Synthesis of pure (control) SnO 2 Nps

Nps containing pure SnO2 were chemically synthesized by the sol-gel technique due to the following:

Firstly, 3.8827 mL of tin tetrachloride SnCl4 (AR grade) was mixed with 50.00 mL of absolute alcohol (ethanol) and 50.00 mL of ultra-pure water (Milli-Q-purified) in a round bottom flask and used as a precursor for synthesizing undoped (control) SnO2

Nps. To prepare 5.0000 g of SnO2 from SnCl4, molar mass of SnO2=150.71 g/mol and SnCl4 = 260.51 g/mol should be known. 5 g of SnO2 𝑥150.71𝑆𝑛𝑂2𝑔^𝑚𝑜𝑙 𝑥260.51𝑆𝑛𝐶𝑙4𝑔

𝑚𝑜𝑙 =

8.6428 𝑔 of SnCl4

The density of SnCl4=2.226 g/mL.

Density=mass/volume, then the volume=mass/density The volume of SnCl4=8.6428 g/ 2.226g/mL=3.8827mL.

∴ 3.8827 mL of SnCl4 will give 5.00 g of SnO2.

3.8827 mL of SnCl4 was dissolved in 50.00 mL ethanol in a 250 mL beaker as it explained with continuous and slowly stirring. On the top of the mixture added 50.00 mL of Milli-Q-purified. The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2 Photocatalyst preparation 89 3.2.2 Synthesis of doped SnO2 Nps

Different SnO2 Nps containing different ions such as (I, Nd, La, Ce, Sb and Gd) have been synthesized with different percentages such as (0.01, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0 and 1.1wt. %) using sol-gel process.

3.2.2.1 Synthesis of SnO2/I Nps

I was used to dope with SnO2 for synthesizing different SnO2/I weight percentages and the percentage of I on SnO2 was in concentration of (0.01, 0.1, 0.2, 0.3, 0.4, 1.0, and 1.1 wt. %).

For the synthesis of 1.1 wt. % of SnO2/I Nps, 0.0550 g of I and 4.9450 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9450 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8399 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0550 g of I was added with continuous and slowly stirring with the addition of 50 00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 1.0 wt. % of SnO2/I Nps, 0.0500 g of I and 4.9500 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9500 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8438 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0500 g of I was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.4 wt. % SnO2/I Nps, 0.0200 g of I and 4.9800 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9800 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8671 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0200 g of I was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.3 wt. % of SnO2/I Nps, 0.0150 g of I and 4.9850 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9850 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8709 mL of SnCl4 was dissolved in a 250 mL beaker contained 50 00 mL ethanol and 0.0150 g of I was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.2 wt. % SnO2/I Nps, 0.0100 g of I and 4.9900 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9900 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of I was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.1 wt. % SnO2/I Nps, 0.0050 g of I and 4.9950 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9950 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8788 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0050 g of I was added with continuous and slowly stirring with the addition of 50 00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.01 wt. % SnO2/I Nps, 0.0005 g of I and 4.9995 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9995 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8823 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0005 g of I was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2 Photocatalyst preparation 91 3.2.2.2 Synthesis of SnO2/Nd Nps

Nd was used to dope with SnO2 for synthesizing different SnO2/Nd weight percentages and the percentage of Nd on SnO2 was in concentration of (0.2, 0.6 wt. %).

For the synthesis of 0.2 wt. % SnO2/Nd Nps, 0.0100 g of Nd and 4.9900 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9900 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of Nd was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.6 wt. % SnO2/Nd Nps, 0.0300 g of Nd and 4.9700 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9700 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8594 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0300 g of Nd was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2.2.3 Synthesis of SnO2/La Nps

La was used to dope with SnO2 for synthesizing different SnO2/La weight percentages and the percentage of La on SnO2 was in concentration of (0.1, 0.2, 0.4 and 0.6 wt. %).

For the synthesis of 0.1 wt. % SnO2/La Nps, 0.0050 g of La and 4.9950 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9950 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8788 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0050 g of La was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.2 wt. % SnO2/La Nps, 0.0100 g of La and 4.9900 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9900 g of SnO2 from SnCl4, the molar

mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of La was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.4 wt. % SnO2/La Nps, 0.0200 g of La and 4.9800g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9800 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8671 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0200 g of La was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.6 wt. % SnO2/La Nps, 0.0300 g of La and 4.9700 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9700 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8594 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0300 g of La was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2.2.4 Synthesis of SnO2/Ce Nps

Ce was used to dope with SnO2 for synthesizing different SnO2/Ce weight percentages and the percentage of Ce on SnO2 was in concentration of (0.1, 0.2, 0.4 and 0.6 wt. %).

For the synthesis of 0.1 wt. % SnO2/Ce Nps, 0.0050 g of Ce and 4.9950 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9950 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8788 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0050 g of Ce was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2 Photocatalyst preparation 93 For the synthesis of 0.2 wt. % SnO2/Ce Nps, 0.01 g of Ce and 4.9900 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9900 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of Ce was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.4 wt. % SnO2/Ce Nps, 0.0200 g of Ce and 4.9800 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9800 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8671 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0200 g of Ce was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.6 wt. % SnO2/Ce Nps, 0.0300 g of Ce and 4.9700 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9700 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8594 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0300 g of Ce was added by continuous and slowly stirring with the addition of 50 mL of Milli-Q-purified. The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2.2.5 Synthesis of SnO2/Sb Nps

Sb was used to dope with SnO2 for synthesizing different SnO2/Sb weight percentages and the percentage of Sb on SnO2 was in concentration of (0.2, 0.4, 0.6 and 0.8 wt. %).

For the synthesis of 0.2 wt. % SnO2/Sb Nps, 0.0100 g of Sb and 4.9900 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9900 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of Sb was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.4 wt. % SnO2/Sb Nps, 0.0200 g of Sb and 4.9800 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9800 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8671 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol 0.0200 g of Sb was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.6 wt. % SnO2/Sb Nps, 0.0300 g of Sb and 4.9700 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9700 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8593 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0300 g of Sb was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.8 wt. % SnO2/Sb Nps, 0.0400 g of Sb and 4.9600 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9600 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8516 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0400 g of Sb was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

3.2.2.6 Synthesis of SnO2/Gd Nps

Gd was used to dope with SnO2 for synthesizing different SnO2/Gd weight percentages and the percentage of Gd on SnO2 was in concentration of (0.2, 0.4, and 0.6 wt. %).

3.2 Photocatalyst preparation 95

Table 13: Comparison % of dopants and volume of SnO2 values Sl. No. % of ions mass description was given before in section 3.2.1. Therefore, 3.8749 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0100 g of Gd was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.4 wt. % SnO2/Gd Nps, 0.0200 g of Gd and 4.9800 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9800 g of SnO2 from SnCl4, the molar mass description was given before in section 3.2.1. Therefore, 3.8671 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0200 g of Gd was added with continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

For the synthesis of 0.6 wt. % SnO2/Gd Nps, 0.0300 g of Gd and 4.9700 g of SnO2 were combined to give a total of 5.0000 g. To prepare 4.9700 g of SnO2 from SnCl4, the molar

mass description was given before in section 3.2.1. Therefore, 3.8593 mL of SnCl4 was dissolved in a 250 mL beaker contained 50.00 mL ethanol and 0.0300 g of Gd was added by continuous and slowly stirring with the addition of 50.00 mL of Milli-Q-purified.

The mixture was subjected to vigorous stirring for 3 h at room temperature, until a colourless solution was obtained.

Table 13 compares the different undoped and doped SnO2 Nps, these catalysts have been used in different experiments.

3.3

Sol-gel preparation 3.3.1 Sol-gel method

SnO2 synthesized and doped with different ions by sol-gel process at room temperature, Nps been prepared are suitable for large scale production. Applying low temperature procedure is always useful because of its less power consumption and better practical application. The synthesis process is simple and relatively inexpensive, which is based on the hydrolysis and condensation of metal ions to form metal oxide [372], providing a control on the size and the shape of Nps [373].

The sol-gel method offers several advantages such as high purity, better homogeneity, precise control over the stoichiometry, and capability to control the powder size and surface of metal oxides at lower temperatures [126, 160]. The basic benefit of the sol- gel method is the creation of materials at room temperature.

A liquid solution of organometallic precursors undergoes hydrolysis and condensation reactions, leading to the formation of a new phase

The alkoxy groups are substituted by hydroxide groups with the evolution of an inorganic network (sol).

3.4 Powder preparation 97 The particles condensed in a new (gel) phase in which a solid macromolecule is immersed in a solvent. Drying the gel at a low temperature between 25 to 80 ºC will serve to remove the liquid phase and make it possible to obtain porous solid matrices.

Two hydrolysed molecules liberate water (gel), upon linking together, which occurs through the destruction of the gel with the subsequent formation of nanoparticulate materials [259, 374-376]. While the reaction continues, the number of Sn-O-Sn bonds increases by the polymerization, which releases a macroscopic gel.

3.4

Powder preparation

When the colourless solution produced, the mixture was then condensed in a round bottom flask; the temperature was adjusted between 70-80 °C, and kept stable during the process. A white turbid colloidal solution of tin alkoxide appeared after heating the mixture under vacuum conditions [372]. The condensation process is done by refluxing the turbid solution at 70-80 °C for 1 h. After refluxing, the resultant solution was gelled for slowly stirring on a magnetic stirrer ( Make PMC 502 series) at 200 RPM and while stirring into this mixture, (25%) of an aqueous ammonia solution was prepared into 0.1M solution was added in a drop wise manner (with a rate of 10 drops/min). On addition of roughly 50 drops of 0.1 M ammonia the sol-gel was formed within the 5 min. The solution was stirred continuously until a pH value of 8 was reached and the resulting gel poured and left to dry into a container for 48 h until it become totally gelled.

Filtration and successive washing with Ultra-pure water was repeated several times to remove both ammonia and chloride ions until all chloride ions had been removed (by examining the filtrate solution using aqueous silver nitrate solution) The powder was then dried on a hot plate or in an oven at 80 °C and later transferred into an amber container and kept in the desiccator for future use. Prior to the analysis, the powder been grinded sonicated or diluted to obtain uniform particle size.

3.5

Reactors

The semiconductor catalyst is dispersed in powder form in the reaction solution containing the model compound. The apparatus consists of a mixing device, reactor vessel, and protected UV lamp, that can also be purged with air and oxygen. The reactor can be illuminated internally, where it is inserted into a quartz jacket or externally from the top, or it directly can be used by sunlight.

3.5.1 UV photocatalytic reactor

Figure 5 shows the UV photo reactor, which used in this study, where the inner insulator tube jacket is made of quartz, while the outer layer is made of glass tube. The arrangement in this photoreactor has two air flow distribution tubes, where it mixes the bubbles into the pollutant. The photoreactor was a cylindrical Pyrex-glass container with a 250 mL capacity, 50 mm internal diameter and 300 mm height. An 8 W medium pressure mercury lamp (Sankyo Denki, Osaka, Japan) with an intensity of about 80 W/m², as a 352 nm UV light source was used, situated axially at the center and the reaction temperature was kept at 25 °C to cool the photoreactor by means of water flowing. The air pump with a continuous speed was also combined to the air flow meter that was connected to the reactor outer tube to produce air (oxygen).

3.5 Reactors 99

Figure 6: Diagram arrangement of the photoreactor system

3.5.2 Visible light photocatalytic reactor

A second photoreactor contains a Pyrex glass reactor with a cooling water jacket in 250 mL capacity 100 mm internal diameter and 200 mm height. A 300 W xenon lamp simulated visible light source (PLS-SXE300C, Beijing Perfect light Co., Ltd, China), and was placed 71 mm above the surface of the contaminant during the photodegradation studies. The light source in this system is parallel light and can be focused in one direction on the sample, so the photocatalytic effect can be narrowed.

The system delivers maximum current of 20 A, and total optical power of 50 W.

Figure 7: Diagram arrangement of the visible reactor system

3.5.3 Solar light photocatalytic reactor

3.5.3 Solar light photocatalytic reactor

In document Synthesis and comparison of the photocatalytic activities of antimony, iodide, and rare earth metals on SnO2 for the photodegradation of phenol and its intermediates under UV, solar and visible light irradiations (sivua 88-0)