Upcycling of Waste Plastics into Carboxylic Acids for Biodegradable Surfactants

This work outlines a process for producing high-purity (>95%) carboxylate surfactants from post-consumer recycled high-density polyethylene (PCR-HDPE). The approach involves the thermal depolymerization of PCR-HDPE via pyrolysis, followed by fractional distillation to isolate C9-C14 olefins. These olefins undergo hydroformylation using cobalt carbonyl catalysts to generate aldehydes, which are subsequently oxidized to carboxylic acids using Pinnick oxidation under mild aqueous-phase conditions. Neutralization of the resulting carboxylic acids with sodium hydroxide produces plastic-derived carboxylate surfactants (PDCs) in the form of sodium carboxylates. Subsequent purification steps ensure surfactant-grade purity and enable accurate assessment of physicochemical properties. The resulting PDCs are evaluated for critical micelle concentration (CMC), foamability, surface tension reduction, and calcium ion tolerance, demonstrating competitive behavior with conventional anionic carboxylate surfactants. This route provides a sustainable alternative for surfactant production, reducing reliance on fossil-derived feedstocks and valorizing plastic waste streams through chemical upcycling.