Mechanochemical activation of titanium slag for effective selective catalytic reduction of nitric oxide

Ti-bearing blast furnace slag was usually recycled by acid leaching. For the first time, a catalyst was synthesized from the slag by wet ball-milling. During this process, no waste was produced. When the activated slag was used in selective catalytic reduction of nitric oxide (NO), 80.5 ± 1.2% of NO (990 ppm) was removed at 350 °C. The catalyst steadily removed 91.0 ± 1.3% of NO for 900 min at 400 °C. On the contrary, the slag without activation showed almost no catalytic activity at these temperatures. The enhanced activity was mainly attributed to the following characterizations. After wet ball-milling, specific surface area of the slag was increased from 2.595 to 26.497 m²/g; surface acid sites were amplified by 15 times; Fe/Ti ratio on surface was enhanced from 0.20 to 1.10. At the same time, surface Fe²⁺/Fe³⁺ was regulated from 0.43 to 0.53. The above enhanced properties were attributed to the mechanochemical activation, which dissolved and re-deposited active species on particle surface as well as reinforced the effect between Fe and Ti species. The main result of this work put forward a green method for the direct utilization of industrial waste without generating by-products.