JPS6051395B2 - How to regenerate cation exchange membranes - Google Patents

Description

【発明の詳細な説明】 本発明は、陽イオン交換膜を用いた塩化アルカリ水溶液
の電解において、不純物によつて汚染された陽イオン交
換膜を再生する方法に係り、比較的簡単な手段で該イオ
ン交換膜の再生をはかり、膜の寿命延長による経済的効
用を増大せんとするものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a cation exchange membrane contaminated with impurities in the electrolysis of an aqueous alkali chloride solution using a cation exchange membrane. The aim is to regenerate ion exchange membranes and increase the economic utility by extending the life of the membranes.

陽イオン交換膜を用いて塩化アルカリ水溶液電解を実施
する場合、塩化アルカリ水溶液中の不純物が陽イオン交
換膜に極めて大きな影響を与えることは知られており、
従来行なわれていたアスベスト隔膜法や水銀法に比べて
可成り厳密な塩水精製法を必要とする。When performing alkali chloride aqueous electrolysis using a cation exchange membrane, it is known that impurities in the alkali chloride aqueous solution have a very large effect on the cation exchange membrane.
It requires a much more rigorous saltwater purification method than the asbestos diaphragm method and mercury method that have been used in the past.

このような塩水精製法の一つとして通常の精製工程に更
にキレート樹脂による精製を付加してＭｇ、Ｃａ、Ｆｅ
分を除去することが提案されている。As one of such salt water purification methods, purification using a chelate resin is added to the normal purification process to purify Mg, Ca, and Fe.
It is proposed to remove the

かゝる方法を採用することにより膜の寿命は延長される
が、キレート樹脂の破過による不純塩水の流入、或はキ
レート樹脂層以降の装置材質より溶出した溶出物などに
よる急激な、或は継続的な不純物の流入に対しては如何
ともし難い点がある。一方、陽イオン交換膜に対する不
純物の影響を緩和する方法として、膜表面て不純物と反
応してｐＨの変化によりゾル又はゲルを形成するような
化合物（例えばリン酸又はその塩）を添加して膜の洗浄
により不純物の離脱を容易とする方法も提案されている
。By adopting such a method, the life of the membrane can be extended, but it may cause rapid or It is difficult to do anything about the continuous inflow of impurities. On the other hand, as a method to alleviate the influence of impurities on cation exchange membranes, a compound (for example, phosphoric acid or its salt) that reacts with impurities on the membrane surface to form a sol or gel due to a change in pH is added to the membrane. A method has also been proposed in which impurities are easily removed by washing.

この方法も膜の寿命延長には確かに有効で、こ・の方法
を使用しない場合に比べて比較的長期の運転が可能であ
るが、なお経済性に立脚した膜寿命を満たし得るもので
はない。This method is certainly effective in extending the lifespan of the membrane, and it is possible to operate the membrane for a relatively long time compared to when this method is not used, but it is still not able to satisfy the membrane lifespan based on economic efficiency. .

かくてこれらの方法と共に一旦劣化した膜を何らかの方
法で再生してその若返りをはかることも考えられ、不純
物による劣化の程度が低い場合には、常温で酸性水溶液
中に膜を浸漬しておくことも行なわれている。Therefore, in addition to these methods, it is also possible to regenerate the once deteriorated membrane in some way to rejuvenate it.If the degree of deterioration due to impurities is low, it is possible to immerse the membrane in an acidic aqueous solution at room temperature. is also being carried out.

しかし乍らこの若返り方法は繰返し実施して有効なもの
ではなく、又劣化がある程度進んだものに対しては最早
や回復は望み得ず、結局のところ効果的な若返り方法と
云えるものではなかつた。However, this rejuvenation method is not effective when repeated, and recovery can no longer be expected for those whose deterioration has progressed to a certain extent, so in the end it cannot be called an effective rejuvenation method. Ta.

本発明者等はかかる実情において汚染された陽イオン交
換膜を有効に再生する方法を検討し、下記骨子の本発明
を完成するに至つた。即ち、本発明は陽イオン交換膜法
塩化アルカリ水溶液電解によつて汚染された陽イオン交
換膜を再生するに当り、陰陽両極室の極液を共に酸性に
維持した電解槽内に該汚染陽イオン交換膜を取付けて通
電することを特徴とする陽イオン交換膜の再生方法であ
る。Under these circumstances, the present inventors have investigated a method for effectively regenerating a contaminated cation exchange membrane, and have completed the present invention as outlined below. That is, in regenerating a cation exchange membrane contaminated by aqueous alkali chloride electrolysis using the cation exchange membrane method, the contaminated cations are placed in an electrolytic cell in which both the cathode and cathode electrolytes are kept acidic. This is a method for regenerating a cation exchange membrane, which is characterized by attaching the exchange membrane and applying electricity.

陽イオン交換膜法による塩化アルカリ水溶液電解の様に
通常陰極室で水酸化アルカリを生成するような電解にお
いては、陰陽両極室を形成するための陽イオン交換膜の
膜中は勿論、陽極室側の膜面迄がアルカリ性となつてい
る。In electrolysis that normally generates alkali hydroxide in the cathode chamber, such as alkali chloride aqueous solution electrolysis using the cation exchange membrane method, not only the inside of the cation exchange membrane to form the anode and cathode chambers but also the anode chamber side. Even the surface of the membrane is alkaline.

一方、陽極室側に供給される塩水は一般には酸性液とし
て供給され、その中の不純物はイオン状態で可溶性とな
つているが、これがアルカリ性を呈している膜の部分で
主として水酸化物等を形成し、水酸化物の溶解度などの
違いにより膜面や膜中に沈着物を作り、これが電解操業
に悪影響を及ぼすものとされ、この場合、主としてＭｇ
は膜面で、Ｆｅは大部分が膜面で一部は膜中で、又Ｃａ
は大部分膜中で沈着するが、但し塩水中の不純物が非常
に多い時はこれらの大部分は膜面に付着するとされてい
る。On the other hand, the salt water supplied to the anode chamber side is generally supplied as an acidic solution, and the impurities in it are soluble in the ionic state, but this is the alkaline part of the membrane that mainly contains hydroxides, etc. Mg is formed and deposits are formed on the membrane surface or inside the membrane due to differences in the solubility of hydroxide, which has a negative impact on electrolytic operation.
is on the film surface, Fe is mostly on the film surface and some in the film, and Ca
Most of the impurities are deposited in the membrane, but when there are a lot of impurities in the salt water, most of them are said to adhere to the membrane surface.

そしてこのような汚染された交換膜はこれを酸性液中に
入れると膜内が酸性となつて沈着物は再び可溶性になり
、拡散によつて膜外へ移動し、膜の清浄化が達成される
のであるが、本発明者等の経験によればか）る酸性液中
（ＨＣｌ中）に膜を浸漬して再生を繰返すと電解操業中
に電圧の上昇が早くなり（これは一定の上限電圧に達す
る運転期間が短くなる）、電流効率が低下し、又生成水
酸化アルカリ中の塩分が増加してくると云つた種々の障
害が認められた。When such a contaminated exchange membrane is placed in an acidic solution, the inside of the membrane becomes acidic and the deposits become soluble again and move out of the membrane by diffusion, achieving cleaning of the membrane. However, according to the experience of the present inventors, if the membrane is immersed in an acidic solution (HCl) and regeneration is repeated, the voltage rises quickly during electrolysis operation (this is due to a certain upper limit voltage). Various problems were observed, such as a reduction in the operating period required to reach 100%, a decrease in current efficiency, and an increase in salt content in the alkali hydroxide produced.

そしてこれらの事実より単なる酸性液中での浸漬による
再生方法では膜中の不純物が充分に除去し難いことを知
つたのである。From these facts, they learned that it is difficult to remove impurities in the membrane sufficiently by a regeneration method that simply involves immersing the membrane in an acidic solution.

そこて本発明者等は上記の様な知見を基にして電解運転
によつて汚染された膜を電解槽より取外し、陽極室およ
び陰極室の極液を共に酸性に保つた電解槽に取付けて通
電したところ、膜中や膜表面の不純物を除去することが
出来、これによつて再生した膜は可成り長期間の運転に
も耐えることが出来るのみならず、この再生を適宜繰返
した場合にも既述の如き電圧上昇や電流効率の低下など
の障害が軽減して膜の延命が達成出来ることを見出した
のである。Therefore, based on the above knowledge, the present inventors removed the membrane contaminated by electrolytic operation from the electrolytic cell, and installed it in an electrolytic cell in which both the anode chamber and the cathode chamber's electrolytes were kept acidic. When electricity is applied, impurities in the membrane and on the membrane surface can be removed, and the regenerated membrane can not only withstand fairly long-term operation, but also when this regeneration is repeated appropriately. It was also discovered that the above-mentioned problems such as voltage increase and decrease in current efficiency can be alleviated, and the life of the membrane can be extended.

膜の若返りの為の電解槽を使用する本発明の再生方法で
は膜中が酸性となるばかりでなく膜を通してＨ＋が主に
陰極に向けて流れ、又膜中で可溶性となつた不純物も強
制的に陰極に向かつて流れて不純物の充分な除去が出来
るためと思われる。In the regeneration method of the present invention using an electrolytic cell for membrane rejuvenation, not only does the membrane become acidic, but also H+ flows through the membrane mainly toward the cathode, and impurities that have become soluble in the membrane are forcibly removed. This seems to be because the impurities can be sufficiently removed by flowing towards the cathode.

本発明方法に適用出来る陽イオン交換膜としては、塩化
アルカリ水溶液電解用の陽イオン交換膜としてられてい
るＮａｆｉＯｎ膜（ＤｕＰＯｎｔ社製）及びその改質膜
などの含フッ素系の膜やスチレンージビニルベンゼン共
重合体をベースとして製造された膜などに適用してよく
、いずれにしても適度の耐酸性を有する陽イオン交換膜
であればよい。本発明を実施するに当つて使用される再
生の為の電解槽としては、陰陽両極室および陰陽両極が
耐酸性材料で作られたものであり、かかる耐酸性材料の
好適な組合せとして陰陽両極が共にカーボン製の電極で
あり、少くとも陰陽両極室の内壁が塩化ビニル樹脂など
の耐酸性合成樹脂であることが好ましく、これら両極室
の中間に汚染された膜を取付けける構造とすることがよ
い。この電解槽において陰陽両極室に供給する酸性液と
しては、塩酸、硫酸等の鉱酸及びこれら鉱酸を加えた塩
化アルカリ液ならびに酢酸、プロピオン酸、グリコール
酸などの有機酸を挙げることが出来るが、特に塩酸が最
も好ましい。Examples of cation exchange membranes that can be applied to the method of the present invention include fluorine-containing membranes such as the NafiOn membrane (manufactured by DuPOnt), which is used as a cation exchange membrane for aqueous alkali chloride electrolysis, and its modified membrane, and styrene-vinyl membranes. The present invention may be applied to membranes manufactured using a benzene copolymer as a base, and in any case, any cation exchange membrane having appropriate acid resistance may be used. In the electrolytic cell for regeneration used in carrying out the present invention, the negative and positive electrode chambers and the negative and positive electrodes are made of acid-resistant materials, and a suitable combination of such acid-resistant materials is that the negative and positive electrodes are made of acid-resistant materials. Both electrodes are made of carbon, and at least the inner walls of the negative and positive electrode chambers are preferably made of acid-resistant synthetic resin such as vinyl chloride resin, and the structure is preferably such that a contaminated membrane is installed between these electrode chambers. . In this electrolytic cell, the acidic liquid supplied to the negative and positive polarity chambers may include mineral acids such as hydrochloric acid and sulfuric acid, alkaline chloride solutions containing these mineral acids, and organic acids such as acetic acid, propionic acid, and glycolic acid. , especially hydrochloric acid is most preferred.

そしてその濃度は膜の性能が変化しない濃度で使用し、
塩酸の場合は１〜？程度が好適であり、通電による他の
電解運転の条件は特に制限はないが１〜２Ａ／Ｄｄの電
流密度で常温３〜１０時間程度実施すればよい。本発明
方法は上記の通りの簡単な方法で膜寿命の大巾な延長を
はかることが出来るもので、操業上の利益および経済的
効用は極めて大きい。Then, use the concentration at a concentration that does not change the performance of the membrane.
1~ for hydrochloric acid? There are no particular restrictions on the other conditions for electrolytic operation by energization, but it may be carried out at room temperature for about 3 to 10 hours at a current density of 1 to 2 A/Dd. The method of the present invention can significantly extend the membrane life using the simple method described above, and has extremely large operational benefits and economic utility.

以下実施例および比較例を掲げて本発明を説明する。実
施例１ 陽イオン交換膜としてＮａｆｉＯｎ３ｌ３（ＤｕＰＯｎ
ｔ社製含フッ素陽イオン交換膜）を用い、陽極室はチタ
ンライニング、陽極は酸化ルテニウムを含む材料でコー
ティングされたチタンメッシュ、陰極室はＳＵＳ３Ｏ４
、陰極はＳＵＳ３Ｏ４のメッシュで構成された電解槽に
ＫＣｌブライン３３０〜３００ｇ／ｅを分解率略３５％
となるように供給して電解を行なつた（初回操業運転）
。The present invention will be explained below with reference to Examples and Comparative Examples. Example 1 NafiOn3l3 (DuPOn
The anode chamber is titanium lined, the anode is a titanium mesh coated with a material containing ruthenium oxide, and the cathode chamber is SUS3O4.
, 330-300 g/e of KCl brine was added to an electrolytic cell with a cathode made of SUS3O4 mesh at a decomposition rate of about 35%.
(Initial operation)
.

なお、ブラインはキレート樹脂を用いてＭｇ，Ｃａを除
去したものを使用した。Note that the brine used was one in which Mg and Ca were removed using a chelate resin.

電流密度２５Ａ／Ｄｄ，，ＫＯＨ２Ｏ％として、同じ構
造の電解槽Ａ，Ｂ，Ｃの３槽を用いた。Three electrolytic cells A, B, and C having the same structure were used at a current density of 25 A/Dd, KOH2O%.

これら３槽を５ケ月間に亘つて運転したが、その初期、
３ケ月後および５ケ月後の電圧と電流効率を第１表に示
す（■は電圧、％は電流効率）。次にこの運転による５
ケ月後に、電解槽より膜を取り外し、常温で歩−ＨＣｌ
中に４８１１ｒ浸漬し、水洗後再び電解槽に取付けて運
転した（第２回操業運転）。These three tanks were operated for five months, but at the beginning,
The voltage and current efficiency after 3 months and 5 months are shown in Table 1 (■ indicates voltage, % indicates current efficiency). Next, 5 by this operation
After several months, remove the membrane from the electrolytic cell and soak it with HCl at room temperature.
After washing with water, it was installed in the electrolytic cell again and operated (second operation).

５ケ月間に亘る運転の初期、２ケ月後および５ケ月後の
電圧、電流効率の測定結果を第２表に示す。Table 2 shows the measurement results of voltage and current efficiency at the initial stage, after 2 months, and after 5 months of operation for 5 months.

この電解運転においてＡの電解槽は２ケ月に亘る運転の
結果、電流、電流効率が極度に悪化したので運転を停止
し、分解点検したところ、チタンにピンホールが発生し
鉄が腐蝕していた。During this electrolytic operation, the current and current efficiency of electrolytic cell A had deteriorated extremely after two months of operation, so operation was stopped and an overhaul revealed that pinholes had formed in the titanium and the iron had corroded. .

ＢおよびＣの電解槽は５ケ月後に分解して膜を取外し、
電解槽Ｂの膜Ｂは常温でへーＨＣｌ中に４８Ｆ１ｒ浸漬
し、一方電解槽Ｃの膜Ｃ″は別途準備した次に述べる膜
再生用の電解槽に取付けて２Ａ／ｄボ常温で５１１ｒ通
電して電解運転を行なつた。即ち、この電解槽はＰＶＣ
製で陽極、陰極はカーボンを使用し、陽極室、陰極室に
は共に駆一ＨＣｌを供給し酸性溶液によつて満たされた
ものである。After 5 months, the electrolytic cells B and C were disassembled and the membranes were removed.
Membrane B in electrolytic cell B was immersed in 48F1r at room temperature, while membrane C'' in electrolytic cell C was attached to a separately prepared electrolytic cell for membrane regeneration described below, and energized at 2 A/d at room temperature in 511r. In other words, this electrolytic cell was made of PVC
The anode and cathode are made of carbon, and the anode and cathode chambers are both filled with an acidic solution supplied with HCl.

この電解運転で陽極室出口のＨＣｌ濃度は略へに、又陰
極室出口のＨＣｌ濃度は略駆を示した。During this electrolytic operation, the HCl concentration at the anode chamber outlet was approximately zero, and the HCl concentration at the cathode chamber outlet was approximately zero.

このように処理した膜Ｂ″，Ｃ″を再び元の電解槽にそ
れぞれ取付けて前記と同様の運転を行つた。初期及び２
週間後の電圧と電流効率を第３表に示す。尚、電解槽Ａ
の膜Ａ″は常温で駆−ＨＣｌに４８１１ｒ浸漬し再び電
解槽に取付けて１週間運転したところ４．３Ｖの電圧を
示した。The membranes B'' and C'' treated in this way were each reattached to the original electrolytic cell and operated in the same manner as described above. Early and 2
Table 3 shows the voltage and current efficiency after a week. Furthermore, electrolytic cell A
Membrane A'' was immersed in di-HCl at room temperature for 4811r, then attached to the electrolytic cell again and operated for one week, and showed a voltage of 4.3V.

そこでこれを再び取外し前記膜再生用の電解槽に取付け
て１Ａ／ＤｄｌｌＯｈｒで電解運転を行つた。この電解
槽の陽極室へは駆−ＨＣｌを供給したが、戻りのＨＣｌ
は略３．５Ｎであつた。又陰極室へはＨＣｌを３５ｇ／
ｅ含む２５０ｇ／′濃度のＫＣｌブラインを供給した。
この膜を元の電解槽に取付けて１週間運転したところ電
圧は４．０Ｖ１電流効率は９５％を示した。実施例２ 陽イオン交換膜をＮａｆｉＯｎ３３６（ＤｕＰＯｎｔ社
製）とし、ブライン精製として更に脱鉄用のキレート樹
脂層への通液を付加させた以外は実施例１の初回操業運
転に準じてＤおよびＥの電解槽による電解運転を行なつ
た。Therefore, it was removed again, attached to the electrolytic cell for membrane regeneration, and electrolyzed at 1 A/DdllOhr. Although hydrogen-HCl was supplied to the anode chamber of this electrolytic cell, the return HCl
was approximately 3.5N. In addition, 35g/HCl was added to the cathode chamber.
A KCl brine with a concentration of 250 g/' was fed.
When this membrane was attached to the original electrolytic cell and operated for one week, the voltage was 4.0 V and the current efficiency was 95%. Example 2 D and E were carried out in accordance with the initial operation of Example 1, except that the cation exchange membrane was NafiOn336 (manufactured by DuPOnt) and that the liquid was passed through a chelate resin layer for iron removal as brine purification. Electrolysis operation was carried out using an electrolytic cell.

初期および８ケ月後の電圧、電流効率の測定結果を第４
表に示す。８ケ月の運転後、膜を取り外し、電解槽Ｄの
膜Ｄ″は常温で△−ＨＣｌ中に９６１１ｒ浸漬し、電解
槽ＥＪの膜Ｅ″は膜再生用の電解槽に取付け２Ａ／ｄイ
で１０ｈｒの電解を行なつた。The measurement results of voltage and current efficiency at the initial stage and after 8 months are summarized in the fourth stage.
Shown in the table. After 8 months of operation, the membrane was removed, and the membrane D'' of electrolytic cell D was immersed in 9611r of △-HCl at room temperature, and the membrane E'' of electrolytic cell EJ was installed in an electrolytic cell for membrane regeneration at 2A/d. Electrolysis was performed for 10 hours.

この電解槽の陽極へは３．５Ｎ−ＨＣｌを供給し、戻り
のＨＣｌ濃度を３．０Ｎとし、陰極室へはＨＣＩを３．
５ｇ／ｅ含む２５０ｇ／′のＮａＣｌブラインを供給し
た。７ これらの膜を再び電解槽に取付けて運転した結
果を第５表に示す。3.5N HCl is supplied to the anode of this electrolytic cell, the return HCl concentration is set to 3.0N, and 3.5N HCl is supplied to the cathode chamber.
250 g/' of NaCl brine containing 5 g/e was fed. 7 These membranes were reattached to the electrolytic cell and operated, and the results are shown in Table 5.

実施例３ 陽イオン交換膜としてＮａｆｉＯｎ２２７（ＤｕＰＯｎ
ｔ社製）を用いて実施例１と同様の電解槽１槽でＮａＣ
ｌ水溶液の初回電解操業運転を行なつた。Example 3 NafiOn227 (DuPOn
(manufactured by T company) in one electrolytic cell similar to Example 1.
An initial electrolytic operation using aqueous solution was carried out.

ブラインは脱Ｍｇ，Ｃａキレート樹脂により精製たもの
を用い、３００ｇ／ｅ（７）ＮａＣＩブラインを分解率
３０％になるように供給し、ＮａＯＩ度２０％で電流密
度２５Ａ／Ｄｄで電解した。６ケ月に亘る電解運転の結
果を第６表に示す。The brine purified using a Mg-free, Ca chelating resin was used, and 300 g/e(7) NaCI brine was supplied so that the decomposition rate was 30%, and electrolysis was performed at a NaOI degree of 20% and a current density of 25 A/Dd. Table 6 shows the results of electrolysis operation over 6 months.

６ケ月後に電解槽から膜を取り出し、この膜の中央部よ
り１５ｃｍ四角の膜２枚を切り出し、その内の１枚膜Ｆ
″を常温でパーＨＣｌ中に他の１枚（膜Ｇ″）を膜再生
用の電解槽に取付けて１Ａ／Ｄｄで１０ｈｒ電解した。After 6 months, take out the membrane from the electrolytic cell, cut out two 15cm square membranes from the center of this membrane, and cut out one membrane F.
'' was placed in Par HCl at room temperature, and the other membrane G'' was attached to an electrolytic tank for membrane regeneration and electrolyzed at 1 A/Dd for 10 hours.

この電解槽の陽極室へはへーＨＣｌを供給して、戻りが
△−ＨＣｌとなるようにし、陰極室へはＨＣＩを５ｇ／
ｆ含むＮａ２ＳＯ４８Ｏｇ／ｆを陰極室へ供給した。こ
れらの膜を再び実施例１と同様の電解槽ＦおよびＧに取
付けて運転した結果を第７表に示す。HCl is supplied to the anode chamber of this electrolytic cell so that the return becomes △-HCl, and 5g/HCl is supplied to the cathode chamber.
Na2SO48Og/f containing f was supplied to the cathode chamber. These membranes were again attached to electrolytic cells F and G similar to those in Example 1 and operated, and Table 7 shows the results.

Claims (1)

【特許請求の範囲】[Claims] １ 陽イオン交換膜法塩化アルカリ水溶液電解によつて
汚染された陽イオン交換膜を再生するに当り、陰陽両極
室の極液を共に酸性に維持した電解槽内に該汚染陽イオ
ン交換膜を取付けて通電することを特徴とする陽イオン
交換膜の再生方法。1. Cation Exchange Membrane Method When regenerating a cation exchange membrane contaminated by aqueous alkaline chloride electrolysis, the contaminated cation exchange membrane is installed in an electrolytic cell in which both the cathode and cathode electrode compartments are kept acidic. 1. A method for regenerating a cation exchange membrane, the method comprising applying current to the cation exchange membrane.