A γ-Al₂O₃ and MgO/MgAl₂O₄ Fabricated via a Facile Pathway as Excellent Dye Eliminators from Water

Abstract

This study has successfully developed a practical and straightforward approach for synthesizing nanocomposites with excellent dye removal potential. The SEM inspection of γ-Al₂O₃ (γ-Al) and MgO/MgAl₂O₄ (Mg/MgAl) nanocomposite showed a mean size of 59.0 and 46.4 nm, respectively, while the TEM results show particles with an average size of 26.63 and 13.4 nm, respectively. The surface area of γ-Al and Mg/MgAl was 50.0 and 69.5 m² g⁻¹, respectively. The study of adsorbing indigo carmine (IC) sorption onto γ-Al and Mg/MgAl presented sorption capacities of 41.6 and 55.9 mg g⁻¹, respectively, and both adsorbents attained equilibrium at 90 min. The highest IC sorption onto Mg/MgAl took place at pH 6.0. It is worth mentioning that raising the IC solution’s temperature from 20 °C to 50 °C increased the q_t to 268 mg g⁻¹. The IC sorption onto γ-Al and Mg/MgAl agreed with the pseudo-second-order model, and the liquid-film diffusion controlled the IC sorption. The Mg/MgAl showed an average removal of 98.2% when tested for removing six dyes at 10 mg L⁻¹, particularly malachite green, methylene blue, fast green, methyl orange, rhodamine B, and basic fuchsin, and the removal efficiency was 93.3% when their concentration increased to 20 mg L⁻¹. The Mg/MgAl nanocomposite performed exceptionally well in natural water samples (seawater and groundwater), indicating its potential applicability in managing water contamination.

1. Introduction

Industrialization is a significant contributor to water contamination, prompting an increased focus on water quality due to its potential impact on human health [1]. Among water pollutants, organic dyes from the textile, cosmetic, paper, and leather industries are considered poisonous, mutagenic, and carcinogenic [2,3,4]. The textile, plastics, food, and other sectors worldwide produce and use about one million tons of natural and synthetic dyes annually. In addition to providing color, stains can also pose health risks [5]. Almost 15% of the global dye production is released into effluents, disrupting the aquatic food chain and contributing to the death of fish and algae, as well as the collapse of ecosystems [6]. Roughly 10,000 dyes are dumped into the water environment annually [7,8,9]. Due to the long-lasting nature of organic dyes, waste should be removed before being discharged into the environment [10,11]. Since a 1.0 ppm concentration of dyes may ruin water quality, the occurrence of dyes in water highlights a clash between industrial interests and environmental protection efforts. Indigo carmine (IC), sometimes referred to as acid blue, is the sodium salt of the chemical compound 3,3-dioxi-2,2-bis-indilyden-5,5-disulfonic acid (C16H8N2Na2O8S2, 466.36 g/mol) [12]. This compound has two sulphonate groups and four aromatic rings [13]. Textiles, cosmetics, printing, biological staining, dermatological and antibiotic agents, and poultry feed are some of the various applications for this versatile dyeing substance [14]. It has a high coloring capacity for aqueous solutions and is also believed to be highly poisonous to mammalian cells, irritating, and recalcitrant [15,16,17].

Recent years have presented humanity with the formidable task of protecting the environment from the harmful effects of dyes and other pollutants. Several diverse approaches to cleaning up liquid effluent and improving the quality of natural water resources are in use worldwide. The most common methods include photodegradation, electrocoagulation, flocculation–coagulation, ultrafiltration, and adsorption [18,19,20]. Compared with other water purification methods, adsorption stands out as the clear frontrunner due to its efficiency, scalability, low operation cost, and simplicity. When deciding on a treatment strategy, it is crucial to consider the type and quantity of contaminants present [10]. In addition to different clays, activated carbon is commonly used as an adsorbent. In recent years, a wide variety of specialized sorbents, such as metal oxides and their composites, have been widely used. Magnesium and aluminum are two metals proposed as options for wastewater treatment via adsorption and photocatalytic activities [21,22]. Due to their effectiveness, relative safety, and large surface area, nanomaterials composed of metal oxides, such as those with layered double hydroxides and hierarchical nanostructures, exhibit high adsorption capacities for eliminating heavy metals [23]. Several studies have investigated the use of magnesium oxide nanoparticles and their composites as potential agents for water filtration. To effectively remove arsenic and lead ions from water, Feng et al. [24] used a microwave-aided solvothermal approach to create an aluminum and magnesium oxide composite. Biosynthesized magnesium oxide was effectively applied to remove chromium and other contaminants from a tannery’s wastewater [25]. Waste red mud from the alumina industry was used to remove IC from aqueous solutions (pH = 4.0), showing a maximum sorption capacity of 62 mg g⁻¹ [15]. Due to its environmental friendliness, several nanomaterials based on magnesium oxides have been synthesized [26]. Therefore, this study aimed to prepare γ-Al₂O₃ (γ-Al) and MgO/MgAl₂O₄ (Mg/MgAl) as low-cost, environmentally safe adsorbents using a simple, time-conserving, and economically feasible method. The prepared γ-Al and Mg/MgAl was analyzed via SEM, TEM, BET, XRD, and FTIR. Then, the two nanomaterials were tested for removing IC as an exemplary pollutant. The solution parameters were studied, and the optimum conditions for removing IC by the prepared γ-Al and Mg/MgAl were determined.

2. Results and Discussion

2.1. Characterization of γ-Al and Mg/MgAl

The surficial morphology of the prepared nanomaterials was explored via SEM analysis. Figure 1a shows the γ-Al fabricated in ellipse-shaped particles with a 55.3–63.8 nm diameter. At the same time, the Mg/MgAl conformation appeared spherical with a size ranging from 42.3 nm to 52.4 nm (Figure 1b). Additionally, the detailed morphologies of γ-Al and Mg/MgAl were examined by applying the TEM technique. The TEM images in Figure 1c revealed that γ-Al had a size range of 13.3 and 42.9 nm. In comparison, the heterogeneously built Mg/MgAl showed a size range of 6.9 and 27.8 nm (Figure 1d). Particles created using this method were smaller than those synthesized using complex routes described in the literature. Elements of the as-synthesized γ-Al and Mg/MgAl were identified using the EDX. The γ-Al sorbent exhibits an Al:O atom percentage of 54:45 (Figure 2a), indicating a slight increase in the oxygen attributable to adsorbed moisture. Concerning the Mg/MgAl composite, the Mg:Al:O atom percentage is 46.5:15.1:37.7 (Figure 2b). The EDX mapping in Figure 3 unraveled an even Al and Mg distribution all over the mapped area, indicating the capability of producing homogenous nanocomposites via this dry synthesis method.

The surface properties of γ-Al and Mg/MgAl were studied using the N₂ adsorption-desorption technique (Figure 4a,b). According to the IUPAC classification, the curve illustrates that γ-Al and Mg/MgAl exhibit an H3-type hysteresis loop, correlated with mesoporous materials featuring cylindrical pores [27]. The surface area (SA) was calculated using the BET method, while the BJH method was used to calculate the pore volume and diameter (PV and PD). γ-Al and Mg/MgAl possessed SA of 50.03 and 69.48 m²/g, PV of 0.32 and 0.33 cm³/g, and PD values of 146.36 and 284.29 Å, respectively.

The crystallography of γ-Al and Mg/MgAl was investigated using the powder XRD technique, and the results are illustrated in Figure 4c and d, respectively. The Alumina resulted in diffraction maxima at 2θ° of 19.12 (111), 31.04 (220), 37.3 (311), 45.89 (400), 61.50 (511), and 67.12 (440) allocated to γ-Al crystal planes (JCPDS card: 010-0425) [28,29]. Furthermore, the Mg:Al (2:1) composite possessed diffraction maxima at 2θ° of 18.86, 31.65, 36.99, 42.97, 44.96, 60.05, 62.68, 65.81, 74.20, and 78.61 that matched MgAl₂O₄ crystal planes of (111), (220), (311), (400), (511), (440), (620), and (533) (PDF 020-1152) [30,31]. The peaks at 42.74 and 62.25 2θ° are allocated to the (200) and (220) planes of the cubic MgO crystal (JCPDS 87-0653) [32]. These outcomes indicated that γ-Al and Mg/MgAl were prepared successfully, and the principal peaks of MgO and MgAl₂O₄ indicated a 5:1 phase ratio.

Figure 4d illustrates chemical substances and functional groups on γ-Al and MgAl₂O₄ surfaces that were analyzed via an FTIR spectrophotometer. The broad band between 3000 and 3600 cm⁻¹ can be attributed to OH-stretching vibrations. The peak appearing at 1100 cm⁻¹ matches the Al–O vibration of γ-Al. The valley between 1000 cm⁻¹ and 435 cm⁻¹ confirms the γ-Al phase indicated by XRD analysis, while the bands at 670 cm⁻¹ and 873 cm⁻¹ are assigned to the Al-O and Al-O-Al bending vibrations of the γ-Al phase [33].

2.2. Contact Time and Kinetic Investigations

Figure 5a depicts the contact time study of IC sorption onto γ-Al and Mg/MgAl. The adsorption of IC onto γ-Al and Mg/MgAl that occurred during the first 30 min may be due to the availability of adsorption sites on the surfaces of the two adsorbents. The decrease in the adsorption rate after 30 min may be attributed to a decrease in the gradient of IC concentration and a slowing of the sorption trend [34]. The IC elimination trend by γ-Al and Mg/MgAl progressed up to 90 min (equilibrium time), yielding q_t values of 41.6 and 55.9 mg g⁻¹, respectively. These findings identified γ-Al and Mg/MgAl as viable options for removing high IC pollution, such as textile and leather industrial waste. To evaluate the IC sorption kinetics onto γ-Al and Mg/MgAl, the nonlinear pseudo-first-order (PFO) and nonlinear pseudo-second-order (PSO) (Equations (1) and (2)), respectively, were employed. Furthermore, the intraparticle diffusion (IPD) and liquid film (LFM) models (Equations (3) and (4)) were employed to investigate the sorption control mechanism [35].

$$q_t=q_e(1-{exp}^{-K_1·t})$$

(1)

$$q_t={\displaystyle \frac{k_2·q_e^2·t}{1+k_2·q_e·t}}$$

(2)

$$q_t=K_{IP}\ast t^{{\displaystyle \frac{1}{2}}}+C_i$$

(3)

$$ln(1-F)=-K_{LF}\ast t$$

(4)

where k₁ (min⁻¹), k₂ (g mg⁻¹ min⁻¹), K_IP (mg g⁻¹ min^−1/2), and K_LF (min⁻¹) denote the constants for PFO, PSO, LDM, and IDM, respectively, C_i represents the boundary layer factor in IDM [36]. The PFO and PSO rate constants are denoted as k₁ (min⁻¹) and k₂ (g mg⁻¹ min⁻¹), respectively, while the LDM and IDM constants are represented as K_LF (min⁻¹) and K_IP (mg g⁻¹ min^−0.5), respectively. The k₁ and k₂ calculations were performed using the slope and intercept derived from the PFO and PSO graphs presented in Figure 5b,c. Aside from the residual sum of squares and reduced Chi-square (RSS and X²), the best-fitting model was primarily chosen based on the correlation coefficient (R²) (

Table 1. Kinetic outcomes of IC sorption onto γ-Al and Mg/MgAl nanocomposites.

Adsorption Rate Order
Sorbent	qmax exp (mg g−1)	PFO					PSO
		qe (mg·g−1)	K1	R2	X2	RSS	qe (mg·g−1)	K2	R2	X2	RSS
γ-Al	41.57	40.022	0.064	0.988	3.110	18.661	51.755	0.064	0.996	0.952	5.714
Mg/MgAl	55.90	49.095	0.062	0.956	15.715	94.951	51.957	1.011	0.984	5.721	34.327
Adsorption Rate Mechanism
Sorbent	IDM							LDM
	KIP (mg·g−1 min1/2)		C (mg·g−1)		R2	X2	RSS	KLF (min−1)	R2	X2	RSS
γ-Al	5.531		1.404		0.963	12.448	22.361	0.074	0.978	0.067	1.0457
Mg/MgAl	2.603		35.154		0.937	13.498	8.444	0.038	0.963	0.066	1.3057

) [37]. The computed values also indicated that the PSO was more effectively corroborated by the data obtained from the IC sorption on γ-Al and Mg/MgAl, as seen by lower X² values corresponding to higher R² values. The findings indicated that γ-Al and Mg/MgAl surfaces exhibited multi-layer sorption with interactions among sorbed molecules and localized sorbent sites. Figure 5d,e illustrate the association between IDM and LDM for IC sorption onto γ-Al and Mg/MgAl. The results in Table 1 indicated that IC sorption onto the γ-Al and Mg/MgAl was governed by LDM, as demonstrated by higher R² values accompanied by decreased X² and RSS values. Another piece of evidence indicating a discrepancy in sorption with the IDM model is that both nanocomposites exhibit C_i values exceeding zero [38,39]. These results demonstrate that IC sorption was regulated by the LDM model and indicated a significant affinity of IC toward γ-Al and Mg/MgAl.

2.3. Sorption Equilibria

The temperature and initial feeding concentration are the most critical factors affecting adsorption [40]. According to the contact time results, Mg/MgAl was identified as the best sorbent. Consequently, the influence of IC concentration on the sorption by Mg/MgAl was examined (Figure 6a). The q_t grew correspondingly as the concentration escalated from 20 to 200 mg L⁻¹, indicating that a higher starting concentration can provide a powerful force that aids in the dispersion of contaminants. Raising the IC solution temperature from 293 K to 323 K significantly increased the sorption efficiency, where the q_t of 200 mg L⁻¹ of IC shifted from 130 to 268 mg g⁻¹, demonstrating that IC adsorption by Mg/MgAl was endothermic. The elevation of the solution temperature may have resulted in extensive de-agglomeration of the Mg/MgAl clusters, generating new adsorption sites through the fractionation of the agglomerates, which led to an additional increase in adsorption capacity. This characteristic is particularly significant in real-world scenarios, where temperature fluctuations occur frequently and maintaining high levels of removal efficiency is possible [41].

To better comprehend IC sorption onto Mg/MgAl, the Langmuir (LM) and the Freundlich (FM) isotherm models were examined using concentration data at 293 K. The hypothesis of single-layer sorption without sorbate-sorbate interaction was investigated using LM (Equation (5)); conversely, the multi-layer sorption potentiality was assessed by FM (Equation (6)). Ce (mg L⁻¹) is IC concentration; q_m is the maximum q_t; K_L (L.mg⁻¹) is the LM constant; K_F (L g⁻¹) and 1/n are the FM constant and favorability factor, respectively [1,39].

$$q_e=\left({\displaystyle \frac{K_l{q}_m{C}_e}{1+q_m{C}_e }}\right)$$

(5)

$$q_e=K_F·C_e^{{\displaystyle \frac{1}{n}}}$$

(6)

Figure 6b presents the aggregated LM and FM nonlinear plots of IC adsorption onto Mg/MgAl, and their outcomes are presented in

Table 2. Isotherm results of IC sorption by Mg/MgAl using concentrations ranged from 25 to 200 mgL⁻¹ at 293K, and the thermodynamic results of 25 to 200 mgL⁻¹ IC concentrations at 293, 303, 313, and 323 K.

Adsorption Isotherms
Isotherm Model →	Langmuir			Freundlich
Temperature	R2	KL (L·g−1)	qm (mg·g−1)	R2	Kf (L·g−1)	1/n (a.u)
293 K	0.997	0.012	188.774	0.956	9.446	0.502
Thermodynamic Results
Conc. (mg L−1)	ΔH°	ΔS°	ΔG° (293 K)	ΔG° (303 K)	ΔG° (313 K)	ΔG° (323 K)	R2
25.0	35.692	0.131	−2.695	−4.005	−5.315	−6.625	0.921
50.0	3.610	0.020	−2.210	−2.409	−2.608	−2.806	0.626
100.0	39.644	0.136	−0.165	−1.524	−2.883	−4.241	0.994
200.0	19.799	0.068	−0.033	−0.710	−1.387	−2.064	0.974

. The fitting results indicated that the IC sorption onto Mg/MgAl was aligned with the LM, which suggested that one gram of Mg/MgAl could potentially eliminate up to 188 mg of IC. The sub-unity value of 1/n indicated that IC sorption onto Mg/MgAl was favorable.

For a further understanding of IC removal via Mg/MgAl, the thermodynamics were investigated at 293, 303, 313, and 323 K with the preidentified concentrations. The graph of Equation (7), presented in Figure 6c, was used to calculate the entropy (ΔS°) and enthalpy (ΔH°), and then their magnitudes were plugged into Equation (8) to compute the Gibbs free energy (ΔG°), and the thermodynamic results are gathered in Table 2.

$$ln K_c= {\displaystyle \frac{\Delta H^o}{RT}} + {\displaystyle \frac{\Delta S^o}{R}}$$

(7)

$$\Delta G^o=\Delta H^o-T \Delta S^o$$

(8)

K_c (L/mg) denotes the adsorption equilibrium constant derived from the Langmuir isotherm adsorption equation; ΔG° is expressed in (kJ/mol); ΔH° is in (kJ/mol); ΔS° is in (kJ/(mol K)); R represents the universal gas constant (8.314 J/mol); and T indicates the adsorption temperature (K) [1,2].

The positive ΔH° outcomes indicated an endothermic IC sorption onto Mg/MgAl, and the removal tended to be spontaneous at all tested IC concentrations. The negative ΔG° indicates the spontaneity of the adsorption process, and the rise in the negative ΔG° values with decreasing initial concentration is promising for utilizing these sorbents in water treatment applications, particularly for low pollutant concentrations.

2.4. Effect of pH on IC Sorption by Mg/MgAl

The influence of pH on the adsorption process was analyzed, as it significantly affects the sorbent’s capacity to remove contaminants. As illustrated in Figure 7, the adsorption capacities of the adsorbent were influenced by varying the solution pH. The adsorption exhibited a gradual increase from pH = 2.0 to 6.0, ranging from 50.2 to 64.3 mg g⁻¹. Subsequently, with an increase in pH, the removal capacities declined and reached their lowest point at a pH of 10.0. The maximum adsorption occurs at pH = 6.0, suggesting that neutral or mildly acidic conditions are optimal for this process. The dispersion of Mg/MgAl water may result in the formation of M-OH-type groups through a Mg/MgAl surface reaction, and the dissociation of these M-OH groups is contingent upon the pH value. A positively charged surface M-OH²⁺ exists at acidic pH because of the high availability of H⁺ in the solution at such acidic medium. At pH ≥ 7.0, the Mg/MgAl surface exhibits a repulsion of IC molecules through its negatively charged double sulphonate groups (Figure 7b) and the negative Mg/MgAl. This case is mainly attributed to the conversion of MgO to the more stable Mg(OH)₂ form, along with the spreading of ⁻OH in the solution, which hinders the IC diffusion, competing for the limited positive sites on the Mg/MgAl surface, and consequently diminishing the IC sorption [42,43].

2.5. Application of Sorbents to Natural Water Samples

To introduce a realistic character to this study, the effectiveness of Mg/MgAl as an adsorbent for treating polluted water sources was evaluated. The natural samples of GRW and SEAW exhibited TDS values of 0.89 and 33.28 g/L, respectively; their temperatures were 24.5 °C and 25.5 °C, with corresponding pH values of 6.1 and 6.5. The natural water pH was sufficiently close to the optimal level; hence, the samples were processed as if directly sourced, incorporating a heating step (40 °C) to enhance sorption, as demonstrated by the thermodynamic data. Figure 7b reflects the Mg/MgAl efficacy in eliminating IC from GRW and SEAW. The marginal decrease in IC removal from SEAW relative to GRW can be ascribed to the heightened SEAW saline concentration, which may obstruct some active sorption sites on Mg/MgAl and/or impede the diffusion of the IC solution towards the Mg/MgAl surface.

2.6. Removal of Different Organic Dyes

The Mg/MgAl was tested for the removal of diverse dyes, including malachite green (MG), methylene blue (MEB), fast green (FGR), methyl orange (MEO), rhodamine B (RHB), and basic fuchsin (BFN). The adsorption investigation was conducted with dye concentrations of 10 and 20 mg L⁻¹, and the outcomes were depicted in Figure 7c. Treating a 10 mg L⁻¹ concentration of the preidentified pollutants, the synthesized Mg/MgAl exhibited an average removal efficiency of 98.16% with a 96.56% to 99.15% range and RSD of 1.14%. Furthermore, 20 mg L⁻¹ concentration Mg/MgAl demonstrated an average removal efficiency of 93.32%, with a range of 84.84–97.23% and an RSD of 4.4%. The obtained data indicated the validity of Mg/MgAl for treating water containing diverse dye contaminants, such as those from the textile industry.

3. Conclusions

This work has developed a practical and straightforward method for synthesizing nanocomposites with promise for reuse. The SEM analysis of γ-Al and Mg/MgAl nanocomposites revealed mean size ranges of 55.3–63.8 nm and 42.3–52.4 nm, respectively. Detailed morphologies of γ-Al and Mg/MgAl were investigated using TEM, indicating that γ-Al exhibited a size range of 13.3 to 42.9 nm, while Mg/MgAl displayed a size range of 6.9 to 27.8 nm. Their respective surface areas were 50.03 and 69.48 m²/g. The elemental composition of the synthesized γ-Al and Mg/MgAl was determined by EDX, revealing a 2:3 Al:O ratio for the γ-Al sorbent, which closely aligns with the estimated ratio for the Mg/MgAl composite. X-ray diffraction (XRD) demonstrated the purity of the nanocomposites and identified the existence of γ-Al crystal planes in both samples. A comprehensive examination was conducted to analyze IC sorption on γ-Al and Mg/MgAl, which exhibited qt values of 41.6 and 55.9 mg g⁻¹, respectively. The ideal adsorption of IC occurred within approximately 90 min, with optimal elimination observed at a pH of 6.0. The Langmuir model was optimally matched by isothermal sorption onto γ-Al and Mg/MgAl; whereas the diffusion model indicated a physisorption characteristic, with adsorption governed by pseudo-second-order kinetics. The study of thermodynamic data reveals a spontaneous endothermic IC sorption on the Mg/MgAl nanocomposite across all tested IC concentrations. The Mg/MgAl exhibited an average removal effectiveness of 98.2% for six dyes at a concentration of 10 mg L⁻¹, specifically malachite green, methylene blue, fast green, methyl orange, rhodamine B, and basic fuchsin; in comparison, the removal efficiency decreased to 93.3% at 20 mg L⁻¹ dye concentration. The Mg/MgAl nanocomposite exhibited outstanding performance in natural water samples (seawater and groundwater), suggesting its potential utility in addressing water contamination.

4. Experimental

4.1. Materials

Magnesium chloride-6-hydrate 99% (MgCl₂-6H₂O) and indigo carmine (IC) dye were provided by Fluka, Dresden, Germany. Aluminum trichloride hexahydrate (97% purity, AlCl₃·6H₂O) was purchased from LOBA CHEMIE, India. D(+)-Glucose monohydrate (GL) from Riedel-de-Haen, Hanover, Germany.

4.2. Preparation of γ-Al and Mg/MgAl

The γ-Al was prepared by milling 0.1 mol of AlCl₃·6H₂O and 0.01 mol of GL in a 50 mL stainless steel crucible using a ball mill for 30 min, with the machine operating at 300 RPM. The mixed powder was placed into a 250 mL porcelain dish and heated on a hot plate until the GL was carbonized; then, it was heated at 600 °C for 4.0 h. The Mg/MgAl was prepared similarly, except for adding 0.15 moles of MgCl₂·6H₂O to the aforementioned AlCl₃·6H₂O and GL amounts.

4.3. Characterization of γ-Al and Mg/MgAl

The prepared nanomaterials were examined using a powder X-ray diffractometer (D8 Advance, Bruker, Billerica, MA, USA), Fourier transform infrared spectroscopy (FTIR, Bruker TENSOR Series, Ettlingen, Germany), scanning electron microscopy (SEM-JSM-IT300), and a surface analyzer (ASAP 2020, Micromeritics, Norcross, GA, USA).

4.4. Adsorption of IC on γ-Al and Mg/MgAl

The IC adsorption on γ-Al and Mg/MgAl was studied by stirring (600 RPM)100 mL of a 100 mg L⁻¹ IC solution with 50 mg of sorbent in a 250 mL glass beaker. A portion of the mixture was sampled at regular time intervals, and the absorbance was determined using a Shimadzu UV-2600i spectrophotometer. The pH impact on IC sorption by γ-Al and Mg/MgAl was studied at ambient temperature using separate beakers containing a 100 mg L⁻¹ IC solution adjusted to pH values of 2 to 10. These were modified utilizing 0.1 mol L⁻¹ NaOH and 0.1 mol L⁻¹ HCl solutions. A pH meter (Hanna, Eibar, Spain) equipped with a glass pH electrode was used to measure the pH values of the solutions while stirring at 300 RPM. In summary, 100 mL of a 100 mg L⁻¹ IC solution was stirred with 50 mg of each adsorbent separately for 90 min. Aliquots were subsequently collected, filtered, and examined using a 2600i Shimadzu UV-vis spectrophotometer to ascertain the equilibrium concentration of IC at each pH level. The IC color alteration due to the pH value was taken into consideration by adjusting an extra volume of IC solution to accommodate the sample use, and the surplus was used as the standard solution. The influence of feed concentration on IC removal by γ-Al and Mg/MgAl was tested using 25, 50, 100, and 200 mg/L IC solutions, and the adsorbents were shaken with 50 mg of each individually for 90 min. Moreover, to examine the impact of temperature on IC sorption, the previous experiment was performed between 20 and 50 °C.

4.5. Application of γ-Al and Mg/MgAl to Natural Water Samples

A seawater sample (SEAW) was collected from the beach of Al-Khobar, eastern Saudi Arabia, and the groundwater (GRW) sample was taken from the industrial city north of Riyadh, Saudi Arabia. Concentrations of 5 and 10 mg L⁻¹ drug solutions were prepared in each natural water sample. For both drugs, 100 mL of each concentration was stirred with 50 mg sorbent for 1.5 h, and then the sorption efficiency was calculated.