Method for recovering phenol from bdp wastewater and application thereof

Abstract

The present application relates to the field of wastewater recovery, and more particularly to a method for recovering phenol from BDP wastewater and application thereof.The method for recovering phenol from BDP wastewater comprises the following steps: S1, heating and alkaline decomposition of BDP wastewater; S2, conversion and precipitation of bisphenol A; S3, phenol extraction and separation of residual phenol; S4, calcium phosphate removal; S5, evaporation, cooling and crystallization post-treatment of the filtrate.The method for recovering phenol from BDP wastewater provided in the present application consumes less energy and costs less than the existing recovery process of BDP wastewater, and can simply and quickly treat 90% of the pollutants in BDP wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater recycling, and more particularly to a method for recovering phenol from BDP wastewater and its application. Background Technology

[0002] Bisphenol A bis(diphenyl phosphate), abbreviated as BDP, is a novel phosphorus-based flame retardant. However, the BDP production process generates wastewater with high salinity, high toxicity, and high COD during the washing stage; this wastewater is known as BDP wastewater. The main salts in this wastewater are NaOH and NaCl, and the main toxic components are phenol and bisphenol A, along with a large amount of large, difficult-to-degrade molecules. In recent years, with the widespread application of BDP flame retardants, the wastewater problem generated during BDP production has become a pressing technical challenge. Statistics show that approximately 2.5 tons of wastewater are generated for every ton of BDP produced. This wastewater exhibits high bioinhibitory activity, making it difficult to treat using traditional physicochemical and biochemical methods, and the high salinity further complicates treatment.

[0003] Currently, the treatment of BDP wastewater mainly employs a combination of physicochemical and biological methods. Physicochemical methods include incineration, wet oxidation, Fenton chromatography, flocculation, and MVR distillation; biological methods mainly include activated sludge and biofilm processes. However, due to the high toxicity, recalcitrant nature, and poor biodegradability of organic matter in the wastewater, direct introduction into the biological system can severely impact microorganisms and inhibit their growth. Furthermore, while biological methods are effective at treating aliphatic hydrocarbons, they are less effective at treating highly toxic aromatic compounds, especially since the wastewater contains a large amount of polycyclic aromatic hydrocarbons.

[0004] The prior art CN108609804B provides a method for treating BDP wastewater, which uses a combination of ozone oxidation, biochemical treatment, and membrane treatment to treat BDP wastewater, and claims that it can ultimately reduce the COD concentration of BDP wastewater to 40 mg / L and the salinity to 500 mg / L. However, it still does not effectively treat the highly toxic phenol and bisphenol A substances in BDP wastewater.

[0005] Therefore, in order to solve the above problems, this application provides a method for recovering phenol from BDP wastewater. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this application provides a method for recovering phenol from BDP wastewater, characterized by the following steps: S1: heating and alkaline decomposition of BDP wastewater; S2: conversion and precipitation of bisphenol A; S3: phenol extraction and separation of phenol from the residue; S4: removal of calcium phosphate; S5: evaporation, cooling, and crystallization post-treatment of the filtrate.

[0007] As a preferred embodiment, the pH value of the BDP wastewater is ≥14; the mass percentage concentration of NaOH in the BDP wastewater is 2-3%; and the COD in the BDP wastewater is 28000-32000 mg / L.

[0008] As a preferred embodiment, the specific operation of S1 is as follows: add BDP wastewater to a pressure stirring vessel, turn on the stirring and heat to the alkaline decomposition temperature, control the environmental pressure inside the vessel, and after the BDP wastewater has been heated and alkaline decomposed, discharge the material and allow it to cool naturally to room temperature.

[0009] As a preferred embodiment, the heating alkaline decomposition temperature in S1 is 150–180°C, the ambient pressure is 0.5–0.8 MPa, and the heating alkaline decomposition time is 30–60 min.

[0010] As a preferred embodiment, the heating alkaline decomposition temperature in S1 is 160–175°C, and the ambient pressure is 0.6–0.7 MPa; the heating alkaline decomposition time is 30–40 min.

[0011] As a preferred embodiment, the heating alkaline decomposition temperature in S1 is 160-165℃, the ambient pressure is 0.6-0.65MPa, and the heating alkaline decomposition time is 30min.

[0012] As a preferred embodiment, the specific operation of S2 is as follows: adding hydrochloric acid to the wastewater after heating and alkaline decomposition to adjust the pH, cooling to precipitate bisphenol A solid, and then filtering to obtain crude bisphenol A and filtrate.

[0013] As a preferred embodiment, hydrochloric acid is added to the wastewater in step S2 to adjust the pH to 7-7.5.

[0014] As a preferred embodiment, hydrochloric acid is added to the wastewater in step S2 to adjust the pH to 7.

[0015] As a preferred embodiment, the hydrochloric acid has a mass concentration of 5 wt%.

[0016] As a preferred embodiment, the specific operation of S3 is as follows: the filtrate obtained in S2 is added to kerosene for extraction 1 to 3 times, and the extracts are combined. After removing the kerosene, crude phenol is obtained.

[0017] As a preferred embodiment, the volume ratio of the filtrate to kerosene is 1-1.2:0.2-0.3.

[0018] As a preferred embodiment, the volume ratio of the filtrate to kerosene is 1:0.25.

[0019] As a preferred embodiment, the specific operation of S4 is as follows: calcium chloride is added to the raffinate obtained in S3, stirred for 20-40 minutes, and then filtered to obtain wet calcium phosphate.

[0020] In this application, the combined implementation of the above steps can effectively improve the recovery rate of toxic substances in BDP wastewater and recover 90% of the organic matter in the wastewater, significantly reducing the cost of subsequent wastewater treatment. The applicant believes that by utilizing the alkaline hydrolysis effect of heating under the alkaline conditions of BDP wastewater, the sodium phosphate salts in the wastewater are gradually decomposed into phenol, bisphenol A, and sodium phosphate salts, thereby directly decomposing the main pollutants into three independent parts. Furthermore, by employing separate and independent separation operations to separate these three substances, the pollutant recovery efficiency of BDP wastewater during the recovery process can be greatly improved, and the purity of the recovered substances can also be further improved, thereby achieving the recycling of these substances.

[0021] As a preferred embodiment, the mass ratio of the raffinate phase to calcium chloride is 100-200:2-4.

[0022] As a preferred embodiment, the specific operation of S5 is as follows: the filtrate collected in S4 is evaporated, cooled, and recrystallized to obtain sodium chloride.

[0023] The second aspect of this application provides an application of the above-mentioned method for recovering phenol from BDP wastewater, including its application in a process for recovering phenol from organic polluted wastewater.

[0024] Beneficial effects:

[0025] 1. The method for recovering phenol from BDP wastewater provided in this application consumes less energy and has lower cost compared to existing BDP wastewater recovery processes, and can simply and quickly treat 90% of pollutants in BDP wastewater.

[0026] 2. The method for recovering phenol from BDP wastewater provided in this application requires less equipment and has fewer requirements. It does not suffer from severe equipment corrosion and can reduce the time and cost of equipment maintenance.

[0027] 3. The method for recovering phenol from BDP wastewater provided in this application can effectively improve the recovery rate of toxic substances in BDP wastewater. By utilizing the alkaline hydrolysis effect of heating under the alkaline conditions of BDP wastewater, the sodium phosphate salt in the wastewater is gradually decomposed into phenol, bisphenol A and sodium phosphate salt, thereby directly decomposing the main pollutants into three independent parts. Furthermore, the above three substances are separated by separate operations, which can greatly improve the pollutant recovery efficiency of BDP wastewater in the recovery process.

[0028] 4. The method for recovering phenol from BDP wastewater provided in this application can be used as a pretreatment process for a more refined recovery process. It can quickly recover most of the organic pollutants in BDP wastewater, saving enterprises a lot of BDP recovery costs.

[0029] 5. The method for recovering phenol from BDP wastewater provided in this application can accurately, effectively and quickly recover phenol and bisphenol A materials from BDP wastewater, and can ensure that the purity of the recovered materials is above 99%. Detailed Implementation

[0030] Example 1

[0031] Example 1 provides a method for recovering phenol from BDP wastewater, characterized by the following steps: S1: heating and alkaline decomposition of BDP wastewater; S2: conversion and precipitation of bisphenol A; S3: phenol extraction and separation of phenol from the residue; S4: removal of calcium phosphate; S5: evaporation, cooling and crystallization of the filtrate.

[0032] The total amount of wastewater is 500 parts by weight.

[0033] The pH value of the BDP wastewater is 14; the mass percentage concentration of NaOH in the BDP wastewater is 2.5%; and the COD in the BDP wastewater is 30,000 mg / L.

[0034] The specific operation of S1 is as follows: add BDP wastewater into a pressure stirring vessel, turn on the stirring and heat it to the alkaline decomposition temperature, control the environmental pressure inside the vessel, and after the BDP wastewater has been heated and decomposed into alkaline substances, discharge the material and allow it to cool naturally to room temperature.

[0035] The heating alkaline decomposition temperature in S1 is 162℃, the ambient pressure is 0.63MPa, and the heating alkaline decomposition time is 30min.

[0036] The specific operation of S2 is as follows: add hydrochloric acid to the wastewater after heating and alkaline decomposition to adjust the pH, cool down to precipitate bisphenol A solid, and then filter to obtain crude bisphenol A and filtrate.

[0037] In S2, hydrochloric acid was added to adjust the pH of the wastewater to 7; the mass concentration of hydrochloric acid was 5 wt%.

[0038] The specific operation of S3 is as follows: the filtrate obtained from S2 is added to kerosene for extraction twice, and the extracts are combined. After removing the kerosene, crude phenol is obtained.

[0039] The volume ratio of filtrate to kerosene is 1:0.25.

[0040] The specific operation of S4 is as follows: add calcium chloride to the raffinate obtained in S3, stir for 30 minutes, and then filter to obtain wet calcium phosphate.

[0041] The mass ratio of the raffinate to calcium chloride is 150:2.5.

[0042] The specific operation of S5 is as follows: the filtrate collected in S4 is evaporated, cooled, and recrystallized to obtain sodium chloride.

[0043] Example 2

[0044] The specific implementation method of this embodiment is the same as that of Embodiment 1, except that: the heating alkaline decomposition temperature in S1 is 172°C, the ambient pressure is 0.68 MPa, and the heating alkaline decomposition time is 45 min.

[0045] Example 3

[0046] The specific implementation method of this embodiment is the same as that of embodiment 2, except that the total amount of wastewater is 5000 parts by mass.

[0047] Performance Evaluation

[0048] Purity of recovered substances: The purity of phenol and bisphenol A recovered from the examples and comparative examples was tested. Ten samples were tested for each example and comparative example, and the average value of the measured values ​​was recorded in Table 1.

[0049] BDP wastewater impurity retention: The total phosphorus content, phenol content, and COD content of the treated wastewater obtained in the examples and comparative examples were tested. Ten samples were tested for each example and comparative example, and the average value of the measured values ​​was recorded in Table 2.

[0050] Table 1

[0051]

[0052]

[0053] Table 2

[0054] Example 1 12.3 14 3248 Example 2 8.5 13 2986 Example 3 8.6 12.8 3014

Claims

1. A method for recovering phenol from BDP wastewater, characterized in that: The process includes the following steps: S1: Alkaline decomposition of BDP wastewater by heating; S2: Conversion and precipitation of bisphenol A; S3: Phenol extraction and phenol separation from the residue; S4: Removal of calcium phosphate; S5: Evaporation, cooling and crystallization post-treatment of the filtrate. The total volume of wastewater is 500 or 5000 parts by weight. The pH value of the BDP wastewater is 14; the mass percentage concentration of NaOH in the BDP wastewater is 2.5%; and the COD in the BDP wastewater is 30,000 mg / L. The specific operation of S1 is as follows: add BDP wastewater into a pressure stirring vessel, turn on the stirring and heat it to the alkaline decomposition temperature, control the environmental pressure inside the vessel, and after the BDP wastewater has been heated and decomposed into alkaline substances, discharge the material and let it cool naturally to room temperature. The heating alkaline decomposition temperature in S1 is 162 or 172℃, the ambient pressure is 0.63 or 0.68 MPa, and the heating alkaline decomposition time is 30 or 45 min. The specific operation of S2 is as follows: add hydrochloric acid to the wastewater after heating and alkaline decomposition to adjust the pH, cool down to precipitate bisphenol A solid, and then filter to obtain crude bisphenol A and filtrate. In wastewater S2, hydrochloric acid was added to adjust the pH to 7; the mass concentration of hydrochloric acid was 5 wt%. The specific operation of S3 is as follows: the filtrate obtained from S2 is added to kerosene for extraction twice, and the extracts are combined. After removing the kerosene, crude phenol is obtained. The volume ratio of filtrate to kerosene is 1:0.25; The specific operation of S4 is as follows: add calcium chloride to the raffinate obtained in S3, stir for 30 minutes, and then filter to obtain wet calcium phosphate. The mass ratio of the raffinate to calcium chloride was 150:2.5; The specific operation of S5 is as follows: the filtrate collected in S4 is evaporated, cooled, and recrystallized to obtain sodium chloride.

2. An application of the method for recovering phenol from BDP wastewater according to claim 1, characterized in that: This includes the application of this method in the process of recovering phenol from organically polluted wastewater.

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