Latest Adsorbent for the Adsorption, Removal or Recovery of Environmental Pollutants

Dear Colleagues,

The topic of ion exchange and adsorption has passed through an interesting historical and scientific development, since the first synthetic ion exchanger, prepared probably in 1903 by the two German chemists Harms and Rupler, advanced into current technological maturity. Nevertheless, only scarce references had been found until 1850, when Thompson and Way, two English chemists, discovered “basic principles of cation exchange” through observations of soils. Materials responsible for those phenomena were chiefly described later on by Lemberg and Wiegner as clays, glauconites, zeolites, and humic acids. Also at the beginning of 20th century, specifically in 1935, two English chemists, Adams and Holmes, discovered the ion exchange properties in crushed phonograph records, which perhaps especially in Europe enabled scientists in the following decades to synthesize organic ion exchangers, called resins. For the first time in history, both inventors have been recognized for their scientific contribution. Although the process of ion exchange may be considered to have been discovered in 1850, it was not applied as an industrial separation process until 1905, when the German inventor Richard Gans demonstrated it as a unique process for water softening and for the removal of iron and manganese from waste streams. Approximately 50 years passed, especially after the Second World War (WWII), before an extensive development of the new organic ion exchangers, e.g., sulfonated and aminated copolymers of styrene and divinyl benzene with superior stability and easier recovery or regeneration, fabricated usually in oil refineries or petrochemical companies, enabled rapidly expanding all the ion exchange processes for plenty of industrial applications. Nevertheless, the higher thermal and radiation resistance of some natural zeolites in regard to synthetic ion exchange resins and their excellent selectivity to large, weakly hydrated cations and noxious radioisotopes allowed combining a development of entirely new technological applications of natural zeolites in the following decades. This phenomenon die not generally displace competitive synthetic ion exchangers in then-existing environmental applications, but quite the opposite: it initiated a development of entirely new processes for which synthetic resins were not suited.

Adsorption science has a very long history, with the first practical adoption of adsorption noted in ancient times. The current adsorption theory and relevant applications initiated by Langmuir's fundamental work have been developed extensively more or less during the last 80 years. Today, they comprise many advanced approaches, including a wide spectrum of modern surface chemistry sciences. The autonomous existence of adsorption is based on the enormous complexity that is inherent in adsorption phenomena at various interfaces and the widespread, general occurrence and importance of adsorption and related domains in nature, including everyday-life products and environmental applications.

Prof. Dr. Eva Chmielewska
Guest Editor

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• separation processes
• adsorption
• ion exchange
• environmental pollutant removal
• regeneration
• synthetic and natural adsorbents