Oxygen, carbon dioxide, and other gases dissolved in water or other liquids can adversely affect many processes. Whether you are in the industrial, pharmaceutical, or semiconductor industry, delivering water that has very low levels of dissolved gases leads to longer equipment life, reduced maintenance, and improved quality.

Silicone membranes can effectively degas liquids, including low surface tension liquids and solvents. PermSelect® silicone membranes can be used for:

• O2 removal from water
• CO2 removal from water
• degassing all compatible liquids
• degassing low surface tension liquids
• degassing transformer oil
• degassing ultrapure water
• degassing ink

O2 and CO2 Removal from Water

Water naturally contains dissolved gases, even after purification steps such as reverse osmosis and filtration. When water used for analytical or high purity processes contains dissolved oxygen of carbon dioxide, a number of problems can occur. Scientists and process specialists remove dissolved gases from water in a number of ways, including a hydrophobic hollow fiber membrane system. The benefits can be remarkable: reproducible results that meet experimental or regulatory requirements; lower downstream process intensity and longer component life; improved yields of materials in contact with degassed water; reduced issues with corrosion, undesired pH levels and unwanted byproducts.

Oxygen: Membrane degassing of water to remove oxygen avoids exposing oxygen-sensitive compounds to its effects, and reduces oxidation problems. Oxygen in the presence of other dissolved compounds, such as ammonia, can lead to other types of corrosion that affect piping and components. Dissolved oxygen and other gases can form bubbles, which may negatively affect processes and analytical measurements.

CO2: In certain applications, such as ultrapure process water, removing CO2 is desirable to improve efficiency of other purification steps. A hollow fiber membrane contactor can efficiently remove the CO2 and extend the life of components. Carbon dioxide in steam can form carbonic acid and carbonate in water, causing accelerated corrosion and affecting readings for pH and conductivity. Removing CO2 can positively affect the process results in applications from ultrapure water in semiconductor manufacturing to productivity in aquaculture.

Degassing Ink

Dissolved gas and microbubbles in ink can significantly affect the speed and quality of printing. By interrupting droplet formation or pressurization at the ink head, dissolved gases can lead to improper jetting at the time of ink ejection. Beyond poor image quality, nozzle dropouts can cause expensive shutdown of the equipment, and the need for more frequent cleaning.

Degassing ink with a membrane prior to it reaching the print head is a simple process. The ink flows on one side of the membrane, while a vacuum is drawn on the other side. Gases dissolved in the ink readily transfer through the membrane to the vacuum side, leaving the ink degassed when it reached the outlet.

For providers of ink in closed loop systems, a membrane degasser is used to degas the ink while filling the vacuum-sealed bags. Because the closed system does not allow air to contact the surface of the ink, as some bulk systems do, the need for additional degassing is minimized. This is especially important for white inks, which must be handled carefully to maintain suspension of the TiO2 pigment. In addition, degassing ink while packaging can reduce foaming, which otherwise will slow the fill process.

How to Degass Liquids using PermSelect® Modules

Degassing liquids using PermSelect® membrane modules is straightforward as illustrated in the figure below. Liquid with dissolved gases is contained in a reservoir, or a continuous feed is supplied upstream from the membrane module. A pump may be placed in the circuit (upstream or downstream from the membrane module) if needed to provide a required flow rate through the system. The simplest method to degas a liquid is to use straight vacuum to remove all dissolved gases from the liquid. As shown in the figure below, liquid enters the center port of the PermSelect® membrane module, then flows on the outside of the hollow fibers (shell side) and exits the at side ports (shown on top of the module). Vacuum is applied at the ports on the end caps which provide vacuum to the inside (lumen side) of the hollow fibers. As liquid flows through the hollow fiber bundle, dissolved gases permeate the hollow fiber walls driven by the vacuum in the lumens. Extracted gases flow toward the vacuum pump and degassed liquid exits side ports.

Liquid degassing can be accomplished continuously with a single pass through the membrane module or with multiple passes by recirculating the fluid through a reservoir. The choice will depend on the system design, the capacity of the module to remove gases, and the required level of degassing. Other considerations include liquid-membrane compatibility, and the system fluid pressures. Please view the silicone chemical compatibility chart as an initial substance compatibility guide. Depending on your system pressure requirements, a reversal of liquid flow and vacuum (a lumen side liquid flow) may be required. The maximum recommended trans-membrane pressure (TMP) for shell side liquid flow is 15 psi. So if your system exceeds this TMP then a lumen side liquid flow is recommended up to 45 psi TMP. Contact an applications engineer, or call +1 (734) 769-1066 to discuss your particular liquid deassing needs.

MedArray provides its PermSelect® modules for liquid degassing directly to researchers, and to industry through Original Equipment Manufacturers (OEM’s) who are interested in integrating degassing solutions in their equipment.