*3.8. SEM Characterization*

In order to explore the surface characteristics (texture, pore, and pore size) of soils and OPBS, SEM analyses are presented in Figure 8. Micrographs (d, e, and f) indicate that the soil samples had approximately the same size with a prismatic shape. The micrograph scale indicates that soil particles were large in diameter and display low porosity surfaces (micrographs d and e). Indeed, the absence of laminated and porous structures indicates the presence of clayey minerals and confirms the dominance of quartz in the soil samples.

However, tiny layers have covered the quartz mineral in minor portions in some spots with a relatively low surface porosity (micrograph f). Unlike soil samples, the OPBS SEM observations demonstrate a larger porous area (micrographs a and b). In addition, the OPBS surface was characterized by a hollow surface with different pore size distributions (micrograph c). The SEM micrograph confirmed that the R'mel agricultural soils had principally a macrostructure composed mostly of larger SiO<sup>2</sup> particles, as well as a reduced pore volume (macropores). In contrast, SEM analysis revealed the abundance of pore distribution on the OPBS surface. Finally, the OPBS morphological characteristics could be useful to fill the voids between soil particles and thereby increase the surface area and water-retention capacity of soil. Moreover, the available mesopore sites on the OPBS surface could interact with the soil–water solution and adsorb different pollutants. *C* **2023**, *9*, x FOR PEER REVIEW 18 of 22

**Figure 8.** SEM micrographs (different magnifications) of OPBS (**a**–**c**) and soils (**d**–**f**). **Figure 8.** SEM micrographs (different magnifications) of OPBS (**a**–**c**) and soils (**d**–**f**).

The properties of three agricultural soils and olive pomace biomass slag (OPBS) were

(1) The R'mel soils were coarser in texture, with low clay, silt, and OM, low CEC, limited adsorption sites, and poor nutrient availability. In contrast, the clayey fraction (FF) exhibited significant water content, OM, CaCO3, and heavy-metal adsorption capac-

ity despite its low percentage in the soil (<5%).

**4. Conclusions and Perspectives** 
