Membrane sparging, also known as using nanoporous membranes, is a precision method for generating exceptionally small and stable nanobubbles. Unlike other methods that rely on bulk fluid dynamics or electrical fields, this process uses a physical barrier to control the bubble size with a high degree of uniformity. This method is particularly valued for applications requiring a narrow size distribution of nanobubbles.

How It Works – Step-by-Step

1. Gas Supply
   • Pure or blended gases (air, O₂, CO₂, H₂, or ozone) are fed into a pressurized chamber beneath a hydrophobic or hydrophilic nanoporous membrane.
2. Nanoporous Membrane
   • The membrane (pore size: 20–200 nm) allows controlled gas diffusion into the adjacent water phase.
   • Materials may include PTFE, ceramic, stainless steel, or polymer composites.
   • Pore geometry and surface energy are critical to maintaining stable nanobubble formation.
3. Bubble Formation at Pore Mouths
   • When gas pressure exceeds the liquid-side hydrostatic pressure + capillary entry pressure, gas exits the pores in a dispersed fashion.
   • The bubble diameter depends on pore size, surface tension, and gas pressure. With appropriate design, nanobubbles (<200 nm) are consistently formed.
4. Nanobubble Release and Stabilization
   • As bubbles detach from the pore and enter the bulk liquid, shear forces, Brownian motion, and interfacial energy stabilize the nanobubbles.
   • Nanobubbles remain suspended due to their near-neutral buoyancy, high zeta potential, and internal Laplace pressure.

      

Key Features

Industrial Applications

Conclusion

The synergy between electrolysis and pressurized gas–liquid mixing offers a scalable, chemical-free, and energy-efficient way to generate stable nanobubbles. This method is especially valuable for plant and operations managers seeking to improve treatment performance, reduce chemical dosing, and support sustainable industrial processes.