ABSTRACT
The fabrication of a Z-scheme heterojunction photocatalyst can effectively modulate the electron transfer and separation of photoinduced charge carriers to enhance photocatalytic performance. Here, we demonstrate a direct Z-scheme BiOCl-phosphotungstic acid (BiOCl-HPW) heterojunction, fabricated via a one-step hydrothermal synthesis, as a highly active and stable photocatalyst for the photodegradation of tetracycline. BiOCl-HPWs result in a dramatic improvement in visible-light utilization and photogenerated e- and h+ separation, as well as a decrease in the electrical resistance by the addition of HPW. Notably, the BiOCl-HPW heterojunction with optimized phosphotungstic acid (HPW) content achieved an outstanding photodegradation rate of tetracycline (0.0195 min-1). A reasonable Z-scheme photocatalytic mechanism based on the analysis of band structure and monitoring of active radicals is proposed. This study highlights the potential implications of the BiOCl-HPW heterojunctions in the photodegradation of other toxic chemicals and photocatalytic studies.
ABSTRACT
The removal of heavy metals, especially from wastewater, has attracted significant interest because of their toxicity, tendency to bioaccumulate, and the threat they pose to human life and the environment. Many low-cost sorbents have been investigated for their biosorption capacity toward heavy metals. However, there are no reports available on the removal of Pb(II) from aqueous solution by of L. seed husk ash. In this work, use of seed husk ash for the removal of Pb(II) from wastewater was investigated as a function of contact time and the initial pH of the solution. Kinetics and equilibrium constants were obtained from batch experiments. Our study shows that the adsorption process follows pseudo-second-order kinetics. Moreover, the Langmuir absorption model gave a better fit to the experimental data than the Freundlich equation. The maximum adsorption capacity of the husk ash was 263.10 mg g at 298 K and pH 5.0, and this is higher than the previously reported data obtained using other sorbents. The results obtained confirm that seed husk ash is an effective sorbent for the removal of Pb(II) from aqueous solution. Analysis of infrared spectra of the husk ash after absorption of Pb(II) suggested that OH, C=O, C-O, Si-O-Si, and O-Si-O groups were important for the Pb(II) ion removal. Moreover, practical tests on this biosorbent for Pb(II) removal in real wastewater samples successfully demonstrated that seed husk ash constitutes an efficient and cost-effective technology for the elimination of heavy metals from industrial effluent.
