A process for removing impurities from a liquid azole heteroaromatic compound-containing (e.g., triazole-containing) mixture by: (a) providing a liquid azole heteroaromatic compound-containing mixture having impurities; and (b) passing the azole heteroaromatic compound-containing mixture through at least one filtration membrane which is a nanofiltration membrane and/or ultrafiltration membrane having a molecular pore size in the range of from about 200 daltons to about 1 kilodaltons to provide a permeate that is an at least partially purified azole heteroaromatic compound-containing mixture and a retentate with at least some impurities.