GB2217314A

GB2217314A - Embedment of dangerous wastes containing heavy metals

Info

Publication number: GB2217314A
Application number: GB8908937A
Authority: GB
Inventors: Laszlo Barta; Zoltan Bonnyai; Mihaly Prisch; Eva Miltenyi Szerencses; Gyorgy Vamos; Laszlo Varga
Original assignee: Energiagazdalkodasi Intezet
Current assignee: Energiagazdalkodasi Intezet
Priority date: 1988-04-20
Filing date: 1989-04-20
Publication date: 1989-10-25
Also published as: DE3911440A1; HU207191B; GB8908937D0

Description

2217314 P':'SS FOR THE EMBEDMENT OF DANGEROUS WASTE MATERIALS R OC E OF

HIGH HEAVY METAL CONTENT AND CONTAINING AS ATTENDANT ELEMENT WATER SOLUBLE ALKALI IONS OF GREAT MOBILITY 1 The invention relates to the embedment of dangerous waste materials of high heavy metal content and containing water soluble alkali ions of high mobility as attendant element.

According to a significant disarming process of various types of dangerous waste materials, the number of which is more and more increasing, they are embedded into a water insoluble medium to avoid the dissolution of toxic ingredients and to prevent them from getting into the environment.

The best known among the different methods for achieving the above aim are the processes using inorganic binding materials as solicifying agents (cement, calc, flue-ash of power station, gypsum).

US-PS 3,976,537 describes a process for the embedment of liquid substances of liquid phase, wherein the liquid dange- rous waste material is embedded and solidified by using Portland cement.

According to an other process described in US-PS 4,226,631 cement is-used as embedding and solidifying agent of dangerous materials and for decreasing dissolution, lipid is added in different ratios.

HU-PS 178,097 suggests the use of an embedding mixture containing Portland cement, aluminium silicate and active carbon for the embedment dangerous waste materials, wherein active carbon is added in order to achieve the physical bind- ing of the ingredients (e.g. organic substances) disturbing the cementation processes.

Disadvantage of the above-mentioned three processes is that the embedding components (e.g. Portland cement, active carbon, lipids) are very expensive, furthermore the additional ingredients arising occasionally in addition to the toxic heavy metal ingredients of the dangerous waste materials to be embedded and delaying or inhibiting the cementation processes can be only partly bound (physically) by these processes.

In other patent specifications the use of much cheaper flue-ash, calc or flue-ash-calc binding materials are suggest-ed to use for the embedment of different dangerous waste materials. For example in US-PS 4,028,130 flue-ash-calc binding material and occasionally alkali earth metal sulphate are suggested for use as additive for embedding sewage-sludges. The sewage-sludge embedded by using the above process can be placed anywhere and can be used as basic material when building roads.

According to US-PS 4,226,630 flying flue-ash is used for disarming dangerous sludge waste materials of high heavy me- tal content. When adding the flying flue-ash in 20-70 mass% calculated for the mass of the waste material the 7-day comp ression strength of the embedded dangerous waste material is 1.75 MPa.

Disadvantage of the latter two processes is that they are suitable only for the embedment of certain types of dange rous waste materials, which do not contain ions disturbing the formation and stabilization of puzzolane bonds. Further disadvantage is that the solidifying process of the embedded waste materials is slow, its starting solidity is low.

Summerising, the embedment technologies containing inorganic components (cement, calc, flue-ash, etc.) as binding material and as additive a component or components suitable for physipal binding can only be used, if the dangerous waste material in addition to its toxic heavy metal content does not contain as additive physically unboundable, water soluble elements of great mobility.

These ingredients of great mobility - mainly alkali ions - infiltrate into the hydrocrystals during the cemen- tation and puzzolane reactions and by this inhibit the forma- Y -14 3 - 0 j tion of hydrocrystals containing C21ciumhydrosilicates (4C20.5SiO 2 5H 2 0) triC21cium-hydrO2lumin2te (3C20.Al 2 0 3 6H 2 0) C21Ciumferrithydrate MaO.Fe 2 0 3' 6H 2 0) and ettringite MaO.Al 2 0 3' 3CaSO 4' 3H 2 0) assuring the chemical stability, and the formation of crystal complexes formed by chemical and physical bond between the above crystals and the heavy metal components of the dangerous waste materials, as well as the formation of heterogenous crystal mixtures.

I Taking into consideration that the amount of the unburnable dangerous waste materials to be deposited or disarmed is 700,000 t./year only in Hungary and a significant part thereof should be considered as dangerous waste material owing to its high metal content, furthermore during their formation in the industry the half of these waste materials with heavy metal content contains more or less amount of water soluble alkali ions of great mobility (e.g. metallurgical slag, lead salt waste, barium salt slag, salt slag of magnesium content) a process which makes possible the secure and economical embedment of these waste materials is of significant importance.

Aim of the invention is to achieve a process suitable for the embedment of waste materials containing as attendant element water soluble alkali ions of great mobility in addition to the high amount of toxic heavy metal content; according to this process cheap binding agents and additives consisting of mainly industrial waste materials are utilized as embedding components.

Novelty of the process according to the invention is based on the recognition that if dangerous waste material of high heavy metal content containing water soluble alkali ions of great mobility as attendant element are ground together with a diC2lCiUM silicate containing component of alkaline exCit2tion, the latter sets into chemical reaction with the water soluble alkali ions of the dangerous waste material in the presence of water as a consequence of the mechanical exploitation and activation which can be achieved by grinding, i.e. it binds them. After mixing the active CaO ar- active S'02 +Fe 2 0 3 + +A1 2 0 3 components necessary for the physical chemical binding of heavy metals in an appropriate ratio, the dangerous waste material can securely be embedded.

As an advantage of the process it can be mentioned, that when chemically reacting the dicalcium silicate containing component of alkaline excitation with alkali ions, not only the cementation and/or puzzolane reactions being necessary for binding the heavy metals, can be carried out i.e. the formation of stabile crystal mixtures, crystal complexes is possible, but the reaction assures a more rapid solidifying and a greater starting solidity of the embedded waste material.

A further advantage of the process is that as active CaO, SiO, Al 2 0 3 and Fe 2 0 3 containing component mainly waste materials of the industry first of all different types of flue-ash fractions - are used, as well as that the dicalcium silicate containing component of alkaline excitation is also a waste material, preferably the slag of blast-furnaces.

Subject of the invention is a process for the embedment of dangerous waste materials of high heavy metal content and containing as attendant element water soluble alkali ions of great mobility. According to the process the dangerous waste material is ground then 1-45 weight% of binding agent component containing at least 20 weight% of active CaO and 5-70 weight% of binding agent component containing at least 20 weight% of active SiO 2 +Fe 2 0 3 + A1 2 0 3 are given to the grist for the physical-chemical binding of the toxic heavy metal content of the dangerous waste materials.

Novelty of the invention is that the mechanical exploitation and activating of the dangerous waste material is carried out by the simultaneous grinding of the dangerous waste material and of the 1-30 weight%, at least 20 weight% of dicalcium silicate containing, alkaline excitation component related to the weight of the dangerous waste material, whereas the the dicalcium silicate containing component is set into chemical react-ion with the alkali ions of the dangerous waste materials in the presence of water. The Blain specific surface of the mixture obtained by the simultaneous grinding of the dangerous waste material and the dicalcium silicate containing, alkaline excitation component is min. 1800 cm 2 /g. The alkaline excitation dicalcium silicate containing component used as additive is a waste material of the industry, preferably an active granulate slag of blast furnaces. By the chemical reac- tion of alkaline excitation dicalcium silicate containing additive with the water soluble alkali ions of the dangerous waste material, the complete cementation and/or puzzolane reac tionS and the stability of the crystalline end products can be assured. Owing to the own hydrating and solidifying methods by the above chemical reaction rapid solidifying and great starting solidity are assured to the dangerous waste material, whereas the starting pressure solidity of the embedded dangerous waste material is adjusted to the following value:

in the age of 3 days: 2.3 MPa in the age of 7 days: 3.5 MPa.

The process according to the invention is described in following non-limiting examples.

detail in the Example 1 25 The embedment of slag of powder metallurgy with toxic heavy metal content and containing as attendant element 6 mass% of water soluble sodium -related to the mass of the waste material is started with the simultaneous grinding of powder metallurgical slag and 5 mass% granuled slag of bast-furnace related to the mass of the powder metallurgical slag. The two-component mixture has a Blaine specific surface of 1800 cm 2 /g.

To the two-component mixture 15 mass% of stirring water related to the mass of dangerous material, non-hydraulic flue-ash, and 1 mass% of calcium hydrate containing waste powder, 6 then further 8 mass% of stirring water are added, which is necessary to achieve the spoil-wet consistence. After concentrating the spoil-wet, concrete-like mixture 3.5 MPa was measured as the 7-day compression strength of the embedded waste material.

Main characteristics of the powder metallurgical slag (dangerous waste material):

humidity content: 1.6 mass% heating loss (at 600 0 C): 4.1 mass% Na-content: 17-20 %, 5-6 mass% thereof is water soluble 0.4 % 5-6% 8-10 %, a little part is water soluble 3-4 % completely water soluble 1020 mg./kg.

3055 mg./kg.

10-90 mg./kg.

mg./kg.

2050 mg./kg.

K-content: CaO-content: so 4_ content:

Cl-content:

Pb-content:

Cu-content:

Zn-content:

Sn-content:

so 4 2-_ content:

Main features of the embedding components:

a) granuled slag of blast-furnaces:

dicalcium silicate content b) not hydraulic flue-ash active SiO 2 +Fe 2 0 3 +Al 2 0 3 content calcium hydrate waste powder active CaO content 60.mass% The dissolution values of the embedded powder metallurgi cal waste material measured at its age of 28 days are much lower than the permissible values (see Table I).

c) mass% mass% 7 - Table I

Dissolution values of the embedded waste material with distilled water Pb Cu Zn 10 Sn SO 2 Example 2

Dissolution with distilled water mg./dm 3.

0.1 0.04 C 0.02 C 5 35.

The embedment of dangerous waste material of high Zinc and copper content, containing little amount of water soluble sodium and kalium ions, is carried out according to example 1 having the following composition:

part by weight of dangerous waste material part by weight of slag of blast-furnaces 70 part by weight of hydraulic flue-ash part by weight of carbide calc waste material part by weight of stirring water (added in to parts as written in example 1).

The dangerous waste material -slag of blast furnace- ob tained by grinding has a Blaine specific surface: 2800 cm 2 /g.

The compression strength of the embedded waste material concentrated in spoil-wet condition in 4.8 MPa. Main characte ristics of the dangerous waste material:

humidity content: 8.4 mass% heating loss: 5.6 mass% Na content (water soluble):

K content (water soluble):

Pb content:

Cu content:

Cr content:

3 mass% 5 mass% 472 mg./kg. 3654 mg./kg.

82 mg./kg.

8 - P b C u Cr N i Zn C d Ba Ni content: Zn content: Cd content: Ba content: Sn content:

177 mg./kg. 17273 mg./kg.

4.0 mg./kg. 80 mg./kg. 1000 mg./kg. Main characteristics of the embedding components:

a) granuled slag of blast furnace dicalcium silicate content 20 mass% b) not hydraulic flue-ash active SiD 2 +Fe 2 0 3 +Al 2 0 3 content 20 mass% c) carbide calc waste material water content active CaO content t 9 mass% 20 mass% Table II

Dissolution with distilled water mg./dm 3 0.02 0.22 < 0.04 < 0.1 < 0.02 e, 0.02 < 2.

9 M&C FOLIO: 230P58542

Claims

WANGDOC: 0153D 1. A process for the entrapment of waste containing heavy metals and highly mobile alkali ions in a solid product. characterised in that the waste is mixed with a sufficient quantity of dicalcium silicate to substantially immobilise the alkali ions in the presence of water.

2. A process according to claim 1 wherein the waste is mixed with about 0. 2-30 wt% dicalcium silicate.

3. A process according to claim 1 or 2 wherein the mixing is achieved by grinding.

4. A process according to any preceding dlaim wherein the waste material is formed into the solid product by the incorporation of 0.2-45 wt% CaO and 1-70 wt% Sio 2 /Fe 2 0 3 /Al 2 0 3 A process according to any preceding claim wherein the blend of waste and dicalcium silicate has a Blaine specific surface of at least about 1800cm 2 /g.

6. A process according to any preceding claim wherein the dicalcium silicate is provided by an alkaline excitation component.

7. A process according to any preceding claim wherein granulated blast furnace slag is used for the dicalcium silicate component.

8. A process according to any preceding claim wherein the alkali ions are sufficiently immobilised to enable substantial completion of the cementation andlor puzzolane reactions to stabilise the product.

9. A process according to any preceding claim wherein the compression strength of the product is at least 2.3 MPa after 3 days.

10. A process according to any preceding claim wherein the product has a compression strength of at least 3.5 MPa after 7 days.

11. A process for the embedment of dangerous waste materials of high heavy metal content and containing water soluble alkali ions of great mobility, comprising grinding the waste material and giving 1 to 45wt% of binding component. min. 20wt% active CaO and 5 to 70wt% of binding material component containing min. 20wt% active Sio 2 +Fe 2 0 3 +Al 2 0 3 to the grist, characterised in that the mechanical exploitation and activation of the waste material is carried out by simultaneous grinding of the waste with 1-30wt% alkaline excitation component relative to the waste and containing at least 20wt% dicalcium silicate, setting the dicalcium silicate-containing component into reaction with the alkali ions in the presence of water.

12. A process according to claim 11 with parameters as defined in any of claims 1 to 10.

13. A process according to any of claims 1 to 10 having any of the parameters as defined in claim 11.

14. A product produced in accordance with the process of any preceding claim.

!Z il 15. The use of the product of claim 14 as a foundation material.

16. A process for the disposal and/or entrapment of waste materials containing heavy metals and mobile alkali ions involving the use of dicalcium silicate substantially as described hereinbefore.

PubiWied 1989 &tThe Patent=oe. State House,6&71 Elio HolboraLondonWIR 4TP. purther ooples M&yb,, ObW,,dftm Thepatmtoaloe. Was Bmuch, St MLry Cray, Orplr4wn, Kew MW 3RD. Printed by lEumplex tewmlques Itd, Bt MW7 CTAY, Kent, COn. 1/87