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

Abstract

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 (O2−) 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.