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

Abstract

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.