Chapter 23 - Solubility Issues in Environmental Pollution

Abstract

This chapter describes the use of seawater for absorbing the sulfur dioxide produced by the combustion of fossil fuels. The chapter also reviews the antiknock petrol additives that have replaced methyl tert-butyl ether (MTBE). The desulfurization of oil refinery streams by ionic liquids is also discussed. In the case of sea, which is slightly alkaline, the equilibria controlling the distribution of the various forms of CO2 and SO2 between air and water lead to the sea acting as a sink for these pollutants, which tends to limit both the greenhouse effect and the effects of acid rain on land. The carbonates and sulfates into which CO2 and SO2 are converted are natural components of seawater, and seawater remains practically unaffected by these inputs. In practice, MTBE has been mainly replaced by tert-amyl methyl ether (TAME) or ethyl tert-butyl ether (ETBE). The chief advantages of ETBE over TAME are its lower solubility in water, its higher octane rating, and the possibility of its production from bioethanol. Room-temperature ionic liquids (RTILs) are used to desulfurize oil refinery streams. RTILs are salts with melting points below 100ºC that are composed of a large organic cation and an inorganic anion. They dissolve most organic and inorganic compounds, whether polar or non-polar, and are thermally stable and non-inflammable, and their negligible vapor pressure means reduced losses from evaporation and reduced risk for those who use them.