Ultrafine continuous fibrous ceramic filter and method of manufacturing same

Abstract

An ultrafine continuous fibrous ceramic filter, which comprises a filtering layer of a fibrous porous body, wherein the fibrous porous body comprises continuous ultrafine fibers of metal oxide which are randomly arranged and layered, and powdery nano-alumina incorporated into the ultrafine fibers or coated thereon, the ultrafine fibers being obtained by electrospinning a spinning solution comprising a metal oxide precursor sol-gel solution, and optionally, a polymer resin, and sintering the electrospun fibers, in which the ultrafine fibers have an average diameter of 10˜500 nm, and the fibrous porous body has a pore size of maximum frequency ranging from 0.05 to 2 μm, exhibits high filtration efficiency at a high flow rate, and can be regenerated.

Description

TECHNICAL FIELD[0001]The present invention relates to an ultrafine continuous fibrous ceramic filter, which exhibits high filtration efficiency at a high flow rate, and can be regenerated, and to a method of manufacturing same.BACKGROUND ART[0002]There has been a recent upsurge in demand for highly advanced techniques for water purification capable of removing not only physical contaminants such as organic materials, heavy metals, etc. but also biological impurities such as viruses. Such a water purification system typically includes a membrane filter having pores smaller than particles that are to be filtered out. Examples of the membrane filter include a microfiltration filter (MF; pore size 50˜2000 nm), an ultrafiltration filter (UF; pore size 1˜200 nm), and a reverse osmosis filter (RO; pore size 0.1˜2 nm). The membrane-based liquid filter / separation techniques are regarded as very important in water treatment fields including oil / water emulsion separation and desalting, since t...

AI Technical Summary

Benefits of technology

The present invention provides a ceramic filter that has a high permeation flow rate and low pressure drop during filtration while being able to remove ultrafine particles such as viruses. Additionally, the ceramic filter can be regenerated, making it a long-lasting solution. The invention also provides a method for manufacturing the ceramic filter by electrospinning a metal oxide precursor sol-gel solution or a mixture of the metal oxide precursor sol-gel solution and a polymer resin to make a layer of continuous ultrafine fibers randomly arranged, and then sintering the ultrafine fibers at a temperature ranging from 250 to 1000° C. The ultrafine fibers can be impregnated or coated with a suspension of one-dimensional powdery nano-alumina.

Problems solved by technology

This results in a drastic pressure drop and reduces process flow rates.

In addition, during use, membranes are susceptible to clogging which further degrades the flow rates, and back washing must be used.

Back washing markedly increases operating costs and undesirably causes membrane damage or pore size increase.

This filter is capable of filtering 85˜95% by weight of fine particles but cannot filter ultrafine particles such as viruses.

Melt-blown non-woven fabrics usually have a fiber diameter of 1 μm or more and thus a filter made thereof cannot filter nanoparticles such as viruses.

Even when ultrafine fibers having a diameter distribution of 5˜500 nm are used, fibers having a larger diameter are present so that large pores are formed, undesirably decreasing the level of filtering precision and making it difficult to remove water-borne viruses having a size of 10˜100 nm.

However, it is very difficult to increase the level of filtering precision enough to remove nanoparticles such as viruses, while maintaining low operating pressures and high flow rates.

The reason for this is that there is a limit in decreasing the pore size sufficiently to filter ultrafine particles such as viruses, by minimizing the fiber fineness, and also that a small pore size drastically increases the operating pressure while undesirably sharply decreasing the flow rate.

However, these polymeric nanofiber filters suffer from a short lifespan, low thermal stability, swelling properties in various solvents, and difficulties in surface modification.

However, in the sol-gel process, it is often difficult to control the pore size because of the particles having an irregular shape, and undesirable cracks or pinholes may be formed in the uppermost layer during drying and sintering processes.

Also, when pore size is decreased to increase selectivity, a serious loss in the permeation flow rate and agglomeration of fine particles in the uppermost layer may occur, and thus it is difficult to maintain high selectivity and high permeation flow rate.

Hence, it is very difficult to actually obtain a porous ceramic filter having both superior selectivity and a sufficiently high permeation flow rate.

Briefly, increase in the mechanical strength of the filter results in a loss in the permeation flow rate.

In this case, however, there is a limit to the length of the metal oxide nanofibers which can form a homogeneous suspension, and a non-uniform suspension makes it difficult to manufacture a homogeneous filter.

Furthermore, although the filtration efficiency of ultrafine particles such as viruses is very high because of a pore size of 1˜100 nm, the permeation flow rate undesirably decreases.

As described above, conventional filters known to date are still unsatisfactory in terms of filtration efficiency, permeation flow rate, heat resistance, preparation and so on, the properties being required of an excellent water treatment filter material.

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