CZ303353B6 - Method of fixing toxic substances in alumosilicate polymer matrix - Google Patents

Abstract

The present invention relates to a method of fixing toxic substances in alumosilicate polymer matrix, said polymer containing an alumosilicate substance, an alkali activator Mei2O being present in concentration of 5 to 12 percent by weight based on the weight of the alumosilicate substance, wherein Me represents Na and/or K, in the form of a hydroxide, optionally in the form of water glass with module Ms 0.7 to 3, or a mixture of an alkali hydroxide and water glass, make-up water in the water/alumosilicate substance ratio = 0.1 to 0.6, optionally a filling agent for the production of mortars and concretes. optionally a substance containing Ca, and substances being selected from the group consisting of cations and anions, particularly oxygenic anions of toxic elements particularly from the group consisting of Be, Bi, Cd, Co, Cr, Cu, Nb, Ni, Pb, Sn, Th, U, Y, Zr, whereby the alumosilicate polymer mixed with a toxic material is compacted after mixing by vibration o squeezing and then it is let in an environment with temperature in the range of 20 to 95 degC until solidification and thereinafter the substance is fired to a temperature of 600 to 1100 degC.

Description

Method of fixation of toxic substances in matrix of alumosilicate polymer

Technical field

Basic data on aluminosilicate compounds activated by alkaline compounds can be found in the literature, for example, in the book by VD Gluchovsky: "Soil Silicates", Kiev 1959, then in Proceedings of the 1st and 2nd International Conference "Alkaline Cements and Concretes", Kijey 1994, 1999 and many others. These works describe mixtures of latent hydraulic substances (especially slags and others) where an alkaline activator in the form of water glass, Na ₂ CO ₃ and NaOH is used. Further basic data on these types of substances are given in comprehensive papers such as Geopolymers, Structure, Properties and Industrial Applications, ed, JL Provis and JSJ van Deventer (2009) and J. Davidovits Geopolymer (2009).

In a number of publications, e.g., U.S. Pat. No. 5,084,102, U.S. Pat. No. 5,601,643, WO 00/00447, WO2005 019 130,

WO 03 078 349.

From CZ 289 735, an alkali-activated binder based on latent hydraulically active substances for the production of slurries, mortars and concretes hardening at temperatures of 15 to 95 ° C is known, consisting of 35 to 93 wt. % fly ash with a specific surface area of 100 to 600 m ² / kg, 2 to 50 wt. mineral active substances selected from the group consisting of ground granulated blast furnace slag with a specific surface area of 200 to 600 m ² / kg, and / or ground clinker of Portland cement with a specific surface area of 200 to 600 m ² / kg, and / or natural and / or artificial pozzolan; and / or thermally activated natural clay, and 5 to 15 wt. % of an alkali activator, such as a mixture of sodium or potassium waterglass and NaOH or KOH, expressed as wt. Na ₂ O or K ₂ O, in which the SiO ₂ / Na ₂ O or K ₂ O ratio is from 0.4 to 1.0, optionally containing up to 10 wt. blended Portland cement, such as slag-portland or blast furnace cement.

From CZ 291 443 there is known a binder geopolymic composition curing at temperatures of 15 to 95 ° C, intended for the production of slurries, mortars and concretes consisting of 35.01 to 93.90 wt. 100 to 600 m ² / kg, 0 to 40 wt. % by weight of a guide surface of 200 to 600 m ² / kg, selected from the group consisting of ground Portland cement clinker, blast-furnace granulated slag, 5 to 15 wt. % of an alkali activator, such as a mixture of sodium and / or potassium waterglass and NaOH or KOH, expressed as wt. % Na ₂ O or K ₂ O, with a SiO ₂ / Na ₂ O or K ₂ O ratio equal to 0.1 to 1.0, and 1.1 to 9.99 wt. aluminum additives containing at least 35 wt. Al ₂ O ₃ such as calcium aluminates, aluminous cement clinker, gibbsit, boemite, anhydrous Al ₂ O ₃ , calcined or non-calcined bauxite, clay clay, saliva, aluminum hydroxide, mica, preferably the aluminum additive has more than 50% by weight . particles of less than 60 microns.

From CZ 301 705, cement-free fly ash is known which is produced in such a way that the synthesis of geopolymers takes place by alkaline activation of the fly ash mixture at a temperature in the range of 40 to 80 ° C, preferably by alkaline activator of Na ₂ SiO ₃ up to 12% dry matter by weight of fly ash and sodium hydroxide in an amount of 4 to 8% dry matter by weight of fly ash. To improve the consistency of fly ash concrete, water can be added up to the total water coefficient water in the solutions and the water added, where w is 0.45 to 0.6. The free storage time after mixing the fly ash concrete and the subsequent thermal activation has a positive effect on the strength. The amount of fly ash in relation to the aggregate can be used to control not only the consistency of fresh fly ash concrete, but also its resulting strength and resistance to aggressive environments. A number of published papers show successful fixation of toxic substances containing heavy metals in the matrix of alumosilicate polymers.

Van Jaarsveld JG S, Van Deventer JSJ, Lorenzen L .: The Potential Use of Geopolymeric Materials for Immobilized Toxic Materials ”, Part I., Miner. Eng. 10, 659-669 (1997), Part II, 12, 75-91 (1999)) suggest that the most important factor in the alkaline activation of latent hydCZ 303353 B6 raulins is the Si / Al ratio, respectively. alkali concentration or SiO ₂ / Na ₂ O ratio. This activation produces aluminosilicate inorganic polymers, when Al enters the (Si-O-Si) n structure and creates a new structure (Si-O-Al-O-Si) ) _n . this matrix is suitable for fixing a number of heavy elements.

DE 3 934 085 discloses a binder for the immobilization of heavy metal waste consisting of latent hydraulic substances (slag, fly ash and others) having a particle size of less than 100 µm, an alkaline activator based on CaO, Ca (OH) ₂ , MgO, Mg ( OH) ₂ , and CaSO ₃ or CaSO ₄ . EP 593130 discloses a process for immobilizing heavy metal wastes using a binder consisting of fly ash, an alkaline activator solution and a pH greater than 13, optionally containing slag, silica drift or other pozzolans.

JP8 301 639 describes a process for solidifying toxic materials in a mixture of waste ash and water glass.

WO 8 902 766, US 5 539 140, US 4 859 367 (J. Davidovits) discloses a composition of an alumosilicate polymer suitable for fixing waste materials based on an alkali-activated starting material, metakaolin (a thermally activated kaolinitic material).

EP 1 864 299 discloses a method of fixing radioactive materials in a matrix based on a geopolymeric (alumosilicate) precursor. This method of silicification enables the preparation of monolithic bodies which are suitable for the storage of radioactive waste.

DE 3528054 A1 (Dumont E) discloses a method of fixing toxic substances in a water glass matrix and oxides or alumosilicates which are mixed with water glass and formed into bodies, for example pellets, which can then be coated with another water glass and reconstituted with water. temperature up to 1200 ° C.

From the literature "Coal fly ash-slag-based geopolymers: Microstructure and metal leachng", Journal of Hazardous Materials

Maria Izquierdoa, Xavier Querol, Joseph Davidovits b, Diano Antenuccic, Henk Nugterend, Constantino Femandez-Pereira, or "Geopolymers for Immobilization of Cr (6+), Cd (2+), and Pb (2+)" Zhang J , Provis JL, Feng D, van Deventer JS, J Hazard Mater. 2008 15; 157 (23): 587-98 and our extensive experiments (eg Škvára F., Minaříková M .: "FIXATION OF HEAVY METALS IN GEOPOLYMERIC MATERIALS BASED ON BROWN COAL FLY ASH", Ceramics - Silicates 50 (4) 200-207 ( However, it appears that the possibilities of fixing toxic substances in the matrix of alumosilicate polymers (geopolymers) are limited in some way.

The structure of aluminosilicate polymers contains 2 and 3 dimensional chains (Si-O-Al-O-SiV, where the negative charge on the Al atom is usually compensated by the cation Me ⁺ or Me ²⁺ (Na, K, or Ca). (eg Zn ²⁺ , Pb ²⁺ , Cu ²⁺ , Zr ⁴⁺ ) can also compensate for the negative charge on the Al atom, which is then strongly ionically bound in the alumosilicate polymer matrix and their leachability from this matrix is very low. In many cases, the leachability of these elements is below the hygienic standards, making this alumosilicate matrix suitable for solidification of toxic elements.If the ion radius of atoms of toxic elements such as Cs is too large for space in the alumosilicate matrix structure, their leachability increases and can Trivalent cations such as Cr are more tightly bound and their leachability is lower.

The main limitation for the fixation of toxic elements in the alumosilicate matrix is for elements that occur in the form of oxygen anions, such as CrO ₄ ² C? O? ^2- , AsO ₄ ³ ', AsOf et al., Anions with a negative charge cannot equalize the negative charge on the AL atom. The negative charge on the oxygenous ones or those is counterbalanced by the present alkaline cations. These elements (toxic) are present in the matrix of the alumosilicate polymer in the form of soluble alkali salts and are not bound by any chemical bond. The leaching of the elements in the non-ionic form is then controlled by diffusion and the leachability values! they often go well beyond hygiene standards. It is particularly problematic

Fixation of Cr ⁶⁺ (chromates, dichromates) and As ³⁺ and As ⁵⁺ (arsenites, arsenates) in the alumosilicate polymer matrix. As. Therefore, fixation of elements such as Cr, As, B, Mo, Se, V and W in the alumosilicate polymer matrix is problematic.

Maximum permissible values of indicators for each leachability class {Leachability classes

Pointer ^! I! mg / l 1 Ha | Iib | III mg / l mg / l mg / l As 0.05 2.5 and 0.2 2.5 Ba 2 30 10 í 30 CD 0.004 0.5 0.1 0.5 Cr total i 0.05 ......... ’..... i 1 ! 7 ¹ 7 .................. Cu ! 0.2 10 5 10 Hg {6,001 1 0.2 0.02 p '' Ni 0.04 4 and jl 4 | Pb 0.05 5 ....... ' and Í5 ’” 1 Coll 0.006 0.5 0.07 θ, 5 and Se 0.01 0.7 0.05 0.7 Žn {0,4 120 5 ^! 20 May Mo 0.05 | 3 ’“ .............-..... and íi ...................... and 3

SUMMARY OF THE INVENTION

Said problem of sufficient fixation of toxic substances in the alumosilicate polymer matrix by mixing alumosilicate substances such as waste power plant fly ash, thermally activated clay substances (metakaolin), an alkaline activator in a concentration of 5 to 12 wt. Me2O (based on the weight of the alumosilicate substance), where Me is Na and / or K, in the form of hydroxide, optionally in the form of a water glass with a modulus Ms of 0.7 to 3, or a mixture of alkaline hydroxide and water glass; water / alumosilicate substance = 0.1 to 0.6, with toxic material containing cations and anions, especially oxygen anions of toxic elements, especially from the group of Be, Bi, Cd, Co, Cr, Cu, Nb, Ni, Pb, Sn, Th, U, Y, Zr, where after mixing the mixture is compacted by vibration or compression and then left in a temperature of 20 to 95 ° C until hardening is solved according to the invention, which consists in burning the mass after the hardening process to the temperature

600 DEG-1100 DEG.

The toxic material may be toxic soil or toxic residues from mining operations.

The atosilicate polymer may optionally contain a filler for the production of mortars and concretes and / or a Ca-containing substance, eg limestone,

Based on extensive experimental work of the authors, it has been found that the leachability of toxic elements, especially elements in the form of oxygen anions (Cr, As, B, Mo, Se, V and W) significantly decreases after firing at higher temperatures. Depending on the firing temperature, the original porous alumosity of the lattice matrix is compacted (sintered) and the toxic (otherwise relatively loosely bound elements) transition to the alumosilicate matrix. The leachability of these elements decreases significantly with the firing temperature. Depending on the firing temperature, it is possible to reach limits for individual prescribed leachability classes in terms of the relevant ME and MH regulations. These firing temperatures range from 600 to 1100 ° C. At 800 to 1000 ° C, even the lowest values prescribed for the lowest leachability classes were achieved. The leachability of toxic elements is further reduced in the presence of Ca-containing substances, eg CaCO ₃ .

The process according to the invention is suitable for fixing (solidifying) toxic materials, toxic soils or toxic residues from mining operations.

Example 1.

Mortars were used for leachability tests (always 4x4x16 cm solids). The composition of the mortar was as follows: water / fly ash weight ratio 0.34 to 0.36, ash / sand ratio 1: 1.5. The mixing water contained NaOH and water glass, where the total Na ₂ O content (calculated on the fly ash weight) was 8 to 10 wt%, the SiO ₂ / Na ₂ O ratio was 1.3 to 1.5. Toxic substances were added to the mixing water or mixed with fly ash as a solid phase. The mortars had good workability, which allowed the compaction of vibrations of 50 Hz. After preparation, the bodies were placed in an oven at 80-90 ° C for 8-12 hours.

Example 2 (prior art control experiment)

The mortar according to Example 1 was subjected to leaching in accordance with the procedures prescribed by the Decree of the Ministry of the Environment No. 294/2005 Coll. and ČSN EN 1247-4, when a water leachate was prepared (24 hours leaching in unionized water). Leaches were prepared repeatedly.

Leachability classes according to ME Decree No. 294/2005 Coll

........ Γ Γ Ha T ..... lib ί ffi '

Element Material can Save landfill 'Inert waste' Material can 1 landfill 'Other waste' Material can ! landfill 'Other waste' subclass Material can be stored landfill "hazardous waste" mg / l and mg / l ί 1 mg / l 1 mg / l ) Cr total not more than 0,05 not more than 7 Not more than 1 j 1 [ i maximum 7 j i ^! . and

-4GB 303353 B6

The content of Cr was determined by absorption atomic spectrometry after 24 hours. The leaches were repeated after another days.

The mortar contained 0.5 wt. Cr in the form of Na ₂ Cr ₂ O ₇ .2H ₂ O.

Extract No Cr (mg / l) Evaluation 1 350 does not comply with any leachability class 2 200 does not comply with any leachability class 3 190 does not comply with any leachability class

Example 3.

The mortar bodies according to Example 2 containing 0.5 wt. Cr (in the form of Na ₂ Cr ₂ O ₇ · 2H ₂ O) was fired to 600, 800 and 1000 ° C after the drying process.

Firing to 600 ° C

Extract No Cr (mg / l) Evaluation 1 19 Dec does not comply with any leachability class 2 22nd does not comply with any leachability class 3 19 Dec does not comply with any leachability class 4 30 does not comply with any leachability class 5 4.7 compliant with Ila. leachability class 6 2.9 complies with Ha. leachability class 7 1,8 compliant with Ila. leachability class 8 2.6 complies with Ha. leachability class

Firing to 800 ° C

Extract No Cr (mg / l) Evaluation 1 0.85 complies with lib. leachability class 2 0.4 complies with lib. leachability class 3 0.35 complies with lib. leachability class 4 0.4 complies with lib, leachability class 5 0.16 complies with lib. leachability class 6 0.1 complies with lib. leachability class 7 -0.07 complies with lib. leachability class 8 0.21 complies with lib. leachability class

Firing to 1000 ° C

Extract No Cr (mg / l) Evaluation 1 -0.04 complies with Class 1 leachability 2 <0.04 complies with Class I leachability 3 <0.04 complies with Class I leachability 4 <0.04 complies with Class I leachability 5 <0.04 complies with Class I leachability 6 <0.04 complies with Class I leachability 7 <0.04 complies with Class I leachability 8 <0.04 complies with Class I leachability

In the process according to the invention, the leachability of Cr has been greatly reduced and complies with the hygienic limits laid down by law.

Example 4.

The mortar of Example 2 contained 1% Cr in the form of chromate. The mortar bodies were fired to 1000 ° C.

Firing to 1000 st.C

Extract No Cr (mg / l) Evaluation 1 -0.04 complies with Class I leachability 2 <0.04 complies with Class I leachability 3 <0.04 complies with Class I leachability 4 <0.04 complies with Class I leachability 5 <0.04 complies with Class I leachability 6 <0.04 complies with Class I leachability 7 <0.04 complies with Class I leachability 8 <0.04 complies with Class I leachability

Cr leachability meets hygienic leachability limits,

Example 5.

The mortar of Example 2 contained 1.5 wt% Cr in the form of chromate. The mortar bodies were fired at 800 and 1000 ° C.

-6GB 303353 B6

Firing to 800 ° C

Extract No Cr (mg / l) Evaluation 1 7.2 does not comply with any leachability class 2 2 complies with lib. leachability class 3 3.1 complies with lib. leachability class 4 0.79 complies with lib. leachability class 5 0.60 complies with lib. leachability class 6 1.46 complies with lib. leachability class 7 0.8 complies with lib. leachability class 8 0.23 complies with lib. leachability class 9 0.16 complies with lib. leachability class

Firing to 1000 ° C

Extract No Cr (mg / l) Evaluation 1 <0.05 complies with Class 1 leachability 2 <0.05 complies with Class I leachability 3 <0.05 complies with L leachability class 4 <0.05 complies with Class I leachability 5 <0.05 complies with Class I leachability 6 <0.05 complies with Class I leachability 7 <0.05 complies with Class I leachability 8 <0.05 complies with Class I leachability

Example 6.

The mortar was prepared as described in Example 1. The mortar contained 0.1 wt. AS2O3.

Extract No As (mg / l) Evaluation 1 32.1 does not comply with any leachability class 2 16.2 does not comply with any leachability class 3 10.8 does not comply with any leachability class

XEN 303353 B6

Example 7.

The mortar was prepared as in Example 1 and the mortar bodies were fired at 600, 800 and 1000 ° C

Firing to 600 ° C

Extract No As (mg / l) Evaluation 1 1.5 compliant with Ila. leachability class 2 -0.6 complies with lib. leachability class 3 0.9 complies with lib. leachability class 4 <0.5 complies with lib. leachability class 5 <0.5 complies with lib. leachability class 6 <0.5 complies with lib, leachability class 7 <0.5 complies with lib. leachability class 8 <0.5 complies with Hb. leachability class

Firing to 800 ° C

Extract No As (mg / l) Evaluation 1 <0.5 complies with Hb. leachability class 2 <0.5 complies with lib. leachability class 3 <0.5 complies with lib. leachability class 4 <0.5 complies with lib. leachability class 5 <0.5 complies with lib. leachability class 6 <0.5 complies with lib. leachability class 7 <0.5 complies with lib. leachability class 8 <0.5 complies with lib. leachability class

-8EN 303353 B6

Firing to 1000 ° C

Extract No As (mg / l) Evaluation 1 <0.3 complies with lib. leachability class 2 <0.3 complies with lib. leachability class 3 <0.3 complies with lib. leachability class 4 <0.3 complies with lib. leachability class 5 <0.3 complies with lib. leachability class 6 <0.3 complies with lib. leachability class 7 <0.3 complies with lib. leachability class 8 <0.3 complies with lib. leachability class

Example 7.

The mortar was prepared according to Example 1. The mortar contained 0.1 wt. AS2O3 · CaCO ₃ has been added to the mortar. In the extract, the content of As AA was determined by spectrometry.

Firing temperature ° C As (mg / l) Hodnocení 800 0,044 complies with lib. leachability class 1000 0.01 complies with Class I leachability

Leachability classes according to ME Decree No. 294/2005 Coll

I Ila ΐ lib ΠΪ

Material can be stored; Material can be stored Material can be stored on Material can be stored on

landfill “inert ^! landfill “others! waste landfill "other landfill" unsafe waste 'subclass: waste' mg / l 1 mg / l mg / 1 mg / l As not more than 0,05 'not more than 2,5 not more than 0,2 not more than 2,5

Industrial applicability

The invention is useful in the disposal of toxic substances containing toxic elements, in particular from the group of Be, Bi, Cd, Co, Cr, Cu, Nb, Pb, Sn, Th, U, Y, Zr.

Claims (5)

1. A method of fixing toxic substances in an alumosilicate polymer matrix prepared by mixing: an alumosilicate substance selected from the group consisting of waste electric fly ash or thermally activated clay substances; an alkaline activator at a concentration of 5 to 12 wt. Me ₂ O, based on the weight of the alumio silicate substance, where Me is Na and / or K, and • mixing water in a water / alumosilicate ratio = 0.1 to 0.6, with a toxic material containing cations and anions, in particular oxygen anions toxic elements, especially from the group of Be, Bi, Cd, Co, Cr, Cu, Nb, Ni, Pb, Sn, Th, U, Y, Zr, after mixing the mixture is compacted by vibration or pressing and then left in a temperature environment 20 to 95 ° C until hardening, characterized in that after the hardening process the mass is fired to a temperature of 600 to 1100 ° C. The method according to claim 1, characterized in that the alkaline activator is in the form of 20 alkali hydroxide and / or in the form of water glass with a module Ms of 0.7 to 3. The method of claims 1 and 2, wherein the mixture of the alumosilicate polymer with the toxic material further comprises a Ca-containing substance. 25 The method of claims 1 to 3, wherein the mixture of the alumosilicate polymer with the toxic material further comprises a filler for the production of mortars and concretes. Method according to claims 1 to 4, characterized in that the toxic material is toxic soil or toxic residues from mining operations.