JP5769920B2 - Soil improvement material - Google Patents
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- JP5769920B2 JP5769920B2 JP2009246227A JP2009246227A JP5769920B2 JP 5769920 B2 JP5769920 B2 JP 5769920B2 JP 2009246227 A JP2009246227 A JP 2009246227A JP 2009246227 A JP2009246227 A JP 2009246227A JP 5769920 B2 JP5769920 B2 JP 5769920B2
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- 239000002689 soil Substances 0.000 title claims description 62
- 239000000463 material Substances 0.000 title claims description 43
- 230000006872 improvement Effects 0.000 title claims description 27
- 239000002893 slag Substances 0.000 claims description 131
- 238000009628 steelmaking Methods 0.000 claims description 65
- 229910052751 metal Inorganic materials 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 22
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 21
- 239000002245 particle Substances 0.000 claims description 13
- 230000005484 gravity Effects 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 239000003516 soil conditioner Substances 0.000 claims description 6
- -1 thiosulfate ions Chemical class 0.000 claims description 6
- 238000002386 leaching Methods 0.000 claims description 5
- 229910000831 Steel Inorganic materials 0.000 claims description 4
- 239000010959 steel Substances 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 75
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 60
- 238000006722 reduction reaction Methods 0.000 description 33
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 31
- 230000009467 reduction Effects 0.000 description 31
- 230000000694 effects Effects 0.000 description 24
- 238000000034 method Methods 0.000 description 19
- 238000010828 elution Methods 0.000 description 18
- 230000001603 reducing effect Effects 0.000 description 14
- 239000011575 calcium Substances 0.000 description 13
- 238000010583 slow cooling Methods 0.000 description 11
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 10
- 239000000126 substance Substances 0.000 description 9
- 239000003638 chemical reducing agent Substances 0.000 description 8
- 150000001450 anions Chemical class 0.000 description 7
- 230000007613 environmental effect Effects 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 230000009471 action Effects 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 229910001385 heavy metal Inorganic materials 0.000 description 4
- 230000002452 interceptive effect Effects 0.000 description 4
- 238000007885 magnetic separation Methods 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- 230000032683 aging Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000005261 decarburization Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000011790 ferrous sulphate Substances 0.000 description 3
- 235000003891 ferrous sulphate Nutrition 0.000 description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- WETINTNJFLGREW-UHFFFAOYSA-N calcium;iron;tetrahydrate Chemical compound O.O.O.O.[Ca].[Fe].[Fe] WETINTNJFLGREW-UHFFFAOYSA-N 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000007922 dissolution test Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229920001021 polysulfide Polymers 0.000 description 2
- 239000005077 polysulfide Substances 0.000 description 2
- 150000008117 polysulfides Polymers 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000012086 standard solution Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229940006280 thiosulfate ion Drugs 0.000 description 2
- DHCDFWKWKRSZHF-UHFFFAOYSA-L thiosulfate(2-) Chemical compound [O-]S([S-])(=O)=O DHCDFWKWKRSZHF-UHFFFAOYSA-L 0.000 description 2
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 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
- 238000003723 Smelting Methods 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
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 150000004045 organic chlorine compounds Chemical class 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- CEOCDNVZRAIOQZ-UHFFFAOYSA-N pentachlorobenzene Chemical compound ClC1=CC(Cl)=C(Cl)C(Cl)=C1Cl CEOCDNVZRAIOQZ-UHFFFAOYSA-N 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Description
本発明は、６価クロムやアンモニア等のような有害物質で汚染された土壌を改良するための土壌改良材に関するものである。 The present invention relates to a soil conditioner for improving soil contaminated with harmful substances such as hexavalent chromium and ammonia.
土壌は、置かれた環境や周辺の排水の影響或いは自然由来によって、有害物質に汚染される場合があり、その汚染の度合いが環境基準値を超える場合もある。例えば、６価クロムや砒素などの重金属類、トリクロロエチレン、ダイオキシン等の有機化合物に関して、土壌環境基準等において土壌中の上限値が定められている。
６価クロムは、還元して３価にすることによって溶解度が大幅に低減し、安全性を確保できることから、還元剤を混合することで溶出抑制を図る方法が広く知られており、具体的な方法としては、還元剤として硫酸第一鉄を用いる方法（例えば、特許文献１，２）、硫黄系還元剤を用いる方法（例えば、特許文献３，４）、鉄粉を用いる方法（例えば、特許文献５，６）などがある。
Soil may be contaminated with harmful substances due to the environment where it is placed, the drainage of the surrounding area, or the natural origin, and the degree of contamination may exceed the environmental standard value. For example, with respect to heavy metals such as hexavalent chromium and arsenic, and organic compounds such as trichlorethylene and dioxin, an upper limit value in the soil is defined in the soil environmental standards.
Since hexavalent chromium is reduced to trivalent, its solubility is greatly reduced and safety can be secured. Therefore, a method for suppressing elution by mixing a reducing agent is widely known. As a method, a method using ferrous sulfate as a reducing agent (for example, Patent Documents 1 and 2), a method using a sulfur-based reducing agent (for example, Patent Documents 3 and 4), a method using iron powder (for example, a patent) There are references 5, 6).
上述した従来技術のなかで、還元剤として硫酸第一鉄を用いる方法は、速効性は高いものの、効果がすぐに失われてしまう欠点がある。また、硫黄系還元剤を用いる方法は、比較的長期の還元性能が維持されるが、速効性を確保するためには、材料の粒度や特性を特定の限られた範囲にする必要性がある。また、還元剤として鉄粉を用いる方法は、還元剤として同じ鉄系の硫酸第一鉄を用いる方法に較べて長期的な還元効果が期待できるものの、実際上の問題として、スラリー状にして混合することによる地盤の軟弱化等の問題がある。これは、鉄粉と土壌の混合条件に十分留意しないと、均質混合が難しいためである。 Among the above-described conventional techniques, the method using ferrous sulfate as the reducing agent has a drawback that the effect is lost immediately, although the rapid effect is high. In addition, the method using a sulfur-based reducing agent maintains a relatively long-term reduction performance, but it is necessary to make the particle size and characteristics of the material within a specific limited range in order to ensure quick action. . In addition, the method using iron powder as the reducing agent can be expected to have a long-term reduction effect compared to the method using the same ferrous ferrous sulfate as the reducing agent. There is a problem such as softening of the ground due to doing. This is because homogeneous mixing is difficult unless attention is paid to the mixing conditions of iron powder and soil.
本発明者らは、上述したような従来の土壌改良材の問題に鑑み、優れた還元作用を発揮して適切な土壌改良を行うことができ、且つ特別な施工条件を必要としない材料について、以下のような検討を行った。
まず、本発明者らは、鉄粉などが持つ還元作用を有効に発揮させるためには、簡便な混合でも均質性を確保できることが重要ではないかと考え、細かい鉄を含み、且つ土壌との比重差が小さい材料について探索した結果、製鋼スラグが適した材料であるとの結論を得た。
In view of the problems of the conventional soil improvement materials as described above, the present inventors can perform an appropriate soil improvement by exhibiting an excellent reducing action, and for materials that do not require special construction conditions, The following examination was conducted.
First, in order to effectively exhibit the reducing action of iron powder and the like, the present inventors consider that it is important to ensure homogeneity even with simple mixing, and contain fine iron and have a specific gravity with soil. As a result of searching for materials having a small difference, it was concluded that steelmaking slag is a suitable material.
従来、製鋼スラグを有害物質の無害化技術に利用したものとして、特許文献７〜９に示されるようなものがある。これらのうち、特許文献７に示されるのは脱硫スラグを含む固化材であるが、この固化材は脱硫スラグに含まれる硫黄による還元能力を期待したものであり、酸化鉄や鉄粉の作用効果については不明である。また、特許文献８に示されるのは、製鋼スラグとアルカノールアミンを含有する有害物質捕集材であるが、同文献（段落００２４）では、製鋼スラグのみを用いると、種々の妨害性のアニオンの濃度が高い環境下では、捕集材としての効果が期待できないとしている。また、特許文献９に示されるのは、重金属を含む廃棄物を転炉スラグ等の製鋼スラグを用いて安定化処理する方法であるが、この方法では、温水環境下で共存させるなど特殊な処理場と温度場が要求されており、また、土壌のような比表面積が大きい対象についての有効性は明確ではない。
Conventionally, as shown in Patent Documents 7 to 9, steelmaking slag is used for detoxifying technology for harmful substances. Among these, what is shown in Patent Document 7 is a solidified material containing desulfurized slag, and this solidified material is expected to have a reducing ability due to sulfur contained in the desulfurized slag, and the effect of iron oxide and iron powder. Is unknown. Further, Patent Document 8 shows a harmful substance collecting material containing steelmaking slag and alkanolamine. However, in the same document (paragraph 0024), when only steelmaking slag is used, various interfering anions are used. It is said that the effect as a collecting material cannot be expected in a high concentration environment. Further,
一方、特許文献１０，１１に記載の技術では、有害物質低減材を構成するカルシウムフェライト系材料が用いられている。この技術で使用されるカルシウムフェライト系材料は、ＣａＯとＦｅ２Ｏ３の化合物からなっており、換言すれば、鉄系の原料として３価のＦｅ源を用いるものである。この技術の本質は、有害重金属を不溶化するものであり、還元効果は期待できない。また、特許文献１１では転炉スラグが用いられているが、その役割は潜在水硬性材料としてのものである。
On the other hand, in the techniques described in
このような技術の改善策として、特許文献１２には、高炉徐冷スラグと製鋼スラグとからなる有害物質低減材が示されており、この技術は、高炉徐冷スラグにより還元効果を発揮させ、製鋼スラグのＦｅ２Ｏ３とＡｌ２Ｏ３で有害重金属を不溶化するというものである。しかし、同文献において製鋼スラグであるとしている、Ｆｅ２Ｏ３とＡｌ２Ｏ３の合計濃度が高い酸化性のスラグは、一般に知られている製鋼スラグの組成とかなり異なったものである。例えば、代表的な製鋼スラグの組成を表１に示すが、脱炭炉スラグ、脱リンスラグではＦｅ２Ｏ３とＡｌ２Ｏ３の比率は低く、２ＣａＯ・Ｆｅ２Ｏ３、４ＣａＯ・Ａｌ２Ｏ３・Ｆｅ２Ｏ３が最大限生成したと仮定しても、Ｆｅ２Ｏ３とＡｌ２Ｏ３の合計濃度が２０質量％を超えることはない。また、電気炉スラグはＡｌ２Ｏ３の割合が比較的高く、Ｆｅ２Ｏ３とＡｌ２Ｏ３の合計濃度は高めになるものの、Ｆｅ２Ｏ３やＣａＯは少ないため、２ＣａＯ・Ｆｅ２Ｏ３、４ＣａＯ・Ａｌ２Ｏ３・Ｆｅ２Ｏ３が最大限生成したとしても、Ｆｅ２Ｏ３とＡｌ２Ｏ３の合計濃度は脱炭炉スラグや脱リンスラグと同程度である。加えて、実際のスラグでは、２ＣａＯ・ＳｉＯ２やＭｇＯ、スピネル等との固溶物もあり、そのような生成量にはならない。したがって、特許文献１２に示されるようなＦｅ２Ｏ３とＡｌ２Ｏ３の合計濃度が高いスラグを得るには、精錬工程で発生した製鋼スラグに特別な処理（例えば、熱処理などで酸化させる）を加えてＦｅ２Ｏ３を増やす必要がある。また、特許文献１２が使用する有害物質低減材は、その反応機構から明らかなように、一般的な鉄鋼製造プロセスで発生する製鋼スラグが有する金属ＦｅやＦｅＯの反応を有効に活用するものではない。したがってまた、特許文献１２には、スラグのＦｅ２Ｏ３とＡｌ２Ｏ３の合計量の記載しかなく、トータルＦｅ、ＦｅＯ、金属Ｆｅの各含有量は全く不明である。 As a measure for improving such technology, Patent Document 12 shows a harmful substance reducing material composed of blast furnace slow cooling slag and steelmaking slag, and this technology exhibits a reduction effect by blast furnace slow cooling slag, In this method, harmful heavy metals are insolubilized with Fe 2 O 3 and Al 2 O 3 of steelmaking slag. However, the oxidizing slag having a high total concentration of Fe 2 O 3 and Al 2 O 3 , which is said to be steelmaking slag in the same document, is quite different from the composition of generally known steelmaking slag. For example, the composition of typical steelmaking slag is shown in Table 1. In the decarburization furnace slag and dephosphorization slag, the ratio of Fe 2 O 3 and Al 2 O 3 is low, 2CaO · Fe 2 O 3 , 4CaO · Al 2 O. Even if it is assumed that 3 · Fe 2 O 3 is generated to the maximum extent, the total concentration of Fe 2 O 3 and Al 2 O 3 does not exceed 20 mass%. Moreover, although the ratio of Al 2 O 3 is relatively high in the electric furnace slag and the total concentration of Fe 2 O 3 and Al 2 O 3 is high, Fe 2 O 3 and CaO are small, so 2CaO · Fe 2 O Even if 3 , 4CaO.Al 2 O 3 .Fe 2 O 3 is produced to the maximum extent, the total concentration of Fe 2 O 3 and Al 2 O 3 is comparable to decarburization furnace slag and dephosphorization slag. In addition, in actual slag, there is a solid solution with 2CaO · SiO 2 , MgO, spinel, etc., and such a generated amount is not obtained. Therefore, in order to obtain a slag having a high total concentration of Fe 2 O 3 and Al 2 O 3 as shown in Patent Document 12, the steelmaking slag generated in the refining process is specially treated (for example, oxidized by heat treatment or the like). To increase Fe 2 O 3 . Moreover, the harmful substance reducing material used in Patent Document 12 does not effectively utilize the reaction of metal Fe or FeO contained in steelmaking slag generated in a general steelmaking process, as is apparent from the reaction mechanism. . Therefore, Patent Document 12 only describes the total amount of Fe 2 O 3 and Al 2 O 3 in the slag, and the contents of total Fe, FeO, and metal Fe are completely unknown.
したがって本発明の目的は、発生後特別な処理を施すことなく常温まで冷却した製鋼スラグを利用した土壌改良材であって、製鋼スラグの還元作用によって６価クロム等の有害物質の有害性を低減し、土壌の環境安全性を効果的に改善できる土壌改良材を提供することにある。 Therefore, an object of the present invention is a soil improvement material using steelmaking slag cooled to room temperature without performing any special treatment after generation, and reduces the harmfulness of harmful substances such as hexavalent chromium by the reducing action of steelmaking slag. And providing a soil conditioner that can effectively improve the environmental safety of the soil.
本発明者らは、上記課題を解決すべく検討を重ねた結果、以下のような知見を得た。すなわち、製鋼スラグが有する金属ＦｅやＦｅＯは還元機能を十分有しているが、置かれた環境とアニオン類の影響によって還元等の能力が低下し、また土壌の種類によっても、元素の吸着効果によって、その効果が大きく変動してしまう。したがって、これを抑制することができれば、製鋼スラグだけを添加した場合でも有効な還元効果が発現できる。具体的には、トータルＦｅおよびＦｅＯの含有量とＣａＯ／ＳｉＯ２を所定レベル以上とした製鋼スラグを用いることにより、スラグから十分な量のＣａ分を供給して、妨害性アニオンの効果を適切に抑制しつつ、鉄および酸化鉄による還元作用を十分に発揮させることができる。 As a result of repeated studies to solve the above problems, the present inventors have obtained the following knowledge. In other words, metal Fe and FeO possessed by steelmaking slag have a sufficient reducing function, but the ability to reduce, etc. is reduced by the influence of the environment and anions, and the effect of adsorption of elements also depends on the type of soil. Depending on the situation, the effect will vary greatly. Therefore, if this can be suppressed, an effective reduction effect can be exhibited even when only steelmaking slag is added. Specifically, by using a steel slag which the content and CaO / SiO 2 of total Fe and FeO to a predetermined level or higher, by supplying a Ca content sufficient amount of slag, the proper effects of interfering anions It is possible to sufficiently exhibit the reducing action of iron and iron oxide while suppressing the above.
本発明はこのような知見に基づきなされたもので、以下を要旨とするものである。
［1］土壌と混合して使用される土壌改良材であって、トータルＦｅ含有量が２０質量％以上、ＦｅＯ含有量が１０質量％以上、ＣａＯ／ＳｉＯ２（質量比）が２以上、５未満である製鋼スラグからなることを特徴とする土壌改良材。
［2］上記［1］の土壌改良材において、製鋼スラグの金属Ｆｅ含有量が１質量％以上であることを特徴とする土壌改良材。
The present invention has been made on the basis of such findings and has the following gist.
[1] A soil improvement material used by mixing with soil, wherein the total Fe content is 20% by mass or more, the FeO content is 10% by mass or more, and the CaO / SiO 2 (mass ratio) is 2 or more, 5 A soil improvement material comprising steelmaking slag that is less than.
[2] The soil improvement material according to [1], wherein the metal Fe content of the steelmaking slag is 1% by mass or more.
［3］上記［1］または［2］の土壌改良材において、さらに、未エージングの高炉徐冷スラグを含むことを特徴とする土壌改良材。
［4］上記［3］の土壌改良材において、未エージングの高炉徐冷スラグは、粒径１０ｍｍ以下の割合が９０mass％以上である粒度を有することを特徴とする土壌改良材。
［5］上記［3］または［4］の土壌改良材において、未エージングの高炉徐冷スラグは、水：スラグ＝１０：１の質量部割合で水と混合し、２００ｒｐｍで６時間振とう後、ろ過したときのチオ硫酸イオンの浸出量が３０ｍｇ／Ｌ以上となるスラグであることを特徴とする土壌改良材。
［6］上記［1］〜［5］のいずれかの土壌改良材において、製鋼スラグの比重が３〜４であることを特徴とする土壌改良材。
[3] The soil conditioner according to the above [1] or [2], further comprising unaged blast furnace chilled slag.
[4] The soil improvement material according to [3], wherein the unaged blast furnace chilled slag has a particle size in which a ratio of a particle size of 10 mm or less is 90 mass% or more.
[5] In the soil improvement material of [3] or [4] above, unaged blast furnace chilled slag is mixed with water at a mass part ratio of water: slag = 10: 1, and shaken at 200 rpm for 6 hours. A soil conditioner characterized by being a slag that has a leaching amount of thiosulfate ions of 30 mg / L or more when filtered.
[6] The soil improvement material according to any one of [1] to [5], wherein the specific gravity of the steelmaking slag is 3 to 4.
本発明の土壌改良材は、製鋼スラグまたは製鋼スラグ＋高炉徐冷スラグだけからなる土壌改良材でありながら、製鋼スラグまたは製鋼スラグ＋高炉徐冷スラグの還元作用によって６価クロム等の有害物質の有害性を低減し、土壌の環境安全性を効果的に改善することができる。 Although the soil improvement material of the present invention is a soil improvement material consisting only of steelmaking slag or steelmaking slag + blast furnace chilled slag, harmful substances such as hexavalent chromium are reduced by the reduction action of steelmaking slag or steelmaking slag + blast furnace chilled slag. It can reduce the harmfulness and can effectively improve the environmental safety of the soil.
本発明の土壌改良材は、トータルＦｅ含有量が１５質量％以上、好ましくは２０質量％以上、ＦｅＯ含有量が１０質量％以上、ＣａＯ／ＳｉＯ２（質量比）が２以上５未満、好ましくは３以上５未満の製鋼スラグからなるものである。
このように所定レベル以上のトータルＦｅ含有量とＦｅＯ含有量を有し、且つＣａＯ／ＳｉＯ２（質量比）が２以上、好ましくは３以上の製鋼スラグを土壌改良材として用いることにより、土壌の表面水や間隙水が製鋼スラグと接触した際にＣａ分が供給され、妨害性アニオンの効果を適切に抑制することができ、鉄および酸化鉄による還元能力を十分に発揮させることが可能となる。また、セメント等による粘土質等の土壌改良では、セメントから供給されるＣａが粘土鉱物の表面や層間に吸着されてしまい、Ｃａによる効果が十分に得られないという問題があるが、製鋼スラグにより十分なＣａを供給することによって、効果を維持できることも判った。
The soil improvement material of the present invention has a total Fe content of 15% by mass or more, preferably 20% by mass or more, an FeO content of 10% by mass or more, and a CaO / SiO 2 (mass ratio) of 2 to less than 5, preferably It consists of 3 or more and less than 5 steelmaking slag.
Thus, by using a steelmaking slag having a total Fe content and a FeO content of a predetermined level or more and having a CaO / SiO 2 (mass ratio) of 2 or more, preferably 3 or more as a soil improver, When surface water or interstitial water comes into contact with steelmaking slag, Ca content is supplied, the effect of interfering anions can be appropriately suppressed, and the ability to reduce by iron and iron oxide can be fully exhibited. . Moreover, in soil improvement such as clay with cement etc., there is a problem that Ca supplied from cement is adsorbed between the surface of clay minerals and between layers, and the effect of Ca cannot be sufficiently obtained. It was also found that the effect can be maintained by supplying sufficient Ca.
製鋼スラグのトータルＦｅ含有量が１５質量％未満、ＦｅＯ含有量が１０質量％未満では、土壌との接触比が十分確保できないこと、土壌種類の影響で効果が不安定になるケースがあることから、いずれの場合も鉄および酸化鉄による還元作用が十分に得られない。また、このような観点から、より好ましいトータルＦｅ含有量は２０質量％以上である。
また、製鋼スラグは、金属Ｆｅ含有量が１質量％以上、望ましくは３質量％以上であることが好ましく、このような量の金属Ｆｅを含有することにより、還元作用をより高めることができる。
製鋼スラグは、上述したＦｅＯと金属Ｆｅ以外に、水酸化鉄や３価の鉄酸化物などを含んでいてもよい。
If the total Fe content of the steelmaking slag is less than 15% by mass and the FeO content is less than 10% by mass, the contact ratio with the soil cannot be secured sufficiently, and the effect may be unstable due to the influence of the soil type. In either case, the reduction action by iron and iron oxide cannot be sufficiently obtained. From such a viewpoint, the more preferable total Fe content is 20% by mass or more.
Further, the steelmaking slag has a metal Fe content of 1% by mass or more, preferably 3% by mass or more. By containing such an amount of metal Fe, the reduction action can be further enhanced.
Steelmaking slag may contain iron hydroxide, trivalent iron oxide, etc. in addition to the above-described FeO and metal Fe.
図１〜図３に、製鋼スラグのトータルＦｅ含有量、ＦｅＯ含有量、金属Ｆｅ含有量と６価クロム還元率との関係を調査した結果を示す。これらの試験では、クロム標準液を用いて、６価クロム濃度を０．５ｍｇ／Ｌに調整し、これを土壌に１０質量％添加した。この土壌質量：１に対して製鋼スラグを質量比で０．５の割合で混合し、これを１日静置した後、環境庁告示第４６号法で６価クロム溶出試験を行い、６価クロム還元率（還元後の６価クロム量／還元前の６価クロム量）を調べた。 1 to 3 show the results of investigating the relationship between the total Fe content, the FeO content, the metal Fe content, and the hexavalent chromium reduction rate of steelmaking slag. In these tests, the hexavalent chromium concentration was adjusted to 0.5 mg / L using a chromium standard solution, and 10% by mass of this was added to the soil. Steel soil slag was mixed at a mass ratio of 0.5 with respect to this soil mass: 1 and allowed to stand for one day. Then, a hexavalent chromium elution test was conducted by the Environmental Agency Notification Method No. 46. The chromium reduction rate (the amount of hexavalent chromium after reduction / the amount of hexavalent chromium before reduction) was examined.
図１の試験では、精錬炉における撹拌条件を変えてトータルＦｅ含有量が異なる製鋼スラグを生成させた。この製鋼スラグのＣａＯ／ＳｉＯ２（質量比）は３．２〜４．２、金属Ｆｅ含有量は２質量％であり、ＦｅＯ含有量はトータルＦｅの７５質量％がＦｅＯとなるように調整した。また、図２の試験では、トータルＦｅ含有量が１８〜２０質量％、金属Ｆｅ含有量が１．５質量％、ＣａＯ／ＳｉＯ２（質量比）が３．８〜４．２の製鋼スラグの冷却時酸化条件を変更して、ＦｅＯ含有量の異なる製鋼スラグを生成させた。さらに、図３の試験では、トータルＦｅ含有量が２０質量％、ＦｅＯ含有量が１０〜１５質量％の製鋼スラグについて、磁選の条件を変えることで所定の金属Ｆｅ含有量になるように調整した。 In the test of FIG. 1, steelmaking slag having different total Fe contents was generated by changing the stirring conditions in the smelting furnace. This steelmaking slag has a CaO / SiO 2 (mass ratio) of 3.2 to 4.2, a metal Fe content of 2 mass%, and the FeO content was adjusted so that 75 mass% of the total Fe becomes FeO. . Moreover, in the test of FIG. 2, the total Fe content is 18 to 20% by mass, the metal Fe content is 1.5% by mass, and the CaO / SiO 2 (mass ratio) is 3.8 to 4.2. Steelmaking slag having different FeO contents was generated by changing the oxidation conditions during cooling. Furthermore, in the test of FIG. 3, the steelmaking slag having a total Fe content of 20% by mass and a FeO content of 10 to 15% by mass was adjusted to have a predetermined metal Fe content by changing the magnetic separation conditions. .
図１および図２によれば、トータルＦｅ含有量が１５質量％以上、ＦｅＯ含有量が１０質量％以上の製鋼スラグを用いることで、６０％以上の６価クロム還元率が得られることが判る。さらに、トータルＦｅ含有量が２０質量％以上になると、８０％以上の６価クロム還元率が得られ、より好ましいことが判る。また、図３によれば、特に金属Ｆｅ含有量が１質量％以上、好ましくは３質量％以上の製鋼スラグを用いることにより、より高い６価クロム還元率が得られることが判る。 According to FIG. 1 and FIG. 2, it is understood that a hexavalent chromium reduction rate of 60% or more can be obtained by using a steelmaking slag having a total Fe content of 15% by mass or more and an FeO content of 10% by mass or more. . Furthermore, it can be seen that when the total Fe content is 20% by mass or more, a hexavalent chromium reduction rate of 80% or more is obtained, which is more preferable. Moreover, according to FIG. 3, it can be seen that a higher hexavalent chromium reduction rate can be obtained by using a steelmaking slag having a metal Fe content of 1% by mass or more, preferably 3% by mass or more.
なお、トータルＦｅ含有量の上限は特に規定するものではないが、金属Ｆｅの比重が７．８、ＦｅＯの比重が５．７であり、土壌の比重は火山灰で２．４、非火山灰で２．６程度であることから判るように、製鋼スラグ中のトータルＦｅ含有量が多すぎるとスラグと土壌との比重差が大きく、混合時に分離しやすくなり、均質な混合が難しくなったり、処理にばらつきが生じるという問題が発生しやすい。したがって、土壌との比重差が小さい方が好ましく、製鋼スラグの比重は３〜４となるような成分比率であることが好ましい。この点から、Ｆｅの酸化状態にもよるが、トータルＦｅ含有量は３０質量％以下であることが好ましく、２６質量％以下であることがさらに好ましい。製鋼スラグの比重が３〜４程度であれば、土壌と比重が近いことから、安定した混合・還元特性を得ることが可能となる。 The upper limit of the total Fe content is not particularly specified, but the specific gravity of metal Fe is 7.8, the specific gravity of FeO is 5.7, the specific gravity of soil is 2.4 for volcanic ash and 2 for non-volcanic ash. .6 As can be seen from the fact that there is too much total Fe content in steelmaking slag, the difference in specific gravity between slag and soil is large, making it easier to separate during mixing, making it difficult to achieve homogeneous mixing, The problem of variations is likely to occur. Therefore, the one where the specific gravity difference with soil is smaller is preferable, and it is preferable that the specific gravity of steelmaking slag is a component ratio which will be 3-4. From this point, although depending on the oxidation state of Fe, the total Fe content is preferably 30% by mass or less, and more preferably 26% by mass or less. If the specific gravity of steelmaking slag is about 3-4, since the specific gravity is close to soil, it becomes possible to obtain stable mixing / reduction characteristics.
製鋼スラグの塩基度、すなわちＣａＯ／ＳｉＯ２（質量比）が２未満では、Ｃａ溶出量が急激に低下し、周辺の妨害性のアニオンによる影響を吸収しきれない場合がある。この観点から、より好ましいＣａＯ／ＳｉＯ２（質量比）は３以上である。一方、製鋼スラグのＣａＯ／ＳｉＯ２（質量比）が５以上では、還元効果に及ぼす影響はないものの、スラグ中の遊離ＣａＯが残存する量が多いことになり、土壌の体積安定性が低下するため望ましくない。 If the basicity of the steelmaking slag, that is, CaO / SiO 2 (mass ratio) is less than 2, the amount of Ca elution is drastically reduced, and the influence of surrounding disturbing anions may not be absorbed. From this viewpoint, a more preferable CaO / SiO 2 (mass ratio) is 3 or more. On the other hand, when the CaO / SiO 2 (mass ratio) of the steelmaking slag is 5 or more, although there is no influence on the reduction effect, the amount of free CaO in the slag will remain, and the volume stability of the soil will decrease. Therefore, it is not desirable.
図４に、製鋼スラグのＣａＯ／ＳｉＯ２（質量比）とＣａ溶出量との関係を調査した結果を示す。この試験では、トータルＦｅ含有量が２０質量％、ＦｅＯ含有量が１５質量％、金属Ｆｅ含有量が１．０質量％の製鋼スラグについて、ＣａＯ／ＳｉＯ２（質量比）を１．２〜４．２の範囲で変化させ、Ｃａ溶出量を調査した。Ｃａ溶出量は、製鋼スラグ１質量部に対して水を１０質量部添加し、２００ｒｐｍで６時間振とうした後、メンブランフィルターでろ過したろ液を用いて評価した。
図４によれば、製鋼スラグからのＣａ溶出量は、スラグのＣａＯ／ＳｉＯ２（質量比）が２以上となると急増し、特に３以上となると顕著に増加している。このように十分なＣａ溶出量が確保されることにより、妨害性のアニオンや吸着による効果の低下が防止され、ＦｅＯや金属Ｆｅによる還元効果を有効に発揮することが可能となる。
Figure 4 shows the results of investigating the relationship between CaO / SiO 2 (weight ratio) and Ca elution of steelmaking slag. In this test, CaO / SiO 2 (mass ratio) was 1.2-4 for steelmaking slag having a total Fe content of 20% by mass, a FeO content of 15% by mass, and a metal Fe content of 1.0% by mass. The amount of Ca elution was investigated by changing the range of .2. The amount of Ca elution was evaluated using a filtrate filtered with a membrane filter after adding 10 parts by mass of water to 1 part by mass of steelmaking slag and shaking at 200 rpm for 6 hours.
According to FIG. 4, the Ca elution amount from the steelmaking slag increases rapidly when the CaO / SiO 2 (mass ratio) of the slag becomes 2 or more, and particularly increases when it becomes 3 or more. By securing a sufficient Ca elution amount in this way, it is possible to prevent a decrease in the effect due to the disturbing anions and adsorption, and to effectively exhibit the reduction effect due to FeO or metal Fe.
図５に、トータルＦｅ含有量が２２質量％、ＦｅＯ含有量が２０質量％、金属Ｆｅ含有量が１．０質量％であって、ＣａＯ／ＳｉＯ２（質量比）が異なる製鋼スラグを用いて、６価クロム低減効果（６価クロムの還元率）を調査した結果を示す。この試験では、クロム標準液を用いて、６価クロム濃度を０．５ｍｇ／Ｌに調整し、これを土壌に１０質量％添加した。この土壌質量：１に対して製鋼スラグを質量比で０．５の割合で混合し、これを１日静置した後、環境庁告示第４６号法で６価クロム溶出試験を行い、６価クロム還元率（還元後の６価クロム量／還元前の６価クロム量）を調べた。
図５によれば、製鋼スラグのＣａＯ／ＳｉＯ２（質量比）によって６価クロムの還元効果が変化し、ＣａＯ／ＳｉＯ２（質量比）が２以上で有効な還元効果が得られ、特に３以上で顕著な還元効果が得られている。
FIG. 5 shows a steelmaking slag having a total Fe content of 22 mass%, an FeO content of 20 mass%, a metal Fe content of 1.0 mass%, and different CaO / SiO 2 (mass ratio). The results of examining the hexavalent chromium reduction effect (reduction rate of hexavalent chromium) are shown. In this test, the hexavalent chromium concentration was adjusted to 0.5 mg / L using a chromium standard solution, and 10% by mass was added to the soil. Steel soil slag was mixed at a mass ratio of 0.5 with respect to this soil mass: 1 and allowed to stand for one day. Then, a hexavalent chromium elution test was conducted by the Environmental Agency Notification Method No. 46. The chromium reduction rate (the amount of hexavalent chromium after reduction / the amount of hexavalent chromium before reduction) was examined.
According to FIG. 5, the reduction effect of hexavalent chromium by the steelmaking slag CaO / SiO 2 (weight ratio) changes, CaO / SiO 2 (weight ratio) is effective reducing effect is obtained in 2 or more, particularly 3 The remarkable reduction effect is acquired by the above.
本発明で使用される製鋼スラグとしては、例えば、転炉スラグ（脱炭スラグ）、溶銑予備処理スラグ（脱燐スラグ、脱硫スラグ、脱珪スラグなど）、電気炉スラグなどが挙げられるが、これらに限定されるものではない。
製鋼スラグの粒度も特に限定されるものではないが、還元反応に関与する接触面やＣａ溶出の促進のための比表面積を確保するという観点から、通常、最大粒径が１０ｍｍ以下に破砕若しくは篩分けにより粒度調整されたものが望ましい。
本発明で規定する製鋼スラグの組成条件は、例えば、ＣａＯ／ＳｉＯ２（質量比）については、精錬中の副原料（石灰、珪石等）の調整などにより、また、トータルＦｅ含有量、ＦｅＯ含有量および金属Ｆｅ含有量については、製鉄操業時の酸化鉄の添加条件や酸素吹きの条件の調整、磁選条件の調整、冷却条件の調整などにより、それぞれ実現することができる。
Examples of the steelmaking slag used in the present invention include converter slag (decarburization slag), hot metal pretreatment slag (dephosphorization slag, desulfurization slag, desiliconization slag, etc.), electric furnace slag, etc. It is not limited to.
The particle size of the steelmaking slag is not particularly limited, but is usually crushed or sieved to a maximum particle size of 10 mm or less from the viewpoint of securing a contact surface involved in the reduction reaction and a specific surface area for promoting Ca elution. Those whose particle size is adjusted by dividing are desirable.
The composition conditions of the steelmaking slag specified in the present invention include, for example, CaO / SiO 2 (mass ratio) by adjusting the auxiliary raw materials (lime, silica, etc.) during refining, and the total Fe content, FeO content The amount and the metal Fe content can be realized by adjusting iron oxide addition conditions and oxygen blowing conditions during ironmaking operations, adjusting magnetic separation conditions, adjusting cooling conditions, and the like.
本発明の土壌改良材は、上述したような組成の製鋼スラグに、さらに、未エージングの高炉徐冷スラグを混合したものでもよい。改良の対象となる土壌は、条件によって反応性が異なり、特に酸性側になる土壌では金属Ｆｅ、ＦｅＯによる還元反応が有効に作用しにくくなる場合がある。このような土壌に対して、製鋼スラグに未エージングの高炉徐冷スラグを混合した土壌改良材を適用した場合、多硫化物やチオ硫酸などの還元性材料が供給され、安定した還元能力が発揮される。 The soil improvement material of the present invention may be obtained by further mixing unaged blast furnace chilled slag with steelmaking slag having the above-described composition. The soil to be improved has different reactivity depending on the conditions. In particular, in the soil on the acidic side, the reduction reaction by the metal Fe and FeO may not be effective. When such a soil is applied with a soil improvement material in which steelmaking slag is mixed with unaged blast furnace chilled slag, reducing materials such as polysulfide and thiosulfuric acid are supplied, and stable reduction capability is demonstrated. Is done.
ここで、高炉徐冷スラグのエージングとは、ＪＩＳ−Ａ５０１５「鉄鋼スラグ路盤材」に規定されるものであり、未エージングの高炉徐冷スラグとは、破砕後のエージング期間が６ヶ月に満たないものである。
このように高炉徐冷スラグとして未エージングのものを用いるのは、未エージングの高炉徐冷スラグからは多硫化物やチオ硫酸イオンが浸出するのに対し、大気中でエージングを進めた高炉徐冷スラグでは表面から硫化物の酸化が進み、硫酸塩（ＳＯ４ ２−）に変わり、還元能力が大きく低下してしまうためである。
Here, aging of blast furnace slow cooling slag is defined in JIS-A5015 “Steel Slag Subbase Material”, and unaged blast furnace slow cooling slag has an aging period after crushing of less than 6 months. Is.
As described above, unaged blast furnace slag is used for blast furnace chilled slag that has been aged in the atmosphere while polysulfides and thiosulfate ions are leached from unaged blast furnace chilled slag. This is because in the slag, the oxidation of sulfide proceeds from the surface and changes to sulfate (SO 4 2− ), and the reducing ability is greatly reduced.
高炉徐冷スラグの粒度は特に限定されるものではないが、表面積が大きいほど還元性物質が土壌に供給されやすくなる。このため粒径１０ｍｍ以下の割合が９０質量％以上、より望ましくは、粒径５ｍｍ以下の割合が９０質量％以上である粒度を有することが好ましい。
未エージングの高炉徐冷スラグは、還元能力は高いものがより望ましい。特に、水：スラグ＝１０：１の質量部割合で水と混合し、２００ｒｐｍで６時間振とう後、ろ過したときのチオ硫酸イオンの浸出量が３０ｍｇ／Ｌ以上となる高炉徐冷スラグを用いることが好ましい。チオ硫酸イオンは、還元剤として知られるイオンであるが、高炉徐冷スラグに含まれる硫黄成分が一部酸化された状態で溶出してくる。チオ硫酸イオンの浸出量が３０ｍｇ／Ｌ未満の高炉徐冷スラグでも効果は期待できるが、妨害性のアニオンなどの影響に対して安定した還元効果を得るためには、チオ硫酸イオンの浸出量が３０ｍｇ／Ｌ以上のものが望ましい。
The particle size of the blast furnace slow-cooled slag is not particularly limited, but the reducing material is more easily supplied to the soil as the surface area increases. For this reason, it is preferable to have a particle size in which the ratio of the particle size of 10 mm or less is 90% by mass or more, more desirably, the ratio of the particle size of 5 mm or less is 90% by mass or more.
The non-aging blast furnace slow cooling slag preferably has a high reducing ability. In particular, a blast furnace slow-cooled slag is used that is mixed with water at a mass part ratio of water: slag = 10: 1, shaken at 200 rpm for 6 hours, and filtered to have a thiosulfate ion leaching amount of 30 mg / L or more. It is preferable. The thiosulfate ion is an ion known as a reducing agent, and is eluted in a state in which the sulfur component contained in the blast furnace slow cooling slag is partially oxidized. Although the effect can be expected even with blast furnace slow cooling slag having a leaching amount of thiosulfate ions of less than 30 mg / L, in order to obtain a stable reduction effect against the influence of interfering anions, the leaching amount of thiosulfate ions is Those of 30 mg / L or more are desirable.
製鋼スラグに対する高炉徐冷スラグの配合量は特に限定しないが、ｐＨが４未満になるような土壌に適用する場合には、製鋼スラグ＋高炉徐冷スラグ中で２０質量％以上配合するのが望ましい。高炉徐冷スラグの配合量の上限は特にないが、余剰Ｓが発生すると、低ｐＨ土壌では極微量ではあるものの硫化水素が発生する可能性があり、このため、好ましくは製鋼スラグ＋高炉徐冷スラグ中で５０質量％未満であることが望ましい。
本発明の土壌改良材は、６価クロム以外にも、アンモニアやＰＣＢ、トリクロロエチレンといった有機塩素化合物等の浄化効果も期待できる。
The blending amount of the blast furnace slow cooling slag with respect to the steelmaking slag is not particularly limited, but when applied to soil where the pH is less than 4, it is desirable to blend 20 mass% or more in the steelmaking slag + blast furnace slow cooling slag. . There is no particular upper limit on the amount of blast furnace slow cooling slag, but if surplus S is generated, hydrogen sulfide may be generated although it is extremely small in low pH soil. For this reason, steelmaking slag + blast furnace slow cooling is preferable. It is desirable that it is less than 50% by mass in the slag.
In addition to hexavalent chromium, the soil improvement material of the present invention can be expected to have a purification effect on organic chlorine compounds such as ammonia, PCB, and trichlorethylene.
本実施例では、製鋼スラグとして、脱炭スラグと脱燐スラグを用いた。高炉徐冷スラグは、高炉から出されたスラグを放流・徐冷して得られたスラグである。各スラグをヤードに放流して冷却後、クラッシャーで破砕し、条件にあわせて粒度を整えて使用した。
製鋼スラグの組成のうち、金属Ｆｅ含有量は磁選の条件を選択することで調整し、ＦｅＯ含有量は製鉄操業時の酸化鉄の添加条件や酸素吹きの条件を選択することで調整し、トータルＦｅ含有量は磁選条件（磁場の強さ、距離など）を選択することで調整し、それぞれ分析値をもとに適用した。また、ＣａＯ／ＳｉＯ２（質量比）は、副原料添加量を管理し、得られたスラグを選択することで調整し、分析値をもとに適用した。
In this example, decarburized slag and dephosphorized slag were used as the steelmaking slag. Blast furnace slow-cooled slag is slag obtained by discharging and slowly cooling slag discharged from the blast furnace. Each slag was discharged to the yard, cooled, crushed with a crusher, and used after adjusting the particle size according to the conditions.
Of the composition of steelmaking slag, the metal Fe content is adjusted by selecting magnetic separation conditions, and the FeO content is adjusted by selecting iron oxide addition conditions and oxygen blowing conditions during ironmaking operations. The Fe content was adjusted by selecting magnetic separation conditions (magnetic field strength, distance, etc.), and each was applied based on the analysis value. In addition, CaO / SiO 2 (mass ratio) was adjusted by controlling the amount of auxiliary raw material added and selecting the obtained slag, and applied based on the analysis value.
土壌改良材の添加量を３質量％とした条件で、環境庁告示４６号法による溶出試験方法に基づく溶出試験を行い、６価クロムの溶出量を測定した。対象の土壌としては、６価クロムの溶出抑制効果を阻害すると言われる火山灰質粘性土のセメント改良土を用いた。試験は、土壌に土壌改良材を３質量％添加して十分撹拌した後、３日間静置してから溶出試験を行った。その結果を、土壌改良材の構成とともに表２に示す。
なお、表２に示す溶出試験の評価は以下の通りである。
○：６価クロムの検出下限値（０．０３ｍｇ／Ｌ）未満
△：６価クロムの溶出値が０．０３ｍｇ／Ｌ以上、０．０５ｍｇ／Ｌ以下
×：６価クロムの溶出値が０．０５ｍｇ／Ｌ超
表２によれば、本発明の土壌改良材では、いずれも６価クロムの溶出量が基準値以下に抑えられている。
An elution test based on the elution test method by the Environment Agency Notification No. 46 method was conducted under the condition that the amount of the soil improvement material added was 3% by mass, and the elution amount of hexavalent chromium was measured. As the target soil, a cement-modified soil of volcanic ash clay that is said to inhibit the elution suppression effect of hexavalent chromium was used. In the test, 3 mass% of the soil conditioner was added to the soil, and after sufficient stirring, the sample was allowed to stand for 3 days and then the dissolution test was performed. The results are shown in Table 2 together with the structure of the soil improvement material.
The evaluation of the dissolution test shown in Table 2 is as follows.
○: Less than the lower limit of detection of hexavalent chromium (0.03 mg / L) Δ: The elution value of hexavalent chromium is 0.03 mg / L or more and 0.05 mg / L or less ×: The elution value of hexavalent chromium is 0.00. More than 05 mg / L According to Table 2, in the soil improvement material of the present invention, the elution amount of hexavalent chromium is suppressed to a reference value or less.
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