Fabrication of Fe-doped biochar for Pb adsorption through pyrolysis of agricultural waste with red mud.

Synthesis of metal-doped biochar have gained prominence due to their adsorption capability for heavy metal(loid)s. In this study, iron-doped biochar (Fe-BC) was fabricated through pyrolysis of waste mushroom substrate (WMS) with red mud (RM). The synthesised Fe-BC was employed as an adsorbent for Pb removal. During pyrolysis of WMS, introducing RM contributed to the enhanced syngas formation, this observation was attributed to the catalytic function of Fe species in RM. The Fe-BCs were made at three different temperatures (500, 600, and 700 °C), and their adsorption capabilities for Pb were evaluated. Among the prepared Fe-BCs, Fe-BC fabricated at 700 °C (Fe-BC-700) demonstrated the highest Pb adsorption performance (243.07 mg g^-1). This performance primarily stemmed from the presence of zero-valent Fe and surface functional groups (-OH) in Fe-BC-700. Pb removal by Fe-BC-700 was dominated by surface precipitation and complexation mechanisms. Therefore, this study highlights a promising approach for producing an effective adsorbent for Pb removal from industrial wastewater by utilizing wastes such as RM and WMS.