Oxidation of polystyrene aerosols by VUV-photolysis and/or ozone

Abstract

Aerosols of submicron polystyrene particles were oxidized by either vacuum-ultraviolet (VUV) irradiation in the presence of molecular oxygen (O(2)) and/or by ozone (O(3)). Different degrees of oxidation and oxidative degradation were reached by VUV-photolysis depending on radiant energy, O(2) and H(2)O concentrations in the bulk gas mixture as well as on particle diameter. The same functionalization was obtained by exposing the aerosol to O(3), however, oxidation, in particular oxidative degradation, was less efficient. The evolution of hydroxyl and carbonyl functions introduced was quantified by ATR-FTIR spectroscopy of filtered particles, and oxidative degradation of the polymer particles was confirmed by determining size and number of aerosol particles before and after oxidation. Efficiency analyses are based on the results of an O(3) actinometry and on an evaluation of the rate of absorbed photons by the aerosol particles in function of their size.

Up-scaling aerosol functionalization. Photo-oxychlorination using vacuum ultraviolet radiation (VUV)

“…In fact, diminution of particle diameter and concentration got faster as the residence time was increased. Expectedly, the same result was found with an increasing incident photon flux 9,11,12 .…”

“…Carboxyl functions are known to react with HO . by electron transfer and subsequent decarboxylation (reactions (12) and (13), respectively). (13) Although, O 3 is not photolyzed under the experimental conditions applied, it was found to oxidize polystyrene surfaces.…”

“…Depending on the project to be accomplished, the nanoparticles may be dispersed into water after this first functionalization, or may be guided into other reactors for a second or even third functionalization. The VUVphotochemical oxidation of polystyrene nanoparticles of defined diameter, the characterization of the oxidized particles and examples of a secondary functionalization have already been reported, [9][10][11][12] and the present work focalizes on the up-scaling of the first functionalization.…”

Atmospheric Micro and Nanoplastics: An Enormous Microscopic Problem

“…However, until now, only a limited number of studies investigated the reactivity of MP and NP towards atmospheric oxidants and further studies are needed to understand the fate of these plastics in the air. For example, Vicente et al [46] report the formation of degradation products by oxidation of PS nanoparticles in the presence of O 3 , while our previous study [50] estimates the reactivity constant between PS nanoparticles and • OH. To date, the effect of chemical degradation on plastic has only been studied for macro and mesoplastics, with special attention to plastic films, while little is known for MP and NP.…”

“…Once in the atmosphere, plastic particles are transported following air masses movements [17,43] and could act as ice nuclei, facilitating the formation of ice crystals [44]. The atmospheric oxidant capacity probably has a key role in their transformation, since MP and NP are exposed to sunlight [45], gas-phase oxidants (ozone, hydroxyl and nitrate radicals) [46][47][48][49] and aqueous phase oxidants (hydroxyl and nitrate radicals) [50] with higher concentrations compared to soil and water bodies. However, little is known about the fate and transformation of MP in the atmosphere.…”