Iron-carbon composite from carbonization of iron-crosslinked sodium alginate for Cr(VI) removal

It is vital to prepare iron (Fe)-containing porous carbonaceous materials (Fe/C) with high reductive Fe content, large specific surface area, and abundant oxygen-containing functional groups to alleviate the toxicity and mobility of Cr(VI) from both reduction and adsorption. In this study, Fe-crosslinked sodium alginate (SA-Fe) was carbonized to prepare an Fe/C composite (SA-Fe-C) with high content of reductive Fe content for Cr(VI) removal via regulating the amount of crosslinked FeSO4. With increasing FeSO4 from 1 mmol to 10 mmol, the main Fe components in the Fe/C composite transformed from FeS and Fe3O4 to Fe(0), and the content of reductive Fe increased from 81.2 mg to 120 mg. The optimal dosage of FeSO4 was 10 mmol, at which obtained SA-Fe-C with higher content of reductive Fe (i.e., Fe(0) FeO, and FeS), specific surface area, and rich oxygen-containing functional groups. The prepared SA-Fe-C exhibited a high removal capacity for Cr(VI) (100 mg/g) due to the high content of reductive Fe, which accounted for 84.0% of Cr(VI) (20 mg/L) reduction. The adsorption resulted from pore-filling and cation bridging and/or strong charge-assisted H-bonding contributed to 16.0% of the total removal of Cr(VI). Our findings showed that Fe/C composite with high content of reductive Fe and large specific surface area can be regulated and has a promising application potential in remediating heavy metals contaminated water.