Preparation method of diatomite slow-release sodium persulfate gel composite material

Abstract

The invention relates to a preparation method of a diatomite slow-release sodium persulfate gel composite material. The preparation method is characterized by specifically comprising the following steps: S1, pretreatment of diatomite; S2, preparation of modified diatomite; and S3, preparation of a diatomite slow-release oxidant gel composite material. The diatomite prepared by adopting the design has the characteristic of high surface area, the adsorption capacity of the diatomite after alkali modification can be enhanced, the loading capacity of sodium persulfate can be improved, the mechanical strength of the gel material can be improved after the diatomite is embedded, and the service life of the sustained-release material is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater pollution control, and in particular to a method for preparing a diatomaceous earth slow-release sodium persulfate gel composite material. Background Art

[0002] In-situ chemical oxidation is one of the mainstream treatment methods for groundwater pollution control and has been successfully applied to the remediation of organic groundwater pollution. However, traditional in-situ oxidation technology lacks effective selectivity for pollutants and cannot deliver oxidants for a long time, resulting in poor stability of the remediation effect, reverse diffusion of agents, concentration tailing, and pollutant rebound during remediation. It faces the problem of rising remediation costs and declining remediation effects, which is easy to cause secondary pollution. In order to solve the problem of in-situ remediation, slow-release oxidation technology has received widespread attention from researchers at home and abroad. This technology uses special materials or devices to slowly release oxidants. It has the characteristics of controlling the release rate of active compounds, reducing the non-selective consumption of oxidants, and maintaining an oxidizing environment for a long time, making the remediation process more stable and lasting.

[0003] However, slow-release technology still faces some challenges in groundwater remediation. For example, the stability, controllability and renewability of slow-release materials directly affect the remediation effect of pollutants. Therefore, in order to improve the remediation effect and adaptability of slow-release technology, it is crucial to develop slow-release materials with stable performance and their application technology. Summary of the invention

[0004] In order to solve the above problems, the present invention designs a preparation method of a diatomite slow-release sodium persulfate gel composite material. By adopting this design, the alkali-modified diatomite can enhance its adsorption capacity, increase the loading amount of sodium persulfate, and improve the mechanical strength of the gel material after being embedded, thereby increasing the service life of the slow-release material, so that the diatomite has the characteristics of a high surface area.

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material, which specifically comprises the following steps:

[0006] S1: Pretreatment of diatomite: The diatomite raw material is sent to a pretreatment box, first passed through a 100-mesh sieve, then washed with deionized water to remove impurities, and finally dried at 45-50°C for use;

[0007] S2: Preparation of modified diatomite: Take an appropriate amount of the dried diatomite prepared in step S1, add an appropriate amount of sodium hydroxide solution, stir at 100°C for 2h to form a uniform turbid liquid, then inject it into a mold, place it in a vacuum drying oven at 70°C for 24h to obtain hard modified diatomite, and grind it for later use;

[0008] S3: Preparation of diatomite slow-release oxidant gel composite material: 4%-20% soluble starch, 4%-10% polyvinyl alcohol, 4%-10% modified diatomite and 2%-5% sodium persulfate powder are weighed in proportion, the soluble starch is first dissolved in distilled water, and continuous stirring is performed in a stirring tank to ensure that the starch is evenly dispersed in the water, and then polyvinyl alcohol is added to the starch solution, and the temperature is controlled between 60-90°C for stirring in a water bath to make the polyvinyl alcohol evenly dispersed in the starch solution, and then the ground modified diatomite is added, and glycerol is added after stirring to form a uniform turbid liquid, and continuous stirring is continued for 2 hours; then sodium persulfate powder is added and continuous stirring is continued for 2 hours; finally, 0.2-1M boric acid solution is added, and after standing for 5-10 minutes, a colloidal diatomite composite gel is obtained, and the colloidal substance is injected into a mold, dried at 60°C, and stored in a desiccator for later use.

[0009] Further: in the step S3, the soluble starch polyvinyl alcohol, modified diatomaceous earth and sodium persulfate powder weighed in proportion are 20%, 10%, 10% and 4% respectively, and the boric acid solution is preferably a 0.2M boric acid solution.

[0010] Furthermore: the pretreatment box in step S1 is composed of a material guiding box, a filtering box and a heating and drying box, the material guiding box is inclined and its lower end is connected to the side wall of the filtering box, a material inlet is arranged on the top of the upper end of the material guiding box, a first rotating shaft is rotatably connected to the material guiding box, one end of the first rotating shaft is connected to a first conveying motor fixed on the outer wall of the material guiding box and a first spiral blade is mounted thereon, so the filtering box and the heating and drying box are detachably connected up and down, a first through groove is provided at the connection between the filtering box and the material guiding box, the filtering box is connected to the material guiding box through the first through groove, a cover plate is detachably connected to the top of the filtering box, a rotating elution mechanism is arranged at the bottom of the cover plate, and an arc-shaped screen filter plate with a 100-mesh screen is installed at the bottom of the filtering box The filtering box is connected with the heating and drying box through the sieve holes provided on the arc-shaped sieve filter plate, and the heating and drying box is suspended and supported by a plurality of columns arranged at the bottom, and a second spiral conveying mechanism is arranged in the lower end of the heating and drying box, and the bottom of the heating and drying box is in an arc shape matching the second spiral conveying mechanism, and a material guiding hood body connected thereto is arranged on the right end side wall of the lower end of the heating and drying box body, and the material guiding hood body is arranged horizontally, and the bottom surface thereof is flush with the lower end of the heating and drying box body, and a second through groove is arranged on the side wall of the lower end of the heating and drying box body facing the material guiding hood body, and the heating and drying box body is connected with the material guiding hood body through the second through groove, and a material outlet is arranged at the bottom of the material guiding hood body, and a blocking mechanism is also arranged in the material guiding hood body, and the second through groove is sealed by the blocking mechanism.

[0011] Furthermore: a flushing pipe is arranged above the material guide box, and a plurality of flushing nozzles are connected to the bottom of the flushing pipe in sequence from left to right through branch pipes. The flushing nozzles are installed on the top wall of the material guide box, and the branch pipes extend into the material guide box and are connected to the flushing nozzles.

[0012] Furthermore: the rotating elution mechanism includes a first annular elution tube, a second annular elution tube, a hollow support tube, a rotating motor, a driving gear and a driven gear. The hollow support tube is placed vertically and its upper end is rotatably connected to the bottom of the cover plate through a bearing structure. The upper end of the hollow support tube passes through the cover plate and is connected to the pressure water pipe through a first mechanical sealing structure. The first annular elution tube and the second annular elution tube are connected to the outside of the hollow support tube one above and one below. The first annular elution tube and the second annular elution tube are both connected to the hollow support tube and rotated under the drive of the hollow support tube. A plurality of elution nozzles are provided at the bottom of the first annular elution tube and the second annular elution tube. The driven gear is mounted on the outer wall of the upper end of the hollow support tube. The rotating motor is installed on the top of the cover plate. The driving gear is installed on the output shaft of the rotating motor and meshes with the driven gear.

[0013] Further: the second spiral conveying mechanism includes a second rotating shaft, a second spiral blade and a second conveying motor, the second rotating shaft is horizontally rotatably connected to the lower end of the heating and drying box body, and its left end is connected to the second conveying motor installed on the left outer wall of the heating and drying box body, the second spiral blade is sleeved on the second rotating shaft in the heating and drying box body, and the right end of the second rotating shaft extends into the second through groove and is connected to the blocking mechanism, the blocking mechanism is connected by a hollow rotating shaft, a rubber plug and a sealing electric cylinder, the hollow rotating shaft is horizontally arranged in the material guide cover body, its left end is connected to the second rotating shaft and rotates therewith, the right end of the second rotating shaft is connected to the second mechanical sealing structure arranged on the right end side wall of the material guide cover body, the hollow rotating shaft is rotatably connected with a rubber plug, the rubber plug is piston-connected in the material guide cover body and connected to the sealing electric cylinder installed on the outer wall of the heating and drying box body, and the rubber plug is translated along the hollow rotating shaft under the drive of the sealing electric cylinder and seals the second through groove.

[0014] Furthermore: the second mechanical sealing structure is connected to a heating medium extraction pipeline and a heating medium delivery pipeline, and a feed channel and a reflux channel connected to the heating medium extraction pipeline and the heating medium delivery pipeline are respectively provided in the hollow rotating shaft and the second rotating shaft, and a circulation channel is also provided in the second spiral blade, one end of the circulation channel is connected to the feed channel, and the other end of the circulation channel is connected to the reflux channel, and a temperature sensor is also arranged in the heating and drying box.

[0015] Furthermore: in the step S2, a pressure protection valve is installed on the top of the vacuum drying oven, and the pressure protection valve includes a first valve body, a second valve body, a valve core, a spring, a pull rod electric cylinder, a pull rod and a pull plate. One end of the first valve body is fixed on the top of the vacuum drying oven and is connected thereto, and the other end of the first valve body is fixed on the outer wall of the second valve body. A plurality of through holes are provided on one end of the second valve body extending into the first valve body, and the other end of the second valve body is open. The valve core is connected to the second valve body through a spring and faces the through holes. A pressure relief hole is provided on the side wall of the second valve body in the first valve body, and the pressure relief hole is sealed by the valve core. The pull rod electric cylinder is installed on one end of the second valve body extending into the first valve body, and the output shaft end of the pull rod electric cylinder extends into the second valve body and is connected to the pull rod, which passes through the valve core and is connected to the pull plate, and the valve core is piston-connected to the pull rod and the second valve body.

[0016] After adopting the above structure, the beneficial effects of the present invention are as follows:

[0017] 1. The diatomaceous earth in the present invention has the characteristics of high surface area. The alkali-modified diatomaceous earth can enhance its adsorption capacity, increase the loading amount of sodium persulfate, and improve the mechanical strength of the gel material after being embedded, thereby increasing the service life of the sustained-release material;

[0018] 2. The present invention forms a gel coating by polyvinyl alcohol / starch, which can achieve the slow release of sodium persulfate;

[0019] 3. The present invention uses polyvinyl alcohol and starch as gel materials and diatomaceous earth as a carrier, which is environmentally friendly and low in cost. It can be used as a filling material for a permeable reaction barrier and is easy to replace.

[0020] 4. The pretreatment box used in the present invention can automatically complete the pretreatment of diatomite, greatly improving the processing efficiency.

[0021] 5. The present invention is provided with a flushing nozzle in the material guide box and a rotary rinsing mechanism in the filter box. The flushing nozzle and the rotary rinsing mechanism can completely flush the diatomaceous earth remaining in the material guide box and the filter box into the heating and drying box. This structure plays a role in saving resources.

[0022] 6. The present invention installs a pressure protection valve on the top of the vacuum drying box, which plays a role of self-protection, prevents unnecessary damage to the structure caused by excessive internal and external pressure difference, and plays a role in increasing practical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1This is a schematic diagram of the structure of the pretreatment box.

[0025] Figure 2 This is the structural diagram of the rotary elution mechanism.

[0026] Figure 3 This is the internal structure diagram of the pressure protection valve.

[0027] Figure 4 It is a comparison chart of the sustained-release performance of sodium persulfate in Examples 1-3 and the performance of paraffin sustained-release material. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material, which specifically comprises the following steps:

[0029] S1: Pretreatment of diatomite: The diatomite raw material is sent to a pretreatment box, first passed through a 100-mesh sieve, then washed with deionized water to remove impurities, and finally dried at 45-50°C for use;

[0030] S2: Preparation of modified diatomite: Take an appropriate amount of the dried diatomite prepared in step S1, add an appropriate amount of sodium hydroxide solution, stir at 100°C for 2h to form a uniform turbid liquid, then inject it into a mold, place it in a vacuum drying oven at 70°C for 24h to obtain hard modified diatomite, and grind it for later use;

[0031] S3: Preparation of diatomite slow-release oxidant gel composite material: 4%-20% soluble starch, 4%-10% polyvinyl alcohol, 4%-10% modified diatomite and 2%-5% sodium persulfate powder are weighed in proportion, the soluble starch is first dissolved in distilled water, and continuous stirring is performed in a stirring tank to ensure that the starch is evenly dispersed in the water, and then polyvinyl alcohol is added to the starch solution, and the temperature is controlled between 60-90°C for stirring in a water bath to make the polyvinyl alcohol evenly dispersed in the starch solution, and then the ground modified diatomite is added, and glycerol is added after stirring to form a uniform turbid liquid, and continuous stirring is continued for 2 hours; then sodium persulfate powder is added and continuous stirring is continued for 2 hours; finally, 0.2-1M boric acid solution is added, and after standing for 5-10 minutes, a colloidal diatomite composite gel is obtained, and the colloidal substance is injected into a mold, dried at 60°C, and stored in a desiccator for later use.

[0032] like Figure 1The pretreatment box in the step S1 shown is composed of a material guiding box 1, a filtering box 2 and a heating and drying box 3. The material guiding box is inclined and its lower end is connected to the side wall of the filtering box. A feeding port 6 is arranged on the top of the upper end of the material guiding box. A first rotating shaft 4 is rotatably connected to the material guiding box. One end of the first rotating shaft is connected to a first conveying motor 5 fixed on the outer wall of the material guiding box and a first spiral blade is mounted thereon. Therefore, the filtering box and the heating and drying box are detachably connected up and down. A first through groove is provided at the connection between the filtering box and the material guiding box, and the filtering box is connected to the material guiding box through the first through groove. A cover plate 15 is detachably connected to the top of the filtering box, and a rotary elution mechanism is arranged at the bottom of the cover plate 15. An arc-shaped screen filter plate 1 with a 100-mesh screen is installed at the bottom of the filtering box. 6. The filter box is connected with the heating and drying box through the sieve holes provided on the arc-shaped sieve filter plate. The heating and drying box is suspended and supported by a plurality of columns provided at the bottom. A second screw conveying mechanism is provided in the lower end of the heating and drying box. The bottom of the heating and drying box is in an arc shape matching the second screw conveying mechanism. A material guide cover 19 connected with the material guide cover is provided on the right side wall of the lower end of the heating and drying box. The material guide cover is provided horizontally, and the bottom surface thereof is flush with the lower end of the heating and drying box. A second through groove is provided on the side wall of the lower end of the heating and drying box facing the material guide cover. The heating and drying box is connected with the material guide cover through the second through groove. A discharge port 21 is provided at the bottom of the material guide cover. A blocking mechanism is also provided in the material guide cover. The second through groove is sealed by the blocking mechanism. The pretreatment box used in the present invention can automatically complete the pretreatment of diatomite, greatly improving the processing efficiency.

[0033] like Figure 1 and Figure 2A flushing pipe 7 is arranged above the material guide box, and a plurality of flushing nozzles are connected to the bottom of the flushing pipe from left to right in sequence through a branch pipe. The flushing nozzles are installed on the top wall of the material guide box, and the branch pipes extend into the material guide box and are connected to the flushing nozzles; the rotary elution mechanism shown includes a first annular elution pipe 10, a second annular elution pipe 9, a hollow support pipe 8, a rotary motor 13, a driving gear 12 and a driven gear 11, the hollow support pipe is placed vertically and its upper end is rotatably connected to the bottom of the cover plate 15 through a bearing structure, and the upper end of the hollow support pipe passes through the cover The plate is connected to the pressure water pipe through the first mechanical sealing structure, the first annular elution pipe and the second annular elution pipe are connected to the outside of the hollow support pipe one above and one below, the first annular elution pipe and the second annular elution pipe are both connected to the hollow support pipe and rotate under the drive of the hollow support pipe, the bottom of the first annular elution pipe and the second annular elution pipe are provided with a plurality of elution nozzles, the driven gear is sleeved on the outer wall of the upper end of the hollow support pipe, the rotating motor is installed on the top of the cover plate, and the driving gear is installed on the output shaft of the rotating motor and meshes with the driven gear. The present invention is provided with a flushing nozzle in the material guide box and a rotating elution mechanism in the filter box, and the diatomaceous earth remaining in the material guide box and the filter box can be completely flushed into the heating and drying box through the flushing nozzle and the rotating elution mechanism, and this structure plays a role in saving resources.

[0034] like Figure 1 The second spiral conveying mechanism shown includes a second rotating shaft 18, a second spiral blade and a second conveying motor 17. The second rotating shaft is horizontally rotatably connected in the lower end of the heating and drying box, and its left end is connected to the second conveying motor installed on the left outer wall of the heating and drying box. The second spiral blade is sleeved on the second rotating shaft in the heating and drying box, and the right end of the second rotating shaft extends into the second through groove and is connected to the blocking mechanism. The blocking mechanism is connected by a hollow rotating shaft 23, a rubber plug 20 and a sealing electric cylinder 22. The hollow rotating shaft is horizontally arranged in the material guide cover, and its left end is connected to the second rotating shaft and rotates therewith. The right end of the second rotating shaft is connected to the second mechanical sealing structure arranged on the right end side wall of the material guide cover. The hollow rotating shaft is rotatably connected with a rubber plug, which is piston-type connected in the material guide cover and connected to the sealing electric cylinder installed on the outer wall of the heating and drying box. Driven by the sealing electric cylinder, the rubber plug translates along the hollow rotating shaft and seals the second through groove.

[0035] The above-mentioned second mechanical sealing structure is connected to a heating medium extraction pipeline and a heating medium delivery pipeline. A feed channel and a reflux channel connected to the heating medium extraction pipeline and the heating medium delivery pipeline are respectively provided in the hollow rotating shaft and the second rotating shaft. A circulation channel is also provided in the second spiral blade. One end of the circulation channel is connected to the feed channel, and the other end of the circulation channel is connected to the reflux channel. A temperature sensor is also arranged in the heating and drying box.

[0036] like Figure 2 In the step S2 shown, a pressure protection valve is installed on the top of the vacuum drying oven, and the pressure protection valve includes a first valve body 24, a second valve body 25, a valve core 30, a spring 31, a pull rod electric cylinder 27, a pull rod 28 and a pull plate 29. One end of the first valve body is fixed on the top of the vacuum drying oven and is connected thereto, and the other end of the first valve body is fixed on the outer wall of the second valve body. A plurality of through holes 26 are provided on the end of the second valve body extending into the first valve body, and the other end of the second valve body is open. The valve core is connected to the second valve body through a spring and faces the through holes. A pressure relief hole 32 is provided on the side wall of the second valve body in the first valve body, and the pressure relief hole is sealed by the valve core. The pull rod electric cylinder is installed on one end of the second valve body extending into the first valve body, and the output shaft end of the pull rod electric cylinder extends into the second valve body and is connected to the pull rod, which passes through the valve core and is connected to the pull plate, and the valve core is piston-connected to the pull rod and the second valve body. The present invention installs a pressure protection valve on the top of the vacuum drying box, which plays a role of self-protection, prevents unnecessary damage to the structure caused by excessive internal and external pressure difference, and plays a role of increasing practical performance. In addition, the present invention adopts the above structure to not only automatically release pressure, but also release pressure by manually opening the pull rod electric cylinder.

[0037] Embodiment 1:

[0038] The preparation method of the diatomaceous earth sustained-release sodium persulfate gel composite material provided by the example of the present invention comprises the following steps:

[0039] A. Pass the diatomaceous earth raw material through a 100-mesh sieve, then wash it with deionized water to remove impurities, and dry it at 45-50°C for later use.

[0040] B. Take 50 kg of dried diatomaceous earth, add an appropriate amount of 5% sodium hydroxide solution and stir at 100°C for 2 hours to form a uniform turbid liquid, then inject it into a mold and place it in a vacuum drying oven at 70°C for 24 hours to obtain hard modified diatomaceous earth, which is then ground for later use.

[0041] C. Weigh 2 kg of soluble starch and dissolve it in 50 L of distilled water, and continue to stir to ensure that the starch is evenly dispersed in the water; weigh 2 kg of polyvinyl alcohol and add it to the starch solution, stir in a water bath at 80° C. to evenly disperse the polyvinyl alcohol in the starch solution, then add 2 kg of ground modified diatomaceous earth, continue to stir to form a uniform turbid solution, add 2 L of glycerol, and continue to stir for 2 hours; then add 2 kg of sodium persulfate powder and continue to stir for 2 hours; finally, add 5 L of 0.2 M boric acid solution in batches, let it stand for 5-10 minutes, and obtain a colloidal diatomaceous earth composite gel, inject the colloidal substance into a mold, dry it, and store it in a desiccator for later use.

[0042] In actual remediation, paraffin slow-release materials are added to the polluted water, such as Figure 4 As shown, after the paraffin slow-release material is added to the water body, the oxidant is released very quickly and the maximum value can be reached in a very short time. However, the groundwater body is flowing and the oxidant release time is very short. Therefore, in order to achieve the repair effect during actual repair, it is necessary to frequently replenish the paraffin slow-release material. This method greatly increases the cost. This embodiment 1 is different. The oxidant is released very quickly, and the oxidant release time is significantly improved compared to the conventional paraffin slow-release material. Therefore, it can be seen from the comparison that the slow-release material of embodiment 1 prepared in this patent application has better performance than the existing slow-release materials such as paraffin.

[0043] Embodiment 2:

[0044] The preparation method of the diatomaceous earth sustained-release sodium persulfate gel composite material provided by the example of the present invention comprises the following steps:

[0045] A. Pass the diatomaceous earth raw material through a 100-mesh sieve, then wash it with deionized water to remove impurities, and dry it at 45-50°C for later use.

[0046] B. Take 50 kg of dried diatomaceous earth, add an appropriate amount of 5% sodium hydroxide solution and stir at 100°C for 2 hours to form a uniform turbid liquid, then inject it into a mold and place it in a vacuum drying oven at 70°C for 24 hours to obtain hard modified diatomaceous earth, which is then ground for later use.

[0047] C. Weigh 5 kg of soluble starch and dissolve it in 50 L of distilled water, and continue to stir to ensure that the starch is evenly dispersed in the water; weigh 5 kg of polyvinyl alcohol and add it to the starch solution, stir in a water bath at 80° C. to evenly disperse the polyvinyl alcohol in the starch solution, then add 2 kg of ground modified diatomaceous earth, continue to stir to form a uniform turbid solution, add 2 L of glycerol, and continue to stir for 2 hours; then add 2 kg of sodium persulfate powder, and continue to stir for 2 hours; finally, add 5 L of 0.2 M boric acid solution in succession, let it stand for 5-10 minutes, and a colloidal diatomaceous earth composite gel is obtained, and the colloidal substance is injected into a mold, dried, and stored in a desiccator for later use.

[0048] like Figure 4 As shown, the release time of Example 2 prepared in the present application is significantly improved when releasing the oxidant compared to conventional paraffin sustained-release materials. Therefore, it can be seen from the comparison that the sustained-release material of Example 2 prepared in the present patent application has better performance than existing sustained-release materials such as paraffin.

[0049] Embodiment 3:

[0050] The preparation method of the diatomaceous earth sustained-release sodium persulfate gel composite material provided by the example of the present invention comprises the following steps:

[0051] A. Pass the diatomaceous earth raw material through a 100-mesh sieve, then wash it with deionized water to remove impurities, and dry it at 45-50°C for later use.

[0052] B. Take 50 kg of dried diatomaceous earth, add an appropriate amount of 5% sodium hydroxide solution and stir at 100°C for 2 hours to form a uniform turbid liquid, then inject it into a mold and place it in a vacuum drying oven at 70°C for 24 hours to obtain hard modified diatomaceous earth, which is then ground for later use.

[0053] C. Weigh 10 kg of soluble starch and dissolve it in 50 L of distilled water, and continue to stir to ensure that the starch is evenly dispersed in the water; weigh 5 kg of polyvinyl alcohol and add it to the starch solution, stir in a water bath at 80° C. to evenly disperse the polyvinyl alcohol in the starch solution, then add 5 kg of ground modified diatomaceous earth, continue to stir to form a uniform turbid solution, add 2 L of glycerol, and continue to stir for 2 hours; then add 2 kg of sodium persulfate powder, and continue to stir for 2 hours; finally, add 5 L of 0.2 M boric acid solution in succession, let it stand for 5-10 minutes, and a colloidal diatomaceous earth composite gel is obtained, and the colloidal substance is injected into a mold, dried, and stored in a desiccator for later use.

[0054] like Figure 4 As shown, the release time of Example 3 prepared in the present application is greatly prolonged when releasing the oxidant compared to conventional paraffin sustained-release materials. Therefore, it can be seen from the comparison that the sustained-release material of Example 3 prepared in the present patent application has better performance than existing sustained-release materials such as paraffin.

[0055] Comparative Examples 1-3, such as Figure 4 As shown, although Example 1 releases the oxidant very quickly after being added to the water body and can reach the maximum value in a very short time, the duration cannot meet the demand. Example 2 is different. Although the speed of releasing the oxidant after being added to the water body is insufficient compared with Example 1, it can still meet the demand, and the duration is much better than Example 1. In addition, the release speed of Example 3 is very slow compared with Example 2, and the maximum value that can be reached is also lower than that of Example 2. Therefore, in comparison, the ratio described in Example 2 is the optimal solution.

[0056] In summary, the diatomaceous earth in the present invention has the characteristics of high surface area, and the diatomaceous earth after alkali modification can enhance its adsorption capacity, increase the loading amount of sodium persulfate, and can improve the mechanical strength of the gel material after being embedded, and increase the service life of the sustained-release material; and the present invention forms a gel coating by polyvinyl alcohol / starch, so as to realize the slow release of sodium persulfate; and the present invention uses polyvinyl alcohol and starch as gel materials and diatomaceous earth as a carrier, which is environmentally friendly and low in cost, and can be used as a filling material of a permeable reaction barrier, and is convenient to replace.

[0057] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material, characterized in that: Specifically, the following steps are included: S1: Pretreatment of diatomite: The diatomite raw material is sent to a pretreatment box, first passed through a 100-mesh sieve, then washed with deionized water to remove impurities, and finally dried at 45-50°C for use; S2: Preparation of modified diatomite: Take an appropriate amount of the dried diatomite prepared in step S1, add an appropriate amount of sodium hydroxide solution, stir at 100°C for 2h to form a uniform turbid liquid, then inject it into a mold, place it in a vacuum drying oven at 70°C for 24h to obtain hard modified diatomite, and grind it for later use; S3: Preparation of diatomite slow-release oxidant gel composite material: weigh 4%-20% soluble starch, 4%-10% polyvinyl alcohol, 4%-10% modified diatomite and 2%-5% sodium persulfate powder in proportion, first dissolve the soluble starch in distilled water, and use a stirring tank to continuously stir to ensure that the soluble starch is evenly dispersed in the water, then add polyvinyl alcohol to the soluble starch solution, control the temperature between 60-90°C and stir in a water bath to make the polyvinyl alcohol evenly dispersed in the soluble starch solution, then add the ground modified diatomite, stir to form a uniform turbid liquid, then add glycerol, and continue stirring for 2h; then add sodium persulfate powder, and continue stirring for 2h; finally, add 0.2-1M boric acid solution, let it stand for 5-10min, and then a colloidal diatomite composite gel is obtained, the colloidal substance is injected into a mold, dried at 60°C, and stored in a desiccator for later use.

2. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 1, characterized in that: In the step S3, the soluble starch polyvinyl alcohol, modified diatomaceous earth and sodium persulfate powder weighed in proportion are 20%, 10%, 10% and 4% respectively, and the boric acid solution is preferably a 0.2M boric acid solution.

3. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 1, characterized in that: The pretreatment box in step S1 is composed of a material guide box (1), a filter box (2) and a heating and drying box (3). The material guide box is inclined and its lower end is connected to the side wall of the filter box. A feed port (6) is provided at the top of the upper end of the material guide box. A first rotating shaft (4) is rotatably connected inside the material guide box. One end of the first rotating shaft is connected to a first conveying motor (5) fixed on the outer wall of the material guide box and a first spiral blade is mounted thereon. Therefore, the filter box and the heating and drying box are detachably connected up and down. A first through groove is provided on the filter box at a connection relative to the material guide box. The filter box is connected to the material guide box through the first through groove. A cover plate (15) is detachably connected to the top of the filter box. A rotary elution mechanism is provided at the bottom of the cover plate (15). An arc with a 100-mesh screen is installed at the bottom of the filter box. The heating and drying box body is provided with a plurality of vertical columns arranged at the bottom thereof for suspension support. A second spiral conveying mechanism is arranged in the lower end of the heating and drying box body. The bottom of the heating and drying box body is in an arc shape matching the second spiral conveying mechanism. A material guide hood body (19) connected thereto is arranged on the right end side wall of the lower end of the heating and drying box body. The material guide hood body is arranged horizontally, and its bottom surface is flush with the lower end of the heating and drying box body. A second through groove is arranged on the side wall of the lower end of the heating and drying box body at a position facing the material guide hood body. The heating and drying box body is connected with the material guide hood body through the second through groove. A material outlet (21) is arranged at the bottom of the material guide hood body. A sealing mechanism is also arranged in the material guide hood body. The second through groove is sealed by the sealing mechanism.

4. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 3, characterized in that: A flushing pipe (7) is arranged above the material guide box, and a plurality of flushing nozzles are sequentially connected to the bottom of the flushing pipe from left to right through branch pipes. The flushing nozzles are installed on the top wall of the material guide box, and the branch pipes extend into the material guide box and are connected to the flushing nozzles.

5. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 3, characterized in that: The rotary elution mechanism comprises a first annular elution pipe (10), a second annular elution pipe (9), a hollow support pipe (8), a rotary motor (13), a driving gear (12) and a driven gear (11); the hollow support pipe is placed vertically and its upper end is rotatably connected to the bottom of the cover plate (15) through a bearing structure; the upper end of the hollow support pipe passes through the cover plate and is connected to the pressure water pipe through a first mechanical sealing structure; the first annular elution pipe and the second annular elution pipe are connected to the outer side of the hollow support pipe in an upper and lower manner; the first annular elution pipe and the second annular elution pipe are both connected to the hollow support pipe and rotated under the drive of the hollow support pipe; a plurality of elution nozzles are arranged at the bottom of the first annular elution pipe and the second annular elution pipe; the driven gear is sleeved on the outer wall of the upper end of the hollow support pipe; the rotary motor is mounted on the top of the cover plate; the driving gear is mounted on the output shaft of the rotary motor and meshes with the driven gear.

6. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 3, characterized in that: The second spiral conveying mechanism comprises a second rotating shaft (18), a second spiral blade and a second conveying motor (17). The second rotating shaft is horizontally rotatably connected in the lower end of the heating and drying box body, and its left end is connected to the second conveying motor installed on the left outer wall of the heating and drying box body. The second spiral blade is sleeved on the second rotating shaft in the heating and drying box body, and the right end of the second rotating shaft extends into the second through groove and is connected to the blocking mechanism. The blocking mechanism is connected by a hollow rotating shaft (23), a rubber plug (20) and a sealing electric cylinder (22). The hollow rotating shaft is horizontally arranged in the material guide cover body, and its left end is connected to the second rotating shaft and rotates therewith. The right end of the second rotating shaft is connected to a second mechanical sealing structure arranged on the right end side wall of the material guide cover body. The hollow rotating shaft is rotatably connected with a rubber plug. The rubber plug is piston-connected in the material guide cover body and connected to the sealing electric cylinder installed on the outer wall of the heating and drying box body. The rubber plug is translated along the hollow rotating shaft under the drive of the sealing electric cylinder and seals the second through groove.

7. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 6, characterized in that: The second mechanical sealing structure is connected to a heating medium extraction pipeline and a heating medium delivery pipeline. A feed channel and a reflux channel connected to the heating medium extraction pipeline and the heating medium delivery pipeline are respectively provided in the hollow rotating shaft and the second rotating shaft. A circulation channel is also provided in the second spiral blade. One end of the circulation channel is connected to the feed channel, and the other end of the circulation channel is connected to the reflux channel. A temperature sensor is also provided in the heating and drying box.

8. The method for preparing a diatomaceous earth sustained-release sodium persulfate gel composite material according to claim 1, characterized in that: In step S2, a pressure protection valve is installed on the top of the vacuum drying oven, and the pressure protection valve includes a first valve body (24), a second valve body (25), a valve core (30), a spring (31), a pull rod electric cylinder (27), a pull rod (28) and a pull plate (29). One end of the first valve body is fixed to the top of the vacuum drying oven and is connected thereto, and the other end of the first valve body is fixed on the outer wall of the second valve body. A plurality of through holes (26) are provided on one end of the second valve body extending into the first valve body, and the other end of the second valve body is open. The valve core is connected to the second valve body through a spring and faces the through holes. A pressure relief hole (32) is provided on the side wall of the second valve body in the first valve body, and the pressure relief hole is sealed by the valve core. The pull rod electric cylinder is installed on one end of the second valve body extending into the first valve body, and the shaft end of the pull rod electric cylinder extends into the second valve body and is connected to the pull rod, which passes through the valve core and is connected to the pull plate. The valve core is piston-connected to the pull rod and the second valve body.

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