JP4999786B2 - Method for evaluating heavy metal insolubilization performance of magnesium oxide - Google Patents
Method for evaluating heavy metal insolubilization performance of magnesium oxide Download PDFInfo
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- JP4999786B2 JP4999786B2 JP2008164020A JP2008164020A JP4999786B2 JP 4999786 B2 JP4999786 B2 JP 4999786B2 JP 2008164020 A JP2008164020 A JP 2008164020A JP 2008164020 A JP2008164020 A JP 2008164020A JP 4999786 B2 JP4999786 B2 JP 4999786B2
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- magnesium oxide
- hexavalent chromium
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims description 212
- 239000000395 magnesium oxide Substances 0.000 title claims description 112
- 229910001385 heavy metal Inorganic materials 0.000 title claims description 66
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims description 18
- 238000000034 method Methods 0.000 title claims description 17
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims description 89
- 238000011156 evaluation Methods 0.000 claims description 39
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 35
- 150000001875 compounds Chemical class 0.000 claims description 34
- 239000007788 liquid Substances 0.000 claims description 31
- 239000002002 slurry Substances 0.000 claims description 28
- 239000011651 chromium Substances 0.000 claims description 20
- 229910001430 chromium ion Inorganic materials 0.000 claims description 20
- 239000002904 solvent Substances 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 17
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- 238000000926 separation method Methods 0.000 claims description 11
- 229910052804 chromium Inorganic materials 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 8
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 7
- 239000000347 magnesium hydroxide Substances 0.000 claims description 7
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 7
- 150000002500 ions Chemical class 0.000 claims description 5
- 239000000460 chlorine Substances 0.000 claims description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 3
- 229910052801 chlorine Inorganic materials 0.000 claims description 3
- 125000001309 chloro group Chemical group Cl* 0.000 claims description 3
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 2
- 229940035427 chromium oxide Drugs 0.000 claims description 2
- 235000012245 magnesium oxide Nutrition 0.000 description 100
- 239000002689 soil Substances 0.000 description 29
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 20
- 238000010828 elution Methods 0.000 description 15
- 238000002474 experimental method Methods 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- 239000000126 substance Substances 0.000 description 11
- 238000010304 firing Methods 0.000 description 9
- 239000003638 chemical reducing agent Substances 0.000 description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052793 cadmium Inorganic materials 0.000 description 5
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 4
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 229910052785 arsenic Inorganic materials 0.000 description 4
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 4
- 239000004927 clay Substances 0.000 description 4
- 229910052731 fluorine Inorganic materials 0.000 description 4
- 239000011737 fluorine Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 3
- 239000001095 magnesium carbonate Substances 0.000 description 3
- 235000014380 magnesium carbonate Nutrition 0.000 description 3
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000012086 standard solution Substances 0.000 description 3
- 239000005909 Kieselgur Substances 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 2
- 229910021536 Zeolite Inorganic materials 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 2
- 239000010440 gypsum Substances 0.000 description 2
- 229910052602 gypsum Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- LEHBURLTIWGHEM-UHFFFAOYSA-N pyridinium chlorochromate Chemical compound [O-][Cr](Cl)(=O)=O.C1=CC=[NH+]C=C1 LEHBURLTIWGHEM-UHFFFAOYSA-N 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- QLOKJRIVRGCVIM-UHFFFAOYSA-N 1-[(4-methylsulfanylphenyl)methyl]piperazine Chemical compound C1=CC(SC)=CC=C1CN1CCNCC1 QLOKJRIVRGCVIM-UHFFFAOYSA-N 0.000 description 1
- PMJNEQWWZRSFCE-UHFFFAOYSA-N 3-ethoxy-3-oxo-2-(thiophen-2-ylmethyl)propanoic acid Chemical compound CCOC(=O)C(C(O)=O)CC1=CC=CS1 PMJNEQWWZRSFCE-UHFFFAOYSA-N 0.000 description 1
- CQTZDAHOKOZXSR-UHFFFAOYSA-L C=CC1=CC=NC=C1.C=CC1=CC=NC=C1.O[Cr](O[Cr](O)(=O)=O)(=O)=O Chemical compound C=CC1=CC=NC=C1.C=CC1=CC=NC=C1.O[Cr](O[Cr](O)(=O)=O)(=O)=O CQTZDAHOKOZXSR-UHFFFAOYSA-L 0.000 description 1
- 229910004844 Na2B4O7.10H2O Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- LEZAZQDIYCYEIE-UHFFFAOYSA-L [Cr](=O)(=O)(O)Cl.N1=C(C=CC=C1)C1=NC=CC=C1 Chemical group [Cr](=O)(=O)(O)Cl.N1=C(C=CC=C1)C1=NC=CC=C1 LEZAZQDIYCYEIE-UHFFFAOYSA-L 0.000 description 1
- PKINRUTUIQQMLY-UHFFFAOYSA-L [Cr](=O)(=O)(O)F.N1=CC=CC=C1 Chemical compound [Cr](=O)(=O)(O)F.N1=CC=CC=C1 PKINRUTUIQQMLY-UHFFFAOYSA-L 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- JOSWYUNQBRPBDN-UHFFFAOYSA-P ammonium dichromate Chemical compound [NH4+].[NH4+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O JOSWYUNQBRPBDN-UHFFFAOYSA-P 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QFFVPLLCYGOFPU-UHFFFAOYSA-N barium chromate Chemical compound [Ba+2].[O-][Cr]([O-])(=O)=O QFFVPLLCYGOFPU-UHFFFAOYSA-N 0.000 description 1
- 229940083898 barium chromate Drugs 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- YKYOUMDCQGMQQO-UHFFFAOYSA-L cadmium dichloride Chemical compound Cl[Cd]Cl YKYOUMDCQGMQQO-UHFFFAOYSA-L 0.000 description 1
- JGIATAMCQXIDNZ-UHFFFAOYSA-N calcium sulfide Chemical compound [Ca]=S JGIATAMCQXIDNZ-UHFFFAOYSA-N 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910052570 clay Inorganic materials 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 229940077449 dichromate ion Drugs 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- CMMUKUYEPRGBFB-UHFFFAOYSA-L dichromic acid Chemical compound O[Cr](=O)(=O)O[Cr](O)(=O)=O CMMUKUYEPRGBFB-UHFFFAOYSA-L 0.000 description 1
- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- HFTNNOZFRQLFQB-UHFFFAOYSA-N ethenoxy(trimethyl)silane Chemical compound C[Si](C)(C)OC=C HFTNNOZFRQLFQB-UHFFFAOYSA-N 0.000 description 1
- UKAUYVFTDYCKQA-UHFFFAOYSA-N homoserine Chemical compound OC(=O)C(N)CCO UKAUYVFTDYCKQA-UHFFFAOYSA-N 0.000 description 1
- OPMAIHGGKQJERG-UHFFFAOYSA-L hydroxy-(hydroxy(dioxo)chromio)oxy-dioxochromium;1h-imidazole Chemical compound C1=CNC=N1.C1=CNC=N1.O[Cr](=O)(=O)O[Cr](O)(=O)=O OPMAIHGGKQJERG-UHFFFAOYSA-L 0.000 description 1
- RCBVKBFIWMOMHF-UHFFFAOYSA-L hydroxy-(hydroxy(dioxo)chromio)oxy-dioxochromium;pyridine Chemical compound C1=CC=NC=C1.C1=CC=NC=C1.O[Cr](=O)(=O)O[Cr](O)(=O)=O RCBVKBFIWMOMHF-UHFFFAOYSA-L 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- MOUPNEIJQCETIW-UHFFFAOYSA-N lead chromate Chemical compound [Pb+2].[O-][Cr]([O-])(=O)=O MOUPNEIJQCETIW-UHFFFAOYSA-N 0.000 description 1
- RLJMLMKIBZAXJO-UHFFFAOYSA-N lead nitrate Chemical compound [O-][N+](=O)O[Pb]O[N+]([O-])=O RLJMLMKIBZAXJO-UHFFFAOYSA-N 0.000 description 1
- 229940031958 magnesium carbonate hydroxide Drugs 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012113 quantitative test Methods 0.000 description 1
- 239000011044 quartzite Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- PTLRDCMBXHILCL-UHFFFAOYSA-M sodium arsenite Chemical compound [Na+].[O-][As]=O PTLRDCMBXHILCL-UHFFFAOYSA-M 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000003828 vacuum filtration Methods 0.000 description 1
- NDKWCCLKSWNDBG-UHFFFAOYSA-N zinc;dioxido(dioxo)chromium Chemical compound [Zn+2].[O-][Cr]([O-])(=O)=O NDKWCCLKSWNDBG-UHFFFAOYSA-N 0.000 description 1
Description
本発明は、汚染土壌に含まれている鉛、カドミウム、６価クロム等の重金属を不溶化するために用いられる酸化マグネシウムの当該重金属不溶化性能を評価するための方法に関する。 The present invention relates to a method for evaluating the heavy metal insolubilization performance of magnesium oxide used for insolubilizing heavy metals such as lead, cadmium and hexavalent chromium contained in contaminated soil.
酸化マグネシウムを土壌固化剤や重金属溶出低減剤の材料として用いることは、従来から知られている。
例えば、酸化マグネシウムおよび／または硫酸マグネシウム、または、酸化マグネシウムおよび／または硫酸マグネシウム含有物からなる土壌固化剤が提案されている（特許文献１）。
また、所定深度の重金属等によって汚染されている汚染土壌を泥土状となし、前記泥土状汚染土壌中に、所定の水と所定量の酸化マグネシウムを混合した酸化マグネシウムを主成分とする土壌固化剤を注入して、該固化剤と前記土壌とを混合せしめ、注入した前記固化剤の酸化マグネシウムが反応して前記土壌を固化して、前記重金属を隣接土壌への溶出を防止せしめることを特徴とする汚染土壌の重金属等溶出防止手段が、提案されている（特許文献２）。
For example, a soil solidifying agent composed of magnesium oxide and / or magnesium sulfate or a magnesium oxide and / or magnesium sulfate-containing material has been proposed (Patent Document 1).
Moreover, the soil solidification agent which makes the contaminated soil contaminated with the heavy metal etc. of predetermined depth in the shape of mud, and which has magnesium oxide as a main component which mixed the predetermined water and the predetermined amount of magnesium oxide in the mud-like contaminated soil. The solidifying agent and the soil are mixed, and the magnesium oxide of the injected solidifying agent reacts to solidify the soil, thereby preventing the heavy metal from being eluted into the adjacent soil. Means for preventing elution of heavy metals from contaminated soil has been proposed (Patent Document 2).
酸化マグネシウムとしては、一般に、炭酸マグネシウムや水酸化マグネシウムを焼成したものが用いられる。この場合、酸化マグネシウムの性状は、焼成温度、原料の種類、原料に含まれる不純物の種類及び量等によって変動する。
本発明者が焼成温度を変化させて種々の酸化マグネシウムを製造して得た知見によると、８００〜１１００℃の温度で焼成した場合であっても、得られる酸化マグシウムの中には、重金属不溶化性能に劣るものがある。そのため、重金属溶出低減剤としての酸化マグネシウムの品質の安定性を高めるためには、このような重金属不溶化性能に劣る酸化マグネシウムを見つけて、製品化前に排除する必要がある。その際、重金属不溶化性能を簡易にかつ短時間でしかも汚染土壌を実際に用いずに評価することができれば、好都合である。
この点、前記の特許文献１、２には、酸化マグネシウムを使用することは記載されているものの、重金属溶出低減等の性能の観点から、酸化マグネシウムの品質の良否を評価して選別することは、全く記載されていない。
そこで、本発明は、汚染土壌の固化及び汚染土壌中の重金属の溶出低減剤として用いられる各種の酸化マグネシウムの重金属不溶化性能を、汚染土壌を用いずに簡易にかつ短時間で評価することのできる方法を提供することを目的とする。
In general, magnesium oxide obtained by firing magnesium carbonate or magnesium hydroxide is used. In this case, the properties of magnesium oxide vary depending on the firing temperature, the type of raw material, the type and amount of impurities contained in the raw material, and the like.
According to the knowledge obtained by the inventors of the present invention by producing various magnesium oxides by changing the firing temperature, even in the case of firing at a temperature of 800 to 1100 ° C., the obtained magnesium oxide is insoluble in heavy metals. Some are inferior in performance. Therefore, in order to improve the stability of the quality of magnesium oxide as a heavy metal elution reducing agent, it is necessary to find magnesium oxide inferior to such heavy metal insolubilization performance and eliminate it before commercialization. At that time, it would be advantageous if the heavy metal insolubilization performance could be evaluated easily and in a short time without actually using contaminated soil.
In this respect, although the use of magnesium oxide is described in Patent Documents 1 and 2, the quality of magnesium oxide is evaluated and selected from the viewpoint of performance such as reduction of heavy metal elution. It is not described at all.
Therefore, the present invention can easily and quickly evaluate the heavy metal insolubilization performance of various magnesium oxides used as a solidification of contaminated soil and an elution reducing agent for heavy metals in the contaminated soil without using contaminated soil. It aims to provide a method.
本発明者は、上記課題を解決するために鋭意検討した結果、６価クロム含有化合物と酸化マグネシウムを、水を溶媒として混合して撹拌し、スラリーを得た後、このスラリーを固液分離して得られる液分中に存在する６価クロムイオン濃度を測定することによって、酸化マグネシウムに由来する水酸化マグネシウムと共に固体分を構成する不溶化した６価クロムを定量することができ、この不溶化した６価クロムの量が多いほど、酸化マグネシウムの重金属不溶化性能が高いと評価しうることを見出し、本発明を完成した。
すなわち、本発明は、以下の［１］〜［５］を提供するものである。
［１］ （Ａ）６価クロム含有化合物と酸化マグネシウムを、水を溶媒として混合して撹拌し、スラリーを得る混合工程と、（Ｂ）得られたスラリーを固液分離して、上記６価クロム含有化合物の一部に由来する６価クロムイオンを含む液分、及び、上記６価クロム含有化合物の残部に由来する６価クロムと上記酸化マグネシウムに由来する水酸化マグネシウムとを含む固体分を得る固液分離工程と、（Ｃ）得られた液分中の６価クロムイオン濃度を測定して、上記酸化マグネシウムの重金属不溶化性能を評価する評価工程とを含む酸化マグネシウムの重金属不溶化性能の評価方法であって、工程（Ａ）において、上記６価クロム含有化合物の量は、上記スラリーの溶媒である水１リットルに対して６価クロムの質量が０．７５〜１０ｍｇとなる量であり、かつ、上記酸化マグネシウムの量は、上記スラリーの溶媒である水１リットルに対して３〜１００ｇであることを特徴とする酸化マグネシウムの重金属不溶化性能の評価方法。
［２］ 工程（Ａ）における撹拌時間が、１５分間以上である前記［１］に記載の酸化マグネシウムの重金属不溶化性能の評価方法。
［３］ 工程（Ａ）のスラリーの塩素含有イオン濃度が、塩素原子に換算して、０．０３ｍｇ／リットル以下である前記［１］又は［２］に記載の酸化マグネシウムの重金属不溶化性能の評価方法。
［４］ 工程（Ａ）〜（Ｃ）に加えて、（Ｄ）工程（Ｃ）の評価結果に基いて、複数の種類の酸化マグネシウムの中から、重金属不溶化性能の高い酸化マグネシウムを選別する選別工程を含む前記［１］〜［３］のいずれかに記載の酸化マグネシウムの重金属不溶化性能の評価方法。
［５］ 工程（Ａ）において、上記６価クロム含有化合物の量は、上記スラリーの溶媒である水１リットルに対して６価クロムの質量が１．０〜２．０ｍｇとなる量であり、上記酸化マグネシウムの量は、上記スラリーの溶媒である水１リットルに対して１０〜３５ｇであり、撹拌時間は１５〜２０分間であり、かつ、工程（Ｄ）において、上記６価クロム含有化合物中の６価クロムの全量の３５質量％以上が上記固体分として回収されたことが判明した酸化マグネシウムを選別する前記［４］に記載の酸化マグネシウムの重金属不溶化性能の評価方法。
As a result of intensive studies to solve the above problems, the present inventor mixed and stirred a hexavalent chromium-containing compound and magnesium oxide using water as a solvent to obtain a slurry, which was then solid-liquid separated. By measuring the concentration of hexavalent chromium ions present in the liquid fraction obtained in this way, the insolubilized hexavalent chromium constituting the solid content together with magnesium hydroxide derived from magnesium oxide can be quantified, and this insolubilized 6 It has been found that the higher the amount of valent chromium, the higher the heavy metal insolubilization performance of magnesium oxide, and the present invention has been completed.
That is, the present invention provides the following [1] to [ 5 ].
[1] (A) A hexavalent chromium-containing compound and magnesium oxide are mixed using water as a solvent and stirred to obtain a slurry; and (B) the obtained slurry is subjected to solid-liquid separation, and the above hexavalent A liquid containing hexavalent chromium ions derived from a part of the chromium-containing compound, and a solid containing hexavalent chromium derived from the remainder of the hexavalent chromium-containing compound and magnesium hydroxide derived from the magnesium oxide. Evaluation of the heavy metal insolubilization performance of magnesium oxide , comprising: a solid-liquid separation step to be obtained; and (C) an evaluation step of measuring the hexavalent chromium ion concentration in the obtained liquid and evaluating the heavy metal insolubilization performance of the magnesium oxide. In step (A), the amount of the hexavalent chromium-containing compound is such that the mass of hexavalent chromium is from 0.75 to 10 mg with respect to 1 liter of water as the solvent of the slurry. And the amount of the magnesium oxide is 3 to 100 g with respect to 1 liter of water which is the solvent of the slurry, the method for evaluating the heavy metal insolubilization performance of magnesium oxide.
[ 2 ] The method for evaluating heavy metal insolubilization performance of magnesium oxide according to [1] , wherein the stirring time in the step (A) is 15 minutes or more.
[ 3 ] Evaluation of heavy metal insolubilization performance of magnesium oxide according to [1] or [2] above, wherein the chlorine-containing ion concentration of the slurry of step (A) is 0.03 mg / liter or less in terms of chlorine atoms. Method.
[ 4 ] In addition to steps (A) to (C), (D) selection for selecting magnesium oxide having high heavy metal insolubilization performance from a plurality of types of magnesium oxide based on the evaluation results of step (C) The evaluation method of the heavy metal insolubilization performance of magnesium oxide in any one of said [1]-[ 3 ] including a process.
[ 5 ] In the step (A), the amount of the hexavalent chromium-containing compound is such that the mass of the hexavalent chromium is 1.0 to 2.0 mg with respect to 1 liter of water as the solvent of the slurry. The amount of the magnesium oxide is 10 to 35 g with respect to 1 liter of water as the solvent of the slurry, the stirring time is 15 to 20 minutes, and in the step (D), the hexavalent chromium-containing compound [ 4 ] The method for evaluating the heavy metal insolubilization performance of magnesium oxide according to [ 4 ] above, wherein the magnesium oxide having been found to be recovered in an amount of 35% by mass or more of the total amount of hexavalent chromium of the above.
本発明の酸化マグネシウムの重金属不溶化性能の評価方法によれば、簡易にかつ短時間（例えば、１時間以内）で酸化マグネシウムの重金属不溶化性能を高精度で評価することができる。特に、工程（Ａ）において、スラリーの溶媒である水１リットル当たりの６価クロムの質量が１．０〜２．０ｍｇとなるように６価クロム含有化合物の使用量を定め、かつ、スラリーの溶媒である水１リットル当たり１０〜３５ｇとなるように酸化マグネシウムの使用量を定めれば、市販の簡易測定装置（例えば、共立理化学研究所製の「デジタルパックテスト」）を用いることによって、１０分間以内で工程（Ｃ）（評価工程）を行なうことができ、この場合、工程（Ａ）〜工程（Ｃ）の全体の所要時間を例えば、３０分間以内に短縮することができる。
また、本発明の評価方法によれば、汚染土壌を用意しなくても、微量の６価クロム含有化合物を用意するだけで、酸化マグネシウムの重金属不溶化性能を評価することができる。
According to the method for evaluating the heavy metal insolubilization performance of magnesium oxide of the present invention, the heavy metal insolubilization performance of magnesium oxide can be evaluated with high accuracy in a short time (for example, within 1 hour). In particular, in step (A), the amount of hexavalent chromium-containing compound used is determined so that the mass of hexavalent chromium per liter of water that is the solvent of the slurry is 1.0 to 2.0 mg, and If the amount of magnesium oxide used is determined to be 10 to 35 g per liter of water as a solvent, a commercially available simple measuring device (for example, “Digital Pack Test” manufactured by Kyoritsu Riken) can be used. The step (C) (evaluation step) can be performed within a minute, and in this case, the total time required for the step (A) to the step (C) can be shortened to within 30 minutes, for example.
Moreover, according to the evaluation method of this invention, even if it does not prepare contaminated soil, the heavy metal insolubilization performance of magnesium oxide can be evaluated only by preparing a trace amount hexavalent chromium containing compound.
本発明の酸化マグネシウムの重金属不溶化性能の評価方法は、（Ａ）６価クロム含有化合物と酸化マグネシウムを、水を溶媒として混合して撹拌し、スラリーを得る混合工程と、（Ｂ）得られたスラリーを固液分離して、上記６価クロム含有化合物の一部に由来する６価クロムイオンを含む液分、及び、上記６価クロム含有化合物の残部に由来する６価クロムと上記酸化マグネシウムに由来する水酸化マグネシウムとを含む固体分を得る固液分離工程と、（Ｃ）得られた液分中の６価クロムイオン濃度を測定して、上記酸化マグネシウムの重金属不溶化性能を評価する評価工程とを含む。
以下、工程（Ａ）〜工程（Ｃ）について詳述する。
The method for evaluating the heavy metal insolubilization performance of magnesium oxide according to the present invention includes (A) a mixing step of mixing a hexavalent chromium-containing compound and magnesium oxide using water as a solvent and stirring to obtain a slurry, and (B) obtained. The slurry is subjected to solid-liquid separation, and a liquid containing hexavalent chromium ions derived from a part of the hexavalent chromium-containing compound and hexavalent chromium and magnesium oxide derived from the remainder of the hexavalent chromium-containing compound are separated. A solid-liquid separation step for obtaining a solid content containing derived magnesium hydroxide, and (C) an evaluation step for measuring the hexavalent chromium ion concentration in the obtained liquid content to evaluate the heavy metal insolubilization performance of the magnesium oxide. Including.
Hereinafter, process (A)-process (C) are explained in full detail.
［工程（Ａ）；混合工程］
工程（Ａ）は、６価クロム含有化合物と酸化マグネシウムを、水を溶媒として混合して撹拌し、スラリーを得る工程である。
６価クロム含有化合物は、水中で６価クロムを含むイオン（例えば、クロム酸（ＣｒＯ4 2-）、二クロム酸（Ｃｒ2Ｏ7 2-）など）を供給し得る水溶性のものであればよい。また、６価クロム含有化合物として、本発明の効果に影響を及ぼさない他の物質との混合物を用いてもよい。６価クロム含有化合物の形態は、液体と固体のいずれでもよい。
６価クロム含有化合物の例としては、二クロム酸ナトリウム二水和物、二クロム酸ピリジニウム、フルオロクロム酸ピリジニウム、ポリ（二クロム酸４−ビニルピリジニウム）、無水クロム酸、クロム標準液（Ｃｒ−１０００）、クロム標準液（Ｃｒ−１００）、クロム酸亜鉛、クロム酸アンモニウム、クロム酸カリウム、クロム酸ナトリウム四水和物、クロム酸鉛（II）、クロム酸バリウム、クロムヘキサカルボニル、クロロクロム酸２，２’−ビピリジル、クロロクロム酸ピリジニウム、ジオキシ塩化クロム、チトリゾールクロム標準溶液、二クロム酸アンモニウム、二クロム酸イミダゾリウム、二クロム酸カリウム等が挙げられる。
[Step (A); mixing step]
Step (A) is a step of obtaining a slurry by mixing and stirring a hexavalent chromium-containing compound and magnesium oxide using water as a solvent.
The hexavalent chromium-containing compound may be a water-soluble compound capable of supplying ions containing hexavalent chromium in water (for example, chromic acid (CrO 4 2− ), dichromic acid (Cr 2 O 7 2− ), etc.). That's fine. Moreover, you may use the mixture with the other substance which does not affect the effect of this invention as a hexavalent chromium containing compound. The form of the hexavalent chromium-containing compound may be either liquid or solid.
Examples of hexavalent chromium-containing compounds include sodium dichromate dihydrate, pyridinium dichromate, pyridinium fluorochromate, poly (4-vinylpyridinium dichromate), chromic anhydride, chromium standard solution (Cr- 1000), chromium standard solution (Cr-100), zinc chromate, ammonium chromate, potassium chromate, sodium chromate tetrahydrate, lead chromate (II), barium chromate, chromium hexacarbonyl, chlorochromic acid 2,2′-bipyridyl, pyridinium chlorochromate, dioxychromium chloride, titrizole chromium standard solution, ammonium dichromate, imidazolium dichromate, potassium dichromate and the like.
６価クロム含有化合物の量は、スラリーの溶媒である水１リットルに対して、６価クロムの質量が０．７５〜１０ｍｇ、好ましくは０．９〜５ｍｇ、より好ましくは１．０〜２．０ｍｇとなる量である。該値が０．７５ｍｇ未満では、酸化マグネシウムの重金属不溶化性能の優劣にかかわらず、工程（Ｃ）における６価クロムイオン濃度の測定値が小さくなり、酸化マグネシウムの評価が困難な場合がある。該値が１０ｍｇを超えると、６価クロム含有廃棄物の量が多くなり、廃棄物の処理の負担が増大する。 The amount of the hexavalent chromium-containing compound is such that the mass of hexavalent chromium is 0.75 to 10 mg , preferably 0.9 to 5 mg, more preferably 1.0 to 2. The amount is 0 mg. If this value is less than 0.75 mg, the measured value of the hexavalent chromium ion concentration in the step (C) becomes small regardless of the superiority or inferiority of the heavy metal insolubilization performance of magnesium oxide, and it may be difficult to evaluate magnesium oxide. If the value exceeds 10 mg, the amount of hexavalent chromium-containing waste increases and the burden of waste disposal increases.
酸化マグネシウムは、例えば、炭酸マグネシウム、水酸化マグネシウム等のマグネシウム含有化合物を焼成することによって得ることができる。焼成温度は、好ましくは７５０〜９５０℃、より好ましくは８００〜９００℃である。焼成温度が７５０℃未満では、焼成時間が長くなり、酸化マグネシウムの製造効率が低下する。焼成温度が９５０℃を超えると、重金属不溶化性能が低下する傾向がある。
酸化マグネシウムの量は、スラリーの溶媒である水１リットルに対して、３〜１００ｇ、好ましくは５〜１００ｇ、より好ましくは７〜５０ｇ、特に好ましくは１０〜３５ｇとなる量である。該量が３ｇ未満では、酸化マグネシウムの重金属不溶化性能の優劣にかかわらず、工程（Ｃ）における６価クロムイオン濃度の測定値が小さ過ぎて、酸化マグネシウムの評価が困難な場合がある。該量が１００ｇを超えると、酸化マグネシウムの評価の精度が低下することがある。
本発明の評価対象物である酸化マグネシウムとしては、本発明の効果に影響を及ぼさない限りにおいて、他の物質との混合物を用いてもよい。他の物質としては、ゼオライト、珪藻土、白土、ベントナイト、乾燥粘土、炭酸カルシウム、珪石粉末、石膏等が挙げられる。他の物質の割合は、酸化マグネシウムとの合計量中、好ましくは７０質量％以下、より好ましくは５０質量％以下である。
なお、本発明の効果に影響を及ぼしうる他の物質としては、例えば、６価クロムを３価クロムに還元する物質（還元剤；例えば、硫酸鉄（II）、硫化カルシウム等）が挙げられる。
Magnesium oxide can be obtained, for example, by firing a magnesium-containing compound such as magnesium carbonate or magnesium hydroxide. The firing temperature is preferably 750 to 950 ° C, more preferably 800 to 900 ° C. When the firing temperature is less than 750 ° C., the firing time becomes longer, and the production efficiency of magnesium oxide decreases. When the firing temperature exceeds 950 ° C., the heavy metal insolubilization performance tends to decrease.
The amount of magnesium oxide, per liter of water is the solvent of the slurry, 3～100G, an amount preferably comprised 5 to 100 g, more preferably 7～50G, particularly preferably a 10～35G. If the amount is less than 3 g, the measured value of the hexavalent chromium ion concentration in the step (C) is too small regardless of superiority or inferiority of the heavy oxide insolubilization performance of magnesium oxide, and it may be difficult to evaluate magnesium oxide. If the amount exceeds 100 g, the accuracy of magnesium oxide evaluation may be reduced.
As magnesium oxide which is an evaluation object of the present invention, a mixture with other substances may be used as long as the effect of the present invention is not affected. Examples of other substances include zeolite, diatomaceous earth, white clay, bentonite, dry clay, calcium carbonate, silica stone powder, gypsum and the like. The ratio of the other substance is preferably 70% by mass or less, more preferably 50% by mass or less, in the total amount with magnesium oxide.
Examples of other substances that can affect the effects of the present invention include substances that reduce hexavalent chromium to trivalent chromium (reducing agents; for example, iron (II) sulfate, calcium sulfide, etc.).
工程（Ａ）におけるスラリーの塩素イオン濃度は、本発明の評価方法の評価の精度を高める観点から、好ましくは０．０３ｍｇ／リットル以下である。なお、本明細書中、塩素イオン濃度とは、塩化物イオン（Ｃｌ-）等の塩素含有イオンの塩素原子（Ｃｌ）に換算した濃度をいう。
スラリーの塩素イオン濃度を前記の好ましい数値範囲内とするためには、工程（Ａ）で用いる水として、蒸留水またはイオン交換水を用いればよい。水道水を用いた場合、通常、スラリー中の塩素イオン濃度は、０．０３ｍｇ／リットルを超える。
工程（Ａ）で用いる水の電気伝導度は、本発明の評価方法の評価の精度を高める観点から、好ましくは０．５μｓ／ｃｍ以下である。
６価クロム含有化合物と酸化マグネシウムを、水を溶媒として混合し撹拌する方法としては、例えば、６価クロム含有化合物と水を混合してなる水溶液と、酸化マグネシウムを混合して撹拌する方法が挙げられる。
撹拌時間の下限値は、好ましくは１５分間以上である。該値が１５分間未満では、酸化マグネシウムの評価の精度が低下することがある。
撹拌時間の上限値は、特に限定されないが、本発明の評価方法の効率性の観点から、好ましくは２時間以内、より好ましくは１時間以内、さらに好ましくは３０分間以内、特に好ましくは２０分間以内である。
The chlorine ion concentration of the slurry in the step (A) is preferably 0.03 mg / liter or less from the viewpoint of improving the accuracy of evaluation by the evaluation method of the present invention. In the present specification, the chlorine ion concentration refers to the concentration converted to chlorine atoms (Cl) of chlorine-containing ions such as chloride ions (Cl-).
In order to make the chlorine ion concentration of the slurry within the preferable numerical range, distilled water or ion-exchanged water may be used as the water used in the step (A). When tap water is used, the chlorine ion concentration in the slurry usually exceeds 0.03 mg / liter.
The electrical conductivity of water used in the step (A) is preferably 0.5 μs / cm or less from the viewpoint of increasing the accuracy of evaluation by the evaluation method of the present invention.
Examples of the method of mixing and stirring the hexavalent chromium-containing compound and magnesium oxide using water as a solvent include, for example, an aqueous solution obtained by mixing the hexavalent chromium-containing compound and water and a method of mixing and stirring the magnesium oxide. It is done.
The lower limit of the stirring time is preferably 15 minutes or more. If the value is less than 15 minutes, the accuracy of magnesium oxide evaluation may be reduced.
The upper limit of the stirring time is not particularly limited, but from the viewpoint of efficiency of the evaluation method of the present invention, it is preferably within 2 hours, more preferably within 1 hour, further preferably within 30 minutes, particularly preferably within 20 minutes. It is.
［工程（Ｂ）；固液分離工程］
工程（Ｂ）は、得られたスラリーを固液分離して、６価クロム含有化合物の一部に由来する６価クロムイオンを含む液分、及び、６価クロム含有化合物の残部に由来する６価クロムと酸化マグネシウムに由来する水酸化マグネシウムとを含む固体分を得る工程である。
固液分離の方法としては、濾過、遠心分離等が挙げられる。
固液分離手段としては、先端にフィルター（濾過手段）を装着した注射器や、減圧濾過装置や、遠心分離装置等が挙げられる。
[Step (B); Solid-liquid separation step]
In the step (B), the obtained slurry is subjected to solid-liquid separation, and the liquid component containing hexavalent chromium ions derived from a part of the hexavalent chromium-containing compound and the remainder 6 of the hexavalent chromium-containing compound are derived. This is a step of obtaining a solid content containing valent chromium and magnesium hydroxide derived from magnesium oxide.
Examples of the solid-liquid separation method include filtration and centrifugation.
Examples of the solid-liquid separation means include a syringe equipped with a filter (filtration means) at the tip, a vacuum filtration device, a centrifugal separation device, and the like.
［工程（Ｃ）；評価工程］
工程（Ｃ）は、工程（Ｂ）で得られた液分中の６価クロムイオン濃度を測定して、酸化マグネシウムの重金属不溶化性能を評価する工程である。
６価クロムイオン濃度とは、６価クロムを含むイオン（例えば、二クロム酸イオン）のクロム原子（Ｃｒ）に換算した濃度をいう。
本発明では、工程（Ａ）で酸化マグネシウムを用いずに６価クロム含有化合物のみを水中に溶解させたと仮定した場合の液分中の６価クロムイオン濃度を基準値とした場合、この基準値に対する６価クロムイオン濃度の低下の程度が、酸化マグネシウムの重金属不溶化性能と高い相関性があるものとして、酸化マグネシウムの重金属不溶化性能を評価するものである。なお、酸化マグネシウムに関し、６価クロムに対する不溶化性能が高い場合、鉛、カドミウム等の重金属に対しても不溶化性能が高いことが、本発明者の実験によって確認されている。つまり、６価クロムに対する不溶化性能と、他の重金属に対する不溶化性能とは、高い相関関係がある。本発明では、この知見に基き、６価クロムに対する不溶化性能の評価を、重金属に対する不溶化性能の評価に置き換えるものである。
本発明の評価方法を用いずに酸化マグネシウムの重金属不溶化性能を評価するためには、酸化マグネシウムと汚染土壌を混合して、所定期間（例えば、２８日）経過後に６価クロム等の重金属の溶出量の定量試験を行って、酸化マグネシウムの重金属不溶化性能を評価する必要がある。この点、本発明の評価方法では、汚染土壌が不要であり、しかも、簡易かつ迅速に評価することができる。
[Step (C); Evaluation step]
Step (C) is a step of measuring the heavy metal insolubilization performance of magnesium oxide by measuring the hexavalent chromium ion concentration in the liquid obtained in step (B).
The hexavalent chromium ion concentration means a concentration converted to a chromium atom (Cr) of an ion containing hexavalent chromium (for example, dichromate ion).
In the present invention, when it is assumed that only the hexavalent chromium-containing compound is dissolved in water without using magnesium oxide in step (A), the reference value is the hexavalent chromium ion concentration in the liquid. The degree of decrease in the hexavalent chromium ion concentration relative to the above is evaluated as being highly correlated with the heavy metal insolubilization performance of magnesium oxide. In addition, regarding the magnesium oxide, when the insolubilization performance with respect to hexavalent chromium is high, it has been confirmed by experiments of the present inventor that the insolubilization performance is high with respect to heavy metals such as lead and cadmium. That is, the insolubilization performance with respect to hexavalent chromium and the insolubilization performance with respect to other heavy metals have a high correlation. In the present invention, based on this finding, evaluation of insolubilization performance for hexavalent chromium is replaced with evaluation of insolubilization performance for heavy metals.
In order to evaluate the heavy metal insolubilization performance of magnesium oxide without using the evaluation method of the present invention, magnesium oxide and contaminated soil are mixed and elution of heavy metals such as hexavalent chromium after a predetermined period (for example, 28 days) has passed. It is necessary to evaluate the heavy metal insolubilization performance of magnesium oxide by conducting a quantitative test of the amount. In this respect, the evaluation method of the present invention does not require contaminated soil, and can be easily and quickly evaluated.
［工程（Ｄ）；選別工程］
本発明の評価方法は、工程（Ａ）〜（Ｃ）に加えて、（Ｄ）工程（Ｃ）の評価結果に基いて、複数の種類の酸化マグネシウムの中から、重金属不溶化性能の高い酸化マグネシウムを、重金属溶出低減剤等としての使用に適する酸化マグネシウムとして選別する選別工程、を含むことができる。
工程（Ｄ）を含む場合における本発明の評価方法の好適な一例として、以下の（ａ）〜（ｄ）の条件をすべて満たすものが挙げられる。
（ａ）工程（Ａ）における６価クロム含有化合物の量は、スラリーの溶媒である水１リットルに対して６価クロムの質量が１．０〜２．０ｍｇとなる量である。
（ｂ）工程（Ａ）における酸化マグネシウムの量は、スラリーの溶媒である水１リットルに対して１０〜３５ｇである。
（ｃ）工程（Ａ）における撹拌時間は、１５〜２０分間である。
（ｄ）工程（Ｄ）は、６価クロム含有化合物中の６価クロムの全量の３５質量％以上が固体分として回収されたことが判明した酸化マグネシウムを選別するものである。
重金属溶出低減剤は、酸化マグネシウム以外に他の物質（例えば、ゼオライト、珪藻土、白土、ベントナイト、乾燥粘土、炭酸カルシウム、珪石粉末、石膏等）を含むことができる。この場合、選別した酸化マグネシウムと、他の物質を混合して、重金属溶出低減剤を調製する。
重金属溶出低減剤の添加量は、汚染土壌に含まれている重金属の種類、量等によっても異なるが、通常、汚染土壌１ｍ３に対して、好ましくは１０ｋｇ以上、より好ましくは５０ｋｇ以上である。添加量の上限は、特に限定されないが、通常、汚染土壌１ｍ３に対して３００ｋｇである。
[Step (D); selection step]
In addition to the steps (A) to (C), the evaluation method of the present invention is based on the evaluation result of the step (C) (D) Magnesium oxide having high heavy metal insolubilization performance from among a plurality of types of magnesium oxide. Can be included as a magnesium oxide suitable for use as a heavy metal elution reducing agent or the like.
As a suitable example of the evaluation method of the present invention in the case of including the step (D), one satisfying all the following conditions (a) to (d) can be mentioned.
(A) The amount of the hexavalent chromium-containing compound in the step (A) is such that the mass of the hexavalent chromium is 1.0 to 2.0 mg with respect to 1 liter of water as the solvent of the slurry.
(B) The amount of magnesium oxide in the step (A) is 10 to 35 g with respect to 1 liter of water as a solvent for the slurry.
(C) The stirring time in the step (A) is 15 to 20 minutes.
(D) Step (D) is to select magnesium oxide that has been found that 35% by mass or more of the total amount of hexavalent chromium in the hexavalent chromium-containing compound has been recovered as a solid content.
The heavy metal elution reducing agent can contain other substances (for example, zeolite, diatomaceous earth, white clay, bentonite, dry clay, calcium carbonate, quartzite powder, gypsum, etc.) in addition to magnesium oxide. In this case, the heavy metal elution reducing agent is prepared by mixing the selected magnesium oxide and other substances.
The addition amount of the heavy metal elution reducing agent varies depending on the kind and amount of heavy metal contained in the contaminated soil, but is usually preferably 10 kg or more, more preferably 50 kg or more with respect to 1 m 3 of the contaminated soil. The upper limit of the addition amount is not particularly limited, but is usually 300 kg with respect to 1 m 3 of contaminated soil.
［実施例１〜６］
（１）評価対象物である酸化マグネシウムの調製
マグネサイト原石を８００〜１１００℃程度で４時間加熱して、各種の酸化マグネシウム（以下、「軽焼マグネシアＡ」〜「軽焼マグネシアＦ」という。）を得た。
蒸留水１リットルに、二クロム酸カリウム（Ｋ2Ｃｒ2Ｏ7）０．０４２４３ｇを溶解させて、６価クロム（Ｃｒ）の濃度が１５．０ｍｇ／リットルである溶液を調製した後、この溶液を蒸留水で１０倍に希釈して、６価クロムの濃度が１．５ｍｇ／リットルである６価クロム含有溶液（表１中の「Ｃｒ(1)」）を調製した。
次いで、この６価クロム含有溶液１００ミリリットルを振とう器に投入した後、この振とう器に、表１に示す種類のＭｇＯ（軽焼マグネシア）を１ｇ投入し、振とうした。なお、表１中の「ＭｇＯの種類」の欄の「Ａ」〜「Ｆ」は、各々、「軽焼マグネシアＡ」〜「軽焼マグネシアＦ」を意味する。
振とうは、１５分間、２００回／分の条件、または、６０分間、２００回／分の条件で行なった。
振とう後、得られたスラリーから、先端にメンブレンフィルター（目開き寸法：０．４５μｍ）を装着した注射器を用いて液分１０ミリリットルを吸引して、この液分中の６価クロムイオン濃度（ｍｇ／リットル）を測定した。結果を表１に「重金属等の溶出量（ｍｇ／Ｌ）」として示す。
１５分間の振とう後の液分の６価クロムイオン濃度が、１．０ｍｇ／リットル未満である場合を、酸化マグネシウムの重金属不溶化性能が良好（表１中、「○」）であるとし、該６価クロムイオン濃度が、１．０ｍｇ／リットル以上である場合を、酸化マグネシウムの重金属不溶化性能が不良（表１中、「×」）であるとして、酸化マグネシウムを評価した。評価結果を表１に「簡易評価方法でのＭｇＯの評価結果」として示す。
一方、６価クロムを７．５ｍｇ／ｋｇの濃度で含む汚染土壌に対して、汚染土壌１ｍ3当たり１００ｋｇの量となるように前記の「軽焼マグネシアＡ」〜「軽焼マグネシアＦ」のいずれかを添加し、かつ、含水比が１４２％になるように水分量を調整して混合し、放置した。なお、含水比とは、（水の質量／汚染土壌の乾燥質量）×１００を意味する。
混合から７日後に、環境省告示第４６号法に準じて、６価クロムの溶出試験を行なった。
結果を表１中に「汚染土壌実験での重金属等の溶出量（ｍｇ／Ｌ）」として示す。なお、軽焼マグネシアを添加しない場合の当該６価クロムイオン濃度を測定したところ、０．９８ｍｇ／リットルであった。
６価クロムイオン濃度が０．４０ｍｇ／リットル未満である場合を、酸化マグネシウムの重金属不溶化性能が良好（表１中、「○」）であるとし、６価クロムイオン濃度が、０．４０ｍｇ／リットル以上である場合を、酸化マグネシウムの重金属不溶化性能が不良（表１中、「×」）であるとして、酸化マグネシウムを評価した。評価結果を表１に「汚染土壌実験でのＭｇＯの評価結果」として示す。
表１中の実施例１〜６から、本発明の簡易評価方法による軽焼マグネシアの評価結果は、汚染土壌を用いて実際に軽焼マグネシア（ＭｇＯ）の重金属不溶化性能を調べた結果と一致していることがわかる。
[Examples 1 to 6]
(1) Preparation of Magnesium Oxide as Evaluation Object The raw magnesite ore is heated at about 800 to 1100 ° C. for 4 hours, and various magnesium oxides (hereinafter referred to as “light calcined magnesia A” to “light calcined magnesia F”). )
After dissolving 0.04243 g of potassium dichromate (K 2 Cr 2 O 7 ) in 1 liter of distilled water to prepare a solution having a hexavalent chromium (Cr) concentration of 15.0 mg / liter, this solution Was diluted 10-fold with distilled water to prepare a hexavalent chromium-containing solution (“Cr (1)” in Table 1) having a hexavalent chromium concentration of 1.5 mg / liter.
Next, 100 ml of this hexavalent chromium-containing solution was put into a shaker, and then 1 g of MgO (lightly burned magnesia) shown in Table 1 was put into the shaker and shaken. In Table 1, “A” to “F” in the column of “MgO type” mean “lightly burned magnesia A” to “lightly burned magnesia F”, respectively.
Shaking was performed for 15 minutes at 200 times / minute or for 60 minutes at 200 times / minute.
After shaking, 10 ml of the liquid content is aspirated from the resulting slurry using a syringe equipped with a membrane filter (opening size: 0.45 μm) at the tip, and the concentration of hexavalent chromium ions ( mg / liter). The results are shown in Table 1 as “elution amount of heavy metals (mg / L)”.
When the hexavalent chromium ion concentration in the liquid after shaking for 15 minutes is less than 1.0 mg / liter, the heavy metal insolubilization performance of magnesium oxide is assumed to be good (“◯” in Table 1). Magnesium oxide was evaluated when the hexavalent chromium ion concentration was 1.0 mg / liter or more, assuming that the heavy metal insolubilization performance of magnesium oxide was poor ("X" in Table 1). The evaluation results are shown in Table 1 as “Evaluation results of MgO by the simple evaluation method”.
On the other hand, any of the above “light-burned magnesia A” to “light-burned magnesia F” so that the amount of contaminated soil containing hexavalent chromium at a concentration of 7.5 mg / kg is 100 kg per 1 m 3 of the contaminated soil. The water content was adjusted so that the water content ratio was 142%, mixed, and allowed to stand. The water content means (mass of water / dry mass of contaminated soil) × 100.
Seven days after mixing, a hexavalent chromium elution test was conducted in accordance with the Ministry of the Environment Notification No. 46.
The results are shown in Table 1 as “elution amount of heavy metals and the like (mg / L) in the contaminated soil experiment”. The hexavalent chromium ion concentration in the case where light-burned magnesia was not added was 0.98 mg / liter.
When the hexavalent chromium ion concentration is less than 0.40 mg / liter, the heavy metal insolubilization performance of magnesium oxide is assumed to be good (“◯” in Table 1), and the hexavalent chromium ion concentration is 0.40 mg / liter. In the above case, magnesium oxide was evaluated on the assumption that the heavy metal insolubilization performance of magnesium oxide was poor ("X" in Table 1). The evaluation results are shown in Table 1 as “Evaluation results of MgO in the contaminated soil experiment”.
From Examples 1 to 6 in Table 1, the evaluation results of light burned magnesia by the simple evaluation method of the present invention coincide with the results of actually examining the heavy metal insolubilization performance of light burned magnesia (MgO) using contaminated soil. You can see that
［実施例７］
二クロム酸カリウム（Ｋ2Ｃｒ2Ｏ7）に代えてクロム酸（ＣｒＯ3）を用いて、６価クロムの濃度が１．５ｍｇ／リットルである６価クロム含有溶液（表１中の「Ｃｒ(2)」）を調製したこと以外は、実施例１と同様にして実験した。その結果、表１に示すように、実施例１と同じ結果が得られた。
［実施例８］
二クロム酸カリウム（Ｋ2Ｃｒ2Ｏ7）に代えて、二クロム酸カリウム（Ｋ2Ｃｒ2Ｏ7）と硝酸との混合物である原子吸光用標準試薬を用いて、６価クロムの濃度が１．５ｍｇ／リットルである６価クロム含有溶液（表１中の「Ｃｒ(3)」；ｐＨ４．５）を調製したこと以外は、実施例１と同様にして実験した。その結果、表１に示すように、実施例１と同じ結果が得られた。
なお、水酸化ナトリウムを用いて６価クロム含有溶液のｐＨを４．５から７．２または９．８に変えた各場合についても、前記と同様にして実験した。その結果、ｐＨの変化による有意な差は見られなかった。
実施例７、８の結果から、６価クロム含有化合物の種類や、溶媒のｐＨを変えても、本発明の評価結果は変わらないことがわかる。
[Example 7]
Instead of potassium dichromate (K 2 Cr 2 O 7 ), chromic acid (CrO 3 ) was used, and a hexavalent chromium-containing solution having a concentration of hexavalent chromium of 1.5 mg / liter (“Cr” in Table 1) The experiment was performed in the same manner as in Example 1 except that (2) ") was prepared. As a result, as shown in Table 1, the same result as in Example 1 was obtained.
[Example 8]
Instead of potassium dichromate (K 2 Cr 2 O 7), using a standard reagent for atomic absorption is a mixture of potassium dichromate (K 2 Cr 2 O 7) and nitric acid, the concentration of hexavalent chromium An experiment was conducted in the same manner as in Example 1 except that a hexavalent chromium-containing solution (“Cr (3)” in Table 1; pH 4.5) of 1.5 mg / liter was prepared. As a result, as shown in Table 1, the same result as in Example 1 was obtained.
In each case where the pH of the hexavalent chromium-containing solution was changed from 4.5 to 7.2 or 9.8 using sodium hydroxide, the experiment was performed in the same manner as described above. As a result, no significant difference was observed due to the change in pH.
From the results of Examples 7 and 8, it can be seen that the evaluation results of the present invention do not change even when the kind of the hexavalent chromium-containing compound and the pH of the solvent are changed.
［比較例１、２］
二クロム酸カリウムに代えて硝酸鉛（ＰｂＮＯ3）を用い、鉛（Ｐｂ）の濃度が１．５ｍｇ／リットルである鉛含有溶液を調製したこと以外は、実施例１、６と同様にして実験した。その結果、１５分間と６０分間のいずれの撹拌後も、液分中に鉛は検出されなかった。
［比較例３、４］
二クロム酸カリウムに代えて塩化カドミウム（ＣｄＣｌ2）を用い、カドミウム（Ｃｄ）の濃度が１．５ｍｇ／リットルであるカドミウム含有溶液を調製したこと以外は、実施例１、６と同様にして実験した。その結果、１５分間と６０分間のいずれの撹拌後も、液分中にカドミウムは検出されなかった。
［比較例５、６］
二クロム酸カリウムに代えて亜砒酸ナトリウム（ＮａＡｓＯ2）を用い、砒素（Ａｓ）の濃度が１．５ｍｇ／リットルである砒素含有溶液を調製したこと以外は、実施例１、６と同様にして実験した。その結果、１５分間と６０分間のいずれの撹拌後も、液分中に砒素は検出されなかった。なお、砒素は、重金属ではないが、汚染土壌中にしばしば含まれる有害物質である。
［比較例７、８］
二クロム酸カリウムに代えてフッ化カリウム（ＫＦ）を用い、フッ素（Ｆ）の濃度が１．５ｍｇ／リットルであるフッ素含有溶液を調製したこと以外は、実施例１、６と同様にして実験した。なお、フッ素も重金属ではないが、汚染土壌中にしばしば含まれる有害物質である。その結果、液分中のフッ素濃度は、１５分間と６０分間のいずれの撹拌後も、軽焼マグネシアＡよりも軽焼マグネシアＦの方が小さくなり、汚染土壌を用いて実際に軽焼マグネシアの重金属不溶化性能を調べた結果とは逆の結果となった。
［比較例９、１０］
二クロム酸カリウムに代えて四ホウ酸ナトリウム（Ｎａ2Ｂ4Ｏ7・10Ｈ2Ｏ）を用い、ホウ素（Ｂ）の濃度が１．５ｍｇ／リットルであるホウ素含有溶液を調製したこと以外は、実施例１、６と同様にして実験した。なお、ホウ素も重金属ではないが、汚染土壌中にしばしば含まれる有害物質である。その結果、液分中のホウ素濃度は、１５分間と６０分間のいずれの撹拌後も、軽焼マグネシアＡと軽焼マグネシアＦとで同じであった。
比較例１〜１０の結果から、６価クロム以外の重金属等を用いた場合、酸化マグネシウムの重金属不溶化性能の優劣を評価できないことがわかる。
[Comparative Examples 1 and 2]
Experiments were carried out in the same manner as in Examples 1 and 6 except that lead nitrate (PbNO 3 ) was used instead of potassium dichromate and a lead-containing solution having a lead (Pb) concentration of 1.5 mg / liter was prepared. did. As a result, lead was not detected in the liquid after both 15 minutes and 60 minutes of stirring.
[Comparative Examples 3 and 4]
Experiments were carried out in the same manner as in Examples 1 and 6 except that cadmium chloride (CdCl 2 ) was used instead of potassium dichromate and a cadmium-containing solution having a cadmium (Cd) concentration of 1.5 mg / liter was prepared. did. As a result, cadmium was not detected in the liquid after both 15 minutes and 60 minutes of stirring.
[Comparative Examples 5 and 6]
Experiments were carried out in the same manner as in Examples 1 and 6, except that sodium arsenite (NaAsO 2 ) was used instead of potassium dichromate, and an arsenic-containing solution with an arsenic (As) concentration of 1.5 mg / liter was prepared. did. As a result, arsenic was not detected in the liquid after both 15 minutes and 60 minutes of stirring. Arsenic is not a heavy metal, but is a harmful substance often contained in contaminated soil.
[Comparative Examples 7 and 8]
Experiments were carried out in the same manner as in Examples 1 and 6 except that potassium fluoride (KF) was used instead of potassium dichromate and a fluorine-containing solution having a fluorine (F) concentration of 1.5 mg / liter was prepared. did. Although fluorine is not a heavy metal, it is a harmful substance often contained in contaminated soil. As a result, the concentration of fluorine in the liquid is smaller for light-burned magnesia F than for light-burned magnesia A after stirring for 15 minutes and 60 minutes. The result was opposite to the result of examining the heavy metal insolubilization performance.
[Comparative Examples 9 and 10]
Except for using sodium tetraborate (Na 2 B 4 O 7 .10H 2 O) instead of potassium dichromate and preparing a boron-containing solution with a boron (B) concentration of 1.5 mg / liter, Experiments were performed in the same manner as in Examples 1 and 6. Boron is not a heavy metal, but is a harmful substance often contained in contaminated soil. As a result, the boron concentration in the liquid was the same for light-burned magnesia A and light-burned magnesia F after both 15 minutes and 60 minutes of stirring.
From the results of Comparative Examples 1 to 10, it is understood that the superiority or inferiority of the magnesium oxide heavy metal insolubilization performance cannot be evaluated when heavy metals other than hexavalent chromium are used.
［実施例９〜４３］
実施例１〜８で用いた軽焼マグネシアとは異なる種類の軽焼マグネシア（以下、「軽焼マグネシアＧ」という。）を用いて、水１リットル当たり表２に示す量の６価クロム及び酸化マグネシウムを含むスラリーを調製し、かつ、表２に示す振とう時間としたこと以外は、実施例１と同様にして実験した。なお、実施例２２における水１リットル当たりの６価クロム量及び酸化マグネシウム量は、実施例１〜８と同じである。
実施例２２において、振とう時間が１５分間である場合、液分中の６価クロムの溶出量は、１．０６ｍｇ／リットルであった。この値は、実施例６（軽焼マグネシアＦを用いた実験例）と同じである。したがって、実施例９〜４３で用いた軽焼マグネシアＧの重金属不溶化性能の評価結果は、「×」（不良）である。
実施例９〜４３において、液分中の６価クロムの溶出量の測定値に基いて算出した、不溶化した６価クロムの質量割合を、表２に示す。
[Examples 9 to 43]
The amount of hexavalent chromium and oxidation shown in Table 2 per liter of water using a light-burned magnesia different from the light-burned magnesia used in Examples 1 to 8 (hereinafter referred to as “light-burned magnesia G”). An experiment was conducted in the same manner as in Example 1 except that a slurry containing magnesium was prepared and the shaking time shown in Table 2 was used. The amount of hexavalent chromium and the amount of magnesium oxide per liter of water in Example 22 are the same as those in Examples 1-8.
In Example 22, when the shaking time was 15 minutes, the elution amount of hexavalent chromium in the liquid was 1.06 mg / liter. This value is the same as Example 6 (an experimental example using light-burned magnesia F). Therefore, the evaluation result of the heavy metal insolubilization performance of the light burned magnesia G used in Examples 9 to 43 is “x” (defective).
In Examples 9 to 43, Table 2 shows mass ratios of the insolubilized hexavalent chromium calculated based on the measurement value of the elution amount of hexavalent chromium in the liquid.
Claims (5)
（Ｂ）得られたスラリーを固液分離して、上記６価クロム含有化合物の一部に由来する６価クロムイオンを含む液分、及び、上記６価クロム含有化合物の残部に由来する６価クロムと上記酸化マグネシウムに由来する水酸化マグネシウムとを含む固体分を得る固液分離工程と、
（Ｃ）得られた液分中の６価クロムイオン濃度を測定して、上記酸化マグネシウムの重金属不溶化性能を評価する評価工程と
を含む酸化マグネシウムの重金属不溶化性能の評価方法であって、
工程（Ａ）において、上記６価クロム含有化合物の量は、上記スラリーの溶媒である水１リットルに対して６価クロムの質量が０．７５〜１０ｍｇとなる量であり、かつ、上記酸化マグネシウムの量は、上記スラリーの溶媒である水１リットルに対して３〜１００ｇであることを特徴とする酸化マグネシウムの重金属不溶化性能の評価方法。 (A) a mixing step of mixing a hexavalent chromium-containing compound and magnesium oxide with water as a solvent and stirring to obtain a slurry;
(B) The obtained slurry is subjected to solid-liquid separation, and a liquid component containing hexavalent chromium ions derived from a part of the hexavalent chromium-containing compound and hexavalent derived from the remainder of the hexavalent chromium-containing compound. A solid-liquid separation step for obtaining a solid content containing chromium and magnesium hydroxide derived from the magnesium oxide;
(C) an evaluation method for evaluating the heavy metal insolubilization performance of magnesium oxide , including an evaluation step of measuring the hexavalent chromium ion concentration in the obtained liquid and evaluating the heavy metal insolubilization performance of the magnesium oxide,
In the step (A), the amount of the hexavalent chromium-containing compound is such that the mass of hexavalent chromium is 0.75 to 10 mg with respect to 1 liter of water as the solvent of the slurry, and the magnesium oxide. The amount of is 3 to 100 g with respect to 1 liter of water which is the solvent of the slurry, and the method for evaluating the heavy metal insolubilization performance of magnesium oxide.
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| CN102895936B (en) * | 2011-07-29 | 2016-09-28 | 住友大阪水泥股份有限公司 | Dissolution reduces material and manufacture method thereof |
| CN105181759A (en) * | 2015-10-16 | 2015-12-23 | 上海岩土工程勘察设计研究院有限公司 | Method for judging contamination degree of heavy-metal contaminated soil based on indoor test |
| CN108785951A (en) * | 2017-05-02 | 2018-11-13 | 广州市川清环保科技有限公司 | The insoluble inorganic agent of heavy metal and the insoluble processing method of heavy metal |
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| JPH10316967A (en) * | 1997-05-15 | 1998-12-02 | Katsuichi Kunimatsu | Soil solidification agent |
| JPH11147082A (en) * | 1997-11-14 | 1999-06-02 | Miyoshi Oil & Fat Co Ltd | Method for treating metal-containing solid waste |
| JP3721970B2 (en) * | 2000-09-21 | 2005-11-30 | 栗田工業株式会社 | Purification method for contaminated soil |
| JP2002206090A (en) * | 2000-11-09 | 2002-07-26 | Matsuda Giken Kogyo Kk | Neutral soil-solidifying agent and method of improving ground and the like, and means for preventing elution of heavy metal |
| JP2004306017A (en) * | 2003-03-26 | 2004-11-04 | Ohbayashi Corp | Cleaning system for polluted soil |
| JP3980533B2 (en) * | 2003-07-11 | 2007-09-26 | 株式会社竹中工務店 | Methods for preventing leaching of toxic metals from hazardous metal contaminated waste |
| JP2006349494A (en) * | 2005-06-15 | 2006-12-28 | Toda Kogyo Corp | Evaluation method of penetration state of ferrous purifying agent in soil |
| JP5158462B2 (en) * | 2006-03-31 | 2013-03-06 | 住友大阪セメント株式会社 | Reduced solidification of toxic metals |
| JP5291333B2 (en) * | 2007-12-26 | 2013-09-18 | 太平洋セメント株式会社 | Insolubilizing material and insolubilizing method |
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