| dc.description.abstract | The rapidly accumulating post-consumer polyethylene terephthalate (PET) plastics
pose a great threat to our environment as they constitute one of the most used products in
our day-to-day life. As a result, degradation of PET and recycling has become the focus of
considerable interest in the last decade. Hydrolysis of PET is very challenging as they are
extremely resistant to both biotic and abiotic degradation. A technically and economically
feasible approach to degrade PET waste from the environment is highly desirable.
Physicochemical pre-treatment can play an important role in making PET more degradable
by changing their surface properties. Direct recycling of segregated PET has problems of
contamination of additives and components used in various PET products. PET hydrolysis
however can lead to recovery of the monomers terephthalic acid (TPA) and ethylene glycol
(EG) as well as the dimers bis(2-hydroxyethyl) terephthalate (BHET) and mono(2-
hydroxyethyl) terephthalate (MHET) which can be reused for making new PETs. This can
potentially solve the difficulties associated with PET recycling and lead to a circular
economy. The present study reports the effect of ozone and ultrasound pretreatment on
both enzymatic and chemical hydrolysis of PET. The results showed that combination of
ozone pretreatment followed by ultra-sonication during enzymatic hydrolysis using HiC
cutinase enzyme resulted in almost 9-fold increase in TPA and EG recovery compared to
enzymatic hydrolysis of untreated PET. However, the long reaction time in enzymatic
hydrolysis prompted us to investigate chemical hydrolysis. Although, chemical hydrolysis
of pretreated PET films using methanolic sodium hydroxide as solvent resulted in 80%
weight loss (at 50C, atmospheric pressure), the recovery of monomers was relatively not
as efficient as enzymatic hydrolysis. Size reduction of the PET films followed by chemical
hydrolysis gave the highest (90%) breakdown, but it is a very energy intensive process. | en_US |
