Photocatalytic degradation of local dyeing wastewater by iodine-phosphorus co-doped tungsten trioxide nanocomposites under natural sunlight irradiation.

In the present work, one-step green synthesis of WO₃ based on the interaction of ammonium paratungstate and Spondias mombin leaves extract is reported. Different concentrations of iodine and phosphorus in the range of (2%, 5% and 10%) were firstly incorporated into the prepared WO₃ nanoparticles to obtain Iodine doped and Phosphorus doped WO₃ nanoparticles respectively. Subsequently, iodine and phosphorus co-doped WO₃ nanocomposites was prepared using a wet impregnation method followed by calcination at high temperature. The nanomaterials were characterized by HRSEM, HRTEM, BET, UV-Visible, EDS, XRD and XPS. The photo-oxidation of dyeing wastewater by the synthesized WO₃ nanomaterials were tested and assessed using Total organic carbon (TOC) and Chemical oxygen demand (COD) as indicator parameters. XRD and HRSEM analysis demonstrated the formation of only monoclinic phase of WO₃ irrespective of the dopants. The UV-Visible diffuse reflectance spectroscopy showed the band gap energy of 2.61 eV for undoped WO₃ and 2.02 eV for I-P co-doped WO₃ nanocomposites. The surface area of I-P co-doped WO₃ (416.18 m²/g) was higher than the undoped WO₃ (352.49 m²/g). The XPS demonstrated interstitial and substitution of oxygen (O^2-) vacancies in WO₃ by I^- and P³⁺ and formed I-P-WO(_3-x). The I-P co-doped WO₃ exhibited higher catalytic activities (93.4% TOC, 95.1% COD) than the undoped (54.9% TOC, 79.2% COD) due to the synergistic effects between the two dopants. The experimental data better fitted to pseudo-second order than first order and pseudo-first order model. This study demonstrated the enhanced photocatalytic performance of I-P co-doped WO₃ nanocomposites under sunlight.