ECO-EFFICIENT METHOD FOR MANUFACTURING CONCRETE

Abstract

The present invention describes a method for manufacturing of a composite fixated material comprising the steps of: (a) providing bottom oil shale ash obtained after burning oil shale, said bottom oil shale (BOSA) comprises pozzolanic particles having size of about 10 to 4000 μm and being capable of adsorbing trace elements at their surface; (b) providing acidic waste comprising said trace elements; and (c) adding the BOSA provided in step (a) to the acidic waste provided in step (b) in amount of about 0.1-0.4 weight parts of said BOSA per one weight part of said waste, and mixing said waste with said BOSA, thereby obtaining a neutralised (scrubbed) precipitate with the fixated trace elements, wherein said neutralised (scrubbed) precipitate with the fixated trace elements constitutes said composite fixated material.

Claims

1. A method for manufacturing a composite fixated material comprising: (a) Providing bottom oil shale ash (BOSA), which is obtained after burning oil shale, wherein said BOSA comprises pozzolanic particles having size of about 10 to 4000 μm and being capable of adsorbing trace elements at their surface; (b) Providing acidic waste comprising said trace elements; and (c) Adding the BOSA provided in Step (a) to the acidic waste provided in Step (b) in amount of about 0.1-0.4 weight parts of said BOSA per one weight part of said waste, and mixing said waste with said BOSA, thereby obtaining a neutralised (scrubbed) precipitate with the fixated trace elements, wherein said neutralised (scrubbed) precipitate with the fixated trace elements constitutes said composite fixated material.

2. The method of claim 1, wherein said obtained composite fixated material is a cement-like powder.

3. The method of claim 1, wherein said obtained composite fixated material is a cement-like blendable paste.

4. The method of any one of claims 1 to 3, further comprising the step of transferring said obtained composite fixated material to a site of landfill and allowing it to harden, thereby obtaining a hardened concrete composition comprising the stabilised acidic waste fixated on the BOSA particles.

5. The method of any one of claims 1 to 3, further comprising the step of hardening said concrete composition.

6. The method of claim 4 or claim 5, wherein said hardened concrete composition contains about 50-500 kg of the BOSA particles per one cubic meter of the composition and exhibits after 24 hours an increase in a compression strength of about 100-120%, and after 28 days—an increase in a compression strength of about 70-90%.

7. The method of claim 1, wherein said acidic waste is in a form of sludge or filtration cake.

8. The method of claim 1, wherein said acidic waste is received from sewage sludge, sludge from municipal sanitary wastewater treatment centres, waste and wastewater treatment plants, sludge of lake or river sediments, petroleum refinery sludge, effluent sludge from pharmaceutical production, pulp and paper industry wastes, printing wastes, acrylic latex wastes, sludge from metal surface processing, leather industry wastes, and chemical industry wastes.

9. The method of claim 1, wherein said acidic waste further comprises inorganic or organic compounds.

10. The method of claim 9, wherein said inorganic or organic compounds are organophosphates, halogenated organic compounds, organometallic compounds, herbicides and pesticides.

11. The method of claim 1, wherein said trace elements are radioactive or hazardous metals.

12. The method of claim 11, wherein said radioactive or hazardous metals are U, Pb, Nb, Sr, Th, Cs, Ce, As, Cd, Hg, Cr or Ga.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] Disclosed embodiments will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended figures. The drawings included and described herein are schematic and are not limiting the scope of the disclosure. It is also noted that in the drawings, the size of some elements may be exaggerated and, therefore, not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the disclosure.

[0025] FIG. 1 illustrates the electrostatic interactions of the trace metal cations in the solution with the aluminate and silicate anionic groups at the surface of the BOSA particles.

[0026] FIG. 2 illustrates chemical bonding between the BOSA particles, as a Lewis base, and trace metal cations, as a Lewis acid.

[0027] FIG. 3 illustrates electrostatic interactions of fine precipitates of insoluble metal salts, such as e.g. strontium carbonate (SrCO.sub.3), via the BOSA particles at pH higher than 10.5 (usually, in an alkaline solution, the metal cations are precipitating in a form of compounds of metal oxides or hydroxides).

DETAILED DESCRIPTION

[0028] In the following description, various aspects of the present application will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present application. However, it will also be apparent to one skilled in the art that the present application may be practiced without the specific details presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the present application.

[0029] The term “comprising”, used in the claims, is “open ended” and means the elements recited, or their equivalent in structure or function, plus any other element or elements which are not recited. It should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a material comprising x and z” should not be limited to materials consisting only of elements x and z. Also, the scope of the expression “a method comprising the steps x and z” should not be limited to methods consisting only of these steps.

[0030] Unless specifically stated, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within two standard deviations of the mean. In one embodiment, the term “about” means within 10% of the reported numerical value of the number with which it is being used, preferably within 5% of the reported numerical value. For example, the term “about” can be immediately understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. In other embodiments, the term “about” can mean a higher tolerance of variation depending on for instance the experimental technique used. Said variations of a specified value are understood by the skilled person and are within the context of the present invention. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4 and sub-ranges, for example from 1-3, from 2-4, and from 3-5, as well as 1, 2, 3, 4, 5, or 6, individually. This same principle applies to ranges reciting only one numerical value as a minimum or a maximum. Unless otherwise clear from context, all numerical values provided herein are modified by the term “about”. Other similar terms, such as “substantially”, “generally”, “up to” and the like are to be construed as modifying a term or value such that it is not an absolute. Such terms will be defined by the circumstances and the terms that they modify as those terms are understood by those of skilled in the art. This includes, at very least, the degree of expected experimental error, technical error and instrumental error for a given experiment, technique or an instrument used to measure a value.

[0031] As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity.

[0032] In one aspect of the present invention, there is a method for manufacturing of a composite fixated material comprising the steps of: [0033] (a) Providing bottom oil shale ash obtained after burning oil shale, said bottom oil shale (BOSA) comprises pozzolanic particles having size of about 10 to 4000 μm and capable of adsorbing trace elements at their surface; [0034] (b) Providing acidic waste comprising the trace elements; and [0035] (c) Adding the BOSA of Step (a) to the acidic waste of Step (b) in amount of about 0.1-0.4 weight parts of the BOSA per one weight part of the waste, and mixing said waste with said BOSA, thereby obtaining a neutralised (scrubbed) precipitate with the fixated trace elements.

[0036] The acidic wastes comprising the trace elements can be any acidic toxic chemical industrial wastes, for instance, the wastes of the phosphate industry containing, for example, a mixture of sulfuric and phosphoric acid or a mixture of hydrochloric and phosphoric acid. Both of them contain a lot of trace elements, such as iron, vanadium, uranium, cadmium, lead, niobium, strontium, thorium, arsenic and gallium. Most heavy metals have negative ecological impact due to their toxic, carcinogenic, and accumulative behaviour in animals and human beings. Upon mixing with the BOSA, these toxic metals, or more precisely their ions, are capable of being adsorbed and fixated at the surface of the BOSA particles. These particles comprise a large amount of burnt lime, which is calcium oxide, and even more calcite, which is calcium carbonate, therefore, they are capable of neutralising acids via the following chemical reaction:

CaO+2H.sup.+.fwdarw.Ca.sup.2++H.sub.2O

CaCO.sub.3+2H.sup.+.fwdarw.Ca.sup.2++CO.sub.2+H.sub.2O

[0037] As a result of the above reactions, the neutralised calcium precipitate, which is a scrubbed product, is obtained. The solid particles of the obtained calcium precipitate incorporate the trace elements fixated on their surface. The fixation process itself actually involves aluminates —O—Al—O.sup.− and silicates —O—SiO.sub.2.sup.− anionic groups occurring at the surface of the oil shale ash particles and interacting strongly with the trace elements via electrostatic and chemical interactions. Since the surface of the obtained particles is large, their fixating capacity is also large.

[0038] The BOSA particles can fixate the trace elements in three types of interaction as shown in FIGS. 1-3 below: [0039] 1) Reference is made to FIG. 1 showing electrostatic interactions of the trace metal cations in the solution with the aluminate and silicate anionic groups at the surface of the BOSA particles. This fixation mechanism is similar to a cation exchange reaction, and it takes place for example, with Cs.sup.+ ions. [0040] 2) Reference is now made to FIG. 2 showing chemical bonding between the BOSA particles, as a Lewis base, and trace metal cations, as a Lewis acid. This is a coordinative bonding of the non-bonding electrons of the oxygen atoms of aluminates and silicates, to the trace metal cations in the solution, yielding coordination complexes, which are attached to the BOSA particles surface. This is the mechanism by which, for example, Ce.sup.3+, Ce.sup.4+ ions, are fixated on the surface of the BOSA particles. [0041] 3) Reference is now made to FIG. 3 showing electrostatic interactions of fine precipitates of insoluble metal salts, such as SrCO.sub.3, via the BOSA particles at pH higher than 10.5 (usually, in an alkaline solution, the metal cations are precipitating in a form of compounds of metal oxides or hydroxides). In this case, the BOSA particles very effectively fixate the insoluble metal salt. The zeta potential of the BOSA particles at basic pH values is negative and that of the precipitate is positive which leads to a strong electrostatic interaction. As a result, the fine solid small particles can adsorb to the negative surface of the BOSA particles.

[0042] All three fixation mechanisms presented above are the result of the interaction of the fixated species with aluminate and silicate groups present at the BOSA particles surface.

[0043] The obtained wet scrubbed calcium precipitate is added to concrete mixes as a partial substitute to natural sand, aggregates and cement, for production of industrial concrete for civil engineering projects. It contains almost no calcium oxide which can be damaging to concrete. The inventors unexpectedly found that the concrete obtained in the process of the embodiment, has improved mechanical properties compared to the regular concrete used in industrial applications. Moreover, no leaching of pollutants, such as the trace elements, from the concrete was observed. This can be explained by large fixating capacity of the BOSA particles as mentioned above. As a result of the process of the present invention, scrubbing the acidic waste and storing it in large ponds become redundant.

[0044] The final scrubbed composite fixated material is in a form of large aggregates having the size of about 10 to 4000 μm. It passes all the leaching tests used in the environmental regulations and leaves no toxic hazardous residue, making it environmentally safe. Therefore, as noted above, the obtained scrubbed composite fixated material can be utilised as a partial substitute to cement, aggregates and natural sand for concrete mixture production, having improved technical properties with reduced cost, compared to a regular concrete.

[0045] Leaching tests of the resulted concrete produced from the composite fixated material of the present invention have also clearly shown that this concrete can be defined as a non-hazardous material, which means that it can be used for infrastructure purposes. Thus, the method of the present invention introduces a much more efficient, faster and cheaper way to treat the acidic wastes and produce a ‘green’ (non-polluting) composite fixated material that can be used for civil engineering projects with no need to store the treated hazardous wastes. Moreover, it has been surprisingly found that the utilisation of the composite fixated material of the present invention as a partial substitute to cement in concrete reduces the leaching of the hazardous compounds one order of magnitude compared to the neutralised product, whereas the mechanical strength of the concrete becomes significantly improved.

[0046] Experiments with the FOSA and BOSA were performed with the acidic waste collected at Rotem Amfert (Israel). The experiments testing the ability of the BOSA and FOSA to neutralise the acid waste and fixate the trace elements contained inside these wastes have shown that both FOSA and BOSA are excellent neutralisation reagents (scrubbers) and at the same time also efficient absorbers to the trace elements from the waste. Also, the scrubbed product was found to be an excellent partial substitute to sand and cement in concrete and concrete products for industrial applications. It has excellent mechanical properties and stands in all leaching tests (according to the European directive 14257-2 and the American improved leaching test 1311). The concrete based on the composite fixated material of the present invention can be successfully used in various infrastructure construction projects.

[0047] It has been surprisingly found that the concrete based on the composite fixated material of the present invention possesses enhanced properties compared to the regular concrete or concrete based on the BOSA prior to its treatment with acidic waste. Moreover, the concrete prepared from the pre-treated BOSA is unexpectedly found to be superior over the concrete prepared from the FOSA or coal fly ash. For example, the prepared hardened concrete composition of the invention containing about 50-500 kg of the BOSA particles per 1 m.sup.3 of the composition exhibits after 24 hours an increase in a compression strength of about 100-120%, while after 28 days the compression strength increases for about 70-90%. This is because the BOSA particles forming aggregates of the composite fixated material is significantly larger (about 10-4000 μm) and thus having a significantly smaller surface area compared to the FOSA particles or particles of the coal fly ash (the flying ash particles have the size less than 10 μm). In addition, there is no need to dry the obtained BOSA-based composite fixated material, whereas the similar material based on the FOSA always requires drying prior to its use in concrete mixes.

[0048] Moreover, the fact that the BOSA after its treatment with acidic waste creates a new composite fixated material demonstrating unusual and enhanced physical properties in the cement compositions is totally unpredictable and surprising. Yet further, since the step of treating the BOSA with acidic waste in the method of the present invention is actually the step when the BOSA is neutralising the acidic wastes, this may be considered a simple and ecologic solution to the problems of removal acidic wastes from the surroundings. It should be noted that while the FOSA is used in similar applications, the BOSA has never had such uses. It has always been buried in soil surrounding chemical plants. Therefore, the method of the present invention utilising the aggregates of BOSA with the neutralised waste in manufacturing the ‘green’ composite fixated material solves serious environmental problems.

[0049] To sum up, the present inventors have unexpectedly discovered a number of significant differences indicating the advantageous use of the BOSA over the FOSA in neutralising acidic waste comprising trace elements and further preparing the concrete compositions based on this obtained fixated material. These advantages are: [0050] 1) The amount of FOSA used for the preparation of concrete mixes is less than 50 kg per one cubic meter, while the composite fixated material based on BOSA can be successfully used in concrete in much larger amount, i.e. about 50-500 kg per one cubic meter. [0051] 2) After neutralising acidic waste with BOSA, the obtained BOSA aggregates can be easily used in concrete compositions as a cement substituent, whereas from the industrial point of view, FOSA cannot be used at all in the method of the present invention. This is simply because in case of using FOSA in the method of the present invention, very solid aggregates are obtained that prevent accurate weighing of the material and its application in a concrete factory. [0052] 3) The BOSA-based composite fixated material of the present invention can replace all concrete components: cement, natural sand, coarse aggregates and fine aggregates. FOSA can replace only the fractions in concrete mixtures. [0053] 4) There is no need to dry the obtained BOSA-based composite fixated material, whereas the similar material based on the FOSA always requires drying prior to its use in concrete mixes. This leads to saving huge amounts of water required to prepare the cement mixes, when using the instant BOSA-based composite fixated material containing significant amounts of water.

[0054] While certain features of the present application have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will be apparent to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present application.