*3.1.5 Diatomite before ion exchange experiments*

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

#### **Figure 8.**

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

are noted.

**Table 5.**

**Element Content before ion** 

**exchange (ppm)**

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

*X-ray diffractogram of phosphorite material after ion exchange.*

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

Au 45.93 0 100 Ce 81.79 0.037 99.95 La 51.89 0.017 99.97 Nd 56.97 0.02 99.96 Pd 1.92 0 100 Yb 33.35 0.001 99.99 Ge 9 0 100 Gd 1.4 0.008 99.43 Tb 0.25 0 100 Sm 1.75 0 100 Er 0.9 0 100 Eu 0.35 0 100 Pt 0.005 0 100

**Content after ion exchange (ppm)**

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

**212**

**Figure 7.**

*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 elements and precious metals in the phosphorite.*


#### **Table 6.**

*Average chemical composition of diatomite before ion exchange.*

to form large deposits with a sufficient thickness to have a commercial potential. Its main interchangeable cations are Na+ , Ca2+, K+ , Mg2+, and Si2+.

Firstly, before carrying out the ion exchange experiments, the diatomite mineral was characterized to evaluate, at the end, its exchange capacity. **Table 6** summarizes the results obtained by ICP and XRF of the original elements contained in the diatomite, presenting average contents of 76.68% of silicon, as well as the majority contents of alumina, hematite, potassium oxide, magnesium oxide, calcium oxide, and minor elements such as sodium oxide and titanium.

Likewise, the mineral species present in the diatomite were identified by X-ray diffraction (**Figure 9**), observing the presence of majority mineral phases such as quartz, albite and berlinite.

Finally, in **Figure 10**, an image of a diatomite particle at −400 mesh is shown, in which an analysis was carried out by SEM-EDS. The presence of major elements such as silicon, aluminum, sodium, magnesium, potassium, and iron, are characteristic of the diatomite. Likewise, a photomicrograph of the diatomite particle can be seen in **Figure 10b** where the characteristics properties of the diatoms of the material can be observed.

**Figure 9.**

*X-ray diffractogram of diatomite material before ion exchange.*

#### **Figure 10.**

*Photomicrographs of the diatomite −400 meshes, (a) SEM-EDS microanalysis and (b) general image, 4000×, SEM-SE.*

**215**

**Figure 11.**

**Table 7.**

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

After carrying out the ion exchange, the diatomite mineral was characterized to know the elements exchanged and thus calculate the ion exchange capacity of this mineral. The results are shown in **Table 7**, where a comparison is made between the original leaching liquors and after the exchange through ICP analysis. Likewise, it shows the % of efficiency of the cation exchange and as a result can be seen that

Au 45.93 0 100 Ce 81.79 0.003 99.996 La 51.89 0.004 99.99 Nd 56.97 0.008 99.99 Pd 1.92 0 100 Yb 33.35 0.001 99.997 Ge 9.0 0 100 Gd 1.4 0.03 97.86 Tb 0.25 0 100 Sm 1.75 0 100 Er 0.9 0 100 Eu 0.35 0.003 99.14 Pt 0.005 0 100

**Content after ion exchange (ppm)**

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

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

**Element Content before ion** 

*3.1.6 Diatomite after ion exchange experiments*

**exchange (ppm)**

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

*X-ray diffractogram of diatomite 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*
