Constructed palladium-anchored hollow-rod-like graphitic carbon nitride created rapid visible-light-driven debromination of hexabromocyclododecane

Abstract

The high-efficiency photocatalytic debromination of hexabromocyclododecane (HBCD) as new POPs and discovery of involved mechanisms remain a challenge. Herein, challenging Pd-anchored hollow-rod-like-g-C3N4 (Pd/HR-g-C3N4) was constructed as visible-light-driven photocatalyst. Complete destruction of (±)-α, (±)-β and (±)-γ-HBCD with 92.6 % bromine-removal was achieved at 60 min in optimal system of anaerobic methanol-water (70:30) mixture with 0.5 % Pd/HR-g-C3N4, being superior to most studied HBCD catalytic systems. The higher photocatalytic reduction performance is contributed to enhanced photoexcited-carriers separation and more negative conduction band arising from distinctive 1D-cavity of HR-g-C3N4, and surface-atomically dispersed Pd. A never-reported degradation pathway in which hydrodebromination and addition ring-opening synergistically occur is proposed according to identified products of ten saturated chain alkanes, C12H19Br5 and C12H19Br7. Ulteriorly, hydride-transfer resulted in rapid hydrodebromination of HBCD over Pd/HR-g-C3N4, where H chiefly derives from methanol instead of water although they synergistically promoted e− utilization. This provided a valuable sight into the cost-effective pollution-removal of HBCD.