Uranyl adsorption on (001) surfaces of kaolinite: A molecular dynamics study

The aim of the present paper is to investigate the adsorption of uranyl species (UO₂)^2 +(H₂O)₅ onto kaolinite (001) surfaces. To this end we have employed molecular dynamic simulations based on CLAYFF force field potential. Various types of surface model for inner-sphere adsorption complexes and one model for outer-sphere adsorption complexes were optimized. In order to have a neutral structure, the uranyl (UO₂)^2 +(H₂O)₅ or the kaolinite was deprotonated to form the outer-sphere or inner-sphere adsorption complexes. Both singly protonated and partially deprotonated states of the Al(0) kaolinite surface were considered for adsorption in the model of inner-sphere complexes. The first uranyl coordination shell exhibits pentagonal bi-pyramidal symmetry with the pentagonal formed by 5 water molecules. We show that the average U–OW distances are between 2.49 and 2.57 Å for water molecules. The bond of uranyl with deprotonated O⁻ center is always short because of the charge attraction. The obtained results agree well with density functional calculations and EXAFS measurements, and show how and why the adsorption of uranyl appears on the surface of kaolinite.     

Separation of Uranyl Ions on Starch-Based Functional Hydrogels: Mechanism and Kinetics

In this article, we report the mechanism and kinetics of adsorption of uranyl ions on starch-based functional hydrogels. The hydrogels were prepared from starch in native or hydrolyzed/oxidized form by crosslinking with N,N-methylenebisacrylamide. The hydrogels synthesized from the oxidized starch have carboxylic groups at C-6 position. The effect of the structure and external environmental factors, i.e., contact time, temperature, ion strength, and simulated seawater (0.55 M NaCl and 3 mM NaHCO₃), was investigated on the uranyl adsorption behavior of hydrogels. The adsorption of uranyl ions was rapid as the highest adsorption was observed after 6 h and at 40°C. The sorbents also exhibited appreciable ion uptake even from the simulated seawater. The equilibrium data was analyzed using Langmuir and Freundlich adsorption isotherms and pseudo-first order and pseudo-second order kinetic models. Evidence of adsorption was obtained by characterization of the uranyl ions-loaded hydrogels by FTIR spectroscopy and also by elution with 0.1 N HCl.     

Understanding the adsorption of calcium sulfate on tetracalcium aluminoferrite and tricalcium aluminate surfaces

Calcium sulfate (CaSO₄), an essential retarder in cement, retards the hydration of tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF) phases. However, its retarding mechanism remains unclear. This paper focused on the adsorption of CaSO_4f on C₄AF and C₃A surfaces based on isothermal calorimetry, the measurement of the ionic concentrations in a diluted system, and density functional theory to enhance the understanding of the retardation mechanism. The results showed that the retarding effect of CaSO₄ on C₄AF was stronger than that on C₃A due to the slower CaSO₄ consumption rate, lower driving force for CaSO₄ adsorption, and surface coverage of Fe(OH)₃ gel. The adsorption of CaSO₄ hindered Ca dissolution more markedly on C₄AF than C₃A, which was pronounced on Fe-free C₄AF surfaces. The adsorption of CaSO₄ weakened the affinity of water on C₄AF and C₃A surfaces, lowering the driving force for H₂O adsorption. The adsorption of H₂O and CaSO₄ promoted the dissolution of Al on the [AlO₆] octahedral surface of C₄AF, which may be responsible for the maintenance of a higher Al concentration in the solution. Based on the above results, the adsorption of CaSO₄ on initial C₄AF and C₃A hydration was explained.     

Importance of activated carbon's oxygen surface functional groups on elemental mercury adsorption

The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury (Hg⁰) was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N₂), air oxidation (693 K), and nitric acid (6N HNO₃) treatment of two activated carbons (BPL, WPL) were conducted to vary their surface oxygen functional groups. Adsorption experiments of Hg⁰ by the activated carbons were conducted using a fixed-bed reactor at a temperature of 398 K and under N₂ atmosphere. The pore structures of the samples were characterized by N₂ and carbon dioxide (CO₂) adsorption. Temperature-programmed desorption (TPD) and base-acid titration experiments were conducted to determine the chemical characteristics of the carbon samples. Characterization of the physical and chemical properties of activated carbons in relation to their Hg⁰ adsorption capacity provides important mechanistic information on Hg⁰ adsorption. Results suggest that oxygen surface complexes, possibly lactone and carbonyl groups, are the active sites for Hg⁰ capture. The carbons that have a lower carbon monoxide (CO)/CO₂ ratio and a low phenol group concentration tend to have a higher Hg⁰ adsorption capacity, suggesting that phenol groups may inhibit Hg⁰ adsorption. The high Hg⁰ adsorption capacity of a carbon sample is also found to be associated with a low ratio of the phenol/carbonyl groups. A possible Hg⁰ adsorption mechanism, which is likely to involve an electron transfer process during Hg⁰ adsorption in which the carbon surfaces may act as an electrode for Hg⁰ oxidation, is also discussed.     

Density functional theory study on adsorption of thiophene on TiO2 anatase (0 0 1) surfaces

In order to develop a fundamental understanding of the adsorption mechanism of thiophenic compounds on TiO₂-based adsorbents for ultra-deep desulfurization of liquid hydrocarbon fuels, a density functional theory (DFT) study was conducted on the adsorption of thiophene over the TiO₂ anatase (0 0 1) surface. The perfect, O-poor (with oxygen vacancies), and O-rich (with activated O₂ on the surface) anatase (0 0 1) surfaces were built, and the interaction of thiophene molecule with these surfaces was examined. The adsorption configuration and adsorption energy on the different surfaces and sites were estimated. The results showed that thiophene may be adsorbed on both the perfect and O-poor surfaces through an interaction between the Ti cations on the surface and the S atom in thiophene, whereas on the O-rich surface through an interaction of the activated O atoms (the dissociatively or associatively adsorbed O₂) on the surface with the S atom in thiophene to form a sulfone-like surface species. The adsorption of thiophene on the O-rich surface is significantly stronger than adsorption on the perfect and O-poor surfaces on the basis of the calculated adsorption energies. The results indicate that the activated O₂ on the TiO₂ anatase (0 0 1) surface may play an important role in the adsorption desulfurization over the TiO₂-based adsorbents, and increased concentration of the activated O₂ on the surface may result in improvement of the adsorption capacity of the adsorbents.     

Behaviors of Chemically Crosslinked CAAMPS Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked (C) polyelectrolyte acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid (CAAMPS) hydrogels. CAAMPS hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and water by free radical polymerization in an aqueous solution using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). The swelling equilibrium of polyelectrolyte copolymer gels containing of CAAMPS hydrogels has been studied as a function of copolymer composition. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. The weight-swelling ratio of CAAMPS hydrogels was increased up to 127.03 (for 300 mg AMPS and crosslinked by EGDMA) and 93.32 (for 300 mg AMPS and crosslinked by BDMA), while acrylamide hydrogels swelled up to 10.27 (crosslinked by EGDMA) and 10.06 (crosslinked by BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 0.67 × 10^?3–2.11 × 10^?3 mol uranyl ion per gram for CAAMPS hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio, (K _d ) of uranyl ions was calculated to be 0.10–0.43 for CAAMPS hydrogels.     

Development of novel adsorbent materials for recovery and enrichment of uranium from aqueous media

A new polymeric adsorbent bearing both hydrophilic groups providing swelling in water and amidoxime groups for chelating with uranyl ions (UO₂²⁺), has been developed and its adsorptive ability for recovering uranium from aqueous media has been investigated. The polymers obtained by irradiating the solution of polyethylene glycol (PEG) in acrylonitrile (AN) are defined as interpenetrating polymer networks (IPNs) and the adsorbent has been obtained by applying the amidoximation reaction to the IPNs with a conversion ratio of ∼ 60%. Kinetics of the conversion reaction of the cyano (CN) group to the amidoxime (HONCNH₂) group has been studied by reacting with hydroxylamine (NH₂OH) solution at a molar ratio of NH₂OH/CN = 1.25 in aqueous media at three different temperatures, 30, 40, and 50°C, for 3–4 days. The degree of amidoximation ratio was determined by UO₂²⁺ ion adsorption and FTIR spectrometry and the UO₂²⁺ ion adsorption values were found by both UV and gamma spectrometry and also by gravimetry. It was found that the polymeric adsorbent has a very high adsorption ability for uranium and quite a good stability in aqueous media. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2475–2480, 1997     

Identification of individual 4-methylpyridine molecules physisorbed and chemisorbed on TiO2(110)-(1 x 1) surface by STM

We succeeded in identifying geometries of 4-methylpyridine (4-MP) molecules adsorbed on a TiO₂(110)-(1 x 1) surface based on sequential STM imaging. Characteristics in mobility, topographic height, and location allowed us to distinguish three adsorption states at room temperature: a chemisorbed state with the upright geometry (A₁), a flat-lying state localized at specific sites (A₂), and a flat-lying physisorbed state mobile over the surface (B). The concentration of A₁ and A₂ species was restricted at an order of 0.01 ML. The A₂ state was related to the adsorption at oxygen vacancies resident on the vacuum-annealed surface. The present study demonstrates the promising ability of STM to identify the adsorption geometry of small probe molecules, 4-methylpyridine in the present case, and to provide atom-level information on the origin of acidic property of oxide surfaces. This revised version was published online in July 2006 with corrections to the Cover Date.     

Surface Charge of Variable Porosity Al2O3(s) and SiO2(s) Adsorbents

The surface charge properties of two SiO₂ and three Al₂O₃ mineral adsorbents with varying degrees of framework porosity were investigated using discontinuous titration and ion adsorption methodologies. Points of zero net charge (p.z.n.c) for porous and non-porous SiO₂ were <2.82 and for Al₂O₃ minerals ranged from 6.47–6.87. Silica surfaces possessed very slight negative charge in the acid pH range (pH < 7) and significant dissociation of silanol groups occurred at pH > 7. Variation of surface charge density with aqueous proton concentration was nearly identical within a mineral type (i.e., SiO₂ or Al₂O₃) irrespective of the degree of framework porosity, indicating that the densities of dissociable surface sites are equivalent, when normalized to surface area. The results suggest that the use of titration methods alone may be insufficient for thorough surface charge characterization, particularly at low and high pH. Proton titrations should be coupled with concurrent ion adsorption measurements to confirm surface charge development. Discontinuous proton titration and ion adsorption data, which were in agreement in the slightly acidic through slightly basic pH range, both indicated that p.z.n.c. was equal to the point of zero net proton charge (p.z.n.p.c.) for the variable charge minerals investigated.     

Uranyl Ion Uptake from Aqueous Solutions by Chemically Cross-linked Polyelectrolyte CAMA Hydrogels

Uranyl ion adsorption from aqueous solutions has been investigated by chemically cross-linked polyelectrolyte acrylamide/maleic acid (CAMA) hydrogels. CAMA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), maleic acid (MA), and water by free radical polymerization in aqueous solution using multifunctional cross-linkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K _i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô) for CAMA hydrogel-uranyl ion binding system were calculated by using Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 3.29 × 10^?4 ? 15.87 × 10^?4 mol uranyl ion per gram for CAMA hydrogels. Adsorption of uranyl ion was changed range 8.17–48.10%.     

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite (SMC) was investigated. The SMCs were prepared by the adsorption of cis-1-aminoctadecen-9 (oleylamine) on both modified and unmodified natural clinoptilolite tuff. The properties of the modified clinoptilolite samples, such as cation type, structure of the zeolite framework and ECEC value, determined the mechanism of oleylamine adsorption, and consequently anion adsorption on the external clinoptilolite surface. According to the strength of the anion adsorption, two groups of SMCs could be distinguished: strong and weak anion adsorbents. Strong anion adsorbents were obtained by oleylamine adsorption on H⁺-clinoptilolites by protonation of the –NH₂ groups. This mechanism of oleylamine adsorption resulted in the surface precipitation mechanism of anion adsorption being the dominant mechanism. The oleylamine derivatives of Ca- and Na-clinoptilolite were weak anion adsorbents. Oleylamine is adsorbed on Ca- and Na-clinoptilolite by hydrogen bonding, thus yielding insufficient adsorption sites for anions. Hydrogenchromate and dihydrogenphosphate anions were nevertheless adsorbed on these SMCs by interaction with oleylamine. The experiments of anion adsorption on various oleylamine loaded SMCs confirmed the existence of two types of anion adsorption sites and showed that excess oleylamine did not significantly influence the anion adsorption in the investigated concentration range. The kinetic results showed that SO₄²⁻ and H₂PO₄⁻ adsorptions were slow processes while HCrO₄⁻ adsorption was completed in a few minutes.     

Adsorption of uranyl ions and microscale distribution on Fe-bearing mica

The interaction of uranyl ions (UO₂²⁺) with Fe-bearing mica is an important determinant of the mobility of U species in granitic rocks or their weathered terrains, especially with regard to radionuclide migration. To understand their interaction, U sorption experiments were conducted on both fresh and oxidized biotites, especially examining an effect of oxidized mineral surfaces which was treated by H₂O₂ for 3 weeks. The U sorption onto the biotite reached a maximum at around pH 7.0, and the amount adsorbed by the oxidized biotite was much larger than that by the fresh one. The difference of the adsorption capacity between the two biotites may be attributed to an increase in the specific surface area by oxidization, which accompanies some slightly peeled off and reactive surfaces with amorphous precipitates. During the U adsorption reaction, there was a continuous depletion of K⁺ ions from the interlayer space. At the same time structural Fe was released and oxidized near the edges, forming non-detectable very small goethite particles. Such an incipient feeble crystalline Fe (hydr)oxide phase was only detected by scanning electron microscopy (SEM), but its location interestingly corresponded to the U adsorbed position on the biotite surface, implying its strong adsorption of U. Besides, the crystallized Fe (hydr)oxide seems to be relatively more effective in the adsorption of U as compared with the amorphous one on the H₂O₂ treated biotite.     

Study of nisin adsorption on plasma-treated polymer surfaces for setting up materials with antibacterial properties

Setting up antibacterial materials by nisin adsorption on surfaces depends mainly on the surface properties and the surface treatments allowing the modification of such properties. In order to investigate the factors affecting such adsorption, the native low density polyethylene (LDPE) was modified using Argon/Oxygen (Ar/O₂) plasma, nitrogen (N₂) plasma and plasma-induced grafting of acrylic acid (AA). The films were studied by various characterization techniques. The chemical surface modification was confirmed by X-ray photoelectron spectroscopy (XPS), the wettability of the surfaces was evaluated by contact angle measurements, the surface charge was determined by the zeta potential measurements, and the changes in surface topography and roughness were revealed by atomic force microscopy (AFM). Nisin was adsorbed on the native and the modified surfaces. The antibacterial activity, the nisin adsorbed amount, and the peptide distribution were compared for the four nisin-functionalized films. The highest antibacterial activity was recorded on the Ar/O₂ followed by AA then by N₂ treated films and the lowest activity was on the native film. The observed antibacterial activity was correlated to the type of the surface, hydrophobic and hydrophilic interactions, surface charge, surface topography, nisin adsorbed amount, and nisin distribution on the surfaces.     

Adsorptive removal of uranium from water by sulfonated phenol–formaldehyde resin

Adsorption characteristics of a sulfonated phenol‐formaldehyde resin (SPR) have been studied for U removal from aqueous solution by means of batch method. Adsorption experiments have been carried out as a function of contact time, solution/adsorbent ratio, particle size and pH. Adsorption isotherm has been evaluated by changing adsorbent dosage in the range of 0.04–80 g/L at an initial uranyl nitrate concentration of 0.05 mol/L. The enormous adsorption capacity of 0.29 mol/g estimated from the plateau region of the S shaped isotherm is well comparable the Langmuir capacity of 0.31 mol/g. Equilibrium data are also adequately well described by the Freundlich and the Dubinin‐Radushkevich (D‐R) isotherm equations. The parameters of the isotherms and pH dependency of distribution coefficients (K_D) indicate that polymeric uranyl chains form on bidentate surface complex as a result of solute–solute interactions on the adsorbent surface. Both desorption and elution studies show that uranyl chains are irreversibly bounded on the SPR. Kinetic curves having a fast initial part followed by a slower process well fit both McKay model based on two‐resistance diffusion and Nernst‐Plank model with single diffusion coefficient. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cu(II) Adsorption of Activated Carbon Fibers Produced by Radiation-Induced Graft Polymerization

In this work, the adsorption behaviors of activated carbon fibers (ACFs) containing chelating functional groups were studied in heavy metal ion removal. The ACFs were modified by electron beam and glycidyl methacrylate (GMA, CH₂—CCH₃COOCH₂CHOCH₂) graft polymerization in order to induce chelating functional groups, such as iminodiacetate (IDA, NH(CH₂COOH)₂) groups on the ACF surfaces. Fourier transform-infrared spectrometry (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties of the ACFs. The specific surface area and the pore structure were evaluated from nitrogen adsorption data at 77 K. The adsorbed amount of heavy metal ions was measured by using inductively coupled plasma-atomic emission spectrometer (ICP-AES). Results of FT-IR and XPS showed that the relative intensity of oxygen peaks increased with increasing the dose of electron beam. The results indicated that the radicals were increased as the dose of electron beam irradiation increased, and increased radicals led to the increase of the IDA groups. Also, the adsorption of heavy metal ions was increased by increasing the dose of electron beam irradiation. It was explained that the IDA groups of the treated ACF surfaces were introduced by radiation-induced graft polymerization and the increased IDA groups led to an increase of the adsorption of heavy metal ions.     

Determination of the fractal dimension of alumina using adsorption: Challenges of choosing appropriate adsorbates and analysis methods

The classical method for surface characterisation of the porous structure of the catalysts is nitrogen (N₂) adsorption at ?196°C, which provides a catalyst surface area value valid for molecules similar in size to N₂ (0.162 nm²/molecule). To complement and obtain more information about the materials, catalyst surfaces can be characterised using fractal geometry. The fractal dimension of a sample can be determined by the adsorption uptake of molecules of different sizes on the surface of interest in order to obtain a characteristic parameter of the surface geometry known as the fractal dimension, D. In this work, the value of D for a γ‐alumina catalyst support has been determined (D = 2.71 ± 0.15) using different adsorbates (argon, nitrogen, isopropanol, pyridine, and n‐butane). The decision process for choosing these adsorbates and the challenges of this type of characterisation method are discussed in this article. © 2011 Canadian Society for Chemical Engineering     

Exploring Potential Methods for Anchoring Amine Groups on the Surface of Activated Carbon for CO2 Adsorption

Activated carbon can be effectively modified for CO₂ adsorption with amine groups due to their high affinity for CO₂. Using approaches such as impregnation, some modifiers containing amine groups are physically adsorbed on the surface of carbon, whereas other amine groups can be directly or indirectly chemically bound to the activated carbon matrix. In the context of exploring potential techniques for grafting amine groups onto activated carbon surfaces, we herein review the literature on modifications applied to different materials and supports for a variety of applications, limited to neither activated carbon nor CO₂-adsorption applications. We focus on the processes of grafting amine groups and the parameters influencing these processes. Moreover, the mechanism of CO₂ adsorption involving amine groups is discussed.     

Ozonide ions on the surface of MgO nanocrystals

The adsorption properties of oxygen radicals on the surface of polycrystalline oxides can provide relevant information about the functionality of specific surface sites in oxidation catalysis. Using electron paramagnetic resonance spectroscopy, we investigated O₂ adsorption at MgO nanocrystal surfaces which were previously enriched with O⁻ radicals i.e. trapped hole centers. On dehydroxylated particle surfaces, two ozonide radical types O ₃ ⁻ were isolated as adsorbates and the related energies for O₂ adsorption were found to be 55 ± 5 kJ mol⁻¹ and 100 ± 5 kJ mol⁻¹. The respective adsorption sites are assigned to hole centers trapped on oxygen terminated corners and cation vancancies, respectively. In addition, O ₃ ⁻ ions were also employed as probes for electron trapping sites on partially hydroxylated sample surfaces. Five types of O⁻ radicals emerge from surface colour centre bleaching with N₂O, but only two of them adsorb O₂ at room temperature. A connection between the well-characterized (H⁺)(e^-) defect – an electron trapped in close vicinity of a nearby proton [Chiesa et al. J. Phys. Chem. B 109 (2005) 7314] – and one ozonide type which exhibits significant magnetic coupling with an adjacent proton, was established on the basis of their production parameter dependence. Although the g tensor of an O₃ ⁻ species reflects the properties of the radical itself rather than the structure of the adsorption site, the related signatures are proposed to serve also as spectroscopic fingerprints for catalytically relevant surface anion environments.     

Accumulation of uranium on austenitic stainless steel surfaces

The surface contamination by uranium in the primary circuit of PWR type nuclear reactors is a fairly complex problem as (i) different chemical forms (molecular, colloidal and/or disperse) of the uranium atoms can be present in the boric acid coolant, and (ii) only limited pieces of information about the extent, kinetics and mechanism of uranium accumulation on constructional materials are available in the literature. A comprehensive program has been initiated in order to gain fundamental information about the uranium accumulation onto the main constituents of the primary cooling circuit (i.e., onto austenitic stainless steel type 08X18H10T (GOSZT 5632-61) and Zr(1%Nb) alloy). In this paper, some experimental findings on the time and pH dependences of U accumulation obtained in a pilot plant model system are presented and discussed. The surface excess, oxidation state and chemical forms of uranium species sorbed on the inner surfaces of the stainless steel tubes of steam generators have been detected by radiotracer (alpha spectrometric), ICP-OES and XPS methods. In addition, the passivity, morphology and chemical composition of the oxide-layers formed on the studied surfaces of steel specimens have been analyzed by voltammetry and SEM-EDX. The experimental data imply that the uranium sorption is significant in the pH range of 4-8 where the intense hydrolysis of uranyl cations in boric acid solution can be observed. Some specific adsorption and deposition of (mainly colloidal and disperse) uranyl hydroxide to be formed in the solution prevail over the accumulation of other U(VI) hydroxo complexes. The maximum surface excess of uranium species measured at pH 6 (Γ_sample = 1.22 μg cm⁻²U ≅ 4 × 10⁻⁹ mol cm⁻² UO₂(OH)₂) exceeds a monolayer coverage.     

Novel magnetic polyamic hydrazide nanocomposite: Preparation,characterization, and application for the removal of cd2+ and pb2+ from industrial wastes

In this work, a novel polymer polyamic hydrazide (PAH) was synthesized via the reaction of terephthalohydrazide with pyromelitic dianhydride. The obtained PAH was characterized with nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy and elemental analysis. Finally, a novel magnetic nanocomposite was prepared by immobilization of PAH on the Fe₃O₄ nanoparticles in water. The prepared magnetic nanocomposite was successfully used for selective removal of Pb²⁺ and Cd²⁺ ions from industrial wastes and the effects of affecting parameters on the adsorption capacity of the magnetic nanocomposite adsorbent for the removal of Pb²⁺ and Cd²⁺ from model aqueous solutions were investigated. The maximum adsorption capacities of Pb²⁺ and Cd²⁺ were found to be 138.9 and 103.1 mg g^?1, respectively. The kinetics and mechanism of the adsorption of Pb²⁺ and Cd²⁺ on the surface of the prepared nanocomposite were studied and it was found that complex formation between active sites of the surface of the nanocomposite and metal ions is the possible mechanism for adsorption of metal cations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42538.