*3.1.6 Diatomite after ion exchange experiments*

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

and minor elements such as sodium oxide and titanium.

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

main interchangeable cations are Na+

quartz, albite and berlinite.

material can be observed.

to form large deposits with a sufficient thickness to have a commercial potential. Its

, Ca2+, K+

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,

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

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

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

, Mg2+, and Si2+.

**214**

**Figure 10.**

*SEM-SE.*

**Figure 9.**

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


#### **Table 7.** *Results of the ion exchange done using diatomite (ICP).*

**Figure 11.**

*X-ray diffractogram of diatomite material, after ion exchange.*

**Figure 12.**

*Photomicrograph of the diatomite −400 meshes, (a) SEM-EDS microanalysis, (b and c) general image, SEM-SE, and (d) mappings.*

diatomite shows an exchange efficiency for the precious metals of 100%, as well as the Pd, Ge, Tb, Sm, and Er. The other elements show an efficiency superior to 99%, not so for the Gd, since its exchange efficiency is 97.86, which corroborates that the diatomite has an exchange efficiency for these types of metals. On the other hand, the author also has to demonstrate the efficiency of cationic exchange of diatomite, getting 96.46% of efficiency for the removal of As3+, 95.44% for Ni2+, and 98.80% of Pb2+ [13].

Likewise, the mineral species were identified by X-ray diffraction (**Figure 11**), observing the presence of majority mineral phases such as quartz, anorthoclase, orthoclase, albite and berlinite; as well as the presence of rare earths such as Er, La, and Eu.

Finally, **Figure 12** shows the image of a diatomite particle after ion exchange with the leaching liquors of a SEDEX type mineral, where can be observed the semiquantitative point composition and the distribution of elements by X-ray mapping, can be concluded that the elements present in the leaching liquors were effectively absorbed into the diatomite particles.

### **4. Conclusions**

The preliminary results in the cation exchange of heavy metals, precious metals, and rare earths, through the use of non-metallic porous minerals, show a good efficiency since for most of the cases, recoveries over 99% were obtained, except for some elements; in the case of bentonite, for Pd, only 94.37%, for Gd, only 92.09%, and for Eu, only 96.87% absorption were obtained, and in the case of the phosphorite, the lowest value was for Gd with a 99.43% efficiency; in the case of diatomite, Gd presented a 97.86% efficiency in the exchange (**Table 8**). Therefore, it can be concluded that these natural absorbers can be used with a high efficiency for the exchange of these metals, noting also that for most of the cases, Gd presented recoveries above 90% and for the case of the precious metals, it was above 99% for all the minerals used.

**217**

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

Au 99.84 100 100 Ce 100.00 99.95 99.996 La 100.00 99.97 99.99 Nd 99.96 99.96 99.99 Pd 94.37 100 100 Yb 99.97 99.99 99.99 Ge 100 100 100 Gd 92.07 99.43 97.86 Tb 100 100 100 Sm 100 100 100 Er 100 100 100 Eu 96.86 100 99.14 Pt 100 100 100

**Phosphorite % in CEC**

**Diatomite % in CEC**

**% in CEC**

The authors would like to thank the PRODEP-SEP of the government of Mexico for the financial support in the publishing of this chapter. Also thy would like to thank Autonomous University of the State of Hidalgo and the CONACyT for the Master degree scholarship granted to the student Edgar Omar Mejía Serrano who

*Cation exchange capacity (CEC), per element, of the mineral used for the removal of precious metals, heavy* 

This chapter not only shows unpublished preliminary results obtained by the authors where they have evaluated the capacity of ion exchange for some natural minerals found in the state of Hidalgo Mexico, but also exhibits an exhalative sedimentary mineral found by the same authors in the north of the state of Hidalgo, where ore mineral has important contents of precious metals and some rare earths

worked this theme, during his thesis project (number 627910).

The authors declare no conflict of interest.

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

**Element Bentonite**

**Acknowledgements**

*metals and rare earth elements.*

**Conflict of interest**

**Notes**

**Table 8.**

elements.


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

#### **Table 8.**

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

diatomite shows an exchange efficiency for the precious metals of 100%, as well as the Pd, Ge, Tb, Sm, and Er. The other elements show an efficiency superior to 99%, not so for the Gd, since its exchange efficiency is 97.86, which corroborates that the diatomite has an exchange efficiency for these types of metals. On the other hand, the author also has to demonstrate the efficiency of cationic exchange of diatomite, getting 96.46% of efficiency for the removal of As3+, 95.44% for Ni2+, and 98.80% of Pb2+ [13]. Likewise, the mineral species were identified by X-ray diffraction (**Figure 11**), observing the presence of majority mineral phases such as quartz, anorthoclase, orthoclase, albite and berlinite; as well as the presence of rare earths such as

*Photomicrograph of the diatomite −400 meshes, (a) SEM-EDS microanalysis, (b and c) general image,* 

Finally, **Figure 12** shows the image of a diatomite particle after ion exchange with the leaching liquors of a SEDEX type mineral, where can be observed the semiquantitative point composition and the distribution of elements by X-ray mapping, can be concluded that the elements present in the leaching liquors were

The preliminary results in the cation exchange of heavy metals, precious metals, and rare earths, through the use of non-metallic porous minerals, show a good efficiency since for most of the cases, recoveries over 99% were obtained, except for some elements; in the case of bentonite, for Pd, only 94.37%, for Gd, only 92.09%, and for Eu, only 96.87% absorption were obtained, and in the case of the phosphorite, the lowest value was for Gd with a 99.43% efficiency; in the case of diatomite, Gd presented a 97.86% efficiency in the exchange (**Table 8**). Therefore, it can be concluded that these natural absorbers can be used with a high efficiency for the exchange of these metals, noting also that for most of the cases, Gd presented recoveries above 90% and for the

case of the precious metals, it was above 99% for all the minerals used.

**216**

Er, La, and Eu.

**Figure 12.**

*SEM-SE, and (d) mappings.*

**4. Conclusions**

effectively absorbed into the diatomite particles.

*Cation exchange capacity (CEC), per element, of the mineral used for the removal of precious metals, heavy metals and rare earth elements.*
