Synthesis and evaluation of Fe₃O₄-impregnated activated carbon for dioxin removal

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/PCDFs) are highly toxic organic pollutants in soils and sediments which persist over timescales that extend from decades to centuries. There is a growing need to develop effective technologies for remediating PCDD/Fs-contaminated soils and sediments to protect human and ecosystem health. The use of sorbent amendments to sequester PCDD/Fs has emerged as one promising technology. A synthesis method is described here to create a magnetic activated carbon composite (AC-Fe₃O₄) for dioxin removal and sampling that could be recovered from soils using magnetic separation. Six AC-Fe₃O₄ composites were evaluated (five granular ACs (GACs) and one fine-textured powder AC(PAC)) for their magnetization and ability to sequester dibenzo-p-dioxin (DD). Both GAC/PAC and GAC/PAC-Fe₃O₄ composites effectively removed DD from aqueous solution. The sorption affinity of DD for GAC-Fe₃O₄ was slightly reduced compared to GAC alone, which is attributed to the blocking of sorption sites. The magnetization of a GAC-Fe₃O₄ composite reached 5.38 emu/g based on SQUID results, allowing the adsorbent to be easily separated from aqueous solution using an external magnetic field. Similarly, a fine-textured PAC-Fe₃O₄ composite was synthesized with a magnetization of 9.3 emu/g.