*3.1.3 Phosphorite before ion exchange experiments*

Phosphorites are sedimentary rocks that contain at least 20% P2O5 in the form of cryptocrystalline fluorapatite, apatite, or some other minerals containing

**Figure 2.** *SEM analysis of bentonite: (a) point microanalysis by SEM-EDS and (b) general image (SEM-SE).*

**209**

Ca2+, K+

**Figure 3.**

**Table 3.**

, and Mg2+.

*X-ray diffractogram of bentonite after ion exchange.*

*Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals...*

Au 45.93 0.072 99.84 Ce 81.79 0.000 100.00 La 51.89 0.000 100.00 Nd 56.97 0.020 99.96 Pd 1.92 0.108 94.37 Yb 33.35 0.009 99.97 Ge 9 0 100 Gd 1.4 0.111 92.07 Tb 0.25 0 100 Sm 1.75 0 100 Er 0.9 0 100 Eu 0.35 0.011 96.86 Pt 0.005 0 100

**Content after ion exchange (ppm)**

**Efficiency of the ion exchange (%)**

phosphorus. They usually occur in layers, and it can also be present in the form of crusts, spherulites, and nodules in sedimentary horizons. Rocks with less than 10% phosphate receive the adjective of phosphates. Its main interchangeable cations are:

Before carrying out the ion exchange experiments, the phosphorite was characterized to know its composition and compare it at the end of the ion exchange

*DOI: http://dx.doi.org/10.5772/intechopen.88742*

*Results of the ion exchange done using bentonite (ICP).*

**exchange (ppm)**

**Element Content before ion** 


*Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals... DOI: http://dx.doi.org/10.5772/intechopen.88742*

#### **Table 3.**

*Trace Metals in the Environment - New Approaches and Recent Advances*

silicoaluminates (paragonite and gmelinite).

surface and contact area, **Figure 2b**.

*3.1.2 Bentonite after ion exchange experiments*

leaching liquor, the efficiency is over 90%.

*3.1.3 Phosphorite before ion exchange experiments*

absorbent.

the bentonite ore.

anorthoclase, orthoclase, albite, and berlinite, can be seen, as well as sodium

On the other hand, **Figure 2** shows an image of a bentonite particle at −400 mesh, analyzed by SEM-EDS, where the semiquantitative and point composition can be observed, showing the presence of elements such as silicon, aluminum, sodium, magnesium, potassium, and iron, which are characteristic in the bentonite (**Figure 2a**); likewise, the bentonite particle is shown in detail, having a lot of porosity, which is essentially one of the most important physical characteristics for the ion exchange that could be carried out, besides the particle size, offering a large

The results obtained after ion exchange experiments are presented as chemical composition of liquors before and after the procedure; **Table 3** shows the chemical composition of these liquors obtained by ICP, showing also the efficiency of ion exchange for each element. It can be noticed that for all elements present in original

After the ion exchange, the solution was filtered and the solid residue of the bentonite was dried and analyzed by XRD. The mineral species identified by X-ray diffraction (**Figure 3**), are majority mineral phases, such as quartz, anorthoclase, orthoclase, albite, berlinite, and silico-aluminates, typical of bentonite. Likewise, signs indicating the presence of rare earths and precious metals are noted, which corroborates that the exchange of these elements was made to the natural

Finally, **Figure 4** shows the image of a bentonite particle after performing the ion exchange with the leaching liquors of a SEDEX-type mineral, where the semiquantitative composition and the distribution of the elements are shown by X-ray mapping, observing that, indeed, the aforementioned elements were absorbed in

Phosphorites are sedimentary rocks that contain at least 20% P2O5 in the form

of cryptocrystalline fluorapatite, apatite, or some other minerals containing

*SEM analysis of bentonite: (a) point microanalysis by SEM-EDS and (b) general image (SEM-SE).*

**208**

**Figure 2.**

*Results of the ion exchange done using bentonite (ICP).*

#### **Figure 3.**

*X-ray diffractogram of bentonite after ion exchange.*

phosphorus. They usually occur in layers, and it can also be present in the form of crusts, spherulites, and nodules in sedimentary horizons. Rocks with less than 10% phosphate receive the adjective of phosphates. Its main interchangeable cations are: Ca2+, K+ , and Mg2+.

Before carrying out the ion exchange experiments, the phosphorite was characterized to know its composition and compare it at the end of the ion exchange

#### **Figure 4.**

*Photomicrographs of bentonite after ion exchange: (a) general microanalysis SEM-EDS; (b) general image, 2000×, SEM-SE; (c) point image where the microanalysis was taken; and (d) distribution mapping of rare earth elements and precious metals in the bentonite.*


#### **Table 4.**

*Average chemical composition of phosphorite before ion exchange.*

experiments, and thus to evaluate its exchange capacity for the elements present in the leaching liquors. **Table 4** shows the results obtained by ICP and XRF of the chemical composition for the phosphorite, where the average contents of 36% of P2O5 are shown, as well as the majority of aluminum, calcium, and minor elements such as oxides of sodium, potassium, titanium, and iron.

On the other hand, the mineral species identified by X-ray diffraction (**Figure 5**) are mainly mineral phases of calcium and phosphorus.

Finally, in **Figure 6**, an image of phosphorite particles at −400 mesh can be seen, which was analyzed by SEM-EDS, and here, also the presence of major elements of phosphorus, aluminum, and calcium oxides, as well as minor elements of sodium, titanium and iron, can be observed, as is shown in **Figure 6a**; similarly, the photomicrographs of the phosphorite particle are shown in **Figure 6b**.

**211**

**Figure 5.**

**Figure 6.**

*SEM-SE.*

*Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals...*

*DOI: http://dx.doi.org/10.5772/intechopen.88742*

*3.1.4 Phosphorite after ion exchange experiments*

*X-ray diffractogram of phosphorite, before ion exchange.*

After carrying out the ion exchange, using phosphorite as an absorbent mineral, the solution was filtered and analyzed by ICP, comparing the results with the initial composition of the leaching liquors. The results are shown in **Table 5**, where a comparison is made between the original leaching liquors before and after the exchange, as well as the efficiency of the cation exchange of this mineral; it is observed that in all cases, efficiencies are greater than 99% of the elements exchanged, which can determine that phosphorite is a good natural absorbent for rare earths and precious metals. Likewise, the solids obtained after the ion exchange were separated and dried to be later analyzed by XRD. The mineral species identified by X-ray diffraction (**Figure 7**) are majority phases such as quartz, anorthoclase, orthoclase, albite,

*Photomicrographs of the phosphorite −400 meshes, (a) SEM-EDS microanalysis and (b) general image, 2200×,* 

*Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals... DOI: http://dx.doi.org/10.5772/intechopen.88742*

**Figure 5.**

*Trace Metals in the Environment - New Approaches and Recent Advances*

experiments, and thus to evaluate its exchange capacity for the elements present in the leaching liquors. **Table 4** shows the results obtained by ICP and XRF of the chemical composition for the phosphorite, where the average contents of 36% of P2O5 are shown, as well as the majority of aluminum, calcium, and minor elements

**Element ICP (wt.%) XRF (wt.%)** Na2O 0 0.16 Al2O3 2.43 2.40 P2O5 36.03 36.08 K2O 0.15 0.21 CaO 59.99 59.95 TiO2 0.48 0.31 Fe2O3 0.92 0.89

*Photomicrographs of bentonite after ion exchange: (a) general microanalysis SEM-EDS; (b) general image, 2000×, SEM-SE; (c) point image where the microanalysis was taken; and (d) distribution mapping of rare* 

On the other hand, the mineral species identified by X-ray diffraction (**Figure 5**)

Finally, in **Figure 6**, an image of phosphorite particles at −400 mesh can be seen, which was analyzed by SEM-EDS, and here, also the presence of major elements of phosphorus, aluminum, and calcium oxides, as well as minor elements of sodium, titanium and iron, can be observed, as is shown in **Figure 6a**; similarly, the photo-

such as oxides of sodium, potassium, titanium, and iron.

*Average chemical composition of phosphorite before ion exchange.*

*earth elements and precious metals in the bentonite.*

are mainly mineral phases of calcium and phosphorus.

micrographs of the phosphorite particle are shown in **Figure 6b**.

**210**

**Table 4.**

**Figure 4.**

*X-ray diffractogram of phosphorite, before ion exchange.*

**Figure 6.** *Photomicrographs of the phosphorite −400 meshes, (a) SEM-EDS microanalysis and (b) general image, 2200×, SEM-SE.*

#### *3.1.4 Phosphorite after ion exchange experiments*

After carrying out the ion exchange, using phosphorite as an absorbent mineral, the solution was filtered and analyzed by ICP, comparing the results with the initial composition of the leaching liquors. The results are shown in **Table 5**, where a comparison is made between the original leaching liquors before and after the exchange, as well as the efficiency of the cation exchange of this mineral; it is observed that in all cases, efficiencies are greater than 99% of the elements exchanged, which can determine that phosphorite is a good natural absorbent for rare earths and precious metals.

Likewise, the solids obtained after the ion exchange were separated and dried to be later analyzed by XRD. The mineral species identified by X-ray diffraction (**Figure 7**) are majority phases such as quartz, anorthoclase, orthoclase, albite,

berlinite, and silicoaluminates. Similarly, the presence of rare earths, such as lanthanum and cerium, and precious metals that were all adsorbed by this mineral are noted.


#### **Table 5.**

*Results of the ion exchange done using phosphorite (ICP).*

**213**

**Table 6.**

**Figure 8.**

*elements and precious metals in the phosphorite.*

*Average chemical composition of diatomite before ion exchange.*

*Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals...*

Finally, **Figure 8** shows the image of phosphorite particles after performing the ion exchange with the leaching liquors of a SEDEX-type mineral, where the semiquantitative point composition and the X-ray mapping of the elements are shown. This verifies that effectively the aforementioned elements were absorbed in the mineral.

Diatomite is a siliceous sedimentary rock of biogenic origin, composed of fossilized skeletons of diatomite frustules. It is composed by sedimentary accumulation

*Photomicrographs of the phosphorite after ion exchange: (a) SEM-EDS microanalysis; (b) general image, 2000×, SEM; (c) point image where the microanalysis was taken; and (d) distribution mapping of rare earth* 

**Element ICP (wt.%) XRF (wt.%)** Na2O 0.61 0.923 MgO 1.79 1.87 Al2O3 11.63 7.77 SiO2 76.00 77.36 K2O 2.41 1.2 CaO 0.85 1.04 TiO2 0.50 0.348 Fe2O3 1.95 2.35

*DOI: http://dx.doi.org/10.5772/intechopen.88742*

*3.1.5 Diatomite before ion exchange experiments*

**Figure 7.** *X-ray diffractogram of phosphorite material after ion exchange.* *Use of Porous no Metallic Minerals to Remove Heavy Metals, Precious Metals... DOI: http://dx.doi.org/10.5772/intechopen.88742*

Finally, **Figure 8** shows the image of phosphorite particles after performing the ion exchange with the leaching liquors of a SEDEX-type mineral, where the semiquantitative point composition and the X-ray mapping of the elements are shown. This verifies that effectively the aforementioned elements were absorbed in the mineral.
