**3.5 Characterization of nDCPD**

**Figure 12** shows the SEM image of the nDCPD doped with the Ni, Co, and Cu ions, where the main characteristics of nDCPD (**Figure 12a**), monoclinic disk morphology [1, 15, 29, 39], which does not present significant changes in the presence of Ni (**Figure 12b**), Co (**Figure 12c**), and Cu (**Figure 12d**) ions can be observed, probably because the vast majority of metal ions are adsorbed on the surface of nDCPD. The XRD patterns of nDCPD doped with Ni, Co, and Cu are shown in **Figure 13**, and according to the International Center of Diffraction Data Chart (JCPDS) database, some changes are observed in the samples with metal ions compared to that of nDCPD without doping [1]. The peaks at ∽32° and 40° increase in intensity, while at ∽34°, the intensity of the peaks directly related to the presence of Ni, Co, and Cu ions decreases. While at 26, 29, and 53°, new peaks appear in the doped brushite samples, which also caused a decrease in the network parameter of 4.99 nm, a value lower than the 5.77 nm obtained for nDCPD, without doping, together with the particle size from 9.26 to 4.45, 4.08, and 4.35 Å, for Ni, Co, and Cu, respectively, which was determined with the Scherrer Equation [39, 40]. This may be due to the fact that the Ca ions of nDCPD without doping (1.12 Å) are replaced during the adsorption process by the ions of Ni (0.78 Å), Co (0.63 Å), and Cu (0.69 Å), which implies that part of the ions are retained inside the structure of nDCPD [40].

**105**

**Figure 13.**

**Figure 12.**

*The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes*

In **Figure 14**, the infrared spectra of nDCPD are presented, where the characteristic peaks of the groups that make up apatite are observed, among which the

tions of flexing of the phosphate groups; while the signal at 790 cm**−**<sup>1</sup>

, characteristic of the vibra-

, there are peaks related to

is due to

presence of a doublet stands out at 577 and 526 cm**−**<sup>1</sup>

*X-ray diffraction patterns of nCDPD doped with the different metal ions.*

*Micrographs obtained in SEM: (a) brushite, (b) Ni, (c) Co, and (d) Cu.*

bending out of the P-O-H plane; at 987 and 873 cm**−**<sup>1</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.86803*

*The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes DOI: http://dx.doi.org/10.5772/intechopen.86803*

#### **Figure 12.**

*Water Chemistry*

**Figure 11.**

**Table 6.**

**104**

nDCPD [40].

**3.5 Characterization of nDCPD**

*Removal of Cu and Co ions in the aqueous solution at 45°C.*

Pseudo-first order *dq*

Pseudo-second order *dq*

Elovich *dq*

External diffusion (DE) *ln*(

*Adsorption isotherm models used for the analysis of experimental data.*

Intraparticle diffusion (DI) *q* = *kid t*

**Figure 12** shows the SEM image of the nDCPD doped with the Ni, Co, and Cu ions, where the main characteristics of nDCPD (**Figure 12a**), monoclinic disk morphology [1, 15, 29, 39], which does not present significant changes in the presence of Ni (**Figure 12b**), Co (**Figure 12c**), and Cu (**Figure 12d**) ions can be observed, probably because the vast majority of metal ions are adsorbed on the surface of nDCPD. The XRD patterns of nDCPD doped with Ni, Co, and Cu are shown in **Figure 13**, and according to the International Center of Diffraction Data Chart (JCPDS) database, some changes are observed in the samples with metal ions compared to that of nDCPD without doping [1]. The peaks at ∽32° and 40° increase in intensity, while at ∽34°, the intensity of the peaks directly related to the presence of Ni, Co, and Cu ions decreases. While at 26, 29, and 53°, new peaks appear in the doped brushite samples, which also caused a decrease in the network parameter of 4.99 nm, a value lower than the 5.77 nm obtained for nDCPD, without doping, together with the particle size from 9.26 to 4.45, 4.08, and 4.35 Å, for Ni, Co, and Cu, respectively, which was determined with the Scherrer Equation [39, 40]. This may be due to the fact that the Ca ions of nDCPD without doping (1.12 Å) are replaced during the adsorption process by the ions of Ni (0.78 Å), Co (0.63 Å), and Cu (0.69 Å), which implies that part of the ions are retained inside the structure of

**Model Equation Ref.**

\_\_\_

\_\_\_ *dt* <sup>=</sup> *<sup>k</sup>*<sup>2</sup> (*qe* <sup>−</sup> *<sup>q</sup>*)

> \_\_\_ *dt* <sup>=</sup> *<sup>α</sup><sup>e</sup>* −*q*

\_\_\_*C*

*dt* <sup>=</sup> *<sup>k</sup>*1(*qe* <sup>−</sup> *<sup>q</sup>*) [35]

*<sup>C</sup>*0) <sup>=</sup> <sup>−</sup>*kextt* [37]

2

0.5

*Micrographs obtained in SEM: (a) brushite, (b) Ni, (c) Co, and (d) Cu.*

**Figure 13.** *X-ray diffraction patterns of nCDPD doped with the different metal ions.*

In **Figure 14**, the infrared spectra of nDCPD are presented, where the characteristic peaks of the groups that make up apatite are observed, among which the presence of a doublet stands out at 577 and 526 cm**−**<sup>1</sup> , characteristic of the vibrations of flexing of the phosphate groups; while the signal at 790 cm**−**<sup>1</sup> is due to bending out of the P-O-H plane; at 987 and 873 cm**−**<sup>1</sup> , there are peaks related to

#### **Figure 14.**

*Infrared spectrum of pure nCDPD doped with Ni, Co, and Cu.*

the stretching of P-O (H) in the HPO**−**<sup>2</sup> 4. On the other hand, the signals found at 1138, 1120, 1065, and 1004 cm**−**<sup>1</sup> are attributed to the stretching of the P-O link. At 1215 cm**−**<sup>1</sup> the signal generated by the flexion of the O-H group plane is presented, and the peaks observed at 665 and 1651 cm**−**<sup>1</sup> are related to the binding vibrations and physical vibrations of the water molecule. Additionally, a shoulder at 1725 cm**−**<sup>1</sup> was observed, which is related to the flexural stress of the water molecule, and the signals obtained at 3548, 3484, 3278, and 3166 cm**−**<sup>1</sup> are related to the extension of the water molecule in the apatite. Finally, a band at 2944 cm**−**<sup>1</sup> was also observed, directly related to the stretching of PO-H that occurs in HPO [1, 41, 42]. In the case of the nDCPD spectra with the different metal ions, it was observed that several peaks decrease in intensity or disappear as a result of the presence of Ni, Co, and Cu; these signals are related to the PO3 **−**4 and OH groups, with which it can be inferred that the groups present on the surface of this apatite participate in the adsorption of metals directly.
