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

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.

Automated summary

The synthesis of RMBC composite through co-carbonization of red mud and waste sawdust is effective for Rhodamine B (RhB) oxidation, displaying both adsorption and catalytic effects. The activation of hydrogen peroxide by RMBC shows a low activation energy, and the dominant role of hydroxyl radical in solution for RhB oxidation is verified. The limitations of RMBC for heterogeneous catalysis may be overcome by regulating its alkaline feature, making it a green and sustainable approach for wastewater treatment.