Lanthanides Usage Areas
Red mud is waste generated during alumina production. In alumina plants, 1.0-1.6 tons of red mud is produced during 1 ton of alumina production. It is estimated that over 66 million tons of these toxic wastes are produced in the world. It contains numerous minor – trace and rare metals such as La, Ce, Nd etc. in different ratio.
Rechargeable, high-powered nickel-metal hydride (NiMH) batteries are widely used as power sources for electrical and electronic devices such as digital cameras, cell phones and electric equipment. Spent nickel-metal hydride batteries contain 36–42% nickel, 3–4% cobalt and above 8% cerium, praseodymium, and neodymium.
Fluid Catalytic Cracking Catalyst
Fluid catalytic cracking catalyst plays a significant role in the petroleum and chemical industry. About 65% of the spent FCC is reused as catalyst, raw material for cement and ceramics. The remaining parts are used in the treatment of industrial wastewater and as an asphalt retarder.
The FCC catalyst contains kaolin, an active alumina matrix mixture, a silica or silica-alumina and rare earth exchanged Y-zeolite. REEs such as lanthanum and cerium are synthesized by ion exchange of Y-zeolites. Therefore, the spent FCC catalyst becomes a potential secondary source of cerium. The cerium content in the FCC catalyst is about 0.2-0.3%.
Cerium oxides and other cerium compounds are used in catalytic converters and larger-scale equipment to reduce sulfur oxide emissions. Cerium is a diesel fuel additive for micro-filtration of pollutants and promotes more complete fuel combustion for more energy efficiency. It is one of the components of misch metal, which is used extensively in the manufacturing of pyrophoric alloys, making aluminum alloys and in some irons and steels.
Cerium Dioxide In Glass Polishing Waste And Glass Films
Cerium dioxide production is currently about 54,400 tons, accounting for about 32% of REE oxides. The REE oxide consumption of the glass industry is approximately 40,000 tons, of which 16,000 tons are used for polishing applications. The main ingredient in glass polishing powders is about 40-99% cerium dioxide.
Cerium Oxide In Catalytic Converters
To improve the characteristics of the catalyst, some REEs like cerium oxide is doped which is useful for the treatment of the exhaust gases and is used in concentrations of up to 5%.
Under high-oxygen conditions, the cerium oxide absorbs oxygen, which helps to increase the efficiency by which nitrogen oxide is reduced to nitrogen. Under low-oxygen conditions, the cerium oxide releases stored oxygen and increases the efficiency by which carbon monoxide is oxidized and becomes carbon dioxide. Cerium allows the catalysts to operate at maximum efficiency as the air and fuel mixture in the engine is continuously cycled from slightly rich in oxygen to slightly poor in oxygen.