Photo-fenton degradation of poly(Ethyleneglycol)

Abstract

Polietilenoglicol (PEG) foi fotooxidado usando o sistema foto-Fenton e comparando com a reação no escuro. Os produtos foram analisados por GPC e HPLC. As amostras tratadas na ausência de luz necessitaram 490 min para que a -M w decrescesse em 50%, enquanto que sob irradiação UV essa mesma proporção foi obtida em 10 min. O decaimento exponencial de -M w com um concomitante aumento na polidispersividade e o número de quebras de cadeia caracteriza um mecanismo de quebra de cadeia aleatório. Os produtos da degradação de PEG em ambos os casos mostram a presença de produtos de massa molecular menor, incluindo etilenoglicóis menores e o ácido fórmico. O mecanismo da fotodegradação corresponde a processos consecutivos, onde etilenoglicóis de maior massa molar geram outros de menor massa, envolvendo quebras sucessivas das cadeias do polímero. O estudo demonstra que o processo de foto-Fenton com irradiação UV é um bom método para a decomposição de PEG.Polyethyleneglycol (PEG) was photooxidized in a photo-Fenton system and results compared with the dark reaction. The products were analysed using GPC and HPLC. In the absence of light, PEG samples needed 490 min to reduce their -M w by 50%, whereas under UV irradiation, only 10 min were necessary. The exponential decay of -M w with a concomitant increase in polydispersity and number of average chain scission, characterized a random chain scission mechanism. The degradation products of PEG in both systems showed the presence of lower molecular weight products, including smaller ethyleneglycols and formic acid. The mechanism involves consecutive processes, were the larger ethyleneglycols give rise, successively, to smaller ones. This suggests that the mechanism involves successive scissions of the polymer chain. Irradiated samples decomposed faster than those kept in the dark This study proves that the foto-Fenton method associated with UV-light is a good reactant for PEG photodegradation.

Polyolefins and the environment

“…These will react with oxygen, thus producing peroxy radicals and subsequently hydroperoxides, which are thermally and photochemically unstable and will induce further breakdown. Again, polymer degradation results in chemically irreversible reactions or physical changes, the knowledge of the processes involved is important to prevent the premature failure of these materials [59].…”

An Evaluation of Osmotic Technique Under Ultraviolet Germicidal Irradiation Exposure

“…Das & Gupta (2005) noted that some changes in the FTiR spectrum of PEG when exposed under UV lamp for more than 1 hour. In the presence of oxidation chemicals such as hydrogen peroxide and titanium oxide, the degradation of PEG in aqueous form was found to occur at shorter periods of exposure [25] [26].…”

Data on Specific Polymers

“…560 In the absence of light, PEG samples needed 490 min to reduce their M w by 50%, whereas under UV irradiation, only 10 min were necessary. 560 Degradation products obtained in both systems included low molecular weight PEG and formic acid. 560 This suggests that the mechanism involves successive scissions of the polymer chain.…”

“…560 Degradation products obtained in both systems included low molecular weight PEG and formic acid. 560 This suggests that the mechanism involves successive scissions of the polymer chain. 560 Photodegradation of poly(ethylene glycol) was conducted in aqueous solutions by means of the photo-Fenton and H 2 O 2 /UV processes.…”