Eutectic solvent composition for efficiently extracting phenolic compounds and preparation method of eutectic solvent composition

Abstract

The invention belongs to the technical field of environmental engineering and chemical separation, and particularly relates to a deep-eutectic solvent composition for efficiently extracting phenolic compounds and a preparation method of the deep-eutectic solvent composition. The deep-eutectic solvent composition for efficiently extracting the phenolic compounds, provided by the invention, consists of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of (1-2): (1-9), the hydrogen bond donor comprises n-caprylic acid or n-hexyl alcohol; the hydrogen bond receptor comprises 1-ethyl-3-methylimidazole chloride or tetrabutylammonium bromide. The eutectic solvent composition has the advantages of high partition coefficient, low viscosity, high selectivity, rapid phase separation, environmental friendliness and the like, can efficiently extract phenol, resorcinol, o-cresol, m-cresol and p-cresol, and has single-stage extraction efficiency gt; the regeneration rate is high, and the method is suitable for high-concentration phenolic wastewater, polyhydroxy phenolic wastewater, continuous process and low-toxicity emission requirement scenes.

Description

A eutectic solvent composition for efficient extraction of phenolic compounds and its preparation method Technical Field

[0001] This invention belongs to the fields of environmental engineering and chemical separation technology, and more specifically relates to a eutectic solvent composition for efficient extraction of phenolic compounds and its preparation method. Background Technology

[0002] Phenolic compounds are common organic pollutants in industrial wastewater (such as from coking, petrochemical, and pharmaceutical industries), exhibiting high toxicity, recalcitrant degradation, and bioaccumulation, posing a serious threat to the environment and human health. Traditional phenol extraction methods primarily utilize organic solvents (such as benzene and toluene), but these solvents suffer from high volatility, high toxicity, difficulty in recovery, and a tendency to cause secondary pollution. Deep eutectic solvents (DES), as a novel green solvent, are formed by hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) through hydrogen bonding, offering advantages such as low toxicity, biodegradability, ease of preparation, and low cost. However, existing DESs often suffer from drawbacks in phenol extraction, including low partition coefficients, high viscosity, poor selectivity, and slow phase separation, limiting their industrial application. Therefore, developing efficient, environmentally friendly, and renewable DESs for phenol extraction is of great significance. Summary of the Invention

[0003] The purpose of this invention is to provide a eutectic solvent composition for efficient extraction of phenolic compounds and a method for preparing the same. This composition is used for efficient extraction of phenolic compounds (including phenol, resorcinol, o-cresol, m-cresol, and p-cresol) to solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is to provide a eutectic solvent composition for efficient extraction of phenolic compounds, wherein the eutectic solvent composition is composed of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA); the hydrogen bond donor includes n-octanoic acid or n-hexanol; the hydrogen bond acceptor includes 1-ethyl-3-methylimidazole chloride (EMIMCl, hereinafter referred to as EMIM) or tetrabutylammonium bromide (TBAB); the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1-2:1-9.

[0005] Furthermore, when the hydrogen bond donor is octanoic acid, the hydrogen bond acceptor is 1-ethyl-3-methylimidazole chloride.

[0006] Furthermore, when the hydrogen bond donor is n-hexanol, the hydrogen bond acceptor is tetrabutylammonium bromide.

[0007] The second technical solution of the present invention provides a method for preparing the above-mentioned eutectic solvent composition for efficient extraction of phenolic compounds, comprising the steps of: mixing a hydrogen bond donor and a hydrogen bond acceptor, heating and stirring the mixture until a uniform and transparent liquid is formed, thereby obtaining the eutectic solvent composition.

[0008] Furthermore, the temperature of the heating and stirring reaction is 50-80℃.

[0009] The third technical solution of the present invention provides an application of the above-mentioned eutectic solvent composition for efficient extraction of phenolic compounds in the efficient extraction of phenolic compounds.

[0010] The fourth technical solution of the present invention provides an application of the above-mentioned eutectic solvent composition for efficient extraction of phenolic compounds in the treatment of wastewater containing phenolic compounds.

[0011] The present invention discloses the following technical effects: the DES composition provided by the present invention has the advantages of high partition coefficient, low viscosity, high selectivity, rapid phase separation, and environmental friendliness.

[0012] The DES prepared by this invention has advantages such as high partition coefficient, low viscosity, high selectivity, rapid phase separation, and environmental friendliness. It can efficiently extract phenol, resorcinol, o-cresol, m-cresol, and p-cresol, with a single-stage extraction efficiency of >85% and high regeneration rate. It is suitable for high-concentration phenol wastewater, polyhydroxyphenol wastewater, continuous processes, and low-toxicity emission requirements. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 is an infrared spectrum of the eutectic solvents prepared in Examples 1-2 and Comparative Examples 2-3.

[0014] Figure 2 shows the extraction efficiency of different DES systems.

[0015] Figure 3 shows the effect of extraction time on extraction efficiency.

[0016] Figure 4 shows the effect of temperature on extraction efficiency.

[0017] Figure 5 shows the effect of comparison on extraction rate and partition coefficient.

[0018] Figure 6 shows the effect of pH on extraction efficiency.

[0019] Figure 7 shows the effect of different molar ratios of hydrogen bond acceptor (EMIM) and hydrogen bond donor (octanoic acid) on phenol extraction in Examples 1 and 3.

[0020] Figure 8 shows the effect of different molar ratios of hydrogen bond acceptor (TBAB) and hydrogen bond donor (n-hexanol) on phenol extraction in Examples 2 and 4. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0027] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0028] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0029] In some specific embodiments, the present invention provides a method for preparing a eutectic solvent composition, comprising the steps of: mixing a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1-2:1-3, heating and stirring the mixture at 50-80°C until a homogeneous and transparent liquid is formed to obtain the eutectic solvent composition; wherein the hydrogen bond donor includes n-octanoic acid or n-hexanol; and the hydrogen bond acceptor includes 1-ethyl-3-methylimidazole chloride (EMIMCl, hereinafter referred to as EMIM) or tetrabutylammonium bromide (TBAB).

[0030] The DES prepared by this invention has advantages such as high partition coefficient, low viscosity, high selectivity, rapid phase separation, and environmental friendliness. It can efficiently extract phenol, resorcinol, o-cresol, m-cresol, and p-cresol, with a single-stage extraction efficiency of >85% and high regeneration rate. It is suitable for high-concentration phenol wastewater, polyhydroxyphenol wastewater, continuous processes, and low-toxicity emission requirements.

[0031] Example 1: A method for preparing a eutectic solvent composition, comprising the steps of: mixing a hydrogen bond acceptor (EMIM) and a hydrogen bond donor (octanoic acid) in a molar ratio of 2:1, 1:1, 1:2 or 1:3, and heating and stirring the mixture at 80°C until a homogeneous and transparent liquid is formed (approximately 30 min) to obtain the eutectic solvent composition.

[0032] Example 2: A method for preparing a eutectic solvent composition, comprising the steps of: mixing hydrogen bond acceptor (TBAB) and hydrogen bond donor (n-hexanol) in a molar ratio of 2:1, 1:1, 1:2 or 1:3, and heating and stirring at 80°C until a homogeneous and transparent liquid is formed (about 25 min) to obtain a eutectic solvent composition.

[0033] The only difference between Example 3 and Example 1 is that the molar ratio of the hydrogen bond acceptor (EMIM) and the hydrogen bond donor (octanoic acid) is 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9.

[0034] The only difference between Example 4 and Example 2 is that the molar ratio of the hydrogen bond acceptor (TBAB) and the hydrogen bond donor (n-hexanol) is 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9.

[0035] The preparation method of the eutectic solvent composition of Comparative Example 1 includes the following steps: mixing hydrogen bond acceptor (ChCl) and hydrogen bond donor (1,6-hexanediol) in a molar ratio of 2:1, 1:1, 1:2 or 1:3, heating and stirring at 80°C until a homogeneous and transparent liquid is formed (about 20 min) to obtain the eutectic solvent composition.

[0036] The preparation method of the eutectic solvent composition of Comparative Example 2 includes the following steps: mixing hydrogen bond acceptor (ChCl) and hydrogen bond donor (1,8-octanediol) in a molar ratio of 2:1, 1:1, 1:2 or 1:3, heating and stirring at 80°C until a homogeneous and transparent liquid is formed (about 20 min) to obtain the eutectic solvent composition.

[0037] The preparation method of the eutectic solvent composition of Comparative Example 3 includes the following steps: mixing hydrogen bond acceptor (TMAC) and hydrogen bond donor (n-octanol) in a molar ratio of 2:1, 1:1, 1:2 or 1:3, heating and stirring at 80°C until a homogeneous and transparent liquid is formed (about 30 min) to obtain the eutectic solvent composition.

[0038] The eutectic solvent compositions prepared in Experimental Examples 1-2 and Comparative Examples 1-3 are numbered as shown in Table 1.

[0039] Table 1 The physical state and stability of the eutectic solvents prepared in Examples 1-2 and Comparative Examples 1-3 are shown in Table 2.

[0040] Table 2 Observation and analysis of the eutectic solvents (DES) prepared in Examples 1-2 and Comparative Examples 1-3 revealed that Group A (octanoic acid / EMIM) exhibited excellent phase-forming ability. Except for A21, where the excess HBA (EMIM) exceeded its solubility in octanoic acid, leading to crystal precipitation, the other proportions formed homogeneous, transparent, and stable liquids. This indicates that EMIM and octanoic acid can form stable eutectic mixtures over a wide range of proportions, and their strong hydrogen bonding network overcomes the lattice energy of their respective components.

[0041] All formulations in Group B (1,6-hexanediol / ChCl) formed a homogeneous phase. Although a homogeneous liquid was formed, the DES obtained was completely miscible with water because both HBA (ChCl) and HBD are strongly hydrophilic substances, and thus could not form a two-phase system.

[0042] The synthesized products of group C (1,8-octanediol / ChCl) exhibit high viscosity, even being semi-solid at room temperature (e.g., C21). This is attributed to the strong intramolecular and intermolecular hydrogen bonding crosslinks between the diol molecules, resulting in extremely poor flowability and hindering mass transfer.

[0043] Group D (n-hexanol / TBAB) exhibited the best phase-forming ability and flowability. The long-chain alkyl group of TBAB and the nonpolar segments of n-hexanol endowed the system with excellent hydrophobicity and low viscosity, making it an ideal candidate for extractant.

[0044] The phase formation of group E (n-octanol / TMAC) was not ideal. All ratios formed a homogeneous phase upon heating, but HBA (TMAC) crystals precipitated to varying degrees upon cooling. This is because TMAC has high symmetry and large lattice energy, and the hydrogen bonding energy provided by the hydroxyl group of n-octanol is insufficient to destroy the lattice structure of TMAC in a large proportion.

[0045] Figure 1 shows the infrared spectra of the eutectic solvents prepared in Examples 1-2 and Comparative Examples 2-3. As can be seen from the figure, all prepared DES systems exhibited infrared spectra in the range of 3600-2400 cm⁻¹. -1 The high wavenumber region (shown by the orange dashed box in the figure) exhibits highly common spectral changes. The sharp stretching vibration peak originally attributed to the free hydroxyl group (-OH) in the hydrogen bond donor (HBD) undergoes dramatic broadening and a significant red shift in this region, forming a very broad envelope peak. This significant change in peak shape is attributed to the interaction between the hydroxyl proton in the HBD molecule and the halide anion (Cl-) in the quaternary ammonium salt. - or Br - A strong hydrogen bond interaction forms between HBD and HBA. From a molecular dynamics perspective, this strong interaction leads to a decrease in the force constant and vibrational frequency of the OH bond. Simultaneously, due to the randomness of molecular orientation and the dynamic non-uniformity of the microenvironment in the liquid DES system, the bond lengths and bond angles of the hydrogen bonds exhibit diverse distributions, resulting in a significant broadening of the absorption band in the macroscopic spectrum. This phenomenon strongly confirms that a broad and stable supramolecular hydrogen bond network has been established between HBD and HBA, effectively overcoming the lattice energy of the original components, and is the structural basis for the homogeneous and stable liquid state of DES at room temperature.

[0046] Based on the confirmation of hydrogen bond formation, further comparative analysis of the fingerprint region characteristics of the four sets of spectra clearly reveals the influence of different HBD structures on the intermolecular interaction modes of DES. Spectra A, D, and E show a high degree of structural similarity; apart from the aforementioned broad OH peak, all are located at approximately 1710 cm⁻¹. -1 A strong characteristic absorption peak was observed at 1700 cm⁻¹, attributed to the stretching vibration of the carbonyl group (C=O) in the carboxylic acid group. The persistent presence of this peak and its slight shift relative to the pure component corroborate that the carboxyl group acts as a hydrogen bond donor core involved in the complexation process, and indicates that these three DES groups share a similar acid-dominated hydrogen bond association mechanism. In stark contrast, the C group spectrum shows a weak absorption peak at 1700 cm⁻¹. -1 No carbonyl absorption peak was observed nearby, which is consistent with the molecular structure characteristics of this component using alcohol HBD; meanwhile, the OH broad peak in group C is relatively flatter and superimposed on the 2850–2950 cm⁻¹ peak. -1The CH stretching vibration peaks at the hydroxyl groups are more prominent, suggesting that the hydrogen bond network constructed by the hydroxyl groups differs from that of the carboxylic acid system in terms of intensity or spatial configuration. Furthermore, the spectra of samples with different molar ratios within each group maintain extremely high consistency in peak shape, position, and relative intensity, without any unexpected impurity peaks or splitting. This not only rules out the occurrence of chemical side reactions but also indicates that the main physical interaction mechanism within the DES system has good chemical stability within the studied ratio range. In summary, FT-IR spectroscopy analysis confirms the successful preparation of four DES groups (A, C, D, and E) at the molecular level, clarifies the dominant role of hydrogen bonding, and provides a solid structural basis for subsequent interpretation of their macroscopic physical properties and extraction behavior.

[0047] To evaluate the extraction potential of different DES systems (Examples 1-2 and Comparative Examples 2-3), four representative DESs were selected, and extraction experiments were conducted on five phenolic compounds (phenol, resorcinol, o-cresol, m-cresol, and p-cresol) at different molar ratios. The experimental results are shown in Figure 2. The steps are as follows: 2 mL of the DES organic phase was placed in a 15 mL stoppered glass centrifuge tube and preheated in an 80°C water bath for 10 minutes to reduce the viscous resistance of the high-viscosity DES and create favorable conditions for the subsequent mass transfer process; 8 mL of phenolic standard solution (100 mg / L) was added to the preheated DES.

[0048] Place the centrifuge tubes in a constant temperature water bath shaker and shake at 200 rpm for 15 minutes at 30°C. After the extraction is complete, keep the temperature constant and let it stand for at least 12 hours.

[0049] After complete separation, a precision syringe with a long needle is used to carefully aspirate the lower aqueous phase and the upper organic phase separately for subsequent concentration analysis.

[0050] Each experiment was repeated at least three times, and the average of the experimental results was taken as the final result to avoid random errors.

[0051] Figure 2 shows the extraction efficiency of different DES systems. As shown in the figure, in all DES systems capable of forming a stable liquid phase, the extraction efficiency (E) of the target phenolic compound increases significantly as the molar ratio of HBD in the DES components increases from 2:1 to 1:3. Taking the EMIM·n-octanoic acid system for extracting phenol as an example, the extraction rate is 89.06% when the molar ratio is 2:1; however, when the HBD ratio is adjusted to 1:3, the extraction rate increases to 97.50%. Similarly, the TBAB·n-hexanol system achieves a high extraction rate of 99.49% for phenol at a 1:3 ratio. Thermodynamically, this positive correlation effect is mainly attributed to the enhanced hydrophobicity of the system. The selected HBDs (n-octanoic acid, n-hexanol, and n-octanol) are all hydrophobic molecules with long alkyl chains. As the HBD ratio increases, the overall polarity of the DES decreases, and the hydrophobicity significantly increases. According to the principle of "like dissolves like," this is more conducive to the transfer of hydrophobic phenolic molecules from the aqueous phase to the DES phase. In addition, the excess HBD, as a co-solvent, provides more active hydrogen bond sites, which can form a tighter hydrogen bond network with phenolic hydroxyl groups, thereby significantly improving the solute loading capacity of DES.

[0052] The differences in component structure among different DES systems directly determine their extraction capabilities. Comparing four representative DES systems, their extraction capabilities follow this order: TBAB·n-hexanol ≈ EMIM·n-octanoic acid > TMAC·n-octanol >> ChCl·1,8-octanediol. Among them, TBAB·n-hexanol and EMIM·n-octanoic acid exhibit the best performance, especially TBAB·n-hexanol, which achieves extraction rates of almost 99% or higher for all five phenols at a 1:3 ratio. This is mainly due to the highly hydrophobic microenvironment constructed by the four butyl chains in TBAB and the hexyl chains in n-hexanol, as well as the strong π-π interactions between the quaternary ammonium salt cation and the benzene ring. In contrast, the ChCl·1,8-octanediol system performs the worst, with a partition coefficient of only 0.49 for phenol at a 2:1 ratio, indicating that phenol tends to remain in the aqueous phase at this ratio. This is because HBA (choline chloride) has extremely high hydrophilicity, and HBD (1,8-octanediol) contains two hydroxyl groups, resulting in a high overall hydrophilicity and excessive viscosity of the DES, which hinders the mass transfer process. Furthermore, although the TMAC·n-octanol system (Group E) has a acceptable extraction rate, its tendency to crystallize at room temperature limits its potential for practical industrial applications.

[0053] The DES system of D13 was used to extract phenol and m-diphenol. The effects of extraction time, temperature, phase ratio and pH on the extraction system were investigated. Specifically, the change in extraction rate within 5-30 min was investigated at 303.15 K, as shown in Figure 3.

[0054] Figure 3 shows the effect of extraction time on extraction efficiency. As can be seen from the figure, the removal rates of both phenol and resorcinol initially increased rapidly over time and then stabilized. Phenol, due to its stronger hydrophobicity, achieved a removal rate of >99% within 15 minutes and extracted faster. Resorcinol, containing two phenolic hydroxyl groups and exhibiting stronger hydrophilicity, had a lower extraction rate and a lower final removal rate (96.42% at 30 min). This is because its hydrogen bond network in water is more stable, resulting in a higher desolvation energy barrier. When the extraction time reached 15 min, phenol had essentially reached extraction equilibrium, and resorcinol also achieved a removal rate exceeding 95%. Further extending the extraction time had limited effect on improving the removal rates of both. Therefore, 15 min was consistently selected as the extraction time in subsequent experiments to ensure high extraction efficiency while also considering the time economy and repeatability of the experimental process.

[0055] The change in extraction rate under the conditions of 298.15 K-328.15 K was investigated during an extraction time of 15 min, as shown in Figure 4.

[0056] Figure 4 shows the effect of temperature on extraction efficiency. As can be seen from the figure, under constant conditions, the removal rates of both phenols monotonically decrease with increasing temperature (phenol from 99.37% at 298.15 K to 83.12% at 328.15 K, and resorcinol from 97.76% to 79.38%), with the removal rate of phenol consistently higher than that of resorcinol. This phenomenon indicates that the extraction process is thermodynamically more favorable at lower temperatures, because increasing temperature weakens the hydrogen bonding / complexation between the solute and the deep eutectic solvent, leading to a decrease in the partition coefficient. This negative impact outweighs the potential positive effect of increasing temperature on mass transfer. Based on efficiency and economy, 298.15 K (room temperature) was determined to be the optimal operating temperature for this system.

[0057] To investigate the limiting loading capacity and phase equilibrium behavior of the TBAB / n-hexanol eutectic solvent system in treating high-concentration phenol-containing wastewater, with an extraction time of 15 min and a temperature of 298.15 K, the initial solute concentration in the simulated wastewater was increased to 10000 mg / L, and the changes in extraction performance when the ratio (O / A) was gradually reduced from 1:1 to 1:10 were examined, as shown in Figure 5.

[0058] Figure 5 shows the effect of the ratio on the extraction rate and partition coefficient. As can be seen from the figure, the extraction efficiency of both phenols decreases with decreasing organic phase ratio, but phenol shows stronger tolerance (maintaining >95% at a 1:6 ratio, decreasing to 80.8% at 1:10), while resorcinol shows a more significant decrease (only 65.2% at 1:10). This is attributed to the gradual saturation of DES active sites under high loading, and the fact that resorcinol, due to its bisphenol hydroxyl groups and stronger hydrophilicity, has a higher desolvation energy barrier and is more easily retained in the aqueous phase at low ratios. Although the single-stage efficiency decreases at extreme ratios, this DES can achieve solute enrichment of up to 65-80 g / L in the organic phase at 1:10, showing good high loading potential. In practical engineering, multi-stage extraction can further optimize the overall phenol removal and resource recovery effect.

[0059] pH is one of the key parameters affecting the extraction mechanism of phenols. The pH of the aqueous phase was adjusted between 2.0 and 12.0 to investigate the effect of pH on the extraction rate and partition coefficient. The results are shown in Figure 6.

[0060] Figure 6 shows the effect of pH on extraction efficiency. As can be seen from the figure, both exhibit a single-peak trend of "increasing at low pH, plateauing in the neutral region, and sharply decreasing at high pH": in the neutral range of pH 6-9 (phenol) and 6-8 (resorcinol), the extraction efficiency remains stable above 95%; however, under strongly alkaline conditions (pH > 10), the efficiency drops sharply. This is mainly because phenols exist in a hydrophobic neutral molecular form under neutral conditions, easily entering the extraction phase and being captured through hydrogen bonding; when the pH rises to near its pKa, the phenolic hydroxyl groups deprotonate to form hydrophilic phenolate ions, causing them to be strongly retained in the aqueous phase, leading to a sharp drop in extraction rate. Among these, resorcinol, containing dihydroxyl groups, shows a more significant decrease in efficiency near pH=9, indicating that it is more susceptible to alkaline environments. In summary, to ensure that both solutes are within the efficient and stable range, the optimal extraction pH for the system was ultimately determined to be 7.0.

[0061] The effects of different molar ratios of hydrogen bond acceptor (EMIM) and hydrogen bond donor (octanoic acid) on phenol extraction in Examples 1 and 3 were investigated. The steps were as follows: 2 mL of DES organic phase was placed in a 15 mL stoppered glass centrifuge tube and preheated in an 80 °C water bath for 10 minutes to reduce the viscous resistance of the high-viscosity DES and create favorable conditions for the subsequent mass transfer process; 8 mL of phenol standard solution (100 mg / L) was added to the preheated DES.

[0062] Place the centrifuge tubes in a constant temperature water bath shaker and shake at 200 rpm for 15 minutes at 30°C. After the extraction is complete, keep the temperature constant and let it stand for at least 12 hours.

[0063] After complete separation, a precision syringe with a long needle is used to carefully aspirate the lower aqueous phase and the upper organic phase separately for subsequent concentration analysis.

[0064] Each experiment was repeated at least three times, and the average of the experimental results was taken as the final result to avoid random errors.

[0065] Figure 7 shows the effect of different molar ratios of hydrogen bond acceptor (EMIM) and hydrogen bond donor (octanoic acid) on phenol extraction in Examples 1 and 3. As can be seen from the figure, the EDS systems at different molar ratios all exhibit high extraction rates for phenol.

[0066] The effects of different molar ratios of hydrogen bond acceptor (TBAB) and hydrogen bond donor (n-hexanol) on resorcinol extraction in Examples 2 and 4 were investigated. The steps were as follows: 2 mL of DES organic phase was placed in a 15 mL stoppered glass centrifuge tube and preheated in an 80°C water bath for 10 minutes to reduce the viscous resistance of the high-viscosity DES and create favorable conditions for the subsequent mass transfer process; 8 mL of resorcinol standard solution (100 mg / L) was added to the preheated DES.

[0067] Place the centrifuge tubes in a constant temperature water bath shaker and shake at 200 rpm for 15 minutes at 30°C. After the extraction is complete, keep the temperature constant and let it stand for at least 12 hours.

[0068] After complete separation, a precision syringe with a long needle is used to carefully aspirate the lower aqueous phase and the upper organic phase separately for subsequent concentration analysis.

[0069] Each experiment was repeated at least three times, and the average of the experimental results was taken as the final result to avoid random errors.

[0070] Figure 8 shows the effect of different molar ratios of hydrogen bond acceptor (TBAB) and hydrogen bond donor (n-hexanol) on phenol extraction in Examples 2 and 4. As can be seen from the figure, the EDS systems at different molar ratios all exhibit high extraction rates for resorcinol.

[0071] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0072] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A eutectic solvent composition for efficient extraction of phenolic compounds, characterized in that, The eutectic solvent composition comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor includes n-octanoic acid or n-hexanol; the hydrogen bond acceptor includes 1-ethyl-3-methylimidazolium chloride or tetrabutylammonium bromide; the molar ratio of the hydrogen bond donor and the hydrogen bond acceptor is 1-2:1-9.

2. The eutectic solvent composition according to claim 1, characterized in that, When the hydrogen bond donor is octanoic acid, the hydrogen bond acceptor is 1-ethyl-3-methylimidazole chloride.

3. The eutectic solvent composition as described in claim 1, characterized in that, When the hydrogen bond donor is n-hexanol, the hydrogen bond acceptor is tetrabutylammonium bromide.

4. A method for preparing a eutectic solvent composition for efficient extraction of phenolic compounds according to any one of claims 1-3, characterized in that the step... include: The hydrogen bond donor and hydrogen bond acceptor are mixed and heated and stirred until a homogeneous and transparent liquid is formed, thus obtaining the eutectic solvent composition.

5. The preparation method according to claim 4, characterized in that, The temperature for the heating and stirring reaction is 50-80℃.

6. The use of the eutectic solvent composition according to any one of claims 1-3 for the efficient extraction of phenolic compounds in the efficient extraction of phenolic compounds.

7. The use of the eutectic solvent composition for efficient extraction of phenolic compounds as described in any one of claims 1-3 in the treatment of wastewater containing phenolic compounds.

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