Surface characterization of oxidized biochar fibers derived from Luffa Cylindrica and lanthanide binding
SourceJournal of Environmental Chemical Engineering
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In the last years, biochar fibers derived from Luffa Cylindrica have emerged as promising adsorbent material for harmful heavy metal ions. Based on their unique vascular structure, they exhibit a large surface area and thus high capability for the adsorption of metal ions. We investigated the structure and chemical surface composition of the carbonized fibers after treatment with 8 M HNO3 prior and after Sm3+ binding in aqueous solutions. We used a large combination of classical analytical methods such as acid-base titration and batch-type adsorption experiments, as well as high-resolution microscopic and spectroscopic techniques like FTIR, XPS/REELS and SEM-EDX. The goal of the chemical oxidation is to functionalize the inner and outer surfaces of the biochar fibers by forming oxygen-containing active surface groups. Titration and spectroscopic data clearly reveal that anhydrides and carboxylic acids are acting as main surface groups to bind metal ions like Sm3+. We will show that the combination of high surface area and high density of carboxylic acid groups results in extremely high capacity of 2.4 mol kg-1 for the adsorption of Sm3+ ions. Therefore, the functionalization of biochar fibers offers a great potential to design advanced adsorbent materials for polluting heavy metal ions. © 2017 Elsevier Ltd. All rights reserved.