With the wide application of biodegradable plastics in the fields of packaging, agriculture and medical care, the environmental impact of their waste and resource wastage are becoming more and more prominent. Although PBAT has good biodegradability, its production cost is much higher than that of traditional plastics such as PE and PP, and the absence of recycling mechanisms leads to a large waste of resources.
Existing PBAT treatment methods, such as mechanical recycling, industrial composting, and enzymatic degradation, are often limited to specific scenarios and are not very efficient. In contrast, chemical recycling provides a way to convert and upgrade waste PBAT materials into higher value chemicals. However, chemical recycling studies on biodegradable plastics are relatively few and mostly focus on biodegradability and environmental behavior.
In view of the structural similarity between PBAT and PET (polyethylene terephthalate), this study proposes a new route for the rapid degradation of PBAT by a combined 1,4-butanediol (BDO)-alkali method based on the chemical recycling method of PET, aiming to provide new ideas and methods for the sustainable management and resource utilization of PBAT waste.
The first step in this study was the rapid degradation of PBAT. Namely, the 1,4-butanediol-alkali combination treatment method was able to achieve efficient degradation of PBAT plastics in just one hour, reaching a degradation rate of more than 99%.
BDO is a good solvent that promotes the solubilization of PBAT and facilitates the degradation reaction. The method using high concentrations of BDO promoted the self-precipitation of PTA and AA from solution, which were then easily separated by simple filtration.
During the experiment, the degradation of PBAT firstly increased and then decreased with the increase of BDO concentration, and peaked at about 70%.
However, its high viscosity led to a decrease in the degradation rate when its concentration exceeded 70%.The degradation rate of PBAT increased with increasing temperature. At 130 °C, the degradation rate of PBAT increased from 21.2% at 20 min to 95.3% at 50 min and reached more than 99% at 60 min with the increase of reaction time.
This achievement is notable not only for its high efficiency, but also for the fact that it reduces the need for additional chemicals and energy throughout the degradation process by facilitating the efficient separation of hydrolysis products through a high concentration of BDO, avoiding the consumption of resources that would be required in a conventional acid and alkaline treatment step.
The second step of this study was the conversion of PBAT hydrolysate to high-value succinic acid. A two-step rapidly (within 10 min) prepared nickel foam-loaded NiOOH electrocatalyst was developed, which not only showed high selectivity and efficiency in the conversion of oxidized BDO to butanedioic acid, with a high Faraday efficiency achieved at a lower potential, but also showed the same high efficiency in the conversion of BDO monomer in the hydrolysis product of PBAT
