Environmental aspects of plasma technology

Here we can mention as an example the otherwise solvent-intensive fine-cleaning of metals, for which water plasmas are occasionally to be preferred. When cleaning in smaller plants (40 l volume), one mol (18 g water) is sufficient for several cleaning cycles. This is possible because during the discharge, highly reactive particles are produced that attack dirt accordingly. The concentration of aggressive particles is in the meantime much lower than in liquid cleaning agents. This is not detrimental to the cleaning work as in low-pressure gas discharges, the mobility of the particles is higher than in liquids by several orders of magnitude. Also hardly any hazardous waste substances are produced. When the discharge is switched off, the active particles react, for example by recombining. Plasma cleaning in production plants can thus replace solvent-based cleaning methods.

Thermostabile plastics are not suitable for conventional vapor sterilization. Conventional methods of low-temperature sterilization work with toxic or carcinogenic substances such as formaldehyde, ethylene oxide or peroxy acetic acid. With low-pressure plasmas a sterile surface can be obtained just by using a special mixture of oxygen and nitrogen at a power density of several mW / cm2.

The chemical activation of plastics for the purpose of overcoating or bonding generally requires harsh conditions. Thus chromic-sulfuric acid for ABS-plastics and sodium naphthalenide in tetrahydrofuran for fluorocarbons are used as activators. How-ever, these substances are flammable or toxic and must not be released! These treatment methods can be replaced by the use of various plasma processes.

Also the anti-felting of wool based on chloric compounds can be substituted by a more environmentally compatible plasma treatment. Moreover, plasma technology can also reduce environmental pollution in existing industrial processes by decomposing undesired (e.g. nasty smelling) or noxious waste gases by an appropriate plasma waste gas cleaning stage. This can also be applied to engine exhaust fumes.