Highly efficient solar-light-driven photocatalytic degradation of pollutants in petroleum refinery wastewater on hierarchically-structured copper sulfide (CuS) hollow nanocatalysts

Hierarchically-structured CuS hollow nanocatalysts (HS-CuS-HNCs) were prepared in high yield (>95%) by a simple chemical solution deposition method at room temperature, and then used to photocatalytically degrade pollutants in petroleum refinery wastewater (PRW) under solar light radiation. Compared to bulk-size CuS catalyst, HS-CuS-HNCs with narrower band gap (Eg = 0.96 eV) exhibited strong visible-light absorption, highly enhanced quantum efficiency and large specific area (101.5 m2 g−1) characteristics. HS-CuS-HNCs showed significantly enhanced activity for the degradation of pollutants under both artificial and real solar light source (about 66% of COD in PRW was removed in 3 h degradation under conditions of 1.0 g/L catalyst and 7.6 pH). The activity of HS-CuS-HNCs was drastically enhanced further in the presence of hydrogen peroxide (H2O2) (98% of COD in PRW was removed in 2 h under conditions of 1.0 g/L catalyst, 3.0 g/L H2O2 and 7.6 pH), which was attributed to the synergistic effect between HS-CuS-HNCs and H2O2, leading to the enhanced quantum efficiency and production of more reactive oxygen species (ROS). Radical-quenching experiments revealed that the contributions of ROS to COD reduction in PRW followed the sequence: superoxide anion (•O2−) > singlet oxygen (1O2) > hydroxyl radical (•OH). Important factors such as catalyst dose, H2O2 dose and initial pH had influences on the degradation efficiency. This work provided a hierarchically-structured non-TiO2-based nanophotocatalyst with high performance for efficiently utilizing solar energy to oxidatively degrade pollutants in PRW fast and deeply.