Insight into the performance of novel kaolinite-cellulose/cobalt oxide nanocomposite as green adsorbent for liquid phase abatement of heavy metal ions: Modelling and mechanism

A cost-efficient kaolinite-cellulose/cobalt oxide green nanocomposite (Kao-Cel/Co₃O₄ NC) was successfully synthesized, and utilized as a promising material for removing Pb²⁺ and Cd²⁺ from aqueous solution. The fabricated nanocomposite has been characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis. The batch methodology was exploited for optimization of process parameters and the optimized conditions were found to be adsorbent dosage (2.0 g/L), extraction time (50 min), initial concentration (60 mg/L), and initial solution pH (6). Kao-Cel/Co₃O₄ NC displayed excellent adsorption properties and achieved maximum saturation capacity (Q_m) of 293.68 mg Pb²⁺/g and 267.85 mg Cd²⁺/g, with an equilibration time of 50 min at 323 K. The Langmuir model best expressed the isotherm data recommending the adsorption onto energetically homogeneous NC surface, while the compatibility of kinetics data with pseudo-second-order model revealed the dependency of adsorption rate on adsorption capacity, and probable involvement of chemisorption in the rate-controlling step. Electrostatic interaction and ion exchange mechanism were responsible for the uptake of Pb²⁺ and Cd²⁺ by Kao-Cel/Co₃O₄ NC as demonstrated by Fourier transform infrared spectroscopy and pH studies. Thermodynamic parameters confirmed the physical, spontaneous, and endothermic sequestration processes. Real water investigation specified that the present adsorbent could be effectively used for liquid phase decontamination of Pb²⁺ and Cd²⁺. The nanocomposite exhibited high reusability, which could be utilized efficiently for five runs with sustainable results. In summary, this study portrayed the present nanocomposite as an emerging material for the adsorption of heavy metal ions particularly Pb²⁺ and Cd²⁺.     

Adsorption of Pb(2+) ions on nanosized gamma-Fe(2)O(3): formation of surface ternary complexes on ligand complexation

Adsorption of Pb²⁺ ions on the combustion derived nanosized γ-Fe₂O₃ and its thiourea complex composite is reported. The adsorbents upon adsorption of Pb²⁺ ions are characterised by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis and infrared spectroscopy techniques. The eluent is characterised by atomic absorption spectroscopy for the estimation of Pb²⁺ ions. The reduction in the amount of lead after adsorption was estimated to be around 50% in case of complex composite adsorbent and around 15% in case of the γ-Fe₂O₃ adsorbents. Orthorhombic PbSO₄ precipitated out from the eluent and is reported with a model reaction. Adsorption of lead onto the complex composite is explained through the formation of a surface tertiary complex. The advantage of employing a thiourea-γ-Fe₂O₃ complex composite as solid adsorbent for the adsorption of heavy metal pollutants is envisaged in the present investigation.     

Evaluation of PANI-Averraoha bilimbi leaves activated carbon nanocomposite for Cd2+ and Pb2+ removal from wastewater

In current investigation, we synthesized new Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposites and utilized as cost effectual for the elimination of Cd²⁺ and Pb²⁺ ions from the wastewater. The synthesized nanocomposite was confirmed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX), Fourier Transform-Infrared (FT-IR) spectroscopy and X-Ray Diffraction (X-RD) techniques. A batch adsorption study carried in wastewater containing different concentrations of Cd²⁺ and Pb²⁺ ions in the temperature range of 303–343 K. The results show that, around 80% of Cd²⁺ and Pb²⁺ ions from the wastewater was successfully isolated by using PANI-ABLC nanocomposite. Attempts were made to fit adsorption to different isotherm models. The PANI-ABLC nanocomposite complied Langmuir adsorption model (R² = 0.999) and pseudo-second order kinetics. Further, maximum adsorption efficiency observed at 0.5 g of Polyaniline-Averraoha bilimbi leaves activated carbon nanocomposites. AC- Impedance Spectroscopy (IS) technique shows that, Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposite is suitable for removal of Cd²⁺ and Pb²⁺ ions from the wastewater. AC impedance spectroscopy technique study shows that, the process of adsorption was controlled by charge transfer process.     

A millimeter-sized negatively charged polymer embedded with molybdenum disulfide nanosheets for efficient removal of Pb(II) from aqueous solution

Molybdenum disulfide (MoS₂) has excellent trapping ability for lead ions whereas its micro-/nanoscale size has greatly impeded its practical applications in the flow-through systems. Herein, a millimeter-sized nanocomposite MoS2?001 was synthesized for Pb²⁺ removal by loading MoS₂ nanosheets into a polystyrene cation exchanger D-001 by a facile hydrothermal method. The proposed structure and adsorption mechanism of MoS₂?001 was confirmed by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The nanocomposite showed outstanding adsorption capacity and rapid adsorption kinetic for Pb²⁺ removal, and the adsorption behavior followed the Langmuir adsorption model and pseudo-first-model kinetic model. Pb²⁺ uptake by MoS₂?001 still maintains a high level even in the presence of extremely highly competitive ions (Ca(II) and Mg(II)), suggesting its high selectivity for Pb²⁺ adsorption. Besides, the fixed-bed column experiments further certified that MoS₂?001 is of great potential for Pb²⁺ removal from the wastewater in practical engineering applications. Even more gratifying is that the exhausted MoS₂?001 can be regenerated by NaCl-EDTANa₂ solution without any significant adsorption capacity loss. Consequently, all the results indicated that MoS₂?001 is a promising candidate adsorbent for lead-containing wastewater treatment.     

Magnetic Nitrogen-Doped Porous Carbon Nanocomposite for Pb(II) Adsorption from Aqueous Solution

We report in the present study the in situ formation of magnetic nanoparticles (Fe₃O₄ or Fe) within porous N-doped carbon (Fe₃O₄/N@C) via simple impregnation, polymerization, and calcination sequentially. The synthesized nanocomposite structural properties were investigated using different techniques showing its good construction. The formed nanocomposite showed a saturation magnetization (M_s) of 23.0 emu g⁻¹ due to the implanted magnetic nanoparticles and high surface area from the porous N-doped carbon. The nanocomposite was formed as graphite-type layers. The well-synthesized nanocomposite showed a high adsorption affinity toward Pb²⁺ toxic ions. The nanosorbent showed a maximum adsorption capacity of 250.0 mg/g toward the Pb²⁺ metallic ions at pH of 5.5, initial Pb²⁺ concentration of 180.0 mg/L, and room temperature. Due to its superparamagnetic characteristics, an external magnet was used for the fast separation of the nanocomposite. This enabled the study of the nanocomposite reusability toward Pb²⁺ ions, showing good chemical stability even after six cycles. Subsequently, Fe₃O₄/N@C nanocomposite was shown to have excellent efficiency for the removal of toxic Pb²⁺ ions from water.     

Hydrothermal development of magnetic-hydrochar nanocomposite from pineapple leaves and its performance as an adsorbent for the uptake of Mn2+ and reuse of the metal loaded adsorbent in latent fingerprint

Manganese is one of the heavy metals that is a major environmental concern when present in large amount. Manganese is discarded into water systems by numerous industries, including mining, batteries and electroplating etc. Pineapple leaves were applied as a biomass source to produce a magnetic hydrothermal treated hydochar nanocomposite; Fe₃O₄-HC. The BET surface area of Fe₂O₃-HC nanocomposite was 21.27 m²/g. Batch adsorption experiments revealed that the uptake of Mn²⁺ fit well in the pseudo second kinetics model, while the adsorption isotherm best fit the Freundlich model, with a maximum adsorption capacity of 2.99 mg/g at 25 °C and a pH of 5. The obtained thermodynamic parameters demonstrated that Mn²⁺ ion adsorption using the Fe₂O₃-HC nanocomposite was endothermic and nonspontaneous. Additionally, Fe₂O₃-HC nanocomposite demonstrated to be highly selective towards Mn²⁺ ions in the presence of other ions. The removal percentage of Mn²⁺ from a real water sample spiked with 50 mg/L Mn²⁺ was reported to be 53.2%. The spent adsorbent was then used to detect latent fingerprints, which revealed that Mn²⁺-Fe₂O₃-HC nanocomposite generated better and clear latent fingerprints than Fe₂O₃-HC nanocomposite.     

Novel Fe3O4/hydroxyapatite/β‐cyclodextrin nanocomposite adsorbent: Synthesis and application in heavy metal removal from aqueous solution

The increased global concern on environmental protection has made researchers focus their attention on new and more efficient methods of pollutant removal. In this research, novel nanocomposite adsorbents,i.e., magnetic hydroxyapatite (Fe₃O₄@HA) and magnetic hydroxyapatite β‐cyclodextrin (Fe₃O₄@HA‐CD) were synthesized and used for heavy metal removal. The adsorbents were characterized by FTIR, XRD, TGA, VSM, and SEM. In order to investigate the effect of β‐cyclodextrin (β‐CD) removal efficiency, adsorption results of nine metal ions were compared for both adsorbents. β‐CD showed the most increasing effect for Cd²⁺ and Cu²⁺ removal, so these two ions were selected for further studies. The effect of diverse parameters including pH, contact time, initial metal ion concentration and adsorbent dosage on the adsorption process was discussed. The optimum pH was 6 and adsorption equilibrium was achieved after 1 hr. Adsorption kinetic data were well fitted by pseudo‐second‐order model proposing that metal ions were adsorbed via chemical reaction. Adsorption isotherm was best described by the Langmuir model, and maximum adsorption capacity for Cd²⁺ and Cu²⁺ was 100.00 and 66.66 (mg/g), respectively. Desorption experiment was also done, and the most efficient eluent used for desorption of metal ions was EDTA (0.001 M) with 91% and 88% of Cd²⁺ and Cu²⁺ release, respectively. Recyclability studies also showed a 19% decrease in the adsorption capacity of the adsorbent after five cycles of regeneration. Therefore, the synthesized adsorbents were recognized as potential candidates for heavy metal adsorption applications.     

Selective removal of Cd(II), As(III), Pb(II) and Cr(III) ions from water resources using novel 2-anthracene ammonium-based magnetic ionic liquids

Facile synthesis of two 2-anthracene ammonium-based magnetic ionic liquids (MILs), 2-anthracene ammonium tetrachloroferrate (III) ([2A-A]FeCl₄) and 2-anthracene ammonium trichlorocobaltate (II) ([2A-A]CoCl₃) was performed by protonation of 2-aminoanthracene, followed complexation with FeCl₃/CoCl₂. The MILs were tested in the adsorptive removal of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺ from water sources. Upon treatment with 10 mg dosage of MILs in 10 mL aqueous solution of 50 ppm each of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺, adsorption capacity (mg/g) in the range of 5.73–55.5 and 23.6–56.8 for [2A-A]FeCl₄ and [2A-A]CoCl₃ respectively were recorded. Thus, the optimization, kinetic and isotherms studies were conducted using the [2A-A]CoCl₃ adsorbent. The [2A-A]CoCl₃ was more effective in pH 7–9, and equilibrium adsorption was achieved after 60 min contact time. The adsorption process proceeded via the Pseudo-second order pathway and the Langmuir isotherm model is the best fit for the adsorption process (with q_max = 227 – 357 mg/g) of all the targeted metal ions. The [2A-A]CoCl₃ adsorbent demonstrated practicality with large distribution and selectivity coefficients of the targeted ions, and up to six times regeneration.     

Mixed phase Fe2O3/Mn3O4 magnetic nanocomposite for enhanced adsorption of methyl orange dye: Neural network modeling and response surface methodology optimization

In this research, a novel magnetic mesoporous adsorbent with mixed phase of Fe₂O₃/Mn₃O₄ nanocomposite was prepared by a facile precipitating method and characterized extensively. The prepared nanocomposite was used as adsorbent for toxic methyl orange (MO) dye removal from aqua matrix considering its high surface area (178.27 m²/g) with high saturation magnetization (23.07 emu/g). Maximum dye adsorption occurs at solution pH 2.0 and the electrostatic attraction between anionic form of MO dye molecules and the positively charged nanocomposite surface is the main driving force behind this adsorption. Response surface methodology (RSM) was used for optimizing the process variables and maximum MO removal of 97.67% is obtained at optimum experimental condition with contact time, adsorbent dose and initial MO dye concentration of 45 min, 0.87 g/l and 116 mg/l, respectively. Artificial neural network (ANN) model with optimum topology of 3–5–1 was developed for predicting the MO removal (%), which has shown higher predictive ability than RSM model. Maximum adsorption capacity of this nanocomposite was found to be 322.58 mg/g from Langmuir isotherm model. Kinetic studies reveal the applicability of second‐order kinetic model with contribution of intra‐particle diffusion in this process.     

In situ synthesis of MnO<Subscript>2</Subscript>-loaded biocomposite based on microcrystalline cellulose for Pb<Superscript>2+</Superscript> removal from wastewater

We fabricated a new MnO₂-loaded biocomposite based on microcrystalline cellulose (MCC–MnO₂) by an in situ synthesis method and investigated its adsorption behavior and mechanism for Pb²⁺ removal from aqueous medium. As-prepared MCC–MnO₂ was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses. The effects of pH value, initial Pb²⁺ concentration, contact time, and solution temperature on the uptake of Pb²⁺ onto MCC–MnO₂ were investigated using a batch system. Adsorption equilibrium could be achieved in 3 h for various studied initial concentrations, and a pseudo-second-order model could fit the adsorption behavior well. The equilibrium data could be well described by the Langmuir isotherm model, and the maximum monolayer adsorption capacity of MCC–MnO₂ (with 7.98% MnO₂ loading) for Pb²⁺ was estimated to be 247.5 mg/g at 313 K. Thermodynamic studies indicated a spontaneous and endothermic adsorption process. X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorption mechanism, revealing that the chemical speciation of Pb²⁺ on MCC–MnO₂ was similar to the compound PbO. Moreover, no variations in the valence of Mn were observed after adsorbing Pb²⁺. The regeneration study showed that the adsorption capacity retained about 89.6% of its initial value at the fifth sequential regeneration cycle, indicating that this material is an efficient and renewable hybrid adsorbent for Pb²⁺ removal.     

Synthesis and Properties of Surface Molecular Imprinting Adsorbent for Removal of Pb<Superscript>2+</Superscript>

A new chitosan imprinting adsorbent using diatomite as core material was prepared by using the surface molecular imprinting technology with the Pb²⁺ as imprinted ion. The preparation process conditions of the surface molecular imprinting adsorbent were studied. The adsorbent was characterized by using Fourier transform infrared (FTIR) spectrum. FTIR spectrum indicated that it was cross-linked by epichlorohydrin. The new imprinting adsorbent could provide a higher adsorption capacity for Pb²⁺, which reached 139.6 mg/g increasing 32.3% compared with cross-linking chitosan adsorbent (the initial Pb²⁺ concentration of 600 mg/L). The adsorption velocity was quick and the equilibration time of the imprinting adsorbent for Pb²⁺ was 3 h that shortened about 40% compared with cross-linking chitosan adsorbent. It had a more wide pH range of 5–7 than that of cross-linking chitosan adsorbent. The new imprinting adsorbent can be reused for up to ten cycles without loss of adsorption capacity. In the kinetics and isotherm study, the pseudosecond order model and Langmuir model could represent the adsorption process.     

Preparation of core-shell magnetic Fe3O4@SiO2-dithiocarbamate nanoparticle and its application for the Ni2+, Cu2+ removal

A typical superparamagnetic nanoparticles-based dithiocarbamate absorbent (Fe₃O₄@SiO₂-DTC) with core-shell structure was applied for aqueous solution heavy metal ions Ni²⁺, Cu²⁺ removal.     

Synthesis of anionic gemini surfactant-templated mesoporous silica nanoparticles and its adsorption application for Pb2+

Abstract

Amino-functionalized mesoporous silica nanoparticles (AFMSN) were prepared based on the self-assembly process of the pre-fabricated template of anionic gemini surfactant. The perfect mass ration of the reactants for the synthesis of the AFMSN with high surface area and amino loading was optimized by orthogonal experiments. Adsorption capability of the optimized product for lead ion (Pb²⁺) was investigated in detail. Specially, the effects of the amino content, solution pH, adsorbent dosage, temperature, and interference of other metal ions on the removal efficiency of Pb²⁺ were studied. It is found that these factors can greatly affect the removal efficiency of Pb²⁺ and the prepared adsorbent exhibits the high adsorption selectivity for Pb²⁺. At an optimal condition, the AFMSN adsorbent presents an excellent adsorption capacity for Pb²⁺ up to 211.42?mg/g. The adsorption kinetics study revealed that the pseudo-second-order model could well describe the Pb²⁺ adsorption process, and the adsorption isotherm was fitted well with the Langmuir model. More importantly, the AFMSN adsorbent could be recycled 8 times and a high adsorption efficiency of Pb²⁺ could still be maintained. Therefore, the prepared AFMSN adsorbent may find practical application in removing Pb²⁺ from the polluted water.     

Rapid removal of anionic organic dye from contaminated water using a poly(3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite low-cost adsorbent via adsorption techniques

This research study aims to remove hazardous anionic azo dyes (Congo red (CR)) from aqueous solutions via a simple adsorption method using a poly(3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite (P3ABA/GO/CoFe₂O₄) as a novel and low-cost nanoadsorbent, as synthesized by a simple and straightforward polymerization method. Typically, 3-aminobenzoic acid (3ABA), as monomer, was chemically polymerized with graphene oxide (GO) and cobalt ferrite (CoFe₂O₄) in an aqueous acidic medium containing an ammonium persulfate initiator. The adsorbent P3ABA/GO/CoFe₂O₄ nanocomposite was characterized using various techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, energy-dispersive analysis by X-ray and Brunauer–Emmett–Teller, vibrating sample magnetometer, and zeta potential techniques. These techniques confirmed the interaction between the poly(3-aminobenzoic acid) with GO and CoFe₂O₄ due to the presence of π-π interactions, hydrogen bonding, and electrostatic forces. Herein, the removal efficiency of dye from aqueous solution by the adsorbent was studied according to several parameters such as the pH of the solution, dye concentration, dosage of adsorbent, contact time, and temperature. The adsorption of the dye was fitted using a Langmuir model (R² between 0.9980 and 0.9995) at different temperatures, and a kinetic model that was pseudo-second order (R² = between 0.9993 and 0.9929) at various initial concentrations of CR dye. In addition, the data revealed that the P3ABA/GO/CoFe₂O₄ nanocomposite exhibited a high adsorption capacity (153.92 mg/g) and removal for CR dye (98 %) at pH 5. Thermodynamic results showed the adsorption process was an endothermic and spontaneous reaction. It was found that, in terms of reusability, the P3ABA/GO/CoFe₂O₄ adsorbent can be used for up to six cycles. In this study, P3ABA/GO/CoFe₂O₄ nanocomposites were found to be low cost, and have an excellent removal capability and fast adsorption rate for CR from wastewater via a simple adsorption method. Moreover, this adsorbent nanocomposite could be simply separated from the resultant solution and recycled.     

Using Zeolite/Polyvinyl alcohol/sodium alginate nanocomposite beads for removal of some heavy metals from wastewater

Functionalized Polyvinyl alcohol/sodium alginate (PVA/SA) beads were synthesized via blending Polyvinyl alcohol (PVA) with sodium alginate (SA) and the glutaraldehyde was used as a cross-linking agent. The zeolite nanoparticles (Zeo NPs) incorporated PVA/SA resulting Zeo/PVA/SA nanocomposite (NC) beads were synthesized for removal of some heavy metal from wastewater. The synthesizes beads were characterized via Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analyzer (PSA), and scanning electron microscope (SEM). The adsorption kinetics of the selected metal ions onto Zeo/PVA/SA NC beads followed the pseudo-first-order model (PFO) and the adsorption isotherm model was well fitted by the Langmuir model. Moreover, the thermodynamic studies were also examined; the outcomes showed that the adsorption mechanisms of the selective metal ions were endothermic, the chemical in nature, spontaneous adsorption on the surface of the Zeo/PVA/SA NC beads. The removal efficiency using Zeo/PVA/SA NC modified beads reached maximum at the pH value of 6.0 for Pb²⁺, Cd²⁺, Sr²⁺, Cu²⁺, Zn²⁺, Ni²⁺, Mn²⁺ and Li²⁺ with 99.5, 99.2, 98.8, 97.2, 95.6, 93.1, 92.4 and 74.5%, respectively, while the highest removal are achieved at pH = 5 for Fe³⁺ and Al³⁺ with 96.5 and 94.9%, respectively and decreased at lower or higher pH values. The survival count (%) of the E. coli cells were 34% on the SA beads, 11% on the PVA/SA, and 1% on the Zeo/PVA/SA NC modified beads, after 120 min exposure at 25 °C. Reusability experimental displays that the synthesized beads preserved a significant decrease in the sorption capacity after 10 repeating cycles. The Zeo/PVA/SA NC beads were able to eliminate 60–99.8% of Al³⁺, Fe³⁺, Cr³⁺, Co²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Li²⁺, Sr²⁺, Si²⁺, V²⁺, and Pb²⁺ ions from the natural wastewater samples collected from 10th Ramadan City, Cairo, Egypt.     

Comparison of sorption of Pb<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> on Kaolinite clay and polyvinyl alcohol-modified Kaolinite clay

Kaolinite clay obtained from Ubulu-Ukwu, Delta state in Nigeria was modified with polyvinyl alcohol (PVA) reagent to obtain PVA-modified Kaolinite clay adsorbent. Scanning Electron Microscopy (SEM) of the PVA-modified adsorbent suggests that Kaolinite clay particles were made more compact in nature with no definite structure. Modification of Kaolinite clay with PVA increased its adsorption capacity for 300 mg/L Pb²⁺ and Cd²⁺ by a factor of at least 6, i.e., from 4.5 mg/g to 36.23 mg/g and from 4.38 mg/g to 29.85 mg/g, respectively, at 298 K. Binary mixtures of Pb²⁺ and Cd²⁺ decreased the adsorption capacity of Unmodified Kaolinite clay for Pb²⁺ by 26.3% and for Cd²⁺ by 0.07%, respectively. In contrast, for PVA-modified Kaolinite clay, the reductions were up to 50.9% and 58.5% for Pb²⁺ and Cd²⁺, respectively. The adsorption data of Pb²⁺ and Cd²⁺ onto both Unmodified and PVA-modified Kaolinite clay adsorbents were found to fit the Pseudo-Second Order Kinetic model (PSOM), indicating that adsorption on both surfaces was mainly by chemisorption and is concentration dependent. However, kinetic adsorption data from both adsorbent generally failed the Pseudo-First order Kinetic model (PFOM) test. Extents of desorption of 91% Pb²⁺ and 94% Cd²⁺ were obtained, using 0.1 M HCl, for the Unmodified Kaolinite clay adsorbent. It was found that 99% Pb²⁺ and 97% Cd²⁺, were desorbed, for PVA-modified Kaolinite clay adsorbents within 3 min for 60 mg/L of the metal ions adsorbed by the adsorbents.     

Organoclay modified with lignin as a new adsorbent for removal of Pb2+ and UO2 2+

This study investigated a new adsorbent prepared from lignin modified organoclay for the removal of Pb²⁺ and UO₂ ²⁺ from aqueous solutions. The characterization of new adsorbent was performed by FT-IR and XRD. Adsorption of Pb²⁺ and UO₂ ²⁺ species in aqueous solution as a function of ion concentration, pH, temperature and time of adsorption was investigated in detail. The adsorption data were analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich models. The monolayer adsorption capacities of organoclay–lignin were 0.12 mol kg^?1 and 0.42 mol kg^?1 for Pb²⁺ and UO₂ ²⁺, respectively. The experimental kinetic data were analyzed by using pseudo-second-order kinetic and intra-particle diffusion models. The proposed adsorption mechanism follows a pseudo-second-order kinetic and endothermic because of increasing disorderliness at adsorbate/adsorbent interface.     

A novel ion-imprinted nanocomposite for selective separation of Pb2+ ions

In this study, the ion-imprinting method has been integrated to develop a novel composite material for the selective separation of Pb²⁺ ions. Also, Pb²⁺ ion binding ability of the organosmectite based inorganic-organic composite incorporation of bicyclic C18 organic compound into smectite layers was conducted to draw a projection its potential use as a solid phase exchanger which is quite selective toward Pb²⁺ ions. The ion-imprinted nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), swelling tests, and elemental analyses. After that, maximum binding capacity, pH, and equilibrium binding time were also been optimized. In order to show the selectivity of the composite synthesized, non-imprinted composites were also synthesized in absence of Pb²⁺ ions during polymerization. In this step, Ni²⁺, Co²⁺, Al³⁺, Zn²⁺, and Cu²⁺ ions were used as competitors under batch adsorption conditions. The relative selectivity coefficients of imprinted composite were calculated as 28.5, 156.5, 69.3, 24.8 and 131.6 for Pb²⁺/Co²⁺, Pb²⁺/Cu²⁺, Pb²⁺/Al³⁺, Pb²⁺/Zn²⁺, Pb²⁺/Ni²⁺ binary solutions, respectively. Finally, reusability of the composites was evaluated to show its cost-efficiency by repeating adsorption-desorption experiments ten-times. The adsorption capacity of the imprinted composites did not change significantly whereas that of non-imprinted version reduced dramatically.     

Adsorption of UO2 2+, Tl+, Pb2+, Ra2+ and Ac3+ onto polyacrylamide-bentonite composite

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerization in a suspension of bentonite (B), the composite was then modified by phytic acid (PAA-B-Phy). The parameters related to adsorption of UO₂ ²⁺ in absence and presence of 0.01M CaCl₂ and of natural radionuclides (Tl⁺, Pb²⁺, Ra²⁺ and Ac³⁺ in a leaching solution) onto PAA-B and PAA-B-Phy, and thermodynamics of the adsorption were investigated. Adsorption isotherms were of L and H types for the adsorption of UO₂ ²⁺ onto PAA-B and PAA-B-Phy, whilst for Tl⁺, Pb²⁺, Ra²⁺ and Ac³⁺ they were of C type for both adsorbents. Langmuir equilibrium constants for the adsorption of all studied ions onto PAA-B-Phy were significantly higher than those found for PAA-B. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy. The composite of PAA-B and its modification by Phy have been used for the first time in this study. It is concluded that the composites can be practically used for adsorption and applied as adsorbent of radionuclides.     

Effective ultrasound-assisted removal of heavy metal ions As(III), Hg(II), and Pb(II) from aqueous solution by new MgO/CuO and MgO/MnO<Subscript>2</Subscript> nanocomposites

A series of new (MgO) _x CuO and (MgO) _x MnO₂ nanocomposites were prepared and used as adsorbent for removal of As³⁺, Hg²⁺, and Pb²⁺ ions from aqueous solution with high capacity and detection limit. These nanocomposites were synthesized with different molar ratios by sonochemical method in alkaline solution using polyvinylpyrrolidone as a capping agent and were characterized by FTIR, AAS, UV–Vis spectroscopy, and TEM and SEM imaging. The maximum heavy metal ions adsorption was achieved for (MgO)_0.32CuO and (MgO)_2.9MnO₂ nanocomposites assisted by 3-min sonication using ultrasound. Adsorbent capacity of (MgO)_0.32CuO reached 500.0 mg/g and detection limit was 0.1 ppb for As³⁺. Also (MgO)_2.9MnO₂ nanocomposite adsorbed 457.1 mg/g of Hg²⁺ and 461.2 mg/g of Pb²⁺. Extremely low detection limits of 1.5 and 2.0 ppb were obtained for Hg(II) and Pb(II) ions, respectively, which are much lower than the WHO allowable limits. So, these nanocomposites should be excellent candidate for heavy metal removal with advantage of high capacity, high sensitivity, cost effectiveness and easy preparation.