Efficient Disposal of Basic Fuchsin Dye from Aqueous Media Using ZrO₂/MgMn₂O₄/Mg(Mg_0.333Mn_1.333)O₄ as a Novel and Facilely Synthesized Nanocomposite

Abstract

In this work, amorphous and crystalline novel products based on Zr, Mg, and Mn were facilely fabricated through the Pechini sol–gel procedure using inexpensive chemicals and an uncomplicated apparatus. Also, these products showed high efficiency as novel adsorbents in getting rid of basic fuchsin dye from aqueous solutions. The adsorbent, which was fabricated before calcination, was abbreviated as KE. In addition, the adsorbents, which were created at 500 and 700 °C, were designated as KE500 and KE700, respectively. The created adsorbents were characterized using high-level transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), N₂ adsorption/desorption analyzer, and field emission scanning electron microscope (FE-SEM). The XRD showed that the KE adsorbent is amorphous, whereas the KE500 and KE700 adsorbents are mixtures of ZrO₂, MgMn₂O₄, and Mg(Mg_0.333Mn_1.333)O₄ nanostructures. The HR-TEM exhibited that the KE adsorbent consists of very fine irregular shapes, whereas the KE500 adsorbent contains quasi-spherical particles with a mean diameter of 45.16 nm. Furthermore, the HR-TEM exhibited that the KE700 adsorbent consists of polyhedral shapes with a mean diameter of 76.28 nm. Furthermore, the BET surface area of the KE, KE500, and KE700 adsorbents is 67.85, 20.15, and 13.60 m²/g, respectively. Additionally, the elimination of basic fuchsin dye by the KE, KE500, and KE700 adsorbents is exothermic, physical in nature, and follows the pseudo-first-order as well as Langmuir equations. Further, the maximum uptake capabilities of the KE, KE500, and KE700 adsorbents toward basic fuchsin dye are 239.81, 174.83, and 93.19 mg/g, respectively.

1. Introduction

In recent years, people have complained about the scarcity of natural water resources, prompting experts to seek out secure alternatives. Some industries, such as textiles, paints, and pigments, utilize large quantities of water. These large quantities of dye-bearing water are dispersed into the environment in one way or another, leading to environmental contamination and the spread of numerous diseases among the local population [1,2,3,4,5]. Utilizing advanced oxidation processes, photocatalytic degradation, membrane filtration, enzyme degradation, coagulation/flocculation, and adsorption techniques [6,7,8,9,10,11,12,13,14,15], organic dyes have been decontaminated. Among these approaches, the adsorption technique was widely utilized as a cost-effective and simple procedure for water remediation [16,17,18,19,20,21]. Basic fuchsin dye (BFD), also known as basic violet 14, is a cationic dye exploited to color textile, leather, and silk products. Moreover, it is anesthetic, fungicidal, and bactericidal. It is non-biodegradable and toxic, and hence this dye causes environmental pollution when discharged into water [22]. Khan et al. synthesized iron-manganese-oxide-coated kaolinite for the removal of BFD dye, where the uptake capability was 10.36 mg/g [23]. Ai et al. synthesized an activated carbon/ferrospinel composite for the removal of BFD dye, where the uptake capability was 101mg/g [24]. Hinojosa-Reyes et al. synthesized hydrogen titanate nanotubes for the elimination of BFD dye, where the uptake capability was 183.2 mg/g [25]. Apostol et al. synthesized adsorbent based on xanthan and a ferrite/lignin hybrid for the removal of BFD dye, where the uptake capability was 33.33 mg/g [26]. Nanomaterials, such as zinc oxide, aluminum oxide, Fe₃O₄, and MgO, are highly efficient in removing pollutants owing to their small crystal size and great BET surface area [27,28,29,30]. The Pechini sol–gel method has succeeded in obtaining many nanomaterials such as Li₂B₄O₇/NiO/Ni₃(BO₃)₂ nanocomposites, SiO₂, MgO, Cu₂O/Li₃BO₃ nanocomposites, Fe₂O₃, and MgO/Y₂O₃ [31,32,33,34,35]. In this method, chelates are formed between cations and hydroxycarboxylic acids, such as citric acid. After that, esterification occurs through the interaction of the carboxylic group of citric acid with the hydroxyl group of ethylene glycol to produce a three-dimensional network. Moreover, the solvent is evaporated, and the resulting gel is calcinated at a moderate temperature to get rid of the organic part and obtain nanomaterials [16]. So, in the present work, amorphous and crystalline novel adsorbents based on Zr, Mg, and Mn were facilely created using the Pechini sol–gel procedure for the efficient disposal of basic fuchsin dye from aqueous solutions. The effects of pH, contact time, temperature, and initial basic fuchsin dye concentration were also investigated. The synthesis of the ZrO₂/MgMn₂O₄/Mg(Mg_0.333Mn_1.333)O₄ nanocomposite presents numerous benefits, positioning it as a highly promising option for water treatment applications. Through the strategic integration of these three constituents, a cooperative phenomenon arises that amplifies the nanocomposite’s overall functionality. The inclusion of ZrO₂, MgMn₂O₄, and Mg(Mg_0.333Mn_1.333)O₄ within the nanocomposite structure results in an increased availability of active sites for adsorption. This amalgamation leads to an elevated adsorption capacity, consequently enabling a more effective extraction of basic fuchsin dye from aqueous environments. The collaborative influence among these elements serves to augment the comprehensive adsorption performance of the nanocomposite.

2. Experimental

2.1. Chemicals

Zirconyl chloride octahydrate (ZrOCl₂·8H₂O), sodium hydroxide (NaOH), manganese(II) acetate tetrahydrate (Mn(CH₃COO)₂·4H₂O), citric acid (C₆H₈O₇), magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O), hydrochloric acid (HCl), potassium chloride (KCl), ethylene glycol (C₂H₆O₂), and basic fuchsin dye (C₂₀H₁₉N₃·HCl) were of high purity (analytical grade) and acquired from Sigma Aldrich, then utilized without undergoing any purification processes.

2.2. Synthesis of Zr/Mg/Mn/O Adsorbents

In total, 10.00 g of ZrOCl₂·8H₂O was dissolved in about 50 mL of deionized water. Also, 7.61 g of Mn(CH₃COO)₂·4H₂O was dissolved in about 50 mL of deionized water. Moreover, 7.96 g of Mg(NO₃)₂·6H₂O was also dissolved in about 50 mL of deionized water. The three metallic solutions were then combined and magnetically agitated at 550 rpm for 15 min. Moreover, the citric acid solution, which was freshly prepared through dissolving 17.89 g of citric acid in about 50 mL of deionized water, was slowly added and then the produced mixture was subjected to magnetic stirring at 550 rpm for 15 min. Furthermore, 12 mL of ethylene glycol was slowly added, and then the produced mixture was subjected to magnetic stirring at 550 rpm at 150 °C till dryness. Additionally, the generated powder was then calcined in a muffle at 500 and 700 °C for 5 h. The samples that were obtained at 500 and 700 °C were designated as KE500 and KE700, respectively. In addition, the sample that was obtained before calcination was abbreviated as KE.

2.3. Characterization of the Synthesized Adsorbents

Patterns of X-ray diffraction (XRD) of the KE, KE500, and KE700 samples were obtained at room temperature, applying a Bruker D8 Advance diffractometer (Billerica, MA, United States) with CuK_α radiation (wavelength = 1.54 Å), a step rate of 0.4 1/min, and a 2Ɵ range of 5°–70°. A field emission scanning electron microscope (FE-SEM) of the JSM-IT800 Schottky model (Akishima, Tokyo, Japan) with coupled energy dispersive X-ray spectroscopy (EDS) was used to acquire images of the surface morphology of the KE, KE500, and KE700 products as well as qualitative and quantitative information on the composition of the synthesized samples. A transmission electron microscope (TEM, Model: Talos F200iS, Waltham, MA, United States) was used to acquire images of the particle morphology of the KE, KE500, and KE700 samples. Through applying a BET surface area analyzer (Quantachrome, Model: TouchWin, Boynton Beach, FL, United States), the pore features in addition to the BET surface areas of the KE, KE500, and KE700 samples were determined.

2.4. Removal of BFD Dye from Aqueous Solutions

For investigating the influence of solution pH in the range of 2.5–8.5, batch removal experiments were accomplished by shaking 50 mg of KE, KE500, or KE700 samples with 100 mL of about 200 mg/L aqueous BFD solution for 180 min. After that, the adsorbent was retracted from the mixture by centrifugation for 3 min at 3500 rpm. After centrifugation, the yielded filtrate was examined at 544 nm, applying a UV–Vis spectrophotometer (Model: Shimadzu 1800) to estimate the equilibrium BFD dye concentration. In addition, the influences of interaction time (5–40 min), interaction temperature (298–328 kelvin), and primary BFD concentration (150–300 mg/L) were also investigated.

The uptake capability of the KE, KE500, and KE700 adsorbents (U, mg/g) and the uptake efficacy of BFD dye (% R) were calculated by applying Equations (2) and (1), respectively [36].

$$\% R=\frac{E_o-E_e}{E_o}\times 100$$

(1)

$$U=\left(E_o-E_e\right)\times \frac{V}{W}$$

(2)

E_o and E_e are the original and equilibrium BFD dye concentrations (mg/L), respectively. In addition, W and V are the quantity of adsorbent sample (g) and the volume of BFD dye solution (L), respectively.

The procedure described by Khalifa et al. [12] was employed to determine the point of zero charge (pH_PZC) for the KE, KE500, and KE700 adsorbents. The process involved introducing 0.20 g of either KE, KE500, or KE700 adsorbents into separate 0.05 L solutions of 0.026 M KCl. Additionally, the initial pH (pH_Initial) of the utilized KCl solutions was systematically adapted within the 2.50–11.50 range. Each mixture of adsorbent and KCl was continuously stirred for 6 hrs. Subsequently, the resulting pH values (pH_Final) were ascertained and plotted against their corresponding initial pH values (pH_Initial). The pH_Final value corresponding to the point on the plot where a clear plateau emerged was designated as the pH_pzc.

3. Results and Discussion

3.1. Characterization of the Fabricated Products

3.1.1. XRD

Figure 1A–C illustrates the XRD patterns of the KE, KE500, and KE700 samples, respectively. Additionally, the obtained results exhibited that the KE product is amorphous due to the broad peaks at 2Ɵ = 28° and 50°. In addition, the KE500 and KE700 samples consist of zirconium oxide (ZrO₂), magnesium manganese oxide (MgMn₂O₄), and magnesium manganese oxide (Mg(Mg_0.333Mn_1.333)O₄)), as obtained from JCPDS Nos. 00-065-0729, 00-023-0392, and 00-062-0483, respectively. The crystal system, space group, and lattice volume of ZrO₂ are tetragonal, P42/nmc (137), and 67.12 ų, respectively. Also, the crystal system, space group, and lattice volume of MgMn₂O₄ are tetragonal, I41/amd (141), and 306.64 ų, respectively. Moreover, the crystal system, space group, and lattice volume of Mg(Mg_0.333Mn_1.333)O₄ are cubic, Fd-3m (227), and 570.20 ų, respectively. The peaks at 2Ɵ = 30.45°, 35.47°, 50.91°, and 60.45° correspond to the (101), (110), (200), and (211) miller planes of ZrO₂, respectively. The peaks at 2Ɵ = 18.29°, 32.71°, 38.70°, 44.72°, 60.54°, and 65.11° correspond to the (101), (103), (004), (220), (224), and (400) miller planes of MgMn₂O₄, respectively. The peaks at 2Ɵ = 43.77°, 57.54°, and 63.12° correspond to the (400), (511), and (440) miller planes of Mg(Mg_0.333Mn_1.333)O₄, respectively. The average crystallite size, which was estimated using the Scherrer equation, of the KE500 and KE700 samples was 38.27 and 70.45 nm, respectively.

3.1.2. EDS

Figure 2A–C illustrates the EDS patterns of the KE, KE500, and KE700 products, respectively. Furthermore, the obtained findings exhibited that the KE and KE500 products are composed of C, Mg, Zr, Mn, and O, as revealed in

Table 1. Elements and their percentages in the KE, KE500, and KE700 samples.

Samples	% C	% O	% Mg	% Mn	% Zr
KE	36.25	28.47	4.70	11.78	18.80
KE500	33.96	23.84	5.98	13.77	22.45
KE700	----	18.22	9.28	14.14	58.36

. Moreover, the presence of carbon in those samples was due to the incomplete burning of citric acid. In addition, the KE700 sample was composed of Mg, Zr, Mn, and O, as revealed in Table 1. Therefore, 700 °C was sufficient to make the citric acid burn completely.

3.1.3. FE-SEM and HR-TEM

Figure 3A–C illustrates the FE-SEM pictures of the KE, KE500, and KE700 samples, respectively. Additionally, the findings exhibited that the KE product consists of very fine irregular shapes. In addition, the KE500 product contains quasi-spherical particles with a mean grain size of 90.26 nm. Further, the KE700 product is composed of polyhedral shapes with a mean grain size of 650 nm. Figure 4A–C represents the high-resolution transmission electron microscopy (HR-TEM) pictures of the KE, KE500, and KE700 products, respectively. In addition, the findings exhibited that the KE product consists of very fine irregular shapes. Additionally, the KE500 product contains quasi-spherical particles with a mean diameter of 45.16 nm. Furthermore, the KE700 product consists of polyhedral shapes with a mean diameter of 76.28 nm.

3.1.4. Nitrogen Adsorption/Desorption

Figure 5A–C illustrates the nitrogen adsorption/desorption curves of the KE, KE500, and KE700 products, respectively. Furthermore, the obtained findings confirmed that the isotherms correspond to the IV-type isotherm, which shows the mesoporous nature of the products [16]. The surface textures, for example, BET surface area, average pore size, and total pore volume, are listed in

Table 2. Surface characteristics of the KE, KE500, and KE700 products.

Sample	BET Surface Area (m2/g)	Total Pore Volume (cc/g)	Average Pore Size (nm)
KE	67.85	0.1077	3.17
KE500	20.15	0.0265	2.63
KE700	13.60	0.0305	4.49

. It was found that the BET surface area rises according to the following order, KE > KE500 > KE700, owing to the inverse relationship between surface area and crystalline size.

3.2. Removal of BFD Dye from Aqueous Media

3.2.1. Effect of pH

Figure 6A,B illustrates the effect of solution pH on the uptake efficacy of BFD dye as well as the uptake capability of the KE, KE500, and KE700 products, respectively. It was observed that the uptake efficacy of BFD dye and the uptake capability of the KE, KE500, and KE700 products increased with rising pH from 2.50 to 8.50. The uptake efficacy of BFD dye using the KE, KE500, and KE700 adsorbents at pH 8.5 is 56.36, 38.82, and 19.84%, respectively. In addition, the uptake capability of the KE, KE500, and KE700 adsorbents at pH 8.5 is 225.42, 155.26, and 79.36 mg/g, respectively.

To clarify the adsorption process, the KE sample was photographed (as an illustrative example) before and after adsorption at pH 8, as shown in Figure 7. As is clear from the figure, the color intensity decreased significantly after adsorption.

In addition, the point of zero charge (pH_PZC) of the KE, KE500, and KE700 products is represented in Figure 8. The point of zero charge (pH_PZC) of the KE, KE500, and KE700 adsorbents is 5.10, 5.31, and 5.60, respectively. If pH < pH_PZC, the medium works to surround the surface of the KE, KE500, and KE700 adsorbents with positive hydrogen ions that are repellent with positively charged BFD dye, as displayed in Scheme 1, and hence reduce the uptake efficacy and uptake capability [16]. If pH > pH_PZC, the medium works to surround the surface of the KE, KE500, and KE700 adsorbents with negative hydroxide ions that attract the positively charged BFD dye, as displayed in Scheme 1, and hence enhance the uptake efficacy and uptake capability [16].

In order to study the stability of the KE, KE500, and KE700 samples at different pH values (2.5–8.5), the XRD of the synthesized adsorbents was carried out at these pH values (figures omitted for brevity). The results showed that there is no difference in the intensity or locations of the XRD peaks, which confirms their stability. Additionally, the inductively coupled plasma analysis revealed that there is no release of ions from the KE, KE500, or KE700 adsorbents into the filtrate while undergoing adsorption. As a result, the safety of the synthesized adsorbents is established, allowing their application in water pollution treatment.

3.2.2. Effect of Interaction Time

Figure 9A,B illustrates the influence of interaction time on the uptake efficacy of basic fuchsin dye as well as the uptake capability of the KE, KE500, and KE700 products, respectively. It was observed that the uptake efficacy of basic fuchsin dye and the uptake capability of the KE, KE500, and KE700 products increased with rising interaction time from 5 to 30 min. In addition, stability was observed in these parameters when the time was increased from 30 to 40 min due to the saturation of the adsorption sites. The uptake efficacy of basic fuchsin dye using the KE, KE500, and KE700 adsorbents after 30 min was 57.36, 39.88, and 19.24%, respectively. In addition, the uptake capability of the KE, KE500, and KE700 adsorbents after 30 min was 229.44, 159.50, and 76.96 mg/g, respectively.

The pseudo-second-order (Equation (4)) and the pseudo-first-order (Equation (3)) kinetic models [16] were operated to study the linear fitting of the obtained experimental results owing to the elimination of BFD dye using the KE, KE500, and KE700 adsorbents, as displayed in Figure 10A,B, respectively.

$$\log \left(U_e-U_t\right)=log{U}_e-\frac{k_1}{2.303}t$$

(3)

$$\frac{t}{U_t}=\frac{1}{k_2{U}_e^2}+\frac{1}{U_e}t$$

(4)

where k₁ is the pseudo-first-order rate constant (1/min), U_t is the amount of BFD dye adsorbed at time t (mg/g), k₂ is the pseudo-second-order rate constant (g/mg.min), and U_e is the quantity of BFD dye adsorbed at equilibrium (mg/g). The resulting constants and the correlation coefficients (R²) are displayed in

Table 3. Kinetic constants for the disposal of BFD dye by the KE, KE500, and KE700 adsorbents.

Adsorbent	Pseudo-First-Order			Pseudo-Second-Order
	k1 (1/min)	Ue (mg/g)	R2	k2 (g/mg.min)	Ue (mg/g)	R2
KE	0.0685	222.36	0.9996	0.00018	323.62	0.9989
KE500	0.1192	159.33	0.9999	0.00052	209.64	0.9956
KE700	0.0431	78.79	0.9994	0.00014	147.71	0.9945

. In addition, the removal of BFD dye using the KE, KE500, and KE700 products obeys the pseudo-first-order due to the following reasons: (1) The R² values for the pseudo-first-order exhibit greater values compared to the R² values for the pseudo-second-order. (2) The calculated U_e values from the pseudo-first-order closely align with the experimental U_e values.

3.2.3. Effect of Interaction Temperature

Figure 11A,B illustrate the impact of interaction temperature on the uptake efficacy of BFD dye as well as the uptake capability of the KE, KE500, and KE700 products, respectively. It was observed that the uptake efficacy of BFD dye and the uptake capability of the KE, KE500, and KE700 products decreased with rising temperatures from 298 to 328 kelvin. The uptake efficacy of BFD dye using the KE, KE500, and KE700 adsorbents at 328 kelvin is 44.33, 23.52, and 13.55%, respectively. In addition, the uptake capability of the KE, KE500, and KE700 adsorbents at 328 kelvin is 177.30, 94.08, and 54.18 mg/g, respectively.

The impact of solution temperature on the elimination of BFD dye by the KE, KE500, and KE700 adsorbents was investigated by exploiting the thermodynamic constants, for instance, ∆G° (change in free energy, kJ/mol), ∆H° (change in enthalpy, kJ/mol), and ∆S° (change in entropy, kJ/mol kelvin) which were estimated using Equations (5)–(7) [16].

$$\ln K_T=\frac{△S^{°}}{R}-\frac{△H^{°}}{RT}$$

(5)

$$△G^{°}=△H^{°}-T△S^{°}$$

(6)

$$K_T=\frac{U_e}{E_e}$$

(7)

where R is the universal gas constant (kJ/mol kelvin). T is the absolute temperature (kelvin). K_T is the distribution constant (L/g). In addition, the linear alteration of lnK_T versus 1/T is displayed in Figure 12, and the thermodynamic constants can be estimated from the intercept and slope. Additionally, the thermodynamic constants for the elimination of BFD dye using the KE, KE500, and KE700 products are displayed in

Table 4. The thermodynamic constants for the elimination of BFD dye by the KE, KE500, and KE700 products.

Adsorbent	∆H° (kJ/mol)	∆S° (kJ/mol Kelvin)	∆G° (kJ/mol)
			298	308	318	328
KE	−14.20	0.0394	−25.94	−26.34	−26.73	−27.12
KE500	−20.66	0.0669	−40.62	−41.29	−41.96	−42.63
KE700	−11.47	0.0445	−24.73	−25.17	−25.62	−26.06

. Negative ∆G° values suggested that the elimination of BFD dye by the KE, KE500, and KE700 products is spontaneous. Also, the negative ∆H° values suggested that the elimination of BFD dye by the KE, KE500, and KE700 products is exothermic. Additionally, the positive ∆S° values suggested that the elimination of BFD dye by the KE, KE500, and KE700 products was conducted in the direction of growing system randomness. Moreover, the elimination of BFD dye by the KE, KE500, and KE700 products is physical in nature because the ∆H° values are smaller than 40 kJ/mol [16].

3.2.4. Effect of BFD Dye Concentration

Figure 13A,B illustrate the impact of the original dye concentration on the uptake efficacy of BFD dye in addition to the uptake capability of the KE, KE500, and KE700 products, respectively. It was found that the uptake efficacy of BFD dye decreased, whereas the uptake capability of the KE, KE500, and KE700 adsorbents increased with increasing initial dye concentrations.

The Langmuir (Equation (5)) in addition to the Freundlich (Equation (6)) equilibrium equations [16,37,38,39,40] were operated to study the linear fitting of the obtained experimental data owing to the disposal of BFD dye by the KE, KE500, and KE700 products, as displayed in Figure 14A,B, respectively.

$$\frac{E_e}{U_e}=\frac{1}{k_3{U}_{max}}+\frac{E_e}{U_{max}}$$

(8)

$$\ln U_e=\ln k_4+\frac{1}{x}\ln E_e$$

(9)

where 1/x represents the heterogeneity constant. k₃ represents the equilibrium constant of the Langmuir isotherm (L/mg). Furthermore, k₄ represents the equilibrium constant of the Freundlich isotherm (mg/g) (L/mg)^1/n. U_max represents the maximum uptake capability of the Langmuir isotherm (mg/g). Further, Equation (7) can be used for determining the U_max from the applied Freundlich equilibrium isotherm [16].

$$U_{max}=k_4\left(E_o^{1/x}\right)$$

(10)

The resulting constants and the correlation coefficients (R²) are displayed in

Table 5. The obtained equilibrium constants of the disposal of BFD dye by the KE, KE500, and KE700 products.

Langmuir Isotherm				Freundlich Isotherm
Adsorbent	Umax (mg/g)	k3 (L/mg)	R2	Umax (mg/g)	k4 (mg/g) (L/mg)1/n	R2
KE	239.81	0.3064	0.9999	236.49	196.81	0.9979
KE500	174.83	0.0917	0.9996	165.81	110.75	0.9944
KE700	93.19	0.0311	0.9966	79.84	36.53	0.9495

. In addition, the disposal of BFD dye by the KE, KE500, and KE700 products obeys the Langmuir equation because the R² values of the Langmuir equation are higher than the R² values of the Freundlich equation. Additionally, the maximum uptake capability of the KE, KE500, and KE700 products towards BFD dye is 239.81, 174.83, and 93.19 mg/g, respectively.

Furthermore, the uptake capability of the KE, KE500, and KE700 samples for adsorbing BFD dye surpassed that of other adsorbents, as evidenced in

Table 6. Comparison study between maximum adsorption capabilities of the fabricated adsorbents and those of other adsorbents in the literature for the disposal of BFD dye by the KE, KE500, and KE700 adsorbents [23,24,25,26].

Adsorbent	Maximum Uptake Capability (mg/g)	Ref
Iron-manganese-oxide-coated kaolinite	10.36	[23]
Activated carbon/ferrospinel composite	101.00	[24]
Hydrogen titanate nanotubes	183.20	[25]
Xanthan/ferrite/lignin hybrid	33.33	[26]
KE	239.81	This study
KE500	174.83	This study
KE700	93.19	This study

. The utilization of ZrO₂/MgMn₂O₄/Mg(Mg_0.333Mn_1.333)O₄ as an adsorbent offers several advantages. The combination of these components creates a synergistic influence that increases the overall adsorption operation. This nanocomposite configuration imparts a larger number of active uptake positions, leading to increased uptake capability. Consequently, this composite exhibits a heightened efficiency in removing basic fuchsin dye from aqueous media. The strategic integration of ZrO₂, MgMn₂O₄, and Mg(Mg_0.333Mn_1.333)O₄ enhances the adsorption potential, making it an excellent choice for water pollution treatment applications.

3.2.5. Impact of Desorption and Reusability

The KE, KE500, and KE700 products were renewed by exposure to stirring at 60 °C for 20 min in 50 mL of 1 M HCl, which completely removed the BFD dye from them. Afterward, the regenerated products were utilized for five repeated cycles to eliminate the BFD dye, adhering to the previously outlined experimental steps. According to Figure 15, it can be observed that the percentage of BFD dye removal using the synthesized adsorbents remained relatively stable. This suggests that these products can be employed several times without experiencing a substantial reduction in effectiveness.

4. Conclusions

Using the Pechini chemical sol–gel procedure, amorphous and crystalline novel adsorbents based on Zr, Mg, Mn, and O were facilely synthesized for the effective elimination of BFD dye from aqueous solutions. Further, the adsorbent, which was synthesized before calcination, was abbreviated as KE. Moreover, the adsorbents, which were synthesized at 500 and 700 °C, were abbreviated as KE500 and KE700, respectively. The KE adsorbent is amorphous, whereas the KE500 and KE700 adsorbents are nanostructured mixtures of ZrO₂, MgMn₂O₄, and Mg(Mg_0.333Mg_1.333)O₄. The elimination of BFD dye by the KE, KE500, and KE700 products is exothermic, physical, and follows the pseudo-first-order kinetic model and Langmuir equilibrium isotherm. Moreover, the maximum BFD dye uptake capabilities of the KE, KE500, and KE700 adsorbents are 239.81, 174.83, and 93.19 mg/g, respectively.