Lignin, tannic acid and gallic acid reduce sulfolane miscibility in water with implications for pollutant migration and water treatment

Sulfolane is a groundwater and surface water pollutant. Phenolic and polyphenolic compounds are found in plants and are ubiquitous in natural environments. Sulfolane is fully miscible in pure water, but its interactions with polyphenols decrease its miscibility. Lignin, a polyphenol immiscible in water, phase separates sulfolane from water, potentially impacting its migration in water. Sulfolane also interacts with tannic acid (a polyphenol) and gallic acid (a phenol), as seen by Fourier transform infrared spectroscopy and mechanistic simulations. These compounds are highly water-soluble and do not induce the macroscopic separation of sulfolane from water, but they form smaller clusters with sulfolane. Polyvinyl pyrrolidone flocculates gallic acid-sulfolane clusters, promoting their separation into larger droplets. Also, ferric iron forms complexes with gallic acid and sulfolane, promoting their sorption onto zero valent iron particles to achieve a removal of 224 ± 18 mg sulfolane/g zero valent iron within 30 s.