it can be transported to a wastewater treatment plant and used as a coagulating sedimentation agent.

  The crystalline aluminum sulfate 18 hydrate obtained in Example 5 was redissolved in pure water and purification by recrystallization was repeated. Crystalline aluminum sulfate 18 hydrate with a purity usable as a mordant was obtained.

It is the schematic of the one aspect | mode of the electrolytic oxidation apparatus of the photographic waste liquid which has a sedimentation tank which can be used for this invention. It is explanatory drawing which shows the structure of the electrolytic vessel of the electrolytic oxidation apparatus used for the Example. It is the schematic of the one aspect | mode of the electrolytic oxidation apparatus of the photographic waste liquid which has the filtration tank used for the Example.

Explanation of symbols

1. Waste liquid tank 2. 2. Liquid feed pump 3. Liquid feeding pipe 4. electrolytic cell Reflux tube 6. 6. Liquid feed pump 7. Liquid feeding pipe 8. Settling tank Precipitate 10. Supernatant layer 18. Reflux tube 21. Waste liquid tank 24. Electrolyzer 25, 28. Reflux tube 26. Filtration device 27. Outlet

Claims (6)

  A method for utilizing a photographic waste solution, wherein the photographic waste solution is electrolytically oxidized using a conductive diamond electrode as an anode, and the treated photographic waste solution is used as an aqueous sulfuric acid solution.   The photographic waste liquid is a waste liquid containing 0.1 to 5.0% by weight of halide ions, or is a waste liquid containing 0.1 to 5% by weight of halide ions prior to electrolytic oxidation treatment, or a photograph The method for utilizing a photographic waste liquid according to claim 1, wherein 0.1 to 5 mass% of halide ions is added to the waste liquid during electrolytic oxidation treatment.   The method for utilizing a photographic waste liquid according to claim 1 or 2, wherein the silver is recovered from the photographic waste liquid during or after the electrolytic treatment, and then the photographic waste liquid from which the silver has been recovered is used as an aqueous sulfuric acid solution.   The method for utilizing a photographic waste liquid according to any one of claims 1 to 3, wherein aluminum sulfate or aluminum oxide is added to the sulfuric acid aqueous solution to obtain aluminum sulfate.   The method for utilizing a photographic waste liquid according to claim 4, wherein the aluminum sulfate is a flocculant for water treatment.   The method for utilizing a photographic waste liquid according to any one of claims 1 to 5, wherein the electrolytic oxidation treatment of the photographic waste liquid is performed in a minilab, and the obtained sulfuric acid aqueous solution is used as a raw material for aluminum sulfate.

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