Filter element for removing heavy metals in water and use method thereof
Technical Field
The invention belongs to the technical field of magnetic materials and the technical field of sewage heavy metal treatment, and particularly relates to a filter element for removing heavy metals in water and a using method thereof.
Background
Various industrial activities cause the entry of a number of heavy metals (such as lead, mercury, cadmium, cobalt, etc.) into the water, which have toxic effects and can accumulate in the food chain, leading to serious ecological and health risks.
In order to remove heavy metals from water, various methods have been developed, including chemical, physical, biological adsorption, and the like. Among them, filtration and adsorption are common methods, but have the following problems:
(1) in the filtering method, a filter element with a porous structure is used for filtering, but most of the existing filter elements are made of nylon, stainless steel meshes and the like, work in a severe environment and are easy to corrode.
(2) In the adsorption method, the magnetic nanoparticles have the advantages of large specific surface area, convenience in water separation, easiness in functionalization with different chemical groups and the like, so that the magnetic nanoparticles are an effective adsorbent for adsorbing heavy metals, and the adsorbent needs to be matched with a magnetic material and a magnetic field for use, so that the magnetic material adsorbs the magnetic nanoparticles under the action of the magnetic field, and the heavy metals are adsorbed and removed. Wherein, the adsorption efficiency of the magnetic nano-particles is related to the magnetic material and the magnetic field intensity. However, the current method has the following problems:
(a) at present, a rod-shaped magnetic material is used, and the adsorption efficiency of the magnetic material with the structure on magnetic nano particles under the action of a magnetic field is limited;
(b) the sewage treatment comprises static sewage treatment and dynamic sewage treatment, and when the sewage treatment capacity is large, the magnetic field needs to be improved; however, the magnetic field has a limited improvement range in the static sewage treatment at present, so that the static sewage treatment can only work in a small volume, the sewage treatment capacity is small, and the actual large-scale dynamic sewage treatment usually uses a high-gradient magnetic separator with magnetic induction leads, so that the cost is increased.
Disclosure of Invention
Aiming at the technical current situation, the invention combines filtration and adsorption, provides the filter element for removing the heavy metals in water, and can remove the heavy metals in water efficiently, economically and without secondary pollution.
The technical scheme of the invention is as follows: a filter core for removing heavy metal in water, which is characterized in that:
the filter element is of a hollow structure with two open ends, one open end is called an inlet end, and the other open end is called an outlet end;
the filter element is provided with a plurality of holes; each hole penetrates from the inner side to the outer side of the hollow structure, and the hole diameter is gradually reduced from the inner side to the outer side of the hollow structure;
the material of the filter core is soft magnetic material.
Preferably, the hollow structure has an inner diameter that decreases gradually from the inlet end to the outlet end.
As an implementation mode, the whole filter core is of a hollow table body structure, the cross section structure of the filter core is not limited, and the filter core comprises a circle, an ellipse, a triangle, a rectangle, other regular polygons and the like.
Preferably, the pore diameter of the pores is between 100um and 100 mm.
Preferably, the filter core is made of soft magnetic ferrite.
The preparation method of the filter element of the invention is not limited. As an implementation mode, the method is prepared by a 3D printing method, and specifically comprises the following steps: dispersing particles of a soft magnetic material in a premix liquid containing a solvent, a binder, a dispersant, and the like to form a slurry; and (3) obtaining a filter core blank by using the slurry through a 3D printing method, and then drying and sintering to obtain the filter core.
The method for removing heavy metals in water by using the filter element comprises the following steps:
(1) adding magnetic nanoparticles into water, wherein the magnetic nanoparticles adsorb heavy metal ions in the water;
(2) the filter core is placed in a magnetic field, and the filter core made of soft magnetic materials can adsorb magnetic nano particles under the action of the magnetic field; and (3) sealing the outlet end of the filter element, injecting the water treated in the step (1) into the hollow structure from the inlet end of the filter element, and adsorbing the magnetic nanoparticles by the filter element, so that heavy metal ions are adsorbed and the water flows out of the pores.
After the heavy metals in the water are filtered and adsorbed, in order to remove the magnetic nanoparticles adsorbed on the filter element, a flushing fluid formed by clear water without the magnetic nanoparticles is introduced from the outer side of the filter element into the inner side through the holes, so that the magnetic nanoparticles adsorbed on the filter element are flushed, and then the flushing fluid flows out from the outlet end, which is called as a backwashing filter element. For further deep cleaning of the filter element, it is preferred to first remove the magnetic field and then backwash the filter element. More preferably, an acidic substance is added to the rinse solution to make the rinse solution acidic. When the washing is carried out, acidic substances are added into the opening structure, and heavy metal ions can be separated from the magnetic nanoparticles, so that the magnetic nanoparticles can be recycled.
Or, the outlet end of the filter element is firstly closed, the filter element is backwashed, and then the outlet end of the filter element is opened. Preferably, the outlet end of the filter element is closed, an acidic substance is added into the filter element, the filter element is back-flushed, heavy metal ions and magnetic nanoparticles can be separated under the action of the acidic substance, and finally the outlet end of the filter element is opened to recycle the magnetic nanoparticles.
Preferably, the magnetic nanoparticles are not limited, and include composite magnetic nanoparticles, magnetic nanoparticles coated with PAA or PEI, and the like.
Preferably, the magnetic field is detachable, so that the installation and removal are convenient.
Compared with the prior art, the invention has the following beneficial effects:
(1) when the water containing magnetic nanoparticles is injected into the hollow structure from the inlet end, the filter core can adsorb the magnetic nanoparticles under the action of a magnetic field, and the water is discharged from the pore structure, so that the aim of removing the heavy metals in the water is fulfilled; the specific surface area of the filter core with the hollow porous structure is large, so that the adsorption rate is greatly improved.
(2) The design hole diameter reduces from the filter core is inboard to the outside gradually, makes the water that contains magnetic nanoparticle flow in from great diameter, and minor diameter flows, and magnetic nanoparticle is adsorbed on the pore wall gradually, has effectively avoided magnetic nanoparticle to pile up at the pore structure entry, causes the pore structure to block up and unable filterable problem, has realized magnetic nanoparticle's high efficiency filtration.
(3) The inner diameter of the filter core in the direction from the water inlet end to the outlet end is designed to be gradually reduced, so that the filter core is favorably flushed by water containing magnetic nanoparticles, and the filtering effect is further improved.
(4) According to the invention, the filter core is prepared by preferably selecting the soft magnetic ferrite, so that the filter core is corrosion resistant, and the soft magnetic ferrite filter core plays a role in strengthening an external magnetic field, thereby reducing the requirement on the strength of the external magnetic field.
(5) According to the invention, the filter element can be placed in the container by adopting a method of injecting from the inlet end and flowing out from the hole when removing heavy metals in water, and purified water is contained between the container and the filter element after adsorption and filtration, so that collection and treatment are convenient; the filter core is washed by adopting a back washing method of entering the filter core from the hole, and the sewage after washing is discharged from the outlet end, so that the collection and treatment are convenient.
(6) The filter element has the advantages of simple structure, convenient manufacture, high filtering effect, economy, practicability and no secondary pollution, the concentration of heavy metal in water can be obviously reduced from 1.0mg/L to be lower than the drinking water standard recommended by WHO after the filter element is filtered once, and the filter element has good market prospect in industrial sewage treatment.
Drawings
Fig. 1 is a schematic structural view of a filter element in example 1 of the present invention.
Fig. 2 is a schematic view of the structure of the hole of fig. 1.
The reference numerals in fig. 1-2 are: the filter element comprises a filter element 1, an inlet end 2, an outlet end 3, a hole 4, an opening 5 at one end of the hole and an opening 6 at the other end of the hole.
Detailed Description
The present invention will be described in further detail with reference to the following examples and drawings, which are not intended to limit the invention to the details shown.
Example 1:
as shown in fig. 1, the filter element 1 for removing heavy metals in water is a hollow truncated cone structure with two open ends, one open end is called an inlet end 2, and the other open end is called an outlet end 3.
The inner diameter of the hollow structure gradually decreases from the inlet end 2 to the outlet end 3. In this embodiment, in the hollow circular truncated cone structure, the inner diameter of the inlet end 2 is 100mm, the outer diameter is 104mm, the inner diameter of the outlet end 3 is 60mm, the outer diameter is 64mm, and the height between the inlet end 2 and the outlet end 3 is 50 mm.
The filter element 1 is provided with a plurality of holes 4, each of which penetrates from the inside to the outside of the hollow structure, and the hole diameter of each of which is gradually reduced from the inside to the outside of the hollow structure. For example, in fig. 1, the opening 5 at one end of the hole 4 is located inside the hollow structure, the opening 6 at the other end is located inside the hollow structure, the hole 4 is in a circular truncated cone shape as a whole, the inner diameter of the opening 5 is 10mm, and the inner diameter of the opening 6 is 2 mm.
In this embodiment, the filter core is made of nickel-zinc ferrite soft magnetic material. The preparation method of the filter element comprises the following steps:
(1) uniformly dispersing nickel-zinc ferrite powder with the average particle size of about 2um into a premixed solution containing a binder PVA, a plasticizer PEG and a small amount of a dispersing agent ECO-2100 to prepare stable slurry;
(2) and (2) performing 3D printing by using the slurry obtained in the step (1) to obtain a filter element blank shown in figure 1, drying, and performing high-temperature sintering treatment at 1300 ℃ to obtain the high-density nickel-zinc ferrite filter element.
The method for removing heavy metals in the filtered water in the embodiment is utilized as follows:
and (3) applying a detachable magnetic field as low as 0.07T to the prepared filter element. Closing the outlet end 3 of the filter element. In the presence of Pb2+Adding PAA coated Fe into wastewater with the concentration of 1mg/L3O4Nanoparticles 25 mg. Injecting the wastewater into the hollow structure from the inlet end 2 of the filter element, allowing the water to flow out from the pores of the filter element, and allowing the magnetic nanoparticles to be adsorbedThe filter element absorbs the heavy metal ions, so that the heavy metal ions are absorbed by the filter element to obtain the water for removing the heavy metal ions.
After detection, Pb in the water flowing out of the filter element2+The concentration was 0.009 mg/L. The test standard is GB/T32992-.
After the filter core is used, in order to remove the magnetic nanoparticles adsorbed on the filter core, the filter core is back-flushed by a flushing liquid formed by clear water without the magnetic nanoparticles, namely, water flows into the inner side from the outer side of the filter core through a hole to flush the magnetic nanoparticles adsorbed on the filter core, and then flows out from the outlet end. In order to further deeply clean the filter element, the magnetic field is firstly removed, then the filter element is backwashed by clean water, preferably, an acidic substance is added into the flushing liquid to enable the flushing liquid to be acidic, and heavy metal ions and magnetic nanoparticles can be separated during flushing, so that the magnetic nanoparticles can be recycled.
Example 2:
in this example, the filter element for removing heavy metals from water had substantially the same structure as in example 1.
In this embodiment, the preparation method of the filter element is as follows:
(1) the nickel zinc ferrite powder with the average grain diameter of about 2um is evenly dispersed into premixed liquid of photosensitive resin PEGDA, solvent EG, photoinitiator TPO and the like to prepare stable slurry.
(2) And (2) performing 3D printing by using the slurry obtained in the step (1) to obtain a filter element blank shown in figure 1, drying, and performing high-temperature sintering treatment at 1300 ℃ to obtain the high-density nickel-zinc ferrite filter element.
The method for removing heavy metals in water by using the filter element in the embodiment comprises the following steps:
and (3) applying a detachable magnetic field as low as 0.07T to the prepared filter element. Closing the outlet end 3 of the filter element. In the presence of Pb2+Sep-Fe is added into waste water with the concentration of 1mg/L3O4-MnO2Composite nanoparticles 25 mg. Injecting the wastewater into the filter core from the inlet end 3 of the filter core, allowing the water flow to flow out from the pores of the filter core, adsorbing the magnetic nanoparticles by the filter core, and adsorbing the heavy metal ions by the filter core to obtain water without the heavy metal ions。
After detection, Pb in the water flowing out of the filter element2+The concentration was 0.007 mg/L. The test standard is GB/T32992-.
After use, the magnetic nanoparticles adsorbed on the filter element are removed. Firstly, the outlet end of the filter element is closed, the filter element is back-washed by using clear water without adding magnetic nano particles to form washing liquid, namely, water flow enters the inner side from the outer side of the filter element through a hole to wash the magnetic nano particles adsorbed on the filter element, and then the outlet end is opened, so that sewage flows out. Preferably, acidic substances are added into the filter element, the filter element is back-flushed, heavy metal ions and the magnetic nanoparticles can be separated under the action of the acidic substances, and finally the outlet end is opened to recycle the magnetic nanoparticles.
The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.