Coal pollution mitigation emissions of sulfur dioxide or oxides of nitrogen associated with the utilization of coal in the generation of electricity." Before being adopted in this fashion, historically "clean coal" was used to refer to clean-burning coal with low levels of impurities, though this term faded after rates of domestic coal usage dropped. The term appeared in a speech to mine workers in 1918, in context indicating coal that was "free of dirt and impurities." In the early 20th century, prior to World War II, clean coal (also called "smokeless coal") generally referred to anthracite and high-grade bituminous coal, used for cooking
Calgon Carbon pond and aquarium cleaning, and removal of impurities during the manufacturing process of vitamins. The company also serves "industrial processes" applications such as liquid chemicals, catalyst support, gas and water processing, ultrapure water, and bio-based chemicals. Activated carbon, which is a small form of carbon with a large pore structure that can remove impurities, was one of the first products produced by the company in the 1940s. Initially manufacturing granular activated carbon (GAC), the company also began producing forms such as powdered, pellets, and later cloth. Pittsburgh Coke and Chemical introduced an early activated carbon system to decolorize sugar in