Waste lubricating oils used in automobile engines and others include metallic compounds as impurities, like calcium and zinc originated in additive agents, and iron and lead due to engine wear. These impurities do not only prevent the waste lubricating oil from being recycled, but also cause hazardous emissions even in their incineration process. One of promising processes to remove these metallic impurities from waste lubricating oil at low cost is presented here. In this process, the waste lubricating oil is heated to about 300 degC, mixed with brown coal as an adsorbent of impurities. Brown coal was experimentally found to have higher performance to capture metallic impurities in waste lubricating oil than activated carbon. Moisture emission from particle adsorbents during heating process, which was unique to brown coal compared with activated carbon, was expected to have a positive effect on the removal performance of impurities.
