Description

Metal Content

Determining the metal content in iron ore samples is a crucial step for assessing their quality and suitability for industrial use. This process begins by dissolving iron ore samples in hydrochloric acid and nitric acid to break down the material. The solution is then evaporated to remove silica, followed by dilution to adjust its concentration. Afterward, filtration is used to separate any remaining insoluble particles, ensuring that impurities are thoroughly removed. This purification process guarantees that the sample is in optimal condition for further analysis, providing reliable and accurate results.

This method is suitable for a mass content of aluminum between 0.1–5.0% in natural iron ores, iron ore concentrates, and agglomerates, including sinter products.

 

Residue Treatment and Fusion

After filtration, we ignite the residue and remove the silica by evaporating it with a mixture of hydrofluoric and sulfuric acids. Once this step is complete, we carefully fuse the remaining residue with sodium carbonate. Following the fusion process, we allow the resulting melt to cool naturally. Once cooled, we dissolve the melt in the filtrate obtained earlier.

Atomic Absorption Analysis

We then aspirate the resulting solution into the flame of an atomic absorption spectrophotometer for analysis, using a nitrous oxide-acetylene flame to ensure proper atomization. Next, we calculate the results by referencing the aluminum standard solution to ensure measurement accuracy.

Determining Aluminum Content

Finally, we use these calculations to determine the precise aluminum content in the sample, thereby ensuring both the reliability and accuracy of the analysis. Consequently, this step confirms the integrity of the results and reinforces the precision of the overall measurement. Thus, we can be confident in the accuracy of the analysis, ensuring its reliability for further application.

Moreover, by cross-referencing the calculations with the standard solution, we further validate the outcome, which, in turn, ensures a high level of precision in the analysis. In addition, by carefully considering all factors involved, we can be confident in the results. Ultimately, this thorough process not only guarantees that the results are reliable but also assures their accuracy, ensuring the integrity of the entire analysis.

Equipment and Reagents

Equipment and Apparatus:

1. PERSEE Atomic Absorption Spectrophotometer A3F, equipped with nitrous oxide/acetylene gas supply & air/acetylene gas supply. PERSEE aluminum hollow cathode lamps.

2. Muffle Furnace, durable enough to maintain a temperature of 1100°C.

3. Platinum Crucible, compatible with the muffle furnace.

 

Reagents (Analytical Grade):

1. Sodium carbonate (Na₂CO₃), anhydrous

2. Hydrochloric acid, ρ 1.19g/ml

3. Nitric acid, ρ 1.4g/ml

4. Hydrochloric acid (1+9) solution, ρ 1.19g/ml (diluted 1+9)

5. Hydrofluoric acid, ρ 1.13g/ml, 40% mass fraction, or ρ 1.185g/ml, 48% mass fraction

6. Sulfuric acid, ρ 1.84g/ml, diluted 1+1

7. High purity iron (purity >99.9%) with an aluminum content of <0.002%

8. High purity aluminum (purity >99.9%)

 

Background Solution:

1. Dissolve 10g of high purity iron in 50 ml of hydrochloric acid and oxidize by adding nitric acid drop by drop (as little as possible).

2. Begin by gradually evaporating the solution, ensuring that the process is controlled. As evaporation continues, be sure to monitor the process closely. Once the solution begins to thicken, continue checking until a syrup-like consistency is achieved. This ensures that the desired concentration is reached before proceeding. Therefore, constant observation is essential to prevent over-evaporation and ensure optimal results. At this stage, make sure that most of the solvent has evaporated, leaving behind a sticky residue. As a result, the solution will become more concentrated, thus preparing it for the next step in the process.3. Add 20 ml of hydrochloric acid and dilute to 200 ml with water.

4. Begin by dissolving 17 g of sodium carbonate in water. Once dissolved, proceed by adding this solution to the iron solution obtained in the previous step, ensuring thorough mixing. In doing so, ensure that the two solutions are well combined for optimal results. This step is crucial to achieving uniformity in the mixture, preparing it for the next phase of analysis.

5. Transfer the solution to a 1000 ml volumetric flask and dilute to volume with water

 

Aluminum Standard Solution

1. Aluminum Standard Stock Solution (Al content 500 μg/ml):

Dissolve 0.5000 g of high purity aluminum in 25 ml of hydrochloric acid. First, allow the solution to cool. Afterward, transfer it carefully to a 1000 ml volumetric flask. This step ensures that the solution is properly prepared for the next stage of the process.. Add water to the mark and mix the solution well.

2. Aluminum Calibration Solutions (Al content: 0, 5.00, 12.5, 25.0, 50.0, 100, 125 μg/ml):

1. Transfer 2.0, 5.0, 10.0, 20.0, 40.0, and 50.0 ml portions of the aluminum standard stock solution (500 μg/ml) into 200 ml volumetric flasks.

2. Dilute each flask with water to about 100 ml.

3. Add 6 ml of hydrochloric acid and 60 ml of the background solution to each flask.

4. Prepare a blank aluminum calibration solution by transferring 60 ml of the background solution to a 200 ml flask and adding 6 ml of hydrochloric acid.

5. Dilute all solutions to 200 ml with water and mix thoroughly.

1. Dried Test Sample Preparation:

For eligible sample material, first, use a sample with a particle size of less than 100 μm. Furthermore, ensure that the sample has been prepared in accordance with ISO 3082, which guarantees consistency and uniformity in the analysis. This sample should have been prepared in accordance with ISO 3082 to ensure uniformity and consistency in the analysis. Take a representative portion of the sample from the material. Dry the test sample at 105 ±2°C.

2. Decomposition of the Test Portion:

– Take several increments, weigh approximately 1g of the dried test sample.

– Transfer the test portion to a 250 ml beaker. Moisten it with a few ml of water. Add 25 ml of hydrochloric acid, cover with a watch-glass, and heat gently. Increase the heat and digest just below boiling for a few minutes.

– Add 2 ml of nitric acid and digest for several minutes.

– Remove the watch-glass and keep the solution boiling for 30 minutes (105-110°C), evaporating most of the solution.

– Add 5 ml of hydrochloric acid to dissolve the residue. Put the watch-glass back on the beaker and keep warm for several minutes.

– Add 50 ml of water and heat the solution to boiling, washing the watch-glass and walls of the beaker.

– Next, filter the solution through medium-texture paper into a 250 ml beaker. Afterward, carefully remove all adhering particles using a rubber-tipped rod or moistened filter paper. In doing so, make sure that no residue remains on the surface. Next, wash the area three times with hydrochloric acid to remove any remaining impurities. Subsequently, rinse with hot water until the filter paper is completely free of yellow color. This ensures that all contaminants are thoroughly removed, leaving the surface clean and prepared for the next step.

– Transfer the paper and residue to a platinum crucible. Evaporate the filtrate to about 100 ml and retain it.

 

Treatment of the Residue

– Ignite the paper and residue in the platinum crucible at 500 to 800°C.

– Cool, moisten with a few drops of water. Add 3 to 4 drops of sulfuric acid and 10 ml of hydrofluoric acid.

– Evaporate slowly to expel silica.

– Remove excess sulfuric acid by heating it up and maintaining a temperature of about 700°C (the acid will evaporate in white smoke).

Next, add 1.0 g of sodium carbonate to the residue, ensuring the crucible is covered. Then, fuse the mixture at 1100°C for 15 minutes, either over a burner or in a muffle furnace, until a clear melt is obtained.

Preparation of the test solution

Dissolve the cooled melt residue in the retained filtrate. Then, remove and wash in the crucible and cover.

Note: If the solution is cloudy at this stage, indicating the presence of hydrolyzed titanium, it should be filtered prior to the next step.

Transfer the solution to a 200 ml flask, dilute with water, and mix. Inject this solution directly into the atomic absorption spectrophotometer as the testing solution.

Note: If the mass fraction of aluminum in the original sample is greater than 2.5%, then, transfer a 40 ml aliquot to a 200 ml volumetric flask. Add 50 ml of the background solution and 4 ml of hydrochloric acid. Dilute to volume with water and mix. Inject this solution instead as the testing solution.

Instrumental preparation:

1. Apply the Al hollow cathode lamp to the A3F atomic absorption spectrophotometer. Preheat for 30 minutes.

2. Adjust the lamp energy to 100%.

3. Set the wavelength to 396.2 nm, search for the peak, and confirm that the lamp and instrument are functioning correctly.

4. Ignite with air-acetylene for 10 minutes. Then, switch to nitrous oxide-acetylene.

5. Inject the aluminum standard solution of the highest aluminum content. Adjust gas flow and burner head height to obtain maximum absorbance.

6. Next, inject water and select [auto zero].

Equipment Condition
Instrument Working Parameters:

Equipment Condition & Instrument Working Parameters

Experiment Procedure:

Run standard aluminum solutions with aluminum content of 0, 5.00, 12.5, 25.0, 50.0, 100, and 125 μg/ml, then create a standard curve using the results.
Run samples prepared above and calculate the results using AAWIN software.

Calculation:

The mass fraction of aluminum, wAl, expressed as a percentage, is calculated to four decimal places using the formula below:

where:
ρAl is the mass concentration, in micrograms per ml, of aluminum in the final test solution; m is the mass, in grams, of sample contained in 200 ml of the final test solution

 

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