An oleic acid-based DES liquid, its preparation method, and its application in the efficient concentration of anaerobic fermentation liquid

Abstract

An oleic acid-based DES liquid, a preparation method thereof, and its application in the efficient concentration of anaerobic fermentation liquid. The present invention belongs to the field of resource recovery and utilization of fermentation liquid. The purpose of the present invention is to provide an oleic acid-based DES liquid, a preparation method thereof, and its application in the efficient concentration of anaerobic fermentation liquid. The present invention uses non-toxic, easily degradable oleic acid as the main raw material to invent a new oleic acid-based DES liquid. The synthesis method is simple, and it has the advantages of being easy to operate, easy to separate from water, and able to be recycled when used in fields such as dehydration and concentration. The new oleic acid-based DES liquid developed by the present invention has different hydrophilic properties at different temperatures. Therefore, it can be separated from water by simply adjusting the ambient temperature, and recycled, which greatly reduces the cost of use and separation costs. The recycled new oleic acid-based DES liquid can also reduce the harm to the environment caused by improper treatment.

Description

Technical Field

[0001] The invention belongs to the field of fermentation liquid resource recycling and utilization, and particularly relates to an oleic acid-based DES liquid and a preparation method thereof, and application of the oleic acid-based DES liquid in the efficient concentration of anaerobic fermentation liquid. Background Art

[0002] In recent years, the production of food waste has continued to increase, but a large portion of this waste remains untreated, causing secondary environmental pollution and wasting resources. Research has shown that food waste can be used for anaerobic fermentation to produce large quantities of volatile fatty acids (VFAs), which can be subsequently recycled. However, due to cost and energy constraints, separating and purifying VFAs from fermentation broths is a challenge. Currently, methods such as evaporation, electrodialysis, and forward osmosis are used to concentrate fermentation broths. However, forward osmosis is considered the best option due to its high antifouling properties, high water recovery rates, low operating costs, and low / no hydraulic requirements. However, commonly used forward osmosis extractants, such as NaCl, NH₄HCO₃, and MgCl₂, require recovery by reverse osmosis or evaporation, which is costly and energy-intensive. Furthermore, common organic extractants have relatively low water fluxes. Therefore, a new, ideal forward osmosis extractant is urgently needed.

[0003] Deep eutectic solvents (DESs) are a class of solvents that form eutectic mixtures of two or more compounds and have lower eutectic points than the individual compounds. The molecular structure of DESs can be in the form of cation-anion pairs, molecule pairs, or molecule-ion pairs, and their properties are similar to those of traditional ionic liquids (ILs). They have attracted considerable attention in recent years due to their simple synthesis, ease of operation, and low cost. Typically, the cations and anions in DESs are relatively large organic molecules, and the interactions between them are strong, allowing them to form very stable ion pairs. Furthermore, the physical and chemical properties of DESs can be tuned by selecting different cations and anions, thus meeting diverse application requirements. Therefore, DESs can be used as green solvents, drug delivery vehicles, energy storage media, and more. In summary, as a new type of green solvent, DESs offer numerous advantages and broad application prospects, playing an important role in achieving green chemistry and sustainable development. However, several challenges remain in their practical application, such as their toxicity, biodegradability, and stability, which require further research.

[0004] The application of DESs in dehydration is mainly reflected in two aspects: first, as a dehydrating agent, ionic liquids can be used as dehydrating agents to remove water due to their low volatility and high stability. The advantage of dehydration is that it can avoid the toxicity and environmental pollution caused by traditional dehydrating agents. At the same time, ionic liquids can be reused, reducing costs. Secondly, DESs can be used as reaction media and can carry out chemical reactions under anhydrous conditions. However, DESs also have many disadvantages in dehydration, such as high production costs; improper handling can easily cause harm to the environment; high difficulty in operation, etc., especially the high cost of safe handling and recovery, which often requires additional equipment, especially when separating from water, which is very expensive. Currently, some commonly used DESs are more or less difficult to separate from water or are toxic. For example, Cho-urea DESs are one of the most commonly used DESs, but they are highly soluble in water, making separation difficult. Eth-gly DESs are also highly soluble in water, and their environmental toxicity has not been fully studied. Therefore, developing a green solvent that is easily separable from water and non-toxic is a technical challenge that urgently needs to be overcome. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an oleic acid-based DES liquid, a preparation method thereof, and its use in the efficient concentration of anaerobic fermentation broth.

[0006] The present invention provides the following technical solutions:

[0007] One of the objectives of the present invention is to provide an oleic acid-based DES liquid, which comprises oleic acid and an acceptor material.

[0008] As a preferred embodiment of the oleic acid-based DES liquid of the present invention, the receptor material is tetracaine or procaine.

[0009] As a preferred embodiment of the oleic acid-based DES liquid of the present invention, the molar ratio of oleic acid to the acceptor material is 1:(1-10).

[0010] A second object of the present invention is to provide a method for preparing an oleic acid-based DES liquid, the preparation method being as follows:

[0011] The receptor material, oleic acid and water are added into a container, sealed, and magnetically stirred at a certain temperature until a clear and transparent homogeneous solution is formed to obtain an oleic acid-based DES liquid.

[0012] As a preferred embodiment of the method for preparing the oleic acid-based DES liquid of the present invention, the certain temperature is 20-60°C.

[0013] A third object of the present invention is to provide an application of an oleic acid-based DES liquid in the efficient concentration of anaerobic fermentation broth.

[0014] A fourth object of the present invention is to provide a method for concentrating acetic acid in anaerobic fermentation broth of food waste using oleic acid-based DES liquid with low consumption and high efficiency, the method being carried out according to the following steps:

[0015] S1: anaerobic fermentation of the food waste slurry after pretreatment of the food waste is performed at an inoculum ratio of 4:1. After fermentation, acetic acid is separated using a microfiltration membrane to obtain a fermentation liquid to be concentrated;

[0016] S2: The oleic acid-based DES liquid and the fermentation liquid to be concentrated are respectively transported to the hollow fiber permeation membrane for forward osmosis concentration treatment to obtain concentrated acetic acid and a mixed solution of water and DES.

[0017] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation broth of food waste using oleic acid-based DES liquid with low consumption and high efficiency, the pretreatment in S1 is sequentially performing high-temperature cooking, oil extraction, and solid-liquid separation.

[0018] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation liquid of food waste with oleic acid-based DES liquid at low consumption and high efficiency, the anaerobic fermentation parameters in S1 are: pH value of 8-10, temperature of 35-40°C.

[0019] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation broth of food waste with oleic acid-based DES liquid at low consumption and high efficiency according to the present invention, the conveying speed of the fermentation broth to be concentrated in S2 is 375-625 mL / min.

[0020] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation broth of food waste with oleic acid-based DES liquid at low consumption and high efficiency, the delivery speed of the oleic acid-based DES liquid in S2 is 1-3 times that of the fermentation broth to be concentrated.

[0021] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation broth of food waste with oleic acid-based DES liquid at low consumption and high efficiency, the working temperature of the forward osmosis concentration in S2 is 10-20°C.

[0022] As a preferred embodiment of the method for concentrating acetic acid in anaerobic fermentation broth of food waste with oleic acid-based DES liquid at low consumption and high efficiency according to the present invention, the hollow fiber permeable membrane in S2 is a water channel protein membrane.

[0023] A fifth object of the present invention is to provide a method for recycling the mixed solution of water and DES obtained by the above-mentioned method for concentrating acetic acid, wherein the method is carried out according to the following steps:

[0024] The mixture of water and DES is connected to a temperature regulating box, and the solution is heated or cooled within a temperature range of 10-40°C to separate the water and DES, and the DES is then transported back to the hollow fiber permeation membrane for recycling.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention uses non-toxic and easily degradable oleic acid as the main raw material to invent a new oleic acid-based DES liquid. The synthesis method is simple and has the advantages of being easy to operate, easy to separate from water, and recyclable in the fields of dehydration and concentration.

[0027] (2) The novel oleic acid-based DES liquid developed in the present invention has different hydrophilic properties at different temperatures. Therefore, it can be separated from water by simply adjusting the ambient temperature and recycled, which greatly reduces the cost of use and separation. The recycled novel oleic acid-based DES liquid can also reduce the harm to the environment caused by improper treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process of concentrating acetic acid according to the present invention. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0032] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0033] When amount, concentration or other value or parameter are represented with the range of scope, preferred range or a series of upper preferred value and lower preferred value limit, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope "1 to 5", described scope should be interpreted as including scope "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within the scope.In this application specification and claims, range limitation can be combined and / or interchanged, and if these ranges are not otherwise stated, include all subranges contained therein.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0035] The hollow fiber membrane used in the following examples is a water channel protein membrane with a pH tolerance range of 3 to 10 and a maximum operating temperature of 45°C. Its pure water flow rate is >27.6 L·(hr) -1 , reverse salt flux <3g·(m 2 h) -1 , effective area is 2.3m 2 The fiber inner diameter was 195 μm and the thickness was 35 μm. The peristaltic pump used was BJ-300, Baoding Lange.

[0036] Example 1:

[0037] A method of using oleic acid-based DES liquid to concentrate acetic acid in anaerobic fermentation liquid of food waste with low consumption and high efficiency in this embodiment is carried out by the following steps:

[0038] Step 1: Preparation of oleic acid-based DES liquid:

[0039] Oleic acid, tetracaine and water were added to a round-bottom flask at a molar ratio of 1:5. The flask was sealed with a cap and heated in a 60°C water bath with magnetic stirring until a clear, homogeneous solution was formed, thereby obtaining an oleic acid-based DES liquid with a concentration of 37 wt.%.

[0040] Step 2: Separate acetic acid from kitchen waste:

[0041] First, the kitchen waste (from Wuxi Huilian Thermal Power Co., Ltd.) was subjected to high-temperature cooking, oil extraction, and solid-liquid separation to obtain kitchen waste slurry.

[0042] Then, anaerobic fermentation was carried out using the food waste pulp as a substrate and the anaerobic sludge as an inoculum at an inoculum ratio of 4:1. The pH of the anaerobic fermentation was controlled at 8 and the temperature was controlled at 35° C. to obtain a fermentation liquid.

[0043] Next, a flat ceramic membrane with a pore size of 50 nm was used as a microfiltration membrane to separate acetic acid from the fermentation broth, thereby obtaining an initial fermentation broth with an acetic acid concentration of 26.62 g / L, namely the fermentation broth to be concentrated (pH=5.5).

[0044] Step 3: Low-consumption and high-efficiency concentrated acetic acid:

[0045] The fermentation broth to be concentrated obtained in the second step was transferred to a hollow fiber membrane via a peristaltic pump. The oleic acid-based DES liquid with a concentration of 37 wt.% obtained in the first step was used as the draw liquid. The draw liquid was transferred to the hollow fiber membrane via another peristaltic pump, where the acetic acid was concentrated by forward osmosis for 10 minutes. The fermentation broth to be concentrated was transferred at a rate of 500 mL / min, the draw liquid was transferred at a rate of 500 mL / min, and the forward osmosis operating temperature was 20°C, resulting in a concentrated acetic acid and a mixture of water and DES.

[0046] Step 4: Recycling of DES:

[0047] The mixed solution of water and DES obtained in the third step is introduced into a temperature regulating box, and the solution temperature is adjusted to 25°C to separate the water and DES, and the DES is re-transported to the hollow fiber permeation membrane for recycling.

[0048] The results showed that the acetic acid concentration of the concentrated fermentation liquid was 79.59 g / L, the acetic acid concentration ratio was about 2.8 times, and the DES recovery rate was 91%.

[0049] Example 2

[0050] The difference between this embodiment and embodiment 1 is that the draw liquid is replaced by oleic acid-based DES liquid with a concentration of 23 wt.%. The other steps and parameters are the same as those in embodiment 1.

[0051] The results showed that the acetic acid concentration of the fermentation liquid was 105.68 g / L, the acetic acid concentration ratio was about 4.0 times, and the DES recovery rate was 93%.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that the pH value of the fermentation liquid to be concentrated is changed from 5.5 to 3.5. The other steps and parameters are the same as those in embodiment 1.

[0054] The results showed that the acetic acid concentration of the fermentation liquid was 109.68 g / L, the acetic acid concentration ratio was about 4.1 times, and the DES recovery rate was 95%.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 3 is that the drawing liquid is replaced with 3M NaCl solution. Other steps and parameters are the same as those in Example 1.

[0057] The results showed that the acetic acid concentration of the fermentation liquid was 75.39 g / L, the acetic acid concentration ratio was about 2.8 times, and the NaCl recovery rate was 87%.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 3 is that the drawing liquid is replaced with 2MM MgCl2 solution. Other steps and parameters are the same as those in Example 1.

[0060] The results showed that the acetic acid concentration of the fermentation liquid was 95.57 g / L, the acetic acid concentration was about 3.6 times, and the MgCl2 recovery rate was 85%.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for concentrating acetic acid in anaerobic fermentation broth of food waste using oleic acid-based DES liquid with low consumption and high efficiency, characterized in that: Follow these steps: S1: anaerobic fermentation of the pretreated food waste slurry at a substrate to inoculum ratio of 4:1 is performed, and acetic acid is separated using a microfiltration membrane after fermentation to obtain a fermentation liquid to be concentrated; S2: transporting the oleic acid-based DES liquid and the fermentation liquid to be concentrated to the hollow fiber permeation membrane for forward osmosis concentration treatment, thereby obtaining concentrated acetic acid and a mixture of water and DES; The oleic acid-based DES liquid comprises oleic acid and a receptor material; the receptor material is tetracaine or procaine.

2. The method according to claim 1, characterized in that The molar ratio of oleic acid to the acceptor material in S2 is 1:(1-10).

3. The method according to claim 1, characterized in that The preparation of the oleic acid-based DES liquid described in S2 includes the following: The receptor material, oleic acid and water are added into a container, sealed, and magnetically stirred at a certain temperature until a clear and transparent homogeneous solution is formed to obtain an oleic acid-based DES liquid.

4. The method according to claim 3, characterized in that The specific temperature is 20-60℃.

5. The method according to claim 1, wherein The pretreatment in S1 is to carry out high temperature cooking, oil extraction, solid-liquid separation in sequence, and the anaerobic fermentation parameters are: pH value 8-10, temperature 35-40℃.

6. The method according to claim 1, characterized in that The delivery rate of the fermentation liquid to be concentrated in S2 is 375-625 mL / min, the delivery rate of the oleic acid-based DES liquid is 1-3 times that of the fermentation liquid to be concentrated, and the forward osmosis concentration temperature is 10-20°C.

7. A method for recycling a mixed solution of water and DES obtained by the method according to any one of claims 1 to 6, characterized in that: Follow these steps: The mixture of water and DES is connected to a temperature regulating box, and the solution is heated or cooled within a temperature range of 10-40°C to separate the water and DES, and the DES is then transported back to the hollow fiber permeation membrane for recycling.

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