Detailed Description
The invention provides a preparation method of filter cloth for treating rare earth smelting oily wastewater, which comprises the following steps:
(1) mixing the solution of the hydrophilic substance with the nano silica sol and the cross-linking agent, and carrying out cross-linking reaction to obtain super-hydrophilic emulsion; the hydrophilic substance comprises polyvinyl alcohol and/or chitosan;
(2) and (2) soaking the blank filter cloth in the super-hydrophilic emulsion obtained in the step (1) and then drying to obtain the filter cloth for treating the rare earth smelting oily wastewater.
In the present invention, the sources of the components are not particularly limited, unless otherwise specified, and commercially available products known to those skilled in the art may be used.
The invention mixes the solution of hydrophilic substance with nanometer silica sol and cross linker to carry out cross linking reaction, and obtains super hydrophilic emulsion.
In the present invention, the hydrophilic substance includes polyvinyl alcohol and/or chitosan, preferably polyvinyl alcohol.
In the present invention, the average molecular weight of the polyvinyl alcohol is preferably 1500 to 2000, and more preferably 1700 to 1800. In the present invention, the average molecular weight of polyvinyl alcohol is limited to the above range, and the polyvinyl alcohol can be dissolved more favorably.
In the invention, the deacetylation degree of the chitosan is preferably 80-95%, and more preferably 85-90%. The invention limits the deacetylation degree of chitosan in the above range, and can improve the solubility of chitosan.
In the present invention, when the hydrophilic substance is polyvinyl alcohol, the solvent of the solution of the hydrophilic substance is preferably high-purity water. In the invention, the high-purity water can avoid the influence of impurities in water on the performance of the filter cloth.
In the present invention, when the hydrophilic substance is polyvinyl alcohol, the mass fraction of polyvinyl alcohol in the solution of the hydrophilic substance is preferably 1 to 10%, more preferably 2 to 9%, more preferably 3 to 8%, and most preferably 4 to 6%. In the present invention, the mass fraction of polyvinyl alcohol in the solution of the hydrophilic substance is limited to the above range, and the polyvinyl alcohol can be dissolved more sufficiently.
In the present invention, when the hydrophilic substance is polyvinyl alcohol, the method for preparing the solution of the hydrophilic substance is preferably: adding polyvinyl alcohol into high-purity water at 90-100 ℃, and standing for defoaming. In the present invention, the temperature of the high purity water is limited to the above range, and the polyvinyl alcohol can be dissolved more sufficiently. The standing and defoaming time is not specially limited, and no bubbles are generated in the polyvinyl alcohol solution.
In the present invention, when the hydrophilic substance is polyvinyl alcohol and chitosan, the mass fraction of polyvinyl alcohol in the solution of the hydrophilic substance is preferably 0.5 to 8%, more preferably 1 to 6%, more preferably 2 to 5%, and most preferably 3 to 4%.
In the present invention, when the hydrophilic substance is polyvinyl alcohol and chitosan, the mass fraction of chitosan in the solution of the hydrophilic substance is preferably 0.1 to 2.5%, more preferably 0.5 to 2.0%, and most preferably 1.0 to 1.5%. The present invention limits the mass fraction of chitosan in the solution of the hydrophilic substance to the above range, and can dissolve the chitosan more sufficiently.
The invention limits the mass fraction of the polyvinyl alcohol and the chitosan in the solution of the hydrophilic substance within the range, can properly improve the hydrophilicity of the filter cloth, and can avoid the adverse effect on the swelling performance of the filter cloth and the film forming performance of the emulsion.
In the present invention, when the hydrophilic substance includes polyvinyl alcohol and chitosan, the preparation of the solution of the hydrophilic substance is preferably: mixing polyvinyl alcohol and high-purity water to obtain a polyvinyl alcohol solution; mixing chitosan and acetic acid aqueous solution to obtain chitosan solution; and then mixing the polyvinyl alcohol solution and the chitosan solution to obtain a solution of the hydrophilic substance.
In the present invention, polyvinyl alcohol and high purity water are preferably mixed to obtain a polyvinyl alcohol solution. In the invention, the mass fraction of the polyvinyl alcohol solution is preferably 1-8%, more preferably 3-7%, and most preferably 4-6%.
In the invention, chitosan and acetic acid aqueous solution are preferably mixed to obtain chitosan solution. In the present invention, the mass fraction of the acetic acid aqueous solution is preferably 1 to 3%, and more preferably 2%. In the present invention, the mass fraction of the acetic acid aqueous solution is limited to the above range, and the chitosan can be dissolved more sufficiently. The method for preparing the aqueous acetic acid solution is not particularly limited in the present invention, and a solution preparation method well known to those skilled in the art may be used. In the invention, the mass fraction of the chitosan solution is preferably 1-5%, more preferably 2-4%, and most preferably 3%.
After obtaining the polyvinyl alcohol solution and the chitosan solution, the invention preferably mixes the polyvinyl alcohol solution and the chitosan solution to obtain the solution of the hydrophilic substance. In the invention, the volume ratio of the polyvinyl alcohol solution to the chitosan solution is preferably (1-9): 1, more preferably (3-7): 1, most preferably (4-6): 1.
in the present invention, the crosslinking agent preferably includes one of glutaraldehyde, diisocyanate, graphene oxide, and polyorganosilsesquioxane, and more preferably glutaraldehyde. In the present invention, the glutaraldehyde is widely available and inexpensive.
In the present invention, the mass ratio of the crosslinking agent to the hydrophilic substance is preferably (0.001 to 0.1):1, more preferably (0.005 to 0.08):1, even more preferably (0.01 to 0.06):1, and most preferably (0.02 to 0.04): 1. According to the invention, the mass ratio of the cross-linking agent to the hydrophilic substance is limited within the range, so that the cross-linking reaction can be fully carried out, and the separation performance of the filter cloth is further improved.
In the present invention, the crosslinking agent is preferably added in the form of an aqueous crosslinking agent solution. The concentration of the aqueous solution of the crosslinking agent is not particularly limited, and the mass ratio of the crosslinking agent to the hydrophilic substance is within the above range.
In the invention, the particle size of the nano silica sol is preferably 10-300 nm, more preferably 50-250 nm, more preferably 100-200 nm, and most preferably 150 nm. According to the invention, the particle size of the nano silica sol is limited in the range, so that the particle size of the nano silica sol is smaller, a micro-nano coarse structure can be formed after the nano silica sol is solidified on the filter cloth, the hydrophilicity of the filter cloth is improved, the super-hydrophilicity is achieved, and the separation effect is further improved.
In the invention, the solid content of the nano silica sol is preferably 5-25%, more preferably 10-20%, and most preferably 15%. The invention limits the solid content of the nano silica sol in the range, so that the nano silica sol is dispersed more uniformly.
In the invention, the mass ratio of the nano particles to the hydrophilic substances in the nano silica sol is preferably (0.1-5) to 1, and more preferably (0.5-4.5): 1, more preferably (1 to 4):1, most preferably (2-3): 1. according to the invention, the mass ratio of the nano particles to the hydrophilic substances in the nano silica sol is limited within the range, and the content of silicon dioxide in the super-hydrophilic emulsion can be adjusted, so that the silicon dioxide is uniformly dispersed in the super-hydrophilic emulsion and is further uniformly solidified on the filter cloth, and the separation effect is further improved.
In the present invention, the mixing of the solution of the hydrophilic substance with the nanosilicon sol and the crosslinking agent is preferably: firstly, adding nano silica sol into a hydrophilic substance solution, and finally adding a cross-linking agent. In the invention, the addition rate of the nano silica sol is preferably 2-3 mL/min. The invention limits the adding speed of the nano silica sol in the range, can more uniformly disperse the nano silica sol in hydrophilic substances, and avoids agglomeration.
According to the invention, the nano silica sol is preferably added and then sequentially stirred and subjected to ultrasonic treatment. In the present invention, the stirring is preferably a glass rod stirring. In the invention, the stirring time is preferably 5-30 min. In the invention, the power of the ultrasonic wave is preferably 180-480W; the time of the ultrasonic treatment is preferably 15-30 min. The mixing mode of the invention can ensure that the components are mixed more uniformly.
In the invention, the temperature of the crosslinking reaction is preferably 20-30 ℃; the time of the crosslinking reaction is preferably 1-4 h, and more preferably 2-3 h. In the present invention, the temperature and time of the crosslinking reaction are limited to the above ranges, and the crosslinking reaction can be more sufficiently performed. In the invention, in the crosslinking reaction process, the hydrophilic substance is subjected to crosslinking reaction under the action of crosslinking, and the nano silica sol is dispersed in a crosslinked product.
In the present invention, the crosslinking reaction is preferably carried out under stirring conditions. The stirring rate is not particularly limited in the present invention, and a stirring rate known to those skilled in the art may be used.
After the crosslinking reaction is finished, the invention preferably carries out ultrasonic treatment and defoaming on the crosslinking reaction product in sequence to obtain the super-hydrophilic emulsion.
In the invention, the power of the ultrasonic wave is preferably 180-480W; the time of the ultrasonic treatment is preferably 5-15 min. In the invention, the ultrasonic wave can make the dispersion of the nano silica sol more uniform.
In the present invention, the defoaming is preferably static defoaming. The invention has no special limit on the defoaming time, and the system is ensured to have no bubbles.
After the super-hydrophilic emulsion is obtained, the blank filter cloth is soaked in the super-hydrophilic emulsion and then dried to obtain the filter cloth for treating the rare earth smelting oily wastewater.
In the present invention, the blank filter cloth is preferably subjected to cutting, water washing, absolute ethanol washing, ultrapure water washing and drying in this order before use. The size of the blank filter cloth after cutting is not specially limited and can be selected according to actual requirements. In the present invention, the number of times of each washing is preferably 3; the time for each washing is preferably 10-60 min, and more preferably 30-40 min. The invention has no special limitation on the dosage of the detergent in each washing and can be selected according to the size of the blank filter cloth. In the present invention, the washing is preferably performed under ultrasonic conditions; the power of the ultrasonic wave is preferably 180-480W. In the invention, dirt such as oil stain adhered to the surface of the blank filter cloth can be removed by washing, and adverse effect on the load of the super-hydrophilic emulsion is avoided. The invention has no special limitation on the drying temperature and time, and can ensure that the blank filter cloth is dried.
In the present invention, the blank filter cloth is preferably made of nylon, non-woven fabric, polypropylene filter cloth or filter cotton. The preparation method of the blank filter cloth is not particularly limited, and the technical scheme of the preparation method of the filter cloth, which is well known by the technical personnel in the field, can be adopted. In a preferred embodiment of the present invention, the blank filter cloth has good acid resistance.
In the invention, the mesh number of the screen mesh of the blank filter cloth is preferably 200-500 meshes, and more preferably 300-400 meshes. The mesh number of the screen mesh of the blank filter cloth is limited in the range, so that the oil-water separation effect can be further improved.
The dosage of the super-hydrophilic emulsion is not specially limited, and the super-hydrophilic emulsion can be used without a blank filter cloth.
In the invention, the time for soaking is preferably 10-120 min, more preferably 30-100 min, and most preferably 50-70 min. The invention limits the dipping time within the range, can load more super-hydrophilic emulsion on the blank filter cloth, and further improves the separation effect.
After the impregnation is finished, the impregnated filter cloth is preferably pulled out and then dried to obtain the oil-water separation filter cloth.
In the present invention, the pulling is preferably slow pulling; the slow pulling rate is preferably 5-15 cm/min. In the invention, the slow lifting can avoid bubbles generated in the lifting process, so that pores are generated after drying, the separation effect is reduced, the thickness of the super-hydrophilic emulsion loaded on the filter cloth can be more uniform, and the separation effect is further improved.
In the invention, the drying temperature is preferably 50-100 ℃; the drying time is preferably 20-30 min. In the drying process, the solvent in the emulsion is volatilized to obtain the filter cloth for treating the rare earth smelting oily wastewater.
In the present invention, the drying is preferably performed in an oven.
According to the invention, the filter cloth is impregnated by crosslinking hydrophilic substances and nano silica sol, the nano silica sol can be well dispersed in the hydrophilic substances and can form a micro-nano coarse structure after being solidified on the filter cloth, and technological parameters such as the composition and the dosage of each component are controlled, so that the prepared filter cloth has super-hydrophilicity.
The invention provides the filter cloth for treating the rare earth smelting oily wastewater, which is prepared by the preparation method in the technical scheme.
The filter cloth for treating the rare earth smelting oily wastewater provided by the invention has an excellent oil-water separation effect.
The invention also provides application of the filter cloth for treating the rare earth smelting oily wastewater in the technical scheme in treating the rare earth smelting oily wastewater.
The filter cloth provided by the invention can be used for directly filtering and removing oil-containing components in the rare earth smelting oil-containing wastewater, and can also be prepared into a filter bag and then filtered and collected.
The preparation method of the filter bag is not particularly limited, and the technical scheme for preparing the filter bag, which is well known by the technical personnel in the field, can be adopted.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Dissolving polyvinyl alcohol (with average molecular weight of 1750 +/-50) in high-purity water at 97 ℃ to obtain a polyvinyl alcohol solution with the mass fraction of 5%, cooling, standing and defoaming;
(2) under the condition of stirring, adding chitosan (deacetylation degree is 85%) into 2% by mass of acetic acid aqueous solution, and performing ultrasonic treatment at 480W for 30min to obtain 2% by mass of chitosan solution;
(3) preparing 1.5 mass percent of glutaraldehyde aqueous solution and 20 mass percent of nano silica sol (the particle size is 10-300 nm);
(4) mixing 160mL of 5% polyvinyl alcohol solution and 40mL of 2% chitosan solution to obtain a hydrophilic substance solution (the mass fraction of polyvinyl alcohol in the hydrophilic substance solution is 4%, the mass fraction of chitosan in the hydrophilic substance solution is 0.4%, the volume ratio of the polyvinyl alcohol solution to the chitosan solution is 4:1), adding 60mL of 20% solid content nano silica sol (the mass ratio of nano particles in the nano silica sol to the total mass of polyvinyl alcohol and chitosan is 1.4:1), stirring with a glass rod, performing ultrasonic treatment at 480W for 20min, then adding 5mL of 1.5 mass percent glutaraldehyde aqueous solution (the mass ratio of the glutaraldehyde to the total mass of the polyvinyl alcohol and the chitosan is 0.009:1), carrying out crosslinking reaction for 2h at 25 ℃, carrying out ultrasonic treatment for 10min at 480W, and standing and defoaming to obtain super-hydrophilic emulsion;
(5) cutting 300 mesh nylon cloth into 10 × 10cm, ultrasonic cleaning with water, anhydrous ethanol and ultrapure water at 180W for 3 times, each time for 10min, and naturally drying;
(6) and soaking the cleaned and dried nylon cloth in the super-hydrophilic emulsion for 20min, pulling the nylon cloth at the speed of 10cm/min, transferring the nylon cloth into an oven, and drying and curing the nylon cloth at 50 ℃ for 20min to obtain the filter cloth for treating the oil-containing rare earth smelting wastewater.
The contact angle test is carried out on the filter cloth for treating the rare earth smelting oily wastewater prepared in the example 1, the contact angle of the filter cloth to water is 0 degree in the air, and the filter cloth is super-hydrophilic in the air; under water, the contact angle of the filter cloth to oil is 155.5 degrees, and the underwater super oleophobic property is achieved. The method comprises the steps of taking back extraction organic phase washing water of a certain rare earth smelting plant, representing the oil content generated by P507 and organic extracting agents such as kerosene and the like by COD content, and filtering by using the filter cloth prepared in the embodiment 1 to reduce the COD content in the waste water from 498mg/L to 57mg/L, thereby meeting the requirement of emission standard of rare earth industrial pollutants on the limit value of COD less than or equal to 70 mg/L.
Example 2
(1) Dissolving polyvinyl alcohol (with average molecular weight of 1750 +/-50) in high-purity water at 97 ℃ to obtain a polyvinyl alcohol solution with the mass fraction of 3%, cooling, standing and defoaming;
(2) preparing a glutaraldehyde aqueous solution with the mass fraction of 2.5% and nano silica sol (the particle size is 10-300 nm) with the solid content of 16%;
(3) adding 45mL of nano silica sol with the solid content of 16% into 150mL of polyvinyl alcohol solution with the mass fraction of 3% (the mass ratio of nano particles in the nano silica sol to the polyvinyl alcohol is 1.6:1), carrying out 480W ultrasonic treatment for 30min after stirring by a glass rod, then adding 10mL of glutaraldehyde aqueous solution with the mass fraction of 2.5% (the mass ratio of glutaraldehyde to the polyvinyl alcohol is 0.06:1), carrying out crosslinking reaction for 2.5h at 25 ℃, carrying out 480W ultrasonic treatment for 10min, and standing and defoaming to obtain super-hydrophilic emulsion;
(5) cutting 300 mesh non-woven fabric into 10 × 10cm, ultrasonic cleaning with water, anhydrous ethanol and ultrapure water at 180W for 3 times, each time for 10min, and naturally drying;
(6) and (3) soaking the cleaned and dried non-woven fabric in the super-hydrophilic emulsion for 30min, pulling the non-woven fabric at the speed of 10cm/min, transferring the non-woven fabric into an oven, and drying and curing the non-woven fabric at 65 ℃ for 30min to obtain the filter cloth for treating the oil-containing wastewater in the rare earth smelting.
The contact angle test is carried out on the filter cloth for treating the rare earth smelting oily wastewater prepared in the example 2, the contact angle of the filter cloth to water is 0 degree in the air, and the filter cloth is super-hydrophilic in the air; under water, the contact angle of the filter cloth to oil is 158.8 degrees, and the super oleophobic property under water is achieved. After the waste water obtained by mixing the extraction waste water and the precipitation waste water of a certain rare earth smelting plant is filtered by the filter cloth prepared in the embodiment 2, the COD content in the waste water is reduced from 789mg/L to 50mg/L, and the requirement of the emission standard of rare earth industrial pollutants on the limit value of COD less than or equal to 70mg/L is met.
In conclusion, the filter cloth for treating the rare earth smelting oily wastewater has excellent oil-water separation effect, can be directly used for treating the oily wastewater, and is simpler and more convenient to separate and good in treatment effect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.