Biochar/α‐Fe 2 O 3 /γ‐Fe 2 O 3 Heterjunction Composite for Photocatalytic Removal of Amino Black

Abstract Herein we synthesized biochar/iron oxide composite (C/α‐Fe 2 O 3 /γ‐Fe 2 O 3 ) by two‐step calcination method. The prepared C/α‐Fe 2 O 3 /γ‐Fe 2 O 3 had a highly pure and a concentration ratio of α‐Fe 2 O 3 and γ‐Fe 2 O 3 about 1 : 1. The optical properties of as‐synthesized C/α‐Fe 2 O 3 /γ‐Fe 2 O 3 show a lower bandgap energy (1.90 eV) than that of pure C/α‐Fe 2 O 3 (2.02 eV). The effects of different biochar composite catalysts on the removal of amino black were investigated. Upon illumination, the total removal rate of amino black dye by C/α‐Fe 2 O 3 /γ‐Fe 2 O 3 catalyst reached 98 %, which was about 1.7 times that of C/α‐Fe 2 O 3 . In addition, the coercivity and the remanence intensity of C/α‐Fe 2 O 3 /γ‐Fe 2 O 3 is respectively 1.81 times and 7.17 times that of C/α‐Fe 2 O 3 . The catalyst could be magnetically separated and reused for five times with a slight loss of its reactivity. The study of biochar composite provides a new direction for the removal of toxic organic dye in wastewater.