msce Journal of Materials Science and Chemical Engineering 2327-6045 2327-6053 Scientific Research Publishing 10.4236/msce.2025.133002 msce-141491 Articles Chemistry Materials Science Analysis of Bauxite by X-Ray Fluorescence: Mineralogical Study of the Boffa Deposits Mariama Camara 1 Cheick Abdoul Balde 1 Alpha Tata Balde 2 Souleymane Balde 1 Tamba Diré Camara 2 aDepartment of Chemistry, University Gamal Abdel Nasser of Conakry, Conakry, Guinea aGuinea Bauxite Company (CBG), Kamsar, Guinea 19 03 2025 13 03 18 24 5, February 2025 22, February 2025 22, March 2025 © Copyright 2014 by authors and Scientific Research Publishing Inc. 2014 This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ This study investigates the chemical and mineralogical composition of bauxite samples from five operating sites in Boffa, Guinea, aiming to assess their quality and suitability for alumina production using the Bayer process. The researchers employed X-ray fluorescence (XRF) to determine elemental composition after calcination and fusion with lithium borates. The results indicate that the Boffa bauxites are high in alumina (34.28% - 54.02% Al 2O 3) and low in silica (0.98% - 7.29% SiO 2), suggesting high quality and economic viability. X-Ray Fluorescence Boffa Bauxite Mineralogy B-Quant 1. Introduction

Guinea has the world’s largest reserves of bauxite, the ore used to produce aluminum, and its subsoil contains more than a third of these. These reserves are mainly located in the following regions: Lower Guinea (Boké, Kindia, Fria, Boffa), Middle Guinea, in the Fouta-Djalon massif (Tougué, Pita, Mali, Mamou, Dalaba) and Upper Guinea (Dinguiraye, Dabola, Siguiri). With a high alumina content, Guinean reserves are estimated at more than 40 billion tons, including 25 billion concentrated in the province of Boké [1] .

Study Area

The prefecture of Boffa, where the samples were taken, is an administrative subdivision of the province of Boké. It covers an area of 6003 km2 and is 150 km from Conakry. Boffa had 211,063 inhabitants in 2018, according to the National Institute of Statistics. Located along the Atlantic Ocean on the Conakry-Boké axis, it is crossed by the Fatala River. Eight (8) sub-prefectures make up it: Koba, Lisso, Kolia, Mankounta, Tougnifily, Doujrou, Tamita and Boffa Centre. It is bordered to the north by the prefectures of Boké and Télémélé, to the east by the prefecture of Fria, to the south by the prefecture of Dubréka and to the west by the Atlantic Ocean.

For several years, this locality rich in bauxite has experienced an unprecedented mining boom and is home to many mining companies, including: Alufer, China Power Investment, TBEA, Chalco Mining, Axis Minéral, and Eurasian.

Eleven (11) mining companies hold exploration and exploitation permits there. Four (4) companies have already set up in (5) five rural communes including: Bel Air Mining in Doupourou and Tougnifily, which began production in 2018; Chalco in Tamita. China State Power Corporation (SPIC), ex-CPI, in Doupourou and Koliah, and Eurasian on the ore transport corridor in Lisso and Tamita whose ore quay is in Kokaya in Tamita [2] .

From a technical and economic point of view, the quality of bauxites depends essentially on their alumina (Al2O3) and silica (SiO2) content. The more alumina and the less silica bauxite contain, the greater their economic and industrial values [3] . The Al2O3 content, a criterion for the quality and economic value of bauxite, directly influences the yield of the BAYER process, the main industrial approach for extracting alumina from bauxite; gibbsite and diaspore ores are more interesting than boehmite ores in terms of processing cost [4] .

The composition of the bauxite, the level of impurities in the liquor and the optimal consumption of caustic soda determines the efficiency of the refinery. Thus, precise analyses of the Al2O3 content, its mineralogical form, and the impurities of the bauxite are essential for the evaluation of the deposits, which optimizes the exploitation of the mine and the management of the refinery. The lack of scientific data on bauxite indices makes their valorization difficult [5] [6] . The present work aims at the chemical and mineralogical study of samples of bauxite materials from Boffa.

Nowadays, there are several analytical methods for determining the quality of bauxite. In the methodology section, we will briefly present those implemented in this study.

This study provides valuable baseline information on the chemical and mineralogical composition of these bauxites, which is essential for resource evaluation, process optimization, and economic development decisions. The study contributes to a better understanding of bauxite resources in Guinea, which is crucial given the country’s substantial reserves and global importance in aluminum production.

2. Methodology 2.1. Analytical Methods

The samples were taken from five (5) operating sites on bauxite stocks formed after blasting or the use of “surface mining”.

These samples were prepared in the laboratory by crushing, quartering, drying, grinding, pulverizing, homogenizing, and distributing them into polyethylene and codified bottles.

Materieals: personal protective equipment, plastic bags, markers, shovels, common laboratory materials, reagents (lithium bromide LiBr, lithium tetraborate and metaborate 35% Li2B4O7 - 65% LiBO2).

1) X-ray fluorescence

Principle: Fused cast-bead method

2) Phase estimation by B-Quant

Principle

B-Quant is an expert system that, from regression lines and hypotheses based on knowledge of the behavior of bauxite elements in the BAYER process, established ratios and XRF analysis results, estimates the mineralogical phases [5] . Its results have been validated by comparison with those of wet chemistry and diffractometry (mineralogy).

For all these methods, the results of the standards that accompany the unknown samples, compared to the certified values for each element, ensure that the analysis processes of our samples are under control.

This equipment was used to produce the analysis results:

Results and Discussion

Table 1 shows the X-ray fluorescence test results of the bauxite samples. Loss

<xref ref-type="bibr" rid="scirp.141491-"></xref>Table 1. Results of XRF analyses based on nature.

ID

DATE

HEURE

MINUTE

LOI

SiO2

TiO2

Fe2O3

Al2O3

ALDIFF

P2O5

K2O

CaO

V2O5

MnO

ZrO2

Cr2O3

TOTAL

240527020

27-May-24

14

39

20.27

0.98

1.78

42.03

34.28

34.95

0.23

0.01

0.05

0.13

0.02

0.05

0.09

99.90

240527021

27-May-24

14

40

21.21

1.93

2.15

36.88

37.28

37.83

0.11

0.02

0.02

0.11

0.01

0.08

0.09

99.89

240527022

27-May-24

14

41

27.13

1.05

2.32

18.76

50.32

50.75

0.09

0.01

0.01

0.10

0.01

0.07

0.08

99.95

240527023

27-May-24

14

41

23.35

1.23

2.04

31.52

41.35

41.86

0.13

0.01

0.02

0.12

0.02

0.06

0.09

99.94

240527024

27-May-24

14

42

22.08

5.15

2.81

30.83

38.58

39.14

0.19

0.01

0.02

0.13

0.03

0.06

0.05

99.92

240527025

27-May-24

14

43

25.56

3.25

2.49

20.78

47.46

47.92

0.13

0.01

0.01

0.09

0.01

0.05

0.09

99.93

240527026

27-May-24

14

43

24.95

3.45

2.32

22.66

46.14

46.62

0.15

0.01

0.04

0.08

0.01

0.04

0.06

99.91

240527027

27-May-24

14

44

24.54

3.32

2.46

23.69

45.53

45.99

0.14

0.01

0.02

0.09

0.02

0.04

0.06

99.92

240527028

27-May-24

14

45

24.85

2.61

2.69

23.60

45.79

46.25

0.12

0.01

0.04

0.08

0.02

0.05

0.06

99.92

240527029

27-May-24

14

45

24.97

3.59

2.47

20.84

47.67

48.14

0.15

0.01

0.05

0.07

0.01

0.04

0.05

99.91

240527030

27-May-24

14

46

28.03

1.45

2.61

14.93

52.59

52.98

0.08

0.03

0.02

0.08

0.03

0.04

0.05

99.94

240527031

27-May-24

14

47

18.65

6.42

1.71

42.38

30.12

30.85

0.18

0.02

0.02

0.15

0.06

0.04

0.21

99.96

240527032

27-May-24

14

47

24.02

2.44

2.07

28.67

42.25

42.80

0.12

0.01

0.01

0.11

0.02

0.05

0.14

99.92

240527033

27-May-24

14

48

23.01

2.57

2.02

31.09

40.71

41.31

0.13

0.01

0.02

0.11

0.04

0.05

0.15

99.91

240527034

27-May-24

14

49

21.49

1.31

2.28

38.47

35.84

36.45

0.15

0.01

0.03

0.11

0.04

0.08

0.09

99.91

240527035

27-May-24

14

49

27.13

1.60

2.30

17.66

50.88

51.31

0.10

0.02

0.02

0.08

0.03

0.06

0.07

99.94

240527036

27-May-24

14

50

24.22

1.86

2.24

26.67

44.53

45.01

0.14

0.01

0.01

0.08

0.02

0.07

0.09

99.94

240527037

27-May-24

14

51

24.66

1.21

2.13

28.01

43.44

43.98

0.14

0.01

0.01

0.10

0.04

0.06

0.12

99.95

240527038S

27-May-24

14

51

25.66

1.90

3.04

19.54

49.25

49.86

0.17

0.02

0.02

0.12

0.02

0.06

0.10

99.91

240527039

27-May-24

14

53

19.96

0.98

1.61

41.88

34.84

35.58

0.19

0.00

0.03

0.14

0.03

0.07

0.14

99.87

240527040

27-May-24

14

53

17.13

2.40

1.42

52.12

26.07

26.93

0.18

0.04

0.01

0.18

0.03

0.09

0.22

99.89

240527041

27-May-24

14

54

21.80

1.91

2.46

34.60

38.64

39.24

0.10

0.01

0.03

0.14

0.04

0.06

0.14

99.91

240527042

27-May-24

14

55

25.56

1.45

2.50

23.34

46.70

47.15

0.09

0.01

0.02

0.10

0.03

0.04

0.12

99.96

240527043

27-May-24

14

55

20.94

1.34

2.70

38.95

35.41

36.08

0.17

0.00

0.01

0.12

0.09

0.05

0.14

99.91

240527044

27-May-24

14

56

24.06

2.43

2.69

25.60

44.72

45.22

0.09

0.01

0.02

0.13

0.04

0.05

0.11

99.94

240527045

27-May-24

14

57

20.53

1.25

1.98

38.96

36.80

37.28

0.11

0.01

0.01

0.10

0.03

0.05

0.10

99.93

240527046

27-May-24

14

57

24.54

2.07

2.91

25.72

44.21

44.76

0.10

0.01

0.02

0.15

0.04

0.04

0.14

99.95

240527047

27-May-24

14

58

24.23

7.21

2.13

21.21

44.70

45.23

0.11

0.10

0.01

0.08

0.03

0.04

0.08

99.93

240527048

27-May-24

14

59

26.08

5.41

2.25

17.56

48.18

48.71

0.09

0.13

0.01

0.07

0.02

0.05

0.07

99.92

240527049

27-May-24

14

59

26.17

5.49

2.13

17.48

48.25

48.74

0.09

0.12

0.01

0.07

0.02

0.04

0.07

99.93

240527050

27-May-24

15

00

24.69

5.88

2.26

21.96

44.61

45.21

0.12

0.16

0.02

0.08

0.02

0.04

0.08

99.92

240527051

27-May-24

15

01

23.73

7.29

2.07

22.34

43.92

44.56

0.12

0.21

0.02

0.08

0.01

0.04

0.07

99.90

240527052

27-May-24

15

01

25.30

3.74

2.01

23.20

45.23

45.75

0.13

0.09

0.01

0.08

0.01

0.05

0.09

99.94

240527053

27-May-24

15

02

28.85

0.86

2.75

14.23

52.98

53.31

0.08

0.01

0.01

0.09

0.01

0.04

0.06

99.96

240527054

27-May-24

15

03

25.00

4.39

2.13

22.26

45.80

46.22

0.10

0.01

0.01

0.10

0.01

0.05

0.08

99.94

240527055

27-May-24

15

03

27.54

1.53

2.11

17.98

50.47

50.85

0.08

0.01

0.02

0.08

0.01

0.03

0.06

99.92

240527056

27-May-24

15

04

26.66

2.21

2.05

17.96

50.71

51.12

0.09

0.01

0.01

0.09

0.01

0.04

0.09

99.92

240527057S

27-May-24

15

05

25.72

1.86

3.03

19.50

49.30

49.89

0.17

0.02

0.02

0.12

0.02

0.06

0.10

99.92

240527058

27-May-24

14

52

28.17

2.08

2.63

12.77

54.02

54.35

0.07

0.03

0.02

0.08

0.01

0.04

0.06

99.96
<xref ref-type="bibr" rid="scirp.141491-"></xref>Table 2. B-Quant.

ID

DATE

HEURE

MINUTE

LOI

AL-143

AL-235

Mono

240527020

27-May-24

14

39

20.27

240527021

27-May-24

14

40

21.21

240527022

27-May-24

14

41

27.13

45.51

48.74

3.23

240527023

27-May-24

14

41

23.35

240527024

27-May-24

14

42

22.08

240527025

27-May-24

14

43

25.56

41.41

44.24

2.83

240527026

27-May-24

14

43

24.95

39.93

42.83

2.89

240527027

27-May-24

14

44

24.54

38.82

42.24

3.42

240527028

27-May-24

14

45

24.85

39.83

43.07

3.23

240527029

27-May-24

14

45

24.97

39.83

44.29

4.45

240527030

27-May-24

14

46

28.03

48.01

50.93

2.92

240527031

27-May-24

14

47

18.65

240527032

27-May-24

14

47

24.02

37.81

39.39

1.58

240527033

27-May-24

14

48

23.01

240527034

27-May-24

14

49

21.49

240527035

27-May-24

14

49

27.13

45.62

49.03

3.41

240527036

27-May-24

14

50

24.22

38.21

42.06

3.85

240527037

27-May-24

14

51

24.66

39.41

41.25

1.84

240527039

27-May-24

14

53

19.96

240527040

27-May-24

14

53

17.13

240527041

27-May-24

14

54

21.80

240527042

27-May-24

14

55

25.56

41.61

44.67

3.06

240527043

27-May-24

14

55

20.94

240527044

27-May-24

14

56

24.06

37.81

41.97

4.16

240527045

27-May-24

14

57

20.53

240527046

27-May-24

14

57

24.54

39.01

41.55

2.54

240527047

27-May-24

14

58

24.23

38.31

39.13

0.82

240527048

27-May-24

14

59

26.08

43.61

44.06

0.45

240527049

27-May-24

14

59

26.17

43.81

44.12

0.31

240527050

27-May-24

15

00

24.69

39.42

40.04

0.62

240527051

27-May-24

15

01

23.73

37.01

37.90

0.89

240527052

27-May-24

15

01

25.30

41.11

41.80

0.69

240527053

27-May-24

15

02

28.85

50.01

51.56

1.55

240527054

27-May-24

15

03

25.00

40.01

41.78

1.77

240527055

27-May-24

15

03

27.54

46.61

48.54

1.93

240527056

27-May-24

15

04

26.66

44.20

48.34

4.14

240527058

27-May-24

14

52

28.17

48.41

52.10

3.69

on ignition (LOM) indicates the rate of volatile matter including organic matter. In these samples, LOM rates are high, we recommend that these plants do stripping to remove organic matter followed by leaching by rainwater.

Trace elements and minor oxides are in acceptable proportions (P2O5, MnO, CaO, V2O5, TiO2, K2O, ZrO2, Cr2O3).

On the other hand, iron oxide Fe2O3 is high. It is correlated with total alumina, varying in the opposite direction, which predicts a significant volume of residues (sludge and sand). The correlation between Fe₂O₃ and Al₂O₃ in bauxite analyzed by XRF results from both geochemical (formation processes and mineralogy) and analytical (matrix effects and sizing) factors. A negative correlation is often observed but may vary depending on the type of bauxite and analytical conditions.

Table 2 of the phase analysis by B-Quant (version 98) shows that:

 3. Conclusion

The government has an interest in imposing a cut-off grade of 40% for export and 34% for local refineries. Boffa bauxites have specific characteristics in terms of mineralogical composition and impurity content. It is therefore recommended to use local reference samples for the calibration of the XRF apparatus, to consider, the geochemical particularities of the region. In addition, adequate sample preparation, including calcination and fusion with an appropriate flux, is essential to minimize matrix effects and obtain accurate results. The determination of the alumina (Al2O3) content in bauxites, particularly those from the Boffa region in Guinea, is essential to assess their quality and industrial potential. X-ray fluorescence (XRF) analysis is a commonly used method for this determination due to its speed, accuracy and cost.

 Acknowledgements

This research was funded by MESRSI, the Ministry of Higher Education, Scientific Research, and Innovation in the Republic of Guinea. The authors thank the Chemical Laboratory of the Bauxite Company of Guinea (CBG) for their collaboration in carrying out the research.

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