Development of a three-dimensional photoelectrocatalytic reactor packed with granular sludge carbon photoelectrocatalyst for efficient wastewater treatment

• A novel 3D-PER is developed to degrade RhB using GSCs as photoelectrocatalysts. • 3D-PER presents superior performance with the synergy of EC and PC. • The hollow structure of GSC-15 benefits to RhB degradation. • PC initializes RhB decolorization, while EC is critical for RhB mineralization. • The toxicity of 3D-PER effluent is reduced by 90%. The application of photocatalysis/electrocatalysis in wastewater treatment is constrained by their inherent drawbacks, such as the low utilization efficiency of light for photocatalysis, and the diffusional limitations for electrocatalysis. In this work, a novel three-dimensional photoelectrocatalytic reactor (3D-PER) is developed to degrade Rhodamine B (RhB) simulated wastewater. The granular sewage sludge carbons (GSCs) are fabricated and filled into the 3D-PER as particle catalysts, which exert both photocatalysis and electrocatalysis. The decolorization efficiency of RhB is over 95% in the 3D-PER with the synergy of electrocatalysis and photocatalysis. Especially, the hollow structure of GSC-15 improves the decolorization efficiency of RhB, and exhibits a stable treatment performance over 11 continuous cycles. GSC-15 has hierarchical pore structure with abundant active sites, showing a higher degradation rate to RhB than GSC. The contributions of photocatalysis and electrocatalysis to RhB degradation are identified, that photocatalysis primarily initializes decolorization, while electrocatalysis plays a critical role in mineralization. Meanwhile, the toxicity of 3D-PER effluent is largely reduced for the efficient decomposition of toxic intermediates. This study demonstrates the efficacy of 3D-PER in refractory wastewater treatment, benefitting to the promotion of 3D-PER in environmental applications.