*3.1. Zero Valant Fe–Cu/Alg–LS Nanocomposites Characteristics* 3.1.1. FTIR Study

Figure 1 shows the Fe–Cu/Alg–LS nanocomposites' Fourier-transform infrared spectra before and after CIP and LEV adsorption. A specific band that was associated with O-H (hydroxyl) groups appeared at about 3440 cm<sup>−</sup>1. The peaks observed at 1334 and 1081 cm−<sup>1</sup> suggest the existence of OH bending and C-O stretching vibrations [30]. At 1774 cm<sup>−</sup>1, two additional peaks can be seen that are associated to the stretching vibration of C=O seen in carboxylic and/or carbonyl moiety groups [31]. Additionally, a peak at 700 cm−<sup>1</sup> that was correspond to C-H out-of-plane bending in benzene derivatives [32] was observed. As demonstrated in Figure 1B, in Fe–Cu/Alg–LS loaded CIP, After the adsorption, numerous functional groups adjusted to different bands, it was noticed that the bands at 3430, 1776, 881, 700 and 416 cm−<sup>1</sup> shifted to 3428,1774, 879, 696 and 420 cm<sup>−</sup>1, respectively. Moreover, after adsorption of levofloxacin (LEV) the bands at 3430, 1776, 1384, 881, 700 and 416 cm−<sup>1</sup> shifted to at 3482, 1774, 1382, 856 and 422 cm−1, respectively. Shifting the bands can explain the presence of H-bonded OH in the adsorption of CIP and LEV on Fe–Cu/Alg–LS nanocomposites.

**Figure 1.** FTIR spectra of (**A**) the Fe–Cu/Alg–LS nanocomposite, (**B**) Fe–Cu/Alg–LS—loaded CIP, (**C**) Fe–Cu/Alg–LS—loaded LEV.

#### 3.1.2. XRD Study

Spectra were analyzed for the phase purity of the Fe–Cu/Alg–LS nanocomposite as shown in Figure 2. The characteristic diffraction peaks located at 43.7◦ (111) indicated formation of Cu nanocrystals [33]. The diffraction peak observed at 2θ = 44.77◦ are indexed to (101) denoted the crystalline phase for Fe nanoparticles [34]. The peaks at 29.4 and 47.1◦ indicated the presence of calcite [35]. The results reveal the formation of copper, ferric and calcite that guarantees the good synthesis of the Fe–Cu/Alg–LS nanocomposites.

#### 3.1.3. SEM and EDX Study

Figure 3 shows the SEM analysis of the generated. Fe–Cu/Alg–LS nanocomposites both before and after the adsorption of ciprofloxacin (CIP) and levofloxacin (LEV). Figure 3 provides SEM images (A–D). The micrographs display rough surfaces, many holes, and nanoparticles dispersed throughout the sample. The surface exhibits an uneven surface overall for the adsorption of the designated antibiotics. Figure 3A's surface morphologies showed more pores than Figure 3B,C, indicating that the nanocomposite has enough space for the adsorption process to take place. According to Figure 3B,C, the nanocomposite had less pores due to the CIP and LEV that cover the composite.

**Figure 2.** XRD of the Fe–Cu/Alg–LS nanocomposite.

**Figure 3.** SEM of (**A**) Fe–Cu/Alg–LS nanocomposite, (**B**) Fe–Cu/Alg–LS—loaded CIP, (**C**) Fe–Cu/Alg– LS—loaded LEV.

The EDX analysis of Fe–Cu/Alg–LS nanocomposites are shown in Figure 4. The EDX analysis of the Fe–Cu/Alg–LS nanocomposites before adsorption reveals the peaks corresponding to oxygen, carbon, cupper, ferric and calcium elements. Thus, EDX guarantees the good synthesis of the Fe–Cu/Alg–LS nanocomposites.

3.1.4. Transmission Electron Microscopy Study

The TEM and particular area electron diffraction images of the Fe–Cu/Alg–LS nanocomposite is provided in Figure 5. From TEM micrographs, it is clear that the constructed Fe–Cu/Alg–LS nanocomposite exhibited a multilayer structure. This rough surface indicates that nucleation occurred. As seen in Figure 5A, the sample's microstructure and porosity are well suited for enhanced absorption. The wide range in particle size was shown in a histogram of the particle size distribution generated from the TEM images. The particles have an average diameter of 45.54 nm and range in size from 40 to 50 nm.

(**A**)

**Figure 5.** *Cont.*

**Figure 5.** (**A**) TEM analysis of the ZVFe–Cu/Alg–LS nanocomposite (**B**) particle size distribution for ZVFe–Cu/Alg–LS nanocomposite (**C**) Adsorption–desorption nitrogen isotherms.

#### 3.1.5. BET Adsorption—Desorption Measurements

The surface area and porous structure were examined with N2 adsorption–desorption tests. The N2 adsorption–desorption isotherms curve of the as-prepared aerogels obtained at 77 K are shown in Figure 5C. Figure 5C reveals a type-IV isotherm for the as-prepared samples calcined at different temperatures, indicating the existence of a mesoporous structure. The surface area data showed that the pore volume and surface area of the Fe– Cu/Alg–LS nanocomposite were 0.04432 cm3 g−<sup>1</sup> and 21.05 m<sup>2</sup> g<sup>−</sup>1, respectively, as listed in Table 2.

**Table 2.** The pore size distribution adsorption results (surface area, pore volume and average pore radius).


#### *3.2. Performance of the Fe–Cu/Alg–LS Nanocomposite*

#### 3.2.1. Effect of pH

An extremely significant factor that affects the removal efficiency of an adsorbent in wastewater treatment is the pH of the solution since the adsorption efficiency is influenced by the pH of the medium. CIP and LEV adsorption was adjusted to make the solution acidic, neutral, and alkaline (2–10). According to Figure 6A, the maximum CIP and LEV removal was obtained at pH 6 and 7, respectively. It is well recognized that the solubility of CIP and LEV is a function of pH, which is explained by the presence of different CIP and LEV chemical species at the different pH values. At low pH values, a highly soluble CIP+ and LEV+ species occurs and its fraction value decreases as pH values move from 2 to 7, where the pKa constant value (carboxylic acid group) is located [36]. Finally, as the pH value continues to increase to higher than 7, CIP+ and LEV<sup>+</sup> becomes more soluble because of the appearance of the CIP− and LEV- species [37,38]. This behavior can be described through the relationship between CIP and LEV total charge and the surface charge of the Fe–Cu/Alg–LS nanocomposite. As the pH increases up to 6 and 7, the cationic form (CIP+ and LEV+) is present, the negative Fe–Cu/Alg–LS nanocomposite surface will perform a significant adsorption of the pollutant. Moreover, the high efficiency may be attributed to the increase of adsorbent surface area and greater availability of adsorption active sites. The removal efficiency decreases significantly after the initial pH value reaches 7. This performance can be associated with the presence of the anionic

CIP and LEV form (CIP− and LEV−), which can produce repulsive interactions with the Fe–Cu/Alg–LS nanocomposite negative surface [39].

**Figure 6.** Influences of (**A**) pH, (**B**) contact time and (**C**) initial (CIP and LEV) concentration on the adsorption of CIP and LEV by 0.2 g/25 mL of the nanocomposite at pH 6 (CIP) 7 (LEV) and a contact time of (40 min (CIP) 45 min (LEV)).

#### 3.2.2. Contact Time Effect

Contact time is one of the important influences in the adsorption of the CIP and LEV onto the Fe–Cu/Alg–LS. The effect of contact time on CIP and LEV adsorption on the Fe–Cu/Alg–LS nanocomposite at concentrations of 20 ppm (CIP),10 ppm (LEV) using 0.2 g/25 mL of the nanocomposite and pH 6 (CIP) and 7 (LEV) is presented in Figure 6B. The results illustrate that in CIP and LEV removal efficiency increased to 97.3% and 100% with time. Furthermore, Figure 6B exhibited that the adsorption rate was quick in the first period of time and moderate after 40 min. This may be qualified to the accessibility of abundant free active sites on Fe–Cu/Alg–LS at the initial adsorption stage for CIP and LEV sorption. The rate became very slow after 40 min, and no appreciable CIP and LEV removal was achieved. Hence, equilibrium was reached at about 40 min for CIP and 45 min for LEV. The number of existing active sites reduced with time, and eventually, the adsorbent becomes saturated [40,41]. Consequently, beyond the equilibrium time, no significant uptake of CIP and LEV took place as depicted in Figure 6B. This result could be ascribed to an increase in electrostatic interactions between the surfaces of adsorbents and adsorbates.

#### 3.2.3. Effect of the CIP and LEV Concentrations

Using 0.2 g/25 mL of the nanocomposite, the impact of CIP and LEV concentrations on the adsorption process was investigated at concentrations ranging from 10 to 100 ppm.

In addition, the applied pH was (6 for CIP and 7 For LEV), and a contact time of (45 min for CIP and 40 min for LEV), as shown in Figure 6C. As expected, the increase in the concentration of CIP and LEV has a negative effect on the removal efficiency. Moreover, at high concentrations of antibiotics, the adsorbent surface was saturated with pollutants which decreased the adsorption uptake. Consequently, the removal efficiency was found to be decreased from 97% to 69% for CIP and from 100% to 80% for LEV.
