1. Introduction

Inorganic elements are chemically characterized by high stability and resilience, even under harsh conditions, which makes it suitable for many applications involving diverse and frequently changing chemical environments such Titanium Ti and Tungsten (W) [1-2]. However, a drawback is their ineffectiveness at normal temperatures, which limits their use in many applications, particularly in the energy and pollution removal sectors. The most commonly used method for activating these elements was to convert them into oxide form, where they are in a more chemically active form, such as TiO₂ and WO₃ [3]. According to details mentioned previously, many reactions or applications have become possible to accrue with high efficiency.

One method used to enhance the effectiveness of inorganic oxides, which still suffer from deficiencies in their activity, involves preparing inorganic complexes from their oxides. Some of these complexes are prepared by combining both oxides from their usual sources. [4]. Photocatalytic technologies are purifying on a huge scale for polluted water and air. The most common inorganic catalytic material for photoreaction is represented by titanium dioxide (TiO₂), which is effective for pollutant degradation due to two categories of (i) high photoexcitation activity: (i) chemical stabilization mechanisms and (ii) chemical stabilization mechanisms. The activities of TiO₂ were limited by the value of the band gap and the short time for forming (h+/e-) at the excitation state, which caused recombination for the two parts generated by the electron-hole in a very fast reaction. [5]. Many strategies were proposed and applied to solve or at least reduce the influence of the two limiting factors. Maybe creating a synergistic partnership with another semiconductor with a lower transfer rate or incentive, which is commonly referred to as a heterojunction [6]. Tungsten oxide (WO₃) is a semiconductor ideal for optoelectronics applications, with good conductivity, high value for e⁻/h⁺ mobility, and an oxygen-deficient n-type with an electronic bandgap of ~2.6–3.0 eV [7]. The hybrid-binary inorganic composite between short-wave UV light-absorbing TiO₂ and lower-energy-level near-visible-spectrum WO₃ creates new activity of the binary inorganic semiconductor. Photo-generated hole carriers left in the valence band under the presence of the corresponding TiO₂ levels will also have a strong reduction ability. The degree of holes and electrons. [8] In this work, a binary hybrid nanocomposite of inorganic oxides possessing semiconductor properties was prepared using WO₃ and precipitation TiO₂ after the addition of the substrate TiOSO₄ and precipitating agent. After preparing hybrid binary inorganic/semiconductor nanocomposites, the applications were done by removing two types of dyes, methyl orange and methylene blue, by adsorption and photodegradation reactions.

Experimental:

1- Chemicals

Titanyl sulfate (TiOSO₄), tungsten trioxide (WO₃), methyl orange (MO), and methylene blue (MB) were supplied by Sigma Chemical Company, with no further purifications. The precipitation reagent hydrogen peroxide (30% H₂O₂) was supplied from Barcelona, Scharlab, Spain. The scanning was analyzed with the UV-Vis spectrophotometer (TU-1950, Puxi General Instrument Co. Ltd., Beijing, China) from 200 to 800 nm. The value of pH of the prepared solutions was measured by LCD Display Tp-pH220 Potable pH Meter (Chongqing TOP Oil Purifier Co., Ltd., China) at 7.3 ±0.2 and was adjusted with (0.5 M) NaOH and (0.5 M) HCl. The concentration changes of the MO and MB solutions were represented by plotting the measured absorbance values into the standard curve equation.

2- Preparation of MO standard solution

1g of dye (MO) or (MB) were dissolved in less quantities of deionized water, stirred for 15 min at 350 rpm, and transferred with complete volume to a 1000 mL volumetric flask which represent (1000 ppm) of MO and MB standard solution respectively. MO and MB solutions was obtained by diluting the standard solution with deionized water. As shown in Fig.1 the Uv-visible spectrum for Prepared MO and MB solutions were measured its absorbance at wavelength 470 nm and 680 nm respectively by ultraviolet spectrophotometer.

Figure 1: Absorbance spectrum of (a) MO from wavelength (200-575 nm) and , (b) MB from (200-750 nm).

3- Synthesis of binary composites TiO2:WO3

The process includes preparing two solutions: the first, A, when (0.5) g of WO₃ was dispersed in 50 mL of distilled water with stirring by a magnetic stirrer (250 rpm) for 30 minutes. The second solution was B, which included the equivalent weight of TiOSO₄ to produce (1:1) {TiO₂:WO₃} dissolved in 50 mL of distilled water with heating to 40 degrees and continued stirring until forming a colorless solution. The two solutions, A and B, were mixed before 10 mL of 20% H₂O₂ was added slowly with stirring for 1 h. The mixture was still overnight before being filtered, and the precipitation materials were washed with distilled water. The yellow precipitation was dried at 100 degrees for 2 h before calcination at 400 degrees for 3 h.

4- Characterization

The x-ray diffraction XRD, measurements were carried out by (Philips APD 15) with CuKα radiation for 0.15405 nm, and the value of 2 thetas 10˚-80˚, with a scan rate of 5ᵒ/min and the resolution 0.02. Raman spectroscopy were measured by Sentara infinity 1 Broker at 530 nm, laser light, intensity 2m W for 5 lops per 2s and 3-5 cm of resolution. Fig. 2 shows XRD patterns of the WO₃ with the orthorhombic and monoclinic crystalline phases, which have distinguishable Bragg reflections (JCDPS. 20-1324) and (JCPDS. 01-072-1465). The diffraction peaks (2θ = 32°, 38°, 53°, and 64°) are assigned to the reflections associated with the tungsten oxide (WO₃) phase and Miller index (111), (211), (222), and (133) with crystallite sizes that were evaluated using the Scherrer formula [9]. XRD patterns for prepared TiO₂ were reported; high-intensity peaks demonstrate the sample mixture of anatase and rutile crystallinity, with a tetragonal structure. The Anatase phase included (2ϴ = 32, 35, 38, 47, 48, 57, 62, 64, 68, 69) with Miller index (101), (101), (200), (004), (211), (200), (211), (204), (216), and (220), while the Rutile phase was (2ϴ = 35, 56, and 57) and the Miller index was (101), (105), and (211) [10-11].

The XRD patterns for binary composites prepared by chemical deposition for TiO₂ from TiO(SO₄) with WO₃ and then thermal treatment at 400°C include three new parts: the first was the anatase phase at (2ϴ = 25°, 38°, 47°, and 63°), which is related to (110), (101), (111), and (211). The second phase was rutile at (2ϴ = 53°, 55°, and 77°), which related to indices (101), (111), and (211). However, [12-13] the third was for WO₃ in binary, which witnessed reduced intensities of peaks as compared with TiO₂ and merged or overlapped peaks at 37°, 54°, and 64°. The diffraction peaks associated with WO₃, TiO₂, and TiO₂:WO₃ were calculated as crystallite sizes by the Scherrer formula and shown to be 12 nm, 19 nm, and 29 nm, respectively.

Figure 2: XRD- patterns of WO3, prepared TiO2, and prepared TiO2:WO3 for (2ϴ=10˚-80˚).

Raman spectra show strong peaks at 163–650 cm⁻¹, indicating the Ti–oxygen bonding, with vibration modes at 163 (Eg), 402 (B1g), 525 (A1g+B1g), and 650 (Eg, Bg, and Ag) due to symmetric stretching, symmetric, and antisymmetric bending vibration of TiO₂, respectively [14]. Pristine WO₃ showed the monoclinic phase, which has characteristic peaks at 426 and 860 cm⁻¹, and that represents the characterized peaks for the W=O bond. [15]. The Raman spectrum after doping WO₃ with TiO₂ showed the same detection for TiO₂ and WO₃ in the TiO₂/WO₃, with variance in the positions of peaks shifted for red shifted by approximately 3-7 cm⁻¹. In addition to 726 and 820 cm⁻¹ for rutile TiO₂ and WO₃, respectively [16].

Figure 3: Raman spectrum of WO3, prepared TiO2, and prepared TiO2:WO3.

Adsorption and Photo-Degradation

The effectiveness of the binary composite was studied through a decolorization reaction, which requires two stages as shown in fig. 3: first, studying the adsorption activity, which precedes the second reaction; and second, studying the activity in the presence of ultraviolet radiation. The process was done with two dyes (20 ppm / 100 mL), MO and MB, and the same weight (60 mg) of catalysts WO₃, TiO₂, and TiO₂:WO₃. . Figure xx includes the scheme of the process, which contains a UV lamp (15 W) emitting radiation at 254 nm, which is enclosed in a wooden box.

Figure 4: skim for all experimental parts for dark and photo reaction.

Figure 4 shows the two decolorization processes for MO, at adsorption, where the equilibrium time for decolorization was 45 min for the three due components TiO2, WO3, and TiO2:WO3 which showed decolorization rates ranging (WO3<TiO2<TiO2:WO3) respectively. The second process, photo reaction was witness the arrangement (TiO2<WO3<TiO2:WO3)

Figure 5: Adsorption and photo degradation of 20 ppm MO by 60 mg/ 100 m L TiO2 , WO3, and TiO2:WO3, at wavelength 470 nm and 298.15K.

The behavior of three materials was shown change in activity with MB., according to the results in figure 5, the adsorption was (TiO2:WO3<WO3<TiO2), while photo reactions was (WO3<TiO2<TiO2:WO3).

Figure 6: Adsorption and photo degradation of 30 ppm MB by 60 mg/ 100 m L TiO2 , WO3, and TiO2:WO3, at wavelength 680 nm and 298.15K.

The activity of binary composite TiO2:WO3 towards removed MO and MB were reported in figure 6 with two process adsorption and photo reaction. The removal activity was more active with MO at the two process, in additions to variance in value for the two dyes.

Figure 7: The skim of (a) adsorption and photo degradation for 30 ppm MO and MB by 60 mg/100 m L of TiO2:WO3, with absorbance spectrum (a) MO, and (b) MB at wavelength 470 nm and 680 nm respectively.

According to figure 7a, which mentions the values of percent removal %R [17] that is calculated by equation {%R= (At/A0)*100} in every process and total value. The results showed a greater adsorption advantage for the binary complex TiO₂:WO₃ in removing MO dyes compared to the individual components TiO₂ and WO₃. However, the photocatalytic reaction also showed an advantage for the binary complex, with the final removal yield reaching more than 80% of %R. The accumulation result in fig. 7b for MB showed less activity compared to the effect of pristine TiO₂, WO₃, and TiO₂:WO₃, which reached about 40% with MB, and that represents half the effectiveness of the same substance for removing MO.

Figure 8: The skim of %R (Adsorption+ Photo reaction) from 20 ppm of (a) MO, and (b) MB by (60 mg/ 100 m L) TiO2, WO3, and TiO2:WO3 at 298.15 K.

Mechanism of Reaction

Fig. 8 reported the proposal mechanism of photo-degradation by TiO₂:WO₃, which started with (-0.3 eV) for energy potential of the CB of anatase TiO₂ when proved for the synthesized process by XRD and Raman spectrum. The energy of UV irradiation was approximately 3.4 eV, which is a higher level than the band gap of WO₃ and TiO₂, with values of 2.7 eV and 3.2 eV, respectively. The level of UV energy is able to generate photons in both WO₃ and TiO₂, therefore it is a critical parameter to make the best separation between the excited electron and the positive hole with enough time to make the electron's delay from the hole for a suitable period of time to generate more active species [18].

The value as reported in the huge literature [19] is higher negative (0.74 eV) as compared with the CB energy for WO₃. The energy difference between the two inorganic oxides logically promotes the spontaneous transfer of electrons from TiO₂ towards WO₃ through CB [20]. Increasing the efficiency of the binary inorganic complex is another important factor that favors this behavior, represented by the continuous exchange of H+ between TiO₂ and WO₃ of each valence band in the two components. The factor that enhances electron transfer in the direction of the oxidation reaction is the presence of oxygen sites that are ready to receive electrons and prevent them from returning to the hole, which acts as an ideal capture for electrons [21]. The last inorganic behavior makes a real reaction to modifying and improving the efficiency for the surface of TiO₂ with WO₃.The presence of water molecules around the active oxidizing groups will have the effect of generating free hydroxyl radicals, which in turn act as active sites for the oxidation of dyes in general and MO in particular. The other inorganic parameter [22] reported in figure 7 was the higher value for VB of WO₃ as compared with the level of VB for TiO₂, and that makes h⁺ of WO₃ a good recipient of H₂O molecules for easier oxidation and the formation of new free radicals (OH).

Figure 9: The skim for proposal mechanism for binary composite TiO2:WO3

As demonstrated by the hybrid synergistic mechanism of the inorganic oxide, the two oxidants were unable to perform the same action to remove MB, which showed less activity compared to MO. The last behavior may be related to higher abilities for MO than MB, as shown in the adsorption results, which enhance the second part of removing dye [23]. The other cause was represented by high concentrations at 20 ppm and more, which converted the reaction likely in favor of removing MO more than MB due to the higher intensity of color, which prevented penetration of UV light [24]. Thus, according to the experimental section, the binary inorganic oxide hyper was more active with MO than MB.

Conclusion

The loading of titanium dioxide onto tungsten oxide was achieved by precipitating titanium ox-sulfate using hydrogen peroxide. This successfully established a bond and synergy between the two oxides, which was observed in both Raman spectroscopy and X-ray diffraction. The synergistic behavior was further demonstrated by the ability of the two non-organic complexes to decolorize the two dyes, despite the difference in efficiency between the two types. The synergistic effect between the inorganic oxides of tungsten and titanium was evident after a hybrid complex of the two was prepared. The effect was evident when the inorganic complex was more effective for adsorption and photodegradation compared to the two oxides when used individually. However, this did not prevent the MB dye from showing resistance to color removal compared to MO according to the conditions of the prepared hyper binary inorganic oxide composite.