I-P Co-Doped WO3 for Photocatalytic Degradation of Dyeing Wastewater

Nearly 20% of water pollution is caused by the leather and textile industries. Textile wastewater contains a lot of organic pollutants, including dyes that are widely used in industry. At the same time, printing and dyeing wastewater has also caused water problems and health problems.

Semiconductor photocatalytic treatment ensures the environmentally friendly removal of toxic pollutants in textile wastewater with harmless products. Many semiconductor photocatalytic materials, such as ZnO, TiO2, SnO2, MoS2, V2O5, WO2, etc., have been used. Tungsten trioxide (WO3) has small band gap, electrochromic, photochromic and gaschromic properties, and is a promising photocatalytic material. However, it has a lower light energy conversion rate and a lower conduction band. Therefore, the use of Begonia water leaf extract for green synthesis of WO3 nanoparticles was explored. Phosphorus (P) and iodine (I) are co-doped to prepare I-P co-doped WO3 for photocatalytic degradation of dyeing wastewater. The preparation process of I-P co-doped WO3 composite is as below:

50g of powdered leaves of Spondias mombin was poured into 500cm3 methanol in a reflux flask to reflux for 2h. The extract was filtered with a muslin cloth and then evaporated on a rotary evaporator. The semi-dry extract is weighed, placed in a sterile bottle and stored in the refrigerator until further analysis. Iodine and phosphorus co-doped WO3 nanocomposite material (I-P-WO3) is synthesized as follows; first, weigh 20cm3 Spondias mombin extract in a 250cm3 Erlenmeyer flask and mix with 100cm3 0.06M ammonium paratungstate. Subsequently, 2% ammonium iodide and ammonium phosphate were added, and then stirred on a magnetic stirrer at 150 rpm for 1 hour to form a homogeneous solution. Leave the obtained precipitate for 24 hours, pour out the supernatant, and wash the precipitate with distilled water several times to remove excess plant extracts and other impurities. The resulting precipitate was dried in an oven at 80°C for 6 hours and calcined in an oven at 550°C for 2 hours.

Finally, nanomaterials are characterized by HRSEM, HRTEM, BET, UV-Visible, EDS, XRD and XPS. Taking total organic carbon (TOC) and chemical oxygen demand (COD) as indicators, the photooxidation effect of the synthesized WO3 nanomaterials on printing and dyeing wastewater was tested and evaluated.

In summary, I-P co-doped WO3 for photocatalytic degradation of dyeing waster is prepared by co-doping with phosphorus (P) and iodine (I), the photocatalytic activity of WO3 has been greatly improved. Ultraviolet-visible diffuse reflectance spectroscopy shows that the band gap energy of undoped WO3 is 2.61 eV, and the band gap energy of I-P co-doped WO3 nanocomposite is 2.02 eV. The surface area of I-P co-doped WO3 (416.18m2/g) is higher than that of undoped WO3 (352.49m2/g). Compared with the single-doped and undoped WO3 samples, the I-P co-doped WO3 nanocomposite showed the highest photocatalytic activity for TOC and COD reduction, which were about 93.40% and 95.14%, respectively. It is found that materials with low band gap energy, higher BET surface area and more porous structure exhibit higher photocatalytic activity.

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