JP2021075764A - Method of suppressing decrease in oxidant concentration of sulphuric acid solution containing persulfuric acid - Google Patents
Method of suppressing decrease in oxidant concentration of sulphuric acid solution containing persulfuric acid Download PDFInfo
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Abstract
Description
本発明は、金属、シリコン、ガラス、プラスチックなど各種材料の表面洗浄や表面改質処理に用いる、酸化剤としての酸化性物質を含む硫酸溶液中の酸化剤濃度の低下を抑制する方法に関する。 The present invention relates to a method for suppressing a decrease in the concentration of an oxidizing agent in a sulfuric acid solution containing an oxidizing substance as an oxidizing agent, which is used for surface cleaning and surface modification treatment of various materials such as metal, silicon, glass and plastic.
ペルオキソ一硫酸、ペルオキソ一硫酸塩、ペルオキソ二硫酸、ペルオキソ二硫酸塩といった過硫酸成分を含む硫酸溶液は、極めて強い酸化性を有する。この強い酸化性を利用して金属、シリコン、ガラス、プラスチックなどの各種材料表面の洗浄や表面改質に利用されている。 A sulfuric acid solution containing a persulfate component such as peroxomonosulfate, peroxomonosulfate, peroxodisulfate, or peroxodisulfate has extremely strong oxidizing properties. Utilizing this strong oxidizing property, it is used for cleaning and surface modification of the surface of various materials such as metal, silicon, glass, and plastic.
例えば、金属材料に対しては、特許文献１に硫酸含有処理液を電解セルに循環流通させて過硫酸を生成させ、酸化還元電位を＋１．５〜＋３．５Ｖとした処理液中でアルミニウム膜を陽極酸化することにより、該アルミニウム膜に細孔を形成する工程を有する多孔質膜の製造方法が記載されている。また、特許文献２には、シリコンウエハなどに付着した汚染物などを剥離効果が高い過硫酸溶液で洗浄剥離する際に、硫酸溶液を繰り返し利用しつつ過硫酸を再生して洗浄に供する硫酸リサイクル型洗浄システムが記載されている。さらに、特許文献３には、プラスチック材料を過硫酸塩が溶解した硫酸濃度５０〜９２重量％で過硫酸濃度３〜２０ｇ／Ｌの溶液で処理し、当該過硫酸塩を溶解した溶液の温度を８０〜１４０℃とするめっきの前処理としてのプラスチック表面処理方法が記載されている。
For example, for a metal material, in
上述したように過硫酸成分を含む硫酸溶液は、各種材料の表面洗浄や表面改質に幅広く利用することが可能であるが、該溶液中に不純物が混入すると短時間に酸化剤濃度が低下し、酸化活性が失われることがある。このような不純物として硝酸イオン、亜硝酸イオンなどの窒素酸化物イオンがある。これらの不純物が存在し酸化剤濃度の低下が顕著な状況で表面処理に必要な該溶液中の酸化剤濃度を維持するためには、過硫酸成分の供給速度を高める必要がある。例えば、硫酸含有液を電解して生成させた過硫酸成分を供給する場合には、電解装置の大型化が必要となる。また、硫酸中に過硫酸塩を添加する方法や、硫酸中に過酸化水素を添加する方法で生成させた過硫酸成分を用いる場合には、硫酸、過硫酸塩、過酸化水素など、必要成分の使用量を増やす必要がある。このように、酸化剤濃度の低下を引き起こす不純物の混入は、過硫酸成分を含む硫酸溶液による表面処理効果の低下を招くだけでなく、処理コストの増大を招く、という問題点がある。 As described above, a sulfuric acid solution containing a persulfuric acid component can be widely used for surface cleaning and surface modification of various materials, but if impurities are mixed in the solution, the oxidant concentration decreases in a short time. , Oxidizing activity may be lost. Such impurities include nitrogen oxide ions such as nitrate ion and nitrite ion. In order to maintain the oxidant concentration in the solution required for surface treatment in a situation where these impurities are present and the oxidant concentration is significantly reduced, it is necessary to increase the supply rate of the persulfate component. For example, in the case of supplying a persulfuric acid component generated by electrolyzing a sulfuric acid-containing liquid, it is necessary to increase the size of the electrolyzer. In addition, when a persulfate component generated by a method of adding persulfate to sulfuric acid or a method of adding hydrogen peroxide to sulfuric acid is used, necessary components such as sulfuric acid, persulfate, and hydrogen peroxide are used. It is necessary to increase the usage of. As described above, the mixing of impurities that causes a decrease in the concentration of the oxidizing agent has a problem that not only the surface treatment effect of the sulfuric acid solution containing the persulfuric acid component is lowered, but also the treatment cost is increased.
一方、窒素酸化物イオンの混入を抑えるために、液補充や硫酸濃度調整に用いる水に、窒素酸化物イオンを含有しない純水を用いることは有効である。しかしながら、該硫酸溶液によって洗浄、表面改質処理される各種材料由来の窒素酸化物イオンを完全に排除することは困難であることから、該物質の適切な方法およびシステムで除去する必要があり実用的でない、という問題点がある。 On the other hand, in order to suppress the contamination of nitrogen oxide ions, it is effective to use pure water containing no nitrogen oxide ions as the water used for liquid replenishment and sulfuric acid concentration adjustment. However, since it is difficult to completely eliminate nitrogen oxide ions derived from various materials that are washed and surface-modified with the sulfuric acid solution, it is necessary to remove the nitrogen oxide ions by an appropriate method and system for the substance, which is practical. There is a problem that it is not the target.
本発明は上記のような課題に鑑みてなされたものであり、酸化剤濃度の低下を引き起こす不純物である窒素酸化物イオンの混入によっても、有効な酸化剤濃度の低下を最小限に抑制することが可能な過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法を提供することを目的とする。 The present invention has been made in view of the above problems, and it is possible to minimize the decrease in the effective oxidant concentration even by mixing nitrogen oxide ions, which are impurities that cause the decrease in the oxidant concentration. It is an object of the present invention to provide a method for suppressing a decrease in the concentration of an oxidizing agent in a sulfuric acid solution containing a persulfuric acid component.
上記目的を達成するために本発明は、酸化剤として過硫酸成分を含み、該酸化剤濃度の低下を促進する不純物として窒素酸化物イオンが存在する硫酸溶液中の酸化剤濃度の低下を抑制する方法であって、前記窒素酸化物イオンを含む硫酸溶液に対して不活性なガスを接触させる、過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法を提供する（発明１）。 In order to achieve the above object, the present invention suppresses a decrease in the oxidant concentration in a sulfuric acid solution containing a persulfuric acid component as an oxidant and nitrogen oxide ions as an impurity that promotes the decrease in the oxidant concentration. The present invention provides a method for suppressing a decrease in the concentration of an oxidizing agent in a sulfuric acid solution containing a persulfuric acid component, in which an inert gas is brought into contact with the sulfuric acid solution containing nitrogen oxide ions (Invention 1).
かかる発明（発明１）によれば、酸化剤濃度の低下を引き起こす窒素酸化物イオンが混入した過硫酸成分を含む硫酸溶液に不活性なガスを接触させることにより、窒素酸化物イオンが硝酸態ガスとなり、系外に放散することで酸化剤濃度の低下を抑制することができる。 According to the present invention (Invention 1), when an inert gas is brought into contact with a sulfuric acid solution containing a persulfuric acid component mixed with nitrogen oxide ions that cause a decrease in the oxidant concentration, the nitrogen oxide ions become nitrate gas. Therefore, the decrease in the oxidant concentration can be suppressed by dissipating it outside the system.
上記発明（発明１）においては、前記過硫酸成分が、ペルオキソ一硫酸、ペルオキソ一硫酸塩、ペルオキソ二硫酸及びペルオキソ二硫酸塩から選択される一種以上であることが好ましい（発明２）。 In the above invention (Invention 1), it is preferable that the persulfate component is one or more selected from peroxomonosulfate, peroxomonosulfate, peroxodisulfate and peroxodisulfate (Invention 2).
かかる発明（発明２）によれば、これらの過硫酸成分は、酸化剤として機能するが、窒素酸化物イオンが存在すると酸化剤濃度の低下を引き起こしやすい、不活性なガスを接触させて窒素酸化物イオンの低下させることにより、これを抑制することができる。 According to the present invention (Invention 2), these persulfate components function as an oxidant, but nitrogen oxide oxidation is carried out by contacting with an inert gas, which tends to cause a decrease in the oxidant concentration in the presence of nitrogen oxide ions. This can be suppressed by reducing the substance ions.
上記発明（発明１，２）においては、前記硫酸溶液に対して不活性なガスを曝気することにより、窒素酸化物イオンを含む該硫酸溶液に対して不活性なガスを接触させることが好ましい（発明３）。
In the above inventions (
かかる発明（発明３）によれば、不活性なガスとの接触手段として、不活性なガスの曝気を採用することにより、曝気流量を増やすほど、かつ液深が大きいほど硝酸態窒素ガスが曝気ガスの気泡内に取り込まれるため、窒素酸化物イオンの除去効率を向上することができる。 According to the invention (Invention 3), the nitrate nitrogen gas is aerated as the aeration flow rate is increased and the liquid depth is increased by adopting the aeration of the inert gas as the means of contact with the inert gas. Since it is taken into the gas bubbles, the efficiency of removing nitrogen oxide ions can be improved.
本発明の過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法によれば、酸化剤濃度の低下を引き起こす窒素酸化物イオンが混入した過硫酸成分を含む硫酸溶液の酸化剤濃度の低下を有効に抑制することができ、酸化剤による各種材料の表面処理の効果を最大限に発揮させることが可能となる。さらに、表面処理に必要な該溶液中の酸化剤濃度が維持されることにより、過硫酸成分の供給速度を必要最小限に抑えることが可能となる。その結果、例えば硫酸含有液を電解して生成させた過硫酸成分を供給する場合には、コンパクトな電解装置での処理が可能となる。また、硫酸中に過硫酸塩を添加する方法や、硫酸中に過酸化水素を添加する方法で生成させた過硫酸成分を用いる場合には、硫酸、過硫酸塩、過酸化水素など、各成分の使用量を抑えることが可能となる。 According to the method for suppressing a decrease in the oxidant concentration in a sulfuric acid solution containing a persulfuric acid component of the present invention, a decrease in the oxidant concentration in a sulfuric acid solution containing a persulfuric acid component mixed with nitrogen oxide ions that causes a decrease in the oxidant concentration. Can be effectively suppressed, and the effect of surface treatment of various materials with an oxidizing agent can be maximized. Further, by maintaining the concentration of the oxidizing agent in the solution required for the surface treatment, the supply rate of the persulfate component can be suppressed to the minimum necessary. As a result, for example, when supplying a persulfuric acid component generated by electrolyzing a sulfuric acid-containing liquid, processing with a compact electrolyzer becomes possible. In addition, when a persulfate component generated by a method of adding persulfate to sulfuric acid or a method of adding hydrogen peroxide to sulfuric acid is used, each component such as sulfuric acid, persulfate, and hydrogen peroxide is used. It is possible to reduce the amount of hydrogen peroxide used.
本発明の過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法について、以下の実施形態に基づき詳細に説明する。 The method for suppressing a decrease in the concentration of an oxidizing agent in a sulfuric acid solution containing a persulfuric acid component of the present invention will be described in detail based on the following embodiments.
［過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法］
（過硫酸成分を含む硫酸溶液）
本実施形態において、過硫酸成分を含む硫酸溶液としては、酸化剤として過硫酸成分を含んでおり、かつ硫酸溶液であれば特に制限はない。前記過硫酸成分としては、ペルオキソ一硫酸、ペルオキソ一硫酸塩、ペルオキソ二硫酸及びペルオキソ二硫酸塩などが挙げられ、これらを適宜選択して単独で使用してもよいし、２種以上を併用してもよい。
[Method of suppressing decrease in oxidizing agent concentration in sulfuric acid solution containing persulfuric acid component]
(Sulfuric acid solution containing persulfuric acid component)
In the present embodiment, the sulfuric acid solution containing the persulfuric acid component is not particularly limited as long as it contains the persulfuric acid component as an oxidizing agent and is a sulfuric acid solution. Examples of the persulfate component include peroxomonosulfate, peroxomonosulfate, peroxodisulfate, and peroxodisulfate, which may be appropriately selected and used alone, or two or more thereof may be used in combination. You may.
この過硫酸成分を含む硫酸溶液としては、例えば、硫酸含有液を電解して過硫酸成分を生成した硫酸溶液（電解硫酸溶液）、硫酸中に過酸化水素を添加することで過硫酸成分を生成した溶液などを用いることができ、特に電解硫酸溶液に好適に適用することができる。 Examples of the sulfuric acid solution containing the persulfuric acid component include a sulfuric acid solution (electrolytic sulfuric acid solution) in which a sulfuric acid-containing solution is electrolyzed to generate a persulfuric acid component, and a persulfuric acid component is generated by adding hydrogen peroxide to the sulfuric acid. Can be used, and can be particularly preferably applied to an electrolytic sulfuric acid solution.
この過硫酸成分を含む硫酸溶液としては、例えば電解硫酸溶液の場合、硫酸濃度が６０〜８７重量％、特に７０〜８３重量％であることが好ましい。また、初期状態における酸化剤濃度は利用する用途にもよるが２ｇ／Ｌ以上、特に３〜２０ｇ／Ｌである。酸化剤濃度が２ｇ／Ｌ未満では、酸化剤濃度の低下による影響がそれほど大きくない一方、２０ｇ／Ｌを超えるものは、その製造自体困難で経済的でないうえに酸化剤濃度が多少低下しても酸化能に大きな支障がない。 As the sulfuric acid solution containing the persulfuric acid component, for example, in the case of an electrolytic sulfuric acid solution, the sulfuric acid concentration is preferably 60 to 87% by weight, particularly 70 to 83% by weight. The concentration of the oxidizing agent in the initial state is 2 g / L or more, particularly 3 to 20 g / L, although it depends on the intended use. If the oxidant concentration is less than 2 g / L, the effect of the decrease in the oxidant concentration is not so large, while if the oxidant concentration exceeds 20 g / L, the production itself is difficult and uneconomical, and even if the oxidant concentration is slightly decreased. There is no major problem with oxidizing ability.
（酸化剤濃度低下を促進する不純物）
本実施形態において、上述したような過硫酸成分を含む硫酸溶液に混在する酸化剤濃度の低下を促進する不純物は、窒素酸化物イオンである。この窒素酸化物イオンとしては、硝酸イオン（ＮＯ３−）、亜硝酸イオン（ＮＯ２−）などが挙げられる。これらの窒素酸化物イオンは、硝酸、亜硝酸、及びこれらの塩に起因するのが一般的であるが、窒素酸化物イオンをもたらすものであればこれに限定されない。
(Impurities that promote a decrease in oxidant concentration)
In the present embodiment, the impurity that promotes the decrease in the concentration of the oxidizing agent mixed in the sulfuric acid solution containing the persulfuric acid component as described above is nitrogen oxide ions. Examples of the nitrogen oxide ion include nitrate ion (NO 3- ) and nitrite ion (NO 2- ). These nitrogen oxide ions are generally derived from nitric acid, nitrite, and salts thereof, but are not limited to those that provide nitrogen oxide ions.
過硫酸成分を含む硫酸溶液中の窒素酸化物イオンの濃度は１００ｍｇ／Ｌ（ＮＯ３換算）以下程度、特に０．１〜５０ｍｇ／Ｌ程度である。窒素酸化物イオンの不純物濃度が１００ｍｇ／Ｌを超えると、窒素酸化物イオンが多すぎて、十分に除去しきれず酸化剤濃度の低下の抑制効果が十分に発揮されない。なお、窒素酸化物イオンの下限については特に制限はないが、０．１ｍｇ／Ｌ未満では酸化剤濃度の低下が大きくなく、その効果の確認が困難であるため好ましくない。 The concentration of nitrogen oxide ions in a sulfuric acid solution containing a persulfuric acid component is about 100 mg / L (NO 3 conversion) or less, particularly about 0.1 to 50 mg / L. If the impurity concentration of the nitrogen oxide ion exceeds 100 mg / L, the nitrogen oxide ion is too much to be sufficiently removed, and the effect of suppressing the decrease in the oxidant concentration is not sufficiently exhibited. The lower limit of the nitrogen oxide ion is not particularly limited, but if it is less than 0.1 mg / L, the decrease in the oxidant concentration is not large and it is difficult to confirm the effect, which is not preferable.
（酸化剤濃度の低下抑制手段）
本実施形態においては、窒素酸化物イオンによる過硫酸成分を含む硫酸溶液中の酸化剤の濃度低下を抑制するために、該過硫酸成分を含む硫酸溶液に対して、不活性なガスで曝気する。ここで、不活性なガスとしては、過硫酸成分を含む硫酸溶液と反応しないガスであれば制限はないが、安全性や製造コストの観点から空気や窒素ガス（Ｎ２）が好ましい。
(Means for suppressing the decrease in oxidizing agent concentration)
In the present embodiment, in order to suppress a decrease in the concentration of the oxidizing agent in the sulfuric acid solution containing the persulfuric acid component due to nitrogen oxide ions, the sulfuric acid solution containing the persulfuric acid component is exposed to an inert gas. .. Here, the inert gas is not limited as long as it does not react with the sulfuric acid solution containing the persulfuric acid component, but air or nitrogen gas (N 2 ) is preferable from the viewpoint of safety and production cost.
この曝気処理の条件としては、例えば、過硫酸成分を含む硫酸溶液の貯槽の底部から、該底部の面積１ｍ２に対して、０．１〜１００ｍ３／ｈｒ程度量の不活性なガスを、貯槽の底部に散在するように配置した散気菅から吐出すればよい。この曝気処理により、窒素酸化物イオンが不活性なガスと接触することで硝酸態ガスとなり、貯槽から放散することで窒素酸化物イオンが減少するため、酸化剤濃度の低下を抑制することができる。この曝気処理の時間は、窒素酸化物イオンが減少し酸化剤の濃度の低下が十分に抑制するまで継続すればよく、例えば０．５〜１０時間、特に１〜５時間程度曝気すればよい。 As the conditions for this aeration treatment, for example, from the bottom of the storage tank of the sulfuric acid solution containing the persulfuric acid component, an amount of about 0.1 to 100 m 3 / hr of inert gas is applied to an area of 1 m 2 of the bottom. It may be discharged from the aeration pipes arranged so as to be scattered at the bottom of the storage tank. By this aeration treatment, the nitrogen oxide ions come into contact with the inert gas to become a nitrate gas, and the nitrogen oxide ions are reduced by being released from the storage tank, so that the decrease in the oxidant concentration can be suppressed. .. The aeration treatment may be continued until the nitrogen oxide ions are reduced and the decrease in the concentration of the oxidizing agent is sufficiently suppressed, and the aeration may be, for example, 0.5 to 10 hours, particularly about 1 to 5 hours.
上述したような曝気処理は、例えば過硫酸成分を含む硫酸溶液を用いて処理する前に該硫酸溶液の貯槽で所定時間行ってもよいし、過硫酸成分を含む硫酸溶液を用いた処理を行う処理槽に曝気装置を設けて所定時間爆気した後、連続して過硫酸成分を含む硫酸溶液を用いた処理を行ってもよいし、さらには処理槽に曝気装置を設けて曝気処理を行いながら過硫酸成分を含む硫酸溶液を用いた処理を行ってもよい。 The aeration treatment as described above may be performed for a predetermined time in a storage tank of the sulfuric acid solution before the treatment with a sulfuric acid solution containing a persulfuric acid component, or a treatment using a sulfuric acid solution containing a persulfuric acid component is performed. An aeration device may be provided in the treatment tank to explode for a predetermined time, and then treatment using a sulfuric acid solution containing a persulfuric acid component may be continuously performed, or an aeration device may be provided in the treatment tank to perform the aeration treatment. However, the treatment using a sulfuric acid solution containing a persulfuric acid component may be performed.
以上、本発明の過硫酸成分を含む硫酸溶液中の酸化剤濃度の低下抑制方法について説明してきたが、本発明は前記実施例に限定されず種々の変形実施が可能である。例えば、過硫酸成分を含む硫酸溶液は、過硫酸成分と硫酸溶液のみから構成される必要はなく、酸化剤濃度を低下しないものであれば、リン酸などの他の酸や薬液成分を含んでいてもよい。 Although the method for suppressing the decrease in the concentration of the oxidizing agent in the sulfuric acid solution containing the persulfuric acid component of the present invention has been described above, the present invention is not limited to the above-mentioned examples, and various modifications can be carried out. For example, a sulfuric acid solution containing a persulfuric acid component does not need to be composed of only a persulfuric acid component and a sulfuric acid solution, and contains other acids such as phosphoric acid and a chemical solution component as long as it does not reduce the concentration of the oxidizing agent. You may.
以下の実施例及び比較例により、本発明を具体的に説明する。ただし、本発明はこれらの記載により何ら限定されるものではない。 The present invention will be specifically described with reference to the following examples and comparative examples. However, the present invention is not limited to these descriptions.
［実施例１〜４］
過硫酸成分を含む硫酸溶液の酸化剤濃度低下抑制効果を以下の手順で評価した。すなわち、７８重量％の硫酸（Ｈ２ＳＯ４）に窒素酸化物イオンをもたらす成分として、ＨＮＯ３またはＮａ２ＮＯ２を表１に示す濃度になるように添加したものを試験液とした。この試験液１Ｌを６０℃に加温して、事前に所定時間、貯槽の下方から１０Ｌ／分の流量で空気曝気を行った。この試験条件を表１に示す。
[Examples 1 to 4]
The effect of suppressing the decrease in the oxidant concentration of the sulfuric acid solution containing the persulfuric acid component was evaluated by the following procedure. That is, a test solution was prepared by adding HNO 3 or Na 2 NO 2 to 78% by weight of sulfuric acid (H 2 SO 4 ) so as to bring nitrogen oxide ions to the concentration shown in Table 1. 1 L of this test solution was heated to 60 ° C., and air aeration was performed in advance for a predetermined time at a flow rate of 10 L / min from below the storage tank. The test conditions are shown in Table 1.
その後、試験液を電解して酸化剤濃度が７〜８ ｇ／Ｌ ａｓ Ｓ２Ｏ８となるよう調整し、空気曝気後の試験液にＮａ２Ｓ２Ｏ８試薬を添加して酸化剤濃度の変化を３時間測定した。結果を図１に示す。なお、酸化剤濃度は、ヨウ素滴定法により測定した。このヨウ素滴定法とは、少量分取した試験液にＫＩを加えてＩ２を遊離させ、そのＩ２をＮａ２Ｓ２Ｏ８標準溶液で滴定してＩ２の量を求め、そのＩ２の量から酸化剤濃度を求める方法である。 Then, the test solution is electrolyzed to adjust the oxidant concentration to 7 to 8 g / Las S 2 O 8, and the Na 2 S 2 O 8 reagent is added to the test solution after air aeration to adjust the oxidant concentration. The change in was measured for 3 hours. The results are shown in FIG. The oxidant concentration was measured by the iodine titration method. And the iodine titration method, to release the I 2 by adding KI to the test liquid taken minor component, determine the amount of I 2 and the I 2 and titrated with Na 2 S 2 O 8 standard solution, the I 2 This is a method of obtaining the oxidizing agent concentration from the amount of iodine.
［比較例１〜３及び参考例］
実施例と同様にＨＮＯ３またはＮａ２ＮＯ２を表２に示す濃度になるように添加した試験液に対して、空気曝気を行わずスターラー撹拌を所定時間実施後、試験液を電解して酸化剤濃度が７〜８ ｇ／Ｌ ａｓ Ｓ２Ｏ８となるよう調整し、攪拌後の試験液にＮａ２Ｓ２Ｏ８試薬を添加して酸化剤濃度の変化を３時間測定した。結果を図２に示す。また、７８重量％の硫酸（Ｈ２ＳＯ４）に対して、酸化剤濃度が７〜８ ｇ／Ｌ ａｓ Ｓ２Ｏ８となるよう調整し窒素酸化物成分を添加しないで、Ｎａ２Ｓ２Ｏ８試薬を添加して酸化剤濃度の変化を３時間測定した（参考例）。試験条件を表２に結果を図２にあわせて示す。
[Comparative Examples 1 to 3 and Reference Example]
Similar to the examples, the test solution to which HNO 3 or Na 2 NO 2 was added to the concentration shown in Table 2 was stirred with a stirrer for a predetermined time without air aeration, and then the test solution was electrolyzed and oxidized. The agent concentration was adjusted to 7 to 8 g / Las S 2 O 8, and the Na 2 S 2 O 8 reagent was added to the test solution after stirring, and the change in the oxidant concentration was measured for 3 hours. The results are shown in FIG. Further, the concentration of the oxidizing agent was adjusted to 7 to 8 g / Las S 2 O 8 with respect to 78% by weight of sulfuric acid (H 2 SO 4 ), and Na 2 S 2 was not added without adding the nitrogen oxide component. the O 8 reagent was added to measure 3 hours the change in oxidant concentration (reference example). The test conditions are shown in Table 2 and the results are shown in FIG.
表１、２及び図１、２から明らかなように、窒素酸化物イオンが存在する硫酸溶液に対して不活性なガスである空気で曝気した実施例１〜４では、酸化剤の分解を抑制することができ、この効果は曝気時間が長いほど有効であることがわかる。これに対し、曝気処理ではなく撹拌処理した比較例１〜３では窒素酸化物イオンの存在による酸化剤の分解をほとんど抑制できていないことが確認できた。また、参考例の結果より、窒素酸化物イオンの存在がなければ、酸化剤濃度はほとんど低下せず、安定して存在できることがわかる。 As is clear from Tables 1 and 2 and FIGS. 1 and 2, in Examples 1 to 4 aerated with air, which is a gas inert to the sulfuric acid solution in which nitrogen oxide ions are present, decomposition of the oxidizing agent is suppressed. It can be seen that this effect is more effective as the aeration time is longer. On the other hand, it was confirmed that in Comparative Examples 1 to 3 in which the stirring treatment was performed instead of the aeration treatment, the decomposition of the oxidizing agent due to the presence of nitrogen oxide ions could hardly be suppressed. In addition, from the results of the reference example, it can be seen that if the nitrogen oxide ion is not present, the oxidant concentration hardly decreases and can be stably present.
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| JPS63153825A (en) * | 1986-10-06 | 1988-06-27 | アシンズ コーポレイション | Method and apparatus for continuous recycling of extra-pure liquid for washing semiconductor wafer |
| JPH0790628A (en) * | 1993-09-24 | 1995-04-04 | Toray Ind Inc | Etching device and etching method for thin film |
| JPH0964005A (en) * | 1995-08-17 | 1997-03-07 | Risotetsuku Japan Kk | Method for controlling chemical concentration in piranha cleaning step |
| JPH1136089A (en) * | 1997-07-17 | 1999-02-09 | Kurita Water Ind Ltd | Pickling solution for stainless steel |
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