JP5289082B2 - Waste liquid treatment method - Google Patents

Description

  The present invention relates to a waste liquid treatment method capable of removing and recovering hypophosphorous acid and / or phosphorous acid contained in a waste liquid.

  Examples of the waste liquid include those containing phosphorus compounds such as sodium hypophosphite and sodium phosphite, such as electroless plating waste liquid. For this reason, if waste liquid containing a high concentration of phosphorus compounds is discarded as it is into rivers and lakes, algae and other aquatic organisms grow and the water quality is cumulatively deteriorated. Increase the value and COD value. Therefore, from the viewpoint of environmental hygiene, it is required to remove the phosphorus compound when discarding such waste liquid.

  On the other hand, phosphorus is a necessary substance for plant growth. However, since there are not many total phosphorus resources in the world, a way to reuse phosphorus removed from waste liquid is being sought to compensate for this. The organic phosphorus compound and orthophosphoric acid can be easily removed by alkali coagulation precipitation and biological treatment, coagulation precipitation with lime, etc., and the removed phosphorus compound can be reused as a fertilizer. However, phosphorus compounds dissolved as hypophosphite ions and phosphite ions require an extremely long electrolytic oxidation treatment in general agglomeration treatment, and are particularly stable in hypophosphorous acid. Since a complex salt was formed, it could hardly be processed by coagulation precipitation.

  In view of such circumstances, several methods for treating hypophosphorous acid and phosphorous acid have been proposed. For example, to a phosphite-containing waste liquid, add a little excess of slaked lime and equimolar amount of mineral acid over the reaction stoichiometry relative to the amount of phosphorous acid, and react in a neutral to alkaline region while heating There is a method of recovering calcium phosphite (see Patent Document 1).

  However, since this method uses only phosphorous acid as the main target substance, it is necessary to oxidize hypophosphorous acid in order to treat it including hypophosphorous acid, so hypophosphorous acid is recovered. It was difficult.

  In addition, as a method for treating both hypophosphorous acid and phosphorous acid by oxidizing them to regular phosphoric acid, for example, a titanium dioxide carrying a noble metal while keeping a plating aging solution containing hypophosphite ions at pH 1 to 4 Titanium dioxide with noble metal supported by coexisting powder as a photocatalyst, irradiating light while sending oxygen or air, oxidizing hypophosphite ions to phosphate ions, and then filtering while maintaining pH at 1-3 A method of collecting powder has been proposed (see Patent Document 2). However, in this method, when treating a waste liquid containing hypophosphite ions or phosphite ions at a high concentration, not only a treatment time of 50 hours or more is required, but also an oxidation reaction and a filtration operation are performed. Since the treatment is performed under strong acidic conditions, a separate neutralization treatment is required when the plating aging solution after removing the phosphorus compound is discarded.

  In addition, there is a waste liquid containing ammonium ions together with a phosphorus compound such as hypophosphorous acid or phosphorous acid, such as an electroless nickel plating waste liquid. In the case of such a waste liquid, ammonium ions remain dissolved even after the phosphorus compound is removed, and discarding it as it is in a river or the like leads to eutrophication of water quality. Therefore, it is desirable to remove the ammonium ion together with the phosphorus compound. However, it is difficult to realize this with the existing processing method, and no method has been proposed that can simultaneously process both the phosphorus compound and the ammonium ion.

JP-A-9-99288 JP-A-6-136549

  Therefore, the present invention provides a method for oxidizing phosphorous compounds such as hypophosphorous acid and phosphorous acid contained in the waste liquid to phosphoric acid in a short time, and efficiently recycles the phosphorus in the waste liquid. It is an object of the present invention to provide a waste liquid treatment method that can be removed and collected.

  Means taken by the present invention in order to solve the above-mentioned problems include hypophosphorous acid and / or phosphorous acid-containing waste liquid, at least a pair of electrodes each composed of an anode electrode and a cathode electrode, and vibration agitating means. The waste liquid treatment method is characterized in that the electrolytic treatment is performed by supplying to an electrolytic treatment tank.

  As a means for increasing the oxidation efficiency by electrolytic treatment, it is conceivable to stir the waste liquid. However, propeller-type agitation does not provide a sufficient agitation effect, and aeration agitation may mix hydrogen generated by electrolysis with oxygen contained in the supplied air to form an explosion. However, it is not a suitable stirring means. Therefore, by employing vibration agitation that provides a sufficient agitation effect without adversely affecting the electrolytic treatment, hypophosphorous acid or phosphorous acid can be oxidized with high efficiency.

  Moreover, while adding a magnesium compound to a waste liquid, it can also electrolyze in presence of an ammonium ion and can form a magnesium ammonium phosphate crystal | crystallization.

This is a method of insolubilizing phosphoric acid obtained by oxidizing hypophosphorous acid or phosphorous acid by electrolytic treatment as magnesium ammonium phosphate (MgNH ₄ PO ₄ .6H ₂ O) crystals. The method for obtaining magnesium ammonium phosphate crystals from phosphoric acid in this way is called “MAP method”. For the progress of this reaction, the presence of magnesium ions (Mg ²⁺ ) and ammonium ions (NH ⁴⁺ ) is indispensable together with phosphate ions (PO ₄ ²⁻ ). That is, this reaction can proceed by adding a magnesium compound and an ammonium salt to the waste liquid that has been subjected to electrolytic treatment to dissolve magnesium and ammonium ions. However, in the case of a waste liquid in which a sufficient amount of ammonium ions is already dissolved, it is not necessary to add an ammonium salt or the like separately. For example, if an ammonium ion is already contained like an electroless plating waste liquid, it is possible to advance the reaction using this.

  In this case, a step of separating the magnesium ammonium phosphate crystal may be included. As a separation method, various physical separation methods such as aggregation, precipitation, and membrane separation can be used.

  Thus, by depositing magnesium ammonium phosphate crystals, it is possible to easily remove and recover the phosphoric acid from the waste liquid by physical separation means. In this case, if the waste liquid to be treated is a waste liquid containing ammonium ions such as an electroless plating waste liquid, it is possible to simultaneously remove not only phosphoric acid but also ammonium ions that cause water pollution.

It is also possible to add calcium compounds to the waste liquid to form calcium phosphate crystals. That is, by adding a calcium compound to the waste liquid, phosphoric acid obtained by electrolytic treatment reacts with calcium ions (Ca ²⁺ ) to obtain calcium phosphate crystals.

  In this case, a step of separating the calcium phosphate crystals may be included. As a separation method, various physical separation methods such as aggregation, precipitation, and membrane separation can be used.

  By separating the calcium phosphate crystals, phosphoric acid can be easily removed from the waste liquid and recovered.

  Moreover, since heavy metal ions may be contained in the waste liquid, the heavy metal ions contained in the waste liquid may be insolubilized by sulfiding treatment. In the waste liquid, heavy metals such as nickel, cobalt, copper, tin, silver, and platinum may be present as ions, for example, as in the electroless plating waste liquid. In this case, it is not preferable from the viewpoint of environmental hygiene to dump these heavy metal ions into a river or the like without any treatment. Therefore, when treating a waste liquid containing heavy metal ions, the heavy metal ions may be sulfurized to be insolubilized and removed before electrolytic treatment.

  The anode electrode may be a lead dioxide electrode. In order to oxidize and convert hypophosphorous acid or phosphorous acid into phosphoric acid by electrolytic treatment, an anode electrode having a strong oxidizing power is required. For this reason, it is good to use the lead dioxide excellent in oxidizing power for the electrode for anodes in which the oxidation reaction of hypophosphorous acid or phosphorous acid is performed.

  According to the waste liquid treatment method of the present invention, hypophosphorous acid and / or phosphorous acid can be converted into phosphoric acid with high efficiency by subjecting the waste liquid to electrolytic treatment while vibrating and stirring. Thereby, it is possible to remove and recover the phosphorus compound from the waste liquid in a reusable form.

It is a figure which shows the 1st specific example of an electrolytic treatment tank provided with a vibration stirrer. It is a figure which shows the 2nd specific example of an electrolytic treatment tank provided with a vibration stirrer. It is a figure which shows the 3rd specific example of an electrolytic treatment tank provided with a vibration stirrer. It is a figure which shows an example of the vibration absorption (rolling prevention) mechanism in a vibration stirrer. It is a figure which shows an example at the time of providing a rubber-like ring in a vibration stirrer. It is a figure which shows an example of the vibration blade board in a vibration stirrer. It is a graph explaining the relationship between the length of a diaphragm blade and the degree of bending. It is a top view of an electrolytic treatment tank provided with a vibration stirrer used in each example and each comparative example.

  The waste liquid treatment method according to the present invention comprises treating a waste liquid containing phosphorous acid and / or hypophosphorous acid with electrolytic oxidation while performing vibrational stirring, thereby converting phosphorous acid and / or hypophosphorous acid into normal phosphorus. It converts to acid.

  The waste liquid treatment method according to the present invention can be applied to any kind of waste liquid containing hypophosphorous acid or phosphorous acid, and in particular, an electroless plating waste liquid containing a large amount of these phosphorus compounds. Suitable for processing.

  For the implementation of the waste liquid treatment method according to the present invention, for example, an electrolytic treatment tank 5 having a vibration stirrer 22 as shown in FIGS. 1 to 3 is used. The vibration agitator 22 illustrated in FIGS. 1 to 3 includes a vibration motor 1, a vibration transmission member 2, a vibration rod 6 connected to the vibration motor 1, and a single-stage or multi-stage vibration blade plate 7 fixed to the vibration rod 6. Is provided. Then, the vibrating blade plate 7 is “stained” by the vibration of the vibration motor 1, so that the waste liquid is vibrated and flowed and stirred.

  Further, as shown in FIG. 4, the vibration stirrer 22 and the electrolytic treatment tank 5 include three or more, preferably four support rods 41 extending downward from the vibration transmission member 2 and correspondingly electrolytic treatment. A support bar 42 extending upward from the tank 5 side is preferably engaged by a spring 3 surrounding them. In particular, it is preferable that the upper and lower support bars 41, 42 are kept in a state where they are not in contact with each other by the spring 3. As a result, even if rolling occurs in the vibration agitator 22, the rolling can be absorbed by the engaging portion of the spring 3, so that the stability of the entire apparatus at the time of operation is improved and noise generation is also prevented. can do.

The degree of vibration is usually about 10 to 60 Hz, but may be increased to about 500 Hz when the frequency is desired to be increased. When operating at a high frequency, the vibration transmitting member 2
Since cracks and breaks due to concentration of vibration stress may occur in the vicinity of the contact portion between the vibration rod 6 and the vibration rod 6, it is preferable to provide means for dispersing vibration stress in this portion.

  As an example of the vibration stress distribution means, a rubber ring may be provided around the vibration rod below the vibration transmission member at the connection portion between the vibration transmission member and the vibration rod. It is longer than the diameter of the rod, usually 3 to 8 times the diameter of the vibrating rod, and its thickness is 1.3 to 3 times, especially about 1.5 to 2.5 times larger than the diameter of the vibrating rod. preferable. Specifically, when the vibrating bar is a round bar having a diameter of 10 to 16 mm, the thickness of the rubber ring is preferably 10 to 15 mm, and when the vibrating bar is a round bar having a diameter of 20 to 25 mm, The wall thickness is preferably 20 to 30 mm.

  In order to connect the vibration rod to the vibration transmission member, for example, as shown in FIG. 5, the vibration rod 6 is passed through a predetermined hole of the vibration transmission member 2, and nuts 9, 10, and washer rings are inserted from the end of the vibration rod 6. 13 to fix. Then, the rubber ring 15 can be inserted into the lower part of the vibrating rod 6 from the lower side of the vibration transmitting member 2 and fixed by the nuts 11, 12 and the like.

  The rubber ring described above can be made of a hard elastic body having a Shore A hardness of 80 to 120, preferably 90 to 100, such as hard natural rubber, hard synthetic rubber, and synthetic resin. In particular, a hard urethane rubber having a Shore A hardness of 90 to 100 is preferable from the viewpoint of durability and chemical resistance.

  Generation of vibration is performed using a vibration motor that generates vibration of 25 to 500 Hz, preferably 25 to 400 Hz, particularly preferably 25 to 300 Hz. The relationship between the output of the vibration motor and the stirring capacity is approximately as follows in the case of a normal aqueous solution.

If the output of the vibration motor is 3 KW, it is possible to sufficiently agitate a 100 m ³ capacity one.

  Usually, the vibration motor is set on a pedestal placed on an electrolytic treatment tank, a side wall, or a hard floor. Since the thickness of the electrolytic treatment tank is thin (for example, 5 mm or less in the case of a stainless steel tank), it is preferable to install a pedestal outside the electrolytic treatment tank when the vibration of the waste liquid is transmitted to the side wall or the floor surface. Further, a reinforcing member may be attached to the side wall of the electrolytic treatment tank in such a manner as to tighten the band, and a vibration agitator may be installed there.

  The vibration generated by the vibration motor is transmitted to the vibration rod through the vibration transmission member. As shown in FIG. 2 and FIG. 3, the vibration motor is provided so as to be hung downward as shown in FIG. It is effective for.

  For example, as shown in FIGS. 2 and 3, the mount 4 is placed on the electrolytic treatment tank 5, and the vibration transmission member 2 is then connected via the support rods 41 and 42 with the spring 3 as shown in FIG. 4. And the vibration motor 1 is attached thereto. The vibration motor 1 may be mounted above the vibration transmission member 2 as shown in FIGS. 2 and 3, but if it is attached below as shown in FIG. Shake can be suppressed. In addition, the vibration motor is not necessarily provided on the electrolytic treatment tank. For example, the vibration transmission member is extended to the outside of the electrolytic treatment tank, and the vibration motor is attached to the upper side or the lower side of the extended vibration transmission member. The vibration may be transmitted to the vibrating rod.

  Moreover, as shown in FIG.1 and FIG.2, two vibrating bars 6 can also be attached to the both sides of the vibration motor 1, and only one can be attached as shown in FIG. When two are attached, the vibrating blade plate 7 can be attached as shown in FIGS. 1 and 2, and when only one is attached, the vibrating blade plate 7 can be attached as shown in FIG. .

  The vibration width at the tip of the vibration blade plate by the vibration motor is preferably about 3.0 to 20 mm. The frequency of the vibration motor is determined by the setting of the inverter, but the frequency of the vibration blade is usually 200 to 3000 vtm (frequency / minute), preferably 400 to 800 vtm, and the rotation speed of the vibration motor is usually 400 to 4000 rpm. is there.

  The vibration blade plate is fixed by a vibration blade plate fixing member, a plurality of vibration blade plates are stacked, or a vibration blade plate and a vibration blade plate fixing member are integrally molded. Can be used.

  As a material of the vibration blade plate, preferably, a thin metal, plastic, elastic synthetic resin, rubber, or the like can be used. For example, titanium, aluminum, copper, iron, stainless steel, or an alloy thereof can be used as the material of the metal vibrating blade plate. Moreover, as a material of the synthetic resin diaphragm, for example, polycarbonate, vinyl chloride resin, polypropylene, or the like can be used.

  The thickness of the vibration blade plate is not particularly limited as long as at least the tip portion of the vibration blade plate causes flutter phenomenon (a state in which a wave is struck, that is, a state in which bending occurs) due to the vibration of the vibration motor. However, in general, 0.2 to 2.0 mm is preferable when made from metal, and 0.2 to 1.0 mm, particularly 0.5 mm is preferable when made from stainless steel. Moreover, when producing from a plastic, 0.5-10 mm is preferable. Furthermore, when producing from a synthetic resin and rubber | gum, generally 1.0-5.0 mm is preferable. Moreover, the vibration width of the vibration blade is 2.0 to 30 mm, preferably 5.0 to 10 mm.

  The vibrating blade plate can be attached to the vibrating rod in one or more stages. When the vibration blade plate is multistage, it is preferable that the number of vibration blades is 5 to 7 depending on the size of the vibration motor. This is because if the number of stages is increased too much, the vibration width decreases and the vibration motor generates heat when the load of the vibration motor is increased. In this case, as shown in FIGS. 2 and 3, a spacer 30 may be provided between the plurality of vibrating blade plates 7. The mounting angle of the vibrating blade plate may be horizontal to the vibrating rod, but as shown in FIG. 6A, the inclination angle α is 5 to 30 degrees, in particular, 10 to 20 degrees, and the directionality to vibration. It is good to have it. In particular, in the present invention, it is preferable to have a downward slope. This is because the flow of the waste liquid can be further promoted.

  The vibrating blade plate can be fixed to the vibrating rod by being sandwiched from above and below by the vibrating blade fixing member. When the vibrating blade plate is made of a metal such as stainless steel, a chemical-resistant synthetic resin sheet represented by a fluorine resin such as polytetrafluoroethylene is provided between the vibrating blade plate and the fixing member for the vibrating blade plate. It is preferable to interpose. This is because the life of the vibrating blade plate can be significantly extended. The thickness of the chemical-resistant synthetic resin sheet is not particularly limited, but usually about 1.0 to 3.0 mm is sufficient. Further, as shown in FIG. 6A, when the vibration blade fixing member 10 and the vibration blade 9 are integrally inclined and / or curved as viewed from the side of the vibration shaft, the vibration stress is dispersed. It becomes easy to prevent the vibration blades from being damaged when the vibration frequency becomes high.

  Further, as shown in FIG. 6C, the vibration blade plate 7 may be formed integrally with the vibration blade plate fixing member using a material such as plastic. In this case, as in the case where the two are manufactured separately, the workpieces do not enter or adhere to the joining portion, so that cleaning becomes easy. Further, as shown in FIG. 6C, by integrating the vibration blade plate 7 with the vibration blade plate fixing member, there is no thickness difference between them, and stress concentration can be avoided. It is possible to prevent the vibration blade plate from being damaged.

  When tilting and / or bending is given to the vibrating blade plate, among the large number of vibrating blade plates, the lower one or two sheets are set to be inclined downward and / or curved, and the other blades are inclined and curved upward. It is good. Thus, by changing the direction of inclination and / or curvature according to the position, the bottom of the electrolytic treatment tank is sufficiently stirred, and it is possible to prevent the bottom from being accumulated.

  The degree of the “bending phenomenon” of the vibrating blade plate that occurs with the vibration transmitted from the vibration motor through the vibrating rod is determined by the frequency at which the vibration is applied, the length and thickness of the vibrating blade plate, and the viscosity of the waste liquid to be treated. It changes with specific gravity. For this reason, it is preferable to set the vibration blade plate to a length and a thickness at which the “bending” is most obtained according to the frequency.

  When the length of the vibrating blade plate is changed while keeping the frequency and the thickness of the vibrating blade plate constant, as shown in FIG. 7, as the length of the portion ahead of the vibrating blade plate fixing member increases, a certain stage Until then, the degree of “bending” becomes large, but after that, “bending” becomes small, and when it becomes a certain length, it becomes irrelevant. And, it became clear that the relationship of “bending” becoming larger again at a certain length was repeated.

  Therefore, the length of the vibrating blade plate (the length of the portion ahead of the vibrating blade plate fixing member) is preferably the length indicating the first peak shown in FIG. 7 or the second peak. It is preferable to select the length indicating the first peak or the length indicating the second peak. The length of the second peak is preferably selected by giving a strong vibration to the waste liquid to be treated or flowing. Can be selected as appropriate depending on whether or not the When the length indicating the third peak is selected, the vibration width becomes small.

  The following table shows the results of determining the length of the first peak and the length of the second peak by changing the thickness of the SUS304 vibrating blade at a frequency of 37-60 Hz and 75 W. The length of the vibration blade plate in this experiment is the length from the front end of the vibration blade plate fixing member to the front end of the vibration blade plate (the length indicated by m in A in FIG. 6). The length from the center of the vibrating rod to the tip of the fixed member for the vibrating blade plate (the length indicated by n in FIG. 6A) is 27 mm, and the inclined angle α of the vibrating blade plate is 15 degrees upward.

  Moreover, in this invention, in addition to the vibration stirring mentioned above, you may use aeration stirring together as needed. In this case, it is conceivable to install a diffuser tube at the bottom of the electrolytic treatment tank, but in this case, care must be taken not to form an explosion. In this case, the vibration motor is preferably an explosion-proof type. Furthermore, when treating the waste liquid that generates toxic gas by electrolytic treatment, it is preferable to provide an exhaust hood above the electrolytic treatment tank.

  The selection of the anode electrode used for the electrolytic treatment of the waste liquid is extremely important in oxidizing hypophosphorous acid and phosphorous acid. The electrode for the anode is not limited as long as it has conductivity and corrosion resistance and has sufficient oxidizing power to convert hypophosphorous acid and phosphorous acid into phosphoric acid, but a lead dioxide electrode is used. It is preferable. This is because the lead dioxide electrode is superior in oxidizing power compared to other electrodes. The raw material of the electrode base of the lead dioxide electrode and the lead dioxide layer is not particularly limited, for example, directly on titanium, niobium, zirconium, iron or alloys thereof, or oxides such as titanium, niobium, zirconium, platinum, palladium After forming an intermediate layer containing a noble metal such as lead acid, a lead dioxide layer may be formed using lead nitrate, basic lead carbonate, lead oxide or the like. Of these, a titanium-coated layer of α-type lead peroxide and β-type lead dioxide is particularly preferable.

  The material for the cathode electrode is not particularly limited, and a material having conductivity and corrosion resistance, such as titanium, zirconium, niobium, tungsten, copper, nickel, iron, or an alloy thereof can be used. However, it is particularly preferable to use a SUS304 stainless steel electrode.

  The shape of both the anode electrode and the cathode electrode is not particularly limited. For example, the anode electrode and the cathode electrode may be formed in a flat plate shape, or in a mesh or a porous plate shape in order to increase the contact area with the treated water. It may be formed.

Further, the magnesium compound may be added to the waste liquid and the electrolytic treatment may be performed in the presence of ammonium ions. According to this, phosphoric acid obtained by electrolytic treatment can be insolubilized as magnesium ammonium phosphate and removed / recovered. This is particularly effective for a waste liquid having a high phosphoric acid concentration. The magnesium compound added to the waste liquid is not particularly limited as long as it releases calcium ions in the waste liquid. For example, a magnesium salt of an inorganic acid such as magnesium chloride (MgCl ₂ ) or magnesium sulfide (MgSO ₄ ) is used. It is possible. The magnesium compound may be added as a powder or a solution. The addition of the magnesium compound to the waste liquid may be performed at a timing capable of reacting with phosphoric acid obtained by the electrolytic treatment, and may be performed either before or after the electrolytic treatment or during the electrolytic treatment. The amount of magnesium compound added may be any amount that releases an equivalent molar amount of magnesium ions to the concentration of phosphorus contained in the waste liquid, but in order to efficiently remove and recover phosphoric acid, it is added in a small excess. It is preferable.

Here, in order to produce a magnesium ammonium phosphate crystal, the presence of ammonium ions is essential. Ammonium ions can be added together with a magnesium compound as an ammonium salt such as ammonium chloride (NH ₄ Cl). For example, when treating a waste solution containing ammonium ions, such as an electroless plating waste solution. The reaction can also be carried out using this ammonium ion. Since ammonium ion is a substance that also causes water pollution, it is very effective in terms of environmental hygiene to remove it from the electroless plating waste liquid together with phosphoric acid. In addition, even when treating a waste solution containing ammonium ions such as an electroless plating waste solution, it is possible to compensate for this by adding an ammonium salt if a sufficient amount of ammonium ions is not contained in the reaction. It is. The ammonium salt may be added to the waste liquid at a timing at which it can react with the phosphoric acid obtained by the electrolytic treatment, and may be added either before or after the electrolytic treatment or during the electrolytic treatment.

  Further, a calcium compound may be added to the waste liquid to insolubilize and remove phosphoric acid as calcium phosphate. The calcium compound added to the waste liquid is not particularly limited as long as it releases calcium ions in the waste liquid. For example, calcium hydroxide can be used, and may be added as a powder or added as a solution. May be. Further, the calcium compound may be added to the waste liquid at a timing capable of reacting with phosphoric acid obtained by the electrolytic treatment, and may be added either before or after the electrolytic treatment or during the electrolytic treatment. The amount of calcium compound added may be any amount that releases calcium ions in an equimolar amount with the concentration of phosphoric acid contained in the waste liquid, but in order to efficiently remove and recover phosphoric acid, it should be added in a small excess. It is preferable to do.

Moreover, when the waste liquid to process contains heavy metal ions, such as nickel, cobalt, copper, tin, silver, platinum, and these alloys, it is good to sulphide and insolubilize these. Thereby, since it can coagulate and precipitate as heavy metal sulfide, removal of heavy metal ions becomes easy. The sulfurization treatment may be performed before the electrolytic treatment or after the electrolytic treatment. For the sulfidation treatment, a known sulfidation treatment agent such as water soda (NaSH) or sodium sulfide (Na ₂ S) can be used. The agglomerated and precipitated heavy metal sulfide may be removed alone, but in particular, it is preferably removed after coprecipitation with magnesium ammonium phosphate crystals. Magnesium ammonium phosphate crystals are present as very fine particles of several μm, so it is difficult to remove and collect them alone. However, coprecipitation with heavy metal sulfides increases aggregation and facilitates removal and recovery. Because it becomes.

  Separation means for removing and recovering magnesium ammonium phosphate crystals, calcium phosphate crystals, and heavy metal sulfides produced by the above means is not particularly limited, and known means such as filtration and centrifugation are used. Can be used. However, since the magnesium ammonium phosphate crystal is present in extremely fine particles as described above, it may be separated by a precise separation means such as membrane separation or by coprecipitation with heavy metal sulfide.

  Examples of the present invention will be described below.

(1) Treatment liquid A solution prepared by adding 1100 ml of a 32% aqueous sodium hydroxide solution to 13 liters of nickel plating waste liquid to adjust the pH to 9.0 was used. The phosphorus concentration in the treatment solution before the electrolytic treatment was 12000 mg / l.

(2) Electrolytic treatment tank and electrode As the electrolytic treatment tank, the one shown in FIGS. 3 and 8 was used. The electrolytic treatment tank 5 is made of FRP having a size of W 200 mm × L 300 mm × H 290 mm and a capacity of 14 liters. And in this electrolytic treatment tank 5, the electrode 21 was arrange | positioned as shown in FIG. For the anode electrode, a perforated plate (W100 mm × H285 mm) in which an α-type lead peroxide layer is coated on a titanium plate and then a β-type lead dioxide layer is coated to make the total lead oxide layer 0.5 to 1 mm. × 3 mm) 2 sheets were used. As the cathode electrode, three SUS304 hunted parts (W100 mm × H285 mm × 3 mm) were used.

(3) Vibratory stirrer A vibration stirrer having the configuration shown in FIG. As shown in FIG. 3, the vibration stirrer 22 is composed of one vibrating rod 6 and six vibrating blade plates 7 made of SUS304 and having a thickness of 0.5 mm inclined downward by 15 degrees from the right angle direction of the vibrating rod 6. Attached. This vibration stirrer 22 was arranged in the electrolytic treatment tank 5 as shown in FIG. And the vibration rod 6 was driven by the vibration motor 1 with an inverter (75 W × 200 V, three phases).

(4) Operation With the distance between the electrodes kept at 50 mm, 14 liters of the above-mentioned treatment solution was put into the electrolytic treatment tank, and an electrolytic treatment was carried out by passing a current of 4.5 to 5.5 V, 96 A through the electrodes. On the other hand, a vibration of 43 Hz was generated in the vibration stirrer, and the treatment liquid in the electrolytic treatment tank was vibrated and stirred. The treatment liquid was heated to 20 to 40 ° C. at the beginning of the operation, and was set to around 70 ° C. as the electrolytic oxidation progressed. The treatment solution was sampled 1 hour, 2 hours, 4 hours, 6 hours and 8 hours after the start of the electrolytic oxidation treatment. After neutralizing this sampling solution, a calcium hydroxide solution was added and filtered, and the concentration of phosphorus contained in the obtained filtrate was measured.

Comparative Example 1

  The electrolytic treatment was performed in the same manner as in Example 1 using a propeller stirrer instead of the vibration stirrer in Example 1.

  Table 3 shows the results of the electrolytic treatment of the treatment liquid in Example 1, and Table 4 shows the results of the electrolytic treatment in Comparative Example 1. First, as shown in Table 3, in Example 1 using a vibration stirrer, approximately 97% of phosphorus in the treatment liquid was removed in 2 hours from the start of the electrolytic treatment. On the other hand, as shown in Table 4, in Comparative Example 1 using a propeller stirrer, only 65% of phosphorus was removed after 2 hours from the start of the electrolytic treatment, and 8 hours passed. Even after this, 90% was obtained, which was less than the phosphorus removal rate in Example 1. From this, it became clear that it is extremely effective to perform vibration stirring in the electrolytic oxidation treatment of hypophosphorous acid and / or phosphorous acid in the waste liquid.

  As in Example 1, 1100 ml of 32% sodium hydroxide solution was added to 13 liters of nickel plating waste liquid to adjust the pH to 9.0. The phosphorus concentration in the treatment solution before the electrolytic oxidation treatment was 15000 mg / l. Using this treatment solution, electrolytic treatment was performed in the same manner as in Example 1.

Comparative Example 2

  The electrolytic oxidation treatment was performed in the same manner as in Example 1 except that the anode electrode in Example 1 was changed from the lead dioxide electrode to the Ir—Sn electrode.

  Table 5 shows the results of the electrolytic treatment of the treatment liquid in Example 2, and Table 6 shows the results of the electrolytic treatment in Comparative Example 2. First, as shown in Table 5, in Example 2 in which a lead dioxide electrode was used as the anode, approximately 96% of phosphorus in the treatment liquid was removed in 2 hours from the start of the electrolytic oxidation treatment. On the other hand, as shown in Table 6, in Comparative Example 2 using the Ir—Sn electrode as the anode, only about 86% of phosphorus was removed after 2 hours from the start of the electrolytic treatment, After 8 hours, 97% of phosphorus was finally removed. For this reason, in the electrolytic treatment of hypophosphorous acid and / or phosphorous acid in the treatment liquid, the use of a lead dioxide electrode as the anode is extremely effective in improving the oxidation rate of hypophosphorous acid and / or phosphorous acid. It became clear that it was effective.

  After electrolytic treatment of the treatment liquid, an optimum pH for a method of adding a magnesium compound to the treatment liquid and removing phosphorus produced by oxidizing phosphorous acid and / or phosphorous acid as magnesium ammonium phosphate crystals The conditions were examined.

Nickel plating waste liquid was used as the treatment liquid, and the same electrolytic treatment tank, vibration stirrer, anode electrode, and cathode electrode as in Example 1 were used, and the electrolytic treatment was performed in the same manner as in Example 1. Waste liquid electrolysis was performed. The treatment solution after the electrolytic treatment had a pH of 8.4 and a phosphorus concentration of 8000 mg / l. Further, magnesium sulfate (MgSO ₄ ) powder was used as the magnesium compound, and 10% dilute sulfuric acid and 10% sodium hydroxide solution were used for pH adjustment.

  10% diluted sulfuric acid and / or 10% sodium hydroxide solution was added to a sample obtained by sampling an appropriate amount of the treatment solution after the electrolytic treatment, and the pH was adjusted in the range of 5.0 to 12.0. Magnesium sulfate crystals were produced by adding magnesium sulfate powder in an amount equivalent to phosphorus to each sampling solution adjusted in pH and stirring. And it filtered with the membrane filter with a filtration effective diameter of 0.45 micrometer, the magnesium sulfate ammonium crystal | crystallization was isolate | separated, and each sampling liquid as a filtrate was obtained. The residual phosphorus concentration of each sampling solution was measured, and the phosphorus removal rate was determined from this value.

  Table 7 summarizes the residual phosphorus concentration and phosphorus removal rate of each sampling solution. As shown in Table 6, when the pH was adjusted to 5.0, the phosphorus removal rate was only 2.5%, but when adjusted to pH 6.0, the removal rate was 52.5%. The rate is rising rapidly. At pH 9.0 to 12.0, the removal rate was 98.5 to 99.0%, and phosphorus was almost completely removed. From this, it was revealed that when removing phosphorus in the treatment liquid by adding a magnesium compound, it is suitable to adjust the treatment liquid to pH 9.0 to 12.0.

  As described above, in each example, hypophosphorous acid and / or phosphorous acid contained in the waste liquid can be oxidized into phosphoric acid in a short time and with high efficiency, and the produced phosphoric acid is converted into calcium phosphate crystals or It could be almost completely removed from the waste liquid in the form of magnesium ammonium sulfate crystals. The recovered calcium phosphate crystals and magnesium ammonium sulfate crystals can be effectively used as useful substances such as fertilizers.

  In the conventional waste liquid treatment method, it has been difficult to efficiently remove and recover hypophosphorous acid and phosphorous acid contained in the waste liquid. However, by using the waste liquid treatment method according to the present invention, hypophosphorous acid Acid and phosphorous acid can be efficiently removed and recovered after making phosphoric acid with high utility value. Therefore, it is possible to prevent the eutrophication of the river caused by the waste liquid dumping, and it is possible to effectively use the collected phosphoric acid as a fertilizer.

DESCRIPTION OF SYMBOLS 1 Vibration motor 2 Vibration transmission member 3 Spring 4 Base 5 Electrolytic treatment tank 6 Vibration rod 7 Vibration blade plate 8 Vibration blade plate fixing member 9 Nut 10 Nut 11 Nut 12 Nut 13 Washer ring 14 Screw groove 15 of the vibration rod 15 Rubber ring 21 Electrode 22 Vibration stirrer 30 Spacer 41 Support bar 42 extending downward from the vibration transmitting member side Support bar extending upward from the electrolytic treatment tank side

Claims (7)

A waste liquid containing hypophosphorous acid and / or phosphorous acid and ammonium ions is supplied to an electrolytic treatment tank comprising at least a pair of electrodes composed of an anode electrode and a cathode electrode, and a vibration stirring means, and the waste liquid. Add the magnesium compound to
By performing electrolytic treatment during vibration stirring, hypophosphorous acid and / or phosphorous acid is oxidized to normal phosphoric acid, and at the same time, a magnesium ammonium phosphate crystal is formed from the normal phosphoric acid and the ammonium ion. A waste liquid treatment method characterized by the above. Further, waste processing method according to claim 1, characterized in that it comprises a step of separating the magnesium ammonium phosphate crystals.   The waste liquid treatment method according to claim 1, wherein a calcium compound is added to the waste liquid to form calcium phosphate crystals. The waste liquid treatment method according to claim 3 , further comprising a step of separating the calcium phosphate crystals. The waste liquid treatment method according to any one of claims 1 to 4 , further comprising a step of insolubilizing heavy metal ions contained in the waste liquid by a sulfidation treatment. Anode electrode, wastewater treatment method according to any one of claims 1 to 5, characterized in that the lead dioxide electrode. The waste liquid treatment method according to any one of claims 1 to 6 , wherein the waste liquid to be subjected to the electrolytic treatment is an electroless plating waste liquid.

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