Taloring sawdust derived hydrochar via red mud for cadmium removal: Electron transfer insight and recyclability...

Iron modified bio-adsorbents gained a lot of attention recently, especially some iron-contain wastes were employed for fabrication. However, the influence of indigenous impurities in wastes was merely investigated. In this study, red mud (RM), an iron-rich by-product was employed as source to prepare Fe modified hydrochar (RM@HC) by a facile hydrothermal method, and then employed for Cd(II) removal from wastewater. The RM@HC demonstrated excellent adsorption performance with capacity of 598.26 mg/g and maintained with a wide pH range. Further, the removal mechanisms were comprehensively elucidated and calculated, which was attributed to the various interactions include physical adsorption (29.07%), reduction (27.61%), and co-precipitation (25.81%). Moreover, the abundant metal oxides in RM@HC contributed to the removal through co-precipitation by building a highly alkaline environment. This work provided a promising choice for the sustainable reutilization of RM by designing a green bio-adsorbent to remove heavy metals from wastewater.