Reverse Osmosis Membranes

• High-efficiency filtration
• Energy saving
• Environmental protection
• High reliability

Reverse osmosis membrane also called RO membrane is a semi-permeable membrane used for water treatment and filtration, which plays a vital role in modern water treatment technology. It provides a highly efficient water purification solution. Reverse osmosis systems can be modularly designed to meet water treatment needs of various scales and applications.

• High-efficiency filtration

RO membranes can effectively remove dissolved substances in water, including salts, bacteria, viruses, etc., to obtain clean and pure output water

• Energy saving

Compared with traditional water treatment methods, RO technology does not require high temperature and pressure, which can significantly save energy.

• Environmental protection

RO membrane processes do not require the use of chemicals, reducing pollution to the environment.

• High reliability

Can operate stably for a long time and have a longer service life.

Working Principle

The working principle of reverse osmosis membrane is to separate water molecules from water containing dissolved substances through a semi-permeable membrane to obtain pure water.

Osmosis: Water naturally flows from a low-concentration solution to a high-concentration solution. This process is called osmosis.
Reverse osmosis: During reverse osmosis, pressure is applied to reverse the direction of natural osmosis, causing water to flow from a high-concentration solution to a low-concentration solution.
Filtration: The pores of the reverse osmosis membrane are very small (usually less than 0.0001 microns). Only water molecules can pass through, while harmful substances, bacteria, viruses, salts and other large molecules dissolved in the water are trapped on the other side of the membrane.

How to choose reverse osmosis membrane

01.Molecular Weight Cut-off (MWCO)

This vital parameter represents the minimum molecular weight of solutes that the nanofiltration membrane can retain with a remarkable efficiency exceeding 90%, typically expressed in Daltons (Da). Nanofiltration membranes generally exhibit molecular weight cut-offs ranging from 100 to 1000 Da. This specific cut-off decisively influences the separation capability of substances. For example, a membrane with a 200 Da cut-off skillfully captures disaccharides and small peptides, while selectively permitting the passage of certain monosaccharides and inorganic salts.

02. Salt Rejection Rate

This parameter assesses the membrane’s adeptness in retaining salt substances, denoted as a percentage. Generally, the rejection rate for monovalent ions-such as sodium and chloride-ranges from 50% to 80%, whereas for divalent and multivalent ions-like calcium and magnesium-it surpasses 90%. Influential factors include the membrane’s material, structural composition, operating pressure, and raw water concentration. Notably, heightened operating pressure often boosts the salt rejection rate, showcasing the membrane’s adaptability.

03. Water Flux

Also known as the water permeability rate, this parameter quantifies the volume of water transmitted through each unit area of the membrane per hour, expressed in L/(m²·h). Water flux is closely tied to the membrane’s material, pore size, operating pressure, ambient temperature, and raw water properties. Typically, increased operating pressure and temperature augment water flux, whereas higher pollutant levels in the raw water reduce permeability, highlighting the membrane’s sensitivity to environmental conditions.

04. Membrane Pore Size

Strategically positioned between reverse osmosis and ultrafiltration membranes, the nanofiltration membrane’s pore size typically ranges from 0.5 to 2 nanometers. Although precise measurement may remain elusive, pore size is intricately linked to the molecular weight cut-off, where a smaller pore size efficiently retains larger molecular weight substances, enabling superior separation and selective permeability.

05.Applicable PH Range

This parameter delineates the pH spectrum within which the nanofiltration membrane reliably operates, generally from 2 to 11. Operating beyond this range may lead to hydrolysis or membrane swelling, impairing performance and reducing lifespan. Under extreme acidic or alkaline conditions, the membrane’s structural integrity may weaken, affecting both salt rejection rate and water flux, showcasing its sensitivity to pH variations.

06. Maximum Operating Temperature

This denotes the peak temperature at which the nanofiltration membrane retains its functional integrity, typically between 30 and 45°C. Excessive temperatures may compromise the thermal stability of the membrane materials, leading to deformation, aging, and subsequent performance deterioration, affecting water flux and retention characteristics, underscoring its temperature resilience.

Application of reverse osmosis membrane

• The salt in seawater is removed to obtain drinkable fresh water.

• Clean and safe drinking water is provided by removing harmful substances in water, such as bacteria, viruses, heavy metals and salts.

• Industries that require high-purity water, such as the electronics industry, pharmaceutical industry, and food industry, use reverse osmosis membranes for water treatment.

• Remove harmful substances from sewage and recycle water resources.

New technology enhances filtration efficiency

Filmedia® has developed a new generation of reverse osmosis membranes based on polymer interface nano self-assembly technology, breaking through the limitations of traditional reverse osmosis membrane research and development.

Ultra-thin separation layer
By using polymer interface nanotechnology, the thickness of the separation layer is reduced to at least one-third of the traditional polyamide film (previously limited to 100 nanometers). This breakthrough significantly increases water flux and achieves a significant increase in permeability.

Significantly improved performance
The introduction of nanoparticles and special hydrophilic polymers has made breakthrough progress in the hydrophilicity, anti-fouling ability, durability and antioxidant properties of the membrane.

Industrial reverse osmosis membranes

Industrial RO membranes are used in large-scale water treatment systems. Their filtration accuracy can reach 0.00001 microns. They can effectively remove bacteria, viruses, solvents, heavy metals, radioactive elements, etc. in the water, provide high-quality pure water, and can be used in various industrial production scenarios.

Specification

Domestic reverse osmosis membranes

The main features of domestic RO membranes are miniaturization, light weight, easy installation and maintenance. Their filtration accuracy is usually 0.0001 microns, which can remove most impurities and bacteria, but it is difficult to handle pathogenic viruses, chemical pollutants, etc.

Specification