Co-carbonization of red mud and waste sawdust for functional application as Fenton catalyst: Evaluation of catalytic activity and mechanism

Abstract

Synthesis of red mud/biochar (RMBC) composite was conducted by facile co-carbonization of red mud and waste sawdust. Multiple characterizations verify the reduction of ferric oxide and the formation of graphitic biochar with defects. Hydrogen peroxide activation by RMBC was investigated for Rhodamine B (RhB) oxidation. RMBC displays both adsorption and catalytic effects for RhB removal. Catalytic oxidation of RhB is effectively obtained at pH below 2.2. RhB oxidation is slightly improved with growing temperature. RhB oxidation in RMBC/H2O2 system obeys the pseudo first-order kinetic, and the low activation energy of 56 kJ/mol implies the effective hydrogen peroxide activation by RMBC. Associated with the determinations of radical and iron leaching, the dominant role of hydroxyl radical in solution is verified for RhB oxidation. The limitation of RMBC for heterogenous catalysis may be solved by the regulation of alkaline feature. RMBC processes special properties of red mud and biochar, and its application to wastewater treatment provides a green and sustainable approach obeying the “waste treating waste” concept.