Conductive polymers are purified using a solid scavenger. The solid scavengers include metal-scavenging functional groups linked to the surface of a particle support material. To improve the functionalization of the support material, the support materials are first treated with sulfuric acid or nitric acid before attaching the molecules containing the metal-scavenging functional groups. The solid scavengers used in the purification methods are more efficient at removing impurities in conductive polymers than existing scavengers.