Method for resource utilization of bubble food waste water and application of recovered material thereof

Abstract

This invention discloses a method for the resource utilization of grain soaking wastewater and the application of its recovered products. The method specifically includes the following steps: (1) removing suspended matter from the grain soaking wastewater and then concentrating it under reduced pressure to obtain a wastewater concentrate; (2) adjusting the pH of the wastewater concentrate to 8.0, then allowing it to stand to precipitate, followed by centrifugation to obtain acid-soluble substances, and collecting the supernatant for later use; (3) using macroporous resin to adsorb and separate phenolic acids in the supernatant, collecting the eluent, and distilling under reduced pressure to obtain phenolic acids, and collecting the polysaccharide-rich purified water for later use; (4) using Sevage reagent to remove protein from the purified water in step (3), concentrating it under reduced pressure to a viscous state, then adding 80% ethanol solution, ultrasonically vibrating for 30 minutes, allowing it to stand to precipitate, and then centrifuging to obtain polysaccharides. This invention can separate and recover acid-soluble substances, phenolic acids, and polysaccharides from grain soaking wastewater, realizing the resource utilization of grain soaking wastewater and reducing carbon emissions.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology, specifically relating to a method for the resource utilization of grain soaking wastewater and the application of its recycled materials. Background Technology

[0002] Baijiu, a representative of traditional Chinese alcoholic beverages, boasts a long history and unique flavor. As a distilled spirit unique to my country, baijiu is typically made from sorghum and other grains using traditional methods. The process involves crushing and fermenting the raw materials, followed by distillation, storage, and blending. The production, storage, and aging of baijiu generate significant amounts of industrial wastewater. Wastewater from the brewing process, including bottom-boiling water, yellow water, and grain-soaking water, contains high levels of organic matter and is a major cause of environmental pollution. According to incomplete statistics, baijiu brewing enterprises discharge 12-20 tons of industrial wastewater for every ton of baijiu produced, making the alcohol production industry the sector with the highest concentration of organic pollutants. The high-concentration organic wastewater from brewing contains large amounts of organic matter and suspended solids, with high levels of total nitrogen, total phosphorus, chemical oxygen demand (COD), and biological oxygen demand (BOD). Direct discharge into rivers can cause severe eutrophication, leading to environmental pollution.

[0003] Sichuan, as the largest baijiu (white liquor) production base in China, accounts for over 40% of the national total baijiu output, earning it the reputation of "Sichuan baijiu is the best in the world." Xiaoqu baijiu, as one of the main types of baijiu, accounts for approximately 30% of the annual baijiu production. It is characterized by its long history, unique flavor, large production volume, and wide influence, making it a crucial component of Sichuan baijiu's competitive advantage. Sorghum, the main raw material for Xiaoqu baijiu, has long been hailed as the "essence of grains" and the "leader of all grains," containing abundant soluble polysaccharides, phenolic acids, tannins, and other functional components. The soaking process in Xiaoqu baijiu production allows the sorghum to absorb water and swell, loosening its starch structure and creating conditions for gelatinization during cooking. The wastewater generated from soaking the sorghum contains abundant soluble polysaccharides, phenolic acids, tannins, 3-deoxyanthocyanins, and other nutrients. Traditional wastewater treatment methods rely on biochemical degradation to meet discharge standards, which not only wastes the abundant organic matter but also increases the difficulty of wastewater treatment.

[0004] Wastewater resource utilization and the extraction of other resources and energy from wastewater are of great significance for optimizing water supply structure, increasing water supply, alleviating supply and demand imbalances, reducing water pollution, and ensuring water ecological security. Therefore, providing a treatment method that can recycle resources, reduce carbon emissions, and simultaneously consider environmental, social, and economic benefits will inevitably become the future direction for wastewater treatment in the liquor industry. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for the resource utilization of grain soaking wastewater and the application of the recovered products. This invention can separate and recover acid-soluble substances, phenolic acids and polysaccharides from grain soaking wastewater, realize the resource utilization of grain soaking wastewater and reduce carbon emissions.

[0006] The technical solution of this invention is implemented as follows:

[0007] A method for the resource utilization of grain soaking wastewater specifically includes the following steps:

[0008] (1) Remove suspended matter from the grain soaking wastewater, and then concentrate it by vacuum distillation 5-10 times to obtain wastewater concentrate; here, the grain soaking wastewater is concentrated, which can enrich the organic matter in the grain soaking wastewater, and at the same time, it is easy to reduce the volume and store it.

[0009] (2) Adjust the pH of the wastewater concentrate to 8.0, then let it stand at 4-10℃ to precipitate the precipitate, then centrifuge to obtain the acid-soluble substance, and collect the supernatant for later use.

[0010] (3) Phenolic acid substances in the supernatant are adsorbed and separated by macroporous resin. The eluent is collected and distilled under reduced pressure to obtain phenolic acid substances. The water rich in polysaccharides is collected for later use.

[0011] (4) Use Sevage reagent to remove the protein in the impurity-removed water in step (3), then concentrate it to a viscous state by vacuum distillation, then add 80% ethanol solution, sonicate for 15-30 min, let it stand at 4-10℃ to precipitate, and then centrifuge to obtain polysaccharide. The mass-volume ratio of the viscous solution to the 80% ethanol solution is 1g: 5-15mL.

[0012] Furthermore, in step (2), the pH is adjusted using a 0.5M sodium hydroxide solution.

[0013] Furthermore, in step (3), the macroporous resin is DM301 type macroporous resin.

[0014] Furthermore, the adsorption separation conditions are as follows: the pH of the supernatant is adjusted to 4.0–7.0 using 0.5M NaOH; 80% ethanol is selected as the eluent; the adsorption capacity of the resin is 3 BV; the amount of impurity removal water is 3 BV; and the amount of eluent is 3 BV.

[0015] Furthermore, the Sevage reagent is prepared by mixing chloroform and n-butanol in a volume ratio of 4:1.

[0016] The aforementioned acid-soluble substances, phenolic acids, or polysaccharides are used as antioxidants in scavenging hydroxyl radicals, superoxide radicals, and DPPH radicals, with an antioxidant addition amount of 0.2–1.0 g / L.

[0017] The aforementioned phenolic acids are used as corrosion inhibitors in acidic solution environments during steel pickling and oil and gas acidizing.

[0018] Furthermore, the pickling corrosion inhibitor also includes potassium iodide, and the mass ratio of phenolic acid substances to potassium iodide is 1:1.

[0019] The aforementioned application of polysaccharides as a carbon source for microorganisms.

[0020] Furthermore, the microorganism is a denitrifying bacterium.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention uses wastewater from soaking grains in Sichuan-style sorghum liquor as raw material. After preparing a wastewater concentrate through steps such as vacuum filtration and vacuum distillation, three organic substances are separated from the wastewater concentrate by adjusting pH to precipitate acid-soluble substances, separating phenolic acids by adsorption with macroporous resin, and precipitating polysaccharides with ethanol. The entire process does not generate wastewater. The distilled water obtained by vacuum distillation can be reused or simply treated to meet discharge standards, thus realizing the resource utilization and near-zero discharge of wastewater from soaking grains in Sichuan-style sorghum liquor.

[0023] 2. The acid-soluble substances, phenolic acids and polysaccharides separated from the grain soaking wastewater by this invention can be used as antioxidants, and the polysaccharides can also be used as a carbon source in the solution for culturing denitrifying bacteria. This realizes the resource utilization of grain soaking wastewater from Sichuan-style sorghum liquor making, generates high added value, avoids environmental pollution and resource waste, and realizes a process of turning waste into treasure.

[0024] Furthermore, the separated phenolic acids can be used as corrosion inhibitors. These inhibitors require low dosage, have excellent corrosion inhibition effects, and achieve an inhibition efficiency of over 93%. When combined with KI, their corrosion inhibition performance is significantly improved, reaching 98%. The development of these high-value-added products not only enhances the resource utilization value of grain-soaking wastewater but also brings significant economic benefits to enterprises in the second phase, promoting the sustainable development of liquor companies.

[0025] 3. This invention achieves the effective separation and utilization of different types of organic matter in grain soaking wastewater through simple physicochemical methods. The method is simple and easy to implement, and is easy to apply in industrial production, and has broad application value. Attached Figure Description

[0026] Figure 1 Roadmap for the separation and application of organic matter in wastewater from sorghum liquor brewing in Sichuan.

[0027] Figure 2 The effect of sample solution pH on the adsorption of macroporous resin.

[0028] Figure 3 The effect of eluent concentration on desorption.

[0029] Figure 4 The effect of sample volume on the adsorption of macroporous resin.

[0030] Figure 5 The effect of the amount of water used for impurity removal on the impurity removal effect.

[0031] Figure 6 Dynamic elution curve.

[0032] Figure 7 Different separated components of grain soaking wastewater affect ·OH - Free radical scavenging ability.

[0033] Figure 8 Different separated components of grain soaking wastewater affect O2 - Free radical scavenging ability.

[0034] Figure 9 The scavenging ability of different fractions from grain soaking wastewater on ·DPPH free radicals.

[0035] Figure 10 The effect of solution TN content on TN and COD Cr The impact of clearance rate.

[0036] Figure 11 COD of solution Cr Content of TN and COD Cr The impact of clearance rate.

[0037] Figure 12 The effect of solution pH on TN and COD Cr The impact of clearance rate.

[0038] Figure 13 The effect of different carbon sources on TN and COD Cr The clearance rate.

[0039] Figure 14 Polarization curves of carbon steel in 0.5M H2SO4 solutions containing different concentrations of phenolic acids at 30℃.

[0040] Figure 15 (a) Nyquist plot and (b) Bode plot of carbon steel in 0.5M H2SO4 solution containing different concentrations of phenolic acids at 30℃.

[0041] Figure 16 Polarization curves of carbon steel in 0.5M H2SO4 solutions containing different concentrations of phenolic acid-KI at 30℃.

[0042] Figure 17(a) Nyquist plot and (b) Bode plot of carbon steel in 0.5M H2SO4 solution containing different concentrations of phenolic acid-KI at 30℃.

[0043] Figure 18 At 30℃, carbon steel (a) did not participate in corrosion, (b) contained no corrosion, and (c) contained 1.5 g·L⁻¹. -1 SEM image of phenolic acid-KI after soaking in 0.5M H2SO4 solution for 4 hours.

[0044] Figure 19 Carbon steel at 30℃: (a) uncorroded, (b) free of corrosion, and (c) containing 1.5 g·L⁻¹. -1 AFM image of phenolic acid-KI after soaking in 0.5M H2SO4 solution for 4 hours.

[0045] Figure 20 Carbon steel at 30℃: (a) uncorroded, (b) free of corrosion, and (c) containing 1.5 g·L⁻¹. -1 Three-dimensional profile of phenolic acid-KI after soaking in 0.5M H2SO4 solution for 4 hours. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0047] Unless otherwise specified, the experimental methods used in the following examples are all routine procedures, and the reagents used are commercially available. The grain soaking wastewater used in the following examples is the grain soaking wastewater of Sichuan-style sorghum liquor, taken from Luzhou Zuiqingfeng Liquor Co., Ltd.

[0048] I. Technology for separating organic matter from wastewater used in brewing Sichuan sorghum liquor and utilizing it for resource recovery

[0049] Example

[0050] 1) Wastewater samples from the soaking of grains in Sichuan sorghum liquor were filtered under reduced pressure to remove large insoluble particles such as rice husks, wheat bran, and broken grain particles. The water was then recovered by reduced pressure distillation, and the wastewater concentrate containing a large amount of organic matter was collected as raw material for extracting organic matter.

[0051] 2) After adjusting the pH of the collected wastewater concentrate to 8.0 with 0.5M NaOH solution, let it stand at 4℃ for 12 hours to allow complete precipitation, and then centrifuge the precipitate (8000 r·min). -1 (10 min), which is the acid-soluble substance and the supernatant obtained by separation.

[0052] 3) After centrifugation to remove acid-soluble substances, the supernatant obtained is collected and separated by adsorption of phenolic acids using DM301 macroporous resin. The separation conditions are as follows: wastewater sample pH 5.0 (adjusted to 5.0 using 0.5M NaOH); 80% ethanol as eluent; resin adsorption capacity 3 BV; amount of purified water 3 BV; amount of eluent 3 BV. The eluent is collected and distilled under reduced pressure, yielding the separated phenolic acids and polysaccharide-rich purified water.

[0053] 4) After removing small amounts of protein from the polysaccharide-rich water using Sevage's reagent (chloroform: n-butanol = 4:1), the water was concentrated to a viscous state by vacuum distillation. An 80% ethanol solution was then added (the mass-to-volume ratio of the concentrated viscous solution to the 80% ethanol solution was 1 g: 10 mL). The mixture was ultrasonically agitated for 30 min, allowed to stand at 4°C for 12 h, and then centrifuged to collect the precipitate (8000 r·min). -1 (10 min), which is the polysaccharide obtained by separation.

[0054] Throughout the process, water is recycled and ethanol is reused without generating new waste liquid, thus achieving resource utilization and zero-discharge treatment of wastewater from soaking grains in Sichuan-style sorghum liquor.

[0055] 1. The acid-soluble substances separated from the wastewater of Sichuan sorghum liquor soaking in this embodiment were analyzed by HPLC-MS, and the results are shown in Table 1.

[0056] The results showed that palmitic acid, oleic acid amide, and stearamide accounted for the highest proportion of the acid-soluble substances separated from the grain soaking wastewater, totaling 65.68%. These three substances contain long-chain fatty acids, which explains their poor water solubility. It can be seen that amides and nitrogen-containing alkaloids such as 1-deoxymethylsphingosine, choline, and L-valine are the main components of the acid-soluble substances, explaining their acid solubility but insolubility under weakly alkaline conditions. The precipitation of methyl [3,4,5-trihydroxyoxacyclohexane-2-yl]3,4,5-trihydroxybenzoate is partly due to its poor water solubility and partly due to the synergistic solubilizing effect of natural substances. 6-Gingerol may dissolve in water in acidic media due to protonation, but precipitates under weakly alkaline conditions because it cannot be protonated.

[0057] Table 1. Composition and relative content of acid-soluble substances

[0058]

[0059] 2. The phenolic acid substances separated from the wastewater of Sichuan sorghum liquor soaking in this embodiment were analyzed by HPLC-MS, and the results are shown in Table 2.

[0060] Table 2. Components and relative contents of phenolic acids

[0061]

[0062] The results showed that among the phenolic acids separated from the grain soaking wastewater, phenylalanine, 3,4-dihydroxyphenylpropionic acid and 3-phenyllactic acid accounted for the largest proportions, with a combined proportion of about 45% of the organic matter, and were the main components of the separated organic matter.

[0063] 3. The polysaccharides separated from the wastewater of Sichuan sorghum liquor soaking in this embodiment were analyzed by Thermo ICS5000+ ion chromatography, and the results are shown in Table 3.

[0064] Table 3. Components and relative contents of polysaccharides

[0065]

[0066] The results showed that the polysaccharides separated from the grain soaking wastewater were mainly composed of three monosaccharides: fructose, galactose, and glucose. Among them, fructose accounted for the largest proportion, reaching 64.04%, and was the most abundant organic compound in the wastewater polysaccharides.

[0067] II. Process Evaluation of Macroporous Resin Adsorption and Separation of Phenolic Acids

[0068] 1. Different types of macroporous resins exhibit varying separation effects on different substances due to differences in specific surface area, pore size, and polarity. Table 4 shows the static adsorption and desorption rates of phenolic acids in wastewater for 18 different types of macroporous resins commonly used for separating phenolic acids.

[0069] Table 4. Adsorption and desorption rates of phenolic acids in wastewater by different resins

[0070]

[0071] As can be seen from Table 4, a high adsorption rate does not necessarily mean a high desorption rate for macroporous resins. In order to maximize the extraction and separation of phenolic acids from wastewater, this study screened 18 resins based on the product of adsorption rate and desorption rate. Among them, DM301 resin showed the highest product of adsorption rate and desorption rate for phenolic acids in wastewater. Therefore, DM301 macroporous resin was selected as the purification resin for phenolic acids in grain soaking wastewater.

[0072] 2. The effect of sample solution pH on the adsorption of DM301 macroporous resin, such as Figure 2As shown, the adsorption capacity of DM301 macroporous resin for phenolic acids in wastewater first increases and then decreases with increasing pH, reaching its maximum at pH 5.0. The hydroxyl groups in phenolic acids give them weak acidity; at higher pH levels, they easily lose hydrogen ions to become negative ions, making them difficult for macroporous resins to adsorb. At lower pH levels, they can be protonated, reducing their adsorption capacity. Only under appropriate pH conditions do phenolic acids in grain-soaking wastewater exist primarily in molecular form, making them easily adsorbed by macroporous resins. Therefore, when using DM301 macroporous resin to separate phenolic acids from wastewater, the pH of the grain-soaking wastewater should be adjusted to 5.0.

[0073] 3. The effect of eluent concentration on the desorption rate of macroporous resin, such as Figure 3 As shown, in low-concentration ethanol solutions, the desorption capacity of macroporous resins increases with increasing ethanol mass fraction, reaching a maximum at 80% ethanol. Further increases in ethanol concentration decrease the desorption capacity. Phenolic acids interact with the macroporous resin surface through hydrogen bonds or hydrophobic interactions. Increasing the ethanol concentration in the eluent favors the elution of phenolic acids, thus increasing the ethanol concentration increases desorption. However, high ethanol concentrations cause impurities adsorbed in the macroporous resin to flow out with the eluent, reducing the desorption of the target substance and hindering separation and purification.

[0074] 4. The effect of sample volume on the adsorption of macroporous resin, such as Figure 4 As shown, the concentration of phenolic acids in the effluent increases with the increase of the sample volume. When the volume of added wastewater reaches 90 mL, the concentration of phenolic acids in the effluent is basically the same as that in the filtrate (5.19 mg / mL). -1 The same concentration of phenolic acids in the effluent indicates that the resin adsorption has reached saturation. To ensure sufficient adsorption by the macroporous resin while maintaining extraction and separation efficiency, the leakage point is chosen when the concentration of phenolic acids in the effluent is 1 / 4 of the injection concentration. This means that 30 mL of wastewater is considered the adsorption capacity of 10 mL of macroporous resin. Therefore, when using DM301 macroporous resin to adsorb phenolic acids from the filtrate, the optimal adsorption capacity of the resin is 3 BV, meaning the sample volume is three times the total volume of the resin packed in the chromatography column.

[0075] 5. The effect of the amount of water used for impurity removal on the impurity removal effect, such as Figure 5 As shown. Polysaccharides, as the most abundant organic substance in grain soaking wastewater, are the main substance removed from the rinsing water during impurity removal. Figure 5It can be seen that with the addition of deionized water, the polysaccharide content in the effluent decreased sharply, indicating that the DM301 resin is effective in separating phenolic acids and polysaccharides from wastewater. When the amount of deionized water reached 30 mL, further addition resulted in almost no change in the polysaccharide content in the effluent, suggesting that the polysaccharide impurities in the resin pores had been eluted and removed. Therefore, 30 mL of deionized water was chosen as the optimized amount of deionized water (3 BV) after 10 mL of resin adsorption was completed.

[0076] 6. With the addition of eluent, the concentration of phenolic acids in the effluent changes as follows: Figure 6 As shown, with the addition of 80% ethanol, the phenolic acids adsorbed on the macroporous resin are desorbed and elute with the eluent. The content of phenolic acids reaches its maximum when the eluent volume is 10 mL. After adding more eluent to 30 mL, the content of phenolic acids in the eluent reaches its minimum and tends to stabilize. Subsequent additions of eluent do not significantly change the content of phenolic acids in the eluent. Therefore, 30 mL of 80% ethanol is chosen as the eluent volume after the 10 mL resin adsorption is complete, i.e., 3 BV.

[0077] III. Performance Study of Antioxidants

[0078] 1. Evaluation of the antioxidant's ability to scavenge ·OH

[0079] The ability of the isolated organic matter to scavenge ·OH was determined by colorimetric method using reagents from Nanjing Jiancheng Bioengineering Institute. The ·OH scavenging rate was calculated using the following formula.

[0080]

[0081] In the formula: A 对照 A 空白 A 测定 These correspond to the control tube, blank tube, and absorbance of the sample to be measured, respectively.

[0082] The experimental results of the removal of ·OH by three organic compounds separated from wastewater at different concentrations are shown in the figure. Figure 7 Depend on. Figure 7 It can be seen that the acid-soluble substances in grain soaking wastewater have an excellent effect on scavenging hydroxyl radicals, at a concentration of 0.4 g·L⁻¹. -1 The scavenging rate reached as high as 99% at the minimum addition concentration; the isolated polysaccharide also exhibited highly efficient hydroxyl radical scavenging ability at 0.8 g·L⁻¹. -1 At the added amount, the scavenging rate reached over 90%; the separated phenolic acids also had a certain hydroxyl radical scavenging ability, but the effect was worse than that of the other two organic compounds, at 0.9 g·L⁻¹. -1 The clearance rate at the maximum additive concentration was 48.7%.

[0083] 2. Antioxidant scavenging O2 - Ability Assessment

[0084] Separate organic matter and remove O2 - The ability to determine O2 was performed using a colorimetric method with reagents from the Nanjing Jiancheng Biotechnology Institute. - The clearance rate is calculated using the following formula.

[0085]

[0086] In the formula: A 对照 A 测定 A 标准 The absorbance of the corresponding samples was measured.

[0087] Three organic compounds were isolated from grain soaking wastewater. - The ability to clear such as Figure 8 As shown, all three isolates exhibit a certain scavenging ability against superoxide radicals. The scavenging ability of the acid-soluble isolate is directly proportional to its concentration, increasing with increasing concentration. At 1.0 g·L⁻¹, the scavenging ability reaches a certain level. -1 At the added concentration, the scavenging rate reached 31.4%. The scavenging ability of the other two isolates against superoxide radicals decreased with increasing concentration.

[0088] 3. Evaluation of antioxidant DPPH scavenging capacity

[0089] The ability of the isolated organic matter to scavenge ·DPPH was determined by colorimetric method using reagents from Nanjing Jiancheng Bioengineering Institute. The ·DPPH scavenging rate was calculated using the following formula.

[0090] DPPH free radical scavenging rate (%) = (1-(A) 测定 -A 对照 )÷A 空白 )×100 (1-3)

[0091] In the formula: A 对照 A 测定 A 标准 The absorbance of the corresponding samples was measured.

[0092] The removal capabilities of three organic compounds isolated from grain soaking wastewater for ·DPPH are as follows: Figure 9 As shown. By Figure 9 It is evident that phenolic acids exhibit excellent scavenging effects on DPPH free radicals, and the scavenging capacity is directly proportional to the concentration added. At 1.0 g·L⁻¹, the scavenging effect is significantly higher. -1At the maximum scavenging concentration, the scavenging rate reached as high as 98.7%. The other two organic compounds were also effective in scavenging DPPH free radicals. At the maximum scavenging concentration, their scavenging rates were only 22.7% and 46.2%, respectively, which were far lower than those of phenolic acids.

[0093] IV. Performance Study of Polysaccharides as Microbial Carbon Sources

[0094] 1. The total nitrogen (TN) concentration in solution affects the metabolism and growth of microorganisms. Appropriately increasing the TN concentration usually promotes the activity of denitrifying bacteria and accelerates the denitrification rate. However, excessively high TN concentrations may have an inhibitory effect, affecting bacterial growth and metabolism. Different TN concentrations have varying effects on microorganisms in solution, in addition to TN and COD. Cr See the impact Figure 10 .Depend on Figure 10 It can be seen that the removal rate of TN by microorganisms in solution is inversely proportional to the TN concentration, and the removal rate of COD is also inversely proportional to the TN concentration. Cr The removal rate showed a trend of first increasing and then decreasing with increasing TN concentration. To ensure high removal efficiency, 14.5 ppm was selected as the optimal TN concentration for the solution.

[0095] 2. Chemical oxygen demand (COD) reflects the content of organic matter in the solution. The denitrification process of denitrifying bacteria requires organic carbon as an electron donor. An appropriate amount of COD... Cr It can provide sufficient carbon source for denitrifying bacteria, promote their growth and metabolism, and improve denitrification efficiency; while excessive COD Cr This could lead to the proliferation of other heterotrophic microorganisms, which would compete with denitrifying bacteria for resources, thereby inhibiting the denitrification process. Different COD levels... Cr To remove TN and COD from microorganisms in solution Cr The impact such as Figure 11 As shown. From Figure 11 It can be observed that, with the increase of COD in the solution... Cr The increase in microorganisms affects TN and COD Cr The removal rate also increased, reaching maximum values ​​of 67.2% and 10.5% at 800 ppm and 600 ppm, respectively. To ensure high removal efficiency, COD was selected. Cr COD of 800 ppm as the solution optimization Cr concentration.

[0096] 3. The optimal pH range for denitrifying bacteria is typically 6.5-8.5. Within this range, denitrifying enzyme activity is highest, and denitrification efficiency is optimal. However, the optimal pH may vary depending on the operating environment. To investigate the optimal pH of the solution when wastewater polysaccharides are added as a carbon source, the following study was conducted, and the results are as follows: Figure 12As shown, the removal rate of TN by microorganisms was highest at a solution pH of 7.0, reaching 53.8%. This indicates that denitrifying bacteria have strong growth and metabolic activity in solutions with this pH, therefore pH 7.0 was chosen as the optimal pH for the solution.

[0097] 4. When glucose, sucrose, and polysaccharides from grain soaking wastewater are used as carbon sources, respectively, what are the effects of microorganisms on total nitrogen (TN) and total oxygen (COD)? Cr clearance rate such as Figure 13 As shown in the figure. Comparison revealed that after wastewater polysaccharides were added as a carbon source, the microorganisms' response to total nitrogen (TN) and total oxygen (COD) was improved. Cr The removal rate of polysaccharides was superior to that of glucose and sucrose alone as carbon sources, with the removal rate of total nitrogen (TN) being particularly outstanding. The excellent TN removal rate indicates that the denitrifying bacteria in the solution have strong biological activity and can grow and metabolize more quickly, proving that the polysaccharides isolated from grain soaking wastewater have the potential to serve as a carbon source for denitrifying bacteria.

[0098] V. Performance Study of Phenolic Acids as Corrosion Inhibitors

[0099] 1. Place the carbon steel electrode in a 0.5M H2SO4 solution and add phenolic acid substances (corrosion inhibitor 1) prepared in different concentrations as described in the examples, and obtain the potentiodynamic polarization curves, as shown below. Figure 14 As shown in the figure. It can be seen that after adding phenolic acids, the corrosion current density (i) of carbon steel... corr The current density of the cathodic polarization curve decreased significantly, but the overall characteristics of the polarization curve remained unchanged. This indicates that the corrosion-inhibiting molecules in the phenolic acid substances reduce the contact between the carbon steel and the corrosive medium H2SO4 by blocking the active sites on the carbon steel surface, thereby delaying the corrosion of the carbon steel. The blocking of active sites may be attributed to the adsorption of the effective corrosion-inhibiting components in the phenolic acid substances on the carbon steel surface. Simultaneously, it was observed that the addition of phenolic acid substances shifted the cathodic polarization curve to a lower current density, while the anodic polarization curve remained almost unchanged. This suggests that the organic compounds in the phenolic acid substances have little effect on the anodic dissolution of carbon steel in 0.5M H2SO4 solution, but largely inhibit the cathodic hydrogen evolution reaction. Therefore, it can be inferred that phenolic acid substances in the 0.5M H2SO4 corrosive environment are a mixed corrosion inhibitor that primarily inhibits cathodic corrosion of carbon steel.

[0100] The formula for calculating the corrosion suppression efficiency (η) based on polarization data is as follows:

[0101]

[0102] In the formula: i corr and i' corr These represent the corrosion current densities with and without different concentrations of corrosion inhibitors.

[0103] Table 5 presents the electrochemical polarization parameters obtained by Tafel extrapolation and the calculated corrosion inhibition efficiency. By comparing i corr The size reveals that the addition of phenolic acids increases the carbon steel's... corr The significant reduction demonstrates the effectiveness of phenolic acids as corrosion inhibitors in 0.5M H₂SO₄ solution. Furthermore, the corrosion potential (E) decreased significantly. corr The value of E shifts negatively with increasing concentration of phenolic acids, indicating that phenolic acids have a more significant effect on the cathode reaction. This is compared to the blank solution. corr The change in voltage was less than 0.085V, further demonstrating that phenolic acids are a mixed corrosion inhibitor primarily responsible for suppressing cathodic reactions. It is noteworthy that with the addition of phenolic acids, the Tafel slope (β) of the cathode... c ) and the Tafel slope (β) of the anode a The change in the phenolic acid value was not significant, indicating that phenolic acids have little effect on the reaction mechanism of carbon steel in 0.5M H2SO4 solution. At the maximum addition concentration, phenolic acids can inhibit the corrosion of carbon steel in sulfuric acid solution by up to 93.03%, making them an excellent corrosion inhibitor.

[0104] 2. Place the carbon steel electrode in a 0.5M H2SO4 solution and add phenolic acid substances (corrosion inhibitor 1) prepared in different concentrations as described in the examples to obtain impedance spectra, such as... Figure 15 As shown, with the addition of phenolic acids, the diameter of the capacitive arc in the Nyquist plot significantly increases, indicating that the corrosion of carbon steel in 0.5M H2SO4 solution is inhibited. Bode analysis reveals that the impedance modulus increases with increasing phenolic acid concentration, suggesting that higher concentrations of phenolic acids provide stronger protection for carbon steel. Furthermore, the shape of the capacitive arc does not change after the addition of phenolic acids, indicating that the addition of phenolic acids does not alter the corrosion reaction mechanism of carbon steel in 0.5M H2SO4 solution. The capacitive arc appears as a flattened semicircle, rather than a perfect semicircle, due to the irregularity and non-uniformity of the solid electrode surface. It can be noted that the Nyquist plot is characterized by a capacitive arc in the high-frequency region and an inductive arc in the low-frequency region. The capacitive reactance in the high-frequency region corresponds to the charge transfer process of the electric double layer, while the inductive reactance in the low-frequency region is generally related to the relaxation process of the state variables on the electrode surface, implying that the corrosion inhibitor undergoes an adsorption process on the carbon steel surface. As the concentration of corrosion inhibitor increases, the induced arc also increases, reflecting that the induced arc is caused by the adsorption and desorption of the corrosion inhibitor. However, the induced arcs in the experiment are generally small and incomplete, which can easily lead to a large fitting error. Combining the characteristics of Bode plots, data in the mid-to-high frequency range are used... Figure 4-4 The equivalent circuit fitting impedance parameters are shown. Where R... s R represents the resistance of the solution.ct It represents charge transfer resistance. CPE stands for constant phase element, which is often used to replace ideal electrical components to account for non-uniformity.

[0105] The impedance of a CPE can be defined as:

[0106]

[0107] In the formula: Y0 is the size of CPE, n is the diffusion effect exponent, which is the micro-oscillation of the carbon steel surface, j represents the imaginary unit, and ω is the angular frequency. CPE can be an inductor with n = -1, a resistor with n = zero, a Warburg impedance with n = 0.5, or a capacitor with n = 1.

[0108] EIS was fitted using ZSimpWin software, and the corresponding corrosion inhibition efficiency (η) was calculated using the following formula.

[93] as follows:

[0109]

[0110] In the formula: R ct and R' ct It is a charge transfer resistor containing and without different concentrations of SOW.

[0111] Table 6 presents the impedance fitting parameters of carbon steel in 0.5M H2SO4 solutions with different concentrations of phenolic acids at different temperatures. The relatively small chi-square (χ2) values, reflecting the reliability of the fitting results, indicate that the equivalent circuit used is reasonable. The table shows that the corrosion inhibition efficiency of phenolic acids on carbon steel increases significantly with increasing concentration, reaching 93.24% at the maximum concentration, similar to the polarization test results. Furthermore, the fitted value of CPE gradually decreases with increasing phenolic acid concentration, indicating that the effective components of the phenolic acids are adsorbed on the surface of the carbon steel, and the thickness of the adsorbed film increases with increasing concentration.

[0112] 3. Place the carbon steel electrode in a 0.5M H2SO4 solution and add a composite corrosion inhibitor (corrosion inhibitor 2) composed of phenolic acid substances and KI in equal proportions prepared in different concentrations from the examples. Obtain the potentiodynamic polarization curve, as shown below. Figure 16 As shown in the figure, phenolic acid-KI, when added as a corrosion inhibitor, can significantly reduce the cathodic corrosion current density of carbon steel in corrosive media at low concentrations. With increasing concentration, it can also effectively reduce the anodic corrosion current density and inhibit the anodic dissolution reaction of carbon steel, indicating that the phenolic acids separated from grain-soaking wastewater, when combined with KI, are a highly efficient corrosion inhibitor. The polarization parameters fitted using the Tafel extrapolation method are listed in Table 5. The corrosion inhibition efficiency of phenolic acid-KI on carbon steel can reach 98.95% at the maximum concentration, making it an extremely excellent corrosion inhibitor.

[0113] 4. Place the carbon steel electrode in a 0.5M H2SO4 solution and add a composite corrosion inhibitor (corrosion inhibitor 2) composed of phenolic acid substances and KI in equal proportions prepared in different concentrations from the examples. Obtain the dynamic impedance spectrum, as shown below. Figure 17 As shown.

[0114] When phenolic acid-KI substances are added as corrosion inhibitors, the capacitive arc radius increases significantly even at low concentrations, and this increase continues with increasing concentration, indicating that phenolic acid-KI has a good corrosion inhibition effect. The electrochemical impedance parameters fitted by the R(QR) equivalent circuit are listed in Table 6. At the maximum concentration, the corrosion inhibition efficiency of phenolic acid-KI on carbon steel reaches 98.48%, similar to the polarization test results, proving the excellent corrosion inhibition effect of phenolic acid-KI. Furthermore, a comparison was made with the addition of 1.0 g·L⁻¹... -1 and 1.5 g·L -1 R of phenolic acids ct And from η, we know that 1.5 g·L -1 The addition of phenolic acid-KI significantly enhances the inhibitory effect on carbon steel corrosion. This may be because at low concentrations, the corrosion inhibitor's adsorption capacity is insufficient to form a complete adsorption film on the carbon steel surface, leading to localized corrosion. However, as the concentration of the corrosion inhibitor increases, the number of adsorbed molecules increases, enhancing the continuity and density of the adsorption film, thus more effectively isolating the corrosive medium from contact with the metal.

[0115] Table 5. Polarization curve fitting parameters of carbon steel in 0.5M H₂SO₄ solution containing different types and concentrations of organic matter at 30℃

[0116]

[0117] Table 6. Impedance fitting parameters of carbon steel in 0.5M H2SO4 solution containing different types and concentrations of organic matter at 30℃

[0118]

[0119] 5. Weight loss experiment and surface morphology analysis of carbon steel in 0.5M H2SO4 solution with added phenolic acid-KI

[0120] Table 7 lists the corrosion rates of carbon steel in 0.5M H2SO4 solution and the calculated inhibition efficiencies after adding phenolic acids in combination with KI as corrosion inhibitors. Compared to the control group without corrosion inhibitors, the corrosion rate of carbon steel after adding phenolic acids-KI decreased from 40.63 g·m⁻¹. -2 ·h -1 It was reduced to 0.68 g·m -2 ·h-1 The corrosion inhibition efficiency reached an astonishing 98.33%, further demonstrating the excellent corrosion inhibition performance of the compound.

[0121] Table 7. Carbon steel at 30℃ with and without 1.5 g·L -1 Corrosion rate and corrosion inhibition efficiency of phenolic acid-KI in 0.5M H2SO4 solution

[0122]

[0123] Figure 18 (c) is for a solution containing 1.5 g·L -1 SEM images of phenolic acid-KI solution after soaking for 4 hours in 0.5M H2SO4 solution. Comparison with images without added phenolic acid-KI. Figure 18 Figure (b) shows that the addition of the corrosion inhibitor significantly reduced the corrosion rate of carbon steel in the corrosive medium, resulting in a smoother and more even surface without obvious corrosion pits. Furthermore, compared to the uncorroded steel... Figure 18 (a) It can be seen that the carbon steel surface with added corrosion inhibitor is similar to the carbon steel surface without corrosion, and only very slight corrosion occurred, which further proves that the phenolic acid substances in the grain soaking wastewater exhibit excellent corrosion inhibition performance after being compounded with KI.

[0124] Carbon steel containing 1.5 g·L -1 The AFM and three-dimensional profile images after soaking in 0.5M H2SO4 solution of phenolic acid-KI for 4 hours are shown below. Figure 19 and Figure 20 As shown in the figure. Comparing figures (b) and (c), it can be seen that after adding phenolic acid-KI to the corrosive medium, the carbon steel surface is smoother than the carbon steel surface without any corrosion inhibitor, and is almost the same as the carbon steel surface that has not participated in corrosion. The calculated R a and S a The corrosion rate was also much lower than that of the sample without corrosion inhibitor, indicating that the compound has an excellent inhibitory effect on the corrosion of carbon steel in 0.5M H2SO4 solution.

[0125] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for the resource utilization of grain soaking wastewater, characterized in that, Specifically, the following steps are included: (1) Remove suspended matter from the grain soaking wastewater, and then concentrate the wastewater by vacuum distillation to obtain wastewater concentrate; (2) Adjust the pH of the wastewater concentrate to 8.0, then let it stand at 4~10℃ to precipitate the precipitate, then centrifuge to separate the acid-soluble matter, and collect the supernatant for later use; (3) Use macroporous resin to adsorb and separate phenolic acid substances in the supernatant, collect the eluent and distill under reduced pressure to obtain phenolic acid substances, and collect the polysaccharide-rich purified water for later use; (4) Use Sevage reagent to remove the protein in the impurity-removed water in step (3), then concentrate it into a viscous liquid by vacuum distillation, then add 80% ethanol solution, sonicate for 15~30 min, let it stand at 4~10℃ to precipitate, and then centrifuge to obtain polysaccharide. The mass-volume ratio of the viscous liquid to the 80% ethanol solution is 1g: 5~15mL.

2. The method for resource utilization of grain soaking wastewater according to claim 1, characterized in that, In step (2), the pH is adjusted using a 0.5M sodium hydroxide solution.

3. The method for resource utilization of grain soaking wastewater according to claim 1, characterized in that, In step (3), the macroporous resin is DM301 type macroporous resin.

4. A method for resource utilization of grain soaking wastewater according to claim 1 or 3, characterized in that, The adsorption separation conditions were as follows: the pH of the supernatant was adjusted to 4.0-7.0 using 0.5M NaOH; 80% ethanol was used as the eluent; the adsorption capacity of the resin was 3 BV; the amount of impurity removal water was 3 BV; and the amount of eluent was 3 BV.

5. The method for resource utilization of grain soaking wastewater according to claim 1, characterized in that, The Sevage reagent is a mixture of chloroform and n-butanol in a volume ratio of 4:

1.

6. The application of acid-soluble substances, phenolic substances or polysaccharides obtained by the method for resource utilization of grain soaking wastewater according to claim 1 as antioxidants in scavenging hydroxyl radicals, superoxide radicals and DPPH radicals, wherein the amount of antioxidant added is 0.2~1.0 g / L.

7. The application of phenolic acid substances obtained by the method for resource utilization of grain soaking wastewater as described in claim 1 as corrosion inhibitors in acidic solution environments of steel pickling and oil and gas acidizing extraction.

8. The application of the phenolic acid substances according to claim 7 as pickling corrosion inhibitors in acidic solution environments for steel pickling and oil and gas acidizing extraction, characterized in that, The pickling corrosion inhibitor also includes potassium iodide, and the mass ratio of phenolic acid substances to potassium iodide is 1:

1.

9. The application of the polysaccharide obtained by the method for resource utilization of grain soaking wastewater as described in claim 1 as a microbial carbon source.

10. The application of the polysaccharide as a microbial carbon source according to claim 9, characterized in that, The microorganisms are denitrifying bacteria.

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