Preparation Method of Protective Coating for Parts of Wastewater Treatment Filter Press

Abstract

The invention discloses a preparation method of a protective coating for parts of a wastewater treatment filter press, which is characterized in that the fibrous aggregate is firstly subjected to roughening, activation and dispersion pretreatment, then a ZnO curing agent is loaded on the surface of the fibrous aggregate and a SiO2-TiO2 composite porous film is coated on its surface, then Al(H2PO4)3 inorganic phosphate is prepared as the matrix material of the coating, and finally the matrix material is uniformly mixed with the fibrous aggregate coated with the porous oxide film to prepare a protective coating on the surface of the parts of the wastewater treatment filter press. The invention overcomes the problems of insufficient wear resistance and temperature resistance of the existing protective coating and complex preparation process, forms a coating preparation technology with environmentally friendly components, good coating processability, controllable curing process and excellent protective performance, and can be used in the field of environmental protection engineering.

Description

Technical Field

[0001] The present invention relates to a method for preparing a protective coating, and particularly to a method for preparing a protective coating for parts of a wastewater treatment filter press, belonging to the field of environmental protection engineering. Background Art

[0002] A filter press is a mechanical device that applies a certain pressure to the filtration object and uses a special filtration medium to allow the liquid to dialyze out. It is a commonly used solid-liquid separation device and is widely used in wastewater treatment in environmental protection engineering. The service conditions of the key parts of the filter press are very harsh and are often subject to corrosion, wear, erosion, etc. In order to improve the service life and reliability of the core components of the wastewater treatment filter press, it is necessary to carry out coating protection treatment on them. CN201811617205.9 discloses a wear-resistant filter press oil seal bushing, which includes a guide roller shaft and an oil seal bushing. One end of the guide roller shaft is slidably sleeved with an oil seal bushing. An inclined opening is fixedly arranged at the upper end of the oil seal bushing. A through hole is fixedly arranged inside the oil seal bushing. A sprayed ceramic is fixedly arranged on the inner wall surface of the oil seal bushing. After grinding and processing, a 0.25-mm ceramic spray coating is formed, which can extend the service life and maintenance time of the guide roller bearing. CN200910227880.5 discloses a method for repairing a plastic filter plate of a filter press. The worn part of the polypropylene filter plate is replaced with a modified ultra-high molecular weight polyethylene small filter plate; an epoxy resin wear-resistant material is coated on the surface and periphery of the filter plate where the small filter plate is replaced; a resistance filter cloth is pre-laid on the surface of the filter plate coated with the epoxy resin wear-resistant material. By adopting three wear-resistant strengthening measures of replacing the worn area material, coating the surface with an epoxy resin wear-resistant coating, and laying a resistance filter cloth, the damaged and scrapped plastic filter plate of the filter press is repaired in a series structure, playing the role of three "defense lines", increasing the anti-wear effect of the filter plate on fine solid particles in the filtrate, and making the normal service life of the filter plate increase by more than 3 times.

[0003] However, the current surface protection coating materials and technologies are still difficult to meet the increasing demands of parts of the wastewater treatment filter press. The organic coating has insufficient wear resistance and temperature resistance. The preparation of the ceramic coating requires high deposition temperature and special equipment and may have an adverse effect on the substrate. Therefore, it is urgent to develop a coating preparation technology with environmentally friendly components, good coating processability, controllable curing process, and excellent protection performance. Summary of the Invention

[0004] Aiming at the problems existing in the preparation of the protective coating for parts of the wastewater treatment filter press at present, the present invention first pre-treats the fiber aggregate by roughening, activating and dispersing, then loads a coating curing agent on the surface of the fiber aggregate and coats a porous oxide film on its surface, then prepares an inorganic phosphate as the matrix material of the coating, and finally mixes the matrix material and the fiber aggregate coated with the porous oxide film evenly and prepares a protective coating on the surface of the parts of the wastewater treatment filter press.

[0005] The preparation method of the protective coating for the parts of the waste water treatment filter press of the present invention is characterized by sequentially comprising the following steps:

[0006] (1) Pretreatment of the fiber aggregate of the protective coating: First, put the chopped basalt fiber into a muffle furnace and keep it at 250-350 °C for 1-2 h to remove the surface industrial paraffin; then mix the chopped basalt fiber after removing the paraffin with sulfuric acid and deionized water to form a mixed solution. By weight percentage, the chopped basalt fiber in the mixed solution accounts for 10-15%, sulfuric acid accounts for 50-60%, and the rest is deionized water; stir the mixed solution in a constant temperature water bath at 65-75 °C for 1-2 h to roughen and activate the surface of the chopped basalt fiber; then filter the mixed solution and wash the chopped basalt fiber with deionized water for 6-8 times to remove sulfuric acid, and then dry it at 100-110 °C; finally, add the chopped basalt fiber to deionized water to form a mixed solution. By weight percentage, the chopped basalt fiber accounts for 5-10%, and perform ultrasonic dispersion treatment for 30-50 min to obtain the mixed solution of the pretreated chopped basalt fiber aggregate;

[0007] (2) Loading and curing agent on the surface of the fiber aggregate of the protective coating: First, add Tween 80, heptane, and n-hexanol to deionized water to form a mixed solution. By weight percentage, Tween 80:n-hexanol = 50:50, (Tween 80 + n-hexanol):heptane = 35:65, and deionized water accounts for 10-15%; magnetically stir the mixed solution in a constant temperature water bath at 65-90 °C for 1-3 h until the solution is clarified to form a microemulsion; then add Zn(NO3)2 to the formed microemulsion, the molar concentration of Zn(NO3)2 is 0.1-0.5 mol / L, add hydrochloric acid to adjust the pH value of the solution to 3-6, magnetically stir in a constant temperature water bath at 65-90 °C for 1-3 h, and then let it stand for 6-12 h to form Zn(OH)2 sol; finally, drop the Zn(OH)2 sol into the mixed solution of the pretreated chopped basalt fiber aggregate that has been prepared. The molar ratio of the chopped basalt fiber to the Zn(OH)2 sol is 1:(1-1.2), magnetically stir in a constant temperature water bath at 65-90 °C for 1-3 h, after aging for 24 h, Zn(OH)2 is adsorbed on the surface of the chopped basalt fiber aggregate, wash it 3-4 times with absolute ethanol and then filter, then dry it at 100-120 °C, and calcine it at 400 °C - 500 °C for 1-2 h to obtain the chopped basalt fiber aggregate with ZnO curing agent loaded on the surface;

[0008] (3) Coating the surface of fiber aggregate loaded with curing agent with an oxide film: Add tetrabutyl titanate and tetraethyl orthosilicate into absolute ethanol and deionized water to prepare a solution. The molar percentage concentration of tetrabutyl titanate in the solution is 1% - 5%, and the molar percentage concentration of tetraethyl orthosilicate is 1% - 5%. The rest is absolute ethanol and deionized water, and the volume ratio of absolute ethanol to deionized water is 1:(2 - 3); Add hydrochloric acid to adjust the pH value of the solution to 4 - 6, and magnetically stir in a constant temperature water bath at 65 - 85 °C for 3 - 8 h to form a Si(OH)4 / Ti(OH)4 mixed sol; Add polyacrylamide and ethylene glycol to the mixed sol, and the addition amounts are 0.1% - 0.6% and 10% - 30% of the mixed sol by weight respectively, and magnetically stir in a constant temperature water bath at 65 - 85 °C for 1 - 3 h until it becomes clear. Cool the clear sol to 40 - 48 °C, and add short-cut basalt fiber aggregate with ZnO curing agent loaded on its surface. The weight ratio of the clear sol to the short-cut basalt fiber aggregate is (2 - 3):1; Then dropwise add 1,2-epoxypropane, and the addition amount is 4% - 8% of the mixture of basalt fiber aggregate and clear sol by weight, and magnetically stir for 2 - 5 min; Then place it at the same temperature for 24 h for aging to form a phase-separated gel composed of a PAAm-rich phase and a water-rich phase. Polyacrylamide adsorbs on the SiO2-TiO2 oligomer through hydrogen bonds to form a PAAm-rich phase, and the hydrophobic groups of polyacrylamide repel the water phase and cause the formation of a water-rich phase; Wash the gel 3 - 4 times with absolute ethanol and then filter it, then heat it to 100 - 110 °C at a heating rate of 1 - 4 °C / min and keep it warm for 1 - 2 h for drying, and then heat it to 500 °C - 600 °C at a heating rate of 1 - 4 °C / min and calcine it for 1 - 2 h to remove organic substances, so as to form a SiO2-TiO2 composite porous film on the surface of the short-cut basalt fiber aggregate loaded with ZnO curing agent. The pore diameter in the composite porous film is 0.6 - 2.5 μm, and the specific surface area is 10 - 25 m 2 / g;

[0009] (4) Preparation of the matrix material of the protective coating: Add aluminum hydroxide and phosphoric acid into a beaker according to a molar ratio of (3 - 3.1):1, and place the beaker in a constant temperature water bath at 90 - 98 °C and magnetically stir for 1 - 3 h until it becomes a colorless solution, that is, the matrix material of the protective coating with the phase of Al(H2PO4)3 is obtained;

[0010] (5) Preparation of protective coating: Mix the matrix material of the protective coating with the chopped basalt fiber aggregate loaded with ZnO curing agent and coated with SiO2-TiO2 composite porous membrane according to the weight percentage of 10:(0.5~1.5), and stir at room temperature for 30~60 min to make the coating slurry; The coating slurry should be coated within 36 h. By means of air spraying, the coating slurry is coated on the surface of the parts of the wastewater treatment filter press to be protected, and placed in the air for more than 36 h until the weight loss rate of the parts is less than 0.15 g / (m 2 ·h), then the curing of the protective coating is completed.

[0011] The method for preparing the protective coating for the parts of the wastewater treatment filter press of the present invention is further characterized in that:

[0012] (1) The diameter of the chopped basalt fiber is 10~13 μm, and the length is 100~130 μm; The stirring rate during the coarsening and activation of the basalt fiber is 100~200 r / min, and the sulfuric acid used is of analytical purity; The ultrasonic frequency and power during the ultrasonic dispersion treatment are 40 kHz and 100 W respectively;

[0013] (2) Tween 80, heptane, n-hexanol, Zn(NO3)2, hydrochloric acid, and absolute ethanol used during the treatment of loading the curing agent on the surface of the fiber aggregate of the protective coating are all of analytical purity;

[0014] (3) Tetrabutyl titanate, tetraethyl silicate, hydrochloric acid, polyacrylamide, ethylene glycol, 1,2-epoxypropane, and absolute ethanol used during the coating of the oxide film on the surface of the fiber aggregate loaded with the curing agent are all of analytical purity;

[0015] (4) Aluminum hydroxide and phosphoric acid used during the preparation of the matrix material of the protective coating are all of analytical purity;

[0016] (5) During the preparation of the protective coating, the stirring rate of the coating slurry is 100~150 r / min; The air pressure during air spraying is controlled at 0.5 MPa, the spraying amount of the coating slurry is controlled at 180~200 ml / min, the spraying distance is 150~200 mm, the gun moving speed is 30~40 mm / s, the spraying width is 100~150 mm, the overlapping rate of the spraying width of adjacent strokes is 20%~30%, and the spraying is carried out 2~3 times.

[0017] The advantages of the present invention are as follows: (1) In the present invention, the ZnO curing agent is loaded on the surface of chopped basalt fibers, and a porous SiO2-TiO2 composite oxide film is coated on its surface, which can make the curing agent slowly released, avoiding the problems of rapid curing of the coating to form cracks or even inability to coat. (2) In the present invention, the composite oxide film can also improve the physical and chemical compatibility between the coating matrix material Al(H2PO4)3 and the basalt fibers, thereby preparing a complete and well-performing coating. (3) Basalt fibers have good heat resistance, wear resistance and corrosion resistance, which can enhance the service performance of the protective coating. (4) With the basalt fiber aggregate as the core, the sol-gel method is used to load the curing agent on the surface of the basalt fiber aggregate, and the loaded ZnO curing agent can be evenly dispersed by using the fiber aggregate, avoiding the problem of uneven curing degree caused by the agglomeration of the curing agent. (5) The phase of the protective coating matrix material in the present invention is Al(H2PO4)3, which is an inorganic coating with environmentally friendly components and good high-temperature and corrosion resistance. (6) In the present invention, roughening and activation treatment is adopted, and the surface inertness of the basalt fibers is reduced, enabling them to combine well with the curing agent. Brief Description of the Drawings

[0018] Figure 1 Schematic diagram of the preparation method of the protective coating for wastewater treatment filter press parts of the present invention. Detailed Embodiments

[0019] Example 1: The protective coating for wastewater treatment filter press parts is prepared according to the following steps:

[0020] (1) Pretreatment of the fiber aggregate of the protective coating: First, put the chopped basalt fibers into a muffle furnace and keep them at 260 °C for 2 h to remove the surface industrial paraffin. The diameter of the chopped basalt fibers is 10 μm and the length is 112 μm. Then, mix the paraffin-removed chopped basalt fibers with analytical pure sulfuric acid and deionized water to form a mixed solution. By weight percentage, the chopped basalt fibers in the mixed solution account for 10%, the sulfuric acid accounts for 53%, and the rest is deionized water. Stir the mixed solution in a constant temperature water bath at 65 °C for 1 h to roughen and activate the surface of the chopped basalt fibers. Then filter the mixed solution and wash the chopped basalt fibers 6 times with deionized water to remove the sulfuric acid, and then dry at 100 °C. Finally, add the chopped basalt fibers to deionized water to form a mixed solution. By weight percentage, the chopped basalt fibers account for 6%, and ultrasonic dispersion treatment is carried out for 30 min to obtain the mixed solution of the pretreated chopped basalt fiber aggregate. The ultrasonic frequency and power during ultrasonic dispersion treatment are 40 kHz and 100 W respectively;

[0021] (2)The surface of the fiber aggregate of the protective coating is loaded with a curing agent: First, Tween 80, heptane, and n-hexanol are added to deionized water to form a mixed solution. By weight percentage, Tween 80: n-hexanol = 50:50, (Tween 80 + n-hexanol): heptane = 35:65, and deionized water accounts for 10%; the mixed solution is magnetically stirred in a constant temperature water bath at 70 °C for 1 h until the solution is clear to form a microemulsion; then Zn(NO3)2 is added to the formed microemulsion, and the molar concentration of Zn(NO3)2 is 0.1 mol / L. Hydrochloric acid is added to adjust the pH value of the solution to 4, and it is magnetically stirred in a constant temperature water bath at 65 °C for 2 h, and then left for 8 h to form Zn(OH)2 sol; finally, the Zn(OH)2 sol is dropped into the mixed solution of the prepared pretreated chopped basalt fiber aggregate. The molar ratio of the chopped basalt fiber to the Zn(OH)2 sol is 1:1, and it is magnetically stirred in a constant temperature water bath at 65 °C for 1 h. After aging for 24 h, Zn(OH)2 is adsorbed on the surface of the chopped basalt fiber aggregate, washed 3 times with absolute ethanol and then filtered, and then dried at 100 °C and calcined at 400 °C for 1 h to obtain the chopped basalt fiber aggregate with ZnO curing agent loaded on the surface; Tween 80, heptane, n-hexanol, Zn(NO3)2, hydrochloric acid, and absolute ethanol used in the treatment of loading the curing agent on the surface of the fiber aggregate of the protective coating are all of analytical purity;

[0022] (3) Coating an oxide film on the surface of fiber aggregate loaded with a curing agent: Add tetrabutyl titanate and tetraethyl orthosilicate into absolute ethanol and deionized water to prepare a solution. The molar percentage concentration of tetrabutyl titanate in the solution is 2%, and the molar percentage concentration of tetraethyl orthosilicate is 2.5%. The rest is absolute ethanol and deionized water, and the volume ratio of absolute ethanol to deionized water is 1:2. Add hydrochloric acid to adjust the pH value of the solution to 4, and magnetically stir for 3 h in a constant temperature water bath at 70 °C to form a Si(OH)4 / Ti(OH)4 mixed sol. Add polyacrylamide and ethylene glycol to the mixed sol, and the addition amounts are 0.2% and 12% by weight percentage of the mixed sol respectively, and magnetically stir for 1 h in a constant temperature water bath at 65 °C until it becomes clear. Cool the clear sol to 40 °C, and add short-cut basalt fiber aggregate with ZnO curing agent loaded on its surface. The weight ratio of the clear sol to the short-cut basalt fiber aggregate is 2:1. Then dropwise add 1,2-epoxypropane, and the addition amount is 4% by weight percentage of the mixture of basalt fiber aggregate and clear sol, and magnetically stir for 2 min. Then place it at the same temperature for 24 h for aging to form a phase-separated gel composed of a PAAm-rich phase and a water-rich phase. Polyacrylamide adsorbs on the SiO2-TiO2 oligomer through hydrogen bonds to form a PAAm-rich phase, and the hydrophobic groups of polyacrylamide repel the water phase and cause the formation of a water-rich phase. Wash the gel 3 times with absolute ethanol and then filter it. Then heat it to 100 °C at a heating rate of 1 °C / min and keep it warm for 1 h for drying, and then heat it to 500 °C at a heating rate of 1 °C / min and calcine for 2 h to remove organic substances, so as to form a SiO2-TiO2 composite porous film on the surface of the short-cut basalt fiber aggregate loaded with ZnO curing agent. The pore size in the composite porous film is 0.6 - 2.5 μm, and the specific surface area is 14 m 2 / g; The tetrabutyl titanate, tetraethyl silicate, hydrochloric acid, polyacrylamide, ethylene glycol, 1,2-epoxypropane, and absolute ethanol used for coating the oxide film on the surface of the fiber aggregate loaded with the curing agent are all of analytical purity;

[0023] (4) Preparation of the matrix material for the protective coating: Add aluminum hydroxide and phosphoric acid into a beaker according to a molar ratio of 3:1. Both the used aluminum hydroxide and phosphoric acid are of analytical purity. Place the beaker in a constant temperature water bath at 90 °C and magnetically stir for 1.5 h until it becomes a colorless solution, that is, obtain the matrix material for the protective coating with the phase of Al(H2PO4)3;

[0024] (5) Preparation of protective coating: Mix the matrix material of the protective coating with the short-cut basalt fiber aggregate loaded with ZnO curing agent and coated with SiO2-TiO2 composite porous membrane in a weight percentage of 10:0.5, and stir at room temperature for 35 min to make the coating slurry, with a stirring rate of 100 r / min; The coating slurry should be applied within 36 h. By means of air spraying, the coating slurry is applied to the surface of the parts of the wastewater treatment filter press to be protected. When air spraying, the air pressure is controlled at 0.5 MPa, the spraying volume of the coating slurry is controlled at 180 ml / min, the spraying distance is 150 mm, the gun moving speed is 30 mm / s, the spraying width is 110 mm, the overlapping rate of the spraying width of adjacent strokes is 22%, and the spraying is carried out 2 times. Then it is placed in the air for more than 36 h until the weight loss rate of the parts is less than 0.15 g / (m 2 ·h), then the curing of the protective coating is completed.

[0025] Example 2: Prepare the protective coating for the parts of the wastewater treatment filter press according to the following steps:

[0026] (1) Pretreatment of the fiber aggregate of the protective coating: First, put the short-cut basalt fiber into a muffle furnace and keep it at 300 °C for 2 h to remove the surface industrial paraffin. The diameter of the short-cut basalt fiber is 12 μm and the length is 130 μm; Then, mix the short-cut basalt fiber after removing paraffin with analytical pure sulfuric acid and deionized water to form a mixed solution. By weight percentage, the short-cut basalt fiber in the mixed solution accounts for 15%, the sulfuric acid accounts for 55%, and the rest is deionized water; Stir the mixed solution in a constant temperature water bath at 75 °C for 2 h to roughen and activate the surface of the short-cut basalt fiber; Then filter the mixed solution and wash the short-cut basalt fiber 7 times with deionized water to remove sulfuric acid, and then dry it at 110 °C; Finally, add the short-cut basalt fiber to deionized water to form a mixed solution. By weight percentage, the short-cut basalt fiber accounts for 8%, and perform ultrasonic dispersion treatment for 50 min to obtain the mixed solution of the short-cut basalt fiber aggregate after pretreatment; The ultrasonic frequency and power during ultrasonic dispersion treatment are 40 kHz and 100 W respectively;

[0027] (2) The surface of the fiber aggregate of the protective coating is loaded with a curing agent: First, Tween 80, heptane, and n-hexanol are added to deionized water to form a mixed solution. By weight percentage, Tween 80:n-hexanol = 50:50, (Tween 80 + n-hexanol):heptane = 35:65, and deionized water accounts for 15%; the mixed solution is magnetically stirred in a constant temperature water bath at 80 °C for 2 h until the solution becomes clear, thereby forming a microemulsion; then Zn(NO3)2 is added to the formed microemulsion, and the molar concentration of Zn(NO3)2 is 0.5 mol / L. Hydrochloric acid is added to adjust the pH value of the solution to 5, and it is magnetically stirred in a constant temperature water bath at 80 °C for 2 h, and then left for 10 h to form Zn(OH)2 sol; finally, the Zn(OH)2 sol is dropped into the prepared short-cut basalt fiber aggregate mixed solution that has completed pretreatment. The molar ratio of the short-cut basalt fiber to the Zn(OH)2 sol is 1:1.2, and it is magnetically stirred in a constant temperature water bath at 65-90 °C for 2 h. After aging for 24 h, Zn(OH)2 is adsorbed on the surface of the short-cut basalt fiber aggregate, washed 4 times with absolute ethanol and then filtered, and then dried at 110 °C and calcined at 450 °C for 2 h to obtain short-cut basalt fiber aggregate with ZnO curing agent loaded on the surface; Tween 80, heptane, n-hexanol, Zn(NO3)2, hydrochloric acid, and absolute ethanol used in the treatment of loading the curing agent on the surface of the fiber aggregate of the protective coating are all of analytical purity;

[0028] (3) Coating the surface of the fiber aggregate loaded with the curing agent with an oxide film: Add tetrabutyl titanate and tetraethyl orthosilicate to anhydrous ethanol and deionized water to prepare a solution. The molar percentage concentration of tetrabutyl titanate in the solution is 5%, and the molar percentage concentration of tetraethyl orthosilicate is 4%. The rest is anhydrous ethanol and deionized water, and the volume ratio of anhydrous ethanol to deionized water is 1:3. Add hydrochloric acid to adjust the pH value of the solution to 6, and magnetically stir for 7 h in a constant temperature water bath at 80 °C to form a Si(OH)4 / Ti(OH)4 mixed sol. Add polyacrylamide and ethylene glycol to the mixed sol, and the addition amounts are 0.5% and 25% by weight percentage of the mixed sol respectively, and magnetically stir for 3 h in a constant temperature water bath at 75 °C until it becomes clear. Cool the clear sol to 48 °C, and add short-cut basalt fiber aggregate with ZnO curing agent loaded on the surface. The weight ratio of the clear sol to the short-cut basalt fiber aggregate is 3:1. Then dropwise add 1,2-epoxypropane, and the addition amount is 8% by weight percentage of the mixture of basalt fiber aggregate and the clear sol, and magnetically stir for 5 min. Then place it at the same temperature for 24 h for aging and form a phase-separated gel composed of a PAAm-rich phase and a water-rich phase. Polyacrylamide adsorbs on the SiO2-TiO2 oligomer through hydrogen bonds to form a PAAm-rich phase, and the hydrophobic groups of polyacrylamide repel the water phase and cause the formation of a water-rich phase. Wash the gel 4 times with anhydrous ethanol and then filter it, then heat it to 110 °C at a heating rate of 4 °C / min and keep it warm for 2 h for drying, and then heat it to 600 °C at a heating rate of 4 °C / min and calcine for 2 h to remove organic substances, so as to form a SiO2-TiO2 composite porous film on the surface of the short-cut basalt fiber aggregate loaded with the ZnO curing agent. The pore diameter in the composite porous film is 0.6~2.5 μm, and the specific surface area is 20 m 2 / g; The tetrabutyl titanate, tetraethyl silicate, hydrochloric acid, polyacrylamide, ethylene glycol, 1,2-epoxypropane, and anhydrous ethanol used for coating the surface of the fiber aggregate loaded with the curing agent with an oxide film are all of analytical purity;

[0029] (4) Preparation of the matrix material of the protective coating: Add aluminum hydroxide and phosphoric acid to a beaker according to a molar ratio of 3.1:1. Both the aluminum hydroxide and phosphoric acid used are of analytical purity, and place the beaker in a constant temperature water bath at 95 °C and magnetically stir for 3 h until it becomes a colorless solution, that is, a matrix material of the protective coating with the phase of Al(H2PO4)3 is obtained;

[0030] (5)Preparation of protective coating: Mix the matrix material of the protective coating with the chopped basalt fiber aggregate loaded with ZnO curing agent and coated with SiO2-TiO2 composite porous membrane at a weight ratio of 10:1, and stir at room temperature for 50 min to make the coating slurry, with a stirring rate of 150 r / min; The coating slurry should be applied within 36 h. By means of air spraying, apply the coating slurry on the surface of the wastewater treatment filter press parts to be protected. When air spraying, the air pressure is controlled at 0.5 MPa, the spraying volume of the coating slurry is controlled at 200 ml / min, the spraying distance is 200 mm, the gun moving speed is 40 mm / s, the spraying width is 150 mm, the overlapping rate of the spraying width of adjacent strokes is 25%, spray 3 times, and then place it in the air for more than 36 h until the weight loss rate of the parts is less than 0.15 g / (m 2 ·h), then the curing of the protective coating is completed.

Claims

1. A method for preparing a protective coating for wastewater treatment filter press parts, characterized in that The following steps are included in sequence: (1) Pretreatment of fiber aggregates for protective coating: First, put the chopped basalt fibers into a muffle furnace and keep them at 250-350℃ for 1-2 hours to remove the industrial paraffin on the surface; then, prepare a mixed solution of the chopped basalt fibers after the paraffin is removed with sulfuric acid and deionized water, wherein the chopped basalt fibers account for 10-15% by weight, the sulfuric acid accounts for 50-60%, and the rest is deionized water; stir the mixed solution in a constant temperature water bath at 65-75℃ for 1-2 hours to roughen and activate the surface of the chopped basalt fibers; then filter the mixed solution and wash the chopped basalt fibers with deionized water for 6-8 times to remove the sulfuric acid, and then dry them at 100-110℃; finally, add the chopped basalt fibers into deionized water to form a mixed solution, wherein the chopped basalt fibers account for 5-10% by weight, and perform ultrasonic dispersion treatment for 30-50 minutes to obtain a pretreated chopped basalt fiber aggregate mixed solution; (2) Surface loading curing agent of fiber aggregate of protective coating: first, Tween 80, heptane, and n-hexanol were added to deionized water to form a mixed solution, with the weight percentage of Tween 80: n-hexanol = 50:50, (Tween 80 + n-hexanol): heptane = 35:65, and deionized water accounting for 10-15%; the mixed solution was magnetically stirred in a constant temperature water bath at 65-90°C for 1-3 hours until the solution was clarified, thereby forming a microemulsion; then Zn (NO3)2, Zn The molar concentration of (NO3)2 is 0.1-0.5 mol / L, hydrochloric acid is added to adjust the pH value of the solution to 3-6, magnetic stirring is carried out in a constant temperature water bath at 65-90°C for 1-3 hours, and then placed for 6-12 hours to form Zn(OH)2 sol; finally, the Zn(OH)2 sol is added dropwise to the prepared pre-treated chopped basalt fiber aggregate mixed solution, the molar ratio of chopped basalt fiber to Zn(OH)2 sol is 1:(1-1.2), magnetic stirring is carried out in a constant temperature water bath at 65-90°C for 1-3 hours, and after aging for 24 hours, Zn(OH)2 is adsorbed on the surface of the chopped basalt fiber aggregate, washed 3-4 times with anhydrous ethanol, filtered, and then dried at 100-120°C, and calcined at 400-500°C for 1-2 hours to obtain chopped basalt fiber aggregate with surface loaded ZnO curing agent; (3) Coating the surface of the fiber aggregate loaded with curing agent with an oxide film: Add butyl titanate and ethyl orthosilicate into anhydrous ethanol and deionized water to prepare a solution, wherein the molar concentration of butyl titanate and ethyl orthosilicate in the solution is 1% to 5%, the molar concentration of ethyl orthosilicate is 1% to 5%, and the rest is anhydrous ethanol and deionized water, and the volume ratio of anhydrous ethanol to deionized water is 1:(2-3); add hydrochloric acid to adjust the pH value of the solution to 4-6, and stir magnetically for 3-8 hours in a constant temperature water bath at 65-85°C to form a Si(OH)4 / Ti(OH)4 mixed sol; add polyacrylamide and ethylene glycol to the mixed sol, the added amounts are 0.1-0.6% and 10-30% of the mixed sol by weight, respectively, and stir magnetically for 1-3 hours in a constant temperature water bath at 65-85°C until it becomes clear, cool the clear sol to 40-48°C, and add the surface loaded The weight ratio of the clarified sol to the chopped basalt fiber aggregate is (2-3):1; 1,2-propylene oxide is then added dropwise, the amount of which is 4-8% by weight of the mixture of the basalt fiber aggregate and the clarified sol, and magnetic stirring is performed for 2-5 minutes; then the mixture is placed at the same temperature for 24 hours for aging and a phase-separated gel consisting of a PAAm-rich phase and a water-rich phase is formed, and polyacrylamide is adsorbed on the SiO2-TiO2 oligomer through hydrogen bonds to form a PAAm-rich phase, and the hydrophobic groups of polyacrylamide repel the water phase and cause the formation of a water-rich phase; the gel is washed 3-4 times with anhydrous ethanol and filtered, and then heated to 100-110°C at a heating rate of 1-4°C / min and kept warm for 1-2 hours for drying, and then heated to 500°C-600°C at a heating rate of 1-4°C / min. ℃ calcined for 1~2h to remove organic matter, thereby forming a SiO2-TiO2 composite porous membrane on the surface of the short-cut basalt fiber aggregate loaded with ZnO curing agent. The pore size of the composite porous membrane is 0.6~2.5μm, and the specific surface area is 10~25m 2 / g; (4) Preparation of protective coating matrix material: Aluminum hydroxide and phosphoric acid were added into a beaker in a molar ratio of (3-3.1):1, and the beaker was placed in a constant temperature water bath at 90-98 °C and magnetically stirred for 1-3 h until it became a colorless solution, thereby obtaining a protective coating matrix material with a physical phase of Al(H2PO4)3; (5) Preparation of protective coating: The protective coating substrate material and the short-cut basalt fiber aggregate loaded with ZnO curing agent and coated with SiO2-TiO2 composite porous membrane are mixed in a weight percentage of 10: (0.5-1.5), and stirred at room temperature for 30-60 minutes to prepare a coating slurry; The coating slurry should be applied within 36 hours. The coating slurry should be applied to the surface of the wastewater treatment filter press parts to be protected by air spraying and placed in the air for more than 36 hours until the weight loss rate of the parts is less than 0.15g / (m 2 h) the curing of the protective coating is completed.

2. The method for preparing a protective coating for wastewater treatment filter press parts according to claim 1, further characterized by: (1) The diameter of the chopped basalt fiber is 10-13 μm, and the length is 100-130 μm. The stirring rate during the coarsening and activation of the basalt fiber is 100-200 r / min, and the sulfuric acid used is analytical grade. The ultrasonic frequency and power during the ultrasonic dispersion treatment are 40 kHz and 100 W, respectively. (2) Tween 80, heptane, n-hexanol, Zn (NO3)2, hydrochloric acid, and anhydrous ethanol used in the treatment of the fiber aggregate surface loading curing agent of the protective coating were all analytically pure; (3) The butyl titanate, ethyl silicate, hydrochloric acid, polyacrylamide, ethylene glycol, 1,2-propylene oxide, and anhydrous ethanol used in coating the oxide film on the surface of the fiber aggregate loaded with the curing agent were all analytically pure; (4) The aluminum hydroxide and phosphoric acid used in the preparation of the base material of the protective coating are both analytically pure; (5) When preparing the protective coating, the stirring rate of the coating slurry is 100~150 r / min; during air spraying, the air pressure is controlled at 0.5MPa, the spraying volume of the coating slurry is controlled at 180~200 ml / min, the spraying distance is 150~200 mm, the gun speed is 30~40mm / s, the spray width is 100~150 mm, the overlap rate of the adjacent stroke spray width is 20%~30%, and the spraying is performed 2~3 times.

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