Adsorption Process Of Metal Ions Research Articles

Adsorption of Chromium Ions from Aqueous Solutions by Synthesized Nanoparticles

In the present manuscript, an attempt has been made to remove chromium metal ions from synthetic effluent using adsorption process. The synthesized titanium dioxide nanoparticles were used as adsorbents. Adsorption studies were performed in batch process. Various characterization of synthesized nanoparticles such as XRD analysis, optical properties of nanoparticles using UV‐visible absorption spectroscopy, concentration of chemical bonds, and atomic arrangement using (FTIR) have been performed and analyzed. The dependency of adsorption percentage of metal ions and equilibrium amount of metal adsorbed with respect to pH, adsorbent dosage, initial concentration, and temperature are studied. Mechanisms of metal ion adsorption process explained by various adsorption isotherms and adsorption kinetic models. The criteria for statistical significance of correlation coefficient (R2) for fitting the experimental data to the various isotherms were tested and analyzed. The experimental results reveal that synthesized titanium dioxide nanoparticles could be used as adsorbents in order to remove chromium ions present in industrial wastewater.

Molecular dynamic simulation and artificial intelligence of lead ions removal from aqueous solution using magnetic-ash-graphene oxide nanocomposite

In this work, the heavy metal ions (lead, Pb) adsorption process were studied using an artificial intelligence simulation based model for prediction of the adsorption process by using magnetic ash/graphene oxide (GO) nanocomposite. Also, the adsorption mechanism of Pb ions on the adsorbent were investigated using molecular dynamics (MD) calculations in aqueous solution. Reactivity of structures, ionization energy (I), electron affinity (A), chemical hardness (η), chemical softness (σ), and energy gap (ΔEgap) of all compounds were obtained from the HOMO–LUMO energy levels. The outcomes demonstrated that the adsorption of Pb ions on the adsorbent occurred through electrostatic interactions and van der waals bonding and the lead-water-GO configuration had the highest adsorption affinity according the ΔEgap calculations. The artificial neural network (ANN) with two hidden layers was used for developing the model with a mixture of linear and non-linear transfer functions. The equilibrium (Eq.) concentration of the Pb ion as an important factor in predicting the adsorption capacity of adsorbent was considered for the model output and initial Pb ion concentration as well as solution temperature were assumed as the model inputs. The training and validation procedure of ANN indicated great agreement between the experimental and predicted data according to the high coefficient of determination and low root mean square error (R2 > 0.999, RMSE = 0.086). Based on the simulation results increasing the initial concentration of Pb ion significantly affect the Eq. concentration while the solution temperature had a lower effect on Eq. concentration. The results of this study provide valuable model for pollutants removal. MD calculations and artificial intelligence simulation methods could be an appropriate combined technique for predicting the adsorption behavior of nanocomposite in heavy metal ions removal from the aqueous solution with high accuracy.

Alternative treatment for metal ions removal from acid mine drainage using an organic biomixture as a low cost adsorbent

Acid mine drainage, characterized by low pH and elevated heavy metal ion concentrations, causes severe harm to the environment. In this study, the feasibility of a new organic biomixture adsorbent for removing Fe3+, Zn2+, Cu2+ and Mn2+ metal ions from synthetic acid mine drainage was evaluated. This kinetic study showed fast metal ions adsorption within the first four to eight hours, and adsorption over 80% in the organic biomixture. The equilibrium adsorption isotherms resulted in a metal ion uptake greater than 84%, and the Freundlich model fitted well the data. The Freundlich affinity coefficient (Kf) ranged from 1.44 to 3.82 in the following order: Zn2+>Cu2+>Fe3+>Mn2+. Scanning electron microscope images revealed the heterogeneous structure of the biomixture, and energy-dispersive X-ray analysis after adsorption confirmed the ability of the biomixture to remove the metal ions. In the fixed-bed column, the Thomas model described (R2>0.95) the adsorption process of metal ions contained in the treated acid mine drainage well. The adsorption capacity (q0) of this system resulted in 164.2 mg g−1, 129.2 mg g−1, 26.0 mg g−1 and 15.3 mg g−1 of Fe3+, Zn2+, Cu2+ and Mn2+, respectively. This study confirmed the efficiency of an organic biomixture to adsorb metal ions and provide new and valuable information for the future design of low-cost treatments to reduce acid mine drainage pollution.

The behavior and mechanism of the adsorption of Pb(II) and Cd(II) by a porous double network porous hydrogel derived from peanut shells

Adsorption has been deemed as one of the most efficient technologies for the removal of heavy metals from water because of its diversity of adsorbents, low cost, and simple operation. In this study, acrylic acid underwent free radical polymerization in an aqueous solution of lignocellulose extracted from peanut shells (PS) to form a porous double network hydrogel adsorbent, PS(H)-PAA. The PS(H)-PAA hydrogel had high water permeability and a porous network structure, which could provide a fast channel for metal ions diffusion from solution into hydrogel and gave rise to good adsorption performance. The adsorption process of heavy metal ions on the PS(H)-PAA hydrogel was identified to be a spontaneous endothermic adsorption and reached kinetic equilibrium within only 10 min for Pb(II) and 60 min for Cd(II) at an initial concentration of 100 mg/L using 0.5 g/L of adsorbent. According to a Langmuir model, at T =313 K the maximum theoretical adsorption capacities were as high as 250.42 and 109.89 mg/g for Pb(II) (pH 5) and Cd(II) (pH 6), respectively. Moreover, a PS(H)-PAA hydrogel showed good adsorption performance over a pH range of 4–9. The surface properties, dimensional morphology, and thermal stability of the adsorbents were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and derivative thermogravimetry. The adsorption behavior under different conditions (such as pH, contact time, ion strength, and interfering ions) and the adsorption mechanism were studied. The adsorption mechanism indicated that oxygen- and nitrogen-containing functional groups play a major role in the adsorption process, primarily through chemical interactions, and secondarily through physical interactions. In addition, these adsorbents exhibited strong chemical stability, had very high swelling ratios in water, and could be recycled easily. These results indicate the developed PS(H)-PAA hydrogel is an environmentally friendly and potentially effective adsorbent for the removal of heavy metals.

Adsorption process and mechanism of heavy metal ions by different components of cells, using yeast (Pichia pastoris) and Cu2+ as biosorption models.

Microbial biomass has been recognized as an essential biosorbent to remove heavy metal ions, but the biosorption process and mechanism of different components of microbial cells have not been elucidated. In present study, Pichia pastoris X33 and Cu2+ was used as a biosorption model to reveal the biosorption process and mechanism of different components of microbial cells. For the biosorption of whole cells, the maximum removal efficiency was 41.1%, and the adsorption capacity was 6.2 mg g−1. TEM-EDX analysis proved the existence of Cu2+ on the cell surface and cytoplasm. The maximum Cu2+ removal efficiency of the cell wall, cell membrane and cytoplasm were 21.2%, 20.7% and 18.5%, respectively. The optimum pH of Cu2+ biosorption of the P. pastoris cell, cell wall, cell membrane and cytoplasm was 6. Moreover, the maximum adsorption capacity of the cell, cell wall, cell membrane and cytoplasm was 16.13, 11.53, 10.97 and 8.87 mg g−1, respectively. The maximum removal efficiencies of P. pastoris biomass treated with proteinase K and P. pastoris biomass treated with β-mannanase were 18.1% and 28.2%, respectively. The maximum removal efficiencies of mannan and glucan were 34% and 12%, respectively. The FTIR spectra showed that the amino group (N–H), hydroxyl (O–H), carbon oxygen bond (C–O), –CH, C–N and carbonyl group (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O) of a ketone or aldehyde may interact with Cu2+. Thus, our work provides guidance for further understanding the effect of different cell components on biosorption.

Fabrication of PVA Nanofibers Grafted with Octaamino-POSS and their Application in Heavy Metal Adsorption

Wastewater treatment is one of the focuses in current society, and the removal of heavy metal ions from it is crucial in wastewater treatment. Polyvinyl alcohol (PVA) nanofibers play a certain role in the adsorption of heavy metal ions, but their adsorption capacity is limited. In this work, maleic anhydride (MAH) was first grafted onto the molecular chain of PVA. Then through the condensation of the carboxyl group and the amino group, the octaamino-POSS was successfully grafted on the PVA molecular chain. Two kinds of nanofibers, PVA/octaamino-POSS nanofibers as well as PVA-g-POSS nanofibers, were fabricated by electrospinning technology for the adsorption of Pb2+ and Cu2+ in wastewater. The preparation of PVA/octaamino-POSS was used to compare which metal ion adsorption process was more stable, physical blending or chemical grafting. With the increase of contact time, the adsorption capacity of PVA/octaamino-POSS nanofibers to Cu2+ increased at first and then decreased. It was observed that the adsorption capacity of PVA-g-POSS to heavy metal ions was higher than that of PVA/octaamino-POSS. With the increase of octaamino-POSS content, the equilibrium adsorption of Pb2+ and Cu2+ on PVA-g-POSS nanofibers was significantly improved, with prominent adsorption effect for Cu2+. Based on the analysis of quasi-first-order and quasi-second-order dynamic equation, it was deduced that the chemical adsorption and physical adsorption worked together in the adsorption process of Pb2+ and Cu2+ by PVA-g-POSS, and chemical adsorption played a major role.

Adsorption of Cu2+, Cd2+ and Pb2+ in wastewater by modified chitosan hydrogel

ABSTRACT Heavy metal pollution is extraordinary critical, so it is urgent to develop an effective adsorbent to dispose of such pollution. Modified chitosan was combined with polyacrylic acid to form N-carboxymethyl chitosan hydrogel (NCS-hydrogel) adsorbent. The morphology and structure of NCS-hydrogel were analyzed and identified by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and other characterization methods. NCS-hydrogel adsorption was used to treat water pollution of Cu, Cd and Pb ions, and the influencing factors of adsorption performance were studied. The intrinsic mechanism of adsorption process was discussed by thermodynamic, kinetic and isotherm models. The results show that the adsorption process of metal ions by NCS-hydrogel meets the spontaneous monolayer chemisorption, and the adsorption process is accompanied by heat release.

Adsorption mechanism of toxic heavy metal ions on oxygen-passivated nanopores in graphene nanoflakes

In this work, using density functional theory, we investigate the adsorption process of toxic metal ions (Hg2+, Cd2+, and Pb2+) on graphene nanoflakes (GNF) comprised of various sized oxygen-passivated nanopores to gain molecular insights into the ability of such surfaces in effectively removing the metal ions from contaminated environments. Thermodynamically, the adsorption of these ions on the oxygen-passivated nanopores is shown to be more energetically favorable than that on the pristine surface. The dispersion corrected adsorption energy calculations indicate Hg2+ ion to have the highest and Pb2+ ion the lowest affinities for interaction with such surfaces (Hg2+ > Cd2+ > Pb2+). The highest adsorption of Hg2+ and Cd2+ ions on the surfaces is seen in the 12-crown-3…Hg2+ (− 382.9 kcal/mol) and 12-crown-3…Cd2+ (− 314.7 kcal/mol) complexes, while Pb2+ ion shows the highest adsorption energy for the 18-crown-6 surface (− 195.0 kcal/mol). Noncovalent interaction plots, Hirshfeld charge analysis and energy decomposition analysis conclude that the role of charge transfer in formation of surface…ion complexes is more important than noncovalent interactions and therefore plays a key role in the adsorption of these ions on the surfaces. The magnitude of charge transfer in the complexes follows the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+, which is consistent with the adsorption energetic order of these metal ions on the surfaces. We also found that Pb2+ ion is mainly adsorbed on the surfaces via electrostatic interactions, while Hg2+ and Cd2+ ions are adsorbed through van der Waals (vdW) interactions. This could be attributed to the presence of vacant p orbitals on Pb2+ ion, which interact with the π bonds on the GNF and oxygen atoms in the nanopores through electrostatic interactions. No such vacant orbitals are available for Hg2+ and Cd2+ ions thus resulting in such ions adsorbing via vdW interactions. The contribution of ΔEorb, induction energy component of total energy, for the surface…Hg2+ complexes is more than that for the surface…Cd2+ and surface…Pb2+ complexes, following the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+ again, consistent with the calculated adsorption energy order suggesting that charge transfer indeed plays a major role in formation of such surface…ion complexes. Finally, time-dependent density functional theory calculations show that the absorption spectra of the surfaces undergo significant changes, including peak shifts, peak quenching and appearance of new peaks, upon interaction with Hg2+, Cd2+, and Pb2+ ions, such changes being consistent with binding energetics rank order of ions on these surfaces. These complexes would have potential applications in near-infra-red photonics in addition to their service of effectively remediating of toxic heavy elements from contaminated environments.

Surface modifications of nanochitosan coated magnetic nanoparticles and their applications in Pb(II), Cu(II) and Cd(II) removal

Nano-chitosan coating nano-iron oxide was prepared and its surface was modified with two different compounds (crotonaldehyde and succinic anhydride). The prepared nano-materials (Nano-CI, nano-CIC and nano-CIS) were characterized by FTIR, TGA, XRD, SEM, TEM and BET analyses. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were exhibit average size between 9.32–20.57 nm for nano-materials. Nano-CI, nano-CIC and nano-CIS sorbents were studied for adsorption of Pb(II), Cu(II) and Cd(II). The adsorption process of heavy metal ions was investigated by batch equilibrium technique and several controlling factors were studied. The maximum adsorption capacity values were distinguished in the following order Cu(II) > Pb(II) > Cd(II) as 4700, 2700, and 1800 μmol g–1, respectively. The adsorption equilibrium time was found at (10−30) min for studied heavy metal ions. The applicability of nano-CI, nano-CIC and nano-CIS sorbents to absorb toxic heavy metal ions from sea water and wastewater samples was tested by using micro-column technique. The effect of adsorption temperature (25, 35, 45 and 55 ± 1 °C) on the adsorption of heavy metals by nano-CI, nano-CIC and nano-CIS adsorbents was also investigated. The pseudo-second order is the best and more fitted for the adsorption reactions. Langmuir is the best fitted for removal of the studied metals.

Removal of Pb(II), Zn(II), Sn(II) and Cu(II) Ions from Aqueous Solutions by Linear Alternating Poly(4,4'-biphenol oxalate) Oligomer

Poly(4,4′-biphenol oxalate) oligomer was synthesized and characterized by FT-IR, elemental analysis XRD and thermal analysis. The capability of the oligomer to take away Pb(II), Zn(II), Sn(II) and Cu(II) metal ions from aqueous solutions was considered by the known batch and column techniques in terms of concentration, pH value, contact time and temperature. The results indicated that a high initial rate of metal-ion uptake by the oligomer was observed throughout the first 30 minutes, which enlarged slightly amid rising the pH value and then reached its greatest value at pH=5.00 for Pb(II) and Zn(II), pH=4.00 for Cu(II) and pH=6.00 for Sn(II). The oligomer exhibited a high metal-ion uptake capacity to Pb(II) and Zn(II), but a little metal-ion uptake capacity to Cu(II) and Sn(II). Linearized forms of the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherms were used to investigate the experimental equilibrium concentration data of Pb(II), Zn(II), Cu(II) and Sn(II). ΔG values demonstrated that the adsorption process of these metal ions on the oligomer is favored while the ΔH values indicated that this process is endothermic. On the other hand, the entropy of the process is positive. In addition to batch experiments, column experiments were performed, where the metal ions were efficiently recovered by treatment of the metal-loaded oligomer with 1.0 M HNO3, 1.0 M HCl and 0.5 M EDTA. The best results were obtained with 1.0 M HNO3 solution.

Sulfonated Pentablock Copolymer Membranes and Graphene Oxide Addition for Efficient Removal of Metal Ions from Water.

Nowadays heavy metals are among the higher environmental priority pollutants, therefore, the identification of new, effective, reusable and easy-to-handle adsorbent materials able to remove metal ions from water is highly desired. To this aim, in this work for the first time, sulfonated pentablock copolymer (s-PBC, Nexar™) membranes and s-PBC/graphene oxide (GO) nanocomposite membranes were investigated for the removal of heavy metals from water. Membranes were prepared by drop casting and their chemical, structural and morphological properties were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic mechanical analysis (DMA) and small-angle X-ray scattering (SAXS). The adsorption abilities and adsorption kinetics of both the polymer and the s-PBC/GO nanocomposite were investigated for the removal of different heavy metal ions (Ni2+, Co2+, Cr3+ and Pb2+) from aqueous solutions containing the corresponding metal salts at different concentrations. The investigated s-PBC membrane shows a good efficiency, due to the presence of sulfonic groups that play a fundamental role in the adsorption process of metal ions. Its performance is further enhanced by embedding a very low amount of GO in the polymer allowing an increase by at least three times of the adsorption efficiencies of the polymer itself. This can be ascribed to the higher porosity, higher roughness and higher lamellar distances introduced by GO in the s-PBC membrane, as evidenced by the SEM and SAXS analysis. Both the polymeric materials showed the best performance in removing Pb2+ ions.

A review of the application of sea material shells as low cost and effective bio-adsorbent for removal of heavy metals from wastewater.

The pollution caused by heavy metal ions in industrial wastewater is of a great concern. Applying effective and low-cost methods is an urgent need for treatment of polluted water and aqueous solutions. Biosorption have received the most attention among the various methods. It has become an alternative technique to conventional technologies due to low cost, simple operation and treatment for heavy metal recovery, and high selectivity. In recent years, sea material shells have been applied as one of the most cost-effective bio-adsorbents due to their special properties. They are environmentally friendly, low cost, and easy to access and have high adsorption capacity. The purpose of this review is to present the application of oyster shell, snail shell, and shrimp shell as low-cost and effective biosorbents for removal of noxious heavy metals from aqueous solutions. In addition, heavy metals, their sources, and ways to remediate them from waste streams and various factors affecting the biosorption process with sea materials shells are also reviewed. Moreover, a brief description and literature review of the equilibrium, kinetic, and thermodynamic behaviors of the heavy metal ion adsorption process on sea material shells have been studied. Finally, further applications of sea materials shell for waste effluents treatment are specially focused.

Efficient Removal of Ni(II) and Co(II) Ions from Aqueous Solutions Using Silica-based Hybrid Materials Functionalized with PAMAM Dendrimers

ABSTRACT Many techniques of metal ions removal have been already implemented; however, there is still need for novel, efficient, and non-toxic adsorbents dedicated to heavy metals. In a recent study, the adsorptive properties of four hybrid materials consisting of silica platform surface grafted with poly(amidoamine) dendrimers (PAMAM) with different amino-terminal components, toward two heavy metal ions: Ni(II) and Co(II), were examined. The materials showed maximal scavenging properties at pH 5.4. To determine the adsorptive nature of the hybrid materials, experimental isotherms were fitted by the Langmuir, the Freundlich, and the Dubinin–Radushkevich models. All materials exhibited adsorption capability best described by the Langmuir model. The calculated adsorption capacities qm ranged between 86.7 and 116.6 mg g−1 for Ni(II) ions and 32.8 and 101.1 mg g−1 for Co(II) ions, which strictly indicate the influence of grafting agent structure on adsorptive properties of hybrid materials. The values of mean free energy E and adsorption enthalpy ΔH° jointly indicated the physical nature of adsorption processes. From the thermodynamic studies, the values of ΔH°, ΔS°, and ΔG° were obtained, indicating the spontaneous and endothermic character of investigated Ni(II)/Co(II) metal ions adsorption process on SiO2–dendrimer hybrid materials. Moreover, the materials exhibited selectivity toward Ni(II) ions.

Kinetic, isothermal, thermodynamic and adsorption studies on Mentha piperita using ICP-OES

The present study reflects the efficiency of Mentha piperita waste (MP) as an environmental friendly and cost-effective novel adsorbent for the sequestration of Cd(II), Co(II), Cr(VI) and Pb(II) from synthetically prepared wastewaters through batch adsorption experiments. MP was characterized and identified using SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy), TEM (Tanning Electron Microscopy, FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-Rays Diffraction) and TGA (Thermogravimetric analysis). The efficacy of MP adsorbent for the removal of Cd(II), Co(II), Cr(VI) and Pb(II) was investigated by varying MP dose (15–75 mg), solution pH (2–12), initial adsorbate concentration (0.2–0.6 mg L − 1), ionic strength of KNO3 (0 – 0.1 M) and temperature (298 K – 328 K). On increasing MP dose, the metal percent removal increased. The equilibrium time for the adsorption of Cd(II), Co(II), Cr(VI) and Pb(II) onto MP was found at 90, 90, 60 and 60 min, respectively. The adsorption capacity was found to increase with increasing pH of the metal solutions up to a value of 8.0 for Cd(II), 6.0 for Co(II), 2.0 for Cr(VI) and 6.0 for Pb(II) on MP. Moreover, it remains unchanged with additional increase of pH. Equilibrium data were best fitted by linear Freundlich isotherm model, which indicates multilayer adsorption. Kinetic study showed that the adsorption process of metal ions follows pseudo-second-order kinetics, suggesting chemisorption. Thermodynamic calculations suggested endothermic reactions for Cd(II), Co(II) and Cr(VI), while exothermic reactions for Pb(II) and spontaneous nature for all the metal ions adsorption onto MP adsorbent. MP showed a satisfactory adsorption performance due to its nano range particle size (13.4 nm to 51.7 nm) and good adsorption capacity. As a result, this study concluded that Mentha piperita wastes could be used as low-cost potential sorbent for the removal of Cd(II), Co(II), Cr(VI) and Pb(II) from aqueous solutions.

Synthesis and application of hydrazono-imidazoline modified cellulose for selective separation of precious metals from geological samples

A new hydrazono-imidazoline modified cellulose (HIMC) was synthesized for selective recovery of Pt(IV), Pd(II) and Au(III) from geological samples. Cellulose was oxidized by periodate and was further functionalized with hydrazono-imidazoline moieties to afford N-donor chelating fibers. Scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N2 physisorption, elemental analysis, and energy-dispersive X-ray spectroscopy (EDX) were used for characterization. Introducing the hydrazono-imidazoline groups at the surface of cellulose fibers did not alert their ordered structure and crystallinity, as indicated by XRD and SEM results. Factors affecting the adsorption were systematically investigated. Under the optimized conditions, the HIMC sorbent exhibited high adsorption capacities of 105, 88 and 75 mg g−1 for Pt(IV), Pd(II) and Au(III), respectively. Besides, the metal ion adsorption process fitted by pseudo-second-order kinetic model and Langmuir adsorption isotherm. These results highlight the applicability of this carbohydrate-based sorbent for the selective recovery of precious metals from various matrices.

Evaluation of possible use of the macroporous ion exchanger in the adsorption process of rare earth elements and heavy metal ions from spent batteries solutions

In the paper Purolite S957 was used to determine the most effective conditions for the separation of La(III) and Ni(II) ions from acidic solutions. Preliminary studies of the sorption of La(III), Ce(III), Nd(III), Fe(III), Ni(II), Co(II), Cu(II) and Zn(II) mixture were carried out. The sorption process efficiency depends on the HNO3 concentration, contact time, initial metal concentration and temperature. Maximum sorption capacities amount to 0.46 ± 0.023 mmol/g for La(III) ions and 0.38 ± 0.019 mmol/g for Ni(II). To study the kinetics and process mechanism, the pseudo-first order, pseudo-second order equations, Weber-Morris intraparticle diffusion and Boyd models were applied. The equilibrium was described using the Langmuir, Freundlich and Temkin isotherm models. The desorption studies were also carried out. The morphology of ion exchanger was analyzed using scanning electron microscopy, optical microscopy and atomic force microscopy. The interactions of metals with the ion exchanger were confirmed by the attenuated total reflectance Fourier transform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy before and after the sorption process. Furthermore, the point of zero charge of Purolite S957 was determined. The obtained results can be used to assess the potential of ion exchanger application for recovery of rare earth elements and heavy metals from spent nickel-metal hydride batteries.

Preparation of anionic-cationic co-substituted hydroxyapatite for heavy metal removal: Performance and mechanisms

Sodium, silicate and carbonate ions co-substituted hydroxyapatite adsorbent (Na-SiCHAP) was prepared by sonochemistry coprecipitation. The effect of a variety of parameters on the adsorption of Pb2+ and Cd2+ by Na-SiCHAP were performed. The adsorption process of heavy metal ions was found to follow the pseudo-second-order kinetic equation and Langmuir adsorption model. The maximum absorption capacity (Qm) of Na-SiCHAP for Pb2+ and Cd2+ ions in 303 K were 698.68 and 129.60 mg g−1 according to the Langmuir adsorption model, respectively. The thermodynamic parameters (ΔG0 <0, ΔS0 >0, ΔH0 >22kJ·mol-1) indicated that the absorption of Pb2+ and Cd2+ on the Na-SiCHAP was spontaneous and endothermic, and the Na-SiCHAP adsorbed mainly via chemical adsorption. Ion exchange of Pb2+ and Cd2+ for Ca2+ and Na+ was one of the principal mechanisms, followed by precipitation and electrostatic interactions. Furthermore, the well stability properties of the Na-SiCHAP adsorbent were confirmed by recycling assays. These data indicate that Na-SiCHAP may be a good adsorbent for the rapid removal of heavy metal ions from aqueous solutions.

Preparation of acrylamide/acrylic acid cellulose hydrogels for the adsorption of heavy metal ions

Modified cellulose hydrogels were prepared by blending and cross-linking with acrylamide and acrylic acid. The structure of hydrogels was characterized and analyzed with fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Under the optimized conditions, the maximum absorption capacity in modified cellulose hydrogels of Cu (II), Pb (II) and Cd (II) ions were 157.51, 393.28 and 289.97 mg/g, respectively. In addition, the metal ion adsorption process accorded with pseudo-second-order rate equation and Langmuir adsorption isotherm. Based on the microstructure analysis and adsorption kinetics, the adsorption mechanisms such as physical, chemical, and electrostatic interactions are discussed. The adsorption process was controlled by the ion-exchange mechanism.

Comparative study of uranium and thorium metal ion adsorption by gum ghatti grafted poly(acrylamide) copolymer composites.

Uranium and thorium ions were selectively removed from aqueous solution using synthesized gum ghatti grafted poly(acrylamide) gum-g-poly(AAm) composite. A gamma radiation induced free radical copolymerization technique was used to synthesize the copolymer composite of gum-g-poly(AAm). Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the graft copolymer gum-g-poly(AAm). The adsorption of uranium ions and thorium ions using the gum-g-poly(AAm) copolymer composites has been investigated in batch mode. The adsorptive characteristics were investigated by varying the pH, concentration and time for both ions. The adsorption method depends on the pH of each metal ion, and the highest adsorption percentage was achieved at pH 6.0. The adsorption statistics were justified by isotherm, kinetic and thermodynamic models. The Langmuir adsorption model was revealed to be the best fitted monolayer arrangement, with a maximum adsorption capacity of 367.65 mg g−1 for the uranium ions and 125.95 mg g−1 for the thorium ions. The adsorption of metal ions occurred by the ion exchange process, which was specified through the rate controlling step with a best-fitted pseudo-second order kinetic rate model. Thermodynamic analysis shows that the ΔH and ΔS values for the uranium ions and thorium ions were positive. The negative ΔG values decreased with an increase in temperature, suggesting that the metal ion adsorption process was endothermic and spontaneous in behaviour.

Application of oak powder/Fe3O4 magnetic composite in toxic metals removal from aqueous solutions

In this study, the capability of a magnetic composite of oak powder/Fe3O4 (OP/Fe3O4) for the adsorption of lead, cobalt, and nickel ions from aqueous solutions was examined. Characteristics and structure of oak powder (OP) and OP/Fe3O4 magnetic composite were explored by FTIR, SEM, TGA-DTG, VSM, and XRD analysis. The XRD results showed that OP/Fe3O4 magnetic composite and OP were in crystalline form. Kinetic behavior of adsorption process was studied using pseudo-first-order, pseudo-second-order, and Elovich models. Results indicated that the pseudo-second-order model (R2 > 0.999) can better describe the kinetic behavior of the metal adsorption process. Equilibrium behavior of the adsorption process was also tested using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Scatchard isotherm models. The results revealed that the adsorption equilibrium data for three metals match with the Freundlich isotherm model (R2 > 0.99). This indicates the effectiveness of heterogeneous surfaces in comparison with homogeneous ones in the adsorption process of metal ions. Moreover, the results showed that the adsorption process of metal ions with the OP/Fe3O4 magnetic composite is physical. Finally, negative values of enthalpy and entropy indicated that the process of the metal ion adsorption is spontaneous and exothermic.