Method for binding sulfates in body of water, product prepared by said method, calcined mixture for said method and use of said mixture

Abstract

The invention relates to a method for binding sulfates in a body of water comprising sulfates, a calcined mixture prepared by calcining a mixture comprising calcium oxide and calcium alumina and / or calcium aluminate and cooling it to bind sulfates in a body of water, and the use of at least one element comprising CaO and mayenite supergroup and / or of a powder mixture and / or calcined mixture comprising at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or calcium silicate for binding sulfates in a body of water.

Description

Technical Field

[0001] This invention relates to a method for binding sulfates in water containing sulfates, products prepared by said method, calcined mixtures for binding sulfates in water prepared by calcining and cooling a mixture containing calcium oxide and calcium aluminate and / or calcium aluminate, and the use of powder mixtures and / or calcined mixtures containing CaO and at least one calcium aluminate supergroup mineral and / or containing at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or calcium silicate for binding sulfates in water. Background Technology

[0002] Sulfate ions are generated in many processes involving sulfuric acid and in the production of sulfuric acid. In addition, sulfate ions can also enter the environment in other ways, such as through further reactions of sulfur oxides, which can be generated during the combustion of fossil fuels, or through fertilization.

[0003] However, in many water bodies, sulfate ions are problematic and harmful to the environment, disrupting the ecological balance. Furthermore, sulfate ions can also damage buildings and structures. Therefore, it is necessary to reduce excessive sulfate levels.

[0004] The article "Calcium aluminate precipitation of sulfate and calcium sulfate" published on October 10, 1992, in Wasser, Luft und Boden, Zeitschrift für Umwelttechnik, discloses the precipitation of sulfate in industrial wastewater using specially formulated calcium aluminate. The removal of sulfate and calcium from wastewater streams in the case of ettringite formation can also be found in WO 98 / 55405 A1.

[0005] However, current methods for sulfate binding or removal still leave a significant amount of sulfate ions in the water. Therefore, there is a need for methods that can effectively bind sulfate ions in water. Summary of the Invention

[0006] According to the present invention, it has been found that sulfates can be further bound by adding a calcined mixture containing CaO in addition to calcium aluminate and / or calcium alumina.

[0007] A first aspect of the present invention relates to a method for combining sulfates in a body of water containing sulfates, the method comprising: A mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate is provided; Calcination of a mixture comprising calcium oxide and calcium alumina and / or calcium aluminate, followed by cooling of the mixture, to produce a calcined mixture; and The calcined mixture is added to the water containing sulfate, thereby binding the sulfate.

[0008] Furthermore, a second aspect discloses a method for binding sulfates in a body of water containing sulfates, the method comprising: Provide mixtures, particularly powder mixtures, comprising CaO and at least one mineral of the calcium aluminum group, preferably comprising the molecular formula Ca6Al7O 16.5 (or Ca) 12 Al 14 O 33 ) calcium aluminum stone, and / or at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or at least one calcium silicate, Wherein, based on the mixture, particularly the powder mixture, the mixture, particularly the powder mixture, contains at least 27.0 to 45.0 wt.%, preferably 30.0 to 40.0 wt.%, more preferably 32.0 to 37.0 wt.% by mass of calcium, and contains 20.0 to 28.0 wt.%, preferably 21.0 to 27.5 wt.%, more preferably 21.5 to 25.5 wt.% by mass of aluminum (including the respective endpoint values); and The minerals containing CaO and at least one calcium aluminum group and / or a mixture containing at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or calcium silicate are added to a body of water containing sulfate, thereby binding the sulfate.

[0009] A third aspect of the invention relates to a calcined mixture for binding sulfates in water, prepared by: providing a mixture comprising calcium oxide and calcium alumina and / or calcium aluminate; and The mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate is calcined and the mixture is cooled to prepare a calcined mixture for binding sulfates in water.

[0010] The fourth aspect relates to a product comprising bound sulfate prepared by the method of the present invention.

[0011] The present invention also discloses the use of a mineral comprising CaO and at least one calcium aluminum silicate supergroup and / or a powder mixture comprising at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or calcium silicate and / or the calcined mixture of the present invention for binding sulfates in water.

[0012] Other aspects of the invention can be found in the dependent claims and detailed descriptions. Attached Figure Description

[0013] The accompanying drawings are intended to illustrate embodiments of the invention and provide a further understanding of the invention. In conjunction with the specification, the drawings are used to explain the concepts and principles of the invention. Other embodiments and many of the advantages mentioned will be apparent from the drawings. Elements in the drawings are not necessarily shown to scale relative to each other. Unless otherwise stated, identical, functionally identical, and equivalent elements, features, and components are indicated by the same reference numerals in the drawings.

[0014] Figure 1 The method according to the first aspect of the invention is illustrated schematically.

[0015] Figure 2 The method according to the second aspect of the invention is illustrated schematically. Detailed Implementation

[0016] definition

[0017] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0018] For the purposes of this invention, "water body" or "water" is understood to mean all water or water bodies, such as ponds, lakes, rivers, reservoirs, coastal waters, fjords, brackish lakes, bays, seawater, water in breeding stations for fish and other marine animals, aquariums, water in agricultural or drinking water reservoir storage systems, and aquifers, whereby such water may also contain soil, sediments and / or sludge, as well as settled and suspended solids. For the purposes of this invention, sediments are understood to be solids found in water such as ponds, lakes, and rivers. Sludge may originate from, for example, sewage treatment plants, wastewater filters, etc., and / or be present at the bottom of the water body. Preferred water bodies are freshwater bodies (e.g., ponds, lakes, etc.) with sediments and / or silt deposits, which have sub-oxygen and / or anoxic zones and may rapidly become unstable, but can be effectively treated by this method. This method is particularly suitable for water bodies with low sulfate concentrations (e.g., up to 2.5 g / L). In addition, sulfate removal is also advantageous in seawater desalination, as it can prevent gypsum formation and thus save energy during desalination by reducing the load on the membrane.

[0019] When identifying and naming calcium alumina and / or calcium aluminate, overlap may also exist in the definitions within the scope of this invention. Scientifically, the terms calcium alumina and calcium aluminate are not clearly distinguished from each other, and therefore there is practical overlap between them (see, for example, A. Intiso et al., "The fascinating world of mayenite (Ca...)"). 12 Al 14 O 33(and its derivatives), Rendiconti Lincei. Scienze Fisiche e Naturali, 2021, 32, 699, 708, where calcium aluminate is referred to as mesoporous calcium aluminate in the abstract and as mesoporous calcium aluminate in Part 1. For example, the mineral Krotit is also called calcium aluminate with the chemical formula CaAl2O4 or calcium aluminate with the chemical formula CaO·Al2O3. Because it is difficult to make a clear distinction in science, the two terms are used interchangeably and synonymously here.

[0020] Besides monocalcium aluminate found in the mineral forms of Crostone and dmitryivanovit (CaO·Al2O3(CA)), other calcium aluminates include tricalcium aluminate (3CaO·Al2O3(C3A)) and dodecacalcium heptaaluminate, also known as the mineral calcium aluminum oxide (12CaO·7Al2O3(C3A)). 12 A7), calcium aluminate (CaO·2Al2O3(CA2)) found in the form of the mineral Grossit, and calcium aluminate (CaO·6Al2O3(CA6)) found in the form of the mineral Hibonit. In addition, synthetic or foreign calcium aluminates, such as brownmillerit, should also be mentioned.

[0021] Unless otherwise stated or obvious from the context, the quantities specified in the context of this invention refer to wt.%.

[0022] The standard pressure is 101325 Pa = 1.01325 bar.

[0023] A first aspect of the present invention relates to a method for combining sulfates in a body of water containing sulfates, the method comprising: A mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate is provided; Calcination of a mixture comprising calcium oxide and calcium alumina and / or calcium aluminate, followed by cooling of the mixture to produce a calcined mixture; and The calcined mixture is added to the water containing sulfate, thereby binding the sulfate.

[0024] In the method, there are no particular limitations on the provision of a mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate.

[0025] According to the present invention, there are no particular limitations on the mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate, provided that it contains calcium oxide and additionally contains at least one calcium aluminate, at least one calcium aluminate, or at least one calcium aluminate and at least one calcium aluminate. Furthermore, according to some embodiments, the mixture also contains at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or at least one silicate, such as geollenite (Ca2Al((AlSi)O7)) and / or calcium olivine (Calcio-Olivin(Ca2(SiO4))).

[0026] There are no particular restrictions on the amount of calcium oxide. It can be added to the mixture in a suitable manner, for example, in the form of a technically pure or pure compound, but it can also be added to the mixture as calcined lime or quicklime.

[0027] There are no particular limitations on calcium alumina and / or calcium aluminate. The mixture may also contain more than one type of calcium alumina and / or calcium aluminate. According to some embodiments, calcium alumina and / or calcium aluminate are provided as a mineral mixture containing calcium alumina and / or calcium aluminate, for example, naturally occurring or mined, and then appropriately mixed with calcium oxide to prepare the mixture. According to some embodiments, the mineral mixture and the mixture therefore contain at least crosite and grossite, and according to some embodiments, contain calcium aluminate, wherein, based on the mineral mixture, calcium aluminate is preferably present in an amount, for example, <0 wt.% and less than 7 wt.%, preferably less than 4 wt.%, and more preferably less than 2 wt.%. According to some preferred embodiments, the mineral mixture or the mixture further contains at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or at least one calcium aluminosilicate, particularly calcium aluminate (C2AS, Ca2Al((AlSi)O7)) and / or calcium olivine (C2S, Ca2(SiO4)).

[0028] According to certain embodiments, based on a mineral mixture, the mineral mixture contains at least 20.0 to 29.0 wt.%, preferably 23.0 to 26.0 wt.%, more preferably 24.0 to 25.8 wt.% of calcium by mass, and contains 27.0 to 35.0 wt.%, preferably 27.2 to 30.5 wt.%, more preferably 27.5 to 29.5 wt.% of aluminum by mass (thereby including corresponding endpoint values). This allows for the realization of a preferred sulfate-bound phase during calcination.

[0029] According to some embodiments, the mixture contains calcium oxide and a mineral mixture comprising calcium alumina and / or calcium aluminate. According to some embodiments, the mixture comprising calcium oxide and a mineral mixture comprising calcium alumina and / or calcium aluminate contains calcium oxide in a ratio (w / w) of 5:95 to 50:50, preferably 10:90 to 30:70, with the mineral mixture comprising calcium alumina and / or calcium aluminate. This means that calcium oxide is present in the mixture in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, and in contrast, calcium alumina, calcium aluminate, or both (if both are considered to be present according to nomenclature) in an amount of 50 to 95 parts by weight, preferably 70 to 90 parts by weight. The sulfate binding can be further improved by appropriate adjustments. For example, as described above, the mineral mixture can be, for example, a natural mineral mixture mined from a mine.

[0030] According to the invention, a mixture comprising calcium oxide and calcium aluminate can be mixed and ground prior to calcination. There are no particular limitations on the mixing and grinding, and it can be carried out in a suitable manner, for example, using a suitable grinding apparatus, preferably a ball mill. Mixing and grinding can produce a powder that, when the mixture is calcined, leads to the formation of a favorable phase for the efficient binding of sulfates during the process.

[0031] According to some embodiments, the mixture is mixed and ground to a particle size >0.0 to ≤20.0 mm, preferably >0.0 to ≤10.0 mm, more preferably >0.0 to ≤5.0 mm, and even more preferably >0.0 to ≤1.0 mm, for example, >0.0 to ≤0.5 mm. According to some embodiments, the particle size is determined by sieving the mixed and ground mixture.

[0032] After preparation and any optional mixing, grinding, and, for example, sieving, the mixture may be calcined.

[0033] There are no particular limitations on the calcination of a mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate, and the cooling of said mixture to prepare a calcined mixture. This can be carried out, for example, in a suitable furnace.

[0034] According to some embodiments, calcination is carried out at a temperature of 800 to 1500°C, preferably at 900 to 1450°C, and more preferably at 950 to 1400°C. At this temperature, a favorable phase transition of the mixture is obtained, which allows for further improvement of sulfate binding in the method. The duration of calcination is not particularly limited, and it is carried out, for example, 1 to 12 hours, for example 3 to 8 hours, for example 6 hours.

[0035] Furthermore, there are no particular restrictions on cooling, which is usually carried out by, for example, natural cooling, such as in a desiccator or at room temperature to room temperature (18 to 25°C).

[0036] Furthermore, there are no particular limitations on adding the calcined mixture to a sulfate-containing water body to bind the sulfate. According to some embodiments, the addition of the calcined mixture to the sulfate-containing water body is carried out by distributing the calcined mixture into the water body, and / or by natural and / or artificially induced mixing after addition. Distribution is not particularly limited and may include, for example, dispersion. Uniform distribution is preferred here. Natural and / or artificially induced mixing can be achieved, for example, by introducing the mixture into a natural flow field and / or by generating an artificial flow field. Distribution and / or mixing allow for faster sulfate reduction in the calcined mixture and help to better avoid side reactions.

[0037] According to some embodiments, mixing is carried out for at least 30 minutes after addition, preferably at least 1 hour, and more preferably at least 2 hours. Longer mixing times can promote sulfate binding.

[0038] According to some embodiments, the addition is carried out at a temperature of 20 to 40°C, preferably 23 to 37°C, and more preferably 27 to 33°C. Therefore, for example, the introduction into natural water bodies is preferably carried out in summer.

[0039] Before adding the calcined mixture to the water body, according to certain embodiments, the water body can be brought to a suitable pH, for example, between 6.0 and 13.0, such as 7.0 to 12.5, preferably in the pH range of 10.0 to 12.0, such as about 11.0. If desired, the pH can be appropriately adjusted, for example, with CaO and / or NaOH and / or lime milk.

[0040] After the sulfate binds, the resulting product can be appropriately separated from the water body according to certain implementation schemes; that is, the product can be separated from the bound sulfate. There are no particular limitations on the separation.

[0041] exist Figure 1 The corresponding method according to the first aspect of the invention is illustrated schematically.

[0042] After providing a mixture containing calcium oxide and calcium aluminate and / or calcium aluminate in step 1, the mixture containing calcium oxide and calcium aluminate and / or calcium aluminate is calcined in step 2 and the mixture is cooled to produce a calcined mixture, and the calcined mixture is added to an aqueous body containing sulfate in step 3, thereby binding the sulfate.

[0043] Furthermore, this invention discloses a method for binding sulfates in a body of water containing sulfates, the method comprising: Provide mixtures, particularly powder mixtures, comprising CaO and at least one mineral of the calcium aluminum group, preferably comprising the molecular formula Ca6Al7O 16.5 (or Ca) 12 Al 14 O 33 The mixture comprises calcium aluminum silicate, and / or at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or at least one calcium silicate, wherein, based on the mixture, particularly the powder mixture, the mixture, particularly the powder mixture, contains at least 27.0 to 45.0 wt.%, preferably 30.0 to 40.0 wt.%, more preferably 32.0 to 37.0 wt.% by mass of calcium, and contains 20.0 to 28.0 wt.%, preferably 21.0 to 27.5 wt.%, more preferably 21.5 to 25.5 wt.% by mass of aluminum; and the mineral comprising CaO and at least one calcium aluminum silicate supergroup and / or a mixture comprising at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or calcium silicate is added to an aqueous body containing sulfate, thereby binding the sulfate.

[0044] Provide mixtures, particularly powder mixtures, comprising CaO and at least one mineral of the calcium aluminum group, preferably comprising the molecular formula Ca6Al7O 16.5 (or Ca) 12 Al 14 O 33 There are no particular limitations on calcium aluminum stone, and / or at least one calcium aluminum silicate and / or at least one calcium aluminum silicate and / or at least one calcium silicate.

[0045] The mixture, especially the powder mixture, contains at least CaO (calcium oxide) and at least one mineral from the calcium aluminum group, preferably containing the molecular formula Ca6Al7O. 16.5 (or Ca) 12 Al 14 O 33 The mixture contains at least CaO and a mineral of the calcium aluminate supergroup, preferably calcium aluminate. According to certain embodiments, the mixture, particularly the powder mixture, contains at least CaO, calcium aluminate, and calcium silicate, such as tricalcium silicate (Ca3SiO5). Preferably, calcium aluminate is the main component of the powder mixture, accounting for more than 50 wt.%, preferably more than 80 wt.%, and more preferably more than 85 wt.% based on the powder mixture (i.e., 100 wt.% powder mixture). The corresponding mixture, particularly the powder mixture, can be obtained specifically by calcination as described in the method of the first aspect.

[0046] Based on the mixture, particularly the powder mixture, containing at least 27.0 to 45.0 wt.%, preferably 30.0 to 40.0 wt.%, more preferably 32.0 to 37.0 wt.% by mass of calcium, and containing 20.0 to 28.0 wt.%, preferably 21.0 to ≤27.5 wt.%, more preferably 21.5 to 25.5 wt.% by mass of aluminum. Appropriate adjustments to the proportions make the binding of sulfates more effective.

[0047] According to some embodiments, the mixture is a powder mixture. According to some embodiments, the powder mixture comprises particles with a particle size >0.0 to ≤20.0 mm, preferably >0.0 to ≤10.0 mm, more preferably >0.0 to ≤5.0 mm, and even more preferably >0.0 to ≤1.0 mm, such as particles with a particle size >0.0 to ≤0.5 mm, or preferably composed of such particles. According to some embodiments, the particle size is determined by sieving the powder mixture.

[0048] According to certain embodiments, the addition of minerals containing CaO and at least one calcium aluminum silicate supergroup and / or mixtures containing at least one calcium aluminum silicate and / or at least one calcium aluminosilicate and / or calcium silicate, particularly powder mixtures, to an aqueous body containing sulfate is carried out by distributing the calcined mixture into the aqueous body, and / or by natural and / or artificially induced mixing after the addition, wherein the mixing after the addition preferably takes place for at least 30 minutes, preferably at least 1 hour, and preferably at least 2 hours. Distribution is not particularly limited and may include, for example, dispersion. Uniform distribution is preferred here. Natural and / or artificially induced mixing can be achieved, for example, by introducing the mixture into a natural flow field and / or by generating an artificial flow field. Distribution and / or mixing allow the calcined mixture to undergo sulfate reduction more rapidly and help avoid side reactions. Prolonged mixing promotes sulfate binding.

[0049] Before adding minerals containing CaO and at least one calcium aluminum silicate supergroup and / or mixtures containing at least one calcium aluminum silicate and / or at least one calcium aluminosilicate and / or calcium silicate, particularly powdered mixtures, to a body of water, the water may be brought to a suitable pH, for example, between 6.0 and 13.0, such as 7.0 to 12.5, preferably in a pH range of 10.0 to 12.0, such as about 11.0, according to certain embodiments. If necessary, the pH may be appropriately adjusted by, for example, CaO and / or NaOH and / or lime milk.

[0050] After the sulfate binds, the resulting product can be appropriately separated from the water body according to certain implementation schemes; that is, the product can be separated from the bound sulfate. There are no particular limitations on the separation.

[0051] Figure 2 An exemplary method of the second aspect is schematically illustrated. As in step 2a, a mineral comprising CaO and at least one grossular supergroup is provided, preferably comprising a mineral with the molecular formula Ca6Al7O. 16.5 (or Ca) 12 Al 14 O 33 A mixture of calcium aluminum silicate and / or at least one calcium aluminum silicate and / or at least one calcium aluminosilicate and / or at least one calcium silicate, wherein, based on the powder mixture, the powder mixture contains at least 27.0 to 45.0 wt.%, preferably 30.0 to 40.0 wt.%, more preferably 32.0 to 37.0 wt.%, and contains 20.0 to 28.0 wt.%, preferably 21.0 to ≤27.5 wt.%, more preferably 21.5 to 25.5 wt.%, in particular, after the powder mixture, in step 3a, a mineral containing CaO and at least one calcium aluminum silicate supergroup and / or a mixture containing at least one calcium aluminum silicate and / or at least one calcium aluminosilicate and / or calcium silicate is added to an aqueous body containing sulfate, thereby binding the sulfate.

[0052] Furthermore, this invention discloses a calcined mixture for binding sulfates in water, prepared by: providing a mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate; and calcining the mixture and cooling it to prepare the calcined mixture for binding sulfates in water. The calcined mixture is obtained particularly by the method of the first aspect and is therefore highly suitable for sulfate binding. The calcined mixture preferably contains at least calcium aluminate and calcium silicate, such as tricalcium silicate (Ca3SiO5). Calcium aluminate is preferably the major component in the powder mixture, comprising more than 50 wt.%, preferably more than 80 wt.%, and more preferably more than 85 wt.%, based on the powder mixture (i.e., 100 wt.% powder mixture).

[0053] Calcination is preferably carried out at a temperature of 800 to 1500°C, more preferably at a temperature of 900 to 1450°C, and even more preferably at a temperature of 950 to 1400°C, with no particular limitations, nor is cooling particularly limited. These can be carried out as described in the first aspect. The starting product specifically corresponds to the product described in the first aspect. Therefore, the aspects described herein can also be applied to calcined mixtures used to bind sulfates.

[0054] Furthermore, this invention discloses products comprising bound sulfates, prepared by the method described in the first or second aspect of the invention. Specifically, it comprises bound ettringite (Ca6Al2(SO4)3(OH)). 12Sulfates of (x 26 H2O) are also known as sulfates, but other sulfate-containing compounds such as Orschallit (Ca3(SO3)2(SO4)(H2O)) are also known as sulfates. 12 ) and / or other compounds such as calcite (CaCO3) and / or bayerite (Al(OH)3) may also be included in the product and are preferred to be included therein. Due to the starting compounds, the product also preferably has an excellent particle size distribution, and is therefore very suitable for further use, such as as an additive in the production of concrete and / or cement, or as an additive in the production of gypsum or mortar.

[0055] The present invention also discloses the use of minerals comprising CaO and at least one calcium aluminate supergroup and / or mixtures comprising at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or calcium silicate, particularly powder mixtures and / or calcined mixtures, for binding sulfates in water bodies. As described above, these powder mixtures and / or calcined mixtures are particularly suitable for binding sulfates in certain water bodies with low sulfate content (e.g., water bodies that are not industrial wastewater).

[0056] The above-described embodiments, designs, and further developments can be combined with each other as needed, provided that such combinations are reasonable. Other possible embodiments, further developments, and implementations of the invention include combinations of features of the invention described above or below with respect to embodiments not explicitly mentioned. In particular, those skilled in the art will also add various aspects as improvements or additions to the corresponding basic form of the invention.

[0057] The invention will now be explained in more detail with reference to various embodiments thereof. However, the invention is not limited to these embodiments.

[0058] Example

[0059] Comparative Example 1

[0060] A natural mineral mixture containing, as the main phase, calcium aluminum feldspar, kroite, grossite, calcium olivine, and calcium aluminum ore as determined by X-ray diffraction (XRD), with a Ca weight fraction of 25.5 wt.% and an Al weight fraction of 27.5 wt.%, was ground using a ball mill. The fraction with a particle size less than 0.5 mm was sieved from the ground mineral mixture and used for further experiments.

[0061] XRD measurements were performed using a PANalytical “AERIS research” diffractometer with Cu Kα radiation at 1.5418 Å, in Bragg-Brentano geometrical reflection mode, according to DIN EN 13925-1, -2:2003. -3: 2005 and DIN EN 1330-11:2007.

[0062] The ground mineral mixture obtained in this way is called the comparative mixture "V1".

[0063] A portion of the mineral mixture was mixed with CaO (calcium oxide powder; CAS 1305-78-8; >96%; product: 22645.360, VWR Chemicals) at a mass ratio of 80:20 (w / w) and calcined at 1000°C in a ceramic crucible in a muffle furnace for 6 hours. The resulting mixture was then cooled to room temperature in a desiccator. The mass loss during calcination was 4.23 wt%. The mixture obtained in this manner is referred to as Example Mixture “B1”. Calcination of Mixture B1 was also examined by XRD as described above, yielding a Ca weight fraction of 34.7 wt% and an Al weight fraction of 23.8 wt%, wherein the main phases were calcium aluminate, alkyd, portlandit, and katoit.

[0064] Furthermore, a portion of the comparative mixture V1 was calcined at 1000°C in a ceramic crucible in a muffle furnace for 6 hours according to the example mixture B1, and then the mixture prepared in this manner was cooled to room temperature in a desiccator. The loss during calcination was 0.68% by weight. The mixture obtained in this way is referred to as the comparative mixture "V2".

[0065] Examples 1 and 2 and Comparative Examples 1 to 4 Artificial sulfate-containing water is prepared by weighing sodium sulfate (Na2SO4) and adding and dissolving it in tap water to a concentration of 0.2 g / L, and adjusting the pH to 11.0 with CaO and / or NaOH and / or lime milk.

[0066] Comparative mixtures V1 and V2, along with CaO itself and example mixture B1, were added to the corresponding sample amounts of sulfate-containing tap water prepared in this manner at the temperatures specified in Table 1, to final concentrations of V1, V2, CaO, and B1 of 10 g / L, respectively. The samples thus prepared were stirred at 250 rpm for 24 hours using a magnetic stirrer. Sediments may form in some cases; in Example 1, the supernatant was filtered through a calcium acetate filter with a pore size of 0.45 μm or 0.25 μm.

[0067] Sulfate concentration was determined using Metrohm ion chromatography (IC Metrohm 881). The mobile phase consisted of 5.2995 g Na₂CO₃ and 0.168 g NaHCO₃ / 1000 ml ultrapure water. Sulfate was calibrated using a multivariate standard to obtain an r0.998 for sulfate concentrations ranging from 1 to 50 mg / L. 2The calibration curve for the values. The results of the sulfate reduction compared to the original sulfate content are given as a percentage in Table 1.

[0068] Table 1: Results of sulfate reduction

[0069] In Example 1, another sample was taken out after 3 hours and filtered accordingly. At this point, the sulfate reduction (w / w) was 96.0%, which was higher than the values ​​of Comparative Examples 2 and 3 after 24 hours of stirring.

[0070] It can be seen that longer mixing time increases the reduction of sulfate. However, temperature also has an effect on sulfate reduction, although the effect of temperature on mixture B1 is smaller than that on mixture V1. As is usually the case when CaO is used alone, mixture V1 does not achieve any sulfate reduction at low temperatures. However, even at temperatures raised to 31°C, mixture B1 of the present invention is superior to the control mixture V2 in terms of unexpected sulfate removal levels (achieving a 99.3% reduction compared to 95.2%), which is attributed to the additional CaO present during calcination. The calcined mixture V2 is only slightly superior to the uncalcined mixture V1.

Claims

1. A method for binding sulphate in a water body comprising sulphate, the method comprising: providing a mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate; calcining the mixture comprising calcium oxide and calcium aluminate and / or calcium aluminate and cooling the mixture to produce a calcined mixture; and adding the calcined mixture to the water body comprising sulphate, thereby binding the sulphate.

2. The method according to claim 1, wherein the calcining is performed at a temperature of 800 to 1500 °C, preferably at a temperature of 900 to 1450 °C, more preferably at a temperature of 950 to 1400 °C.

3. The method according to claim 1 or 2, wherein the mixture contains calcium oxide and a mineral mixture comprising calcium aluminate and / or calcium aluminate, wherein the mixture containing calcium oxide and a mineral mixture comprising calcium aluminate and / or calcium aluminate contains calcium oxide in a ratio (w / w) to the mineral mixture comprising calcium aluminate and / or calcium aluminate of 5:95 to 50:50, preferably 10:90 to 30:

70.

4. The method according to any one of the preceding claims, wherein the mixture comprising calcium oxide and calcium aluminate is mixed and ground prior to calcination, preferably using a ball mill.

5. The method according to claim 4, wherein the mixing and grinding is performed to a particle size of > 0.0 to < or equal to 20.0 mm, preferably a particle size of > 0.0 to < or equal to 10.0 mm, more preferably a particle size of > 0.0 to < or equal to 5.0 mm, even more preferably a particle size of > 0.0 to < or equal to 1.0 mm.

6. The method according to any one of the preceding claims, wherein the adding of the calcined mixture to the water body comprising sulphate is performed by dispensing the calcined mixture into the water body; and / or a natural and / or artificially induced mixing is performed after the adding.

7. The method according to claim 6, wherein the mixing after the adding is performed for at least 30 minutes, preferably at least 1 hour, preferably at least 2 hours.

8. A method for binding sulphate in a water body comprising sulphate, the method comprising: A mixture, in particular a powder mixture, comprising CaO and at least one mineral of the mayenite supergroup, preferably comprising mayenite of the formula Ca6Al7O 16.5 and / or at least one calcium aluminate and / or at least one calcium aluminosilicate and / or at least one calcium silicate is provided. wherein, based on the mixture, in particular the powder mixture, at least a mass fraction of 27.0 to 45.0 wt.%, preferably 30.0 to 40.0 wt.%, more preferably 32.0 to 37.0 wt.% of calcium and a mass fraction of 20.0 to 28.0 wt.%, preferably 21.0 to < 27.5 wt.%, more preferably 21.5 to 25.5 wt.% of aluminium is contained in the mixture, in particular the powder mixture; and adding the mixture comprising CaO and at least one mineral of the calcium aluminate supergroup and / or comprising at least one calcium aluminium aluminate and / or at least one calcium aluminium aluminate and / or calcium aluminate and / or silica calcium to the water body comprising sulphate, thereby binding the sulphate.

9. The method of claim 8, wherein, The addition of the mixture comprising CaO and at least one mineral of the gehlenite supergroup and / or comprising at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or calcium silicate to the water body comprising sulphates is carried out by dispensing the calcined mixture into the water body and / or a natural and / or artificially induced mixing is carried out after the addition, preferably wherein the mixing after the addition is carried out for at least 30 minutes, preferably at least 1 hour, preferably at least 2 hours.

10. A calcined mixture for binding sulphates in a water body, prepared by the method of: providing a mixture comprising calcium oxide and calcium and / or calcium aluminate; and calcining the mixture comprising calcium oxide and calcium and / or calcium aluminate and cooling the mixture to produce a calcined mixture for binding sulphates in a water body.

11. A product comprising bound sulphates, prepared according to the method of any one of claims 1 to 9.

12. Use of a mixture comprising CaO and at least one mineral of the gehlenite supergroup and / or comprising at least one calcium aluminosilicate and / or at least one calcium aluminosilicate and / or calcium silicate, in particular a powder mixture, and / or a calcined mixture according to claim 10 for binding sulphates in a water body.

Images