Study on PFAS removal by different forms of iron-modified biochar: Adsorption effects and catalytic activity

Iron-modified biochar has been investigated as an adsorbent and catalyst for the removal of per- and poly-fluoroalkyl substances (PFAS) from wastewater. However, the influence of different forms of iron-modified biochar on the adsorption effect and catalytic activity of PFAS is unclear. This study prepared four distinct forms of biochar: Fe 0 /BC, Fe₂O₃/BC, Fe(OH)₃/BC, and Fe₃O₄/BC. Their adsorption capacities for PFOS, PFOA, PFHxA, PFBA, and PFBS were compared. The catalytic activity towards peroxymonosulfate (PMS) and the contribution made by reactive radicals were investigated. The results showed that for long-chain PFAS, all three biochar samples except Fe(OH) 3 /BC showed high adsorption capacity. For short-chain PFAS, the adsorption capacities of Fe 2 O 3 /BC and Fe 3 O 4 /BC were much higher than those of the other two biochar types. Fe 3 O 4 /BC showed better catalytic activity for PMS activation. SO 4 · − and ·O 2 - played a major role in the whole PFAS removal process, and ·OH contributed less to PFAS removal. Fe 3 O 4 /BC is an eco-friendly, low-cost, and highly efficient adsorbent material and catalyst with excellent recycling ability. It has good application prospects for removing PFAS contamination from water, especially for short-chain PFAS, and has more advantages than other forms of iron-modified biochar.