JP6143627B2 - Ammonia recovery method - Google Patents
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- JP6143627B2 JP6143627B2 JP2013208671A JP2013208671A JP6143627B2 JP 6143627 B2 JP6143627 B2 JP 6143627B2 JP 2013208671 A JP2013208671 A JP 2013208671A JP 2013208671 A JP2013208671 A JP 2013208671A JP 6143627 B2 JP6143627 B2 JP 6143627B2
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims description 238
- 229910021529 ammonia Inorganic materials 0.000 title claims description 113
- 238000000034 method Methods 0.000 title claims description 48
- 238000011084 recovery Methods 0.000 title claims description 40
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 132
- 229910052709 silver Inorganic materials 0.000 claims description 121
- 239000004332 silver Substances 0.000 claims description 121
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 105
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 98
- PLKATZNSTYDYJW-UHFFFAOYSA-N azane silver Chemical compound N.[Ag] PLKATZNSTYDYJW-UHFFFAOYSA-N 0.000 claims description 92
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 33
- 239000000460 chlorine Substances 0.000 claims description 28
- 229910052801 chlorine Inorganic materials 0.000 claims description 27
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 25
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 17
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 17
- 239000000243 solution Substances 0.000 claims description 15
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 10
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- 239000007864 aqueous solution Substances 0.000 claims description 8
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- 239000011780 sodium chloride Substances 0.000 claims description 5
- 235000002639 sodium chloride Nutrition 0.000 claims description 5
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- 150000003841 chloride salts Chemical class 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- 239000001103 potassium chloride Substances 0.000 claims description 2
- 235000011164 potassium chloride Nutrition 0.000 claims description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 14
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 14
- 229910021607 Silver chloride Inorganic materials 0.000 description 12
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 239000007788 liquid Substances 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
- 239000002699 waste material Substances 0.000 description 9
- 238000004880 explosion Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- -1 silver ions Chemical class 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000002360 explosive Substances 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 6
- 239000003446 ligand Substances 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000000084 colloidal system Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000000976 ink Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000010992 reflux Methods 0.000 description 4
- 239000002351 wastewater Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 150000001408 amides Chemical class 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 229910001385 heavy metal Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- DTPQZKZONQKKSU-UHFFFAOYSA-N silver azanide silver Chemical compound [NH2-].[Ag].[Ag].[Ag+] DTPQZKZONQKKSU-UHFFFAOYSA-N 0.000 description 3
- 229920003169 water-soluble polymer Polymers 0.000 description 3
- VRZJGENLTNRAIG-UHFFFAOYSA-N 4-[4-(dimethylamino)phenyl]iminonaphthalen-1-one Chemical compound C1=CC(N(C)C)=CC=C1N=C1C2=CC=CC=C2C(=O)C=C1 VRZJGENLTNRAIG-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 125000001309 chloro group Chemical group Cl* 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 150000003378 silver Chemical class 0.000 description 2
- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 2
- GGCZERPQGJTIQP-UHFFFAOYSA-N sodium;9,10-dioxoanthracene-2-sulfonic acid Chemical compound [Na+].C1=CC=C2C(=O)C3=CC(S(=O)(=O)O)=CC=C3C(=O)C2=C1 GGCZERPQGJTIQP-UHFFFAOYSA-N 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001723 curing Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000013007 heat curing Methods 0.000 description 1
- 150000003949 imides Chemical class 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 229910001923 silver oxide Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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- Manufacture And Refinement Of Metals (AREA)
Description
本発明は、銀アンモニア溶液からのアンモニア回収方法に関するものであり、特に、爆発性を有する雷銀の生成を抑えて銀アンモニア溶液から安全にアンモニアを回収する方法に関する。 The present invention relates to a method for recovering ammonia from a silver ammonia solution, and particularly to a method for safely recovering ammonia from a silver ammonia solution while suppressing the formation of explosive thunder silver.
電子機器における配線層や電極などの導電膜の形成には、銀粉を含んだ銀ペーストや銀インクが多用されている。これら銀ペーストや銀インクは、加熱硬化あるいは加熱焼成によって銀粉が連なって電気的に接続した電流パスを形成するので、配線層や電極となる導電膜の材料として用いられている。例えば、銀ペーストの一種である樹脂型銀ペーストは、銀粉、樹脂、硬化剤、および溶剤などからなり、これを回路パターンや端子形状に印刷し、１００℃〜２００℃で加熱硬化させることで配線や電極用の導電膜を形成することができる。また、銀ペーストの一種である焼成型銀ペーストは、銀粉、ガラス、および溶剤などからなり、これを回路パターンや端子形状に印刷し、６００℃〜８００℃で加熱焼成することで配線や電極用の導電膜を形成することができる。 For the formation of conductive layers such as wiring layers and electrodes in electronic devices, silver paste and silver ink containing silver powder are frequently used. These silver pastes and silver inks are used as conductive film materials for wiring layers and electrodes because they form a current path in which silver powders are connected and electrically connected by heat curing or heat baking. For example, a resin-type silver paste, which is a kind of silver paste, consists of silver powder, resin, curing agent, solvent, etc., printed on a circuit pattern or terminal shape, and cured by heating at 100 ° C to 200 ° C. And a conductive film for an electrode can be formed. Moreover, the baking type silver paste which is 1 type of silver paste consists of silver powder, glass, a solvent, etc., this is printed on a circuit pattern or a terminal shape, and is used for wiring or an electrode by baking at 600 to 800 degreeC. The conductive film can be formed.
かかる銀ペーストに使用する銀粉の粒径は一般に０.１μｍから数μｍ程度であり、形成する配線の幅や電極の厚さに応じて異なる粒径の銀粉が使用される。銀粉はペースト中で均一に分散させることが望ましく、これにより均一な厚みと幅を有する配線や均一な厚みを有する電極を形成することができる。一方、銀インクはタッチパネルや高電流を必要しない配線材として用いられており、使用される銀粉の粒径は数ｎｍから０.１μｍ程度であり、銀ペーストよりも細かい銀粉が使用される。 The particle size of silver powder used for such silver paste is generally about 0.1 μm to several μm, and silver powder having different particle sizes is used depending on the width of the wiring to be formed and the thickness of the electrode. The silver powder is desirably dispersed uniformly in the paste, whereby a wiring having a uniform thickness and width and an electrode having a uniform thickness can be formed. On the other hand, silver ink is used as a wiring material that does not require a touch panel or high current, and the particle size of silver powder used is about several nm to 0.1 μm, and silver powder finer than silver paste is used.
これら銀ペーストや銀インクの製造コストでは銀粉が高い割合を占めており、低コストに銀粉を製造することが重要視されている。そのため、銀粉はアンモニアを用いた湿式還元法で製造されることが多い。アンモニアは銀イオンと安定な銀アンミン錯体を形成するため還元反応を制御しやすく、湿式還元法による銀粉の製造では有効な成分である。さらに、アンモニアは一般に薬剤コストが低く、廃液処理において容易に回収可能な薬剤である点においても工業上有利である。 In the production costs of these silver pastes and silver inks, silver powder occupies a high proportion, and it is important to produce silver powder at a low cost. Therefore, silver powder is often produced by a wet reduction method using ammonia. Ammonia forms a stable silver ammine complex with silver ions, making it easy to control the reduction reaction, and is an effective component in the production of silver powder by a wet reduction method. Further, ammonia is industrially advantageous in that it is generally low in drug cost and can be easily recovered in waste liquid treatment.
しかし、アンモニアは人体や環境に有害な物質であり、アンモニアを含む廃液を周辺環境に放出したり、あるいはアンモニアガスとして大気中に放出することは法律で制限されている。そのため、アンモニアを含む廃液は通常は放出前にアンモニアを除去する処理が施されている。この処理法には、例えば非特許文献１に示すようなアンモニアストリッピング法、薬剤または触媒による分解処理法、微生物による生物学的処理法、イオン交換法による吸着処理法等を挙げることができる。これらの内、アンモニア濃度が０.１質量％以上の高濃度の場合は、アンモニアストリッピング法によるアンモニアの回収が行われることが多い。アンモニアストリッピング法は、他の方法に比べて処理に要するエネルギー消費量が少なく、設備も簡易でコストを抑えることができるからである。 However, ammonia is a substance harmful to the human body and the environment, and it is legally restricted to discharge waste liquid containing ammonia to the surrounding environment or to the atmosphere as ammonia gas. Therefore, the waste liquid containing ammonia is usually subjected to a treatment for removing ammonia before release. Examples of the treatment method include an ammonia stripping method as shown in Non-Patent Document 1, a decomposition treatment method using a drug or a catalyst, a biological treatment method using a microorganism, an adsorption treatment method using an ion exchange method, and the like. Among these, when the ammonia concentration is a high concentration of 0.1% by mass or more, ammonia is often recovered by an ammonia stripping method. This is because the ammonia stripping method requires less energy consumption than other methods, has simple equipment, and can reduce costs.
アンモニアストリッピング法は、下記式１に示すように水酸化物イオンを添加することにより平衡を左に傾かせてアンモニアを非解離状態で遊離させ、さらに温度を上げることによってアンモニアガスの溶解度を下げて遊離したアンモニアガスを排水から分離する方法である。分離してアンモニアガスはアンモニア水として回収したり、硫酸に吸収させて硫酸アンモニウムとして回収したりできる。あるいは、触媒と接触させることにより窒素ガスに分解して無害化する方法がとられることがある。なお、式１の関係から水酸化物イオン濃度が高い方がアンモニアガスになりやすく、工業的にはｐＨ１１以上が好ましいとされている。
［式１］
ＮＨ３＋Ｈ２Ｏ ⇔ ＮＨ４ＯＨ ⇔ ＮＨ４ ＋＋ＯＨ−
In the ammonia stripping method, as shown in the following formula 1, by adding hydroxide ions, the equilibrium is tilted to the left to release ammonia in a non-dissociated state, and the solubility of ammonia gas is lowered by raising the temperature further. This is a method for separating the released ammonia gas from the waste water. Separately, the ammonia gas can be recovered as aqueous ammonia, or absorbed into sulfuric acid and recovered as ammonium sulfate. Alternatively, a method of decomposing and detoxifying nitrogen gas by contacting with a catalyst may be used. In addition, from the relationship of Formula 1, the higher the hydroxide ion concentration, the easier it becomes ammonia gas, and it is considered industrially that the pH is 11 or more.
[Formula 1]
NH 3 + H 2 O⇔NH 4 OH⇔NH 4 + + OH −
特許文献１には、排水中の重金属イオンを水溶性ポリマーに吸着させた後、該水溶性ポリマーを分離膜を用いて分離し、分離後の液をアンモニアストリッピング法で処理してアンモニアを回収する技術が開示されている。排水中の重金属イオンの分離を行うには水酸化物や還元による重金属の分離の方が効率的であり、特許文献１の技術は水溶性ポリマーの処理および分離膜の維持コストがかかるという欠点がある。また、特許文献２には、アンモニア性窒素含有水に酸化剤を添加したのち、加温下で金属触媒と接触させてアンモニアを分解し、窒素ガスとして回収する技術が開示されている。 In Patent Document 1, heavy metal ions in waste water are adsorbed on a water-soluble polymer, and then the water-soluble polymer is separated using a separation membrane, and the separated liquid is treated by an ammonia stripping method to recover ammonia. Techniques to do this are disclosed. Separation of heavy metal ions in wastewater is more efficient by separation of heavy metals by hydroxide or reduction, and the technique of Patent Document 1 has a drawback that it costs water-soluble polymer treatment and separation membrane maintenance costs. is there. Patent Document 2 discloses a technique in which an oxidizing agent is added to ammoniacal nitrogen-containing water, and then brought into contact with a metal catalyst under heating to decompose ammonia and recover it as nitrogen gas.
銀を含んだアンモニア溶液中では、銀イオンの大部分は銀アンミン錯体の形態で存在しており、この銀アンミン錯体は、条件によっては爆発性の雷銀を生成する可能性がある。これは、銀溶液やその廃液を管理しながら処理する反応槽内や配管系内のみならず、銀溶液やその廃液が飛散して乾固した場合も同様である。そのため、銀粉の製造工程における銀を含んだ銀溶液の一連の処理においては勿論、銀粉の製造工程から排出される廃液の取り扱いにおいても安全性に考慮する必要がある。 In an ammonia solution containing silver, most of silver ions are present in the form of a silver ammine complex, and this silver ammine complex may generate explosive thunder silver depending on conditions. This is the same not only in the reaction tank and the piping system in which the silver solution and its waste liquid are managed, but also when the silver solution and its waste liquid are scattered and dried. Therefore, it is necessary to consider safety not only in the series of processing of the silver solution containing silver in the silver powder manufacturing process but also in the handling of the waste liquid discharged from the silver powder manufacturing process.
しかしながら、従来のアンモニアを含む廃液の処理方法では、銀とアンモニアとを含む溶液に対して爆発性の雷銀の発生の回避を考慮しながらアンモニアを回収する方法については検討されていなかった。本発明は上記したような銀とアンモニアとを含む溶液の処理が抱える課題に鑑みてなされたものであり、銀アンミン錯体を含む溶液に対して、危険な雷銀を発生させることなく安全にアンモニアを回収する方法を提供することを目的としている。 However, in the conventional method for treating waste liquid containing ammonia, a method for recovering ammonia in consideration of avoiding the generation of explosive thunder silver in a solution containing silver and ammonia has not been studied. The present invention has been made in view of the problems of processing of a solution containing silver and ammonia as described above, and can safely be used for a solution containing a silver ammine complex without causing dangerous lightning silver. It aims to provide a method for recovering.
本発明の発明者らは、銀アンミン錯体がアンモニア回収工程において雷銀を生成する条件について鋭意研究を重ねた結果、銀を含んだアンモニア溶液（以降、銀アンモニア溶液と称する）に含まれる成分の濃度や温度を限定することにより雷銀の生成を抑えて安全にアンモニアを回収できることを見出し本発明を完成するに至った。 The inventors of the present invention have conducted extensive research on the conditions under which silver ammine complexes generate thunder silver in the ammonia recovery process, and as a result, of the components contained in the silver-containing ammonia solution (hereinafter referred to as silver ammonia solution). By limiting the concentration and temperature, it was found that ammonia can be recovered safely by suppressing the formation of thunder silver, and the present invention has been completed.
すなわち、本発明が提供するアンモニアの回収方法の第１形態は、銀とアンモニアとを少なくとも含有する銀アンモニア溶液からアンモニアを回収する方法であって、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を前記銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１と等しくするか又は１より大きくし、且つ該銀アンモニア溶液中の水酸化アルカリの濃度を０.０００１ｍｏｌ／Ｌ以上０.０５ｍｏｌ／Ｌ以下とし、アンモニア回収時の銀アンモニア溶液の温度を５０℃より高くすることを特徴としている。 That is, the first form of the ammonia recovery method provided by the present invention is a method of recovering ammonia from a silver ammonia solution containing at least silver and ammonia, and the total chlorine contained in the silver ammonia solution before ammonia recovery The value obtained by dividing the molar concentration of silver by the molar concentration of total silver contained in the silver ammonia solution is equal to or greater than 1, and the concentration of alkali hydroxide in the silver ammonia solution is 0.0001 mol / L. The temperature is 0.05 mol / L or less, and the temperature of the silver ammonia solution at the time of ammonia recovery is higher than 50 ° C.
また、本発明が提供するアンモニアの回収方法の第２形態は、銀とアンモニアとを少なくとも含有する銀アンモニア溶液からアンモニアを回収する方法であって、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を前記銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１と等しくするか又は１より大きくし、且つ該銀アンモニア溶液中の水酸化アルカリの濃度を０.０５ｍｏｌ／Ｌを超え０.１ｍｏｌ／Ｌ以下とし、アンモニア回収時の銀アンモニア溶液の温度を５０℃以下にすることを特徴としている。 A second form of the ammonia recovery method provided by the present invention is a method of recovering ammonia from a silver ammonia solution containing at least silver and ammonia, and the total chlorine contained in the silver ammonia solution before ammonia recovery. The value obtained by dividing the molar concentration of silver by the molar concentration of total silver contained in the silver ammonia solution is equal to or greater than 1, and the concentration of alkali hydroxide in the silver ammonia solution is 0.05 mol / L. And 0.1 mol / L or less, and the temperature of the silver ammonia solution at the time of ammonia recovery is 50 ° C. or less.
さらに、本発明が提供するアンモニアの回収方法の第３形態は、銀とアンモニアとを少なくとも含有する銀アンモニア溶液からアンモニアを回収する方法であって、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を前記銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１.０７以上とし、且つ該銀アンモニア溶液中の水酸化アルカリの濃度を０.０５ｍｏｌ／Ｌを超え０.２ｍｏｌ／Ｌ以下にすることを特徴としている。 Furthermore, the third form of the ammonia recovery method provided by the present invention is a method of recovering ammonia from a silver ammonia solution containing at least silver and ammonia, and the total chlorine contained in the silver ammonia solution before ammonia recovery The value obtained by dividing the molar concentration of silver by the molar concentration of total silver contained in the silver ammonia solution is set to 1.07 or more, and the concentration of alkali hydroxide in the silver ammonia solution exceeds 0.05 mol / L and is 0.2 mol. / L or less.
本発明によれば、爆発性の雷銀の生成を抑制しながらアンモニアを効率よく回収して再利用できるので、その工業的価値は極めて高い。 According to the present invention, ammonia can be efficiently recovered and reused while suppressing the generation of explosive thunder silver, and thus its industrial value is extremely high.
以下、本発明に係るアンモニアの回収方法を、銀粉や銀コロイドの製造工程から排出される銀アンミン錯体を含む銀アンモニア溶液からストリッピング法でアンモニアを回収する場合を例に挙げて説明する。銀粉や銀コロイド溶液の製造方法では、アンモニアを含有する水溶液に必要に応じて塩化物塩を添加した後、銀塩を溶解して銀アンミン錯体を含む銀アンモニア溶液を作製し、この銀アンモニア溶液に還元剤を添加して銀イオンを還元することで銀微粒子を形成し、得られた銀微粒子を含む懸濁液を固液分離して銀粉を作製したり銀コロイド溶液を作製したりすることが行われている。 Hereinafter, the ammonia recovery method according to the present invention will be described by taking as an example the case of recovering ammonia by a stripping method from a silver ammonia solution containing a silver ammine complex discharged from the production process of silver powder or silver colloid. In the method for producing silver powder or silver colloid solution, a silver salt solution containing a silver ammine complex is prepared by dissolving a silver salt after adding a chloride salt to an aqueous solution containing ammonia as required. Forming silver fine particles by reducing silver ions by adding a reducing agent to the suspension, and solid-liquid separation of the resulting suspension containing silver fine particles to produce silver powder or silver colloid solution Has been done.
必要に応じてアンモニア溶液に添加する塩化物塩は、溶解しないものや還元反応の際に水酸化物のような沈殿物を生じるものは好ましくないが、それ以外あれば特に限定はない。例えば、塩化ナトリウム、塩化カリウム、塩化アンモニウム、塩化リチウムなどを使用することができる。 The chloride salt added to the ammonia solution as needed is not preferred if it does not dissolve or produces a precipitate such as a hydroxide during the reduction reaction, but otherwise there is no particular limitation. For example, sodium chloride, potassium chloride, ammonium chloride, lithium chloride and the like can be used.
上記の製造方法では、形成する銀微粒子の粒径や形状、銀コロイドの特性などによっては銀イオンをすべて還元するとは限られず、この場合は未還元の銀アンミン錯体を含む溶液が発生する。また、銀アンミン錯体をすべて還元する工程であっても量産工程では還元を行う反応槽内での反応の偏りなどで、未還元の銀アンミン錯体を含んだ溶液が発生することもある。このような残留する未反応の銀アンミン錯体は、後段のアンモニア回収工程において処理する際、雷銀の生成により爆発などの危険を孕んでいることが問題になる。すなわち、銀アンミン錯体溶液は、乾燥、加熱、またはアルカリ性物質の添加を行うことにより、溶液中のアンモニア濃度が下がり、雷銀が生成されるので、その生成を抑える安全対策が重要となる。ここで雷銀とは、窒化銀、アミド銀、およびイミド銀などの銀を含む爆発性物質の一般的な総称である。 In the above production method, the silver ions are not necessarily all reduced depending on the particle diameter and shape of the silver fine particles to be formed and the characteristics of the silver colloid. In this case, a solution containing an unreduced silver ammine complex is generated. Further, even in the process of reducing all of the silver ammine complex, a solution containing unreduced silver ammine complex may be generated due to the bias of the reaction in the reaction tank in which reduction is performed in the mass production process. When such a remaining unreacted silver ammine complex is treated in a subsequent ammonia recovery step, there is a problem that a danger such as an explosion is generated due to generation of thunder silver. That is, when the silver ammine complex solution is dried, heated, or added with an alkaline substance, the ammonia concentration in the solution is lowered and thundersilver is generated. Therefore, it is important to take safety measures to suppress the generation. Here, lightning silver is a general term for explosive substances including silver such as silver nitride, amide silver, and imide silver.
具体的な雷銀の発生過程としては、銀アンミン錯体を含む銀アンモニア溶液を乾燥濃縮させると、銀アンミン錯体から配位子のアンモニアが外れてアミド銀（ＡｇＮＨ２）が生成する。これは意図的に銀アンモニア溶液を濃縮する場合に限られず、例えば反応槽や配管系から銀アンモニア溶液が飛散して乾燥濃縮した場合も同様に雷銀が形成される。また、銀アンミン錯体を含む銀アンモニア溶液にアルカリを加えた場合は、銀アンミン錯体から配位子のアンモニアが外れ、これによりアミド銀が生成して窒化銀の生成が進行する。 As a specific generation process of lightning silver, when a silver ammonia solution containing a silver ammine complex is dried and concentrated, the ammonia of the ligand is removed from the silver ammine complex to produce amide silver (AgNH 2 ). This is not limited to intentionally concentrating the silver ammonia solution. For example, lightning silver is also formed when the silver ammonia solution scatters from the reaction tank or piping system and is concentrated by drying. Further, when an alkali is added to a silver ammonia solution containing a silver ammine complex, the ligand ammonia is removed from the silver ammine complex, whereby amide silver is produced and silver nitride proceeds.
例えば非特許文献２よれば、銀アンミン錯体を含む銀アンモニア溶液に水酸化カリウムを添加すると、下記式２および式３の反応を経由して爆発性を有する窒化銀Ａｇ３Ｎが生成することが開示されている。このことから、アルカリの添加により雷銀の生成が促進されると考えられる。
［式２］
［Ａｇ（ＮＨ３）］２＋＋ＯＨ−→ＡｇＮＨ２＋ＮＨ３＋Ｈ２Ｏ
［式３］
ＡｇＮＨ２→Ａｇ３Ｎ＋２ＮＨ３
For example, according to Non-Patent Document 2, when potassium hydroxide is added to a silver ammonia solution containing a silver ammine complex, explosive silver nitride Ag 3 N may be generated via the reactions of the following formulas 2 and 3. It is disclosed. From this, it is considered that the formation of thunder silver is promoted by the addition of alkali.
[Formula 2]
[Ag (NH 3 )] 2+ + OH − → AgNH 2 + NH 3 + H 2 O
[Formula 3]
AgNH 2 → Ag 3 N + 2NH 3
ところで、廃液からアンモニア等を回収するアンモニアストリッピング法では、より高い効率でストリッピングするために廃液を加熱することが行われており、これは上記した式２の反応を促進させることになるため、ｐＨや温度の制御だけでは雷銀の生成を防止することは困難である。そこで、本発明者らは銀とアンモニアを含む銀アンモニア溶液に対して雷銀の生成を抑えながらアンモニアを良好にストリッピングできる条件について鋭意研究した結果、下記に述べるように、アンモニア回収前の銀アンモニア溶液中の全塩素のモル濃度と全銀のモル濃度との比率及び水酸化アルカリのモル濃度、並びにアンモニア回収時の銀アンモニア溶液の温度にそれぞれ所定の制限を課した３つの条件においては、いずれも雷銀を生成しないことを見出した。 By the way, in the ammonia stripping method for recovering ammonia and the like from the waste liquid, the waste liquid is heated in order to perform stripping with higher efficiency, and this promotes the reaction of the above formula 2. It is difficult to prevent the formation of lightning silver only by controlling the pH and temperature. Therefore, as a result of intensive studies on the conditions under which ammonia can be satisfactorily stripped while suppressing the formation of thunder silver with respect to a silver ammonia solution containing silver and ammonia, the present inventors, as described below, In the three conditions in which predetermined limits are imposed respectively on the ratio of the molar concentration of total chlorine to the molar concentration of total silver in the ammonia solution, the molar concentration of alkali hydroxide, and the temperature of the silver ammonia solution at the time of ammonia recovery, Neither of them found that it produces thunder silver.
ここで、全塩素のモル濃度とは、銀アンモニア溶液中に含まれるＣｌ−で示される塩素イオンやＣｌ２で示される塩素分子、さらには銀アンモニア溶液中に塩素の化合物として存在するものの全てを塩素原子に換算したモル濃度である。また、全銀のモル濃度とは、銀アンモニア溶液中の銀の化学種を銀原子に換算したモル濃度であり、この場合、銀はほとんどが銀アンミン錯体［Ａｇ（ＮＨ３）２］＋として存在するが、化学平衡により銀アンミン錯体以外の錯体として存在する銀イオンが含まれる。さらに、水酸化アルカリとは、水酸化リチウム、水酸化ナトリウム、および水酸化カリウムのうちのいずれか１つ以上である。 Here, the molar concentration of total chlorine refers to all of the chlorine ions represented by Cl − and chlorine molecules represented by Cl 2 contained in the silver ammonia solution, as well as all the compounds existing as chlorine compounds in the silver ammonia solution. The molar concentration in terms of chlorine atoms. The total silver molar concentration is the molar concentration obtained by converting the chemical species of silver in the silver ammonia solution into silver atoms. In this case, most of the silver is converted into a silver ammine complex [Ag (NH 3 ) 2 ] +. Although present, silver ions that are present as complexes other than silver ammine complexes due to chemical equilibrium are included. Furthermore, the alkali hydroxide is any one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide.
まず、第１の条件は、アンモニア回収前の銀アンモニア溶液が下記式４または式５のいずれかの関係を満たすように、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を該銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１と等しくするか又は１より大きくし、また、アンモニア回収前の銀アンモニア溶液中の水酸化アルカリ濃度を０.０００１ｍｏｌ／Ｌ以上０.０５ｍｏｌ／Ｌ以下とし、更にアンモニア回収時の銀アンモニア溶液の加熱温度を５０℃より高い温度にする条件である。この条件下でアンモニアを回収すれば、雷銀を生成することはない。 First, the first condition is that the molar concentration of total chlorine contained in the silver ammonia solution before ammonia recovery is adjusted so that the silver ammonia solution before ammonia recovery satisfies either of the following formulas 4 and 5. The value divided by the molar concentration of total silver contained in the ammonia solution is made equal to or greater than 1, and the alkali hydroxide concentration in the silver ammonia solution before ammonia recovery is 0.0001 mol / L or more and 0.001. The temperature is set to 05 mol / L or less, and the heating temperature of the silver ammonia solution at the time of ammonia recovery is set to a temperature higher than 50 ° C. If ammonia is recovered under these conditions, no lightning silver is produced.
［式４］
１＝（全塩素のモル濃度）／（全銀のモル濃度）
［式５］
１＜（全塩素のモル濃度）／（全銀のモル濃度）
[Formula 4]
1 = (Molar concentration of total chlorine) / (Molar concentration of total silver)
[Formula 5]
1 <(Molar concentration of total chlorine) / (Molar concentration of total silver)
アンモニア回収前の銀アンモニア溶液が上記式４および式５のいずれをも満たさない場合、すなわち、アンモニア回収前の銀アンモニア溶液中の全塩素のモル濃度を全銀のモル濃度で除した値が１未満の場合は、塩素が不足するため塩化銀の生成が不安定となり、雷銀が生成されてしまう。また、水酸化アルカリ濃度が０.０００１ｍｏｌ／Ｌ未満では前述した式１の平衡が左に傾きにくく、溶液中でアンモニウムイオンとして残留する割合が高くなり、アンモニアの回収効率が著しく下がることになる。一方、水酸化アルカリ濃度が０.０５ｍｏｌ／Ｌを超えると、銀アンミン錯体からアンモニア配位子が外れやすくなり、雷銀の生成を促進させることになる。アンモニアの回収時は、銀アンモニア溶液を５０℃より高くする必要があり、８５℃以上に加熱するのが好ましい。８５℃よりも低いとアンモニアの回収効率が悪くなるからである。 When the silver ammonia solution before ammonia recovery does not satisfy any of the above formulas 4 and 5, that is, the value obtained by dividing the molar concentration of total chlorine in the silver ammonia solution before ammonia recovery by the molar concentration of total silver is 1. If it is less than 1, chlorine is insufficient and the production of silver chloride becomes unstable, and lightning silver is produced. In addition, when the alkali hydroxide concentration is less than 0.0001 mol / L, the equilibrium of the above-described formula 1 is not easily inclined to the left, the ratio of remaining ammonium ions in the solution is increased, and the ammonia recovery efficiency is significantly reduced. On the other hand, when the alkali hydroxide concentration exceeds 0.05 mol / L, the ammonia ligand is easily detached from the silver ammine complex, and the generation of lightning silver is promoted. At the time of recovery of ammonia, the silver ammonia solution needs to be higher than 50 ° C., and is preferably heated to 85 ° C. or higher. This is because when the temperature is lower than 85 ° C., the ammonia recovery efficiency deteriorates.
次に、第２の条件は、アンモニア回収前の銀アンモニア溶液が上記式４または式５のいずれかの関係を満たすように、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を該銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１と等しくするか又は１より大きくし、また、アンモニア回収前の銀アンモニア溶液中の水酸化アルカリの濃度を０.０５ｍｏｌ／Ｌを超えて０.１ｍｏｌ／Ｌ以下とし、更にアンモニア回収時の銀アンモニア溶液の温度を５０℃以下にする条件である。この条件下でアンモニアを回収すれば、雷銀を生成することはない。 Next, the second condition is that the molar concentration of total chlorine contained in the silver ammonia solution before ammonia recovery is adjusted so that the silver ammonia solution before ammonia recovery satisfies either of the above formulas 4 or 5. The value divided by the molar concentration of total silver contained in the silver ammonia solution is made equal to 1 or larger than 1, and the concentration of alkali hydroxide in the silver ammonia solution before ammonia recovery is set to 0.05 mol / L. This is a condition of exceeding 0.1 mol / L and further making the temperature of the silver ammonia solution at the time of ammonia recovery 50 ° C. or less. If ammonia is recovered under these conditions, no lightning silver is produced.
このように、水酸化アルカリ濃度が０.０５ｍｏｌ／Ｌを超え０.１ｍｏｌ／Ｌ以下であっても、銀アンモニア溶液の温度を５０℃以下に保てば、雷銀の生成を抑制することができる。０.１ｍｏｌ／Ｌを超えると、５０℃以下であっても銀アンミン錯体からアンモニア配位子が外れやすくなり、雷銀の生成を促進させることになる。この第２の条件は第１の条件よりもアンモニア回収時の温度が低いため、アンモニアストリッピングの際は減圧することが望ましい。 Thus, even if the alkali hydroxide concentration is more than 0.05 mol / L and not more than 0.1 mol / L, if the temperature of the silver ammonia solution is kept at 50 ° C. or less, generation of thunder silver can be suppressed. it can. When it exceeds 0.1 mol / L, the ammonia ligand is easily detached from the silver ammine complex even at 50 ° C. or lower, and the formation of thunder silver is promoted. Since this second condition has a lower temperature during ammonia recovery than the first condition, it is desirable to reduce the pressure during ammonia stripping.
そして、第３の条件は、下記式６の関係を満たすように、アンモニア回収前の銀アンモニア溶液に含まれる全塩素のモル濃度を前記銀アンモニア溶液に含まれる全銀のモル濃度で除した値を１.０７以上とし、且つ水酸化アルカリ濃度が０.２ｍｏｌ／Ｌ以下とすることで雷銀を生成せずに処理できることを見出した。このように塩素原子を過剰にすることにより、水酸化アルカリ濃度が０.１ｍｏｌ／Ｌを超え０.２ｍｏｌ／Ｌ以下でも、銀アンミン錯体からアンモニア配位子が外れても塩化銀となる反応が優先され、雷銀の生成を抑制できる。なお、この第３の条件ではアンモニア回収時の温度について特に制約はない。
［式６］
１.０７≦（全塩素のモル濃度）／（全銀のモル濃度）
The third condition is a value obtained by dividing the molar concentration of total chlorine contained in the silver ammonia solution before ammonia recovery by the molar concentration of total silver contained in the silver ammonia solution so as to satisfy the relationship of the following formula 6. It has been found that the process can be carried out without producing thunder silver by setting the pH to 1.07 or more and the alkali hydroxide concentration to 0.2 mol / L or less. By making the chlorine atom excessive in this way, even when the alkali hydroxide concentration exceeds 0.1 mol / L and is 0.2 mol / L or less, the reaction that becomes silver chloride even if the ammonia ligand is removed from the silver ammine complex. Priority is given, and generation of thunder silver can be suppressed. In the third condition, there is no particular restriction on the temperature at the time of ammonia recovery.
[Formula 6]
1.07 ≦ (Molar concentration of total chlorine) / (Molar concentration of total silver)
銀アンモニア溶液に含まれる全塩素のモル濃度を全銀のモル濃度で除した値の上限は特にないが、全塩素のモル濃度が高くなればなるほど水酸化アルカリの濃度を０.２ｍｏｌ／Ｌよりも高くできる可能性が高い。しかしながら、塩化銀の溶解度を超えた場合には塩化銀の析出が生じる可能性が高くなり、また、塩化ナトリウムの析出、中和のための薬剤コストが増加するので、これらの観点から上限を課すのが好ましい。 There is no particular upper limit to the value obtained by dividing the molar concentration of total chlorine contained in the silver ammonia solution by the molar concentration of total silver. However, the higher the molar concentration of total chlorine, the higher the concentration of alkali hydroxide from 0.2 mol / L. Is likely to be higher. However, when the solubility of silver chloride is exceeded, the possibility of silver chloride precipitation increases, and the cost of chemicals for precipitation and neutralization of sodium chloride increases, so an upper limit is imposed from these viewpoints. Is preferred.
［実施例１］
２８％アンモニア水１ｇに塩化銀を６０ｍｇ加えて溶解し、さらに水酸化ナトリウムを０.０５ｍｏｌ／Ｌとなるように加えて銀アンモニア溶液を作製した。この銀アンモニア溶液に含まれる全塩素のモル濃度を全銀のモル濃度で除した値は１.００となる。この銀アンモニア溶液を１００℃まで加熱して得た残留物に波長９２０ｎｍ〜９４０ｎｍ、パルスピーク出力５Ｗ、パルス幅２ｍ秒の赤外線レーザを照射して着火試験を行ったところ、爆発は認められなかった。この結果から、この銀アンモニア溶液は１００℃に加熱しても雷銀の生成はなく安全であることがわかった。
[Example 1]
A silver ammonia solution was prepared by adding 60 mg of silver chloride to 1 g of 28% ammonia water and further adding sodium hydroxide to 0.05 mol / L. A value obtained by dividing the molar concentration of total chlorine contained in the silver ammonia solution by the molar concentration of total silver is 1.00. When an ignition test was performed on the residue obtained by heating the silver ammonia solution to 100 ° C. by irradiating an infrared laser having a wavelength of 920 nm to 940 nm, a pulse peak output of 5 W, and a pulse width of 2 ms, no explosion was observed. . From this result, it was found that this silver ammonia solution was safe even when heated to 100 ° C. without generation of thunder silver.
そこで、還流冷却器を備えた丸底フラスコ内で２８％アンモニア水１０ｇに塩化銀０.６ｇを溶解し、純水１００ｍＬおよび水酸化ナトリウム濃度が０.０５ｍｏｌ／Ｌとなるように加えて銀アンモニア溶液を作製した。この銀アンモニア溶液を設定温度１００℃にして加熱し、その際、還流冷却器から排出されるアンモニアガスを０.１ｍｏｌ／Ｌの硫酸水溶液５０ｍＬに吸収させた。この硫酸水溶液中のアンモニア量をインドフェノール青吸光光度法により分析したところ２.８ｇとなり、ほぼ全量のアンモニアを回収できた。このことから、上記条件の銀アンモニア溶液の場合はアンモニアストリッピング法を用いて効率よく且つ安全にアンモニアを回収できることがわかった。 Therefore, in a round bottom flask equipped with a reflux condenser, 0.6 g of silver chloride was dissolved in 10 g of 28% aqueous ammonia, and added to 100 mL of pure water and a sodium hydroxide concentration of 0.05 mol / L to add silver ammonia. A solution was made. This silver ammonia solution was heated to a set temperature of 100 ° C., and at that time, ammonia gas discharged from the reflux condenser was absorbed into 50 mL of a 0.1 mol / L sulfuric acid aqueous solution. When the amount of ammonia in this sulfuric acid aqueous solution was analyzed by indophenol blue absorptiometry, it was 2.8 g, and almost the entire amount of ammonia was recovered. From this, it was found that in the case of the silver ammonia solution under the above conditions, ammonia can be recovered efficiently and safely using the ammonia stripping method.
［実施例２］
水酸化ナトリウムの濃度を０.０５ｍｏｌ／Ｌに代えて０.０１ｍｏｌ／Ｌとなるように加えた以外は実施例１と同様にして着火試験及びアンモニアの回収を行ったところ、爆発は認められず、また、硫酸水溶液中のアンモニア量が２.７ｇとなり、アンモニアを９５％以上回収できた。このことから、上記条件の銀アンモニア溶液の場合はアンモニアストリッピング法を用いて効率よく且つ安全にアンモニアを回収できることがわかった。
[Example 2]
When an ignition test and recovery of ammonia were performed in the same manner as in Example 1 except that the concentration of sodium hydroxide was changed to 0.01 mol / L instead of 0.05 mol / L, no explosion was observed. In addition, the amount of ammonia in the sulfuric acid aqueous solution was 2.7 g, and it was possible to recover 95% or more of ammonia. From this, it was found that in the case of the silver ammonia solution under the above conditions, ammonia can be recovered efficiently and safely using the ammonia stripping method.
［実施例３］
２８％アンモニア水１ｇに塩化銀６０ｍｇと、塩化ナトリウム１.４９ｍｇと加えて溶解した。さらに水酸化ナトリウムを０.２ｍｏｌ／Ｌとなるように加えて銀アンモニア溶液を作製した。この銀アンモニア溶液に含まれる全塩素のモル濃度を全銀のモル濃度で除した値は１.０７となる。この銀アンモニア溶液に対して実施例１と同様に加熱して着火試験及びアンモニアの回収を行ったところ、爆発は認められず、また、硫酸水溶液中のアンモニア量が２.８ｇとなりほぼ全量のアンモニアを回収できた。このことから、上記条件の銀アンモニア溶液の場合はアンモニアストリッピング法を用いて効率よく且つ安全にアンモニアを回収できることがわかった。
[Example 3]
In 1 g of 28% aqueous ammonia, 60 mg of silver chloride and 1.49 mg of sodium chloride were added and dissolved. Furthermore, sodium hydroxide was added so that it might become 0.2 mol / L, and the silver ammonia solution was produced. The value obtained by dividing the molar concentration of total chlorine contained in the silver ammonia solution by the molar concentration of total silver is 1.07. When this silver ammonia solution was heated in the same manner as in Example 1 to conduct an ignition test and recover ammonia, no explosion was observed, and the amount of ammonia in the sulfuric acid aqueous solution was 2.8 g. Was recovered. From this, it was found that in the case of the silver ammonia solution under the above conditions, ammonia can be recovered efficiently and safely using the ammonia stripping method.
［実施例４］
水酸化ナトリウムの濃度を０.０５ｍｏｌ／Ｌに代えて０.１ｍｏｌ／Ｌとなるように加えた以外は実施例１と同様にして銀アンモニア溶液を作製した。この銀アンモニア溶液を５０℃に加熱して得た残留物に対して実施例１と同様に着火試験を行ったところ、爆発は認められなかった。この結果から、この銀アンモニア溶液は５０℃の加熱では雷銀の生成はなく安全であることがわかった。
[Example 4]
A silver ammonia solution was prepared in the same manner as in Example 1 except that the concentration of sodium hydroxide was changed to 0.1 mol / L instead of 0.05 mol / L. When an ignition test was performed on the residue obtained by heating this silver ammonia solution to 50 ° C. in the same manner as in Example 1, no explosion was observed. From this result, it was found that this silver ammonia solution was safe with no formation of thunder silver when heated at 50 ° C.
そこで、還流冷却器を備えた耐圧の丸底フラスコ内で２８％アンモニア水１０ｇに塩化銀０.６ｇを溶解し、純水１００ｍＬおよび水酸化ナトリウム濃度が０.１ｍｏｌ／Ｌとなるように加え、設定温度を５０℃となるように加熱し、還流冷却器から出たアンモニアガスを−５０ｍｍＨｇとなるように減圧しながら０.１ｍｏｌ／Ｌの硫酸水溶液５０ｍＬに吸収させた。硫酸水溶液中のアンモニア量をインドフェノール青吸光光度法により分析したところ２.６ｇとなり、９０％以上のアンモニアを回収できた。このことから、上記条件の銀アンモニア溶液の場合はアンモニアストリッピング法を用いて効率よく且つ安全にアンモニアを回収できることがわかった。 Therefore, 0.6 g of silver chloride was dissolved in 10 g of 28% aqueous ammonia in a pressure-resistant round bottom flask equipped with a reflux condenser, and added so that 100 mL of pure water and a sodium hydroxide concentration were 0.1 mol / L. The set temperature was heated to 50 ° C., and ammonia gas from the reflux condenser was absorbed in 50 mL of a 0.1 mol / L sulfuric acid aqueous solution while reducing the pressure to -50 mmHg. When the amount of ammonia in the sulfuric acid aqueous solution was analyzed by indophenol blue absorptiometry, it was 2.6 g, and 90% or more of ammonia could be recovered. From this, it was found that in the case of the silver ammonia solution under the above conditions, ammonia can be recovered efficiently and safely using the ammonia stripping method.
［比較例１］
２８％アンモニア水１ｇに、塩化銀４６ｍｇおよび酸化銀１３ｍｇを溶解して全塩素のモル濃度を全銀のモル濃度で除した値が０.７５の銀アンモニア溶液を作製した。この銀アンモニア溶液を常温で乾燥して得た残留物に対して実施例１と同様に着火試験を行ったところ、雷銀の生成が部分的に認められ、この銀アンモニア溶液を加熱すると爆発等の危険性があることがわかった。よって、以降のアンモニア回収試験は行わなかった。
[Comparative Example 1]
A silver ammonia solution having a value of 0.75 obtained by dissolving 46 mg of silver chloride and 13 mg of silver oxide in 1 g of 28% ammonia water and dividing the molar concentration of total chlorine by the molar concentration of total silver was prepared. When an ignition test was performed on the residue obtained by drying this silver ammonia solution at room temperature in the same manner as in Example 1, the formation of thunder silver was partially observed. I found out that there was a risk. Therefore, the subsequent ammonia recovery test was not performed.
［比較例２］
２８％アンモニア水１ｇに、塩化銀６０ｍｇを溶解して全塩素のモル濃度を全銀のモル濃度で除した値が１.００の銀アンモニア溶液を作製した。この銀アンモニア溶液に更に水酸化ナトリウムを０.１ｍｏｌ／Ｌとなるように添加し、６０℃に加熱して得た残留物に対して実施例１と同様に着火試験を行ったところ、雷銀の生成が認められ、この銀アンモニア溶液を加熱すると爆発等の危険性があることがわかった。よって、以降のアンモニア回収試験は行わなかった。
[Comparative Example 2]
A silver ammonia solution having a value of 1.00 obtained by dissolving 60 mg of silver chloride in 1 g of 28% ammonia water and dividing the molar concentration of total chlorine by the molar concentration of total silver was prepared. To this silver ammonia solution, sodium hydroxide was further added at 0.1 mol / L, and the residue obtained by heating to 60 ° C. was subjected to an ignition test in the same manner as in Example 1. It was found that when this silver ammonia solution was heated, there was a risk of explosion and the like. Therefore, the subsequent ammonia recovery test was not performed.
［比較例３］
２８％アンモニア水１ｇに、塩化銀６０ｍｇを溶解して全塩素のモル濃度を全銀のモル濃度で除した値が１.００の銀アンモニア溶液を作製した。この銀アンモニア溶液に更に水酸化ナトリウムを０.２ｍｏｌ／Ｌとなるように添加し、５０℃に加熱して得た残留物に対して実施例１と同様に着火試験を行ったところ、雷銀の生成が認められ、この銀アンモニア溶液を加熱すると爆発等の危険性があることがわかった。よって、以降のアンモニア回収試験は行わなかった。
[Comparative Example 3]
A silver ammonia solution having a value of 1.00 obtained by dissolving 60 mg of silver chloride in 1 g of 28% ammonia water and dividing the molar concentration of total chlorine by the molar concentration of total silver was prepared. To this silver ammonia solution, sodium hydroxide was further added at 0.2 mol / L, and the residue obtained by heating to 50 ° C. was subjected to an ignition test in the same manner as in Example 1. It was found that when this silver ammonia solution was heated, there was a risk of explosion and the like. Therefore, the subsequent ammonia recovery test was not performed.
［比較例４］
２８％アンモニア水１ｇに、塩化銀６０ｍｇおよび塩化ナトリウム１.４７ｍｇを溶解して塩素のモル濃度を銀のモル濃度で除した値が１.０６の銀アンモニア溶液を作製した。この銀アンモニア溶液に更に水酸化ナトリウムを０.２ｍｏｌ／Ｌとなるように添加し、１００℃に加熱して得た残留物に対して実施例１と同様に着火試験を行ったところ、雷銀の生成が認められ、この銀アンモニア溶液を加熱すると爆発等の危険性があることがわかった。よって、以降のアンモニア回収試験は行わなかった。
[Comparative Example 4]
A silver ammonia solution having a value of 1.06 obtained by dissolving 60 mg of silver chloride and 1.47 mg of sodium chloride in 1 g of 28% ammonia water and dividing the molar concentration of chlorine by the molar concentration of silver was prepared. To this silver ammonia solution, sodium hydroxide was further added at 0.2 mol / L, and the residue obtained by heating to 100 ° C. was subjected to an ignition test in the same manner as in Example 1. It was found that when this silver ammonia solution was heated, there was a risk of explosion and the like. Therefore, the subsequent ammonia recovery test was not performed.
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