Flocculating agent for sewage treatment

Abstract

The invention provides a flocculating agent for sewage treatment. The flocculating agent for sewage treatment is prepared from the following components: polyacrylamide, a surfactant, a modified ferric chloride compound, sodium chloride, a pH regulator and an auxiliary agent, wherein the modified ferric chloride compound is a product obtained by reaction of starch and ferric chloride. The preparation method of the flocculating agent for sewage treatment comprises the following steps: S1, adding starch and caustic soda liquid into water, stirring, then adding acid into the water, adjusting the pH value, then adding a ferric trichloride solution into the water, reacting, and curing to obtain the modified ferric chloride compound; s2, polyacrylamide is added into the modified ferric chloride compound, standing is conducted for 15-30 min, and a mixture is obtained; s3, blending other components with the mixture, and stirring to obtain the flocculating agent for sewage treatment. The modified ferric chloride compound improves the adsorption capacity and stability of the flocculant, and has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and mainly to a flocculant used for sewage treatment. Background Art

[0002] Wastewater treatment is an important part of environmental protection. my country is a country with a shortage of water resources and a low per capita water resource. Through sewage treatment, harmful substances in sewage can be removed so that the treated water can be reused in industrial production, agricultural irrigation, urban landscape water replenishment and many other aspects, thereby alleviating the contradiction between supply and demand of water resources and realizing the recycling of water resources. Direct discharge of untreated sewage will cause surface water pollution, such as rivers, lakes, and oceans. Organic matter, heavy metals, and nutrients in sewage will make the water body black and smelly, leading to frequent problems such as eutrophication. At the same time, sewage will also pollute groundwater through soil infiltration and other methods. Effective sewage treatment can prevent these pollutants from entering the water body, protect the water quality of surface water and groundwater, and maintain the health of aquatic ecosystems.

[0003] As a commonly used sewage treatment product, flocculants have many advantages. For example, they can efficiently remove suspended matter and colloids, causing the suspended matter and colloid particles in sewage to aggregate into larger flocs, which are easy to precipitate or filter out; through adsorption, complexation and other effects, they can reduce the content of organic matter and heavy metals, reduce the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of sewage, and reduce pollution to the environment; they have a wide range of applications, whether it is industrial wastewater or domestic sewage, whether it is acidic, alkaline or neutral sewage, you can find a suitable flocculant for treatment, and they have strong adaptability to sewage of different types and properties.

[0004] Polyacrylamide flocculant is a commonly used sewage treatment product with the following advantages: fast and efficient, it can form larger flocs of suspended particles, colloids, etc. in sewage in a short time, greatly shortening the sewage treatment time; good removal effect, it has a good removal effect on various types of suspended particles and colloid substances, such as silt, organic matter, heavy metal ions, etc.

[0005] Ferric chloride is also a commonly used sewage treatment product with the following advantages: good floc formation, the ferric hydroxide precipitate generated after hydrolysis has extremely strong cohesive force, the formed flocs are large and dense, the precipitation speed is fast, and the solid-liquid separation efficiency is improved; it has a strong effect on organic matter, and has a strong adsorption capacity for emulsified and semi-emulsified organic matter in water, and can effectively remove organic matter in sewage and reduce the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of the effluent; it has good low-temperature treatment effect, and its treatment effect on low-temperature turbid water is better than other flocculants, and it can still maintain good flocculation performance under low temperature conditions to ensure the stability of sewage treatment effect.

[0006] At present, some researchers have compounded polyacrylamide with ferric chloride to prepare flocculants, and achieved good results. However, there are still some problems, such as: temperature has a significant effect on the adsorption effect of flocculants, and too low or too high temperature will significantly reduce the effect; there is still room for improvement in the removal rate of various pollutants in sewage; the stability is insufficient, especially after long-term storage, the viscosity decreases, resulting in reduced adsorption effect, which is more obvious in harsh storage environments, etc. As society's requirements for environmental protection become higher and higher, the current polyacrylamide and ferric chloride compound flocculants can no longer meet the requirements of higher temperature adaptability, higher pollutant removal rate, better stability, etc.

[0007] In summary, it is necessary to develop a new technical solution to solve the defects and shortcomings in the existing technology. Summary of the invention

[0008] The invention provides a flocculant for sewage treatment. The flocculant for sewage treatment is compounded with components such as polyacrylamide and modified ferric chloride complex, has the advantages of better temperature adaptability, higher pollutant removal rate, better stability, etc. than common flocculants, and has good application prospects.

[0009] One object of the present invention is to provide a flocculant for sewage treatment, wherein the flocculant for sewage treatment comprises the following components in parts by weight: Polyacrylamide 20-40 parts Surfactant 4-8 parts 5-8 parts of modified ferric chloride complex 1-2 parts sodium chloride pH adjuster 1-2 parts 1-2 parts of additives; Wherein, the modified ferric chloride complex is a product obtained by the reaction of starch and ferric chloride.

[0010] Furthermore, the auxiliary agent is selected from one or more of inorganic salts, starch, and seaweed powder.

[0011] Furthermore, the surfactant is selected from one or more of anionic surfactants or amphoteric surfactants.

[0012] Furthermore, the pH regulator is selected from one or more of sodium carbonate, tartaric acid and citric acid.

[0013] Furthermore, the molecular weight of the polyacrylamide is 8-12 million.

[0014] Another object of the present invention is to provide a method for preparing the above-mentioned flocculant for sewage treatment, the method for preparing the flocculant for sewage treatment comprising the following steps: S1, adding starch and liquid alkali into water, stirring, then adding acid thereto, adjusting the pH, and then adding ferric chloride solution thereto, reacting and ripening to obtain the modified ferric chloride complex; S2, adding polyacrylamide to the modified ferric chloride complex, standing for 15-30 minutes, to obtain a mixture; S3, blending the remaining components with the mixture and stirring to obtain the flocculant for sewage treatment.

[0015] Furthermore, the mass ratio of the starch, liquid alkali and ferric chloride solution is (2-3):(0.2-0.3):(150-200).

[0016] Furthermore, the mass fraction of the ferric chloride solution is 30-44%.

[0017] Furthermore, the reaction temperature is 40-50°C and the reaction time is 2-4h.

[0018] Furthermore, the ripening time is 16-20 hours.

[0019] The present invention has the following beneficial effects: In the flocculant for sewage treatment provided by the present invention, starch is a high molecular polymer, which can effectively adsorb pollutants through adsorption bridging and other effects, and after reacting with ferric chloride to generate a modified ferric chloride complex, the adsorption capacity is improved while the charge amount is increased, thereby further improving the adsorption capacity; starch introduces organic segments into the modified ferric chloride complex, thereby improving the compatibility of the modified ferric chloride complex with other components, allowing each component to be evenly dispersed, thereby avoiding agglomeration and resulting in reduced adsorption effect; the organic segment and other components can generate intermolecular forces, exert synergistic effects, and form a more stable structure; the organic segment is a long chain, which can be interspersed between components such as polyacrylamide, thereby further enhancing stability and avoiding reduced adsorption effect due to decreased viscosity caused by insufficient stability. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0021] The words "preferred", "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0022] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers indicating, for example, the amounts of ingredients used in the specification and claims should be understood to be modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary depending on the desired properties to be obtained by the present invention.

[0023] The following raw materials are used in the embodiments of the present invention: Polyacrylamide, molecular weight 10 million, purchased from Guangdong Shouxin Environmental Protection Materials Technology Co., Ltd.; The surfactant was dodecyl dimethyl betaine, purchased from Hubei Watson Chemical Technology Co., Ltd.; The pH regulator was citric acid, purchased from Shandong Haihua Biotechnology Co., Ltd.; The auxiliary agent was starch, which was purchased from Wuhan Runxingyuan Technology Co., Ltd. Example 1

[0024] A flocculant for sewage treatment, comprising the following components in parts by weight: Polyacrylamide 40 parts 8 parts surfactant 7 parts of modified ferric chloride complex 2 parts sodium chloride 2 parts pH adjuster 2 parts of additives.

[0025] The preparation method of the above-mentioned flocculant for sewage treatment comprises the following steps: S1, adding corn starch to water and heating to 50°C and slowly adding sodium hydroxide (mass ratio of 2.5:500:0.25), stirring for 1 hour, adding 30wt% hydrochloric acid to adjust the pH of the solution to 2, controlling the temperature to 45°C, adding 40wt% ferric chloride solution (the mass ratio of corn starch to ferric chloride solution is 2.5:175), reacting for 3 hours, cooling to room temperature and ripening for 18 hours, and freeze-drying to obtain the modified ferric chloride complex; S2. Blending polyacrylamide and modified ferric chloride composite according to the above mass fractions, and standing for 30 minutes to obtain a mixture; S3. Blend the mixture with dodecyl dimethyl betaine, sodium chloride, citric acid and starch according to the above mass fractions, add sufficient water and stir until completely dissolved to obtain the flocculant for sewage treatment. Example 2

[0026] A flocculant for sewage treatment, comprising the following components in parts by weight: Polyacrylamide 38 parts Surfactant 7 parts 7 parts of modified ferric chloride complex 2 parts sodium chloride 2 parts pH adjuster 2 parts of additives.

[0027] The preparation method of the above-mentioned flocculant for sewage treatment comprises the following steps: S1, adding corn starch to water and heating to 50°C and slowly adding sodium hydroxide (mass ratio of 2.5:500:0.25), stirring for 1 hour, adding 30wt% hydrochloric acid to adjust the pH of the solution to 2, controlling the temperature to 45°C, adding 40wt% ferric chloride solution (the mass ratio of corn starch to ferric chloride solution is 2.5:175), reacting for 3 hours, cooling to room temperature and ripening for 18 hours, and freeze-drying to obtain the modified ferric chloride complex; S2. Blending polyacrylamide and modified ferric chloride composite according to the above mass fractions, and standing for 30 minutes to obtain a mixture; S3. Blend the mixture with dodecyl dimethyl betaine, sodium chloride, citric acid and starch according to the above mass fractions, add sufficient water and stir until completely dissolved to obtain the flocculant for sewage treatment. Example 3

[0028] A flocculant for sewage treatment, comprising the following components in parts by weight: Polyacrylamide 36 parts 6 parts surfactant 6 parts of modified ferric chloride complex 2 parts sodium chloride 2 parts pH adjuster 2 parts of additives.

[0029] The preparation method of the above-mentioned flocculant for sewage treatment comprises the following steps: S1, adding corn starch to water and heating to 50°C and slowly adding sodium hydroxide (mass ratio of 2.5:500:0.25), stirring for 1 hour, adding 30wt% hydrochloric acid to adjust the pH of the solution to 2, controlling the temperature to 45°C, adding 40wt% ferric chloride solution (the mass ratio of corn starch to ferric chloride solution is 2.5:175), reacting for 3 hours, cooling to room temperature and ripening for 18 hours, and freeze-drying to obtain the modified ferric chloride complex; S2. Blending polyacrylamide and modified ferric chloride composite according to the above mass fractions, and standing for 30 minutes to obtain a mixture; S3. Blend the mixture with dodecyl dimethyl betaine, sodium chloride, citric acid and starch according to the above mass fractions, add sufficient water and stir until completely dissolved to obtain the flocculant for sewage treatment.

[0030] Comparative Example The components and preparation method of the comparative example are the same as those of Example 1, except that the mass of corn starch in step S1 is replaced by glucose.

[0031] Test Case The performance of the flocculants prepared in Examples 1-3 and Comparative Examples was measured.

[0032] Test Method (1) At 20, 30, 40, 50, and 60°C, take 200 ml of domestic sewage and place it in a 250 ml beaker and stir. Add 0.5% of the sewage mass of a flocculant, stir and let it stand. Record the time for the pollutants to decrease (until the pollutants do not decrease significantly). Let it stand for another 60 seconds, take 15 ml of the solution from the supernatant, measure the turbidity of the supernatant solution using a turbidity meter, and calculate the turbidity removal rate and sedimentation rate.

[0033] The turbidity removal rate calculation formula is:

[0034] Among them, η is the turbidity removal rate, C0 is the initial turbidity of sewage, and C1 is the turbidity of the supernatant after coagulation; The formula for calculating the sedimentation velocity is:

[0035] Where ϑ is the settling velocity in mm / s, H is the settling distance in mm, and t is the settling time in s.

[0036] (2) At room temperature, the components of the supernatant of the domestic sewage before treatment with the flocculant in Examples 1-3 and the comparative example and after treatment with a flocculant at a concentration of 0.5% by mass of the sewage were measured, and the pollutant removal rate was calculated, where the pollutants included chemical oxygen demand (COD), biochemical oxygen demand (BOD), suspended solids (SS), ammonia nitrogen, and phosphorus.

[0037] (3) 0.5 g of each flocculant of Examples 1-3 and the comparative example was dissolved in 30 ml of water and stored at 25°C for 45 days. The viscosity was recorded and the stability was evaluated by the change in viscosity.

[0038] Test Results Table 1 shows the flocculation performance test results of Examples 1-3 and Comparative Examples, Table 2 shows the pollutant removal rates of Examples 1-3 and Comparative Examples after treating domestic sewage with flocculants, and Table 3 shows the viscosity changes of Examples 1-3 and Comparative Examples after storage at 25°C for 45 days.

[0039] Table 1 Flocculation performance test results of Examples 1-3 and Comparative Examples

[0040] Table 2 Pollutant removal rate after treating domestic sewage with flocculants in Examples 1-3 and Comparative Examples

[0041] Table 3 Stability of Examples 1-3 and Comparative Examples after 45 days of storage at 25°C

[0042] It can be seen from Tables 1, 2 and 3 that the effects and stability of Examples 1-3 are significantly better than those of the Comparative Example. This is because the Comparative Example uses glucose instead of the high molecular polymer corn starch of the Example, and the product generated by the reaction of glucose and ferric chloride does not contain long organic chains, which reduces the adsorption capacity and reduces the compatibility of the components, making it easy to agglomerate and causing reduced stability.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0044] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A flocculant for sewage treatment, characterized in that: The flocculant for sewage treatment comprises the following components in parts by weight: Polyacrylamide 20-40 parts Surfactant 4-8 parts 5-8 parts of modified ferric chloride complex 1-2 parts sodium chloride pH adjuster 1-2 parts 1-2 parts of additives; Wherein, the modified ferric chloride complex is a product obtained by the reaction of starch and ferric chloride.

2. The flocculant for sewage treatment according to claim 1, characterized in that: The auxiliary agent is selected from one or more of inorganic salts, starch and seaweed powder.

3. The flocculant for sewage treatment according to claim 1, characterized in that: The surfactant is selected from one or more of anionic surfactants and amphoteric surfactants.

4. The flocculant for sewage treatment according to claim 1, characterized in that: The molecular weight of the polyacrylamide is 8-12 million.

5. The method for preparing a flocculant for sewage treatment according to any one of claims 1 to 4, characterized in that: The preparation method of the flocculant for sewage treatment comprises the following steps: S1, adding starch and liquid alkali into water, stirring, then adding acid thereto, adjusting the pH, and then adding ferric chloride solution thereto, reacting and ripening to obtain the modified ferric chloride complex; S2, adding polyacrylamide to the modified ferric chloride complex, standing for 15-30 minutes, to obtain a mixture; S3, blending the remaining components with the mixture and stirring to obtain the flocculant for sewage treatment.

6. The method for preparing a flocculant for sewage treatment according to claim 5, characterized in that: The mass ratio of the starch, liquid alkali and ferric chloride solution is (2-3):(0.2-0.3):(150-200).

7. The method for preparing a flocculant for sewage treatment according to claim 5, characterized in that: The mass fraction of the ferric chloride solution is 30-44%.

8. The method for preparing a flocculant for sewage treatment according to claim 5, characterized in that: The reaction temperature is 40-50°C and the reaction time is 2-4h.

9. The method for preparing a flocculant for sewage treatment according to claim 5, characterized in that: The aging time is 16-20 hours.

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