Influence of neutral and charged species on the plasma degradation of the stearic acid

Abstract

In this work, stearic acid (SA) was degraded in an Ar-O 2 and Ar-H 2 post-discharge environment created by a plasma reactor with a microwave source and in an Ar, Ar-H 2 and Ar-O 2 DC (Direct Current) discharge environment created in a cathode-anode confined system. The afterglow region is useful for understanding the role of the chemically active species (O, O 2 , H and H 2 ). In contrast, the discharge region allows the observation of the effects of chemically active species, charged species (ions and electrons) and photons. The influence of these species on the grafting and etching of SA was evaluated by measuring the mass variation, mass variation rate and chemical composition. The results showed that when only chemically active oxygen species are present, the SA is preferentially grafted. However, when both photons and charged species are present, the SA is more efficiently etched. When the Ar-H 2 and Ar environments are utilized; the SA is not efficiently degraded.

Evaluation of sample temperature and applied power on degradation of stearic acid in inductively coupled radio frequency plasma

“…The stearic acid (SA) has been used in recent studies as model of organic contaminant [16][17][18][19] . This molecule (C 18 H 36 O 2 ) is a linear chain of 18 carbons with an acid function on the extremity, so the reactions pathways are restricted to interaction of the plasma with the C-C, C-H, C=O and C-O-H functions.…”

“…It is known 17,21,22 that to generate degradation with oxygen it is necessary to create radicals from SA molecules, and it would take some time to create volatile compounds from the original SA molecule [16][17][18][19] . In this way, since radicals generation rate it is presumed to be constant, as suggested by MVR (Figure 8) and temperature ( Figure 7) results, but the volatile compounds generation rate shows a time dependence, a constant MVR only will be reached once the surface of sample is covered with both reactions in equilibrium rate.…”

Treatment of Glycine and Proline in Late Ar‐O2 Afterglow

“…Then, we demonstrated that phenyl rings of carbons in biphenyl molecules (C 12 H 10 ) can be opened by the singlet state O 2 (a 1 Δ g ) . More recently, treatments in direct plasmas were also considered …”

Dependence of E-H transition in argon ICP discharges for treatment of organic molecules

“…The present work is a complement of previous studies from MAFRA et al [18], BERNARDELLI et al [19], FARIAS et al [20] where the mechanisms of plasma degradation of organic molecules are studied. The set of experiments here presented aims to gain a better understanding in this issue, by investigating the differences on degradation of hexatriacontane in E or H modes, monitoring the by-products of the treatments.…”