Method for resource utilization of grain soaking wastewater and application of recycled material of grain soaking wastewater

Abstract

The invention discloses a grain soaking wastewater resource utilization method and application of recovered substances thereof, and the method specifically comprises the following steps: (1) removing suspended substances in grain soaking wastewater, and then carrying out reduced pressure distillation and concentration to obtain a wastewater concentrated solution; (2) adjusting the pH value of the wastewater concentrated solution to 8.0, then standing to separate out a precipitate, then carrying out centrifugal separation to obtain an acid-soluble substance, and collecting a supernatant for later use; (3) carrying out adsorption separation on phenolic acid substances in the supernatant by adopting macroporous resin, collecting an eluent, carrying out reduced pressure distillation to obtain the phenolic acid substances, and collecting polysaccharide-rich impurity-removed water for later use; and (4) removing protein in the impurity-removed water in the step (3) by using a Sevage reagent, carrying out reduced pressure distillation and concentration to a viscous state, then adding an 80% ethanol solution, carrying out ultrasonic oscillation for 30 minutes, standing to separate out a precipitate, and carrying out centrifugal separation to obtain the polysaccharide. According to the method, acid-soluble substances, phenolic acid substances and polysaccharide can be separated and recycled from the grain soaking wastewater, resource utilization of the grain soaking wastewater is achieved, and carbon emission is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recycling and utilization, and particularly relates to a method for resource utilization of grain soaking wastewater and application of its recyclables. Background Art

[0002] Baijiu, a representative of traditional Chinese alcoholic beverages, boasts a long history and unique flavor. Baijiu, a unique distilled spirit in my country, is typically made from sorghum and other grains. It retains traditional production techniques, combining crushing and fermentation of the raw materials with distillation, storage, and blending. The production, storage, and aging of baijiu generate significant amounts of industrial wastewater. Boiler water, yellow water, and grain soaking water, among other processes, contain significant amounts of organic matter and are a major cause of environmental pollution. According to incomplete statistics, baijiu distilleries discharge 12 to 20 tons of industrial wastewater for every ton of baijiu produced, making the alcohol production industry the industry with the highest concentration of organic pollutants. High-concentration organic wastewater from distillery operations contains significant amounts of organic matter and suspended solids, as well as high levels of total nitrogen, total phosphorus, chemical oxygen demand, and biological oxygen demand. Direct discharge into rivers can cause severe eutrophication and environmental pollution.

[0003] As China's largest baijiu production base, Sichuan accounts for over 40% of the national total, earning it the reputation of "the best Sichuan liquor in the world." Xiaoqu liquor, a major baijiu variety, accounts for approximately 30% of annual production. With a long history, unique flavor, high production volume, and widespread influence, it is a crucial component of Sichuan liquor's strengths. Sorghum, the primary raw material for xiaoqu liquor, has long been known as the "essence of the five grains" and the "chief of all grains." It is rich in functional ingredients such as soluble polysaccharides, phenolic acids, and tannins. The soaking process in xiaoqu liquor production causes the sorghum to absorb water and swell, loosening the starch structure and creating conditions for steaming and gelatinization. The soaking wastewater produced by soaking contains a wealth of nutrients such as soluble polysaccharides, phenolic acids, tannins, and 3-deoxyanthocyanidins. Traditional wastewater treatment relies on biochemical degradation to meet discharge standards, which not only wastes the abundant organic matter but also increases the difficulty of wastewater treatment.

[0004] Recycling wastewater and extracting other resources and energy from it are crucial for optimizing water supply structures, increasing water resources, alleviating supply-demand imbalances, reducing water pollution, and ensuring aquatic ecological security. Therefore, providing a treatment approach that recycles resources and reduces carbon emissions while balancing environmental, social, and economic benefits will undoubtedly become the future direction of wastewater treatment in the liquor industry. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for resource utilization of grain soaking wastewater and the application of its recyclables. The present invention can separate and recover acid-soluble substances, phenolic acid substances and polysaccharides from grain soaking wastewater, thereby realizing resource utilization of grain soaking wastewater and reducing carbon emissions.

[0006] The technical solution of the present invention is achieved as follows:

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

[0008] (1) Remove the suspended matter in the grain soaking wastewater, and then distill and concentrate it by 5-10 times under reduced pressure to obtain a wastewater concentrate; here, the grain soaking wastewater is concentrated to enrich the organic matter in the grain soaking wastewater, and at the same time, it is easy to reduce the volume for easy storage.

[0009] (2) The pH value of the wastewater concentrate is adjusted to 8.0, and then the concentrate is allowed to stand at 4-10°C to precipitate, and then centrifuged to obtain the acid-soluble material, and the supernatant is collected for later use.

[0010] (3) Using macroporous resin to adsorb and separate phenolic acid substances in the supernatant, collecting the eluent and performing vacuum distillation to obtain phenolic acid substances, and collecting the decontaminated water rich in polysaccharides for later use.

[0011] (4) Using Sevage reagent to remove the protein in the impurity-removed water in step (3), the solution was concentrated by vacuum distillation to a viscous solution, and then an 80% ethanol solution was added. After ultrasonic vibration for 15 to 30 minutes, the solution was allowed to stand at 4 to 10° C. to precipitate, and then centrifuged to obtain polysaccharide, wherein the mass volume ratio of the viscous solution to the 80% ethanol solution was 1 g: 5 to 15 mL.

[0012] Furthermore, in step (2), 0.5 M sodium hydroxide solution is used to adjust the pH.

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

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

[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 acid substances or polysaccharides are used as antioxidants in scavenging hydroxyl free radicals, superoxide free radicals and DPPH free radicals, and the added amount of the antioxidant is 0.2-1.0 g / L.

[0017] The phenolic acids mentioned above are used as corrosion inhibitors in acidic solution environments of steel pickling and oil and gas acidification production.

[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 use of the polysaccharides described above as carbon sources for microorganisms.

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

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

[0022] 1. The present invention uses the wastewater from soaking grain in Sichuan-style kaoliang and small-qu liquor as raw material, prepares a wastewater concentrate through steps such as vacuum filtration and vacuum distillation, and then separates three organic substances from the wastewater concentrate by adjusting pH to precipitate acid-soluble substances, adsorbing and separating phenolic acids with macroporous resin, and precipitating polysaccharides with ethanol. The entire process does not generate waste liquid, and the distilled water obtained by decompression can be reused or simply treated and then discharged in compliance with discharge standards, thereby realizing resource utilization and near-zero emission of the wastewater from soaking grain in Sichuan-style kaoliang and small-qu liquor.

[0023] 2. The acid-soluble substances, phenolic acid substances and polysaccharides separated from the grain soaking wastewater of the present invention can be used as antioxidants, and the polysaccharides can also be used as a carbon source in the solution for culturing denitrifying bacteria, thereby realizing the resource utilization of the grain soaking wastewater of Sichuan-style sorghum Xiaoqu wine, generating high added value, avoiding environmental pollution and waste of resources, and realizing a process of turning waste into treasure.

[0024] Furthermore, the isolated phenolic acids can be used as corrosion inhibitors. These inhibitors offer excellent corrosion inhibition at low dosages, achieving efficiency exceeding 93%. When compounded with KI, this performance is significantly improved, reaching 98%. The development of these high-value-added products not only increases the resource utilization of grain-soaking wastewater, but also, in the second phase, will generate significant economic benefits for the company and promote the sustainable development of the liquor industry.

[0025] 3. The present invention realizes the effective separation and utilization of different types of organic matter in grain soaking wastewater through simple physical and chemical methods. The method is simple and easy to implement, easy to apply in industrial production, and has wide promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Roadmap for separation and application of organic matter in grain soaking wastewater from Sichuan-style sorghum liquor production.

[0027] Figure 2 Effect of sample solution pH on adsorption of macroporous resin.

[0028] Figure 3 Effect of eluent concentration on desorption.

[0029] Figure 4 Effect of sample volume on adsorption of macroporous resin.

[0030] Figure 5 The influence of the amount of decontamination water on the decontamination effect.

[0031] Figure 6 Dynamic elution curve.

[0032] Figure 7 Effect of different fractions from grain soaking wastewater on ·OH - Free radical scavenging ability.

[0033] Figure 8 Effects of different fractions from grain soaking wastewater on O2 - Free radical scavenging ability.

[0034] Figure 9 Scavenging ability of different isolates from grain soaking wastewater on DPPH free radicals.

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

[0036] Figure 11 Solution COD Cr Effect of TN and COD content Cr Effect of clearance rate.

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

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

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

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

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

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

[0043] Figure 18 Carbon steel at 30℃ (a) not involved in corrosion, (b) without corrosion, and (c) with corrosion of 1.5g·L -1 SEM image of phenolic acid-KI after immersion in 0.5MH2SO4 solution for 4 hours.

[0044] Figure 19 Carbon steel at 30℃ (a) uncorroded, (b) free, and (c) containing 1.5g·L -1 AFM image of phenolic acid-KI after immersion in 0.5MH2SO4 solution for 4h.

[0045] Figure 20 Carbon steel at 30℃ (a) uncorroded, (b) free, and (c) containing 1.5g·L -1 Three-dimensional contour map of phenolic acid-KI after immersion in 0.5MH2SO4 solution for 4 hours. DETAILED DESCRIPTION

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

[0047] Unless otherwise specified, the experimental methods in the following examples are conventional operations, and the reagents used are commercially available. The grain soaking wastewater used in the following examples is Sichuan-style sorghum xiaoqu wine soaking wastewater, which is obtained from Luzhou Zuiqingfeng Wine Co., Ltd.

[0048] 1. Technology for separating organic matter from grain soaking wastewater from Sichuan-style sorghum liquor production for resource utilization

[0049] Example

[0050] 1) The wastewater sample of Sichuan-style sorghum liquor soaking grain was filtered by vacuum filtration to remove large particles of insoluble solid suspended matter such as husks, wheat bran, and broken grain particles in the water. The water was then recovered by vacuum distillation, and the wastewater concentrate containing a large amount of organic matter was collected as the raw material for extracting organic matter.

[0051] 2) After adding 0.5M NaOH solution to the collected wastewater concentrate to adjust the pH value to 8.0, it was left to stand at 4°C for 12 hours to allow the precipitate to completely separate, and then centrifuged (8000 r·min -1 , 10min), that is, the acid-soluble material and the supernatant were separated.

[0052] 3) After centrifugation to remove the acid-soluble material, the supernatant was collected and subjected to adsorption separation of phenolic acids using a DM301 macroporous resin. The separation conditions were as follows: the wastewater sample pH was 5.0 (the pH of the supernatant was adjusted to 5.0 using 0.5 M NaOH); 80% ethanol was used as the eluent; the resin adsorption capacity was 3 BV; the amount of decontamination water was 3 BV; and the amount of eluent was 3 BV. The eluent was collected and subjected to vacuum distillation to separate the phenolic acids and the decontamination water rich in polysaccharides.

[0053] 4) The polysaccharide-rich impurity-free water was treated with Sevage reagent (chloroform: n-butanol = 4:1) to remove a small amount of protein, and then concentrated to a viscous state by vacuum distillation. 80% ethanol solution was added (the mass volume ratio of the viscous concentrate to the 80% ethanol solution was 1 g: 10 mL), ultrasonically shaken for 30 min, and allowed to stand at 4°C for 12 h. The precipitate was collected by centrifugation (8000 r / min) -1 , 10min), which is the separated polysaccharide.

[0054] During the entire process, water is recycled and ethanol is reused, and no new waste liquid is generated, thus achieving resource utilization and zero-emission treatment of the wastewater from soaking grain in Sichuan-style sorghum liquor.

[0055] 1. The acid-soluble matter separated from the grain soaking wastewater of Sichuan-style kaoliang Xiaoqu wine in this embodiment was subjected to HPLC-MS detection and analysis. The results are shown in Table 1.

[0056] Results showed that palmitic acid, oleamide, and stearamide accounted for the highest proportions of the acid-soluble fraction isolated from grain-soaking wastewater, totaling 65.68%. These three compounds are characterized by their structural characteristics of containing long-chain fatty acids, which contributes to 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 fraction, explaining their acid solubility but insolubility in weakly alkaline conditions. The precipitation of [3,4,5-trihydroxyoxan-2-yl] 3,4,5-trihydroxybenzoic acid methyl ester is due, in part, to its inherent poor water solubility and, in part, to the disruption of the synergistic solubilization effect of natural substances. 6-Gingerol, while soluble in water in acidic media, may be protonated, but precipitates in weakly alkaline conditions due to its inability to protonate.

[0057] Table 1 Composition and relative content of acid soluble matter

[0058]

[0059] 2. The phenolic acids separated from the wastewater of Sichuan-style kaoliang xiaoqu wine soaking in this example were subjected to HPLC-MS detection and analysis. The results are shown in Table 2.

[0060] Table 2 Composition and relative content of phenolic acids

[0061]

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

[0063] 3. The polysaccharides separated from the wastewater of Sichuan-style kaoliang Xiaoqu wine soaking in this example were detected and analyzed using a Thermo ICS5000+ ion chromatograph. The results are shown in Table 3.

[0064] Table 3 Composition and relative content of polysaccharides

[0065]

[0066] The results showed that the polysaccharides separated from 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 matter in the wastewater polysaccharides.

[0067] 2. Process evaluation of macroporous resin adsorption separation of phenolic acids

[0068] 1. Different types of macroporous resins have different separation effects on different substances due to their different specific surface areas, pore sizes, and polarity. Table 4 shows the static adsorption and desorption rates of phenolic acids in wastewater by 18 different types of macroporous resins commonly used for the separation of 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, macroporous resins with high adsorption rates do not necessarily have high desorption rates. In order to extract and separate phenolic acids in wastewater to the greatest extent, this study used the product of adsorption rate and desorption rate as the standard to screen 18 resins. Among them, DM301 resin had the largest product of adsorption rate and desorption rate for phenolic acids in wastewater, so DM301 macroporous resin was selected as the purification resin for phenolic acids in grain soaking wastewater.

[0072] 2. Effect of sample solution pH on adsorption of DM301 macroporous resin Figure 2As shown in the figure, the ability of DM301 macroporous resin to adsorb phenolic acids in wastewater increases first and then decreases with increasing pH, reaching its maximum at pH 5.0. The hydroxyl groups in phenolic acids make them weakly acidic. At high pH values, they easily lose hydrogen ions to become negative ions, making them less likely to be adsorbed by macroporous resins. At lower pH values, they can be protonated, reducing their adsorption capacity. Only under appropriate pH conditions do phenolic acids in grain soaking wastewater exist in a molecular state, making them susceptible to adsorption 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 Figure 3 As shown, in low-concentration ethanol solutions, the desorption capacity of the macroporous resin increases with increasing ethanol concentration, reaching a maximum desorption capacity at 80% ethanol. After this, the desorption capacity decreases. Phenolic acids bind to the macroporous resin surface through hydrogen bonding or hydrophobic interactions. Increasing the ethanol concentration in the eluent favors their elution. Therefore, increasing the ethanol concentration can increase the desorption capacity. However, high ethanol concentrations cause impurities adsorbed on the macroporous resin to flow out with the eluent, resulting in a decrease in the desorption capacity of the target compound and hindering its separation and purification.

[0074] 4. Effect of sample volume on adsorption of macroporous resin Figure 4 As shown in the figure, it can be seen that with the increase of the sample volume, the concentration of phenolic acids in the effluent also increases. When the volume of wastewater added 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 ) is the same, indicating that the resin has reached saturation. To ensure sufficient adsorption of the macroporous resin while ensuring extraction and separation effectiveness, the leakage point is selected when the phenolic acid concentration in the effluent is 1 / 4 of the injection concentration. This means that a volume of 30 mL of wastewater corresponds to the adsorption capacity of 10 mL of macroporous resin. Therefore, when using DM301 macroporous resin to adsorb phenolic acids in 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 in the column.

[0075] 5. The effect of the amount of impurity removal water on the impurity removal effect Figure 5 As shown in the figure, polysaccharide is the organic matter with the largest content in grain soaking wastewater and is the main substance removed by impurity removal water. Figure 5As can be seen, the polysaccharide content in the effluent decreases dramatically with the addition of deionized water, demonstrating the effectiveness of DM301 resin in separating phenolic acids and polysaccharides from wastewater. When the deionized water dosage reaches 30 mL, further additions of deionized water maintain nearly constant polysaccharide content in the effluent, indicating that polysaccharide impurities trapped in the resin crevices have been eluted and removed. Therefore, 30 mL of deionized water, or 3 BV, is selected as the optimal deionized water dosage after 10 mL of resin adsorption is complete.

[0076] 6. With the addition of eluent, the concentration of phenolic acids in the effluent is as follows: Figure 6 As shown in Figure 2 , with the addition of 80% ethanol, the phenolic acids adsorbed on the macroporous resin were desorbed and eluted with the eluent. The phenolic acid content reached its maximum at 10 mL of eluent. After adding 30 mL of eluent, the phenolic acid content in the effluent reached its minimum and stabilized. With further additions of eluent, the phenolic acid content in the effluent remained essentially unchanged. Therefore, 30 mL of 80% ethanol was selected as the eluent volume for 10 mL of resin adsorption, or 3 BV.

[0077] 3. Research on the performance of antioxidants

[0078] 1. Evaluation of antioxidants' ability to scavenge OH

[0079] The ability of separated organic matter to remove ·OH was determined by colorimetry using reagents from Nanjing Jiancheng Bioengineering Research Institute, and the ·OH removal rate was calculated using the following formula.

[0080]

[0081] Where: A 对照 、A 空白 、A 测定 They correspond to the control tube, blank tube, and absorbance of the measured sample respectively.

[0082] The results of the scavenging experiment on OH by three organic compounds separated from wastewater at different concentrations are shown in Figure 7 Depend on. Figure 7 It can be seen that the acid-soluble matter in grain soaking wastewater has an excellent effect on scavenging hydroxyl free radicals. -1 The clearance rate was as high as 99% at the minimum added concentration; the isolated polysaccharide also showed efficient hydroxyl radical scavenging ability, at 0.8 g·L -1 The scavenging rate was as high as over 90% at the addition of 0.9 g·L; the separated phenolic acids also had a certain ability to scavenge hydroxyl free radicals, but the effect was poorer than that of the other two organic compounds. -1 The clearance rate was 48.7% at the maximum added concentration.

[0083] 2. Antioxidants remove O2 - Ability evaluation

[0084] Separate organic matter and remove O2 - The capacity was determined by colorimetric method using reagents from Nanjing Jiancheng Bioengineering Institute. - The clearance rate was calculated using the following formula.

[0085]

[0086] Where: A 对照 、A 测定 、A 标准 The absorbance of the corresponding samples was tested respectively.

[0087] Effects of three organic compounds separated from grain soaking wastewater on O2 - The clearing ability of Figure 8 As shown in the figure, it can be seen that the three isolates all have a certain ability to scavenge superoxide free radicals. The scavenging ability of the acid-soluble substance to superoxide free radicals is proportional to the concentration. The scavenging ability increases with the increase of the added concentration. At 1.0 g·L -1 The scavenging rate of the other two isolates can reach 31.4% at the added concentration of 1.54%. However, the scavenging ability of the other two isolates on superoxide free radicals decreased with the increase of the added concentration.

[0088] 3. Evaluation of antioxidants’ ability to scavenge DPPH

[0089] The ability of separated organic matter to remove DPPH was determined by colorimetry using reagents from Nanjing Jiancheng Bioengineering Institute, and the DPPH removal 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] Where: A 对照 、A 测定 、A 标准 The absorbance of the corresponding samples was tested respectively.

[0092] The scavenging ability of the three organic compounds isolated from grain soaking wastewater on DPPH is as follows: Figure 9 As shown. Figure 9 It can be seen that phenolic acids have an excellent effect on scavenging DPPH free radicals, and the scavenging ability is proportional to the added concentration. -1At the maximum addition concentration, the scavenging rate reached 98.7%. The other two organic compounds were also effective in scavenging DPPH free radicals, but at the maximum addition concentration, the scavenging rates were only 22.7% and 46.2%, respectively, far lower than those of phenolic acid compounds.

[0093] 4. Study on the performance of polysaccharides as microbial carbon sources

[0094] 1. The TN concentration in the solution affects the metabolism and growth of microorganisms. Properly increasing the TN concentration can usually promote the activity of denitrifying bacteria and accelerate the denitrification rate. However, when the TN concentration is too high, it may lead to an inhibitory effect and affect the growth and metabolism of bacteria. Cr The impact of Figure 10 .Depend on Figure 10 It can be seen that the removal rate of TN in the solution by microorganisms is inversely proportional to the TN concentration. Cr The removal rate of TN showed a trend of increasing first and then decreasing with the increase of TN concentration. To ensure the high efficiency of the removal, 14.5ppm was selected as the optimized TN concentration of the solution.

[0095] 2. Chemical oxygen demand reflects the content of organic matter in the solution. The denitrification process of denitrifying bacteria requires organic carbon as an electron donor. The appropriate amount of COD Cr It can provide sufficient carbon source for denitrifying bacteria, promote their growth and metabolism, and improve denitrification efficiency; while too high COD Cr This may lead to the proliferation of other heterotrophic microorganisms, competing with denitrifying bacteria for resources, and thus inhibiting the denitrification process. Cr Removal of TN and COD from solution by microorganisms Cr The impact of Figure 11 As shown. Figure 11 It can be found that as the COD Cr The increase of microorganisms on TN and COD Cr The removal rate also increases, reaching the maximum value of 67.2% and 10.5% at 800ppm and 600ppm respectively. Cr 800ppm as the COD optimized for solution Cr concentration.

[0096] 3. The optimal pH range for denitrifying bacteria is usually 6.5-8.5. Within this range, the activity of denitrifying enzyme is the highest and the denitrification efficiency is the best. However, due to different usage environments, the optimal pH may change. In order to explore the optimal pH of the solution when wastewater polysaccharides are added as a carbon source, the following research was conducted. The results are as follows: Figure 12As shown in the figure, the microbial TN removal rate was the highest at a solution pH of 7.0, reaching 53.8%. This indicates that denitrifying bacteria have strong growth and metabolic activity in solutions at this pH, so pH 7.0 was selected as the optimal pH for the solution.

[0097] 4. When glucose, sucrose and polysaccharide from grain wastewater were used as carbon sources, the microbial activity against TN and COD Cr The clearance rate of Figure 13 As shown in the figure, the comparison shows that after wastewater polysaccharide is added as carbon source, the microorganisms have a greater effect on TN and COD. Cr The clearance rates of both were better than those of glucose and sucrose added alone as carbon sources, among which the clearance rate of TN was particularly outstanding. The excellent TN clearance rate indicated that the denitrifying bacteria in the solution had strong biological activity and could grow and metabolize faster, proving that the polysaccharides separated from grain soaking wastewater had the potential to serve as a carbon source for denitrifying bacteria.

[0098] 5. Study on the performance of phenolic acids as corrosion inhibitors

[0099] 1. A carbon steel electrode was placed in a 0.5 M H2SO4 solution and phenolic acid substances (corrosion inhibitor 1) prepared in different concentrations were added to obtain a potentiodynamic polarization curve, as shown in FIG. Figure 14 As shown in the figure, it can be seen that after adding phenolic acid substances, the corrosion current density (i corr ) was significantly reduced, but the overall characteristics of the polarization curve were not changed, which indicates that the corrosion inhibition molecules in the phenolic acid substances blocked the active sites on the carbon steel surface, reducing the contact between the carbon steel and the corrosive medium H2SO4, thereby delaying the corrosion of the carbon steel. The blocking of the active sites may be attributed to the adsorption of the effective corrosion inhibition components in the phenolic acid substances on the carbon steel surface. At the same time, it can be found that the addition of phenolic acids causes the cathodic polarization curve to move to a lower current density, while the anodic polarization curve remains almost unchanged, which indicates 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 acids are a mixed corrosion inhibitor for carbon steel in a 0.5M H2SO4 corrosion environment that mainly inhibits the cathode.

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

[0101]

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

[0103] Table 5 shows the electrochemical polarization parameters obtained by Tafel extrapolation and the calculated corrosion inhibition efficiency. corr It can be found that the addition of phenolic acid substances makes the carbon steel corr The corrosion potential (E corr ) shifted negatively with the increase of phenolic acid concentration, indicating that phenolic acid had a more significant effect on the cathode reaction. corr The change in the value of β is less than 0.085V, which further proves that phenolic acid is a mixed corrosion inhibitor that mainly inhibits the cathode reaction. It is worth noting that with the addition of phenolic acid, the cathode Tafel slope (β c ) and the Tafel slope of the anode (β a ) values ​​did not change significantly, 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 achieved an inhibition efficiency of 93.03% on carbon steel corrosion in sulfuric acid solution, making them excellent corrosion inhibitors.

[0104] 2. A carbon steel electrode was placed in a 0.5M H2SO4 solution and phenolic acid substances (corrosion inhibitor 1) prepared in different concentrations were added to obtain an impedance spectrum, as shown in FIG. Figure 15 As shown in Figure 2 , the diameter of the capacitive arc in the Nyquist plot increases significantly with the addition of phenolic acids, indicating that the corrosion of carbon steel in 0.5 M H₂SO₄ solution is inhibited. Bode analysis reveals that the impedance modulus increases with increasing phenolic acid concentration, indicating 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 mechanism of carbon steel in 0.5 M H₂SO₄ solution. The capacitive arc appears as a flattened semicircle, rather than a perfect semicircle, due to the irregularities and inhomogeneities 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 in the double layer, while the inductive reactance in the low-frequency region is generally associated with the relaxation process of the electrode surface state variable, indicating that the corrosion inhibitor is adsorbed on the carbon steel surface. As the concentration of corrosion inhibitor increases, the induced arc also increases, indicating that the inductive arc is caused by the adsorption and desorption of corrosion inhibitor. However, the inductive arc in the experiment is generally small and incomplete, which can easily lead to large fitting errors. Combining the characteristics of Bode diagrams, using data in the medium and high frequency range, the Figure 4-4 The equivalent circuit shown is fitted with impedance parameters. Among them, R s Represents the solution resistance, Rct Represents charge transfer resistance, and CPE stands for constant phase element, which is often used to replace ideal electrical appliances to take into account non-uniformity.

[0105] The impedance of CPE can be defined as;

[0106]

[0107] Where: Y0 is the magnitude of the CPE, n is the diffusion effect index, which is the microscopic oscillation on the carbon steel surface, j represents the imaginary unit, and ω is the angular frequency. The CPE can be an inductor with n equal to -1, a resistor with n equal to zero, a Warburg impedance with n equal to 0.5, or a capacitor with n equal to 1.

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

[93] as follows:

[0109]

[0110] Where: R ct and R' ct is the charge transfer resistance without and with different concentrations of SOW.

[0111] Table 6 shows the impedance fitting parameters for carbon steel in 0.5 M H₂SO₄ solutions containing various concentrations of phenolic acids at different temperatures. The chi-square (χ₂) values, which reflect the reliability of the fitting results, are low, indicating that the equivalent circuit used is reasonable. As shown in the table, the corrosion inhibition efficiency of phenolic acids on carbon steel increases significantly with increasing concentration, reaching an inhibitory efficiency of 93.24% at the maximum concentration, similar to the polarization test results. Furthermore, the fitted CPE values ​​decrease with increasing phenolic acid concentration, indicating that the active ingredients in the phenolic acids are adsorbed on the carbon steel surface, and the thickness of the adsorbed film increases with increasing concentration.

[0112] 3. A carbon steel electrode was placed in a 0.5 M H2SO4 solution, and a compound corrosion inhibitor (corrosion inhibitor 2) consisting of phenolic acid substances prepared in different concentrations and KI in equal proportions was added to obtain a potentiodynamic polarization curve, as shown in FIG. Figure 16 As shown in Table 5, the addition of phenolic acid-KI as a corrosion inhibitor significantly reduces the cathodic corrosion current density of carbon steel in corrosive media at relatively low concentrations. Increasing the concentration also effectively reduces the anodic corrosion current density, inhibiting the anodic dissolution of carbon steel. This demonstrates that the phenolic acids isolated from grain-soaking wastewater, when combined with KI, are highly effective corrosion inhibitors. Polarization parameters fitted using the Tafel extrapolation method are listed in Table 5. The inhibition efficiency of phenolic acid-KI for carbon steel reaches 98.95% at the maximum addition concentration, making it an extremely excellent corrosion inhibitor.

[0113] 4. A carbon steel electrode was placed in a 0.5 M H2SO4 solution, and a compound corrosion inhibitor (corrosion inhibitor 2) consisting of phenolic acid substances prepared in different concentrations and KI in equal proportions was added to obtain a dynamic impedance spectrum, as shown in FIG. Figure 17 shown.

[0114] After the addition of phenolic acid-KI as a corrosion inhibitor, the capacitance arc radius increased significantly at a low addition concentration, and with the increase of concentration, the capacitance arc radius also increased accordingly, 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. The corrosion inhibition efficiency of phenolic acid-KI on carbon steel can reach 98.48% at the maximum addition concentration, which is similar to the polarization test results, proving the excellent corrosion inhibition effect of phenolic acid-KI. In addition, compared with the addition of 1.0g·L -1 and 1.5 g·L -1 R of phenolic acids ct And η, 1.5g·L -1 The inhibitory effect of phenolic acid-KI on carbon steel corrosion was significantly improved at the added dose. This may be because at low inhibitor concentrations, the adsorption capacity is insufficient, and a complete adsorption film cannot be formed on the carbon steel surface, resulting in localized corrosion on the carbon steel surface. However, as the inhibitor concentration increases, the number of adsorbed molecules increases, and the continuity and density of the adsorption film are enhanced, thereby more effectively isolating the corrosive medium from the metal.

[0115] Table 5 Polarization curve fitting parameters of carbon steel in 0.5MH2SO4 solution containing different types and concentrations of organic matter at 30℃

[0116]

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

[0118]

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

[0120] Table 7 lists the corrosion rate of carbon steel in 0.5M H2SO4 solution after adding phenolic acid compounds and KI as corrosion inhibitors and the calculated corrosion inhibition efficiency. Compared with the blank group without corrosion inhibitor, the corrosion rate of carbon steel after adding phenolic acid-KI increased from 40.63 g·m -2 ·h -1 Reduced to 0.68 g·m -2 ·h-1 The corrosion inhibition efficiency reached an astonishing 98.33%, further proving the excellent corrosion inhibition performance of the compound.

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

[0122]

[0123] Figure 18 (c) is the concentration of 1.5 g·L -1 SEM images of phenolic acid-KI after immersion in 0.5M H2SO4 solution for 4 hours. Figure 18 (b) It can be seen that after adding the corrosion inhibitor, the corrosion degree of carbon steel in the corrosive medium is significantly reduced, the surface is smoother and flatter, and there are no obvious corrosion pits. In addition, compared with the non-corroded Figure 18 (a) It can be seen that the surface of carbon steel with corrosion inhibitor added is similar to that of carbon steel without corrosion, and only very slight corrosion occurs, which further proves that the phenolic acids in grain soaking wastewater show excellent corrosion inhibition performance after being compounded with KI.

[0124] Carbon steel contains 1.5g·L -1 The AFM and 3D contour images of phenolic acid-KI after immersion in 0.5M H2SO4 solution for 4 hours are shown in Figure 2. Figure 19 and Figure 20 As shown in 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 without corrosion. The calculated R a and S a It is also much smaller than the sample without corrosion inhibitor, which shows that the compound has excellent inhibitory effect on the corrosion of carbon steel in 0.5MH2SO4 solution.

[0125] Finally, it should be noted that the above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for resource utilization of grain soaking wastewater, characterized in that: The specific steps include: (1) removing suspended matter from the grain soaking wastewater, and then concentrating the wastewater by vacuum distillation to obtain a wastewater concentrate; (2) The pH value of the wastewater concentrate is adjusted to 8.0, and then the concentrate is allowed to stand at 4-10°C to precipitate, and then centrifuged to obtain an acid-soluble substance, and the supernatant is collected for later use; (3) using a macroporous resin to adsorb and separate phenolic acids in the supernatant, collecting the eluent and distilling it under reduced pressure to obtain phenolic acids, and collecting the decontaminated water rich in polysaccharides for later use; (4) Using Sevage reagent to remove the protein in the impurity-removed water in step (3), the solution was concentrated by vacuum distillation to a viscous solution, and then an 80% ethanol solution was added. After ultrasonic vibration for 15 to 30 minutes, the solution was allowed to stand at 4 to 10° C. to precipitate, and then centrifuged to obtain polysaccharide, wherein the mass volume ratio of the viscous solution to the 80% ethanol solution was 1 g: 5 to 15 mL.

2. The method for resource utilization of grain soaking wastewater according to claim 1, characterized in that: In step (2), 0.5 M sodium hydroxide solution was used to adjust the pH.

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 macroporous resin.

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

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

1.

6. Use of the acid-soluble substance, phenolic acid substance or polysaccharide according to claim 1 as an antioxidant in scavenging hydroxyl radicals, superoxide radicals and DPPH radicals, wherein the amount of the antioxidant added is 0.2 to 1.0 g / L.

7. Use of the phenolic acid substance according to claim 1 as a corrosion inhibitor in an acidic solution environment for steel pickling and oil and gas acidification production.

8. The use of the phenolic acid substance according to claim 7 as a pickling corrosion inhibitor in an acidic solution environment for steel pickling and oil and gas acidification mining, 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. Use of the polysaccharide according to claim 1 as a carbon source for microorganisms.

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

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