A New Approach in Reducing NOx in Diesel Exhaust by Discharge Plasma Catalytic Activity in Composite Industry Wastes

Hazardous gases such as oxides of nitrogen (NOx) come from fossil fuel combustion and, therefore, require special attention because there is a regular usage of fuel on a day-to-day basis. In the current work, a new methodology is proposed for diesel exhaust treatment involving electrical discharge plasma causing possible catalysis in a combination of two industrial wastes (composite waste) for removal of NOx. A dual-metal film and helical wire reactor were used to generate surface discharge plasma at room temperature and pressure. Five composite wastes (CW), namely, waste tiles + foundry sand, copper slag + red mud, iron tailings + waste tiles, red mud + waste tiles, and foundry sand + red mud, were used to examine their catalytic properties. A 5-kW diesel engine exhaust was sampled for laboratory experiments. The NOx removal efficiency, which was 16% under plasma-alone treatment at a specific energy of 140 J/L, got enhanced to 80%–93% in plasma-catalysis mode when CWs containing metal oxides were introduced into the plasma reactor. Further, it was verified that plasma catalysis with individual wastes yielded less NOx removal efficiency compared to that with CWs (40%–71% against 80%–93%), indicating the synergy of two wastes that are blended in the CWs.