**3. Results**

#### *3.1. Characteristics of nZVI Particles* where: Ci = initial heavy metal concentration (mg/kg of soil), Cf = final heavy metal concentration

*BET analysis*: The surface area of the chemically synthesized nZVI particles was 15.2 m<sup>2</sup> /g, and for the particles synthesized using neem and mint leaves, the surface area was 6.2 m<sup>2</sup> /g and 13.0 m<sup>2</sup> /g, respectively. (mg/kg of soil). **3. Results** 

*SEM analysis*: The SEM images are presented in Figure 1a,b (chemically synthesized nanoparticles), Figure 1c,d (nanoparticles synthesized using neem leaves), and Figure 1e,f (nanoparticles synthesized using mint leaves). The images show that the particles are spherical and subjected to agglomeration. *3.1. Characteristics of nZVI Particles BET analysis*: The surface area of the chemically synthesized nZVI particles was 15.2 m2/g, and for the particles synthesized using neem and mint leaves, the surface area was 6.2 m2/g and 13.0 m2/g,

*TEM analysis*: The TEM images are shown in Figure 2. It can be observed that the particles derived from leaf extracts are agglomerated. The color difference between the core and outer layer of the nanoparticle shows that the chemically synthesized nanoparticle (Figure 2a,b) is more subjected to oxidation than those synthesized using leaves (Figure 2c–f). respectively. *SEM analysis*: The SEM images are presented in Figure 1a,b (chemically synthesized nanoparticles), Figure 1c,d (nanoparticles synthesized using neem leaves), and Figure 1e,f (nanoparticles synthesized using mint leaves). The images show that the particles are spherical and subjected to agglomeration.

**Figure 1.** *Cont.*

*Processes* **2020**, *8*, x FOR PEER REVIEW 5 of 12

(**c**) (**d**)

**Figure 1.** SEM image of nanoscale zero-valent iron (nZVI) particles: (**a**,**b**) from chemical synthesis; (**c**,**d**) using neem leaves; (**e**,**f**) using mint leaves. **Figure 1.** SEM image of nanoscale zero-valent iron (nZVI) particles: (**a**,**b**) from chemical synthesis; (**c**,**d**) using neem leaves; (**e**,**f**) using mint leaves. derived from leaf extracts are agglomerated. The color difference between the core and outer layer of the nanoparticle shows that the chemically synthesized nanoparticle (Figure 2a,b) is more subjected to oxidation than those synthesized using leaves (Figure 2c–f).

*3.2. Soil Characteristics* 

by their low concentration.

*3.3. Remediation of Contaminated Soil* 

3.3.1. Remediation by Chemically Synthesized nZVI Particles

**Figure 2.** TEM image of nZVI particles: (**a**,**b**) chemically synthesized; (**c**,**d**) using neem leaves; (**e**,**f**) using mint leaves. **Figure 2.** TEM image of nZVI particles: (**a**,**b**) chemically synthesized; (**c**,**d**) using neem leaves; (**e**,**f**) using mint leaves.

**Table 1.** Initial characteristics of the soil samples. **Characteristics Soil A Soil B** 

The initial characteristics of the collected soil samples are presented in Table 1. Both soils were

Soil type Coarse-graded, sandy soil Coarse-graded, sandy soil pH 6.65 5.32 Conductivity (mS/cm) 1.12 0.98 Water content (%) 13.7 12.9 Specific gravity 2.98 3.07 Organic content (% by weight) 2.78 4.94 Lead concentration (mg/kg of soil) 0.245 0.234 Nickel concentration (mg/kg of soil) 0.201 0.267

The remediation monitoring of lead and nickel using chemically synthesized nZVI particles is presented in Figure 3, where the residual lead and nickel concentration at the dosage of 0.1 g of

nanoparticle/kg of soil added to each contaminated soil sample (A and B) is presented.
