*3.1.4 XRD analysis*

X-ray diffraction analysis allows us to identify the different mineralogical phases contained in our material. The X-ray diffraction patterns of NSC adsorbent are illustrated in **Figure 6**. This result demonstrated the principal presence of kaolinite characterized by an intense peak at 2θ = 26.63° (2θ = 26.63°; d = 3.343 A°) and a series of peaks with varying intensities at 12.33°, 19.75°, 40.85° and those of quartz at 20.87°, 37.92°, and 42. 440°. In addition, the reflections spectrum at 2θ = 8.62°, 29.47°, and 30.81° confirm the presence of illite, calcite, and dolomite, respectively. We see that the diagram also shows the presence of the peak corresponding to the following

*Use of Natural Safiot Clay for the Removal of Chemical Substances from Aqueous Solutions… DOI: http://dx.doi.org/10.5772/intechopen.101605*

**Figure 5.** *SEM micrograph of the natural Safi clay before (a) and after (b) adsorption.*

minerals: kaolinite, calcite, and vermiculite, which implies that our clay is heterogeneous.

### *3.1.5 Determination of pH zero-point charge*

The pH zero-point charge (pHzpc) plays an important role in the adsorption process. The point of zero charge (PZC) of our clay was determined using the pH drift method [37]. Six vials containing solutions of pH in the range of 2–12 (pHi) and 50 mg of NSC are shaken for 24 h at room temperature, and the final pH was measured. The difference between the initial and final pH (ΔpH = pHi pHf) was plotted against the initial pH (pHi) and the point where ΔpH = 0 was taken as the point of zero charge. As shown in **Figure 7**, the pHpzc of NSC was determined to be 7.2.

*Mineralogy*

**Figure 6.** *X-ray diffraction of natural safiot clay.*

**Figure 7.** *pHzpc values for natural safiot clay.*

## **3.2 Experimental setup: single and binary adsorption studies**
