A device that reduces the concentration of pollutants by charge-based mechanisms is known as?

The device that reduces the concentration of pollutants by charge-based mechanisms is the electrostatic precipitator. This technology works on the principle of electrostatic attraction, where particles in a gas stream are charged through ionization. Once charged, these particles are attracted to and collected on oppositely charged surfaces, effectively removing them from the gas stream.

Electrostatic precipitators are particularly effective in industrial applications for controlling emissions from smokestacks and reducing particulate matter in the air. They can remove a high percentage of pollutants while using relatively low energy compared to other filtration methods, making them an efficient choice for air quality management in various industries.

This is distinct from other options like filters, which physically trap particles, separators, which typically involve different physical methods for distinguishing substances, and collectors, which can refer more generally to any device that gathers materials without specifying the charge-based mechanism. The charge-based principle uniquely characterizes the electrostatic precipitator as the correct answer in this context.