Iodine-Phosphorus Co-Doped Tungsten Trioxide Photocatalytic Nanocomposites Prepared Via APT

Dyeing industries use and discharge large volumes of water containing complex non-biodegradable recalcitrant organic and inorganic chemicals into the environment. The local dyeing wastewater have an offensive odour, highly coloured, low pH, and exposure to such wastewater can cause several diseases among which are cancer, skin irritation to mention but a few.

Tungsten trioxide (WO3) nanoparticles has emerged as a suitable candidate due to their smaller band gap, electrochromic, photochromic and gasochromic properties. Green synthesis of WO3 nanoparticles using ammonium paratungstate (APT) and Spondias mombin aqueous leaf extract was introduced. The synthesized WO3 nanoparticles was simultaneously doped and co-doped with phosphorus and iodine.

The synthesis process of  is as below:

All chemicals and reagent such as ammonium iodide, ammonium hydroxide, ammonium paratungstate, sodium hydroxide, ammonium hydroxide tetra oxophosphate (VI) acid, nitric acid used in this study are of analytical grade and were used without any further purification.

A known weight (50 g) of the powdered leaves of Spondias mombin were weighed into 500 cm3 of methanol in a reflux flask and refluxed for 2 h. The extract was filtered using muslin cloth and subsequently evaporated on a rotary evaporator. The semi-dry extract was weighed, placed in a sterile bottle and stored in a refrigerator until further analysis.

The iodine and phosphorus co-doped WO3 nanocomposites (I-P-WO3) was synthesized as follows; firstly, 20 cm3 of Spondias mombin extract was measured and mixing with 100 cm3 of 0.06 M ammonium paratungstate in a 250 cm3 conical flask. This was followed by addition of 2% ammonium iodide and ammonium phosphate and thereafter stirred on a magnetic stirrer at 150 rpm for 1 h to form a homogenous solution. The precipitate obtained was left to age for 24 h and the supernatants decanted and the precipitate was washed several times with distilled water to remove excess plant extract and other impurities. The resultant precipitate was oven-dried at 80 °C for 6 h and calcined in the furnace at 550 °C for 2 h.

In summary, iodine-phosphorus co-doped tungsten trioxide photocatalytic nanocomposites were successfully synthesized from mixture of ammonium paratungstate and spondias mombin plant extract by simple green method. The I-P co-doped WO3 nanocomposites exhibited the highest photocatalytic activity of about 93.40% and 95.14% for TOC and COD reduction respectively. This study provides new insights for the preparation of highly photoactive I-P co-doped WO3 nanomaterials with higher specific surface area, smaller band gap energy, good crystallinity and monoclinic crystal polymorph for the degradation of local dyeing wastewater.

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