Effect of pH in the Hydrothermal Preparation of Bi2WO6 Nanostructures

Abstract

In this study, Bi2WO6 was prepared by the hydrothermal method. The effects of reaction temperature (150/170/200 °C) and reaction time (6/12/24 h) were investigated. The role of strongly acidic pH (1 >) and the full range between 0.3 and 13.5 were studied first. Every sample was studied by XRD and SEM; furthermore, the Bi2WO6 samples prepared at different temperatures were examined in detail by EDX and TEM, as well as FT-IR, Raman and UV-vis spectroscopies. It was found that changing the temperature and time slightly influenced the crystallinity and morphology of the products. The most crystallized product formed at 200 °C, 24 h. The pure, sheet-like Bi2WO6, prepared at 200 °C, 24 h, and 0.3 pH, gradually transformed into a mixture of Bi2WO6 and Bi3.84W0.16O6.24 with increasing pH. The nanosheets turned into a morphology of mixed shapes in the acidic range (fibers, sheets, irregular forms), and became homogenous cube- and octahedral-like shapes in the alkaline range. Their band gaps were calculated and were found to vary between 2.66 and 2.59 eV as the temperature increased. The specific surface area measurements revealed that reducing the temperature favors the formation of a larger surface area (35.8/26/21.6 m2/g belonging to 150/170/200 °C, respectively).

Effect of processing parameters on the morphology of hydrothermally synthesized calcium borate powders

“…Without using specific equipment or external additives morphology of particles can be tailored. Finally, produced calcium borates can be used in several areas in industry such as coating for implants due to antibacterial effects 43 or for fibers to increase flame retardant, 3 lubricant component, 31 UV light source, light emission diodes, and luminescent phosphors 44 . Specifically sphere and clove‐like shape calcium borates can be utilized adsorbents for heavy metal ions 45 or in insecticide applications, 5 and also nano‐plate shape calcium borates can be utilized textured ceramic application 46,47 …”

“…synthesized priceite (Ca 2 (B 5 O 7 )(OH) 5 ·H 2 O), the initial solution of which consists of boric acid and calcium oxide, by using HS 11 . Calcium borate nanoslice was produced by utilizing borax (Na 2 B 4 O 7 ·10H 2 O) and calcium nitrate (Ca(NO 3 ) 2 ·4H 2 O) by using HS at 180°C for 4 h 31 . Literature survey shows that HS is one of the commonly used methods during the production of calcium borates; to the best of our knowledge, pH effect on the final calcium borate properties was not investigated 2 …”

“…4 Bi 2 WO 6 crystals were produced and obtained mixed shapes such as fibers and sheets in the acidic range, and homogeneous cube and octahedral-like crystals in the basic range. 30 Song 31 Literature survey shows that HS is one of the commonly used methods during the production of calcium borates; to the best of our knowledge, pH effect on the final calcium borate properties was not investigated. 2 The goal of this study was to produce calcium borate powders that have various morphologies depending on the pH value of starting solutions by HS.…”

Efficient photocatalytic removal of N‐nitrosamines from amine washing wastewater using bismuth tungstate

“…There is no significant weight loss observed in the Bi 2 WO 6 that was synthesized using HTS. [50] The TGA data of metal impregnated bismuth tungstate catalysts after calcination are shown in Figures S9. The results indicate that metal impregnated catalysts are thermally stable over the temperature range 0-800 C. The weight loss is minimal, indicating that the catalysts are from undesirable components from precursor salts.…”

Bioinspired hierarchical 3D flower-in-ridge hybrid structure for the photodegradation of persistent organic pollutants

“…† The synthesis of the oxygen-vacant blue Bi 2 WO 6−x was performed via a modified solvothermal route. 40 Typically, Na 2 WO 4 •2H 2 O (0.49 g, 1.5 mmol) and Bi(NO 3 ) 3 •5H 2 O (1.50 g, 3 mmol) were dissolved in HNO 3 (9 mL, 2 M) and deionized water (30 mL) in beakers labelled solutions A and B, respectively. Solution A was added dropwise to solution B, forming a yellow precipitate after stirring for 30 min at 700 rpm.…”