Removal of molecular atmospheric pollutants by non-thermal plasmas is under
study since the beginning of the eighties. It has been shown that pulsed
electrical discharges, such as dielectric barrier or corona discharges, are
powerful means to eliminate Volatile Organic Compounds (VOCs) from the
ambient air, or to treat flue gases which contain nitrogen oxide. However it
is now recognised that, for several pollutants, the use of the plasma alone
does not allow a complete elimination of the undesirable molecule. For
example NO is oxidised in the air plasma to form other oxides like NO2
and N2O5, and reactions of oxygen atoms or hydroxyl radicals
produced by the discharge with VOCs can lead not only to H2O and
CO2 but to a number of by-products following the partial oxidation of
the molecule, which can be as undesirable than the compound to be initially
removed from effluents. This is particularly the case when the electrical
energy deposited in the gas flow must be kept as low as possible in order to
design a low energy cost equipment. As a result addition of a catalyst
together with the pulsed discharge is now investigated in various
laboratories in order to achieve a complete oxidation of VOCs, i.e. the
so-called de-COV process, or a complete reduction of NOX (NO and
NO$_{2})$ to produce N2 and O2, i.e. the so-called de-NOX
process, at low energy consumption. This paper is a short review of works
which have been done these last years in that domain, specifically on
NOX and some selected VOC molecules.