Sorption of per- and polyfluoroalkyl substances by lignin in pulp and paper wastewater

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals commonly found in the environment. PFAS pose multifaceted challenges including identifying sources and exposure pathways, detecting and quantifying their presence, characterizing their fate and transport, and assessing their risks. PFAS and fluorotelomer polymers can be found in the pulp and paper (P&P) wastewater systems, but their behavior remains poorly understood. The constituents of P&P waste include lignin hydrolysis products, hence PFAS interactions with lignin likely affect PFAS removal efforts. This study employed quantitative ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-MS/MS) to investigate the sorption-desorption capacity and mechanisms of PFAS interaction with lignin. PFAS with sulfonate functional groups displayed higher affinity for lignin (solid phase) based on their partitioning coefficient (K_d), while PFAS with carboxylate head groups persisted in the P&P wastewater (aqueous phase). Sorption to lignin exhibited an increase with chain length (CF₂)_n among compounds with the same functional group. Long-chain (C ≥ 6) PFAS demonstrated higher sorption compared to short-chain (C ≤ 5) homologs. The sorption-desorption capacities, partitioning coefficients, and kinetics of PFAS reported in this study can facilitate predictive models for PFAS and assist in the development of efficient P&P waste treatment and management.