Recycling Iron‐Containing Sludges from the Electroflocculation of Printing and Dyeing Wastewater into Anode Materials for Lithium‐Ion Batteries

Abstract Iron‐containing sludges (DW/Fe) were prepared by the electroflocculation of industrial printing and dyeing wastewater (DW). To investigate the formation process and the properties of the DW/Fe sludges and their application in anode materials in Li‐ion batteries, the DW/Fe sludges were compared to three other sludges (MB/Fe, RB/Fe, Ta/Fe) prepared from model solutions that contained either methyl blue (MB), rhodamine B (RB), or tartrazine (Ta). The DW/Fe sludges were calcined at 500 °C under N 2 to form iron oxide/carbon composite C‐DW/Fe. The composition and structure of the sludges and the C‐DW/Fe composite were analyzed by using FTIR spectroscopy, XRD, thermogravimetric analysis, SEM, TEM, and X‐ray photoelectron spectroscopy, and their performances as anodes of Li‐ion batteries were studied by adding different proportions of conductive agent (super P® conductive carbon black). Our results show that the sludges are a complex mixture of Fe 3 O 4 and organic matter. The specific capacity and stability can be improved during the charge–discharge test by increasing the amount of carbon black. Importantly, this improvement is more pronounced on DW/Fe that does not require high‐temperature carbonization, which means that the sludges cannot only protect the environment and avoid the waste of resources but also can be used directly and widely in decentralized energy storage devices.