Pyrolysis of Fe-doped Perilla straw for value-added chemical production and functional biochar for Cr(VI) removal from water

Abstract

Cr(VI) contamination in water resources presents a critical environmental and public health challenge, demanding immediate and effective remediation strategies. Conventional Cr(VI) treatment technologies are often energy-intensive and may result in secondary pollution. This study explores a sustainable Cr(VI) remediation strategy using a zero-valent iron (Fe0)-biochar composite synthesized through FeCl3-assisted pyrolysis of Perilla straw, achieving dual environmental benefits: agricultural waste upcycling into value-added products and Cr(VI) remediation. Thermogravimetric analysis results revealed that FeCl3 pretreatment altered the thermal degradation pathway of (hemi)cellulose in Perilla straw, promoting the production of furfural-rich pyrogenic oil and enhanced H2 generation while suppressing CO formation. The evolved H2 facilitated the carbothermic reduction of Fe moieties in Perilla straw to Fe0. Batch experiments, column tests, and composite characterizations revealed that the integration of functional groups of biochar with Fe0 synergistically enhanced Cr(VI) removal by combining chemisorption via surface complexation, Fe0-mediated redox reduction, and insoluble Cr(III)hydroxide formation. These findings highlight that the pyrolysis of FeCl3-treated Perilla straw enables cleaner production of H2 gas, industrial chemical resources, and effective materials for environmental remediation.