Hydrophilic surface bubble detachment

The bulk concentration of anolyte, CA,Na. is almost unchanged under normal operations. However, 5a is a function of the flow rate and of the surface roughness of the membrane. Chlorine bubbles, generated at the anode, agitate the anolyte solution near the membrane. As bubble action becomes more intense, the diffusional boundary layers become thinner. The membrane surface itself is not flat. Industrial membranes are normally reinforced with PTFE fiber or cloth. A metal oxide coating on zero-g membranes improves their hydrophilicity and allows easier detachment of chlorine bubbles. These coatings also affect the thickness of the diffusion layer and the limiting current density. 

There are numerous ways in which surface tension can be measured. The technique that is perhaps the most suitable for electrolyte solutions is the Maximum Bubble Pressure technique, as the continuous generation of fresh interface assists in acquiring data and is not influenced by low levels of contamination. Typically a bubble is produced from a fine capillary every five to ten seconds and as it grows the pressure is monitored. When the pressure reaches a maximum, the radius of the bubble is equivalent to the inside radius of the hydrophilic capillary tip. At this time the radius of the bubble and the internal pressure are known, therefore the surface tension can easily be calculated using the Laplace equation. This bubble then detaches and a new bubble is created, allowing for easy repeat measurements of surface tension at a freshly generated interface. 

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