a wastewater - recyclable polymerization process for producing a polyaniline - based resin includes : feeding into a reactor an aniline monomer , an acid solution and an oxidizing agent to undergo polymerization so as to produce polyaniline resin particles ; filtering the polyaniline resin particles from an acidic aqueous solution formed during the polymerization ; neutralizing and drying the polyaniline resin particles to form a powder ; recycling the acidic aqueous solution by mixing the acidic aqueous solution in the reactor with a fresh reactant feed which contains the aniline monomer , the acid solution and the oxidizing agent ; and permitting the reactant feed to undergo polymerization in the presence of the recycled acidic aqueous solution at room temperature without cooling the reactor .