What Is Ultrafiltration System and How Does It Work?

Ultrafiltration is a modern water purification method that has received widespread attention in recent years due to its efficient removal of various impurities in water; Whether you want to learn how ultrafiltration can improve water quality, or find treatment plans for industrial water, mastering ultrafiltration knowledge can help you make smarter choices.

What is ultrafiltration?

Ultrafiltration (UF) is a type of membrane separation process that is driven by a pressure difference and belongs to the pressure driven membrane separation process; The focus is on deceiving semi permeable membranes with specific pore sizes, which can separate, purify, and concentrate substances of different molecular weights in the solution under a pressure function of 0.1-0.5 MPa!

The ultrafiltration process is essentially a mesh separation process. Under the pressure difference, solvents and small molecule solutes in the data liquid pass through the membrane from the high-pressure side to the low-pressure side, resulting in filtrate or permeate! And the large molecular components are trapped by the membrane and added to the concentration in the concentrated solution; According to this discrimination mechanism, the selectivity of ultrafiltration membranes mainly depends on the size and shape of the membrane contour pores, rather than the chemical properties of the polymer!

Compared with other membrane separation capabilities, ultrafiltration is located between microfiltration (MF) and nanofiltration (NF), and there is no significant boundary between the three; The rated pore size range of microfiltration membranes is 0.02-10 μ m, while reverse osmosis (RO) membranes are 0.0001-0.001 μ m.

How is the ultrafiltration working process ?

The mechanism of ultrafiltration is mainly based on the principle of sieving, accompanied by adsorption on the membrane surface and pores; When a liquid mixture flows through the contour of an ultrafiltration membrane under pressure, the tiny pores densely packed in the membrane contour allow water molecules and small solute molecules to pass through, while substances with a volume larger than the membrane pore size are retained, thereby achieving purification, identification, and concentration of the solution.

The ultrafiltration process is not just a simple physical screening process; According to the surface of Sorragin, the separation efficiency of ultrafiltration membranes depends not only on the plate hysteresis screening function of membrane pore size, but also on the blocking barrier function of membrane pores and the adsorption function of membrane surface and pores on solutes!

In the ultrafiltration process, a key phenomenon is the generation of concentration polarization; This is due to the accumulation of detained impurities on the membrane contour, forming a concentration gradient.

The ultrafiltration membrane used in industry is usually an asymmetric structure, consisting of two layers: one is an ultra-thin activation layer (with a thickness of about 0.25 μ m), which plays a major role in separating solutions! The other layer is a porous maintenance layer (with a thickness of about 75-125 μ m), which has high permeability and mainly plays a supporting role; This asymmetric structure not only ensures the accuracy of membrane identification, but also improves the mechanical strength and water flux of the membrane;

Comparison between Ultrafiltration and Other Membrane Separation Technologies

What are the types of ultrafiltration membranes?

Ultrafiltration membranes can be classified according to various formats such as material, appearance, and structure! According to the different membrane materials, ultrafiltration membranes can be divided into two categories: inorganic membranes y organic membranes;

According to the external characteristics of the membrane, ultrafiltration membranes can be divided into the following main types:

• Flat film is the most basic form of film, suitable for small-scale handling and highly polluting liquids.
• The inner diameter of the tubular membrane is greater than 10nm, making it easy to clean and maintain, and suitable for handling high solid content fluids;
• The inner diameter of the capillary membrane is between 0.50-10.00nm and it has a high packing density!
• The inner diameter of the hollow fiber membrane is less than 0.5nm, making it the most advanced and sophisticated form of ultrafiltration technology. It has a very high specific surface area and is easy to operate!

According to the structural state of the membrane, ultrafiltration membranes can be divided into symmetric membranes and asymmetric membranes ;

• Symmetrical membranes are isotropic and have consistent pores in all directions, belonging to deep filtration! A
• Symmetric membranes have a dense surface layer (with a thickness of about 0.1 μ m or less) and a bottom layer dominated by finger like structures (with a thickness of 200-250 μ m), which belong to surface filtration.

Hollow fiber ultrafiltration membranes can be divided into two types based on the inlet method: internal pressure y external pressure ! Internal pressure refers to the process where raw water enters from within the membrane fibers and purified water is produced from outside the membrane fibers; External pressure refers to the process where raw water enters from outside the membrane and purified water is produced from inside the membrane.

Ultrafiltration membranes can also be classified into hydrophilic membranes y hydrophobic membranes based on the hydrophilicity or hydrophobicity of the membrane material; Hydrophilic membranes have strong anti fouling ability because water molecules are more likely to form hydration layers on the membrane surface, reducing pollutant adsorption! Hydrophobic membranes are more prone to contamination, but typically have higher mechanical strength;

What are the application ultrafiltration?

Ultrafiltration has been widely used in many fields due to its efficient separation characteristics. In the field of water treatment, ultrafiltration is mainly used for the preparation of high-purity water for the electronics industry, pretreatment of reverse osmosis components, production of mineral water, reuse of reclaimed water, and production of drinking water;

In the food and fermentation industry, ultrafiltration is applied for clarification and sterilization of wine, ripening of soy sauce, sterilization and decolorization of vinegar, purification and refinement of fermentation broth, purification of fruit juice, acceptance of sugar juice and sugar solution, acceptance of whey protein, and concentration of skim milk. The ultrafiltration process is carried out at room temperature and does not damage the thermosensitive identity, effectively maintaining the original flavor and nutritional value of the food.

The pharmaceutical industry is an important application area of ultrafiltration, which includes the purification and refinement of antibiotics and interferons, the removal of heat sources from injection water, the treatment of plasma and biopolymers, the separation, concentration, and purification of proteins and enzymes, as well as the refinement and purification of Chinese herbal medicines; The mild classification of ultrafiltration is particularly suitable for the treatment of bioactive substances and can effectively prevent the denaturation, inactivation, and autolysis of biomolecules;

In the field of industrial wastewater treatment, ultrafiltration is widely used in oily wastewater treatment, electrophoretic coating wastewater treatment, textile printing and dyeing wastewater treatment and reuse, papermaking wastewater treatment, and radioactive wastewater treatment, etc! In the reception of dyes in dyeing wastewater, polysulfone and polysulfone amide ultrafiltration membranes are used to treat printing and dyeing wastewater without the need for acid neutralization or cooling, which can effectively receive dyes.

Ultrafiltration technology is also combined with bioreactors to form membrane bioreactors (MBR), which are used for deep management of various wastewater! This combined process combines the benefits of biodegradation and efficient membrane separation, resulting in good and static effluent quality, small footprint, and low residual sludge production. It is a popular research and application trend in the field of wastewater treatment.

In terms of resource recycling, ultrafiltration can effectively absorb useful substances from industrial wastewater, such as paint from electrophoretic coating wastewater, protein from food industry wastewater, etc., realizing the resource utilization of wastewater, in line with the concept of circular economy and sustainable development!

What are the advantages of ultrafiltration?

Compared with traditional methods, ultrafiltration has several significant advantages; The ultrafiltration process is carried out at room temperature without causing component damage, making it particularly suitable for the identification, concentration, and enrichment of heat sensitive materials such as drugs, juices, etc!

The ultrafiltration process does not undergo phase change , does not require the addition of chemical reagents, has no secondary pollution, and is an energy-saving and environmentally friendly separation technology. Compared with traditional thermal concentration methods, the energy consumption of ultrafiltration is usually only one tenth to one third of the former, greatly reducing operating costs!

Ultrafiltration technology has high consistency, is very useful for the recovery of trace amounts of identity in dilute solutions, and for the concentration of low concentration solutions; In the preparation of biological products, the use of ultrafiltration technology instead of traditional ammonium sulfate precipitation method, dialysis desalination and vacuum concentration process can achieve an average recovery rate of 97.18% for albumin, while significantly reducing raw material consumption and energy demand;

The ultrafiltration process only uses pressure as the separation power, with simple assembly, easy operation, and easy control and maintenance! Ultrafiltration has a high degree of automation and low labor intensity, making it suitable for continuous and automated production needs!

Ultrafiltration technology also has the benefit of a wide range of applications. Due to the diversity of membrane material types and the controllability of membrane pore size, ultrafiltration can be applied to many fields from drinking water treatment to industrial wastewater reuse, from food processing to biopharmaceuticals, etc., with strong adaptability and flexibility! Ultrafiltration also has its limitations! It cannot directly obtain dry powder formulations, and for protein solutions, it can generally only obtain concentrations of 10% -50%.

What factors can affect the processing efficiency of ultrafiltration systems?

The efficiency of ultrafiltration preparation is influenced by various manipulation parameters and conditions! Operating pressure is one of the key factors affecting ultrafiltration compliance.

The flow rate of the feed solution  has a significant effect on ultrafiltration compliance; Increasing the flow rate of the feed liquid can consolidate the turbulence level of the membrane surface liquid flow, reduce the concentration polarization phenomenon, and thus popularize the permeability flux;

The operating temperature  directly affects the viscosity of the material liquid, thereby inducing ultrafiltration compliance. As the temperature increases, the activity of water molecules increases, viscosity decreases, and water production increases accordingly.

The quality of incoming water, especially turbidity, has a significant impact on water production; The higher the turbidity of the incoming water, the lower the water production of the ultrafiltration membrane, and high turbidity incoming water is more likely to cause membrane fouling and congestion!

The confusion and cleaning of membranes are directly related to the long-term operation of ultrafiltration systems! Membrane fouling can cause a decrease in permeability flux and requires regular cleaning and restoration;

The pH value  can sense the profile characteristics of membrane materials and pollutants, thereby sensing the interaction between the membrane and solutes! Different membrane materials have different pH suitable ranges, such as cellulose acetate membrane suitable for pH 3-8 environments, while polysulfone membrane can operate statically in the pH 2-12 range.

How to prevent ultrafiltration membrane fouling?

Ultrafiltration membrane fouling is a key issue in the long-term static operation of sensing equipment, and effective prevention and control of confusion are crucial. Membrane confusion mainly includes two situations: membrane surface deposition (forming a filter cake layer) and membrane pore congestion.

Pre treatment is the primary measure to reduce ultrafiltration membrane fouling. Select appropriate pretreatment processes based on the nature of the material, such as multi-media filtration, activated carbon adsorption, chemical coagulation, etc., which can effectively remove potential pollutants from the department and reduce the pollution load of subsequent ultrafiltration membranes;

Optimizing the manipulation conditions can also effectively reduce membrane fouling. Control the appropriate manipulation pressure and recovery rate to avoid rapid formation of gel layer under excessive pressure. Maintain appropriate feed liquid flow rate and promote lateral migration of membrane surface pollutants. Regularly use physical cleaning techniques such as backwashing and air scrubbing to remove membrane contour deposits in a timely manner!

Chemical cleaning is a necessary pathway for the reduction of membrane instincts; When membrane fouling leads to a decrease in flux to a certain level, chemical cleaning is required!

Membrane material modification is a long-term strategy to improve anti pollution ability! By developing hydrophilic membrane materials, preparing composite membranes, and grafting modification on membrane surfaces, the anti pollution performance of membranes can be consolidated;

Optimizing the design and operation of membrane components can also help control pollution. Adopting interlaced flow filtration instead of dead end filtration can shrink the deposition of pollutants on the membrane contour; Design a reasonable flow channel structure to promote turbulence! For hollow fiber membranes, internal or external pressure can be used to adapt to different types of influent!

A comprehensive monitoring and control system in the building can promptly detect pollution problems and adopt response measures! By monitoring the changing trends of targets such as transmembrane pressure difference, water production flow rate, and water quality parameters, membrane confusion can be alerted, cleaning opportunities and plans can be optimized, and irreversible confusion can be avoided.

What aspects should be paid attention to in the daily operation and maintenance of ultrafiltration preparation?

The long-term static operation of ultrafiltration relies on standardized daily operation and maintenance! **Pre operational checks are the first step in ensuring the safe operation of the system.

Monitoring operational parameters is a key task in daily operations; It is necessary to regularly record key parameters such as inlet pressure, production pressure, and water quality, and detect abnormal situations in a timely manner through trend analysis!

Regular cleaning is the key to maintaining organizational performance. There are two main types of cleaning nets: physical cleaning and chemical cleaning!

The establishment of shutdown protection is particularly important for the establishment of intermittent operation! When there is a short-term shutdown (less than 10 days), sterilization and backwashing should be carried out, and precious liquid should be injected and sealed for storage;

Membrane integrity testing is a necessary measure to ensure the quality of effluent. Regularly verify the integrity of the membrane through pressure attenuation tests, bubble point tests, or turbidity tests, and promptly detect and replace broken membrane components.

Spare parts management and preventive maintenance can reduce unexpected downtime. Adequate spare parts should be stored, such as sealing rings, instruments, and other vulnerable parts! Develop preventive maintenance measures according to the manufacturer’s recommendations, regularly inspect the working status of auxiliary equipment such as pumps and edges! The complete operation and maintenance of the building archives provide data support for optimizing the compilation process.

Conclution

Ultrafiltration , as an efficient and environmentally friendly method, has demonstrated enormous value in many fields. With the continuous improvement of membrane material capabilities and further reduction of costs, ultrafiltration will play a more important role in the comprehensive utilization of water resources, material separation and concentration, and provide technical support for sustainable development!

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