5. La protección de datos de carácter personal
5.3. Los derechos de acceso, rectificación y cancelación de los
In this experiment, the liquor prepared from the earlier dissolution process is subjected to controlled hydrolysis using water and the hydrate is filtered and dried at
Page | 79 110°C. Rutile is produced without using structure determining agents. Anatase is produced using phosphoric acid, tri sodium citrate and citric acid as the structure determining agents. Hence, there are 3 procedure stated below
5.3.1 Materials
In this experiment, the materials used are dissolved liquor, water, 10% hydrochloric acid, 0.1M phosphoric acid and citric acid.
5.3.2 Equipments
Apparatus used in this experiment are 5 litre round bottom flask, reflux condenser, thermometer, heating mantle, dropping funnel, glass fiber filter paper, mechanical agitator with teflon coated stirring rod, 4 necked lid and power supply
5.3.3 Procedure (Rutile formation without SDA)
Firstly, the cold liquor stored in duran bottle at 4°C, prepared from dissolution of ilmenite is subjected to water bath at 80°C till all the FeCl2.4H2O crystals are
dissolved. In this experiment, the 5lts round bottom flask with 4 necked lid with a reflux condenser, thermometer and a mechanical agitator with teflon coated stirring rod is used on a heating mantle. Drop ratio of liquor to water used by volume is 80:20 i.e. 80 parts of liquor and 20 parts of water (for e.g. 20ml of water is added for 80ml of filtered liquor). So 20 parts of water is now added in a RBF on a heating mantle. The seed is prepared in RBF flask. The reaction mixture is brought to boiling temperature
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for about 30 minutes. It is important to keep the reaction mixture boiling and stirring throughout the process. Extra care has to be taken while adding bulk liquor as it should drop right into the solution and not onto the sides of the reaction vessel, which might result in an uncontrolled hydrolysis and cracks on the sides of the
Page | 80 reaction vessel. After the addition of the entire liquor, the reaction mixture is boiled for 3hrs under reflux. The resultant liquor is filtered using a glass fiber filter paper and then thoroughly washed with 10% HCl (if not the product would possess yellow color which represent the presence of iron content). The hydrate is then dried in an oven at about 100°C. The resultant hydrate is then ground and subjected to X-Ray powder diffraction (XRD) to investigate the structural properties of product obtained before calcination. The filtered liquor washed with 10 % HCl is subjected to evaporation and pyrolysis for HCl recovery, which is again used in dissolution process. Also, Fe2O3 is obtained as a byproduct, extracted from FeCl2 crystals from
filtered liquor.
Seeding or Seed preparation
About 100ml of water is added to the flask and heated to 96°C. About 8ml(2% of bulk liquor(400ml) obtained from digestion) of filtered liquor is added through a pipette (preheated) in a drop-wise manner for 30—40 seconds with continuous stirring. The reaction mixture is aged for 5 minutes at 96°C. This mixture is called the ‘Seed’.
5.3.4 Procedure (Anatase formation using SDA)
For anatase phase TiO2, the SDA used are phosphoric acid, tri-sodium citrate and
citric acid. The apparatus used in this case is similar to the one used for rutile production. The procedure remains the same but this time the hydrolysis is initiated in the presence of phosphoric acid, sodium citrate or citric acid. The amount of SDA to be used also plays a vital role.
5.3.4.1 Phosphoric acid
The experimental procedure for producing anatase using phosphoric acid is same as the procedure followed for rutile production (5.2.3.1) except one step. In this
Page | 81 procedure phosphate ion is introduced in the form of phosphoric acid. About ‘X’g (amount of phosphoric acid to be added depends on the volume of filtered liquor obtained from dissolution, which is shown in table 3) of phosphoric acid is mixed with 20 parts (for e.g. 20ml of water is added for 80ml of filtered liquor) of water and the mixture is heated to 96°C with continuous stirring. This step is followed by the addition of 2% seed to boiling water in RBF. In this procedure, the remaining bulk liquor is added much slower (40 minutes in dropping funnel) than the procedure followed in rutile production. The mixture is then boiled for 3hrs under reflux condenser, filtered, thoroughly washed with 10% HCl (if not the product would posses yellow color which represent the presence of iron content) and dried. The dry hydrate sample is subjected for XRD to identify its phase and crystallite size.
5.3.4.2 Citric acid and Tri-Sodium citrate
The procedure followed in this method is same the procedure followed for obtaining anatase using phosphoric acid except one step. In this procedure, citrate ion is introduced in the form of citric acid/tri-sodium citrate. About ‘X’g (amount of citric acid/ tri-sodium citrate to be added depends on the volume of filtered liquor obtained from dissolution which is shown in table 3) of citric acid/tri-sodium citrate is mixed with 20 parts (for e.g. 20ml of water is added for 80ml of filtered liquor) of water and the mixture is heated to 96°C with continuous stirring. This step is followed by the addition of 2% seed to boiling water in RBF. In this procedure, the remaining bulk liquor is added much slower (40 minutes in dropping funnel) than the procedure followed in rutile production. The mixture is then boiled for 3hrs under reflux condenser, filtered, thoroughly washed with 10% HCl (if not the product would posses yellow color which represent the presence of iron content) and dried. The dry
Page | 82 hydrate sample is subjected for XRD to identify the phase and crystallite size of TiO2
obtained.
5.3.4.3 Amount of SDA (Phosphoric acid, Citric acid and Tri-Sodium citrate) to be used
Since SDA plays a vital role in building the product phase and its properties. It is important to add an appropriate amount of SDA in hydrolysis step to obtain the desired product. Excess or less usage of SDA may result in undesired reaction phase. SDA to be used is directly proportional to the volume of liquor obtained by dissolution process. In this project, SDA such as phosphoric acid, citric acid and tri- sodium citrate are used to obtain anatase phase of TiO2. The pH of the SDA also plays
a vital role in obtaining a product. SDA with high concentration reduces the hydrolysis rate thus resulting in high TiO2 loss in the solution. Hence SDA with
appropriate pH value which favors hydrolysis is chosen.