Ultrafiltration

Ultrafiltration can be explained as an effective separation method performed in various industries and laboratories for bioseparation processes. It is a common type of filtration used to isolate small particulate matter from samples. Ultrafiltration is a process that involves the usage of a semi-permeable membrane to facilitate separation. It separates the biomolecules based on pressure and concentration gradients and can be easily operated at a pressure of 2 to 10bar. Ultrafiltration is a highly efficient technique specifically used in the field of research for the isolation of microorganisms from samples. In this blog, we will discuss in detail the Ultrafiltration explanation, the principle of Ultrafiltration, Ultrafiltration membrane, function, types, Ultrafiltration system, and applications. 

Principle:

Ultrafiltration is performed similarly to reverse osmosis. The main principle of this is the pressure difference created between the solute and solvent along the semi-permeable membrane and the connection between flux and pressure on the solution. The solvent to be filtered is pressured through the ultrafiltration membrane as it also helps to change the taste, odor, and color of the solvent.

Ultrafiltration system:

The ultrafiltration system consists of a feed tank that is connected to a feed pump that directs the feed through the membrane modules. The feed is passed through the membrane and the filtrate collected out is the permeate and one which stands back is the retentate. The retentate is transported back to the feed pump, a separate retentate valve is present that helps further removal of fluids from the Ultrafiltration system. The collection of the desired product depends on the nature of the product. Sometimes, it may be the permeate passed through the membrane or the retentate that stays back. 

• Ultrafiltration system operating steps:

The operation system involves three major steps. They are:

1. Preprocessing involves installation, flushing, integrity testing, and equilibration. 

2. Processing involves concentration and diafiltration.

3. Post-processing involves product recovery, cleaning, sanitization, and storage. 

• Modes of operation:

This filtration operates in two modes. They are:

1. Normal mode filtration 

It is the common type of filtration where the solvent passes through the membrane where fluid velocity is perpendicular to the plane.

2. Tangential mode filtration 

This involves the inclusion of another fluid velocity component parallel to the plane of the membrane. 

• Types of operating systems:

It is classified into two types based on its application. They are:

1. Point-of-use: applicable for drinking water.

2. Point-of-entry: Not for drinking purposes. 

Ultrafiltration membrane:

Ultrafiltration membranes are highly porous materials that allow the passage of solvents through them. The key physical characteristics that a membrane should possess are:

• Membrane fabrication

• Retention capacity

• Permeability 

• Reusability

• Stability

• Compatibility

• Mechanical strength

The important physical characteristics that a membrane should possess are:

• Anisotropy

• Hydrophobicity

• Sensitivity

• Resistant

• Inert

• Insoluble

This membrane can hold particles of about 5–150 nm and can withstand a molecular weight of 1–1000 kDa that includes bacteria, viruses, proteins, nucleic acids, and nanoparticles. 

Ultrafiltration membranes are commonly made up of polymer films like

• Polyethersulfone

• Polysulfone

• Regenerated cellulose

• Fluoropolymers

• Polyvinylidene fluoride

• Polyacrylonitrile

• Polyamide

Membrane Modules:

Ultrafiltration membranes are categorized into different types of modules based on their shape and size.

• Spiral Module: These are made up of slim sheet-like membrane disks. These sheets are placed beneath the reservoir. O-ring is present that clinches the permeate valve and retentate valve. It provides a tangential flow through the surface. Transfer of mass is uniform in the case of spiral modules. 

• Hollow fibers and tubes: These are tubular structures made up of bundles of fibers. It operates based on tangential flow filtration. The thin fiber bundles are fitted inside the module to facilitate efficient flow. It allows both outside and inside flow of the fiber. 

• Spirals: It is a rolled-type module. The membranes are arranged with uniform spatial differences to form a sandwich. Sealing of permeate membrane forms a leaf and multiple leaves are added to increase efficiency. 

• Cassettes: It is a flat rectangular type of module. The membrane is arranged with uniform spaces where membranes are arranged as sandwiches. The spaces between permeate and membranes act as feed, retentate, and permeate flow channels. 

Applications:

Ultrafiltration is used in various industries for multiple purposes. They are:

• Food industry: Product testing, extraction, toxicity testing, adsorption, clarification.

• Pharmaceutical industry: Vaccine Isolation, IGg extraction, Blood plasma processing, endotoxins removal, product purification, drug testing, enzyme recovery, Final formulation, concentrating drugs.

• Dairy industry: Milk Purification, Cheesemaking, Whey extraction, Protein concentration, Pumping, Sterility maintenance.

• Paint industry: Separation, Paint holding, Check viscosity, Paint recycling.

• Plant extract industry: Coffee, tea, caffeine, and phytochemical extraction. 

• Beverage industry: Juice clarification, Product formulation, Wine or vinegar extraction, Beer recovery.

• Medical industry: Laboratory isolation, protein isolation, screening.

• Water treatment industry: Impurity removal, Microbial treatment, oil removal, 

• Chemical industry: Solvent recycling, catalyst extraction, 

Conclusion:

On the whole, Ultrafiltration is one of the efficient techniques of separation which is majorly applicable to multiple sectors. The benefits like economic cost, low operating pressure, and high efficiency has made it approachable for a wide range of works.