Rapid adsorption of PFAS: Application of Moringa oleifera seed powder encapsulated in alginate beads

Abstract

Adsorption processes are increasingly used for removing perfluoroalkyl and polyfluoroalkyl substances (PFAS) from aqueous systems. However, issues including slow adsorption kinetics, competition with other organics such as humic substances, and the fact that many commercial adsorbents are sourced from non-renewable materials can hinder their application. Calcium alginate beads with integrated Moringa oleifera (MO) seed powder were investigated as an alternative adsorbent for addressing these issues. The beads fabricated under different formulation conditions were evaluated as a proof of concept for their adsorption performance of two PFAS compounds (perfluorooctanesulfonic acid (PFOS) and perfluorobutanesulfonic acid (PFBS)) that are frequently found in PFAS-contaminated water. The beads exhibited fast kinetics with equilibrium reached in 30 min and a high adsorption capacity (up to 941.7 μ g g −1 ) for PFOS. The presence of humic acid (HA) did not greatly affect PFOS adsorption, demonstrating the potential of the beads as a promising adsorbent for long-chain PFAS removal from aqueous streams. The results of adsorption experiments and adsorbent characterization indicated that PFAS adsorption was dominated by hydrophobic interactions and hydrogen bonding. The adsorption efficiency appeared to be related to C–F chain length as the removal efficiency of the short-chain PFAS compound (PFBS) was found to be lower than 10%. • Alginate beads with integrated Moringa seed powder were used for PFAS adsorption. • High removal efficiency and rapid kinetics towards PFOS adsorption were achieved. • Adsorption was governed by hydrogen bonding and hydrophobic interactions. • Adsorption efficiency of the beads was related to C–F​ chain length of PFAS. • Presence of humic acid in the solutions did not significantly affect PFOS removal.