A method for recovering organic matter from phenolic wastewater using cold energy

Abstract

This invention relates to a method for recovering organic matter from phenolic wastewater using cold energy, belonging to the field of wastewater treatment. It addresses the problems of complex processes, high energy consumption, and difficulties in solid-liquid separation and product recovery associated with existing oxidative polymerization processes for phenolic wastewater. The invention adjusts the phenolic wastewater to alkaline conditions and adds persulfate as an oxidant. Cold energy is then used to freeze the wastewater. The freeze-concentration effect creates a localized high-concentration reaction microenvironment at the interface between the unfrozen liquid phase and ice crystals. Under the action of ice crystals removing salt and solute, phenolic organic matter, alkali, and persulfate accumulate in the crystal boundary liquid layer, inducing oxidative coupling of phenolic oxygen free radicals to generate sedimentable or filterable macromolecular oligomers or polymers. Subsequently, solid-liquid separation, washing, and drying yield the recovered organic matter product, or it can be eluted with an organic solvent. This invention significantly reduces energy consumption in the resource recovery process of phenolic wastewater, with high reagent utilization and convenient recovery.

Description

Technical Field

[0001] This invention relates to a method for recovering organic matter from phenolic wastewater using cold energy, belonging to the field of wastewater treatment. Background Technology

[0002] Phenolic wastewater is widely produced in industries such as coking, coal chemical, petrochemical, epoxy resin, phenolic resin, bisphenol chemical, pharmaceutical and pesticide production. This type of wastewater is usually characterized by high toxicity, poor biodegradability, complex composition and large salinity fluctuations. If it is discharged directly without effective treatment, it can easily pose a continuous risk to the aquatic ecosystem and human health.

[0003] Currently, phenolic wastewater treatment technologies mainly include adsorption, extraction, membrane separation, biological treatment, and advanced oxidation. Among these, adsorption and membrane separation primarily remove pollutants by trapping or transferring them, but subsequent regeneration of the adsorbent, disposal of the concentrate, or membrane fouling control are still required. Biological treatment has limited adaptability to highly toxic, high-salinity, and fluctuating phenolic wastewater. While advanced oxidation can remove phenolic pollutants relatively quickly, it typically focuses on pollutant degradation and even mineralization, requiring significant amounts of reagents and energy, easily leading to organic matter loss, hindering resource utilization, and failing to meet the requirements of "pollution reduction and carbon reduction, synergistic efficiency improvement."

[0004] Previous studies have shown that phenolic organic compounds can undergo polymerization under oxidative conditions to generate relatively high molecular weight products, thus providing a new approach for the recovery of organic resources from phenolic wastewater. However, existing oxidative polymerization technologies still have the following shortcomings: First, the preparation process of some carbon-based or metal-based catalysts is relatively complex and energy-intensive; second, homogeneous reaction wastewater usually carries the risk of metal ion leaching and has high requirements for reaction conditions; third, the products often contain a large number of soluble oligomers, making solid-liquid separation and product recovery difficult. Summary of the Invention

[0005] In order to solve the problems of complex process, high energy consumption, and difficulty in solid-liquid separation and product recovery in the existing oxidative polymerization process of phenolic wastewater, this invention proposes a method for recovering organic matter from phenolic wastewater using cold energy.

[0006] The present invention utilizes cold energy to recover organic matter from phenolic wastewater, and the method is carried out according to the following steps:

[0007] 1. Removal of suspended particles from phenolic wastewater;

[0008] 2. Add an alkaline conditioner to the wastewater obtained in step 1;

[0009] 3. Add persulfate to the wastewater obtained in step 2 and mix well;

[0010] The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 2~20:1; the molar ratio of persulfate to alkaline regulator is 1:2~4;

[0011] Fourth, use a cold source to cool the wastewater obtained in step three to -10~-25℃ to achieve a frozen state, and maintain this state for 2~6 hours; so that the volume fraction of the ice phase in the wastewater reaches 70%~95%.

[0012] 5. After step four is completed, raise the temperature of the frozen wastewater to 0~25℃ and maintain it for 0.5~3 hours;

[0013] For wastewater containing bisphenol organic compounds, the pH of the wastewater is adjusted to 4-7 to reduce the degree of ionization of the polymerization products, increase the hydrophobicity of the bisphenol organic compounds and promote precipitation, and then solid-liquid separation is performed; for wastewater containing phenol or chlorophenol organic compounds, an adsorbent is used to adsorb the organic compounds in the wastewater, and then the adsorbent is eluted.

[0014] The principle and beneficial effects of this invention are as follows:

[0015] 1. This invention adjusts phenol-containing wastewater to alkaline and adds persulfate as an oxidant; then, it uses cold energy to freeze the wastewater; utilizing the freeze-concentration effect, a local high-concentration reaction microenvironment is constructed at the interface between the unfrozen liquid phase and ice crystals. Under the action of ice crystals removing salt and solute, phenolic organic matter, alkali, and persulfate are enriched in the crystal boundary liquid layer, inducing oxidative coupling of phenolic oxygen free radicals to generate large molecular oligomers or polymers that can be settled or filtered. Subsequently, the organic matter is recovered by solid-liquid separation, washing, and drying, or by eluting with organic solvents to obtain the organic matter recovered product.

[0016] 2. This invention can treat wastewater containing one or more inorganic salt ions, including Cl-. - SO4 2- NO3 - CO3 2- etc. Cl in wastewater - The concentration range is 0.1~10 mmol / L; SO4 in wastewater 2- NO3 - CO3 2- The concentration range is 1~50 mmol / L.

[0017] 3. The cold sources selectable in this invention include LNG vaporization cooling energy, waste cooling from refrigeration units, cold storage recirculation refrigerant, liquid nitrogen, liquefied air cooling energy, low-temperature brine refrigerant, and natural low-temperature environments as key driving conditions. It requires no high-temperature heating conditions and no introduction of metal catalysts or complex carbon-based catalytic materials, significantly reducing energy consumption in the phenolic wastewater resource recovery process. The reagent utilization rate is high, and recovery is convenient. It can be directly coupled with existing LNG vaporization heat exchange devices, refrigeration brine systems, or open-air cold sources in cold regions, demonstrating good potential for engineering scale-up.

[0018] 4. The products obtained by this invention exist in the form of oligomers or polymers, which are easily separated into solid and liquid phases through sedimentation, adsorption, or filtration, thus reducing the load on subsequent processing. The organic matter recovery products are phenolic oligomers or polymers, which can be used as resin precursors, carbon material precursors, adsorbent material precursors, or fuel feedstocks. Attached Figure Description

[0019] Figure 1 These are photographs of the wastewater after settling in Example 1 and Comparative Example 1.

[0020] Figure 2 This is a liquid chromatography-mass spectrum of the wastewater from Example 1 after it was heated to room temperature;

[0021] Figure 3 The TGA / DTG curve of the organic matter recovery product obtained in Example 1 is shown below.

[0022] Figure 4 Gel permeation chromatography of the organic matter recovery product obtained in Example 1;

[0023] Figure 5 The Fourier transform infrared spectrum of the organic matter recovery product obtained in Example 1;

[0024] Figure 6 A photomicrograph of the frozen ice crystals formed by the freezing of wastewater in Example 1;

[0025] Figure 7 The image shows the confocal Raman spectrum of the frozen ice crystals formed by the freezing of wastewater in Example 1.

[0026] Figure 8 This is a comparison chart of the bisphenol A removal rates of Example 1 and Comparative Examples 1-4;

[0027] Figure 9 A comparison chart of bisphenol A removal rates at different freezing temperatures;

[0028] Figure 10 A comparison chart of bisphenol A removal rates with different amounts of sodium persulfate added;

[0029] Figure 11A comparison chart of bisphenol A removal rates under different initial BPA concentrations;

[0030] Figure 12 A comparison chart of bisphenol A removal rates with different molar ratios of sodium persulfate to sodium hydroxide;

[0031] Figure 13 A comparison chart showing the COD removal rate of wastewater before and after filtration and sedimentation.

[0032] Figure 14 The graph shows the TOC removal rate of wastewater under different NaOH addition conditions. Detailed Implementation

[0033] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0034] Specific Implementation Method 1: This implementation method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0035] 1. Removal of suspended particles from phenolic wastewater;

[0036] 2. Add an alkaline conditioner to the wastewater obtained in step 1;

[0037] 3. Add persulfate to the wastewater obtained in step 2 and mix well;

[0038] The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 2~20:1; the molar ratio of persulfate to alkaline regulator is 1:2~4;

[0039] Fourth, use a cold source to cool the wastewater obtained in step three to -10~-25℃ to achieve a frozen state, and maintain this state for 2~6 hours; so that the volume fraction of the ice phase in the wastewater reaches 70%~95%.

[0040] 5. After step four is completed, raise the temperature of the frozen wastewater to 0~25℃ and maintain it for 0.5~3 hours;

[0041] For wastewater containing bisphenol organic compounds, the pH of the wastewater is adjusted to 4-7 to reduce the degree of ionization of the polymerization products, increase the hydrophobicity of the bisphenol organic compounds and promote precipitation, and then solid-liquid separation is performed; for wastewater containing phenol or chlorophenol organic compounds, an adsorbent is used to adsorb the organic compounds in the wastewater, and then the adsorbent is eluted.

[0042] This embodiment has the following beneficial effects:

[0043] 1. In this embodiment, the phenol-containing wastewater is adjusted to alkaline, and persulfate is added as an oxidant. Then, cold energy is used to freeze the wastewater. The freeze-concentration effect is used to create a local high-concentration reaction microenvironment at the interface between the unfrozen liquid phase and the ice crystals. Under the action of ice crystals removing salt and solute, phenolic organic matter, alkali and persulfate are enriched in the crystal boundary liquid layer, inducing oxidative coupling of phenolic oxygen free radicals to generate large molecular oligomers or polymers that can be settled or filtered. Subsequently, the organic matter is recovered by solid-liquid separation, washing and drying, or by eluting with organic solvents to obtain the organic matter recovered product.

[0044] 2. This embodiment can treat wastewater containing one or more inorganic salt ions, including Cl-. - SO4 2- NO3 - CO3 2- etc. Cl in wastewater - The concentration range is 0.1~10 mmol / L; SO4 in wastewater 2- NO3 - CO3 2- The concentration range is 1~50 mmol / L.

[0045] 3. This implementation method can utilize LNG vaporization cooling energy, waste cooling from refrigeration units, cold storage recirculation refrigerant, liquid nitrogen, liquefied air cooling energy, low-temperature brine refrigerant, and natural low-temperature environments as key driving conditions. It eliminates the need for high-temperature heating and the introduction of metal catalysts or complex carbon-based catalytic materials, significantly reducing energy consumption in the phenolic wastewater resource recovery process. It also boasts high reagent utilization and convenient recovery. It can be directly coupled with existing LNG vaporization heat exchange devices, refrigeration brine systems, or open-air cold sources in cold regions, demonstrating significant potential for engineering scale-up.

[0046] 4. The product obtained in this embodiment exists in the form of oligomers or polymers, which are easily separated into solid and liquid phases through sedimentation, adsorption, or filtration, thus reducing the load on subsequent processing. The organic matter recovery product is a phenolic oligomer or polymer that can be used as a resin precursor, carbon material precursor, adsorbent material precursor, or fuel feedstock.

[0047] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the alkaline regulator mentioned in step one is one or a combination of two of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water.

[0048] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the persulfate mentioned in step 3 is one or a combination of two of sodium persulfate and potassium persulfate.

[0049] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that the bisphenol organic compound mentioned in step five is bisphenol A, bisphenol F or bisphenol S.

[0050] Specific Implementation Method Five: This implementation method differs from one of the specific implementation methods one to four in that the phenolic or chlorophenolic organic compounds mentioned in step five are phenol, chlorophenol, dichlorophenol, cresol, or alkylphenol.

[0051] Specific Implementation Method Six: This implementation method differs from one of Specific Implementation Methods One to Five in that the adsorbent in step five is activated carbon.

[0052] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the solid-liquid separation process described in step five is static sedimentation, centrifugal separation, filtration, or membrane separation.

[0053] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the filter membrane used for filtration has a pore size of 0.22~5μm.

[0054] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Seven in that the centrifugal separation speed is 4000~12000 r / min and the time is 5~30 min.

[0055] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the amount of adsorbent added in step 5 is 0.1~2.0g / L.

[0056] Example 1

[0057] This embodiment of the method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0058] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a bisphenol A (BPA) concentration of 0.05mmol / L and a volume of 1000 mL.

[0059] 2. Add sodium hydroxide to the wastewater obtained in step 1;

[0060] 3. Add sodium persulfate (PDS) to the wastewater obtained in step 2 and mix well;

[0061] The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 10:1; the molar ratio of persulfate to sodium hydroxide is 1:4.

[0062] Fourth, the wastewater obtained in step three is cooled to -20℃ to achieve a frozen state using a cold source and maintained for 3 hours; liquid nitrogen is used as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater, which is carried out in a jacketed reactor, with liquid nitrogen introduced into the jacket.

[0063] 5. After step four, the frozen wastewater was heated to room temperature and maintained for 1 hour. The high-performance liquid chromatography (HPLC) chromatogram of the wastewater after the frozen wastewater was heated to room temperature showed that the bisphenol A removal rate was 99%. Then, sulfuric acid was added to adjust the pH of the wastewater containing bisphenol organic matter to 5, and the mixture was allowed to stand for 5 hours to settle. The precipitate was then filtered and collected. The TOC removal rate was measured to be 93.6%.

[0064] The obtained solid product was washed with deionized water and then dried to obtain a yellowish-brown organic matter recovery product. The mass of the solid product obtained after separation, washing and freeze-drying was 8.3 mg.

[0065] Figure 1 The images show the wastewater after settling in Example 1 and Comparative Example 1. This illustrates that, compared to conditions without cold energy, Example 1 formed more obvious precipitate after settling. The cold energy-induced freeze-concentration process is beneficial for the aggregation, precipitation, separation, and recovery of bisphenol A reaction products.

[0066] Figure 2 The liquid chromatography-mass spectra of the wastewater from Example 1 after it was heated to room temperature show polymer characteristic peaks with m / z values ​​of 453.2, 679.3, 905.4, and 1131.5. Multiple characteristic peaks higher than the molecular weight of bisphenol A monomer were detected in the system after the reaction in Example 1, indicating that bisphenol A underwent oxidative coupling in a cold-coupled alkaline persulfate system, generating a polymer product.

[0067] Figure 3 The TGA / DTG curve of the organic matter recovery product obtained in Example 1 is shown. The results show that the product has major thermal decomposition peaks at 217℃ and 377℃, and still retains about 27% of the residual mass at 800℃, indicating that the obtained product has high thermal stability and condensation aggregation characteristics. Figure 4 Gel permeation chromatography of the organic matter recovery product obtained in Example 1; the results showed that the Mn, Mw, Mz and Mp of the recovered product were 2524 Da, 3060 Da, 3916 Da and 2565 Da, respectively, and the PDI was 1.21, indicating that the product was mainly composed of oligomers / polymers with a narrow molecular weight distribution. Figure 5 The Fourier transform infrared spectrum of the organic matter recovery product obtained in Example 1 is shown below; the results show that the product is at 3419 cm⁻¹ -1 It has an OH absorption peak at 1611 cm⁻¹. -1 1509 cm -1 and 1446 cm -1 It exhibits aromatic ring skeletal vibration characteristics at 1226 cm. -1 and 1180 cm -1The presence of a COC absorption peak indicates that the product retains the bisphenol A-derived aromatic structure and ether bond structure.

[0068] Figure 6 This is a photomicrograph of the frozen ice crystals formed by the freezing of wastewater in Example 1. Figure 7 The image shows the confocal Raman spectrum of the frozen ice crystals formed by the freezing of wastewater in Example 1. Figure 6 This indicates that after the wastewater freezes, it forms a distinct ice crystal structure. There are intercrystalline regions or unfrozen liquid phase channels between the ice crystals. During the freezing process, the solute is repelled and enriched in the unfrozen liquid phase region at the ice crystal interface, thus providing a local high-concentration microenvironment for the subsequent oxidative coupling reaction. Figure 7 The results show a significant difference in Raman signals between the ice crystal region and the ice crystal liquid layer region in the freezing system. The characteristic signals related to the solute are more pronounced in the ice crystal liquid layer region, indicating that bisphenol A and persulfate underwent interfacial enrichment during the freezing process. Both findings demonstrate that the cold energy conditions in this invention not only provide a low-temperature environment but also enrich bisphenol A, persulfate, and alkaline components in local micro-regions through freezing concentration, thereby promoting the oxidative coupling and polymerization transformation of bisphenol A and creating conditions for the subsequent precipitation and recovery of organic matter.

[0069] Example 2

[0070] This embodiment of the method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0071] I. Suspended particles in phenolic wastewater were removed by filtration using a 0.45 μm filter membrane. The phenolic wastewater was a simulated wastewater with a bisphenol A (BPA) concentration of 0.05 mmol / L and a volume of 1000 mL. Four sets of simulated wastewater were prepared, with the following anions: Cl... - SO4 2- NO3 - CO3 2- The anion concentrations were all 20 mmol / L.

[0072] 2. Add sodium hydroxide to the wastewater obtained in step 1;

[0073] 3. Add sodium persulfate (PDS) to the wastewater obtained in step 2 and mix well;

[0074] The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 10:1;

[0075] Fourth, the wastewater obtained in step three is cooled to -20℃ to achieve a frozen state using a cold source and maintained for 3 hours; liquid nitrogen is used as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater, which is carried out in a jacketed reactor, with liquid nitrogen introduced into the jacket.

[0076] 5. After step 4 is completed, the frozen wastewater is heated to room temperature and kept there for 1 hour. HPLC analysis of the wastewater showed that the removal rate of bisphenol A was 99%. Then, sulfuric acid was added to adjust the pH of the wastewater containing bisphenol organic matter to 5, and the mixture was allowed to stand for 5 hours to settle. The precipitate was then filtered and collected. The removal rate of TOC was measured to be 90%. The obtained solid product was washed with deionized water and dried to obtain a yellowish-brown organic matter recovery product.

[0077] The mass of the yellowish-brown organic matter recovered in this example was 8.0 mg. This indicates that in Cl... - SO4 2- NO3 - CO3 2- Under coexisting conditions, separable solid products can be formed in both systems. Even under different inorganic salt ion coexistence environments, the cold-coupled alkaline persulfate system can still promote the conversion of bisphenol A from a dissolved state to separable and recyclable oligomers or polymers, indicating that this invention has good applicability to practical phenolic wastewater containing salts.

[0078] Example 3

[0079] This embodiment of the method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0080] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a phenol concentration of 0.05mmol / L and a volume of 1000 mL.

[0081] 2. Add sodium hydroxide to the wastewater obtained in step 1;

[0082] 3. Add sodium persulfate (PDS) to the wastewater obtained in step 2 and mix thoroughly; the molar ratio of persulfate to sodium hydroxide is 1:4;

[0083] The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 10:1;

[0084] Fourth, the wastewater obtained in step three is cooled to -20℃ to achieve a frozen state using a cold source and maintained for 3 hours; liquid nitrogen is used as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater, which is carried out in a jacketed reactor, with liquid nitrogen introduced into the jacket.

[0085] 5. After step four is completed, the frozen wastewater is heated to room temperature and kept there for 1 hour. HPLC analysis of the wastewater showed that the phenol removal rate was 99%. Then, powdered activated carbon was added at a dosage of 0.5 g / L, and the mixture was stirred and adsorbed for 2 hours to enrich and recover the organic matter. The TOC removal rate was measured to be 93.6%. The adsorbent was then eluted, and the eluent was collected, concentrated, and dried to obtain a brownish-yellow organic matter recovery product.

[0086] Comparative Example 1

[0087] The method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0088] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a bisphenol A concentration of 0.05mmol / L and a volume of 1000 mL.

[0089] 2. Add sodium hydroxide to the wastewater obtained in step 1;

[0090] 3. Add sodium persulfate to the wastewater obtained in step 2 and mix thoroughly; the molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 10:1; the molar ratio of persulfate to sodium hydroxide is 1:4;

[0091] 4. Place the reaction solution obtained in step 3 at 25°C and stir for 3 hours.

[0092] 5. Add sulfuric acid to adjust the pH of the wastewater containing bisphenol organic matter to 5, let it stand for 5 hours to settle, filter, and no precipitate is collected;

[0093] Comparative Example 2

[0094] The method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0095] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a bisphenol A concentration of 0.05mmol / L and a volume of 1000 mL.

[0096] 2. Add 2 mmol of sodium hydroxide to the wastewater obtained in step 1;

[0097] 3. Use a cold source to cool the wastewater obtained in step 2 to -20℃ to achieve a frozen state and maintain it for 3 hours; use liquid nitrogen as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater;

[0098] 4. After step 3 is completed, the frozen wastewater is heated to room temperature and kept for 1 hour; then sulfuric acid is added to adjust the pH of the wastewater containing bisphenol organic matter to 5, and it is allowed to stand for 5 hours to settle. After filtration, no precipitate is collected.

[0099] Comparative Example 3

[0100] The method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0101] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a bisphenol A concentration of 0.05mmol / L and a volume of 1000 mL.

[0102] 2. Add sodium persulfate to the wastewater obtained in step 1 and mix thoroughly; the molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 10:1.

[0103] 3. Use a cold source to cool the wastewater obtained in step 2 to -20℃ to achieve a frozen state and maintain it for 3 hours; use liquid nitrogen as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater;

[0104] 4. After step 3 is completed, the frozen wastewater is heated to room temperature and kept for 1 hour; then sulfuric acid is added to adjust the pH of the wastewater containing bisphenol organic matter to 5, and it is allowed to stand for 5 hours to settle. After filtration, no precipitate is collected.

[0105] Comparative Example 4

[0106] The method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

[0107] 1. Suspended particles in phenolic wastewater were removed by filtration using a 0.45μm filter membrane; the phenolic wastewater was a simulated wastewater with a bisphenol A concentration of 0.05mmol / L and a volume of 1000 mL.

[0108] 2. Use a cold source to cool the wastewater obtained in step 1 to -20℃ to achieve a frozen state and maintain it for 3 hours; use liquid nitrogen as a cold source to exchange heat with the wastewater to achieve cooling and freezing of the wastewater;

[0109] 3. After step 2 is completed, the frozen wastewater is heated to room temperature and kept for 1 hour; then sulfuric acid is added to adjust the pH of the wastewater to 5, and it is allowed to stand for 5 hours to settle. After filtration, no precipitate is collected.

[0110] Figure 8 The graph shows a comparison of the bisphenol A removal rates of Example 1 and Comparative Examples 1-4. The comparison reveals that under conditions of no cold energy, no addition of sodium persulfate, no alkaline adjustment, and only freezing in Comparative Examples 1-4, a large amount of BPA residue was still detected in the treated wastewater, and no clearly separable solid products were obtained. This indicates that the cold energy-induced freeze-concentration process of this invention plays an important role in the generation and separation and recovery of bisphenol A oligomers / polymers. Persulfate is an important reactive component that promotes the oxidative coupling and polymerization transformation of bisphenol A, and alkaline conditions are beneficial for the activation of persulfate and the conversion of bisphenol A into polymeric organic matter.

[0111] Using the method of recovering organic matter from phenolic wastewater with cold energy as described in Example 1, the wastewater in step four was cooled to different temperatures, and the removal rate of bisphenol A at different freezing temperatures was tested. Figure 9 A comparison chart of bisphenol A removal rates at different freezing temperatures; Figure 9This indicates that the removal rate of bisphenol A increases within the low-temperature range, suggesting that a suitable freezing temperature is beneficial for the synergistic effect of freeze concentration and low-temperature oxidative coupling reaction.

[0112] Using the method of recovering organic matter from phenolic wastewater with cold energy as described in Example 1, the amount of sodium persulfate (PDS) added in step 3 was changed, and the removal rate of bisphenol A under different amounts of sodium persulfate (PDS) was tested. Figure 10 A comparison chart of bisphenol A removal rates with different amounts of sodium persulfate added; Figure 10 This indicates that the dosage of sodium persulfate has a significant impact on the removal rate of bisphenol A. As the dosage of sodium persulfate increases, the overall removal rate of bisphenol A improves, indicating that persulfate is an important reactive component promoting the oxidative coupling and polymerization transformation of bisphenol A. Once the dosage of sodium persulfate reaches a certain range, the increase in removal rate tends to plateau, suggesting that there is an optimal range for the dosage of oxidant in this invention.

[0113] Using the method described in Example 1 for recovering organic matter from phenolic wastewater with cold energy, the effect of different initial concentrations of bisphenol A on its removal efficiency was investigated while keeping the sodium persulfate dosage and other reaction conditions constant.

[0114] Figure 11 This is a comparison chart of bisphenol A removal rates under different initial BPA concentrations. Figure 11 The results show that the overall removal effect of the system on bisphenol A is relatively similar, indicating that the method of the present invention is not sensitive to changes in the initial pollutant concentration and has good process stability and applicability.

[0115] Using the method of recovering organic matter from phenolic wastewater with cold energy as described in Example 1, the molar ratio of sodium persulfate to sodium hydroxide in step 2 was changed, and the removal rate of bisphenol A under different molar ratios of sodium persulfate to sodium hydroxide was tested. Figure 12 A comparison chart of bisphenol A removal rates with different molar ratios of sodium persulfate to sodium hydroxide; Figure 12 This demonstrates that within the investigated molar ratio range of sodium persulfate to sodium hydroxide, the bisphenol A removal rate remained at a high level with minimal variation, indicating that the present invention has a certain tolerance to fluctuations in the PDS to NaOH ratio. Under suitable alkaline conditions, persulfate can be effectively activated, promoting the oxidative coupling and polymerization transformation of bisphenol A, thereby achieving a relatively stable treatment effect.

[0116] Using the method described in Example 1 for recovering organic matter from phenolic wastewater with cold energy, the COD and TOC removal rates were tested under different NaOH addition conditions. Figure 13 A comparison chart showing the COD removal rate of wastewater before and after filtration and sedimentation. Figure 14 The graph shows the TOC removal rate of wastewater under different NaOH addition conditions. Figure 13 and Figure 14 This demonstrates that, under suitable alkaline conditions, bisphenol A, after being treated by a cold-energy coupled alkali / PDS system, can be converted into a polymer product that can be separated by sedimentation and filtration, resulting in a further reduction in COD and TOC in the filtered wastewater. This indicates that the present invention achieves the polymerization and transformation of organic matter and resource recovery, rather than simply oxidative degradation in the traditional sense.

Claims

1. A method for recovering organic matter from phenolic wastewater using cold energy, characterized in that: The method for recovering organic matter from phenolic wastewater using cold energy is carried out according to the following steps:

1. Removal of suspended particles from phenolic wastewater; 2. Add an alkaline conditioner to the wastewater obtained in step 1; 3. Add persulfate to the wastewater obtained in step 2 and mix well; The molar ratio of persulfate to phenolic organic matter in the phenolic wastewater is 2~20:1; the molar ratio of persulfate to alkaline regulator is 1:2~4. The persulfate is one or a combination of two of sodium persulfate and potassium persulfate; Fourth, use a cold source to cool the wastewater obtained in step three to -10~-25℃ to achieve a frozen state, and maintain this state for 2~6 hours; so that the volume fraction of the ice phase in the wastewater reaches 70%~95%.

5. After step four is completed, raise the temperature of the frozen wastewater to 0~25℃ and maintain it for 0.5~3 hours; For wastewater containing bisphenols, the pH of the wastewater is adjusted to 4-7, and then solid-liquid separation is performed. For wastewater containing phenols or chlorophenols, an adsorbent is used to adsorb the organic matter in the wastewater, and then the adsorbent is eluted.

2. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The alkalinity regulator mentioned in step one is one or a combination of two of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water.

3. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The bisphenol organic compounds mentioned in step five are bisphenol A, bisphenol F, or bisphenol S.

4. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The phenolic or chlorophenolic organic compounds mentioned in step five are phenol, chlorophenol, dichlorophenol, cresol, or alkylphenol.

5. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The adsorbent used in step five is activated carbon.

6. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The solid-liquid separation process described in step five is static sedimentation, centrifugal separation, filtration, or membrane separation.

7. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 6, characterized in that: The filter membrane used in the filtration process has a pore size of 0.22~5μm.

8. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 6, characterized in that: The centrifugation speed is 4000~12000 r / min, and the time is 5~30 min.

9. The method for recovering organic matter from phenolic wastewater using cold energy according to claim 1, characterized in that: The amount of adsorbent added in step five is 0.1~2.0 g / L.

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