JP5512482B2 - Method for separating and recovering zinc from galvanizing waste liquid - Google Patents
Method for separating and recovering zinc from galvanizing waste liquid Download PDFInfo
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- JP5512482B2 JP5512482B2 JP2010228243A JP2010228243A JP5512482B2 JP 5512482 B2 JP5512482 B2 JP 5512482B2 JP 2010228243 A JP2010228243 A JP 2010228243A JP 2010228243 A JP2010228243 A JP 2010228243A JP 5512482 B2 JP5512482 B2 JP 5512482B2
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- 239000011701 zinc Substances 0.000 title claims description 68
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 title claims description 65
- 229910052725 zinc Inorganic materials 0.000 title claims description 65
- 239000007788 liquid Substances 0.000 title claims description 53
- 239000002699 waste material Substances 0.000 title claims description 38
- 238000000034 method Methods 0.000 title claims description 26
- 238000005246 galvanizing Methods 0.000 title description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 102
- 229910052742 iron Inorganic materials 0.000 claims description 58
- 238000007254 oxidation reaction Methods 0.000 claims description 22
- -1 iron ions Chemical class 0.000 claims description 20
- 230000003647 oxidation Effects 0.000 claims description 20
- 238000000926 separation method Methods 0.000 claims description 20
- 239000003513 alkali Substances 0.000 claims description 19
- 238000007747 plating Methods 0.000 claims description 13
- 238000011084 recovery Methods 0.000 claims description 12
- 239000003795 chemical substances by application Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 229960004887 ferric hydroxide Drugs 0.000 claims description 7
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 claims description 7
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 238000010979 pH adjustment Methods 0.000 claims description 5
- 239000005083 Zinc sulfide Substances 0.000 claims description 4
- 230000001590 oxidative effect Effects 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- UGZADUVQMDAIAO-UHFFFAOYSA-L zinc hydroxide Chemical compound [OH-].[OH-].[Zn+2] UGZADUVQMDAIAO-UHFFFAOYSA-L 0.000 claims description 4
- 229910021511 zinc hydroxide Inorganic materials 0.000 claims description 4
- 229940007718 zinc hydroxide Drugs 0.000 claims description 4
- 229910052984 zinc sulfide Inorganic materials 0.000 claims description 4
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 230000001376 precipitating effect Effects 0.000 claims description 2
- 238000007865 diluting Methods 0.000 claims 2
- 239000011343 solid material Substances 0.000 claims 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 15
- 239000002244 precipitate Substances 0.000 description 12
- 239000000706 filtrate Substances 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 150000003839 salts Chemical class 0.000 description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 238000006386 neutralization reaction Methods 0.000 description 5
- 235000011121 sodium hydroxide Nutrition 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- HYHCSLBZRBJJCH-UHFFFAOYSA-M sodium hydrosulfide Chemical compound [Na+].[SH-] HYHCSLBZRBJJCH-UHFFFAOYSA-M 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000000920 calcium hydroxide Substances 0.000 description 3
- 235000011116 calcium hydroxide Nutrition 0.000 description 3
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 3
- 238000010790 dilution Methods 0.000 description 3
- 239000012895 dilution Substances 0.000 description 3
- 239000008235 industrial water Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 241000894006 Bacteria Species 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000010802 sludge Substances 0.000 description 2
- 235000017557 sodium bicarbonate Nutrition 0.000 description 2
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 235000017550 sodium carbonate Nutrition 0.000 description 2
- 229910052979 sodium sulfide Inorganic materials 0.000 description 2
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 2
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 2
- 229960001763 zinc sulfate Drugs 0.000 description 2
- 229910000368 zinc sulfate Inorganic materials 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 241000233866 Fungi Species 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 235000012255 calcium oxide Nutrition 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 150000003388 sodium compounds Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000011550 stock solution Substances 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Removal Of Specific Substances (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Manufacture And Refinement Of Metals (AREA)
Description
本発明は、亜鉛めっき廃液中の亜鉛を高濃度で収率良く分離回収する方法に関する。 The present invention relates to a method for separating and recovering zinc in a galvanizing waste liquid at a high concentration and high yield.
亜鉛めっき廃液は鋼材表面への亜鉛めっきの工程で発生する高濃度亜鉛含有の廃液で国内では1〜2万トン/年発生していると想定される。液性は4〜6規定の高濃度塩酸もしくは硫酸酸性溶液中に、高濃度の亜鉛イオン及び鋼材から溶出した鉄イオンを含有する。亜鉛イオン濃度としては数%〜20wt%、鉄イオン濃度としては数%〜10wt%を含有する。亜鉛めっき廃液は強酸性で、中和には大量アルカリ剤が必要であり、また鉄は2価イオンで存在するのが特徴である。この廃液の殆どは産廃として処理され、鉄及び亜鉛は中和後、鉄及び亜鉛混合の水酸化物の脱水ケーキとして廃棄処分されている。したがって数千トン規模の亜鉛が廃棄されていると思われる。脱水ケーキの亜鉛濃度は高いので精錬原料として山元還元に供し再資源化することが必要とされているが、それを経済的に実施するためには、共存する鉄や塩の濃度を極力低減させて亜鉛濃度を40%以上に高めることが必要とされている。つまり亜鉛を鉄から効率よく分離回収する手段が必要となっている。複数の金属イオンを含む廃液からの分離回収技術としては多くの方法が知られている。例えば鉄−亜鉛系において特許文献1には、鋼板の酸洗廃液やめっき廃液など各種の重金属を含む廃液を各槽ごとに複数段階に分けてpH調整を行い、pHによる水酸化物生成傾向の差を利用し、金属種類別に水酸化物を析出させて分離回収する方法が提案されている。この中で二価鉄の酸化方法としては鉄酸化細菌を添加する方法が記載されている。特許文献2では鉄を含む複数の金属が混合する廃液において低含水率の鉄ケーキを得る方法が提案され、予め二価鉄を三価鉄に公知の方法で酸化させた後、中和剤を添加し、pH3〜5程度で水酸化鉄(三価)主体の粒子を生成させることが記載されている。特許文献3には、鉄、亜鉛等を含むめっき廃液スラッジからの金属回収のため、スラッジを酸に溶解した後、次いで液中の第1鉄(二価鉄)を過酸化水素等の酸化薬剤を使用して酸化後pH調整により、第二鉄沈殿物を得る方法が提案されている。
上記はいずれも鉄を何らかの方法で酸化して、二価鉄を三価鉄に酸化し、その後pH調整を行い、共存する他の金属成分との分離回収をはかるものである。非特許文献1には数mg/L程度の希薄濃度の二価鉄の三価鉄への空気酸化速度に与えるpHの影響を示し、酸化には中性付近が好適であることが記載されている。
The galvanizing waste liquid is a high concentration zinc-containing waste liquid generated in the galvanizing process on the steel material surface, and is assumed to be generated at 1 to 20,000 tons / year in Japan. Liquidity contains high-concentration zinc ions and iron ions eluted from steel in a 4-6 N high-concentration hydrochloric acid or sulfuric acid acidic solution. The zinc ion concentration includes several percent to 20 wt%, and the iron ion concentration includes several percent to 10 wt%. Zinc plating waste liquid is strongly acidic, requires a large amount of alkaline agent for neutralization, and is characterized by the presence of iron as divalent ions. Most of this waste liquid is treated as industrial waste, and after iron and zinc are neutralized, they are disposed of as a dehydrated cake of a mixed hydroxide of iron and zinc. Therefore, it seems that thousands of tons of zinc are discarded. Since the zinc concentration in the dehydrated cake is high, it is necessary to use it as a refining material for Yamamoto reduction and to recycle it. To achieve this economically, the concentration of coexisting iron and salt must be reduced as much as possible. Therefore, it is necessary to increase the zinc concentration to 40% or more. That is, a means for efficiently separating and recovering zinc from iron is required. Many methods are known as a separation and recovery technique from a waste liquid containing a plurality of metal ions. For example, in an iron-zinc system, Patent Document 1 discloses that a waste liquid containing various heavy metals such as a pickling waste liquid and a plating waste liquid of a steel plate is adjusted in a plurality of stages for each tank, and a hydroxide generation tendency due to pH. A method has been proposed in which the difference is used to deposit and separate a hydroxide for each metal type. Among these, as a method for oxidizing divalent iron, a method of adding iron-oxidizing bacteria is described. Patent Document 2 proposes a method of obtaining an iron cake having a low water content in a waste liquid in which a plurality of metals including iron are mixed, and after previously oxidizing divalent iron to trivalent iron by a known method, a neutralizing agent is added. It is described that iron hydroxide (trivalent) -based particles are produced at a pH of about 3 to 5. In
In any of the above methods, iron is oxidized by some method, divalent iron is oxidized to trivalent iron, pH is adjusted thereafter, and separation and recovery from other coexisting metal components are achieved. Non-Patent Document 1 shows the effect of pH on the air oxidation rate of dilute iron with a dilute concentration of several mg / L to trivalent iron, and it is described that neutrality is suitable for oxidation. Yes.
これらの方法はいずれも金属水酸化物の形成傾向において水酸化第二鉄がpH3以上で溶解度を激減する特徴を利用したものである。
All of these methods utilize the feature that ferric hydroxide drastically reduces the solubility at
化学的酸化には薬剤添加が必要で、多くは添加する薬剤の費用が有価金属回収のクレジットを損じ、経済的プロセスとしての成立を阻む結果となり、実用に至っていない。前記特許文献1において鉄酸化細菌を用いる方法では、酸化薬剤の投入はないが鉄イオン濃度が数10〜数100mg/L程度の希薄溶液への適用であり、本発明が対象とする亜鉛めっき廃液のような高濃度の鉄イオンを含有する廃液に適用した事例はないし、塩が高濃度であるため、菌の活性度も低くなることが想定され、亜鉛めっき廃液に適用するには膨大な希釈と費用が想定され、科学的には可能であっても工業的に成立しない。本発明は、かかる事情に鑑みてなされたものであって、亜鉛めっき廃液中の亜鉛を安価に効率よく鉄と分離し、経済的に再資源化可能な亜鉛濃度40%以上の高濃度亜鉛ケーキを製造する方法を提供することを目的としている。 Chemical oxidation requires the addition of chemicals. In many cases, the cost of the chemicals to be added impairs the credits for recovering valuable metals and prevents the establishment of an economic process. The method using iron-oxidizing bacteria in Patent Document 1 is applied to a dilute solution having an iron ion concentration of several tens to several hundreds mg / L, although no oxidizing agent is added. There are no examples of application to waste liquids that contain high concentrations of iron ions, such as the high concentration of salt, and it is assumed that the activity of the fungus will be low. However, it is scientifically possible but not industrially feasible. The present invention has been made in view of such circumstances, and is capable of separating zinc from galvanizing waste liquid at low cost and efficiently from iron, and economically recycling the high concentration zinc cake having a zinc concentration of 40% or more. It aims to provide a method of manufacturing.
本発明は、上記課題を解決するべく、なされたものであり、亜鉛めっき廃液中の鉄と亜鉛のモル量の和に対して所定量のアルカリを添加し、特定のpHに調整した後、空気を吹込むことにより、2価鉄イオンを3価鉄イオンに酸化するとともに、水酸化第二鉄を析出させ、溶解している亜鉛と分離した後、次いで再度pH調整し、亜鉛を析出させることにより、亜鉛ケーキを有償譲渡可能な高濃度亜鉛含有組成物又は、山元還元に供し得る有価物として回収できることを見出し、本発明を完成したものである。 The present invention has been made in order to solve the above-described problems, and after adding a predetermined amount of alkali to the sum of the molar amounts of iron and zinc in the galvanizing waste liquid, adjusting the pH to a specific value, air Oxidize divalent iron ions to trivalent iron ions, precipitate ferric hydroxide, separate from dissolved zinc, and then adjust pH again to precipitate zinc. Thus, the present inventors have found that the zinc cake can be recovered as a high-concentration zinc-containing composition that can be transferred for a fee or a valuable material that can be used for Yamamoto reduction.
すなわち、本発明は、高濃度亜鉛脱水ケーキを工業的に製造するために同廃液から鉄、及び塩類(塩素イオン、硫酸イオン塩)を除去する方法を提供する。本発明の処理フローでは、まず前処理として廃液を2〜6倍程度に希釈する。これは酸の中和時に生成する高濃度塩の低減に必要となる。次に同液を苛性ソーダ、ないし消石灰によりpHを4.5〜5.5に調整するとともに液中に空気を吹き込み二価鉄を三価鉄に酸化し、同時に水酸化第二鉄として析出させ、充分酸化が進行したことを確認した後にろ過分離する。最終的には水酸価鉄を濾過分離した後の濾液中にアルカリを加えて亜鉛を水酸化亜鉛として沈殿分離し、脱水機にて亜鉛ケーキとして回収する。脱水ケーキ回収時には中間でケーキの水洗浄を行うことで、塩の除去、亜鉛ケーキの高濃度化が可能となる。 That is, the present invention provides a method for removing iron and salts (chlorine ions and sulfate ions) from the waste liquid in order to industrially produce a high-concentration zinc dehydrated cake. In the processing flow of the present invention, the waste liquid is first diluted about 2 to 6 times as a pretreatment. This is necessary to reduce the high-concentration salt produced during the neutralization of the acid. Next, the pH of the same liquid is adjusted to 4.5 to 5.5 with caustic soda or slaked lime, and air is blown into the liquid to oxidize divalent iron to trivalent iron, and at the same time, precipitate as ferric hydroxide. After confirming that the oxidation has progressed sufficiently, it is separated by filtration. Finally, alkali is added to the filtrate after separation of the iron hydroxide value by filtration, and zinc is precipitated and separated as zinc hydroxide and recovered as a zinc cake by a dehydrator. When the dehydrated cake is recovered, the cake is washed with water in the middle to remove salt and to increase the concentration of the zinc cake.
本発明によれば低コスト、高回収率で亜鉛めっき液中の亜鉛を再資源化できる。また、亜鉛めっき廃液に限定されず、鉄と亜鉛を含有する廃液からの鉄あるいは亜鉛の分離に利用することが可能である。 According to the present invention, zinc in the zinc plating solution can be recycled at low cost and high recovery rate. Moreover, it is not limited to a zinc plating waste liquid, It can utilize for the separation of iron or zinc from the waste liquid containing iron and zinc.
本発明が適用される亜鉛めっき廃液は、鉄板、鋼板、その他各種の鉄鋼材を、電解めっき、溶融めっき等で亜鉛めっきした際に生じるめっき液、めっき工程の後処理や、洗浄工程で生じる廃液であり、1〜7規定程度、通常4〜6規定程度の塩酸、硫酸等の鉱酸中に亜鉛イオンを10,000mg/L以上、好ましくは50,000mg/L以上、より好ましくは100,000mg/L以上、2価の鉄イオンを3,000mg/L以上、特に10,000mg/L以上含むものである。亜鉛イオンの上限は特に制限されないが、通常200,000mg/L以下、多くは150,000mg/L以下である。また、2価の鉄イオンの上限も特に制限されないが、通常100,000mg/L以下、多くは60,000mg/L以下である。 The galvanizing waste liquid to which the present invention is applied is a plating liquid produced when galvanizing iron plate, steel sheet, and other various steel materials by electrolytic plating, hot dipping, etc., waste liquid produced in the post-treatment of the plating process and the washing process. In a mineral acid such as hydrochloric acid or sulfuric acid of about 1 to 7 N, usually about 4 to 6 N, zinc ion is 10,000 mg / L or more, preferably 50,000 mg / L or more, more preferably 100,000 mg. / L or more It contains 3,000 mg / L or more, especially 10,000 mg / L or more of divalent iron ions. Although the upper limit of zinc ion is not particularly limited, it is usually 200,000 mg / L or less, and most is 150,000 mg / L or less. The upper limit of the divalent iron ion is not particularly limited, but is usually 100,000 mg / L or less, and most is 60,000 mg / L or less.
この亜鉛めっき廃液に水を加えて、必要により撹拌しながら、2〜6倍程度、好ましくは3〜5倍程度に希釈する。亜鉛めっき廃液の希釈は亜鉛ケーキの品位を向上させる。脱水ケーキ中の水分に付随する塩分が低下するためである。廃液中の高濃度の酸の中和の結果として存在する塩濃度を低減するため、2〜6倍程度に希釈する。希釈度を上げすぎると品位は向上するが処理のボリュームが大きくなり、能率が低下する。 Water is added to this galvanizing waste liquid, and the mixture is diluted to about 2 to 6 times, preferably about 3 to 5 times with stirring as necessary. Dilution of galvanizing waste liquid improves the quality of the zinc cake. It is because the salt content accompanying the water | moisture content in a dewatering cake falls. In order to reduce the salt concentration present as a result of neutralization of the high concentration acid in the waste liquid, it is diluted to about 2 to 6 times. If the degree of dilution is increased too much, the quality will be improved, but the processing volume will be increased and the efficiency will be reduced.
次いで、この希釈廃液にアルカリを添加してpH4.5〜5.5に調整するとともに空気を吹き込み、2価の鉄イオンを3価の鉄イオンに酸化する。空気酸化のpH条件は4.5〜5.5好ましくは4.6〜5.4付近の比較的狭い範囲が好ましい。低濃度域での二価鉄の空気酸化についてはpH依存性が大きく、中性域が好ましいことが知られている(非特許文献1)。しかしながら、本発明が対象とする亜鉛めっき廃液の場合は鉄、亜鉛ともに高濃度であるため、pH6以上では、二価鉄の酸化は進行するものの、水酸化第二鉄の沈降に伴い亜鉛が共沈し、亜鉛の回収率が低下してしまう。また、pHが4以下では二価鉄の酸化が進行せず、二価鉄イオンが液中に残留し、亜鉛析出の際に同時に析出するため回収亜鉛の濃度を低下させてしまう。二価鉄の酸化速度と亜鉛回収率とを考慮すると、pHには最適域が存在し5付近であることを見出した(図2)。pHの調整に用いるアルカリの種類は問わないが、安価で大量に入手できるものがよく、水酸化ナトリウム、炭酸水素ナトリウム、炭酸ナトリウム、酸化カルシウム、水酸化カルシウム等を例示すことができる。なお、空気酸化反応の進行に伴いpHは低下し、低下に伴い酸化反応速度も低下するので酸化時においては液のpHを監視しながら中和用アルカリを連続的あるいは断続的に投入してpH4.5〜5.5付近を維持する方が良い。酸化時間はpHが定まれば経験的に決まるが、実操業においては反応中の液の溶解性鉄の含有量を開始時の20%以下、好ましくは10%以下になるまで行うのがよい。ここで、溶解性鉄とは、反応液を0.45μmフィルターでろ過して得られたろ液中の鉄であり、ろ液を原子吸光分析装置もしくはICP発光分光分析装置で測定した値を溶解性鉄と定義する。
Next, an alkali is added to the diluted waste liquid to adjust to pH 4.5 to 5.5 and air is blown to oxidize divalent iron ions to trivalent iron ions. The pH conditions for air oxidation are preferably within a relatively narrow range of 4.5 to 5.5, preferably 4.6 to 5.4. It is known that the air oxidation of divalent iron in a low concentration range has a large pH dependence and a neutral range is preferable (Non-patent Document 1). However, in the case of the galvanizing waste solution targeted by the present invention, both iron and zinc are at high concentrations. Therefore, at
この空気酸化により、鉄は水酸化第二鉄として沈殿する。析出物の分離手段は、特に限定されず、各種の重力濾過機、加圧濾過機、真空濾過機の外、遠心分離機も利用できる。 By this air oxidation, iron precipitates as ferric hydroxide. The separation means for the precipitate is not particularly limited, and various gravity filters, pressure filters, vacuum filters, and centrifuges can also be used.
分離したケーキは、鉄を高濃度で含有するため、山元にて電気抵抗式溶解炉などに投入することで、金属鉄として回収するとともに、わずかに含有する亜鉛はダストとして回収することができる。 Since the separated cake contains iron at a high concentration, it can be recovered as metallic iron by adding it to an electric resistance melting furnace or the like at the base of the mountain, and the slightly contained zinc can be recovered as dust.
空気酸化終了後、固液分離した濾液は、次に、アルカリを添加し、pH9.5〜11程度、好ましくは10〜10.5程度にして亜鉛を水酸化物として沈殿させる。アルカリの添加は、pHを確認しながら一度に投入しても、沈殿の生成状況を確認しながら数回に分けて投入しても良い。いずれの場合においても、最終的に前記pH範囲内となるようにアルカリ添加量を調整する。pH調整に用いるアルカリは、このようなpHにすることができるものであればよいが、安価で入手が容易な点で水酸化ナトリウム、炭酸水素ナトリウム、炭酸ナトリウム等のナトリウム化合物が望ましい。水酸化カルシウムによる中和の場合は回収した亜鉛ケーキの含有量を低下する。また、水酸化物として沈殿させる方法以外に、硫化剤を添加して硫化物として回収することもできる。この場合、添加する硫化剤としては硫化ナトリウム、硫化水素ナトリウム等のナトリウム硫化物が好ましい。硫化水素ナトリウムを加える場合は、硫化亜鉛生成の際にpHが低下するため、上記アルカリと併用する。この場合、硫化剤の添加条件としては、上記のアルカリによる中和の後半において添加する方が好ましい。硫化亜鉛生成に伴うpH低下によって、硫化水素ナトリウム添加時に硫化水素ガスが発生しやすくなり、作業員に対して危険が及ぶ可能性があるためである。硫化剤の添加開始時期は、具体的には前記アルカリを加えて反応液中のpHが5〜6以上になった時点とする。硫化剤の添加量は、残存する溶解亜鉛つまり未反応亜鉛の量に対しS当量で1〜1.2倍当量(モル比)程度が適当である。ここで、溶解性亜鉛とは、反応液を0.45μmフィルターでろ過して得られたろ液中の亜鉛であり、ろ液を原子吸光分析装置もしくはICP発光分光分析装置で測定した値を溶解性亜鉛と定義する。硫化剤添加後もアルカリの添加を続ける場合には、硫化剤とアルカリの合計量で残存する溶解亜鉛の量の1〜1.2倍当量(モル比)程度が適当である。アルカリや硫化剤を必要量添加してから、30分〜1時間程度撹拌してから沈殿物を分離する。この際高分子凝集剤を添加すると分離を良好に進めることができるが、必ずしも必要ではない。 After completion of air oxidation, the filtrate separated into solid and liquid is then added with alkali to adjust the pH to about 9.5 to 11, preferably about 10 to 10.5, and precipitate zinc as a hydroxide. The alkali may be added all at once while confirming the pH, or may be added several times while confirming the formation state of the precipitate. In either case, the amount of alkali added is adjusted so that it finally falls within the pH range. The alkali used for pH adjustment is not particularly limited as long as the pH can be adjusted to this value, but sodium compounds such as sodium hydroxide, sodium hydrogen carbonate, sodium carbonate and the like are desirable because they are inexpensive and easily available. In the case of neutralization with calcium hydroxide, the content of the recovered zinc cake is reduced. In addition to the method of precipitating as a hydroxide, a sulfurizing agent can be added and recovered as a sulfide. In this case, sodium sulfide such as sodium sulfide or sodium hydrogen sulfide is preferable as the sulfurizing agent to be added. When sodium hydrogen sulfide is added, the pH is lowered during the formation of zinc sulfide, so it is used in combination with the alkali. In this case, the addition condition of the sulfurizing agent is preferably added in the latter half of the neutralization with the alkali. This is because, due to the decrease in pH associated with the formation of zinc sulfide, hydrogen sulfide gas is likely to be generated when sodium hydrogen sulfide is added, and there is a possibility that it may be dangerous for workers. The addition start time of the sulfiding agent is specifically the time when the pH in the reaction solution becomes 5-6 or more by adding the alkali. The addition amount of the sulfurizing agent is suitably about 1 to 1.2 times equivalent (molar ratio) in terms of S equivalent to the amount of remaining dissolved zinc, that is, unreacted zinc. Here, the soluble zinc is zinc in the filtrate obtained by filtering the reaction solution with a 0.45 μm filter, and the value obtained by measuring the filtrate with an atomic absorption spectrometer or ICP emission spectrometer is the soluble zinc. It is defined as In the case where the addition of alkali is continued after the addition of the sulfiding agent, an equivalent (molar ratio) of 1 to 1.2 times the amount of dissolved zinc remaining in the total amount of the sulfiding agent and the alkali is appropriate. After adding a necessary amount of alkali or sulfurating agent, the mixture is stirred for about 30 minutes to 1 hour, and then the precipitate is separated. At this time, the addition of a polymer flocculant can facilitate the separation, but it is not always necessary.
沈殿物の分離手段は、鉄ケーキ同様に、特に限定されず、各種の重力濾過機、加圧濾過機、真空濾過機の外、遠心分離機も利用できる。なおこの脱水工程において亜鉛ケーキへの直接水投入による洗浄操作は前述したメッキ原液の希釈と同様にケーキ中の塩分を低減できるので、亜鉛ケーキの純度向上には有効である。 The means for separating the precipitate is not particularly limited as in the case of the iron cake, and various gravity filters, pressure filters, vacuum filters, and centrifuges can also be used. In this dehydration step, the washing operation by directly adding water to the zinc cake can reduce the salt content in the cake in the same manner as the dilution of the plating stock solution described above, and is therefore effective in improving the purity of the zinc cake.
分離したケーキは、亜鉛を40重量%以上と高濃度に含有しており、山元にて公知の亜鉛回収プロセス、例えば、ばい焼して酸化亜鉛として更に精製した後、硫酸に溶解して硫酸亜鉛溶液とし、硫酸亜鉛溶液から電解によって金属亜鉛を得るプロセスなどに適用することが可能である。 The separated cake contains zinc in a high concentration of 40% by weight or more. A zinc recovery process known in Yamamoto, for example, roasted and further purified as zinc oxide, dissolved in sulfuric acid and dissolved in zinc sulfate. It can be applied to a process of obtaining metallic zinc from a zinc sulfate solution by electrolysis.
固液分離した濾液は、必要により、さらに浄化して放流し、あるいは工業用水等として再利用できる。浄化方法としては、pH調整後、沈殿物除去を行う。再利用時に求められる水質によっては前記浄化方法に、逆浸透膜法などを組み合わせることができる。 The solid-liquid separated filtrate can be further purified and discharged as needed, or reused as industrial water or the like. As a purification method, the precipitate is removed after pH adjustment. Depending on the water quality required at the time of reuse, the purification method can be combined with a reverse osmosis membrane method or the like.
Zn2+濃度96,000mg/L、Fe2+濃度27,000mg/Lの亜鉛めっき廃液10Lを工業用水で3倍に希釈して、Zn2+濃度32,000mg/L、Fe2+9,000mg/Lの希釈廃液を得た。この希釈廃液を200mlづつに分け、それぞれに表1に記載のアルカリ水溶液を添加して表1のpHに保ちながら空気を吹き込んで空気酸化を行った。尚、従来例1においては、水酸化カルシウム水溶液を一度に加えた。 A zinc plating waste solution 10L having a Zn 2+ concentration of 96,000 mg / L and an Fe 2+ concentration of 27,000 mg / L was diluted three-fold with industrial water to obtain a Zn 2+ concentration of 32,000 mg / L, Fe 2+ 9, A diluted waste liquid of 000 mg / L was obtained. The diluted waste solution was divided into 200 ml units, and each of the alkaline aqueous solutions listed in Table 1 was added thereto, and air oxidation was performed by blowing air while maintaining the pH in Table 1. In Conventional Example 1, an aqueous calcium hydroxide solution was added at once.
反応終了後、1μmフィルタでろ過し回収したろ液量と鉄と亜鉛の濃度を測定した後、回収したろ液に水酸化ナトリウムを加えて沈殿を生成し、1μmフィルタでろ過し、回収したケーキの亜鉛と鉄の濃度を表2に示す。 After completion of the reaction, the amount of filtrate collected by filtration through a 1 μm filter and the concentration of iron and zinc were measured, sodium hydroxide was added to the collected filtrate to form a precipitate, filtered through a 1 μm filter, and the recovered cake Table 2 shows the concentrations of zinc and iron.
本発明により、亜鉛めっき廃液から亜鉛を高い純度で回収して再利用でき、廃液の処理負担を軽減できるので亜鉛めっき廃液の処理に広く利用できる。 According to the present invention, zinc can be recovered from zinc plating waste liquor with high purity and reused, and the processing load of the waste liquor can be reduced, so that it can be widely used for treatment of zinc plating waste liquor.
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R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |