Investigation of the iridium adsorption process with functionalized magnetic nanoparticles using triisobutylphosphine sulfide extractors | Scientific Reports

Scientific Reports volume 14, Article number: 25756 (2024) Cite this article

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In this research work, the adsorption process of iridium using magnetic nanoparticles functionalized with Cyanex 471X has been investigated. In this regard, parameters affecting the adsorption process such as pH, initial concentration of iridium ions, contact time and adsorbent dosage were assessed. According to the results, pH 6, adsorbent dosage 1.2 g/L, initial concentration of iridium of 10 mg/L, and contact time of 10 min were selected as optimal conditions for iridium adsorption by this synthesized magnetic nanosorbent. The kinetics of the adsorption process was studied, and it was found that the adsorption reaction follows the pseudo-second-order kinetic model with the correlation coefficient of 0.9960. Also, experimental studies indicated that the Langmuir adsorption isotherm model best matches the experimental data (R2 = 0.9961). The maximum adsorption capacity of the nanosorbent for iridium adsorption was estimated to be 35.34 mg/g by the Langmuir isotherm. With the thermodynamic analysis of the adsorption process, it was found that this process is endothermic and spontaneous. In addition, in the investigation of iridium adsorption and desorption, HCl/HNO3 solution with a concentration of 1.5 M was selected as suitable eluent.

Iridium is an element of platinum family metals. Platinum group metals (PGMs), whose elements are ruthenium, iridium, osmium, platinum, rhodium and palladium1,2. Iridium is a white metal and behaves similarly to platinum3. Solid iridium is difficult to work with because of its hardness, brittleness, and very high melting point, and for this reason, its metal powder is often used. The melting point is 2443 °C and it is mechanically solid at temperatures above 1600 °C4. The main use of iridium is to use it as a hardening agent in platinum alloys. Iridium is used in manufacturing furnace boilers and devices that require high temperatures. Iridium-osmium alloy is used in pen balls5. Iridium metal is used in the manufacture of compasses, special machine parts such as spinners, which are small metal plates with very small holes, aircraft parts, parts of scientific and technological space equipment, deep water pipes, catalysts, and high temperature furnaces6.

In order to remove and recovery heavy elements various methods such as chemical precipitation7,8, oxidation or reduction9,10, flotation11,12, membrane technologies13,14,15, adsorption16,17,18,19,20, ion exchange21,22, and solvent extraction23,24,25,26,27,28, have been used to purify heavy elements, including iridium. In recent years, many researchers have tried to isolate and recover iridium using different methods24,25,26,27,28,29,30,31. As mentioned, one of the most important methods is the solvent extraction method. But due to the high cost, the need for special equipment, and the low efficiency, this method has made researchers look for more simple, lower cost, and higher efficiency methods. During the last few years, a method known as the “Magnetically Assisted Chemical Separation (MACS)” method has been invented to extract and separate different elements. This method has the ability to purify elements with high efficiency while being simple and not requiring special equipment. The MACS process is a combination of solvent extraction and magnetic separation. In this process, the desired element is separated from the solution by magnetic nanoparticles (NPs) coated with an extractant. This method was used by Nunes and colleagues for transuranic elements in 199532. The advantages of this method include the simplicity of the process and the lack of special and complex equipment. At the same time, the solvents used in solvent extraction processes are usually toxic, and the use of an extractant loaded on nanoparticles largely prevents these solvents from entering the environment. Therefore, the MACS method is used for the separation of iridium, using magnetic nanoparticles modified with trioctylamine extractant. In this research work, the adsorption process of iridium using magnetic nanoparticles functionalized with triisobutylphosphine sulfide (Cyanex 471X) has been investigated for the first time. The adsorption process affecting parameters such as pH, initial concentration of iridium ions, contact time and adsorbent dosage were assessed. Kinetics, isotherm, and thermodynamics of the iridium adsorption process by this nano adsorbent were also evaluated.

Iridium (III) chloride, iron chloride (II) and (III), methanol (extra pure), and polyethylene glycol 4000 were purchased from Merck (Darmstadt, Germany). Hydrochloric acid (37%) and nitric acid (70%) were obtained from Sigma-Aldrich. All the used chemicals were of analytical grade. Cyanex 471X, supplied by Cytec, Canada was used as extractant. Argon gas was used for deoxygenation during the synthesis process. To adjust the pH of the solutions in all experiments, Metrohm 827 pH meter was used. FT-IR (Bruker, Optics GmbH, Germany) was used to perform FTIR tests. Scanning electron microscopy (SEM, Zeiss, VO 18 Germany) and ICP (ICP-AES, PerkinElmer, OPTIMA 7300 DV. USA) was used to analyze the samples.

In this work, co-precipitation method was used for the synthesis of magnetic nanoparticles. For this purpose, 50 mL of two molar sodium hydroxide was poured into a double-mouthed Laboratory flask and deoxygenated with a gentle stream of argon gas for 30 min. Deoxygenation during this synthesis must be complete and accurate. The presence of oxygen in the synthetic environment during synthesis prevents the formation of black magnetite deposits. In the presence of oxygen, instead of the black precipitate of magnetite, a red precipitate of Fe(OH)3 is formed. Then 1.27 g of iron chloride (II) and 4.7 g of iron chloride (III) were added to the solution. In order to prevent agglomeration of nanoparticles, 6 g of polyethylene glycol 4000 is added to the synthetic solution. At this stage, the content of this flask is added to an Erlenmeyer flask containing 40 mL of 0.6 M hydrochloric acid and stirred with a magnetic stirrer for 30 min until it was completely dissolved and a clear solution is obtained. The obtained yellow solution is poured into a 50 mL burette and added dropwise to a sodium hydroxide solution. As the first drop is added, the nanoparticles begin to form as a black precipitate. The produced nanoparticles were separated by a magnet and washed several times with distilled water. The prepared nanoparticles were dried at room temperature and powdered using a glass mortar.

To coat nanoparticles with Cyanex 417X extractor, a certain amount of Cyanex was dissolved in 5 mL of ethanol and a certain amount of nanoparticles was added to it. The solution was placed in an ultrasonic device for 10 min to disperse well. Then, the charged nanoparticles were removed from the solution and placed at room temperature until they were completely dry. To compare and confirm the coating of nanoparticles with Cyanex, two samples were prepared before and after the modification of nanoparticles, and their FTIR spectrum was analyzed. Different ratios, i.e., 5, 10, 20, 35, 55, 75, 80, 110% of Cyanex to nanoparticles (CYNX/NPs) were prepared and based on the maximum percentage of iridium adsorption, the best coating ratio was determined and used in adsorption experiments.

The performance of functionalized magnetic nanoparticles for iridium adsorption was investigated in terms of initial pH, initial iridium concentration, adsorbent dosage, contact time, and temperature. All experiments were carried out in 150 mL conical flasks. The experimental solution contained 20 mL of iridium chloride with a predetermined initial concentration, different adsorbent dosages and at specified initial pHs. Adsorption efficiency was checked by taking samples at predetermined time intervals. Adsorption performance was determined by analyzing the concentration of iridium in the filtrates. In order to reduce the error, all experiments were repeated twice and the average results were reported. The concentration of iridium ions in the solutions was determined using ICP.

In order to calculate the adsorption amount per unit mass of adsorbent (mg/g) and removal percentage Eqs. (1) and (2) were used, respectively.

The chi-square (χ²) parameter, Eq. (15) was used to calculate the error of the models employed.

Nanoparticles formed in the synthesis sate can be two types of magnetite (Fe3O4) or maghemite (Fe2O3), with magnetite being the preferred type in this adsorption process. The difference between these two types can be identified primarily by the color of nanoparticles. Magnetite particles are black. The more the color of the formed synthesized nanoparticles tends to black, the more dominant is the amount of magnetite particles formed, and if the tendency to brown is more, maghemite is more dominant. The color of synthesized nanoparticles in this work was completely black, which confirms the magnetite type of nanoparticles. In addition, the XRD results (Fig. 1) and their comparison with the reference spectrum of Fe3O4 also confirm this33.

XRD spectrum of nanoparticles before and after modification with Cyanex 471X.

The size of the synthesized nanoparticles was calculated using the Debye-Scherrer equation (Eq. 4)34, which was equal to 8.1 nm.

Where D is the nanoparticles mean size, K is the dimensionless shape factor, λ is the X-ray wavelength, β is the full width at half maximum (FWHM), and θ is the Bragg’s angle.

The magnetization measurement of the synthesized nanoparticles was investigated using vibrating sample magnetometry (VSM) at room temperature. According to Fig. 2, the magnetization value of the synthesized nanoparticles in the presence of a magnetic field of 6.23 emu g− 1, which reaches zero after removing the field, indicates that the nanoparticles are superparamagnetic. In other words, these particles exhibit magnetic properties in the presence of a magnetic field and are separated from each other when the magnetic field is removed.

Magnetization curve of synthesized nanoparticles at room temperature.

Figure 3 shows the FT-IR spectrum of magnetic nanoparticles before and after coating with Cyanex 471X, respectively. The adsorption bands of 454 and 575 cm− 1 indicates the existence of Fe-O bonds in nanoparticles. The bands in the 2919 and 2852 cm− 1 regions indicate the presence of C-H bonds. The vibrations related to CH2 in the structure of polyethylene glycol and cyanex extractant can be seen in the 2919 and 2858 cm− 1 bands. The broad stretching band at 3440 cm− 1, and the 1629 and 565 cm− 1 bands in the figure indicate the presence of Fe3O4 magnetite. The peak in the range of 2960 cm− 1 is caused by the symmetric stretching vibration of CH3 in Cyanex 471X. The peak in the range of 2872 cm− 1 is caused by the asymmetric stretching vibration of CH3 in Cyanex 471X. The adsorption band in the range of 650 cm− 1 is caused by the C-C bond in Cyanex 471X. The observation of a weak adsorption band near 2500 cm-1 can be partly attributed to the presence of sulfur. By examining the FTIR spectra before and after coating, it can be claimed that the surface of the nanoparticles is coated with Cyanex 471X.

FT-IR spectrum of nanoparticles before and after coating with Cyanex 471X.

Figure 4(a) and 4(b) show the SEM images of magnetic nanoparticles before and after functionalization with Cyanex 471X, respectively, which clearly show the effect of the functionalization.

SEM image of (a) bare magnetic nanoparticles and (b) magnetic nanoparticles functionalized with Cyanex 471X.

In order to find the appropriate ratio of Cyanex to nanoparticles, a series of adsorption tests were performed with different ratios of Cyanex to nanoparticles and the results are shown in Fig. 5. With reference to this figure, with the increase in the ratio of Cyanex to nanoparticles, the efficiency of adsorption increases and reaches to 92% in a ratio of 80%. By increasing the ratio of Cyanex to nanoparticle more than 80%, the percentage of removal has reached an almost constant value, and with the increase of the ratio of Cyanex to nanoparticle, the percentage of removal does not increase much. On the other hand, in ratios higher than 80%, the nanoparticles are not well dispersed and the particles are agglomerated and stick together. Therefore, the ratio of 80% is considered as the optimal ratio and this ratio is used in all experiments. Due to the high specific surface area, magnetic nanoparticles play an essential role in the adsorption of ions, especially iridium, but by coating them with solvents such as Cyanex 471X, the amount and percentage of nanosorbent adsorption increases, which indicates the role of Cyanex 471X in iridium adsorption (Fig. 5). According to the figure, the percentage of iridium removal by magnetic nanoparticles before coating was about 60%, and after coating with Cyanex 471X, the removal percentage increased to 92.34%. Also, according to the color difference of the two solutions before and after adsorption and the discoloration of the solution after the adsorption process, it can be concluded that the nanosorbent has adsorbed iridium ions (Fig. 6).

The removal percentage of iridium (pH = 6, [Ir] = 10 mg/L, Adsorbent dosage = 1.2 g/L, T = 25 ℃)

Iridium solution before and after adsorption.

The initial pH of the solution is one of the most important parameters affecting the amount of heavy metal adsorption. To assess the effect of pH on the iridium adsorption efficiency by this nanosorbent, a series of adsorption tests were performed at initial pHs ranging from 1 to 7, and the results are shown in Fig. 7. Based on the figure, with increasing pH, the adsorption efficiency of iridium increases from about 62.35% at pH 1 to about 92.45% at pH 6, and after that, the adsorption efficiency decreases. Therefore, pH 6 is considered as the optimal pH.

The effect of initial solution pH on iridium adsorption efficiency with functionalized magnetic nanoparticles using Cyanex 471X ([Ir] = 10 mg/L, CYNX/NPS = 80%, Adsorbent dosage = 1.2 g/L, T = 25 ℃)

Figure 8 shows the effect of adsorbent dosage on the adsorption percentage of iridium in the range of 0.2 to 6 g of adsorbent per 1 L solution. As can be seen in the figure, the adsorption proportion increases when adding adsorbent quantities of up to 1.2 g/L; however, at values higher than 1.2 g/L, the adsorption percentage decreases rapidly. The trigger for the sudden increase in adsorption percentage with increasing adsorbent amount is the increase in the number of sites available for adsorption. At dosages higher than 1.2 g/L, due to the agglomeration and sticking together of the nanosorbent particles, the adsorption efficiency decreases noticeably35. Therefore, the adsorbent dosage of 1.2 g of adsorbent in one liter of solution was chosen as the optimal dosage.

The effect of adsorbent dosage on iridium adsorption efficiency with functionalized magnetic nanoparticles using Cyanex 471X ([Ir] = 10 mg/L, CYNX/NPS = 80%, pH = 6, T = 25 ℃)

Figure 9 shows the effect of contact time on iridium adsorption. According to the figure, the adsorption percentage increases with increasing contact time up to 20 min, and after that, due to the accumulation of iridium ions in the active sites on the adsorbent, it remains constant. The results show that most of the adsorption occurs in the first 10 min of the process, which relates to the occupation of accessible surface sites for the adsorption of iridium ions. After the saturating all external active sites on the adsorbent surface, the rate of the adsorption process decreases until equilibrium is reached.

The effect of contact time on iridium adsorption efficiency with functionalized magnetic nanoparticles using Cyanex 471X ([Ir] = 10 mg/L, CYNX/NPS = 80%, pH = 6, Adsorbent dosage = 1.2 g/L, T = 25 ℃)

The above data can be used to investigate the kinetic models of iridium adsorption. In this research, four pseudo-first-order, pseudo-second-order, Elovich, and interparticle diffusion kinetic models were assessed.

The pseudo-first-order model is the simplest adsorption kinetic model that expresses the adsorption kinetics based on a surface reaction step. The linearized form of the pseudo-first-order kinetic equation is as follows:

where k1 (min− 1) is the model constant, qt and qe (mg/g) are the adsorption capacity at time t and equilibrium time, respectively36.

The pseudo-second order model considers the chemical reaction as the main resistance of the adsorption process. The linearized form of the pseudo-second-order model is as follows:

where k2 (mg.g− 1.min− 1) is the model constant36.

In the adsorption system, one of the mass transfer resistances is the internal penetration resistance. One of the methods to determine whether the adsorption process is controlled by penetration resistance is to use the square root of the contact time. The interparticle penetration kinetic model expresses this relationship as follows:

where ki (mg.g− 1.min− 0.5) is the internal infiltration intensity constant and C (mg/g) is the boundary layer thickness. If the qt diagram in terms of t0.5 deviates from the Linear form, it can be concluded that the adsorption process is not controlled by the internal penetration resistance36.

Elovich kinetic model is suitable for interpreting the results when chemisorption occurs. The linear form of this model is as follows:

where α (mg.g− 1.min− 1) and β (mg.g− 1.min− 1) are related to the initial rate of adsorption and the amount of activation energy required to cover the surface, respectively36.

The results of the kinetic investigation of iridium adsorption on functionalized magnetic nanoparticles using Cyanex 471X are given in Fig. 10; Table 1. According to these figure and table, and comparing the R2 and χ2, it is clear that the pseudo-second-order kinetic model matches the experimental results well and better than other models. Also, by comparing the values of the experimental adsorption rate (\(\:{q}_{e}^{exp})\) and calculated (\(\:{q}_{e}^{cal})\:\)by the pseudo-second-order kinetic model, the compatibility between these two values is clearly evident. Therefore, it can be concluded that the adsorption process can be a chemical process37,38.

Kinetics (a) pseudo-first-order, (b) pseudo-second-order, (c) Elovich, and (d) interparticle diffusion; plots for iridium adsorption with functionalized magnetic nanoparticles using Cyanex 471X ([Ir] = 10 mg/L, CYNX/NPS = 80%, pH = 6, Adsorbent dosage = 1.2 g/L, T = 25 ℃)

To investigate the effect of the initial concentration of thorium ions in the solution on the adsorption percentage, the feed solutions were prepared with initial concentration of 6, 10, 20, 40, 50, 60, 80, and 100 mg/L, and by performing a series of experiments, the effect of the initial concentration on the adsorption percentage was checked in the equilibrium state and the results are shown in Fig. 11(a). Based on the figure, with increasing the initial concentration of iridium, the amount of adsorption also increases. The increase in adsorption capacity is due to the high driving force and the availability of active sites for adsorbing iridium ions. At high concentrations, the active adsorption sites on the adsorbent become saturated and the adsorption reaches an almost constant value.

One of the important requirements in designing an adsorption system is to find an isotherm (a suitable relationship) to describe the results of adsorption equilibrium experiments. Equilibrium isotherms of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich have been investigated to fit the equilibrium data in this research work. The Langmuir model considers that the adsorption process takes place on a surface. This model assumes the adsorption process as single-layer and is used for dynamic equilibrium adsorption on homogeneous surfaces. The linearized form of this isotherm is as follows:

where qe (mg/g) is the adsorption amount at the equilibrium, Ce (mg/L) is the equilibrium concentration, qm (mg/g) is the maximum adsorption capacity, and KL (L/mg) is the Langmuir constant.

To check the desirability of the adsorption process, the dimensionless parameter, RL, is defined according to the following relation, which is called the separation factor.

RL > 1 indicates unfavorable adsorption. RL = 1 one means linear isotherm and 0 < RL < 1 indicates favorable adsorption. RL = 0 equal to zero indicates irreversible adsorption39.

The Freundlich isotherm considers the adsorption process to be heterogeneous. The linearized form of this isotherm is as follows:

where Kf (L/g) is the Freundlich constant and n is the dimensionless Freundlich constant39.

In the Temkin isotherm, it is assumed that as the amount of adsorption increases, the heat of adsorption decreases linearly. The linear form of this isotherm is as follows:

where R (J.mol− 1.K− 1) is the universal gas constant, and T is the temperature in Kelvin. KT (L/g) and bT (J/mol) are the Temkin isotherm constants, which are related to the maximum bond energy and heat of adsorption, respectively39.

The Dubinin-Radushkevich isotherm is a model used to describe the adsorption mechanism on a heterogeneous surface with a Gaussian energy distribution. This model generally demonstrates good compatibility and correlation with cases involving high activities of the adsorbing component, as well as middle ranges of concentrations. The linearized form of the D-R isotherm can be expressed as follows:

where Kdr is the Dubinin-Radushkevich isotherm constant (mol2/kJ2) and E represents the term RT Ln(1 + 1/Ce). To determine if the adsorption process is physisorption or chemisorption, the parameter E, which represents the average free energy per mole of the adsorbate, is typically used. The equations for calculating the parameters e and E are provided as Eqs. (14) and (15), respectively.

Figure 11(b)-(e) and Table 2 show the results of linear modeling of the adsorption isotherms.

Based on the results and the comparison of the correlation coefficients, and χ2 of these four models, the Langmuir model fitted the experimental data better than the others. Therefore, it can be said that the adsorption process of iridium by the functionalized magnetic nanoparticles is monolayer. RL changes from 0.04 to 0.42, which indicates that the adsorption process of iridium by this nanosorbent is favorable. Also, according to the value of EDR calculated by Dubinin-Radushkevich model, which is equal to 1.58 and less than 8 kJ/mol, the absorption mechanism is of a physical type40.

(a) The effect of initial concentration on iridium adsorption amount, and linear modeling of the adsorption isotherms (b) Langmuir, (c) Freundlich, and (d) Temkin (CYNX/NPS = 80%, pH = 6, Adsorbent dosage = 1.2 g/L, T = 25 ℃).

In order to assess the effect of temperature on the adsorption percentage and to determine the thermodynamic parameters of the adsorption process of iridium with this functionalized nanoparticle, a series of adsorption experiments were conducted under optimal conditions at temperatures of 35 and 45 ℃. The thermodynamic parameters of the change in Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) are determined using the Van’t-Hoff equation as the following functions:

where T is the temperature in Kelvin, R is the gas constant (8.314 J/mol K), and KC is the Koble-Corrigan constant.

In order to determination of the values of ΔH° and ΔS°, respectively, the slope and intercept of the line obtained from the values of Van’t-Hoff Ln (KC) in terms of 1/T were used. According to the results of adsorption experiments, Gibbs free energy values are − 5.76, -6.22 and − 6.73 kJ/mol at 25, 35 and 45 ℃, respectively (Fig. 12). The values of ΔH° and ΔS° were determined to be 8.67 kJ/mol and 0.0484 kJ/mol, respectively. Negative sign of ΔG° shows the feasibility of the adsorption process in terms of thermodynamics and the spontaneity of this process. A positive value of ΔH° indicates that the adsorption process is endothermic. The positive value of ΔS° is due to the exchange of iridium metal ions with mobile ions in the exchanger, which leads to an increase in entropy during the adsorption process31.

Van’t Hoff plot of iridium adsorption on to functionalized magnetic nanoparticles using Cyanex 471X ([Ir] = 10 mg/L, CYNX/NPS = 80%, pH = 6, Adsorbent dosage = 1.2 g/L)

For the desorption of adsorbed iridium by magnetite nanosorbent coated with Cyanex 471X, hydrochloric acid, nitric acid, a mixture of these two acids (in equal volumetric proportions) and ammonium acetate (all with a concentration of 0.2 M) were used. The percentage of adsorbed iridium was calculated with the following equation:

where Cads and Cdes (mg/L) are the concentration of adsorbed and desorbed iridium, respectively.

The results of the desorption experiments can be seen in Fig. 13(a). According to the obtained results, HCl/HNO3 solution was chosen as the desired iridium stripping solution. After selecting the desorption solution, in order to find the appropriate concentration of this solution, a series of new desorption tests using concentrations of 0.1, 0.2, 0.3, 0.5, 1, 1.5, 2 molars of HCl/HNO3 were done and the results are shown in Fig. 13(b). According to the figure, with the increase in the concentration of the selected solution, the desorption percentage reaches an almost constant value after a rapid upward trend, and after that, increasing the acid concentration had no effect on the desorption efficiency. Therefore, the concentration of 1.5 molar was determined to be the optimal concentration of the desorption solution.

(a) The effect of acidic and alkaline stripping agents on the percentage of iridium desorption and (b) the effect of stripping solution concentration on the percentage of iridium desorption.

The influence of interfering ions of gold, osmium, palladium, platinum, rhenium, rhodium, and ruthenium on the adsorption of iridium in aqueous solutions was investigated with the adsorbent used in this study. These elements were chosen as iridium-associated elements because of their similar chemical properties. First, the solutions containing iridium and each of the interfering ions were prepared in pairs with a concentration of 10 mg/L for each of the elements, and the separation process was performed by nanoparticles on each separately under optimal conditions magnetic nanoparticles were separated by magnets and the final samples were analysed by ICP analysis. The results are shown in Fig. 14.

The effect of platinum group on the uptake of iridium ions,

Adsorbent amount 0.03 g, pH = 6, contact time 10 min, 80% = CYNX / NPS.

Finally, 20 mL of a solution containing all of the above elements at a concentration of 10 mg/L as well as iridium, was prepared. The adsorption test was then carried out under optimal conditions at ambient temperature and for 10 min. The final solution was analyzed by ICP. The results can be seen in Fig. 15. According to the obtained results, gold, platinum, palladium, and osmium ions significantly compete with iridium ions in adsorption by coated magnetite and have influenced the adsorption efficiency of iridium to some extent. According to the results and investigation of the effect of interfering metals, this adsorbent can be suitable for the absorption of noble metals.

The effect of ion-interfering platinum group on iridium adsorption (25 mL solution contains 10 mg/L iridium, Amount of adsorbent 0.03 g, pH = 6, Contact time 10 min, CYNX/NPS = 80%).

Different adsorbents have been used to adsorb iridium, which are compared with the results of the present work in Table 3.

In this study, the adsorption of iridium ions was investigated using functionalized magnetic nanoparticles as the adsorbent. The magnetic nanoparticles were prepared and functionalized by MACS method using Cyanex 471X as the functionalizing agent. The results demonstrate that this functionalized nanosorbent is highly effective in adsorbing iridium ions from aqueous solutions. The influence of various parameters, such as pH, initial iridium concentration, contact time, and adsorbent dosage on adsorption process were investigated and the optimal conditions were determined to be: pH = 6, adsorbent dosage = 1.2 g/L, initial iridium concentration = 10 mg/L, and contact time = 10 min. The experimental data was best described by the pseudo-second-order kinetic model. Also, the Langmuir adsorption isotherm model showed the best agreement with the experimental data. Furthermore, the Langmuir adsorption isotherm model showed the highest correlation with the experimental data. The maximum adsorption capacity of the nanosorbent was estimated to be 35.34 mg/g using the Langmuir isotherm model. Thermodynamic analysis revealed that the adsorption process is endothermic and spontaneous in nature. A 1.5 M HCl/HNO3 solution was found to be an effective eluent for the desorption of iridium from the nanosorbent.

Data sets generated and/or analysed during the current study available from the corresponding author on reasonable request.

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The authors would like to thank everyone who helped with this work and the Research Institute of Nuclear Science and Technology in Tehran for financial and technical support.

Department of Chemistry, Payame Noor University (East Tehran Branch), Tehran, Iran

Shiva Moghtaderi & Shahla Mozaffari

Nuclear Fuel Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box 11365-3486, Tehran, Iran

Kamal Saberyan, Hossein Sid Kalal, Ali A. Gh. Khamseh & Ahmad Nozad Golikand

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Shiva. Moghtaderi: Data curation, Investigation. Hossein Sid Kalal: Project administration, Conceptualization; original draft, Writing – review & editing. Kamal Saberyan and Ali A. Gh. Khamseh: Resources, Writing - review & editing. Shahla Mozaffari and Ahmad Nozad Golikand: Conceptualization, Investigation.

Correspondence to Hossein Sid Kalal.

The authors declare no competing interests.

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Moghtaderi, S., Saberyan, K., Sid Kalal, H. et al. Investigation of the iridium adsorption process with functionalized magnetic nanoparticles using triisobutylphosphine sulfide extractors. Sci Rep 14, 25756 (2024). https://doi.org/10.1038/s41598-024-77551-y

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Received: 14 July 2024

Accepted: 23 October 2024

Published: 28 October 2024

DOI: https://doi.org/10.1038/s41598-024-77551-y

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