Development of Fe/HNT and Fe/HNT-Al₂O₃ composite catalysts and application in successive treatment processes for pharmaceutical industry wastewater

The pharmaceutical industry wastewater (PIW) was treated by successive use of electro Fenton (EF) and photocatalytic oxidation (PcO) processes. Nano-particular powdered Fe/HNT (Iron/Halloysite nanotube) heterogeneous semiconductor catalyst was initially produced with Fe(OH)₃ sludge modification precipitated after EF process. Thus, photocatalyst material was produced from the waste sludge and used in the PcO process. Photocatalyst Fe/HNT powder was immobilized on a three-dimensional (3D) reticulated Al₂O₃ ceramic support to enable rapid recovery of the catalyst from the PcO reactor system. Particle morphology and chemical configuration of the heterogeneous catalysts were analyzed with SEM (Scanning Electron Microscopy)-EDS (Energy-Dispersive X-ray spectrometry), UV-DRS (Ultraviolet Diffuse Reflectance Spectra) and XRD (X-ray diffraction). The Fe/HNT layer was calcined at three different temperatures (350, 450 and 600 °C). The optimum temperature was determined as 350 °C for better photocatalytic performance and practical reasons such as energy consumption. The successive use of EF + PcO processes for degradation of three different PIW samples was investigated by using two catalyst forms (nanoparticle and reticulated) and light sources (visible and sun light). The max TOC removal efficiency by EF + sun light-PcO (with Fe/HNT) successive treatment process was obtained as 78.4 %. Besides, the energy consumption value was calculated for optimum process state and calculated as 48.8 kWh/kg TOC at the EF + sun light-PcO (with Fe/HNT) successive treatment process.