JP2010151714A - Silica concentration measuring method - Google Patents
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- JP2010151714A JP2010151714A JP2008331942A JP2008331942A JP2010151714A JP 2010151714 A JP2010151714 A JP 2010151714A JP 2008331942 A JP2008331942 A JP 2008331942A JP 2008331942 A JP2008331942 A JP 2008331942A JP 2010151714 A JP2010151714 A JP 2010151714A
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 137
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 98
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 43
- 238000002835 absorbance Methods 0.000 claims abstract description 22
- 150000007522 mineralic acids Chemical class 0.000 claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 6
- 239000001257 hydrogen Substances 0.000 claims abstract description 6
- -1 hydrogen ions Chemical class 0.000 claims abstract description 6
- 239000007864 aqueous solution Substances 0.000 claims description 33
- 239000000243 solution Substances 0.000 claims description 19
- 238000000691 measurement method Methods 0.000 claims description 12
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 claims description 6
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 15
- 238000007689 inspection Methods 0.000 description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 10
- 238000005259 measurement Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000013078 crystal Substances 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 150000004685 tetrahydrates Chemical class 0.000 description 6
- 229910052750 molybdenum Inorganic materials 0.000 description 5
- 239000011733 molybdenum Substances 0.000 description 5
- 235000006408 oxalic acid Nutrition 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000008235 industrial water Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 239000003673 groundwater Substances 0.000 description 2
- MEFBJEMVZONFCJ-UHFFFAOYSA-N molybdate Chemical compound [O-][Mo]([O-])(=O)=O MEFBJEMVZONFCJ-UHFFFAOYSA-N 0.000 description 2
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000008399 tap water Substances 0.000 description 2
- 235000020679 tap water Nutrition 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 150000002751 molybdenum Chemical class 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- GEVPUGOOGXGPIO-UHFFFAOYSA-N oxalic acid;dihydrate Chemical compound O.O.OC(=O)C(O)=O GEVPUGOOGXGPIO-UHFFFAOYSA-N 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 229940085991 phosphate ion Drugs 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
- Investigating Or Analysing Materials By The Use Of Chemical Reactions (AREA)
Abstract
Description
本発明は、シリカ濃度測定方法、特に、検査水のシリカ濃度を測定するための方法に関する。 The present invention relates to a silica concentration measurement method, and more particularly to a method for measuring the silica concentration of test water.
ボイラ給水、冷却塔の補給水および電気式脱塩装置（ＥＤＩ）による脱塩処理により純水化される被処理水等として用いられる水道水、工業用水および地下水等の原水は、微量のシリカを含んでいる。ボイラや冷却塔において、原水に含まれるシリカは、スケールの発生原因となるが、同時にボイラや冷却塔の各所の腐食を抑制する作用も有するため、その適切な濃度管理が要求される。また、ＥＤＩにおいて、原水に含まれるシリカは、イオン交換樹脂に吸着し、再生工程においても脱着しにくいことから徐々に蓄積してイオン交換能を低下させるため、予め前処理工程で除去されている。したがって、ＥＤＩ用の被処理水は、シリカ濃度を測定することで、シリカの除去状態の確認が要求される。 Raw water such as boiler water, cooling tower replenishment water, and treated water that is purified by desalination using an electrical demineralizer (EDI), such as tap water, industrial water, and groundwater, contains a trace amount of silica. Contains. In boilers and cooling towers, silica contained in raw water causes scale, but at the same time, it also has an action of suppressing corrosion in various places in the boiler and cooling towers, so that appropriate concentration management is required. In EDI, silica contained in raw water is adsorbed on the ion exchange resin and is difficult to desorb in the regeneration process, so that it gradually accumulates and lowers the ion exchange capacity. Therefore, it is removed in advance in the pretreatment process. . Therefore, the EDI water to be treated is required to confirm the silica removal state by measuring the silica concentration.
ボイラ給水、冷却塔の補給水およびＥＤＩの被処理水等におけるシリカ濃度は、通常、非特許文献１において規定されたモリブデン黄吸光光度法により測定される。このモリブデン黄吸光光度法では、ボイラ給水等から採取した検査水に対して所定濃度の七モリブデン酸六アンモニウム溶液と所定濃度の塩酸とを加えて放置した後、検査水における４１０〜４５０ｎｍの吸光度を測定する。ここで、検査水にシリカ（イオン状シリカ）が含まれる場合、このシリカが七モリブデン酸六アンモニウムとの反応により黄色のヘテロポリ化合物を生成し、検査水はこのヘテロポリ化合物の生成量に応じて検査水を黄色に変色させる。このため、検査水のシリカ濃度は、黄色の吸光度である４１０〜４５０ｎｍの吸光度に基づいて判定することができる。なお、この測定方法において用いられる所定濃度の七モリブデン酸六アンモニウム溶液は、七モリブデン酸六アンモニウム四水和物の所定量を水に溶かして所定量の水溶液としたものである。 The silica concentration in boiler feed water, cooling tower makeup water, EDI treated water, and the like is usually measured by the molybdenum yellow absorptiometry defined in Non-Patent Document 1. In this molybdenum yellow absorptiometry, after adding a predetermined concentration of hexaammonium heptamolybdate solution and a predetermined concentration of hydrochloric acid to test water collected from boiler feed water or the like, the absorbance at 410 to 450 nm in the test water is measured. taking measurement. Here, when the inspection water contains silica (ionic silica), this silica generates a yellow heteropoly compound by reaction with hexaammonium heptamolybdate, and the inspection water is inspected according to the amount of the heteropoly compound generated. Turn the water yellow. For this reason, the silica concentration of test water can be determined based on the absorbance at 410 to 450 nm, which is the yellow absorbance. The predetermined concentration of hexaammonium heptamolybdate solution used in this measuring method is obtained by dissolving a predetermined amount of hexaammonium hexamolybdate tetrahydrate in water to form a predetermined amount of aqueous solution.
ところで、この測定方法において用いられる七モリブデン酸六アンモニウム溶液は、保存安定性を欠き、調製後の早い段階からモリブデン酸の結晶の析出が進行する。特に、この結晶の析出は、高温になるほど進行が速い。結晶の析出した七モリブデン酸六アンモニウム溶液は、検査水に含まれるイオン状シリカとの反応性が低下するため、シリカ濃度の測定結果の信頼性を損ねることになる。このため、七モリブデン酸六アンモニウム溶液は、シリカ濃度を測定する度に調製するのが望ましい。 By the way, the hexaammonium heptamolybdate solution used in this measurement method lacks storage stability, and precipitation of molybdic acid crystals proceeds from an early stage after preparation. In particular, the precipitation of this crystal proceeds faster as the temperature increases. The hexaammonium heptamolybdate solution in which crystals are precipitated has a reduced reactivity with ionic silica contained in the test water, and therefore the reliability of the measurement result of the silica concentration is impaired. For this reason, it is desirable to prepare the hexaammonium heptamolybdate solution each time the silica concentration is measured.
また、ボイラ装置等は、各部の制御の自動化が進められており、自動制御のために必要な水質データを含む各種のデータも自動測定により得ているため、原水等のシリカ濃度の測定もモリブデン黄吸光光度法による自動化の要請がある。この場合、七モリブデン酸六アンモニウム溶液は、予め調製したものを試薬タンクに保存しておいて適宜使用する必要があるが、上述のような結晶の析出が進行するため、このような目的での保存が困難である。特に、七モリブデン酸六アンモニウム溶液は、結晶の析出が進むと、測定結果の信頼性を損うだけではなく、シリカ濃度の自動測定装置において試薬供給経路などを閉塞させ、自動測定装置の動作不良を引き起こす可能性もある。したがって、これまでのモリブデン黄吸光光度法は、シリカ濃度の自動測定への適用が困難である。 In addition, the automation of the control of each part of boiler equipment, etc. has been promoted, and various data including water quality data necessary for automatic control are obtained by automatic measurement. There is a request for automation by yellow absorptiometry. In this case, the hexamolybdenum hexamolybdate solution needs to be stored in a reagent tank and used as appropriate. However, since the precipitation of crystals as mentioned above proceeds, It is difficult to save. In particular, the hexamolybdate hexamolybdate solution not only impairs the reliability of the measurement results as crystals progress, but also blocks the reagent supply path in the silica concentration automatic measurement device, causing the automatic measurement device to malfunction. May also cause. Therefore, the conventional molybdenum yellow absorptiometry is difficult to apply to automatic measurement of silica concentration.
本発明の目的は、自動化に適用可能な、七モリブデン酸六アンモニウムを用いた検査水のシリカ濃度の測定方法を実現することにある。 An object of the present invention is to realize a method for measuring the silica concentration of test water using hexaammonium heptamolybdate that can be applied to automation.
本発明のシリカ濃度測定方法は、検査水のシリカ濃度を測定するための方法であり、七モリブデン酸六アンモニウムと無機酸とを含む試薬水溶液を検査水へ添加する工程と、試薬水溶液が添加された検査水について、４１０〜４５０ｎｍの吸光度を測定する工程と、測定した吸光度に基づいて、検査水に含まれるシリカ濃度を判定する工程とを含んでいる。ここで用いられる試薬水溶液は、七モリブデン酸六アンモニウムに対する水素イオンのモル比が少なくとも４４．５になるよう七モリブデン酸六アンモニウムと無機酸との混合割合が設定されている。 The silica concentration measurement method of the present invention is a method for measuring the silica concentration of test water, a step of adding a reagent aqueous solution containing hexaammonium heptamolybdate and an inorganic acid to the test water, and the addition of the reagent aqueous solution. The test water includes a step of measuring the absorbance at 410 to 450 nm and a step of determining the silica concentration contained in the test water based on the measured absorbance. In the reagent aqueous solution used here, the mixing ratio of hexaammonium heptamolybdate and an inorganic acid is set so that the molar ratio of hydrogen ions to hexaammonium heptamolybdate is at least 44.5.
この測定方法では、例えば、試薬水溶液が添加された検査水を少なくとも２５℃に設定して放置した後に吸光度を測定する。また、この測定方法では、例えば、試薬水溶液が添加された検査水のｐＨを１．１〜１．６に調節して放置した後に吸光度を測定する。 In this measurement method, for example, the absorbance is measured after leaving the test water to which the reagent aqueous solution is added at least at 25 ° C. and leaving it to stand. In this measurement method, for example, the absorbance is measured after adjusting the pH of the test water to which the reagent aqueous solution has been added to 1.1 to 1.6 and leaving it to stand.
本発明に係る検査水のシリカ濃度測定用試薬は、七モリブデン酸六アンモニウムと無機酸とを含む水溶液からなり、七モリブデン酸六アンモニウムに対する水素イオンのモル比が少なくとも４４．５になるよう七モリブデン酸六アンモニウムと無機酸との混合割合が設定されている。 The reagent for measuring the silica concentration of test water according to the present invention comprises an aqueous solution containing hexaammonium heptamolybdate and an inorganic acid, so that the molar ratio of hydrogen ions to hexaammonium heptamolybdate is at least 44.5. The mixing ratio of acid ammonium ammonium and inorganic acid is set.
本発明のシリカ濃度測定用試薬は、七モリブデン酸六アンモニウムと無機酸との混合割合を上記のように設定していることから結晶の析出が抑制されるので、調製後に保存することができ、また、長期間安定に使用することができる。したがって、この試薬を用いる本発明に係るシリカ濃度の測定方法は、自動化に適している。 Since the silica concentration measurement reagent of the present invention is set as described above for the mixing ratio of hexaammonium heptamolybdate and an inorganic acid, precipitation of crystals is suppressed, and can be stored after preparation. Moreover, it can be used stably for a long time. Therefore, the silica concentration measuring method according to the present invention using this reagent is suitable for automation.
本発明の測定方法は、検査水におけるシリカ濃度を測定するための方法である。
この測定方法を適用可能な検査水は、水中のシリカ濃度の測定が必要な水であれば種類が限定されるものではなく、例えば、水道水、工業用水および地下水等に由来のボイラ給水、ボイラ水、冷却塔補給水、冷却塔循環水、逆浸透膜装置での被処理水および濃縮水並びにＥＤＩ用の被処理水などである。また、この測定方法により測定可能なシリカは、イオン状シリカである。したがって、検査水がイオン状シリカとは異なる他のシリカ、すなわち、溶存シリカおよびコロイド状シリカを含む場合は、検査水に炭酸水素ナトリウムを加えて煮沸し、これらのシリカ成分をイオン状シリカに変換してから本発明の測定方法を適用する必要がある。
The measuring method of the present invention is a method for measuring the silica concentration in test water.
The type of test water to which this measurement method can be applied is not limited as long as it is necessary to measure the silica concentration in the water. For example, boiler water derived from tap water, industrial water, groundwater, etc. Water, cooling tower make-up water, cooling tower circulating water, water to be treated and concentrated water in the reverse osmosis membrane device, water to be treated for EDI, and the like. Silica measurable by this measuring method is ionic silica. Therefore, when the test water contains other silica different from ionic silica, that is, dissolved silica and colloidal silica, boil by adding sodium bicarbonate to the test water and convert these silica components into ionic silica Then, it is necessary to apply the measurement method of the present invention.
本発明の測定方法においては、通常、所定の試薬水溶液を予め調製し、この試薬水溶液を保存する。ここで調製する試薬水溶液は、七モリブデン酸六アンモニウムと無機酸とを含むものであり、シリカを含まない水（例えば、ＪＩＳ Ｋ ０５５７に規定されたＡ３の水）に七モリブデン酸六アンモニウムおよび無機酸を添加して溶解したものである。 In the measurement method of the present invention, a predetermined aqueous reagent solution is usually prepared in advance, and this aqueous reagent solution is stored. The aqueous reagent solution prepared here contains hexaammonium heptamolybdate and an inorganic acid, and it contains hexaammonium heptamolybdate and an inorganic substance in water that does not contain silica (for example, water of A3 defined in JIS K 0557). An acid is added and dissolved.
ここで用いられる七モリブデン酸六アンモニウムは、通常、四水和物である。また、無機酸としては、通常、塩酸、硝酸または硫酸が用いられる。試薬水溶液における七モリブデン酸六アンモニウムの濃度（結晶水を除いた七モリブデン酸六アンモニウム自体の濃度）は特に限定されないが、検査水に含まれるものと通常予想されるシリカの濃度との関係および試薬水溶液の添加量節約の観点から、３０〜１２０ｇ／リットルに設定するのが好ましく、５０〜１００ｇ／リットルに設定するのがより好ましい。 The hexaammonium heptamolybdate used here is usually a tetrahydrate. As the inorganic acid, hydrochloric acid, nitric acid or sulfuric acid is usually used. The concentration of hexaammonium heptamolybdate in the aqueous reagent solution (the concentration of hexaammonium heptamolybdate itself excluding crystallization water) is not particularly limited, but the relationship between the concentration in the test water and the expected silica concentration and the reagent From the viewpoint of saving the added amount of the aqueous solution, it is preferably set to 30 to 120 g / liter, and more preferably set to 50 to 100 g / liter.
また、試薬水溶液を調製する際に用いる七モリブデン酸六アンモニウム若しくはその四水和物と無機酸との混合割合は、七モリブデン酸六アンモニウムに対する、無機酸に由来の水素イオンのモル比が少なくとも４４．５、好ましくは４６以上になるよう設定する。試薬水溶液は、このモル比を少なくとも４４．５に設定することで、検査水のシリカ濃度の測定時の一般的な温度環境、具体的には−５〜５０℃の温度環境において、結晶が析出しにくくなり、長期間保存することができるようになる。 In addition, the mixing ratio of hexaammonium heptamolybdate or its tetrahydrate and inorganic acid used when preparing the reagent aqueous solution is such that the molar ratio of hydrogen ions derived from the inorganic acid to hexammammonium hexamolybdate is at least 44. .5, preferably 46 or more. By setting this molar ratio to at least 44.5, the aqueous solution of the reagent precipitates crystals in a general temperature environment when measuring the silica concentration of the test water, specifically in a temperature environment of -5 to 50 ° C. It becomes difficult to store and can be stored for a long time.
また、上記モル比は、後述するように、試薬水溶液を添加した検査水のｐＨが１．１未満まで低下してしまうと反応速度が大きく低下することから、５０以下に設定するのが好ましい。 Further, as described later, the molar ratio is preferably set to 50 or less because the reaction rate is greatly lowered when the pH of the test water to which the aqueous reagent solution is added is lowered to less than 1.1.
検査水のシリカ濃度は、上述の試薬水溶液を用いて次の工程により測定することができる。
（工程１）
シリカ濃度の測定が必要な水から所定量の検査水を量り取る。試料水は、ろ紙５種Ｃ若しくはろ紙６種または孔径０．４５〜１μｍのろ過材を用いて予めろ過しておくのが好ましい。また、試料水は、シリカ濃度が高いものと予想されるときは、希釈するのが好ましい。
The silica concentration of the inspection water can be measured by the following process using the above-described reagent aqueous solution.
(Process 1)
A predetermined amount of test water is weighed out of water that requires measurement of the silica concentration. The sample water is preferably preliminarily filtered using a filter paper of 5 types C or 6 types of filter paper or a filter medium having a pore diameter of 0.45 to 1 μm. The sample water is preferably diluted when the silica concentration is expected to be high.
（工程２）
工程１の検査水に対して試薬水溶液を添加し、これを振り混ぜて放置する。これにより、検査水にイオン状シリカが含まれる場合、このイオン状シリカは、七モリブデン酸六アンモニウムと反応して黄色のヘテロポリ化合物を生成し、検査水を黄色に着色する。
(Process 2)
The reagent aqueous solution is added to the test water in step 1, and this is shaken and allowed to stand. Thereby, when ionic silica is contained in the inspection water, this ionic silica reacts with hexaammonium heptamolybdate to produce a yellow heteropoly compound, and the inspection water is colored yellow.
試薬水溶液の添加量は、通常、検査水における七モリブデン酸六アンモニウムの濃度が検査水に含まれると予想されるシリカの濃度に対してモル比で２倍当量以上になるよう設定するのが好ましい。また、試薬水溶液を添加した検査水の放置時間は、検査水に含まれるイオン状シリカの全量と七モリブデン酸六アンモニウムとの反応が完結するよう設定するのが好ましい。特に、シリカ濃度が高い検査水を測定する場合、試薬水溶液の添加量が相対的に増加することから、試薬水溶液を添加した検査水のｐＨが１．１未満まで低下してしまい、この反応速度が大きく低下するため、これを考慮して十分な放置時間を確保する必要がある。 The amount of the reagent aqueous solution added is usually preferably set so that the concentration of hexaammonium heptamolybdate in the test water is two times the molar equivalent to the concentration of silica expected to be contained in the test water. . Moreover, it is preferable that the leaving time of the inspection water to which the reagent aqueous solution is added is set so that the reaction between the total amount of ionic silica contained in the inspection water and hexaammonium heptamolybdate is completed. In particular, when measuring test water having a high silica concentration, since the amount of the reagent aqueous solution added is relatively increased, the pH of the test water to which the reagent aqueous solution is added is reduced to less than 1.1. In view of this, it is necessary to secure a sufficient standing time.
イオン状シリカとモリブデン酸六アンモニウムとの反応は、検査水を加熱することで加速することができる。この場合、検査水は少なくとも２５℃以上になるよう設定するのが好ましい。また、イオン状シリカとモリブデン酸六アンモニウムとの反応は、検査水のｐＨを１．１〜１．６に調節することで加速することもできる。検査水のｐＨは、検査水に対してアルカリ金属やアルカリ土類金属の水酸化物、例えば、水酸化ナトリウム、水酸化カリウムおよび水酸化カルシウムの水溶液を添加することで上記範囲に調節することができる。検査水の加熱とｐＨ調節とは併用することもできる。検査水の加熱またはｐＨ調節により上述の反応を加速すると、試薬水溶液を添加した検査水の放置時間は大幅に短縮することができるため、シリカ濃度の測定に要する時間を効果的に短縮することができる。 The reaction between the ionic silica and hexammonium molybdate can be accelerated by heating the inspection water. In this case, it is preferable to set the inspection water to be at least 25 ° C. The reaction between ionic silica and hexaammonium molybdate can be accelerated by adjusting the pH of the test water to 1.1 to 1.6. The pH of the test water can be adjusted to the above range by adding an alkali metal or alkaline earth metal hydroxide to the test water, for example, an aqueous solution of sodium hydroxide, potassium hydroxide or calcium hydroxide. it can. The heating of the inspection water and the pH adjustment can be used in combination. If the above reaction is accelerated by heating the test water or adjusting the pH, the time for leaving the test water to which the reagent aqueous solution has been added can be greatly shortened, so the time required for measuring the silica concentration can be effectively shortened. it can.
（工程３）
工程２において放置した検査水について、４１０〜４５０ｎｍの波長の吸光度を分光光度計または光電光度計により測定し、その吸光度に基づいて検査水のシリカ濃度を判定する。ここでは、例えば、上記吸光度とシリカ濃度との関係を調べて検量線を作成しておき、この検量線に基づいて検査水中のシリカ濃度（ｍｇＳｉＯ２／リットル）を判定する。
(Process 3)
For the test water left in step 2, the absorbance at a wavelength of 410 to 450 nm is measured with a spectrophotometer or a photoelectric photometer, and the silica concentration of the test water is determined based on the absorbance. Here, for example, a calibration curve is created by examining the relationship between the absorbance and the silica concentration, and the silica concentration (mgSiO 2 / liter) in the test water is determined based on the calibration curve.
上述の測定方法において、検査水がリン酸イオンを含む場合は、工程２の後、検査水に対してシュウ酸水溶液を添加する。これにより、リン酸イオンがシリカ濃度の測定結果に影響するのを抑制することができる。ここで用いられるシュウ酸水溶液は、シュウ酸二水和物を水に溶かしてシュウ酸換算の濃度が７１．４ｇ／リットルになるよう調製したものである。シュウ酸水溶液の添加量は、検査水１００容量部に対して３容量部に設定するのが好ましい。また、シュウ酸水溶液を添加した検査水は、１分間放置した後、直ちに工程３において吸光度を測定する。この放置時間が１分を超えると、イオン状シリカと七モリブデン酸六アンモニウムとの反応により生成したヘテロポリ化合物による黄色の着色が徐々に退色し、検査水のシリカ濃度と上記吸光度との関係が変動する可能性がある。 In the measurement method described above, when the inspection water contains phosphate ions, an aqueous oxalic acid solution is added to the inspection water after step 2. Thereby, it can suppress that a phosphate ion influences the measurement result of a silica concentration. The aqueous oxalic acid solution used here is prepared by dissolving oxalic acid dihydrate in water so that the concentration in terms of oxalic acid is 71.4 g / liter. The addition amount of the oxalic acid aqueous solution is preferably set to 3 parts by volume with respect to 100 parts by volume of the inspection water. In addition, the test water to which the oxalic acid aqueous solution is added is allowed to stand for 1 minute, and immediately after that, in step 3, the absorbance is measured. If this standing time exceeds 1 minute, the yellow coloration due to the heteropoly compound produced by the reaction of ionic silica and hexaammonium heptamolybate gradually fades, and the relationship between the silica concentration of the test water and the absorbance changes. there's a possibility that.
なお、上述の測定方法は、非特許文献１に記載されたモリブデン黄吸光光度法を参照して実施することができる。特に、工程２を除く各工程での操作および各工程で用いる試薬等は、モリブデン黄吸光光度法での規定に基づいて実行または調製することができる。 The measurement method described above can be performed with reference to the molybdenum yellow absorptiometry described in Non-Patent Document 1. In particular, the operations in each step except step 2 and the reagents and the like used in each step can be executed or prepared based on the regulations in the molybdenum yellow absorptiometry.
上述の測定方法は、予め調製して保存しておいた試薬水溶液を用いることができるため、簡便かつ迅速に実行することができ、また、試薬水溶液の保存安定性が求められる自動化に適している。 Since the above-described measurement method can use a reagent aqueous solution prepared and stored in advance, it can be easily and quickly executed, and is suitable for automation requiring storage stability of the reagent aqueous solution. .
実験例１
七モリブデン酸六アンモニウム四水和物をＪＩＳ Ｋ ０５５７に規定されたＡ３の水に溶解し、七モリブデン酸六アンモニウムの濃度がそれぞれ０．０４０ｍｏｌ／リットル、０．０６１ｍｏｌ／リットルおよび０．０８１ｍｏｌ／リットルの３種類の水溶液を調製した。そして、各水溶液に対し、水素イオンのモル濃度が表１に示すようになるよう硫酸と塩酸を加え、試薬水溶液を調製した。この試薬水溶液を５０℃の温度環境下に４ヶ月間放置し、モリブデン酸の結晶の析出状況を目視により観察した。結果を表１に示す。表１によると、試薬水溶液において、七モリブデン酸六アンモニウムに対する水素イオンのモル比が４４．５以上の場合は、調整後に４ヶ月経過しても結晶の析出が見られず、保存に適していることがわかる。
Experimental example 1
Hexammonium hexamolybdate tetrahydrate was dissolved in A3 water specified in JIS K 0557, and the concentrations of hexaammonium heptamolybdate were 0.040 mol / liter, 0.061 mol / liter and 0.081 mol / liter, respectively. Three types of aqueous solutions were prepared. Then, sulfuric acid and hydrochloric acid were added to each aqueous solution so that the molar concentration of hydrogen ions was as shown in Table 1, to prepare a reagent aqueous solution. This aqueous reagent solution was allowed to stand in a temperature environment of 50 ° C. for 4 months, and the state of precipitation of molybdic acid crystals was visually observed. The results are shown in Table 1. According to Table 1, in the reagent aqueous solution, when the molar ratio of hydrogen ion to hexaammonium heptamolybdate is 44.5 or more, no crystal deposition is observed even after 4 months from the preparation, which is suitable for storage. I understand that.
実験例２
シリカ濃度（イオン状シリカ濃度）が１００ｍｇＳｉＯ２／リットルに設定された検査水試料を調製した。また、ＪＩＳ Ｋ ０５５７に規定されたＡ３の水に七モリブデン酸六アンモニウム四水和物を溶解した後、硫酸と塩酸を混合し、七モリブデン酸六アンモニウムの濃度が０．０８１ｍｏｌ／リットルでありかつ水素イオンの濃度が３．６ｍｏｌ／リットルである試薬水溶液（七モリブデン酸六アンモニウムに対する水素イオンのモル比が４４．５）を調製した。そして、検査水試料１０ミリリットルに対して試薬水溶液０．６ミリリットルを添加して振り混ぜ、その温度を４℃、８℃、１２℃、１６℃、２０℃または２５℃に維持した状態で４１０〜４５０ｎｍの吸光度の経時的な変化を調べた。結果を図１に示す。図１によると、温度が２５℃未満の場合は吸光度が最大値に到達するまでの時間（すなわち、検査水試料に含まれるイオン状シリカの全量と七モリブデン酸六アンモニウムとの反応完結に要する時間）が１２００秒（２０分）以上であるのに対し、温度が２５℃の場合の同時間は約６００秒（約１０分）に短縮されることがわかる。
Experimental example 2
A test water sample having a silica concentration (ionic silica concentration) set to 100 mg SiO 2 / liter was prepared. Further, after dissolving hexaammonium hexamolybdate tetrahydrate in the water of A3 specified in JIS K 0557, sulfuric acid and hydrochloric acid are mixed, and the concentration of hexaammonium heptamolybdate is 0.081 mol / liter, and A reagent aqueous solution having a hydrogen ion concentration of 3.6 mol / liter (a molar ratio of hydrogen ion to hexaammonium heptamolybdate of 44.5) was prepared. Then, 0.6 ml of an aqueous reagent solution is added to 10 ml of the test water sample and shaken, and the temperature is maintained at 4 ° C., 8 ° C., 12 ° C., 16 ° C., 20 ° C. or 25 ° C. The change with time in absorbance at 450 nm was examined. The results are shown in FIG. According to FIG. 1, when the temperature is less than 25 ° C., the time required for the absorbance to reach the maximum value (that is, the time required for completing the reaction between the total amount of ionic silica contained in the test water sample and hexaammonium heptamolybdate). ) Is 1200 seconds (20 minutes) or more, while the same time when the temperature is 25 ° C. is shortened to about 600 seconds (about 10 minutes).
実験例３
シリカ濃度（イオン状シリカ濃度）が２００ｍｇＳｉＯ２／リットルに設定された検査水試料を調製した。また、ＪＩＳ Ｋ ０５５７に規定されたＡ３の水に七モリブデン酸六アンモニウム四水和物を溶解した後、硫酸と塩酸を混合し、七モリブデン酸六アンモニウムの濃度が０．０８１ｍｏｌ／リットルでありかつ水素イオンの濃度が３．６ｍｏｌ／リットルである試薬水溶液（七モリブデン酸六アンモニウムに対する水素イオンのモル比が４４．５）を調製した。そして、検査水試料１０ミリリットルに対して試薬水溶液０．９ミリリットルを添加して振り混ぜた後、さらに水酸化ナトリウム水溶液を添加してｐＨを１．１〜１．６に調節し、温度を５℃または２５℃に維持した状態で４１０〜４５０ｎｍの吸光度の経時的な変化を調べた。結果を図２に示す。図２によると、吸光度が最大値に到達するまでの時間（すなわち、検査水試料に含まれるイオン状シリカの全量と七モリブデン酸六アンモニウムとの反応完結に要する時間）は、２５℃の場合が約３００秒（約５分）、５℃の場合は約６００秒（約１０分）であり、実験例２と対比すると、５℃の低温の場合でも短縮されていることがわかる。
Experimental example 3
A test water sample having a silica concentration (ionic silica concentration) set to 200 mg SiO 2 / liter was prepared. Further, after dissolving hexaammonium hexamolybdate tetrahydrate in the water of A3 specified in JIS K 0557, sulfuric acid and hydrochloric acid are mixed, and the concentration of hexaammonium heptamolybdate is 0.081 mol / liter, and A reagent aqueous solution having a hydrogen ion concentration of 3.6 mol / liter (a molar ratio of hydrogen ion to hexaammonium heptamolybdate of 44.5) was prepared. Then, after adding 0.9 ml of an aqueous reagent solution to 10 ml of the test water sample and shaking and mixing, an aqueous sodium hydroxide solution is further added to adjust the pH to 1.1 to 1.6, and the temperature is adjusted to 5 The change with time of the absorbance at 410 to 450 nm was examined while maintaining the temperature at 25 ° C. The results are shown in FIG. According to FIG. 2, the time until the absorbance reaches the maximum value (that is, the time required to complete the reaction between the total amount of ionic silica contained in the test water sample and hexaammonium heptamolybdate) is 25 ° C. About 300 seconds (about 5 minutes) and 5 ° C., it is about 600 seconds (about 10 minutes). Compared with Experimental Example 2, it can be seen that the temperature is shortened even at a low temperature of 5 ° C.
Claims (4)
七モリブデン酸六アンモニウムと無機酸とを含む試薬水溶液を前記検査水へ添加する工程と、
前記試薬水溶液が添加された前記検査水について、４１０〜４５０ｎｍの吸光度を測定する工程と、
測定した前記吸光度に基づいて、前記検査水に含まれるシリカ濃度を判定する工程とを含み、
前記試薬水溶液は、前記七モリブデン酸六アンモニウムに対する水素イオンのモル比が少なくとも４４．５になるよう前記七モリブデン酸六アンモニウムと前記無機酸との混合割合が設定されている、
シリカ濃度測定方法。 A method for measuring the silica concentration of test water,
Adding an aqueous reagent solution containing hexaammonium heptamolybdate and an inorganic acid to the test water;
Measuring the absorbance at 410 to 450 nm for the test water to which the reagent aqueous solution has been added;
And determining a silica concentration contained in the test water based on the measured absorbance,
In the reagent aqueous solution, the mixing ratio of the hexamolybdenum hexamolybdate and the inorganic acid is set so that the molar ratio of hydrogen ion to hexammonium heptamolybdate is at least 44.5.
Method for measuring silica concentration.
前記七モリブデン酸六アンモニウムに対する水素イオンのモル比が少なくとも４４．５になるよう前記七モリブデン酸六アンモニウムと前記無機酸との混合割合が設定されている、
検査水のシリカ濃度測定用試薬。 Consisting of an aqueous solution containing hexaammonium heptamolybdate and an inorganic acid,
The mixing ratio of the hexaammonium heptamolybdate and the inorganic acid is set so that the molar ratio of hydrogen ions to the hexaammonium heptamolybdate is at least 44.5.
Reagent for measuring silica concentration in test water.
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| JP2013011584A (en) * | 2011-05-30 | 2013-01-17 | Kanazawa Inst Of Technology | Inspection method of concrete modification agent, and device therefor |
| JP2014228468A (en) * | 2013-05-24 | 2014-12-08 | 栗田工業株式会社 | Silica concentration measuring method and device |
| JP2016099255A (en) * | 2014-11-21 | 2016-05-30 | 三浦工業株式会社 | Silica concentration measurement apparatus |
| JP2016099254A (en) * | 2014-11-21 | 2016-05-30 | 三浦工業株式会社 | Silica concentration measurement apparatus |
| JP2018021918A (en) * | 2017-08-23 | 2018-02-08 | 栗田工業株式会社 | Concentration measurement apparatus for dissolved component |
| JP2019066220A (en) * | 2017-09-29 | 2019-04-25 | Ｋｂセーレン株式会社 | Method for measuring silica adhesion amount of synthetic fiber |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013011584A (en) * | 2011-05-30 | 2013-01-17 | Kanazawa Inst Of Technology | Inspection method of concrete modification agent, and device therefor |
| JP2014228468A (en) * | 2013-05-24 | 2014-12-08 | 栗田工業株式会社 | Silica concentration measuring method and device |
| JP2016099255A (en) * | 2014-11-21 | 2016-05-30 | 三浦工業株式会社 | Silica concentration measurement apparatus |
| JP2016099254A (en) * | 2014-11-21 | 2016-05-30 | 三浦工業株式会社 | Silica concentration measurement apparatus |
| JP2018021918A (en) * | 2017-08-23 | 2018-02-08 | 栗田工業株式会社 | Concentration measurement apparatus for dissolved component |
| JP2019066220A (en) * | 2017-09-29 | 2019-04-25 | Ｋｂセーレン株式会社 | Method for measuring silica adhesion amount of synthetic fiber |
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