The material also contains negatively charged ions, which can be moved with electric pulses to different parts of the surface.

FORBES: Connect

As the water passes through the media, the negatively charged arsenic ions are absorbed onto the surfaces of the positively charged media particles.

FORBES: "Plastic Bottle" Filters Can Help Millions Poisoned by Arsenic-Contaminated Water

In an ultracapacitor, positively charged ions gather on the surface of the negatively charged electrode and negative ions on the surface of the positive electrode.

ECONOMIST: Electricity storage