EP2782992A2 - Method for separating algae, in particular microalgae, from an aqueous phase, and a device for carrying out this method - Google Patents

Abstract

The present invention relates to a method for separating algae, in particular microalgae, from an aqueous phase, having the method steps: a) addition of at least one clay mineral, in particular an alternating-layer clay mineral, to the aqueous, algae-containing phase, and mixing the same, b) sedimentation of the resultant aqueous suspension of algae and clay mineral, forming an aqueous supernatant, and c) separating the sediment of algae and clay mineral from the aqueous supernatant. In addition, the invention relates to a device for carrying out this method.

Description

 A method for separating algae, in particular microalgae from an aqueous phase and an apparatus for carrying out this method

The present application relates to a process for separating microorganisms from an aqueous phase according to the preamble of claim 1, an apparatus for carrying out this process according to claim 19, a composition preparable by this process according to claim 25 and the use of this composition according to claim 26.

description

In the background of the worldwide efforts to reduce C0 ₂ emissions, their material use is increasingly coming to the fore. At present it is increasingly being investigated whether the metabolisation of C0 ₂ released by power plants by organisms occurring in the oceans, such as algae, phytoplankton or cyanobacteria, can be a viable option by means of photosynthesis. These organisms account for approximately half of the global carbon fixation through photosynthesis, with most of the fixed carbon returned to the atmosphere via the marine food chain as C0 ₂ . However, a smaller part of the bound C0 ₂ is deposited on the seabed.

It is known, with the help of microalgae - one to a few cell algae - to achieve a biomass using flue gas. Microalgae grow about 10 times faster than land plants, grow in salt, fresh water and wastewater and do not compete with agricultural land. They have a high diversity: about 30,000 described species therefore have great potential for a wide variety of substances that can be produced in the microalgae.

In such processes, the CO ₂ contained in the flue gas is fixed directly in the receiving biomass. The desulfurized flue gas is passed through a solution of microalgae, resulting in exponential growth of the microalgae. This type of C0 ₂ fixation is preferably carried out in a continuous process, for which a permanent removal of the biomass formed and its further processing are prerequisite. The yield of dry matter in biomass, depending on the optimization stage of the process between 0.3 and 0.8% by weight of dry matter. This means that an algal suspension consists of 99.2 to 99.7% by weight of water. Therefore, in addition to the increase in algae concentration, the treatment technology is essential. Due to the very small size of the microalgae from 5 to 15 μηι filtration is very difficult and centrifugation very energy-intensive and therefore very expensive. An estimated 85% of the total production costs are attributable to the processing technology for the dry product.

Depending on the possible uses of the microalgae, e.g. for biomass production for power generation, proteins for animal feed, fine chemicals and foodstuffs to pharmaceuticals and cosmetics prices for the algae of 1 € / kg, 10 € / kg and 100 € / kg. The current high producer prices have hitherto prevented the massive use of algae products, in particular for animal feed. Only through a strong reduction of processing costs can marketable prices be achieved.

In addition to filtration and centrifugation, further possibilities for separating off the biomass produced from microalgae are known from the prior art.

Thus, DE 10 2009 030 712 A1 describes a process for the separation of microalgae in which magnetic particles are added to the biomass produced and the biomass provided with the magnetic particles is deposited in a magnetic separation stage. Further use of the thus deposited microalgae e.g. However, as feed separates due to the magnetic particles contained.

From US 6,524,486 B2 the use u.a. of modified starch known as a flocculating agent. The starchy algae suspension is fed to a flotation column in which, by the introduction of dissolved gas, formation of an algae foam takes place, which is subsequently separated off. However, this method is not suitable for a large-scale approach to flue gas treatment.

It is therefore an object of the present invention to provide a process which enables the separation of microalgae from an aqueous phase, which in one can be used on an industrial scale and at the same time allows further use of the recovered microalgae eg as feed.

This object is achieved by a method having the features of claim 1 and a device having the features of claim 19.

Accordingly, a process is provided for separating algae, in particular microalgae, from an aqueous phase, which comprises the following process steps: a) addition of at least one clay mineral, in particular a changeover clay mineral, to the aqueous algae-containing phase and mixing thereof, b) sedimentation of the formed aqueous suspension, in particular flocculent suspension, of algae and clay mineral and formation of an aqueous supernatant, and. c) separation of the sediment from algae and clay mineral from the aqueous supernatant.

The idea underlying the method according to the invention thus consists of adsorbing or reversibly binding the algae present in an aqueous phase to a suitable agent so as to effect a rapid and gentle enrichment or concentration of the algae. A gentle treatment of the algae is important in order to avoid the destruction of the important cell constituents of the algae.

In particular, a specially prepared clay mineral with a high positive edge charge is coagulated by negatively charged algae by charge neutralization and then rapidly sedimented by flocculation of the clay particles and algae and preferably by means of metal salts as bridging images. By means of a vibration treatment, a further concentration is possible. In a strong centrifugal field, the algae-clay complex can be completely separated again into algae and clay mineral or the complex is further processed into a bio-mineral compound system of algae and clay mineral. The clay mineral takes over the function of a drug delivery system by protecting the active ingredients of the digested algae from destruction. In general, microorganisms - which include the microalgae - microscopically small organisms or organisms that are usually not recognizable as individuals with the naked eye. The microorganisms are predominantly unicellular, and some multicells of appropriate size are included. Microorganisms occur in different sizes. Some microorganisms are important for the nutrition, others are pathogens of infectious diseases.

Examples of microorganisms are bacteria z. As lactic acid bacteria, fungi z. B. baker's yeast S. cerevisiae, cyanobacteria (blue-green algae), microscopic algae z. B. chlorella, the u. a. be used as a dietary supplement, and protozoa z. B. the paramecium and the malaria parasite Plasmodium.

Of particular importance to the present process are microalgae which are suitable for human and animal nutrition and health maintenance.

The class of microscopic algae or microalgae preferably used herein includes the extensive group of chlorella such as Chlorella vulgaris, Chlorella angustoellipsoidea, Chlorella botryoides, Chlorella capsulata, Chlorella ellipsoidea, Chlorella emersonii, Chlorella fusca, Chlorella homosphaera, Chlorella luteo-viridis, Chlorella marina , Chlorella miniata, Chlorella minutissima, Chlorella mirabilis, Chlorella ovalis, Chlorella parasitica, Chlorella peruviana, Chlorella rugosa, Chlorella saccharophila, Chlorella salina, Chlorella spaerckii, Chlorella sphaerica, Chlorella stigmatophora, Chlorella subsphaerica, Chlorella trebouxioides.

Other preferred microalgae are of the genus Pediastrum, e.g. Pediastrum dupl, Pediastrum boryanum and the genus Botryococcus such as e.g. Botryococcus braunii.

The separation of the algae from an aqueous phase using a clay mineral can be understood here in the general sense as adsorption in the form of a physical process in which substances adhere to the surface of another substance and accumulate on its surface. The forces that cause adhesion are not chemical bonds but only physical forces. Therefore, this form of adsorption is called exact physical adsorption or physisorption. However, the adsorbed substance (adsorbate) does not form a chemical bond with the surface but instead adheres to weaker forces similar to adhesion. As a rule, only van der Waal's forces appear. The physical adsorption is reversible.

For the use of adsorbents, in particular for physisorption, their pore structure or the existing reaction surface is the most important factor. In order to ensure optimal utilization of the surface or the adsorption sites, the distribution of the cavities should be maximum, the wall thickness should be minimal. Therefore, the pore structure and the accessible surface per unit mass are often used as a quality criterion for an adsorbent.

Therefore, as adsorbents in particular those substances are used which have a high specific surface area or high porosity such as activated carbon, silica gel, sepiolite, zeolites or bentonites. These can be used in the form of beds or in structured form. Due to their very different ion uptake capacities, their application depends on the specific task.

According to the present method, clay minerals are used to separate the algae from an aqueous phase.

Clay minerals are generally classified into different groups depending on the layer structure. These include the group of kaolinites, smectites, lllites and chlorites.

A well-known representative of the clay minerals is montmorillonite, which belongs to the group of smectides as a three-layer dioctahedral silicate with a tetrahedral layer-octahedral layer-tetrahedral layer structure. Montmorillonite is a three-layer silicate with a high swelling capacity and thixotropy. In the fully delaminated state it can reach an accessible surface of up to 750 m ² / g. Montmorillonite is capable of ion exchange and chemical and physical adsorption. Most of the adsorption is via van der Waals forces and through hydrogen bonds.

The binding of organic substances to montmorillonite usually occurs through several mechanisms involving physical adsorption and chemosorption. Cationic substances are preferably exchanged for the cations contained in the montmorillonite and bound by chemosorption to the montmorillonite. These Mechanisms are controlled by the pH. The binding of anionic substances to montmorillonite is preferably carried out by physical adsorption, so that the substance can be released rapidly. Nonionic substances are often bound to montmorillonite via van der Waals forces and hydrogen bonds.

Montmorillonite has a remarkable swelling capacity. Water causes the interlayer cations to build up through hydration. The swelling process is called "intergranular swelling." Sodium montmorillonite can absorb six to seven times its dry weight of liquid, but in the presence of small amounts of solvent, the layers remain well-ordered, but as the solvent supply increases, the state of order is increasingly lost ,

Due to the physicochemical properties shown, montmorillonite is used in particular as a pharmaceutical excipient and as a bioactive agent, in particular as a detoxifier. Also, chemical agents can be bound and thus used for drug preparation.

Illit is the most common and common clay mineral and is found mostly in soils. It is also a dioctahedral three-layer silicate and shows a close relationship to the mica. It often arises from rock-forming aluminosilicates by diagenetic or hydrothermal processes and forms the main component of many marine clays. In addition to Si-Al replacement in the tetrahedra, their negative layer charge is also due to the replacement of Al ³⁺ by Mg ²⁺ and Fe ²⁺ in the octahedra. If illite particles are broken, additional positive edge charges result.

The frequently occurring in nature mineral compounds or matrices, with alternating storage clay minerals (mixed layer) as the main component, are used due to their lower compared to pure montmorillonite smaller measurable specific surface areas, swelling capacity and cation exchange capacities less often for adsorptive and catalytic applications.

It has now been found that naturally occurring mineral compounds or matrices of marine genesis consist of mixed layers or alternating storage minerals, which are composed of swellable and non-swellable layers in an irregular sequence and possibly also other minerals As silicates, oxides, carbonates, sulfides and sulfates contain, after appropriate treatment have quite adsorptive and other interesting properties.

Structurally, mixedlayer may consist of very different alternating layers of storage, e.g. Kaolinite / smectite, chlorite / vermiculite, mica / vermiculite or very frequently alternating storage of illite / smectite or illite / montmorillonite. As a result, more versatile exchange reactions of cations and anions are possible than with pure montmorillonites.

In one embodiment of the present invention, a clay mineral in the form of a changeover clay mineral is used.

Particularly preferred is a Wechsellagerungstonmineral of montmorillonite and illite / muscovite is used, which can be contained in this change storage mineral montmorillonite and illite / muscovite in a ratio of 60:40 to 40:60, with a ratio of 50:50 is preferred. That is, the montmorillonite and illite / muscovite may be contained at 50% by weight each.

In addition to the minerals montmorillonite and illite / muscovite, the preferred clay mineral may also include portions of other clay minerals such as kaolinites and chlorites, carbonates, sulfides, oxides and sulfates.

In a preferred embodiment, the clay mineral has a Fe ²⁺ / Fe ³⁺ ratio between 0.3 and 1.0, preferably 0.45 and 1.0. Thus, in the present clay mineral compound, the Fe ²⁺ / Fe ³⁺ ratio is approximately 10 times higher than in other known clay minerals and, due to this increased Fe ²⁺ / Fe ³⁺ ratio, additionally has a high natural antioxidant potential.

In a particularly preferred embodiment, the present clay mineral comprises on average 50-60% by weight, preferably 55% by weight of montmorillonite-muscovite alternating support, 15-25% by weight, preferably 20% by weight. 5-9% by weight, preferably 5% by weight of kaolinite / chlorite, 10-20% by weight, preferably 15% by weight of quartz, 1-2% by weight, preferably 1% by weight of calcite, 0.9-1.5, preferably 1% by weight Dolomite, 0.9-1.9% by weight, preferably 1% by weight of feldspar, 0.9-1.0% by weight, preferably 1% by weight of pyrite and 0.6-1.0% by weight, preferably 1% by weight of gypsum. The chemical composition of the main elements can be given in% by weight as follows: Si0 ₂ 57.9-59.5; Al ₂ O ₃ 17.0-18.5; Fe ₂ 0 ₃ 5.9-7.0; K ₂ 0 2.8-3.5; MgO 1, 5-2.6; Na ₂ 0 0.9-1.5; TiO ₂ 0.6-1.5; CaO 0.25-0.35; P ₂ 0 ₅ 0.09-0.15; Other 8.9-10.5.

The clay mineral preferably used has an internal (BET) surface area of 50-100 m ² / g, preferably 55-65 m ² / g, particularly preferably 60 m ² / g. The inner surface of the clay mineral which is preferably used is thus relatively low, for example, in comparison with the highly swellable montmorillonites. The average particle size of the mineral compound preferably used may be in a range of 0.1 to 10 μm, preferably 0.5 to 1 μm, in particular 0.5 μm.

The preferred clay mineral is isolated and processed from the clay deposits present in Germany in Mecklenburg-Western Pomerania, more precisely in the vicinity of Friedland in the eastern part of the Mecklenburg Lake District.

The clay mineral preferably used has, as already mentioned above, unique properties in which it differs substantially from other mineral matrices such as bentonite or montmorillonite.

Thus, the clay mineral used here is not only able to exchange cations in the existing montmorillonite layers, but also to bind anions. The mechanism of action of the presently used mineral compound is therefore different from bentonites. For example, anionic substances are loosely bound to the break edges of the illites / muscovites contained in the mineral compound used. The reason for this are missing or knocked out potassium ions, which ensure a charge balance in the mineral compound. This results in positive charges, where anions can be loosely bound. Since bioactive anions have a relatively high molecular mass and thus diameter, the recesses formed at the fracture edges are not large enough to realize a firm bond. This is only possible with smaller molecules, as evidenced by the very high adsorption power for especially oxygen-containing molecular anions such as phosphate P0 ₄ ^{3 ~} , nitrate N0 ₃ ^" , nitrite N0 ₂ ^" and others. Here, the Fe ²⁺ ions at the breaklines play a crucial role, as these can act as counterions.

The higher the positive edge charge, the better the degree of separation of the algae, especially the microalgae. The superficially negatively charged algal cells are transduced van der Waals forces are loosely bound to the positively charged clay edges, which have charges of Fe, Fe ³⁺ , Al ³⁺ , Mg ²⁺ .

In one embodiment, 1 kg to 15 kg, preferably 2 kg to 10 kg, particularly preferably 3 to 8 kg of clay mineral per kg of dry algae in the aqueous phase (an aqueous phase of 1000 I with an algal content of 0.3% corresponds to 3 kg Algentrockenmasse) was added.

In one embodiment of the present method, the aqueous phase has an algal content of between 0.01 and 5 mass%, preferably between 0.1 and 1.5 mass%, in particular between 0.1 and 0.6 mass%. Thus, typically up to 99.99% of the aqueous phase is water and the concentration of algae in the aqueous phase is correspondingly low.

Preferably, at least one polyvalent cation, in particular a divalent or trivalent cation, is added to the at least one clay mineral or a mixture of clay mineral and cation is produced. The polyvalent cation is preferably selected from a group containing Fe ²⁺ , Ca ²⁺ , Mg ²⁺ , Fe ³⁺ and Al ³⁺ . By adding the polyvalent cations in particular the sedimentation or flocculation of the alga-clay mineral composite is supported, as described in more detail below.

The polyvalent cation may be added in the form of a chloride salt and / or sulfate salt, with the addition of MgCl ₂ and MgSO ₄ being particularly preferred. The amount of salt added, in particular of MgCl ₂ or MgSO _4, is preferably from 1 kg to 10 kg, preferably from 1 kg to 5 kg, particularly preferably 2 kg per kg of algae dry mass in the aqueous phase.

The preferred use of magnesium chloride leads to bridging between the negative surfaces of the clay mineral and the algae. It produces flakes of algae-clay-magnesium, which sediment relatively quickly. The precipitating flakes of algae-clay-magnesium include other disperse substances, such as very fine clay particles, in the resulting flakes. This gives a completely clarified process water from the biomass production with a neutral pH, which can be reused and used, for example, for a circulation mode of operation. The use of MgCl ₂ has the further advantage that an additional source of magnesium will be provided in a later use of the deposited system of algae and clay mineral as a food supplement for animal and human. This is an advantage, magnesium is essential for humans and animals.

The present method thus fulfills a number of conditions which enable efficient separation of algae and at the same time contribute to the formation of a biomineral composite system and its further use. Thus, only those materials will be used for the formation of the bio-mineral composite system, which does not endanger the health of humans and animals. The components of the composite system complement each other synergistically and have positive effects on the state of health. The mineral compound as part of the composite system also serves as a concentration aid for the microalgae biomass. For flocculation only those polyvalent metal ions are used, which are essential for humans and animals. The reuse of the process water from the Aigenbiomasseproduktion is ensured. The concentration process takes place at neutral pH.

The mixing of the clay mineral as an adsorbent and the algae in the aqueous phase is preferably carried out using a stirrer or an optimal flocculation device, such as a stirrer. the FlocFormer from Cutec.

By mixing the clay mineral with the aqueous phase containing the algae, a suspension is formed. Under a suspension is generally understood a heterogeneous mixture of a liquid and finely divided solids therein. A suspension is a coarsely dispersed dispersion and tends to sediment and phase separate.

As described, the gravitational sedimentation following suspension formation is assisted by the addition of polyvalent cations.

The sedimentation rate is moreover dependent on geometric factors of the apparatus used for the adsorption and sedimentation, the properties of the clay mineral used as adsorbent and other supporting measures and under optimal conditions is at least 1.2 cm / min, preferably at least 1.5 cm / min. The sediment of algae adsorbed on the clay mineral settles out as a solid, the end of the settling process being measured photometrically via the turbidity of the aqueous supernatant.

The algae-clay mineral sediment is preferably separated in the form of a thick matter mixture, preferably with a water content of 50-60% in step c). The concentration of the algae, in particular of the microalgae, is increased by a factor of at least 30, preferably by a factor of 50, by the combination of adsorption and subsequent sedimentation.

Due to the flocculation of the algae-clay-magnesium complex in the gravitational field, depending on the waiting time, the process water can be separated by up to 90%. In the remaining alga-clay mineral suspension, a residual water content of 70 to 90% by mass can be achieved, i.e., 10 to 30% dry matter consists of the algae clay mineral opt. Magnesium complex.

In a further process step, it is possible to separate the algae-clay mineral complex, which is preferably provided with cations such as magnesium ions, in a centrifugal field> 500 G again into its individual parts. This makes it possible to produce pure algae concentrates. The separated clay particles can be returned to the flocculation process. This centrifugal treatment of the algae-clay mineral complex can be carried out before separation from the aqueous supernatant as well as after separation from the aqueous supernatant.

In a further variant of the method, it is possible to densify the sediment of algae and clay mineral by means of a vibration treatment. This can be done before the separation of the sediment from the aqueous supernatant and after the separation. A subsequent vibration treatment with a frequency of 500 to 1000 min ^"1 further compresses the algae-clay complex to a residual water content of 50 to 60% by mass.This viscous suspension is well suited for digesting the algae cells with a high-pressure slit homogenizer or in a high-performance ultrasound field.

After the flocculation and compression process, a pumpable, gel-like algae-clay-magnesium complex is available for further processing. The separation of the sediment from algae and clay mineral from the aqueous supernatant can be carried out, for example, by means of decanting or other separation processes known to a person skilled in the art. The separated aqueous supernatant is processed and returned to the production of algae.

In another variant of the present method, the sediment separated in step c) from algae adsorbed on the clay mineral can be treated by means of ultrasound in a further step. The ultrasound treatment in this step causes, on the one hand, a homogenization of the separated sediment and, on the other hand, a cell disruption of the microorganisms, such as e.g. the microalgae to release bioactive substances contained therein. The released during the digestion process bioactive substances are stored in the clay-gel matrix and thus protected from environmental influences. The result is a bio-mineral algae clay mineral opt. Magnesium complex.

Subsequently, the algae-clay mineral sediment separated according to step c) and / or the ultrasonically treated algae-clay mineral sediment may preferably be dried in a drying step. The drying can be carried out by means of per se known methods such as spray drying, belt dryer or in the drying oven.

A preferred drying method is vacuum drying. The drying temperatures should not exceed 50 ° C. By constantly moving in a thin layer, the drying energy is optimally utilized.

Another suitable drying method is spray drying. The highly concentrated e.g. 50% algae-mineral suspension is pumpable and can be fed to the drying apparatus. The injection creates a high drying surface, which ensures extremely fast and gentle drying. During drying, the mineral, in particular the swollen clay mineral, contracts and includes the digested components of the microorganisms, in particular the microalgae, by the formation of granules.

The drying is preferably carried out to a final moisture content of the algae-clay mineral sediment of about 5 to 15 Ma% H ₂ 0 content, in particular from 6 to 9 Ma% H ₂ 0 content. The algal content of the dried algae-clay mineral sediment may be between 10-50 Ma%, preferably 20-40 Ma%, in particular 35 Ma%. Thus, the drying process can be stopped at a residual moisture content of about 6% by mass, with a bio-mineral composite system of algae, clay and possibly magnesium is obtained with an algae content of about 35 Ma%.

By the drying process, the water is removed from the adsorbent, e.g. removed the layer interstices of clay minerals and the bioactive substances that were not accumulated by physical adsorption, bound by a form-locking composite. The result is a reversible, biomineral composite system. As a result of adsorption and drying, a material and positive bond between the particles of the mineral and the adsorbed and trapped bioactive substances of the microorganisms is produced.

It comes to the formation of reversible aggregates, which can be brought into dispersion or disaggregated by adding a suitable solvent, in particular of water.

The dried sediment from microorganisms such as e.g. Microalgae and adsorbents, e.g. Clay mineral, open-minded or non-unlocked, can then be packed and shipped.

In a particularly preferred embodiment, the present method comprises the following steps:

Addition of at least one clay mineral, in particular a conditioned alternate storage clay mineral, to the aqueous phase containing algae and mixing the same to coagulate clay particles and alga,

Addition of a metal salt for bridging between the negatively charged particles and the optimal formation of flakes,

- Sedimentation of the formed flakes of algae, clay mineral and metal salt in the gravitational and / or centrifugal field, and

- Compaction of sediment from algae and clay mineral by means of a vibration treatment. Complete separation of the algae-clay-metal ion complex in the strong centrifugal field in algae and clay mineral or

Algae digestion within the gel-like algae-clay-metal ion complex by means of a high-pressure slit homogenizer or in a high-power ultrasound field.

The composition of algae, in particular microalgae, and at least one clay mineral produced by means of the present process can be used for the production of animal feeds, nutritional supplements and / or pharmacologically active agents.

Animal models have shown that disrupted algae cells have a much better digestibility and efficacy. Both the cell constituents and the bioactive substances in the cell membrane can be active substances.

In the present bio-mineral composite system, the clay mineral has two functions: the first task is the function of a drug delivery system. The bioactive substances of the algae, which are loosely integrated into the mineral matrix, are protected against destruction by gastric acidity during gastric passage. At a pH of about 7.5 in the small intestine, the clay swells and releases the bioactive substances. Thereafter, the clay serves as the second task as Toxic Clearance System for toxins in the gastrointestinal tract. This applies to both human and veterinary use.

The present method is preferably carried out in a device having the features of claim 19.

Accordingly, the device for carrying out a method for separating algae from an aqueous phase comprises at least two sections coupled to one another, wherein a first section is arranged above the second section relative to the direction of gravity. The first portion and the second portion may be integral with each other e.g. be formed in the form of a reactor or can also be spatially separated from each other e.g. be arranged in the form of two separate containers.

The at least first portion consists of at least one container for holding the aqueous phase containing the algae and the at least one clay mineral as adsorbent, and the at least second portion consists of at least one Tube for sedimentation of the aqueous suspension of algae and adsorbent formed in the first region.

In one variant, the first section in the form of a container has at least one inlet for the aqueous phase containing the algae, at least one opening for adding the adsorbent and optionally at least one agitator. In this container, thus, the mixing of the biomass from algae with the adsorbent and the addition of a multivalent cation salt and at the beginning of the sedimentation take place. This first section is also called turbulent mixing zone.

In a further variant, the second section of the device comprises a tube system comprising at least two tubes, preferably from 2 to 10 tubes, particularly preferably from 2 to 5 tubes. The tube system allows laminar sedimentation, so that the sedimentation of the seaweed-laden clay mineral is free of flow influences and takes place at the bottom of the respective tubes of the tube system. The second section can thus be divided into a laminar settling zone and a compression zone.

In addition, the present device may incorporate one with the second section, i. Having the third system coupled to the tube system for the removal of accumulated at the bottom of the second section microorganism adsorbent sediment in the form of a sampling chamber. The sampling chamber has an opening suitable for removing the sediment, e.g. in the form of a valve cock, which can be controlled manually or photometrically.

The present invention will be explained in more detail with reference to several embodiments with reference to the figure. It shows

Figure 1 is a schematic representation of a device suitable for carrying out the method according to the invention.

Figure 1 shows a preferred embodiment of a device 1 in the form of a settling apparatus suitable for carrying out the method according to the invention. The device 1 comprises two mutually coupled sections 2, 3, wherein the first section 2 is arranged with respect to the direction of gravity above the second section 3. The first section 2 consists of at least one cylindrical container for receiving the aqueous, microalgae-containing phase 4 and a clay mineral 5 as adsorbent. The second section 3 consists of a tube system of five tubes running parallel to one another for sedimentation of the aqueous suspension of microalgae and clay mineral formed in the first region 2.

The first section 2 in the form of a cylindrical container has an inlet for the microalgae-containing aqueous phase 4 and an opening in the form of a pouring opening for adding the clay mineral 5, through which the MgCl _{2 is also} supplied.

In addition, the container 2 in the embodiment of Figure 1 has a stirrer 6. In the container 2 thus takes place the mixing of the biomass of microalgae, clay mineral and MgCl ₂ . This area can also be considered as a turbulent mixing zone.

After setting the appropriate isoelectric point, the gravitationally controlled sedimentation of microalgae 4 adsorbed on the clay mineral 5 begins immediately in the tubes of the tube system 3. The tube system allows laminar sedimentation so that sedimentation of the microalgae-containing adsorbent in the laminar settling zone 3b is free from Flow influences is.

The settled in the compression zone 7 in the lower region of the tube system 3 sediment is removed from the device 1 in a coupled to the tube system 3 sampling chamber 8. The extraction chamber 8 has an opening suitable for removing the sediment, e.g. in the form of a valve cock, which can be controlled manually or photometrically.

Embodiment 1

An aqueous phase with a proportion of microalgae biomass of 0.3% is mixed with 9-12 kg of clay flour per 1 000 liter of algal biomass and mixed intensively with one another in the process vessel 2 of the settling apparatus 1 using an agitator. The resulting suspension of microalgae and clay flour will then sediment at rest its solid content of microalgae and clay. The solid sediments in the tubes 3 below the process container 2, wherein it does not matter that all tubes absorb the same amount of solid. It is important that the sedimentation can take place free of flow. The process of sedimentation can be regarded as complete when the solid has collected in the form of a thick matter mixture at the foot of the tubes and only a slight turbidity is to be measured in the upper area.

The thick matter of microalgae and clay is removed from the removal chamber 8 of the settling apparatus 1 via a valve cock and has a moisture content of about 50% H ₂ 0.

Further processing takes place by means of spray drying at a short-term drying temperature of up to Ι δδ'Ό. The dried composition is then pelletized.

When using a starting material of microalgae with a solids content of 0.3%, this results in 3 kg of algae dry matter per 1000 l algal biomass and with the addition of 9 - 12 kg of clay flour per 1000 I algal biomass resulting in 12-15 kg dry matter of the active ingredient mixture.

Embodiment 2

An aqueous phase with a proportion of microalgae biomass of 0.3%, equivalent to 3 kg of algae dry matter, is mixed with 6 kg of treated clay mineral per 1 000 liter of algal biomass and mixed intensively with one another in the process vessel 2 of the settling apparatus 1 using an agitator. It comes to coagulation of algae and clay particles. Subsequently, the algae clay suspension 6kg MgCl ₂ ^* 6H ₂ 0 is added. Bridges are formed between the negatively charged particles with the help of the positively charged magnesium ion. The resulting flakes of microalgae, mineral salt and clay mineral begin to sediment. The flock complex sediments in the tubes 3 below the process container 2, wherein it does not matter that all tubes absorb the same amount of solid. It is important that the sedimentation can take place free of flow.

The process of sedimentation can be regarded as complete when the solid has collected in the form of a thick matter mixture at the foot of the tubes and in the upper area only a clear supernatant can be seen. The flaky sediment of microalgae, mineral salt and clay mineral is further compressed by a vibration treatment at about 800 min ^"1 . The thick matter of microalgae and clay is removed from the removal chamber 8 of the settling apparatus 1 via a valve cock and has a moisture content of about 50% H ₂ 0.

Further processing takes place by means of vacuum drying at a surface temperature of 50 'Ό in a thin moving layer. At a residual moisture content of 6% by mass, approx. 10 kg of the bio-mineral composite system consisting of algae, magnesium and clay mineral can be removed from the apparatus to make them free-flowing.

Claims

claims 1 . A method for separating algae, in particular microalgae, from an aqueous phase characterized by the method steps a) adding at least one clay mineral, in particular a Wechsellagerungstonmineral to the aqueous, algae-containing phase and mixing derselbigen, b) sedimentation of the formed aqueous suspension of algae and clay mineral forming an aqueous supernatant, and c) separating the sediment from algae and clay mineral from the aqueous supernatant. 2. The method according to claim 1, characterized in that the aqueous phase has an algal content between 0.01 and 5 mass%, preferably between 0.1 and 1, 5 mass%, particularly preferably between 0.1 and 0.6 mass% , 3. The method according to claim 1 or 2, characterized in that the at least one clay mineral in a mixture with at least one polyvalent cation, in particular a divalent or trivalent cation, the aqueous algae phase is added. 4. The method according to claim 3, characterized in that the polyvalent cation is selected from a group containing Fe ²⁺ , Ca ²⁺ , Mg ²⁺ , Fe ³⁺ or Al ³⁺ . 5. The method according to claim 3 or 4, characterized in that the polyvalent cation in the form of a chloride salt and / or sulfate salt is added. 6. The method according to any one of claims 3 to 5, characterized in that the salt of the polyvalent cation, in particular MgCl ₂ or MgS0 ₄ in an amount of 1 kg to 10 kg, preferably 1 kg to 5 kg, more preferably 2 kg per kg Algentrockenmasse is used in the aqueous phase. 7. The method according to any one of the preceding claims, characterized in that a change storage clay mineral consisting of montmorillonite and illite / muscovite is used as the clay mineral. 8. The method according to any one of the preceding claims, characterized in that the clay mineral is a Wechsellagerungstonmineral comprising montmorillonite and illite / muscovite is used in each case at least 50% by weight. 9. The method according to any one of the preceding claims, characterized in that the clay mineral contains other clay minerals such as kaolinites and chlorites. 10. The method according to any one of the preceding claims, characterized in that the clay mineral has a Fe ²⁺ / Fe ³⁺ - ratio between 0.3 and 1, 0, preferably 0.45 and 1, 0. 1 1. Method according to one of the preceding claims, characterized in that the clay mineral 50-60 wt% montmorillonite muscovite WL, 15-25 wt% illite / muscovite, 5-9 wt% kaolinite / chlorite, 10-20 wt% quartz, 1 -2 wt% calcite, 0.9-1.5 wt% dolomite, 0.9-1.9 wt% feldspar, 0.9-2.0 wt% pyrite and 0.6-1.0 gypsum. 12. The method according to any one of the preceding claims, characterized in that the clay mineral has a BET surface area of 50 -100 m ² / g, preferably 55-65 m ² / g, particularly preferably of 60 m ² / g. 13. The method according to any one of the preceding claims, characterized in that the clay mineral particles having an average particle size of 0.1 to 10 μηι, preferably 0.5 to 1 μιτι, in particular of 0.5 μηι comprises. 14. The method according to any one of the preceding claims, characterized in that the algae-clay mineral sediment is separated in the form of a thick matter mixture in step c). 15. The method according to any one of the preceding claims, characterized in that the separated in step c) algae-clay mineral sediment is treated in a further step by means of vibration and compacted. 16. The method according to any one of the preceding claims, characterized in that the separated according to step c) algae-clay mineral sediment and / or by means of vibration treated algae-clay mineral sediment to separate alga and clay mineral is centrifuged. 17. The method according to any one of the preceding claims, characterized in that the algae of the algae-clay mineral sediment are digested. 18. The method according to any one of the preceding claims, characterized in that the algae-clay mineral sediment, in particular the digested algae-clay mineral sediment is dried. 19. Device (1) for carrying out a method comprising the method steps according to one of the preceding claims  - At least two mutually coupled portions (2, 3), wherein the first portion (2) with respect to the direction of gravity above the second portion (3) is arranged, and wherein  - The at least first section (2) consists of at least one container for receiving the aqueous, algae-containing phase (4) and the at least one clay mineral (5), and  - The at least second section (3) consists of at least one tube (3a) for sedimentation of the aqueous suspension of algae and clay mineral formed in the first region (2). 20. The apparatus according to claim 19, characterized in that the at least two sections (2, 3) are arranged integrally or spatially separated from each other. 21. Apparatus according to claim 19 or 20, characterized in that the second portion (3) of at least one tube (3a) in at least one laminar settling zone (3b) and a compression zone (7) is divided. 22. Device according to one of claims 19 to 21, characterized in that the first section (2) as a turbulent mixing zone at least one inlet for the aqueous, algae-containing phase (4), at least one opening for adding the clay mineral (5) and, if necessary at least one agitator (6). 23. Device according to one of claims 19 to 22, characterized in that the second section (3) comprises a tube system of at least 2 tubes, preferably from 2 to 10 tubes, more preferably from 2 to 5 tubes. 24. Device according to one of claims 19 to 23, characterized by a second section (3) coupled to the third section (8) for removing the algae-clay mineral sediment formed in the second section (3). 25. Composition of algae, in particular microalgae, and at least one clay mineral, in particular in the form of a bio-mineral composite system produced by a process according to one of claims 1 to 18. 26. Use of a composition of algae, in particular microalgae, and at least one clay mineral according to claim 25 for the production of animal feed, dietary supplements and / or pharmacologically active agents.