A novel nano-cerium oxide functionalized biochar composite for degradation of organic dye: insight of the photocatalysis mechanism.

Recently, visible-light-driven photocatalysis attracts much concerns in the remediation of environmental organic pollutants. In this study, the cerium doped biochar was fabricated through the hydrothermal method, and served as an efficient photocatalyst towards rhodamine B degradation under visible light irradiation. Almost 100% of rhodamine B was removed by 2.0 g·L cerium doped biochar after 60 min of visible light irradiation at pH 3, but only about 25.50% and 29.60% of rhodamine B was removed by cerium dioxide and biochar under identical conditions. The degradation process coincided well with the pseudo-first-order kinetic model, and the photodegradation rate constant of cerium doped biochar was 0.0485·min, which was respectively 97 and 44 times that of biochar (0.0005·min) and cerium dioxide (0.0011·min). According to the trapping experiments and electron spin resonance spectroscopy analysis, h, O∙ and ∙OH all participated in the degradation of rhodamine B in the cerium doped biochar photocatalytic systems, and the function of h and ∙OH was dominated. Consequently, the biochar could not only be an excellent carrier for supporting cerium dioxide, but also greatly improved its photocatalytic activity. The band gap of cerium doped biochar was narrower than cerium dioxide, which could improve the separation and migration of photogenerated electron-hole pairs under visible-light excitation, thus ultimately enhanced the degradation of rhodamine B. This work provided a deeper understanding of the preparation of biochar-based photocatalyst and its application in the remediation of environmental organic pollution.