A suspension of Na-MMT (25 g) was dispersed in 800 mL of distilled water, heated to 80°C with stirring for 2 hours, then centrifuged for 5 minutes to obtain the precipitate. After circulating the Na-MMT suspension for 2 hours, 10 g of (CTAB) were added. The precipitate was repeatedly washed with distilled water until no bromide ions were detected using 0.1N silver nitrate solution. Next, it was dried for 24 h at 60°C (Mohamed et al., 2020).

By combining several compositions that were pre-cooked, GG/PVA polymer solution combinations of diverse compositions were created using the solution casting technique (Wang and Rhim, 2015). To prevent the formation of air bubbles, 3g of guar gum (GG) was dissolved in 50°C distilled water with gentle stirring for 2 hours. In 2 hours, 2g of PVA were dissolved in distilled water at 70°C while being stirred at 1,000 rpm. After that, the guar gum solution and PVA solution were combined thoroughly and constantly stirred until total miscibility. Table 1 displays the weight percentage ratios of GG and PVA in the mixtures, which were (50/50), (60/40), and (80/20) wt%. 0.5 g of OMMT was added once the GG/PVA polymer solution was prepared. After that, 5 wt% (the total dry weight of the polymers) of glycerol was added as a plasticizer, and the mixture was vigorously stirred for 1 hour to achieve a homogenous solution. A precise volume of 20 mL of the mixture was poured into a 15 cm glass petri dish and allowed to dry in a vacuum oven for the entire night at 60°C. As indicated in Scheme 1, the films were taken out of the glass petri dish and placed in polyethylene bags to prevent contamination until needed.

After 1.0 g of copper metal (Merck, 99.99%) was solubilized in 20 mL of HNO₃ and a few drops of HCl, a freshly produced synthetic stock solution containing 1,000 mg/L of copper ions was equipped. The solution was then diluted up to 1 L using distilled water. One liter of 7M HCl was used to dissolve 1 g of cadmium metal (Merck, 99.5%) yielding a stock solution of 1,000 mg/L cadmium. The concentration of copper and cadmium ions was approximated using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES, Agilent, USA).

The FTIR spectra of GG, OMMT, GG/PVAI, GG/PVAII, and GG/PVAIII were recorded using KBr discs on Perkin-Elmer Spectrophotometer to verify the formation of GG/PVA nanocomposite film. 1H NMR shifts were identified by Mestre Nova software for peaks interpretation. The prepared nanocomposite morphology and size were determined using a highly efficient technique (TEM, JEM-200CX, JEOL, Japan), which uses a high-energy electron beam to illuminate a thin sample and then interacts with it to detect the shape, size, and density of quantum wells or wires and dots. After making the sample suspension in ethanol, it was sonicated for 20 min. Next, a copper grid was loaded with a few drops of the resultant suspension at an accelerated voltage of 200 kV to investigate the sample structure. Using a TGA apparatus, samples weighing between 0.98 and 1.5 mg were packed in aluminum pots and heated to 600°C at a rate of 10°C/min in a nitrogen-filled environment. Using a controlled dry nitrogen flow rate of 20 mL/min, TGA was carried out in the temperature range of room 600°C at a rate of 20°C/min using a Shimadzu TGA-50 system from Japan.

Cu²⁺ and Cd²⁺ ion uptake studies were carried out at regulated pH settings (1.0–7.0), with each dry nanocomposite divided into 10 mg parts and stored in separate flasks. Each flask received a 25 mL (100 mg/L) solution of either Cd²⁺ or Cu²⁺. pH was optimized using diluted HCl or NaOH solutions. The flasks were shaken on a vibromatic-384 shaker at 100 rpm for 2 hours at 25°C. Following equilibration, the metal ion residual concentration was estimated using ICP-OES and the uptake was determined using Eq. 1 (Mubark et al., 2021; Yousif et al., 2022; Mubark et al., 2023), and as follows: q = C initial − C final × Volume Weight (1) q: the uptake in mg/g, C _initial, and C _final are in mg/L, Volume is in L and Weight is in g. The standard deviation was used to calculate the averaged findings after repeating each experiment three times.

The Cu²⁺ and Cd²⁺ uptake at various sorbent dosages was assessed by rotating 10–50 mg of each adsorbent nanocomposite in different flasks. Each flask contains a 25 mL (100 mg/L) Cu²⁺ or Cd²⁺ solution with a pH of 6.0. Flasks were shaken for 2 hours at 25°C. Following adsorption, the concentration of remaining metal ions in the solution was determined. The removal efficiency values were then computed using the following equation, which represents the initial and final metal ion concentrations, respectively (Eq. 2). Efficiency of removal = C i n i t i a l   –   C final   /   C i n i t i a l × 100 % (2)

Using 10 mg of each adsorbent nanocomposite in multiple flasks containing 25 mL of Cu²⁺ or Cd²⁺, at an optimal pH (pH 6.0) and a starting concentration of 100 mg/L, the uptake of Cu²⁺ and Cd²⁺ as a function of contact time (30–360 min) was measured. At 25°C and 100 rpm, the flask and its contents were shaken. For the purpose of calculating the concentration of Cu²⁺ or Cd²⁺ residuals, 5 mL of the solution were retrieved at various periods, filtered and measures using ICP-OES. Uptake was calculated via Eq. 1 as previously described.

The stirring time parameter data were used to investigate the adsorption kinetics of the three produced GG nanocomposites for the metal ions under study. This was carried out by applying the results using kinetic models equations, namely,; pseudo-1^st-order, pseudo-2^nd-order.

The two models were represented as follows in Eqs. (3, 4) (Weber and Morris, 1963; Ho and McKay, 2019; Eliwa and Mubark, 2021; Mubark et al., 2022a) log q e − q t = ⁡ log ⁡   q e − k 1 2.303 t (3) t q t = 1 k 2 q e 2 + 1 q e t (4) k₁ and k₂: the reaction rate constants for the pseudo-1^st-order, pseudo-2^nd-order, respectively. q_e and q_t:the amounts of Cu²⁺ and Cd²⁺ adsorbed at equilibrium and at time t, respectively.

Cu²⁺ and Cd²⁺ adsorption isotherms were derived by adding 10 mg of each adsorbent nanocomposite to a series of flasks holding 25 mL of the respective adsorbent at a specific concentration (20, 30, 40, 50, 70, and 100 mg/L) and pH 6.0 for 240 min. Temperatures were maintained at 25, 35, 45, and 55°C while the flasks were shaken at 100 rpm. The residual Cu²⁺ and Cd²⁺ concentration was measured following equilibration.

Two adsorption isotherms were utilized to explain the adsorption mechanism of both metal ions on the prepared nanocomposites, namely, Langmuir and Freundlich models. The empirical model’s equations were represented as follows in Eqs. (5, 6) C e   q e = C e Q max + 1 Q max   K L (5) log ⁡   q e = ⁡ log ⁡ K f + 1 n   log ⁡   C e (6)

Q_max, k_L, and C_e: the maximum adsorption capacity, the Langmuir constant is related to the adsorption capacity, and the metal ion concentration in solution. K_f and 1/n: the Freundlich constant related to adsorption capacity and intensity, respectively.

EDTA solutions were used to set up the desorption experiments. To remove any unabsorbed species, 10 mg of the loaded adsorbent nanocomposite containing Cu²⁺ or Cd²⁺ ions was carefully washed with distilled water. After that, the nanocomposite was shaken for 3 hours at 100 rpm and 25 °C using 25 mL of 1% EDTA. Following a mild washing with distilled water, the nanocomposite was examined to see if it could be used again in the subsequent uptake run. The following equation (Eq. 7) served as the basis for determining the tendency efficiency for the re-uptake. Regeneration efficiency  % = uptake   in   the   2 nd   run uptake   in   the   1 st   run × 100   % (7)

To investigate the applicability of the prepared nanocomposites to remove Cu²⁺ and Cd²⁺, 100 mL portions of wastewater were obtained from Nuclear Material Authority (NMA) laboratories from different laboratories. Using prepared nanocomposites, this wastewater was processed by implementing the most beneficial controlling factors influencing the adsorption of Cu²⁺ and Cd²⁺ at room temperature. According to the methodology described above, estimation of concentration of Cu²⁺ and Cd²⁺ was performed before and after treatment.

To identify the chemical bonds within a molecule, this analysis is dependent on the generation of an infrared absorption spectrum (Chen et al., 2015; Mubark et al., 2022b). The FT-IR provides a full and detailed analysis of the sample through screening and scanning it for many various components to determine its characteristic molecular fingerprint. It is also an efficient way to determine the functional groups and the covalent bond (Rohman et al., 2020).

The FTIR analysis of OMMT, GG, GG/PVAI, GG/PVAII, and GG/PVAIII was obtained in Figure 1. Bands at 2,922, 2,851, and 1,469 cm^-1 in OMMT’s Figure 1A were attributed to the stretching vibration of N-H, the symmetric stretching vibration of the C-H bond of -CH₂, and the sharp peak of C-H bending vibration absorption of CTAB, separately which verified the modification of MMT (Verma et al., 2013). The FTIR for the native GG is displayed in Figure 1B. A wide band at 3,444 cm^-1 was visible on the chart, which corresponded to -OH stretching vibrations and H₂O involved in the formation of hydrogen bonds. A tiny band was identified as the -CH stretching vibration at 2,925 cm^-1. The bands recognized in the spectrum between 800 and 1,200 cm⁻¹ represented the highly coupled C-C-O, C-OH, and C-O-C stretching modes of the backbone of the polymer. The FT-IR spectra of GG/PVA films are shown in Figures 1C–E. The chosen films that were subjected to FT-IR analysis revealed commonalities and overlaps. Furthermore, it was shown that the stretching vibration areas of the hydrogen group are connected to the strong broad band that appeared between 3,700 and 3,000 cm^-1 (Fan et al., 2012). The -OH band can undergo an FT-IR wavenumber transformation because it is extremely sensitive to hydrogen bonding. When GG/PVA film spectra are compared at 3,400 cm^-1, the sharpened and expatriate bands appeared at a higher wavenumber, indicating a shift in the glycerol and PVA content. The formation of various types of hydrogen bonds, both intra- and intermolecular, is linked to the presence of -OH groups in prepared films. The shift was therefore observed at 3,400 cm^-1 as a result of the hydrogen bonding interactions between the GG-glycerol-PVA molecules (Acharya et al., 2017). Vibration bands at 2,902 and 2,938 cm^-1 are caused by aliphatic C-H stretching from alkyl groups, and they intensify in the presence of PVA and glycerol. The vibration bands at 2,902 and 2,938 cm^-1 are mostly caused by the aliphatic C-H stretching from alkyl groups, which becomes more intense when glycerol and PVA are present.

1 H-NMR spectroscopy, which is presented in Figure 2, was also used to confirm the structures of GG/PVAI, GG/PVAII, and GG/PVAIII. A peak with δ = 1.28–1.33 ppm was observed in 1H-NMR analysis for CH2−methylene protons attached to the–O– group, and 1.88–2.2 ppm were observed for protons of (–C–O–H) alcohol substituted to GG at side wise coupled to the cyclic ring carbon. The peaks that developed between 3.50 and 3.78 ppm were caused by methylene protons that were bound to carbons in the formation of cyclic rings and had alcohol on the other side of those protons. The -CH2 protons (d), which are attached to the cyclic carbon ring attached to the side and terminal side -O-H functional group employed in grafting, are responsible for the peaks that appeared in the range of 3.88–4.15.

The characteristics of extremely small specimens are observed using TEM analysis. It is known that there are various types of nanometer-sized particles; therefore, the utilization of TEM permits obtaining information concerning the particle size, shape, and surface layers. So atomic structures can be directly imaged in solids and surfaces by TEM. It is utilized in the first place to determine the presence of prepared metal particles on a nano-scale and it is also very useful in estimating the size of the metal formed nanoparticles (Brodusch et al., 2021). The distribution of OMMT nano clay particles into GG/PVA film could be clarified by using transmission electron microscopy (TEM), shown in Figure 3. The small spherical point groups were localized by TEM, which appears to be superbly dispersed in the GG/PVA films. The image also represents some amount of collections in some regions, which may be due to the presence of a GG/PVA polymer blend responsible for the stabilization of nano clay particles as suggested by the small spherical point groups localized by TEM, and the GG/PVA films seem to have excellent dispersion. The image also shows some collections in some areas, which could be explained by the existence of a GG/PVA polymer mixture that stabilizes nano clay particles (Awadeen et al., 2020).

The effects of adding nano clay surface-modified montmorillonite to guar gum on its thermal stability were investigated using TGA analysis. The weight loss (%) over a broad temperature range of 100–600°C was used to assess the thermal stability of guar gum and montmorillonite, as illustrated in Figure 4. It was recognized that the decomposition rate was lower in the case of nanocomposite than native guar. The chemical modification of guar was detected by the presence of a three-stage decomposition mechanism and by the observation of maximal weight loss after the decomposition reaction of the first stage in the nano samples. The initial decomposition temperature (IDT), which refers to the point at which moisture or volatile compounds were lost, was between 100°C and 200°C in each case. Because of the chain elimination, the secondary stage was identified in the 300–500°C temperature range. Ultimately, the fracture of the composites’ structure at 600°C led to the determination of the third stage. In regarding thermal stability, guar gum (80/20) exceeded the other composites tested. This is owing to the existence of a higher percentage of guar gum and a lesser percentage of clay, as the latter’s high ratio has a negative impact on a specific proportion due to its collapse at high temperatures. This could be connected to the presence of guar gum at a higher ratio than MMT, which has a deleterious effect on the manufactured composites. High-temperature thermal treatment of clay minerals frequently results in the formation of new microcracks or the extension/widening of pre-existing microcracks, resulting in variations in physical attributes (Sun et al., 2016). Upon comparing with the native guar, the decomposition rate was lower in the case of composites than the native guar, which indicates the more compact and maintained polymeric network in nanocomposites. This could be a result of the polymeric network’s incorporation of nano clay, which acts as a barrier to prevent both mass and energy conveyance in the composite network.

Figure 5 shows the extent to which the three prepared nanocomposites were able to adsorb Cu²⁺ or Cd²⁺ ions from liquid solutions depending on the pH effect in non-competitive conditions. In every instance, the maximum uptake for those metal ions was found at pH 6.0. When the effectiveness of the variously prepared nanocomposites was compared, the modified nanocomposite with an 80/20 ratio demonstrated the greatest removal across the entire pH range. According to the majority of research, the pH range of 4.0–6.0 is where Cu²⁺ and Cd²⁺ adsorption results in the highest removal percentage (Fu and Wang, 2011; Carolin et al., 2017). Because protons and metal ions compete for adsorption sites, the extraction efficiency for both metal ions with the various nanocomposites was lowest at low pH. As the pH increased, the solution’s pronation decreased and uptake increased accordingly. The hydrolysis of both metal ions caused a decrease in the extraction percentages of Cu²⁺ and Cd²⁺ at pH values greater than 7.0 (Lü et al., 2013). Thus, in the following studies, pH 6.0 was selected for the removal of Cu²⁺ and Cd²⁺. The mechanism of the interaction of these metal ions with the prepared nanocomposites were expected to achieve through the interaction of the free hydroxyl groups present on the surface of the nanocomposites.

At pH 6.0, the effects of sorbent dose (sorbent dose 10–50 mg, initial metal ion concentration 100 mg/L) on the potency of Cu²⁺ and Cd²⁺ ion elimination onto the three distinct nanocomposites were explored. The data displayed in Figure 6 illustrates how increasing the sorbent dose had a positive impact on removal efficiency which was explained in terms of the quantity of more active adsorption sites for Cu²⁺ and Cd²⁺ in the nanocomposites.

Figure 7 shows the uptake measurement over a fixed time period. Over the course of 120 min, the uptake of Cd²⁺ and Cu²⁺ demonstrated high uptake capacities of roughly 60% at the plateau. Within 240 min, the equilibrium uptake capacities were reached.

To examine kinetics of the adsorption reaction, pseudo-1^st-order and pseudo-2^nd-order models were applied to the adsorption data. The pseudo-1^st-order could model the adsorption process as one component dependent, albeit the pseudo-1st-order model was being properly managed for the bimolecular process. In short, adsorbent or adsorbate amounts mastered the pseudo-1^st-order-model. In many cases, the pseudo-1^st-order-model mainly describes adsorption as a physical process entirely physisorption. The kinetic parameters were produced from the linear plot of log q_e vs. log(q_e-q_t) for pseudo-1^st-order and (t/q_t) vs. t for pseudo-2^nd-order as shown in Figure 8, respectively. Fit of the straight line (R²) and consistency between calculated and experimental values of q_e, as shown in Tables 2, 3 for Cu²⁺ and Cd²⁺ ions, respectively, were used to assess each sample’s efficacy. As a result, the pseudo-2^nd-order model’s estimation of the theoretical adsorption uptakes of both metal ions on various nanocomposites was more accurate than the pseudo-1^st-order model’s calculation. pseudo-2^nd-order shows that there is a chemical process involved in the adsorption between the adsorbent and the adsorbate, meaning that the ions Cu²⁺ and Cd²⁺ adsorb on the synthesized nanocomposites chemically.

Figure 9 shows both metal ions adsorption isotherms on the assessed guar gum nanocomposites at different temperatures. At 25°C, it emerged that the maximum uptake values of the various films that were prepared for Cu²⁺ were 95, 89, and 84 mg/g for guar gum (80/20, 60/40, and 50/50), respectively. However, at 25°C, the maximum uptake values for Cd²⁺ in guar gum (80/20, 60/40, and 50/50), respectively, were found to be 100, 91, and 87 mg/g. Uptake rose until equilibrium was reached at a known temperature as the equilibrium concentration increased.

The equilibrium adsorption isotherms are the key to understanding the metal ion adsorption mechanism on the prepared guar gum film. The Langmuir and Freundlich isotherms are typically used to characterize the adsorption process (Savaskan Yilmaz et al., 2020). To estimate the removal efficiency for different sets of initial solute concentrations, solution volumes, and adsorbent masses or to forecast the adsorbent mass required for solute removal at in-demand retrieval efficiency—the intrinsic parameter of the Langmuir and Freundlich adsorption isotherms was obtained (Chung et al., 2015; Dakroury et al., 2022). Since the Langmuir equation is believed to be the most widely used isotherm equation for modelling equilibrium data, it was applied to the collected adsorption data. As shown in Figure 10, a straight line with slope and intercept equal to 1/Q_max and 1/K_LQ_max, respectively, was obtained by plotting C_e/q_e against C_e. Measurements were made of the slopes and intercepts for both metal ions adsorption, and the resulting values of Q_max and K_L are reported in Tables 4, 5, respectively, for Cu²⁺ and Cd²⁺. The Q_max values are compared to the experimental values, and the Langmuir model was found to provide a better fit for the experimental data based on the correlation coefficient R² values. These Langmuir model-dependent results demonstrated that monolayer coverage essentially determines the adsorption process, which was validated (Russakova et al., 2021).

From the adsorption data for both metal ions, the Freundlich isotherm was computed by graphing log q_e vs log C_e, which results in a straight line with slope and intercept values equal to 1/n and log K_f, respectively, as shown in Figure 11. The obtained values of K_f, n, and R² for both metal ions with different guar gum nanocomposites were displayed in Tables 4, 5 for Cu²⁺ and Cd²⁺, respectively. These results suggest that the adsorption process is consistent with the Langmuir model. These findings proved that both metal ion adsorption on the different guar gum nanocomposites was accomplished as a monolayer on the homogenous sites of the guar gum nanocomposites and that this process was also demonstrable (Huang and Keller, 2020; Ahmed et al., 2021).

As the revival of the nanocomposites loaded by Cu²⁺ or Cd²⁺ ions was processed using 1% EDTA, regeneration of the loaded nanocomposites by Cu²⁺ or Cd²⁺ was explored (Huang and Keller, 2020). Because of its numerous functional groups, EDTA has a high capacity to form a complex with these two metal ions. The mechanism of the reaction between metal ions and EDTA was shown by Eq. 8. With a standard deviation of ±2%, the regeneration of nanocomposite efficiency was reported to be 95% across two cycles, suggesting the stability of the developed nanocomposites even after repeated use. M aq 2 + + EDTA aq 2 – → M EDTA 2 – aq + 2 H + aq (8) Where M 2 + = Cu 2 + or Cd 2 +

Inquiring into whether the produced guar gum nanocomposite films can be used to retrieve Cu²⁺ and Cd²⁺ ions from actual samples. The various nanocomposite films were used on wastewater that was obtained from NMA’s laboratories. The wastewater was treated individually with each prepared nanocomposite, based on the application of optimal controlling factors that influence the adsorption of both metal ions (pH 6.0, 4h, 25°C). The retrieval of both metal ions from the wastewater before and after the adsorption process was found to be 95.1%, 93.3%, and 91.3% for guar gum (80/20, 60/40, and 50/50), respectively, according to chemical analysis of the wastewater. Based on the previously obtained and discussed data, it was evident that the guar gum nanocomposites (Figure 11) were effective in removing copper and cadmium from wastewater with an effectiveness level above-average 90% due to their chemically stable properties and simplicity of synthesis. A study included comparison between the prepared guar gum nanocomposites with various adsorbents is reported in Table 6 (Suresh et al., 2014; Ahmad and Haseeb, 2015; Ahmad and Hasan, 2016; Ahmad et al., 2017; Yang et al., 2019; Mubark et al., 2022b).