Highly efficient sorption of molybdenum from tungstate solution with modified D301 resin

The modified D301 resin is prepared by assembling TOA and D301 for efficient selective adsorption of MoS42− from tungstate solution.

The role of WO42− on surface passivation for Q235 carbon steel in tungstate solution

Purpose The purpose of this work is to reveal the mechanism of WO42− on surface passivation for Q235 carbon steel in tungstate solution. Design/methodology/approach In Na2WO4 solutions with the different concentrations of WO42−, the spontaneous passivation occurred on the surface of Q235 carbon steel when the concentration of WO42− was up to 0.13 mmol/L, which was attributed to the formations of the inner deposition film and the outer adsorption film on the Q235 surface under the action of WO42−. Findings The inner deposition film presented a two-layer microstructure: the inside layer was composed of Fe2O3 mainly, and the outside layer comprised Fe(OH)2•nH2O, Fe(OH)3•nH2O, FeWO4 and Fe2(WO4)3. Originality/value Both FeWO4 and Fe2(WO4)3 repaired the defects in the outside layer of the inner deposition film; however, the outer adsorption film played a more important role in the surface passivation than the inner deposition film did.

A Comparison Study between ZnO Nanorods and WO3/ZnO Nanorods in Bromocresol Green Dye Removal

This work studied the photocatalytic performance of ZnO nanorods and WO3/ZnO nanorods in bromocresol green (BCG). The ZnO nanorods were pre-synthesized via solution precipitation method. Subsequently, the nanorods were kept in sodium tungstate solution for the deposition of WO3. The present of WO3 was confirmed by XRD and EDX analysis. ZnO nanorods (64.34%) showed a higher photodegradation efficiency of BCG removal than WO3/ZnO nanorods (60.03%) under 75 minutes of UV irradiation. This could be attributed to the formation of WO3/ZnO shell-core nanostructure which limited the generation of holes and hydroxyl free radicals that needed for the photodegradation of BCG dyes.

FTIR-SPECTROSCOPIC INVESTIGATION OF SODIUM TUNGSTATE AND SODIUM MOLYBDATE SOLUTIONS IN WIDE RANGE OF рH

For citation:Matveichuk Yu.V. FTIR-spectroscopic investigation of sodium tungstate and sodium molybdate solutions in wide range of рH. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 1. P. 56-63. A FTIR spectroscopic study of aqueous solutions of sodium tungstate and molybdate (solution concentration was 0.1 mol/l) over a wide pH range (factor (level) of acidity Z, Z = C (H+)/C (WO42-) or Z = C (H+)/C(MoO42-)) was carried out. In solutions of sodium tungstate complex frequency band at 885-865 cm-1 correspoding to the stretching vibrations ν(W-O-W) was fixed. The frequency bands of 1720-1700 cm-1, 990, 985 and 1025 cm-1 corresponding to bending vibrations δ(W-OH) were fixed that indicates a significant change in composition of the solution as a result of hydrolytic and polycondensation processes. The sodium molybdate solution has not bands corresponding to the stretching vibrations v(Mo-O-Mo). Only the characteristic bands of the deformation vibrations δ(Mo-OH) were recorded. The low intensity complex band in the area of 885-865 cm-1 corresponding to the stretching vibrations ν(W-O-W) even for freshly prepared 0.1 mol/l sodium tungstate solution was appeared as well as the band at 1720-1700 cm-1 attributed to deformation vibrations δ(W-OH) that indicates a fast change in the solution composition. For solutions of sodium molybdate bands of stretching vibrations v(Mo-O-Mo) are fixed at a pH less than 6 after standing for several days. With Hydra/Medusa program diagrams of distribution of molybdate and tungsten particle depending on the pH were calculated. In relatively dilute solutions, the diagrams received with Hydra/Medusa program showed the only protonated (monomeric) form of molybdate ions, where as in the sodium tungstate solution until pH of 9 W6O216- and HW6O215- particles exist that agrees with the results of IR spectroscopy. The results of IR spectroscopy and modeling with Hydra/Medusa program will be used to support the pH operating range for molybdate and tungstate-selective electrodes, since they are an important feature of any analytical ion-selective electrodes. For tungstate-selective electrode it is necessary to maintain the pH less than 9, for molybdate-selective electrode - less than 8 (with dilute ammonia). Considering the changes in the composition of sodium molybdate and tungstate solutions, for the design of molybdate and tungstate-selective electrodes the freshly prepared solutions have to be only used, rather than stored for more than two days.