Enhanced photocatalytic performance for phenol degradation using ZnO modified with nano-biochar derived from cellulose nanocrystals

Abstract

Phenol, considered as a stable and refractory organic pollutant, has posed an increasing threat to the environment and human health. Herein, the ZnO was regulated with nano-biochar (CCNC) derived from cellulose nanocrystals (CNCs). The CCNC/ZnO photocatalysts were fabricated via in situ precipitation and carbonization, in which CNCs served as both the templates and carbon source. Meanwhile, Zn2+ ions deposited on the surface of rod-like CNCs by electrostatic interaction. Subsequently, homogeneous dispersed ZnO nanoparticles were anchored onto the surface of CNCs, decreasing the ZnO nanoparticles size. As the CNCs transformed into CCNC, the resultant CCNC/ZnO photocatalysts demonstrated excellent degradation efficiency to phenol, corresponding to 99.8% within 90 min. Additionally, the CCNC/ZnO photocatalysts also displayed a satisfactory stability for five cycles without significant performance being decreased. The calculating and experimental results demonstrated that the conjugated graphitic structures of CCNC effectively reduced the band gap of ZnO from 3.26 to 2.96 eV. Besides, the CCNC remarkably promoted photogenerated electron-hole pairs separation and transfer, thereby improving the photodegradation efficiency for phenol. Furthermore, the efficiency for phenol photodegradation was comprehensively influenced by a combination of the ratio of photocatalyst, initial phenol concentration and catalyst dose, and pH value. This study broadened the application of CNCs in the field of photocatalysis, which provided a new perspective for the preparation of highly efficient photocatalysts using CNCs derived nano-biochar as a template and charge-transport pathway.