Simultaneous removal of PFAS and cadmium from different water matrices using regenerable carbonaceous adsorbents

Abstract

Per- and polyfluoroalkyl substances (PFAS) frequently coexist with metal ions in industrial effluents and contaminated aquatic environments, yet their simultaneous removal remains poorly understood. This study examines the co-adsorption of three PFAS compounds (PFOA, PFOS, and GenX) and cadmium (Cd(II)) in concentrated water matrices using activated carbon (AC) and three biochars: hardwood-derived (BC-W) and sewage sludge-derived at 550 °C and 700 °C. Both AC and BC-W demonstrated superior adsorption due to enhanced surface properties. Adsorption followed the order PFOS > PFOA > GenX, influenced by hydrophobicity and functional groups. Cd(II) enhanced PFOS and PFOA adsorption through synergistic interactions but inhibited GenX adsorption due to competition. Cd(II) adsorption improved with increasing PFAS concentrations. A novel step-wise methanol-acid regeneration train selectively desorbed PFAS and Cd(II) in separate steps, achieving over 90% pollutant recovery and enabling adsorbent reuse for at least three cycles without performance loss. PFAS removal in groundwater remained effective, matching or exceeding performance in Milli-Q water. In wastewater, adsorption declined due to organic matter competition, particularly for PFOA, yet both adsorbents maintained strong performance across diverse matrices. This study highlights the potential of wood-derived biochar as a cost-effective alternative to activated carbon for PFAS and Cd(II) co-removal in contaminated effluents.