WO2001058611A1

WO2001058611A1 - Method for manufacturing soil fixing agents and using the agents to fix the soil

Info

Publication number: WO2001058611A1
Application number: PCT/IB1999/001583
Authority: WO
Inventors: Yukoh Akae; Kazuo Kote
Original assignee: Yukoh Akae; Kazuo Kote
Priority date: 1999-10-11
Filing date: 1999-10-11
Publication date: 2001-08-16

Abstract

A fixing agent having characteristics of permeability and impermeability as part of conditions for fixation and also improved strength and tenacity to make a fixing agent having strong saltwater resistance, in comparison with the conventional fixing agents such as cement. Polluted soil is solidified first to utilize it as the solidified soil material and thereafter upon neutralizing and stabilizing hazardous metals by turning it into an insoluble substance.

Description

METHOD FOR MANUFACTURING SOIL FIXING AGENTS AND USING THE AGENTS

TO FIX THE SOIL

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention provides fixing agents that have new characteristics related to the creation of permeable and impermeable strata for use in construction work. The fixing agents manufacture soil-like material having characteristics such as strength, tenacity, heat and saltwater resistance. Polluted soil due to secondary pollution (hazardous substances contained in the incinerated ashes and hazardous waste disposed from chemical plants, such as transformer fluid and other reagents) is continuously stabilized and neutralized and converted to solidified soil material that is insoluble to water, the soil so fabricated used in a manner to prevent environmental pollution.

2. Description of the Prior Art

The fixation method has been conventionally thought of as the separation of organic and inorganic compounds; and the treatment and fixation method using zeolite mainly for inorganic compounds

(making alkaline soil by using chloride) . Also known is a method using bentonite for temporarily fixing soft soil. However, fixing agents (conventional cement, etc.) have been used solely for fixation.

Therefore, secondary pollution caused by fixation has never been discussed and set aside as a separate issue. For instance, secondary pollution from the use of bentonite is one of such examples .

SUMMARY OF THE INVENTION

The present invention provides a fixing agent having characteristics of permeability and impermeability as part of conditions for fixation and also improved strength and tenacity to make a fixing agent having strong saltwater resistance, in comparison with the conventional fixing agents such as cement. Moreover, the present invention is based on the concept that polluted soil is solidified at first to utilize it as the solidified soil material and thereafter upon neutralizing and stabilizing hazardous metals by turning it into an insoluble substance.

As to the fixation of soft soil by using fixing agents, five issues are to be resolved as listed (1) through (5) below: (1) The screening of soft soil grain, in other words, the finer the grain is, the more complicated the methods and procedure become; (2) It is necessary to know the content and variety of other substances contained in soft soil, especially organic substances; (3) It is necessary to take care of inhibitory factors for the reactions in fixing soft soil as pre-treatment, such as ionization, substitution, formation of complex salt, and the like; (4) Pre-treatment is the separation of substances having hydrocarbon group such as fatty acids, organic substances, and the like. The separation itself promotes re-crystallization of oxidized metals (such as aluminum oxide A1203, silicate Si02, magnesium oxide etc.) that are contained in soil grains. (5) The characteristics of soft soil are the presence of organic and inorganic substances mixed together regardless of water content. Moreover, depending on the size of soil grain, the colloid state may vary.

Using the above (1) through (5) as requirements, fixation is performed. The treatment technique employed here is basically one using a continuous process. Moreover, at the final step, further fixation by utilizing the characteristics of graphite is provided, as is treatment for the prevention of solubilization of hazardous substances into water such as hazardous metal ions, etc.

By resolving the above-mentioned issues, through the decomposition and condensation of the generated fatty acids, the fixation can be completed in a solid but soft state. Moreover, due to part of silicon action, a rock structure is formed and agglomerated, and part of metal ions are to be gradually adsorbed onto silicon as it grows. In addition, depending on the type of graphite inter-layer compound, fixation will be performed by sealing heavy metals and metal complex.

Using specific ion exchange substances the present invention provides the following: (A) Isolation and re-crystallization of organic and inorganic substance; (B) Targeting the adsorption of metal ions in soil by using specific silicon salt; (C) Integration of inorganic compounds in soil by making them into complex and coordination bonding compounds; and (D) Fixation of inorganic compounds with specific solvents.

Regarding item A, the fundamental nature of soft soil is one of the molecular constituents of soil. Metal oxides, such as aluminum oxide, silicon oxide, calcium oxide, and the like, exist in a simple substance and crystal form and turn into a form sensitive to ionization as these oxides become finer grain. In addition to the above, there are phenol group, methoxyl group, and non-crystalline allophone in the soil. Furthermore, various organic substances from the decay of plant bodies, various forms of organic substances (lignin) from the decomposition of plants, organic metal, aromatic metal compounds, and organic ester compounds may be found. When promoting the bonding between soil grains, the existence of these organic substances will become a major factor blocking bonding. On the other hand, not knowing how and through what kind of process these organic and inorganic hazardous substances have been mixed, fatty acids and esters, halogenated compounds, semi-metals (P, As, Sb, Bi) compounds, and the like are contained in soil. Depending on the location where soft soil exists, the mixing ratio of these hazardous substances varies, and the quantification of mixing rations does not have significant meaning. Therefore, it is necessary to neutralize (crystallize) and re-crystallize organic and inorganic compounds, which are the factor blocking bonding for fixation, in order to solidify these mixed substances in a more stable manner. Regarding item B, silicate used in the invention means alkaline salt. In other words, poly acid negative ions formed in a sodium silicate solution will form ion crystals by adsorbing aluminum, iron (II) , calcium, magnesium ions and oxides. Regarding item C, a series of reactions including adsorption and crystallization of organic compounds, substitution with inorganic compounds, forming complex compounds through coordination bonding, bonding with organic metals and semi-metals through isolation and substitution and the like will take place continuously by applying (Solvent 2) (electron exchanger) to be used in the invention is indicated.

Regarding item D, graphite will form an inter -layer compound that has reactants inserted in between layers through electron charge transfer reaction with sulfuric acid, nitric acid, sodium, potassium, halogen, sulfide, oxide, and the like. By utilizing such properties, various diazonium salt, alkyl sulfonic acid salt, halogenated compounds, and the like can form and fix inter-layer compounds at the same time.

The present invention provides means for the decomposition and fixation of fatty acids based on the reaction described hereinabove and the environmentally-safe fixation of the factor of polluted soil, in other words, semi-metals that tend to become hazardous sources (arsenic, phosphorus, antimony, and the like) . Moreover, the invention provides means for the reduction and stable fixation of hexavalent chromium as well as the separation of organic mercury.

The requirements set forth in (A) through (D) hereinabove more completely is to adjust the mixing ratio and stirring times of the solvents specified herein. In other words, depending on the amount and variety of hazardous substances, a longer stirring time may be appropriate. A 15-minute stirring time typically is used for each step (approximately 30 minutes for stirring of graphite is used) . On the other hand, as the heat source required for the condensation of alkyl sulfonic acid salt, heat of exothermal reaction of calcium oxide, which was used for stable fixation of heavy metals, was employed instead of an outside heat source.

Based on the above-mentioned methods and ideas, it is desired to separate solid and liquid phase in order to resolve the existing issues.

DESCRIPTION OF THE PRESENT INVENTION

Assuming the fixation of common soil, the types and form of soil varies considerably. Therefore, the present invention, is designed to be applicable for a wide range of soil .

Based on the above-mentioned reasons, the form of soil is classified as shown below and explained in order. Classification of Soil Forms: (1) Humus soil and clay state, soil grain size ranging from 2^"6 mm or smaller;

(2) Silt state, soil grain size ranging 2^'6 ~ 2 mm; (3) Sand and gravel, soil grain size ranging 2 - 22 mm.

Items (1) and (2) may be considered as the main body of difficult work. Although it is very difficult to solidify them since water content is rather high, from another aspect, they tend to retain the elements of the 15th group of the periodical table, or the factors of environmental pollution such as arsenic, phosphorus, and antimony compounds, and at the same time the heavy metal compounds (chromium, lead, zinc, etc.) as noted as pollutants. From the viewpoint of fixation, (l) , (2), and (3) can be separated, but from the viewpoint of treatment, all can be handled by the same technique. Therefore, as the embodiment, the sample belonging to (1) is chosen and the fixation and treatment for environmental pollution is implemented together. Hereafter, the sample serves as the raw mixture and the details are given hereinbelow.

Sample: Soil of Class B River Bed, Clay-like soil; Water content 80%, pH 5.6; Substances contained: Saturated and unsaturated inorganic fatty acids, clay, heavy metal compounds (lead, chromium, zinc, etc.), semi-metal compounds (lead, antimony, arsenic, etc.) . The existence of ammonium was recognized because of the odor.

The first step: The agent to be used is (Solvent 1) sodium silicate (NaSi04) ; (Solvent 1) solution is mixed with the sample. The mixing ratio of the solvent is about 10 wt% to the sample. The purpose at this point is to decompose lower fatty acids and fatty acid esters contained in the sample. The reactions in the process are shown by Formulas 1, 2, and 3 (appendix A) . In addition, silicate ion formed through these reactions will adsorb metal oxides (aluminum, iron, manganese, etc.) contained in the sample and mercury will be adsorbed by silicate ion formed as shown by Formula 3. Thereafter, they will be crystallized as new orthosilicate salt. What is meant by these reaction formulae is the existence of soda alkaline solution formed by the hydrolysis of sodium silicate as shown by Formula 1 which promotes decomposition and crystallization of alkyklated compounds and esters. In other words, sodium silicate acts as the catalytic role and the promoter of substitution, and silicate ion adsorbs simple substance metals. On the other hand, in order to condense alkylated salt more effectively, heating is required, which will become more obvious when mixing with calcium oxide at the third step. Due to the alkylation of solvent, fatty acid esters will be hydrolyzed to form alkylated salt made of alcohol and acid (Formula 2) . Mercury existing in the form of organic mercury will be isolated in an alkaline solution and adsorbed by silicate ion and subsequently solidified (Formula 3) .

In addition, the generation of silicate ion will result in binding with iron (II) , magnesium oxide, and the like and the formation of orthosilicate salt (Formula 4) (Formula 5) . The mixing of (Solvent 1) requires an approximately 10-minute long stirring time. Then (Solvent 2) is added and stirred.

The present invention at this point provides the following features: By adding (Solvent 3) , to utilize the amino group as the electron donor; 2) Turning the solution into alkaline means the freeing of carboxyl group, alkyl group held by phenol compounds, and hydrocarbon group, which are originated from humus/decayed substance abundantly contained in the solvent; 3) Moreover, for the substitution with soil grain bonding, metal-metal bonding, and metal compounds, it acts to ionize (separate) allophanic acid (H2NCONH-COOH) existing as the blocking factor of the reaction,- 4) The ionization of allophanic acid means the separation of (-CO-NH-) that is bonding through coordination in the center to form (-C0-NH-) group by electron transfer, which adsorbs other hydrocarbon group (CH--) and metal oxide; 5) Along with the diazonation of aromatic primary amine, especially, through the substitution for semi-metals (arsenic, bismuth) compounds, these diazonium ions will have some effects in the fixation of semi-metal compounds. In addition, diazonium ion will become adsorbent of the hydrocarbon group.

That is to say, the major ingredients of soil grain, aluminum and silicon, will be negatively charged and crystallized by mixing with Solvent 1 and 2. As set forth hereinabove, various metal complex salts so formed will form further bonding to become double salt. Then, heavy metals adsorbed by phenol that is abundantly contained in soil will be crystallized by repeating the substitution and bonding with aluminosilicate and silicon oxide, which are charged through the action of Solvent 2 and 3 as the electron donor.

As stated hereinabove, for colloid formation in the sample soil, the existence of allophanic acid and compounds having methoxyl group, which are contained in it, is the major blocking factor. Therefore, the ionization of allophanic acid and that of methoxyl group held by lignin will promote the condensation and fixation of colloidal soil to further extent.

After adding Solvent 2 and stirring sufficiently, a sitting time is set to complete the reaction (typically 20 minutes in the embodiment described) .

That is, at this point, metal-metal bonding, coordination, and condensation of double salt, complex salt, diazonium salt, and the like appeared through the substitution of metal ions for the first time. _At the same time, the condensation (the formation of alkyl sulfonic acid salt) takes place due to the hydrolysis of fatty acid ester and unsaturated fatty acid and the formation of alcoholate.

The second step: The agent to be used is 2-naphthol-4- sulfonic acid (Solvent 3) . Subsequently, Solvent 3 is mixed and stirred. The purpose at this point is to utilize hydroxyl group of the sulfonic acid group.

That is, the sulfonification of various allyl alcohols formed in the first step. Namely, crystallization of alkyl sulfonic acid salt, shown by Formula 8. Allyl alcohol that has unsaturated hydrocarbon such as phenyl group, tollyl group, and the like, and part of methane series alcohol are oxidized to turn into alkane (CnH2n+2) with hydrogen ion and hydrogenated halogen via alkan (CnH2n) (Formula 11) with the presence of potassium sulfonate. The alkan that has a tendency of polymerization will become very stable ethylene gas or liquid. (Formula 11) . On the other hand, the formation of allyl complex will start through the bonding of allyl group (CH=CH-H2-) with metal atoms. The allyl group has hapto I (sig a-allyl group) and hapto III (pie-ally1 group) types. Magnesium and zinc form hapto I type, complex salt, with transition elements (Sc, V, Cr, Mn, Fe, Co, Ni, Cu) and the element having 3d shell and 4d shell (39Y ~ 47Ag) , etc. As to the type where allyl group bonded with metal atoms having 3d shell, there are examples of the formation of such compounds, for instance, [M(C3Hs)₃, where M: Cr, Fe, Co] , [M(C3Hs)₂, where M: Ni, Pb] , and [CO (CO) (C3HB) , TKC₃H₅) (C3H₅)₂] that is mixed with other coordinates.

These heavy metal complexes are generated from what is in the soil due to the function of soil colloid as the positive ion exchanger by making solvent pH larger. In addition, it is the complex formed through reduction and substitution of heavy metal oxide mixed in the solution. Further, such heavy metals are heavy metal oxides mixed into the sample for some reason, and they are formed through catalytic action of electron exchanging groups held by Solvent 2 and Solvent 3.

On the other hand, aluminosilicate salt as the major ingredient of soil is water-soluble and becomes as shown in Formula 8 containing [Al (H2O) β] + in solution (in solvent). After further hydrolysis, it will become as shown in (Formula 9) , resulting in the deposit of colloidal aluminum hydroxide. By making alkaline solution, the Al(OH)3 will form complex with metal oxide ion as shown with the general formula [xMiΛOy isOs-z H2O] . That is aluminate (Ml: alkaline metal) (Formula 10) .

Aluminum hydroxide will generate halogenated compounds, silicate, and the like, and especially hydrate of halogenated compounds will form aqueous complex. The speed of exchanging water molecules to which aqueous complex is coordinated may vary depending on the process and the oxidation number of center metal elements. There is polynucleous complex having chromium as the center atom. Polynucleous complex is [ (H2O) ₄Cr (OH) 2-Cr (H2O) 4] ₄+.

The third step: After stirring sufficiently at the second step and leaving sitting for approximately 30 minutes, calcium oxide (_Solvent 4) is added. The purpose at this point is as shown by Formula ₁5, to raise temperature of the sample along with the exothermal reaction. In other words, the exogenous energy is used for the promotion of the reactions shown by Formula 2 and Formula 6.

For fixing the sample in this manner, the conditions good for the fixation of the sample were obtained through the separation (ionization) of fatty acids and allofate as well as alkyl sulfonic acid salt, etc. that are the blocking factors of soil grain bonding and metal-metal bonding. Under these conditions, various complex were formed through various reactions such as substitution and coordination bonding. Among these condensates (crystals) , those having strong deliquescence such as diazonium salt, alkyl sulfonic acid salt, and the like are included.

Subsequently after sufficient stirring, and allowing an additional 30-minute sitting time and separating deposit and solution through filtration, it is possible to neutralize such deposit as well as to turn it into filling body of soil. If arsenic and arsenic compounds are found in the sample, considering product of arsine (AsH3) , it is necessary to place the Solvent 3 solution at an outside site of the treatment facility in advance to adsorb arsenic using the hydroxyl group.

The fourth step: The use of Solvent 5 that is graphite in a soil crystal form. By using the deposit so formed throughout the process of the invention as the sample, it is possible to manufacture cement having strength, heat resistance, tenacity, and saltwater resistance. Thus, the present invention provides a met_ho_d for both fixation of clay-like soil and a method for manufacturing a new type of cement. In other words, the method of fixation using the graphite agent is a kind of technique used in the method for stable fixation of hazardous metal and semi-metal compounds, which is the formation of inter-layer compounds (water insoluble compounds) with a graphite agent.

In addition, when the sample is in a silt form having grain diameter (2^~6 ~ 2^"4) or that of sand grain size (2^"4 ~ 2) or that of gravel size (2 or larger) , the same procedure will do the same using the same agents. When using the above as the sample, under natural conditions, or in environment, no chemical change appeared due to the change of seasons and temperature, and furthermore, no influence such as hydrolysis from rain and water of other source and solvation and elution of metal compounds took place.

As a result, the following were found: 1) Following the procedure mentioned above, with the solid compounds treated and separated from water solution, no change was found even in the solution using another test sample. In other words, the solution did not turn back into colloid form; 2) Despite being left in water for hours (about 6 hours) , the elution of metal ions were not observed in the solution; 3) As a result of the above, the possibility of the fixation of underground silt stratum in civil engineering work and the formation of banks along rivers and coastlines is possible; 4) It may be applicable to the stabilization of soft and vulnerable ground; and (5) the treated soil could be utilized for the formation of soil to be used as permeable and impermeable layers.

The present invention thus enables soil after the neutralization of polluted soil, or sludge and soil of silt layer, as well as common soil to be solidified. In addition, the present invention provides various characteristics not limited to the use for fixing soil such as water permeability (prevents sand hazard or landslide upon heavy rainfall) ; increased strength by mixing with common cement; the fixing agent allowing manufacture of new cement that is stronger than common cement; heat resistance (heat resistance is better than in common cement) ; and saltwater resistance (since the fixing agent is neutral, it is friendly to coral reef, fish and sea vegetables) .

It should be noted that the present invention is particularly adaptable for treating the material resulting from heating the harmful ashes produced by the high temperature and pressure incinerator disclosed in copending application Serial No. , filed concurrently herewith, and entitled "Method and Apparatus for Decomposing Hazardous Substances using High Frequency Waves to Provide Environmentally Safe Fixation Ashes in an Incinerator" .

While the invention has been described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its essential teachings .

APPENDIX A: FORMULAS

(1) N a , S i 0 3 H , 0 (S i 0 ₄) 2 N a 0 H 2 H

(2) R O C O R + N _a 0 H R O N R C O O H R C O O H + N _a 0 H R 0 C 0 N H - 0

(3) R H g + N a O H H g R N a (0 H)

(4) (S i 0 ,) + 4 H + 2 F C 0 F e ₂ S i 0 ₄ + 2 H ₂ 0

(5) (S i 0 ₄) + 4 H + 2 M g O M g S i 0 ₄ + 2 H ₂ 0

(6) R C 0 0 H + (H S 0 ₃) R 0 C (H S 0 ₃) + (O H)

R C O O H + (N a S 0 ₃) R 0 C (N a S 0 ₃) + (O H)

(7) [A L (H _a 0) ³ + H ₂ 0 [A L (0 H) (H ₂ 0) _s] ² + H ₂ 0

(8) [A L (0 H) (H ₂ 0) _s] ² H ₂ 0

[( H ₂ 0) ₄ A L (μ - 0 H) ₂ A L (H ₂ 0) ₄] ⁴

(9) [(H ₂ 0) ₄ A L (μ - 0 H) ₂ A L (H ₂ 0) ₄ ] A L ₂ (0 H) ₃

(10) (R 0 C 0) ₂ P b + 2 A r N H ₂ S 0 ₃ H

P b (S 0 ₃ H) ₂ + 2 A r N H (C 0) + H ₂ 0 (11) R 0 H + (S 0 ₃ H) H

(12) C H ₃ = C H C H ₂ 0 H (alpali aq) C H ₂ = C H C H O

(13) C H ₂ = C H C H O (OXIDATION) C H ₂ = C H C O O H

(14') C H ₂ = C H C O O H (POLYMERIZATION) ( C H ₂ - C H) _n

C 0 0 R

(15) C a O + H ₂ 0 C a (O H) ₂ + 1 5. 2 k c a l

Claims

WHAT IS CLAIMED

1. A method for neutralizing and detoxifying polluted soil due to secondary pollution comprising the steps of preparing fixing agents; and introducing said agents to said soil thereby stabilizing fixing said soil.

2. The method for fixing soil through crystallization of various metal ions, metal complex, halogenated compounds, sulfide and the like with graphite material as well as said solvents for fixing.

3. The method of claim 1 wherein said solvent is selected from the group consisting of potassium silicate and sodium silicate; sodium l-naphthylamine-4-sulfonate; 2-naphthol-4-sulfonic acid derivatives of naphthol; calcium oxide and calcium hydroxide (hydride lime) ; and graphite (in a soil crystal form) .