Where Do Amine Emissions Come From?Mario Pipunić
As derivatives of ammonia, amines are a group of chemical compounds that have a variety of practical applications in today’s modern world. They’re used as an ingredient in certain pharmaceuticals, as well as epoxy resin curing agents and dyes. However, one of the most common and contemporary uses of amines is in gas treatment, where they are employed to extract carbon dioxide (CO2) from natural gas processing and refining plants.
This role in the carbon capture and storage (CCS) industry is instrumental in reducing the environmental impact of such industries – but it may engender problems of its owns. That’s because amine emissions are generated primarily from the CCS industry, as amine solvents can be emitted via the airborne flue gases or in the wastewater effluent streams.
Dyes and epoxy resins
Aromatic amines are often favoured as a starting material for a variety of different dyeing agents, since the reaction which occurs when they come into contact with nitrous acid creates diazonium salt. Once coupled, these form azo compounds which are renowned for their strong colourings, hence their use in dyes.
Meanwhile, a range of different amines are extremely effective as epoxy resin curing agents, including cyclohexylamine, dimethylethylamine and a number of diamines. Tetraethylenepentamine and triethylenetetramine are also used for the same purpose. Advanced analytical techniques have revealed that both dyes and epoxy resins can leach these amines into the air or water over an extended period of time.
Research from 2011 found that 42% of commercial drugs on the market contained functional groups from the amine family. These compounds are put to a wide variety of different uses, from antihistamines, anti-depressants and decongestants to tranquilizers and even serious pain relievers (such as morphine and codeine).
While a proportion of the active ingredients in these pharmaceuticals are absorbed by the body (and thus complete their primary function), a significant percentage can pass through the digestive system unscathed. Afterwards, they are excreted into the sewer system, where they are capable of surviving most conventional wastewater treatment processes, as well.
The aforementioned sources of amine emissions are believed to be so small as to virtually negligible. However, the use of CCS to remove CO2 from industrial flue streams is projected to play a potentially greater role. This source can be responsible for emission of amine solvents into the air (via acid gas reactions, evaporations, oxidation and thermal degradation, which is one reason why gas analysis is such a strong focus in the industry) or into wastewater effluents.
The existing body of research is insufficient to indicate whether these emissions pose a credible threat to human and environmental health over the long term. However, there is some concern over amine degradation products, such as nitrosamines, with further investigations into their concentrations in and ramifications for the natural world still ongoing.