Nanoparticle filtration

A building ventilation system configured to process a gas including nanoparticles suspended therein, the building ventilation system having a gas intake and a gas output, and a flow direction extending from the gas intake to the gas output, the building ventilation system comprising:

• a filter apparatus configured to process air including nanoparticles suspended therein, the filter apparatus comprising an air intake and an air output, and a flow direction extending from the air intake to the air output, the filter apparatus comprising:
• a piezoelectric ultrasonic plume generator that is positioned downstream of the air intake in the flow direction, wherein the plume generator is adapted to receive the gas via the gas intake and configured to produce a plume of liquid droplets suspended in the received air;
• a mixing chamber that is positioned downstream of the plume generator in the flow direction, wherein the mixing chamber is configured to receive and mix the plume of liquid droplets suspended in the received air and the nanoparticles suspended therein to generate a mixture, wherein the mixture comprises gas and nanoparticles that are adhesively bonded to the suspended liquid droplets;
• a cyclonic separator that is positioned downstream of the mixing chamber, the cyclonic separator comprising a substantially conical cavity narrowing in diameter in the flow direction, and configured to produce cyclonic spinning of the air to separate the suspended liquid droplets from the air and to emit the separated air to the air output;
• a propeller configured to propel the air through the filter apparatus in the flow direction;
• wherein the filter apparatus is further configured to re-use, in the plume generator, liquid collected from the cyclonic separator;
• and
• a second stage filter configured to remove nanoparticles from liquid collected from the cyclonic separator, wherein the second stage filter is configured to allow a selected amount of nanoparticles to remain in the collected liquid to be re-used in the plume generator, to promote adhesion between liquid droplets and nanoparticles in the mixing chamber.

A method for separating nanoparticles from a gas, comprising:

• receiving the gas via a gas intake;
• producing a plume of liquid droplets suspended in the received gas with a piezoelectric ultrasonic plume generator;
• mixing the plume of liquid droplets suspended in the received gas and nanoparticles suspended therein to generate a mixture, wherein the mixture comprises gas and nanoparticles that are adhesively bonded to the suspended liquid droplets;
• cyclonically separating the gas from the suspended liquid droplets;
• re-using, in the plume generator, liquid from the cyclonic separator;
• and
• removing nanoparticles from liquid collected from the cyclonic separator, while allowing a selected amount of nanoparticles to remain in the collected liquid to be re-used in the plume generator, to promote adhesion between liquid droplets and nanoparticles in the mixing chamber.