KDF® Process Media are high-purity, granulated copper and zinc-based alloys that treat water through a process based upon the principle of redox (Oxidation-Reduction). Originally, KDF was shorthand for Kinetic Degradation Fluxion. Basically, KDF creates zinc oxide in the cartridge which helps stop bacteria from growing--it actually killls bacteria--and allows the carbon to last longer.
GAC will remove organic materials VOCs and radon gas by a process called adsorption. KDF removes metals including lead and hexavalent chromium 6, pesticides, Trihalomethanes THMs, MTBE, and neutralizes chlorine. KDF combined with coconut shell carbon (GAC or carbon block) extends the life by protecting against bacteria growth. Most systems use carbon to remove chlorine, but need replacing every 3 to 6 months--bacteria will grow in carbon. But, the copper zinc in KDF produces zinc oxide which inhibits bacteria growth extends the life to 18 months.
Carbon filters are most effective at removing chlorine,sediment and volatile organic compounds (VOCs) from water.