Computation-Guided Removal of 6PPD from End-of-Life Waste Tires

The increasing rate of fish morbidity and grave concerns
regarding
the long-term implications on human health with exposure to N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) from waste tires have brought
to light the urgency to isolate this compound in the environment.
Toward this end, we focus on removing 6PPD from waste tires by using
solvent-based extraction. However, a major challenge in solvent-based
extraction is identifying a conducive solvent that is nontoxic, efficient,
and economically and environmentally feasible. Thus, we developed
a physics-informed computational methodology for identifying conducive
solvents to extract 6PPD from waste tires. The methodology spans various
scales from quantum mechanical calculations to process development
and environmental impact. Starting with a database of 2000+ solvents,
we sequentially screened the database to identify 7 candidates. This
was followed by a detailed investigation of these candidates from
economic and environmental perspectives. We subsequently performed
experimental verification of these solvents for the extraction of
6PPD from crumb rubber using batch microwave-assisted extraction.
The developed physics-based methodology could be applied to solvent
selection in other applications as well.