A method for treating bisphenol a type epoxy resin wastewater by using calcium bentonite

Abstract

This invention discloses a method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite. The method includes the following steps: centrifuging bentonite powder N times (N=2~3) according to a centrifugation treatment method, collecting the calcium-based bentonite suspension and calcium-based bentonite; mixing the calcium-based bentonite suspension with the bisphenol A type epoxy resin wastewater, adding calcium-based bentonite to obtain a mixed solution; stirring the mixed solution at 50~90 °C, allowing it to stand, and centrifuging to obtain organically modified sodium bentonite with industrial application value and purified wastewater with COD emission levels meeting standards. This method significantly reduces the COD content of bisphenol A type epoxy resin wastewater, meeting the direct COD emission standard in the Chinese national standard GB 31572-2015 "Emission Standard of Pollutants for Synthetic Resin Industry". It requires no chemical modification agents, causes no secondary pollution, has mild reaction conditions, a simple process flow, and low production costs.

Description

Technical Field

[0001] This invention relates to the field of bisphenol A type epoxy resin wastewater treatment technology, and more particularly to a method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite. Background Technology

[0002] Bisphenol A type epoxy resin, as the most widely used general-purpose thermosetting synthetic resin, possesses advantages such as high bonding strength, excellent insulation, chemical corrosion resistance, and stable mechanical properties. It is widely used in industrial fields such as chemical corrosion protection, building materials, electronics, composite materials, and coatings and adhesives. Currently, most industries use epichlorohydrin (ECH) and bisphenol A (BPA) compounds as raw materials, and prepare crude resin through a dehydrogenation condensation reaction in the presence of NaOH as a catalyst. The crude resin is then washed and refined into bisphenol A type epoxy resin. The resulting bisphenol A type epoxy resin wastewater (pH=13~14), including polymerization mother liquor, neutralization washing wastewater, equipment cleaning wastewater, and process cooling drainage, contains high concentrations of NaOH. + Epoxy resin wastewater is typically used as a de-icing agent after evaporation treatment. However, it is a typical high-concentration, recalcitrant organic chemical wastewater, rich in bisphenol A, epichlorohydrin, residual organic solvents, organohalides, and resin oligomers—organic pollutants with teratogenic, carcinogenic, and endocrine-disrupting toxicity. It is characterized by high chemical oxygen demand (COD) values, which can pollute soil and groundwater, harming plant and animal growth and human health. Direct discharge of untreated epoxy resin wastewater not only causes water turbidity and increased color but also inhibits the activity of aquatic microorganisms and disrupts the aquatic ecological balance. Therefore, the harmless treatment of bisphenol A type epoxy resin wastewater is a key research topic in the chemical environmental protection field.

[0003] Currently, commonly used industrial treatment methods for bisphenol A type epoxy resin wastewater mainly include biochemical treatment, advanced oxidation, coagulation and sedimentation, and extraction. Among these, biochemical treatment is limited by the high toxicity and salinity of the wastewater, and microbial activity is easily inhibited, resulting in low treatment efficiency. Advanced oxidation has excellent treatment effects, but its equipment investment cost is high, reagent consumption is large, and operation and maintenance are cumbersome, leading to high costs for industrial application. Extraction methods suffer from drawbacks such as easy extraction solvent residue, serious secondary pollution, and complex recovery processes. Conventional coagulation and sedimentation methods have limited removal capacity for small molecule phenolic organic matter, making it difficult to meet high emission standards. In summary, existing treatment processes generally suffer from high costs, secondary pollution, limited treatment effects, and complex operation.

[0004] Bentonite is a clay mineral with montmorillonite as its main mineral component. It possesses a unique layered crystal structure and exhibits excellent physical and chemical properties, including a large specific surface area, strong adsorption capacity, superior cation exchange performance, and well-developed pore structure. Furthermore, it is abundant in natural mineral reserves, inexpensive, non-toxic, and pollution-free, making it a high-quality environmentally friendly adsorbent material. Calcium-based bentonite is the mainstream type of natural bentonite. However, raw calcium-based bentonite suffers from high impurity content, poor dispersibility, and weak adsorption selectivity. Unrefined raw ore is ineffective in adsorbing and removing organic pollutants from wastewater, limiting its application in wastewater treatment. Current research largely focuses on artificially chemically modified bentonite. However, the modifying agents are prone to causing secondary pollution, and the preparation process is complex and costly. Therefore, there is an urgent need to develop a low-cost, environmentally friendly, easy-to-operate, and stable bisphenol A type epoxy resin wastewater treatment technology based on calcium-based bentonite, simultaneously realizing the dual application value of efficient sodium-based organic modification of calcium-based bentonite and industrial wastewater purification. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite. This method involves multi-stage purification (centrifugal separation) of raw bentonite ore through physical purification to remove ore impurities and improve adsorption performance. The purified solid bentonite adsorbent (calcium-based bentonite) is then used in conjunction with the purification mother liquor (calcium-based bentonite suspension) to couple the treatment of bisphenol A type epoxy resin wastewater. This process efficiently adsorbs toxic organic pollutants such as epichlorohydrin and bisphenol A from the wastewater, achieving comprehensive utilization of solid and liquid resources. Simultaneously, the sodium ions abundant in the bisphenol A type epoxy resin wastewater displace calcium ions from the interlayer of the calcium-based bentonite, transforming it into organically modified sodium-based bentonite with industrial application value.

[0006] To achieve the above objectives, the present invention is accomplished through the following technical solutions.

[0007] A method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite includes the following steps:

[0008] S1, the bentonite powder is centrifuged N times according to the centrifugation treatment method, N=2~3, and the upper layer solution after each centrifugation is collected as calcium-based bentonite suspension. The solid precipitate obtained after N centrifugations is dried and crushed as calcium-based bentonite. The centrifugation treatment method includes: adding water to the solid to be centrifuged and stirring evenly, letting it stand, taking the upper layer suspension and centrifuging to obtain the upper layer solution and solid precipitate. In S1, the operation of obtaining bentonite powder involves crushing and sieving the raw bentonite ore to obtain bentonite powder.

[0009] In the above technical solution, the bentonite ore is a clay rock with montmorillonite as its core.

[0010] The chemical composition of the calcium-based bentonite includes SiO2, Al2O3, Fe2O3, FeO, CaO, MgO, Na2O and K2O.

[0011] In the above technical solution, the mesh size of the sieve is 100~325 mesh.

[0012] In S1, the solid to be centrifuged is bentonite powder or a solid precipitate obtained after a previous centrifugation.

[0013] In step S1, water is added to the solid to be centrifuged and stirred evenly, and the content of the solid to be centrifuged in water is controlled to be 10~30wt%.

[0014] In step S1, the centrifugation speed is 4000~5000 r / min, and the centrifugation time is 10~50 min.

[0015] In step S1, the drying temperature is 80~120 ℃, and the drying time is 20~24 h.

[0016] In S1, the settling time is 5 to 10 minutes.

[0017] S2, a calcium-based bentonite suspension is mixed with bisphenol A type epoxy resin wastewater, calcium-based bentonite is added to obtain a mixed solution, the mixed solution is stirred at 50~90 ℃ for 2~6 h, allowed to stand, centrifuged, the supernatant is the purified wastewater, and the solid precipitate is organic modified sodium bentonite. The volume fraction of the calcium-based bentonite suspension, the volume fraction of the bisphenol A type epoxy resin wastewater and the mass fraction of the calcium-based bentonite are (150~300):(50~150):(30~60), the volume fraction is in mL and the mass fraction is in g.

[0018] In S2, the bisphenol A type epoxy resin wastewater includes epichlorohydrin, bisphenol A, organic halides other than epichlorohydrin, glycerol, resin oligomers, and sodium. + and Cl - .

[0019] In step S2, the pH of the bisphenol A type epoxy resin wastewater is 13-14.

[0020] In step S2, the centrifugation speed is 4000~5000 r / min, and the centrifugation time is 2~5 min.

[0021] In step S1, the settling time is 24-36 hours (during which the pH of the mixture is neutral). Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method of the present invention can effectively remove internal soluble impurities and clay agglomerates after the bentonite ore is purified by multi-stage centrifugal washing. The resulting calcium-based bentonite, combined with trace colloidal ions in the calcium-based bentonite suspension, forms a coupled adsorption system that can efficiently capture difficult-to-degrade organic pollutants such as epichlorohydrin, bisphenol A and glycerol in bisphenol A type epoxy resin wastewater, significantly reducing the COD content of the water body. It can meet the direct COD emission standard in the Chinese national standard GB 31572-2015 "Emission Standard of Pollutants for Synthetic Resin Industry", and the purification effect is stable.

[0022] (2) The method of the present invention, while treating bisphenol A type epoxy resin wastewater, utilizes the abundant Na ions in the wastewater to replace the calcium ions between the calcium-based bentonite layers, thereby converting the calcium-based bentonite into organically modified sodium bentonite. This organically modified sodium bentonite has broad industrial application value in the field of composite materials, further reduces treatment costs, and possesses excellent recycling performance and engineering application value.

[0023] (3) The method of the present invention does not add strong acid, strong alkali or other chemical modifying agents, thus avoiding the problem of secondary pollution caused by agent residue. The upper suspension and upper solution generated during the purification process are all recycled and reused, realizing the closed-loop utilization of materials, with low waste discharge and green and environmentally friendly process.

[0024] (4) The method of the present invention has a simple process flow and mild reaction conditions. It does not require a harsh environment of high temperature and high pressure. It can be completed with conventional chemical equipment. It is suitable for the production conditions of small and medium-sized bisphenol A type epoxy resin enterprises and has strong industrial promotion. Moreover, the treated wastewater system has fast floc settling and clear solid-liquid stratification, and the subsequent separation operation is simple.

[0025] (5) The method of the present invention uses natural bentonite ore, which is abundant and inexpensive, as the raw material for processing. Compared with commercial adsorption materials such as activated carbon and modified molecular sieves, the raw material cost is lower. Moreover, the entire process is prepared by physical purification, without the need for expensive chemical reagents and special modification equipment. The overall production cost is low and the economic applicability is strong. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the method of the present invention; Figure 2 The images show the XRD patterns of the organically modified sodium bentonite, calcium-based bentonite, and Na2CO3 sodium bentonite obtained in Example 1 of this invention. Detailed Implementation

[0027] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0028] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0029] In the following embodiments, the bentonite ore originates from Jianping County, Chaoyang City, Liaoning Province; the bentonite ore is a clay rock with montmorillonite as its core, containing a small amount of impurity minerals and various chemical oxides, with a montmorillonite content of approximately 80%.

[0030] In the following examples, the main chemical composition of calcium-based bentonite includes: SiO2 (61.46 wt%), Al2O3 (14.93 wt%), Fe2O3 (0.97 wt%), FeO (0.13 wt%), CaO (1.83 wt%), MgO (3.01 wt%), Na2O (0.24 wt%), and K2O (0.067 wt%).

[0031] In the following examples, the bisphenol A type epoxy resin wastewater comes from the production process of Dalian Qihua New Materials Co., Ltd. This process uses epichlorohydrin and bisphenol A compounds as raw materials, and performs a dehydrogenation condensation reaction in the presence of NaOH as a catalyst to prepare bisphenol A type epoxy resin. The bisphenol A type epoxy resin wastewater mainly includes unreacted raw materials (epicochlorohydrin, bisphenol A), byproducts (glycerol, other organic halides), reaction intermediates (resin oligomers), and other organic pollutants, as well as NaOH. + Cl - Inorganic ions, etc.

[0032] In the following embodiments, before the first centrifugation of the upper suspension, the lower precipitate formed after standing can be repeatedly rinsed until the liquid phase of the system is clear after adding water and mixing. The rinsing liquid is collected and added to the upper suspension for centrifugation, thereby realizing the efficient utilization of calcium-based bentonite resources.

[0033] In the following examples, when centrifuging bentonite powder according to the centrifugation treatment method, the settling time is 10 min; when centrifuging the solid precipitate obtained after the previous centrifugation according to the centrifugation treatment method, the settling time is 5 min.

[0034] Examples 1-3 and Comparative Example 1 A method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite, such as... Figure 1 As shown, it includes the following steps: S1. The raw bentonite ore is crushed using a pulverizer and passed through a 100-mesh sieve to obtain bentonite powder. The bentonite powder is centrifuged N times according to the centrifugation treatment method, N=3. The upper layer solution obtained from each centrifugation is collected as a calcium-based bentonite suspension. The solid precipitate obtained after N centrifugations is dried at 80 ℃ for 24 h and crushed to obtain calcium-based bentonite. The centrifugation treatment method includes: adding water to the solid to be centrifuged (calcium-based bentonite powder or solid precipitate obtained from the previous centrifugation), controlling the content of the solid to be centrifuged in water to be 30 wt%, stirring evenly, and letting it stand (the system is divided into upper suspension and lower precipitate). The upper suspension is centrifuged at 5000 r / min for 30 min to obtain the upper solution and solid precipitate.

[0035] S2, the calcium-based bentonite suspension was mixed with bisphenol A type epoxy resin wastewater, and calcium-based bentonite was added to obtain a mixture. The mixture was stirred at 70 °C for 4 h and allowed to stand for 24 h (pH=7 in Examples 1-3 at this time). The mixture was centrifuged at 5000 r / min for 5 min to obtain the supernatant as purified wastewater and the solid precipitate as organic modified sodium bentonite. The ratio of the volume fraction of the calcium-based bentonite suspension, the volume fraction of the bisphenol A type epoxy resin wastewater and the mass fraction of the calcium-based bentonite is G. The volume fraction is in mL and the mass fraction is in g.

[0036] The values ​​of G in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0037] Table 1

[0038] The organically modified sodium bentonite obtained in Example 1, the calcium-based bentonite obtained in S1, and the Na2CO3 sodium bentonite (purchased from Jianping Weike Dongming Mining Co., Ltd.) were subjected to XRD analysis. The XRD patterns are shown in the figure. Figure 2 As shown. By Figure 2 It can be seen that the purified calcium-based bentonite exhibits obvious montmorillonite (001) crystal plane characteristic diffraction peaks in the low-angle region (2θ≈5.0~6.0°). According to the Bragg equation, the corresponding interplanar spacing d is calculated. 001 The wavelength is approximately 1.4–1.5 nm, which is typical of calcium-based bentonite, indicating that the interlayer is mainly composed of hydrated Ca. 2+ The interlayer hydration is high, and the interlayer spacing is large. The (001) diffraction peak of the organically modified sodium bentonite obtained after treating bisphenol A type epoxy resin wastewater with calcium-based bentonite shifts to a higher angle, with the peak position moving to 2θ≈5.0~7.5°, and the interlayer spacing decreasing to 1.2~1.3 nm. This is due to the high degree of interlayer hydration and large interlayer spacing of Na. + Replacement interlayer Ca 2+The resulting typical sodium-based structural characteristics, compared to simple sodium-modified bentonite (i.e., Na2CO3 sodium-modified bentonite), show that the sharp (001) crystal plane diffraction peaks of the organically modified sodium-modified bentonite have basically disappeared, exhibiting a broad and diffuse bulging morphology. The peak intensity has decreased significantly, and the peak shape has broadened considerably, indicating that the organic macromolecules in the wastewater have successfully inserted between the montmorillonite lamellae, disrupting the original orderly lamellae stacking structure of montmorillonite and reducing the crystal order and crystal integrity. In summary, the organically modified sodium-modified bentonite obtained after treating bisphenol A type epoxy resin wastewater with calcium-based bentonite possesses both sodium-modification and organic intercalation characteristics.

[0039] The purified wastewater and bisphenol A type epoxy resin wastewater obtained by the methods of Examples 1-3 and Comparative Example 1 were subjected to chemical oxygen demand (COD) analysis. The test reagent used was Huajianlianke rapid water quality test kit (COD measurement range: 0~10000 mg / L). This test kit directly gives the approximate concentration range of COD by colorimetric method. The test results are shown in Table 2.

[0040] Table 2

[0041] Table 2 shows that the COD of the purified wastewater obtained by the method in Comparative Example 1 is within the range of 50-100 mg / L, exceeding the direct COD emission standard (60 mg / L) in the Chinese National Standard GB 31572-2015 "Emission Standard of Pollutants for Synthetic Resin Industry". The pH of the purified wastewater is 9, indicating weak alkalinity. The COD of the purified wastewater obtained by the methods in Examples 1-3 of this invention is all less than 50 mg / L, significantly reducing the chemical oxygen demand (COD) of the bisphenol A epoxy resin wastewater. Furthermore, the purified wastewater changes from strongly alkaline to neutral. In summary, the bisphenol A epoxy resin wastewater treated by the method of this invention meets the national emission standards.

[0042] After treating bisphenol A type epoxy resin wastewater with calcium-based bentonite, the hydrated Ca occupied in the interlayer... 2+ Na contained in bisphenol A type epoxy resin wastewater + The calcium ions displaced from the purified wastewater are free in the purified wastewater. Therefore, the concentration of residual calcium ions in the purified wastewater is used to characterize the calcium removal effect. To eliminate the potential influence of calcium ions contained in the bisphenol A epoxy resin wastewater itself on the experimental results, excess Na2CO3 solution was added to the bisphenol A epoxy resin wastewater. No precipitation was observed, indicating that calcium ions were not present in the wastewater. Based on this, the sodium content in the purified wastewater obtained in Examples 1-3 was determined by the sodium carbonate precipitation method.

[0043] Sodium carbonate precipitation method: Add excess Na₂CO₃ solution to the purified wastewater until precipitation is complete, so that Ca... 2+The precipitate was completely converted to CaCO3, filtered, washed with deionized water, dried at 80 ℃ for 24 h, and then weighed. The mass of the precipitate was marked as m. CaCO3 The sodiumization rate of calcium-based bentonite was calculated. The formula for calculating the sodiumization rate η is as follows, and the sodiumization rate η is shown in Table 3.

[0044] , where m 样 The mass of the calcium-based bentonite used.

[0045] Table 3

[0046] Table 3 shows that the average sodiumization rate of the calcium-based bentonite ore after wastewater treatment is approximately 25%, indicating a significant sodiumization effect. This demonstrates that the method of this invention can effectively achieve sodiumization modification of calcium-based bentonite while treating bisphenol A type epoxy resin wastewater, and the ion exchange effect significantly reduces the interlayer Ca content. 2+ The content was optimized, improving the colloidal properties and adsorption capacity of bentonite, achieving the dual effect of "treating waste with waste".

[0047] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for treating bisphenol A type epoxy resin wastewater using calcium-based bentonite, characterized in that, Includes the following steps: S1, the bentonite powder is centrifuged N times according to the centrifugation treatment method, N=2~3, and the upper layer solution after each centrifugation is collected as calcium-based bentonite suspension. The solid precipitate obtained after N centrifugations is dried and crushed as calcium-based bentonite. The centrifugation treatment method includes: adding water to the solid to be centrifuged and stirring evenly, letting it stand, taking the upper layer suspension and centrifuging to obtain the upper layer solution and solid precipitate. S2, a calcium-based bentonite suspension is mixed with bisphenol A type epoxy resin wastewater, calcium-based bentonite is added to obtain a mixed solution, the mixed solution is stirred at 50~90 ℃ for 2~6 h, allowed to stand, centrifuged, the supernatant is the purified wastewater, and the solid precipitate is organic modified sodium bentonite. The volume fraction of the calcium-based bentonite suspension, the volume fraction of the bisphenol A type epoxy resin wastewater and the mass fraction of the calcium-based bentonite are (150~300):(50~150):(30~60), the volume fraction is in mL and the mass fraction is in g.

2. The method according to claim 1, characterized in that, The chemical composition of the calcium-based bentonite includes SiO2, Al2O3, Fe2O3, FeO, CaO, MgO, Na2O and K2O.

3. The method according to claim 1, characterized in that, The process of obtaining bentonite powder involves crushing and sieving the raw bentonite ore to obtain bentonite powder.

4. The method according to claim 3, characterized in that, The sieve mesh size is 100~325 mesh.

5. The method according to claim 1, characterized in that, The centrifugation speed is 4000~5000 r / min; in S1, the centrifugation time is 10~50 min; in S2, the centrifugation time is 2~5 min.

6. The method according to claim 1, characterized in that, Add water to the solid to be centrifuged and stir evenly, controlling the content of the solid to be centrifuged in water to be 10~30 wt%.

7. The method according to claim 1, characterized in that, In S1, the settling time is 5~10 min; In S2, the settling time is 24~36 h.

8. The method according to claim 1, characterized in that, The drying temperature is 80~120 ℃, and the drying time is 20~24 h.

9. The method according to claim 1, characterized in that, The bisphenol A type epoxy resin wastewater includes epichlorohydrin, bisphenol A, organic halides other than epichlorohydrin, glycerol, resin oligomers, and sodium. + and Cl - .

10. The method according to claim 1, characterized in that, The pH of the bisphenol A type epoxy resin wastewater is 13-14.

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