Adsorption Mechanism Of Ions Research Articles

Oxygen Ion Adsorption Studies on La10Si6O27 (001) Surface with DFT Calculation for SOFC Electrolyte

The apatite-type material La10-xSi6O27-1.5x (LSO) has promising future as electrolyte in SOFC for its high ionic conductivity [1-3]. In this work, ab-initio calculation based on density functional theory (DFT) [4] has been used to investigate the oxygen ion adsorption mechanisms and energy at different sites on the LSO (001) surface. The oxygen ion migration channel can be predicted using the results of adsorption energies on various sites. The most stable adsorption is shown at the hollow between La and O (located away from O-Si Tetrahedron), thus it should be a candidate channel of oxygen ion migration. Furthermore, the electronic properties, including the Fermi energy level, bond strength and length, have been changed with the ion adsorption, and the electrons transition features were obtained by density of states analysis. The calculated results also imply that LSO could be employed as possible electrolyte material due to its low formation and migration energies for the oxygen ion. Keywords: Apatite electrolyte, Ab initio calculations, DFT, SOFC, ion adsorption. Reference: 1. H. Yoshioka, Y. Nojiri, S. Tanase, Solid State Ionics 179 (2008) 2165-21692. Guangchao Yin, et al, Journal of Alloys and Compounds 586 (2014) 279–2843. Susumu Nakayama, et al, Ceramics International 40 (2014) 1221–12244. T.Q. Nguyen et al. Applied Surface Science, 288 (2014) 244–250 Figure 1

Effect of solvent addition on bitumen–air bubble attachment in process water

Bitumen–air bubble attachment is an essential element for bitumen recovery from oil sands by flotation. Effect of solvent addition to bitumen on bitumen–air bubble attachment in an industrial process water was investigated by determining the minimum time required to achieve the bitumen–air bubble attachment, known as induction time. Proper addition of solvent to bitumen significantly reduced the induction time of bitumen–air bubble attachment, more so for naphtha than for toluene and reaching optimal at 10wt% solvent added to bitumen. The measurement of bubble coalescence time and total organic carbon content in the resulting process water revealed a critical role in bitumen–air bubble attachment of air bubble interfacial properties controlled primarily by surfactants in the process water and water chemistry. Increasing the solvent addition to bitumen led to an increased migration of natural surfactants to the bitumen–water interface. At a given solvent dosage, more surfactants adsorbed at toluene–diluted bitumen–water interface than at naphtha–diluted bitumen–water interface. Interestingly, zeta potentials of diluted bitumen droplets in the process water exhibited a maximum at about 10wt% of solvent addition to bitumen for both toluene and naphtha. At an identical dosage of solvent, toluene–diluted bitumen in the tailings water possesses a more negative zeta potential than naphtha–diluted bitumen. Finally, a possible adsorption mechanism of ions and surfactants accumulating at the diluted bitumen–water interface under the impact of solvent addition is proposed.

Adsorptive efficacy analysis of lignocellulosic waste carbonaceous adsorbents toward different mercury species

Adsorptive efficacy of lignocellulosic waste char (LW-CHAR) and activated carbon (LW-AC) toward inorganic (Hg2+) and organic (MeHg+) mercury ions was studied. The LW-CHAR and LW-AC were, respectively, prepared by carbonization and KOH activation processes of lignocellulosic waste (LW) carried out at 700°C. The Hg2+ adsorption onto the LW-CHAR was lower than LW-AC, however, an opposite result was observed for the MeHg+ indicating the nature of the surface interactions of both mercury ions to respective adsorbent surfaces was significantly different. The adsorption data analysis of both mercury ions was found however to only follow the Langmuir isotherm and pseudo-second order kinetic models whereby a combination of chemisorption and diffusional process was the governing mercury ions adsorption mechanism.

The mechanism of ion exchange and adsorption coexist on medium–low concentration ammonium–nitrogen removal by ion-exchange resin

In this study, the removal of medium–low concentration ammonium–nitrogen () from waters and wastewaters on D113 resin was investigated with respect to pH, initial concentration, temperature and contact time. The equilibrium of on D113 resin reached in 20–30 min. The process of removal by D113 resin fitted Langmuir isotherm well. The pseudo second-order kinetic and intra-particle diffusion models were used to investigate the kinetic data of on D113 resin. The desorption solution can be returned to production after pretreatment. The mechanism of removal of by D113 resin was coexistence of adsorption and cation exchange. When the dosage of D113 resin was 5 g L−1, pH 6, contact 30 min at room temperature, initial concentration being 116 mg L−1 in rare earth metallurgical wastewater was reduced to 13 mg L−1 after adsorption treatment.

Study on removal behavior and separation efficiency of naturally occurring bentonite for sulfate from water by continuous column and batch methods

The removal of sulfate using Jordanian bentonite has been investigated in this study. The surface of the bentonite was modified by calcinations at different temperature. The batch experiments of the equilibrium studies were carried out under different operating conditions. Kinetic modeling for the removal of sulfate ion was investigated using a pseudo-second-order, intraparticle diffusion and Elovich kinetic models to predict the rate constants and equilibrium capacities for this process using column reactor. It was found that intraparticle diffusion of the sulfate ion is the rate limiting step and played an important role in the mechanism of sulfate ion adsorption depending on the obtained activation energy, which was 32.8 kJ/mol. Also, the sorption isotherm analyzed using both the Langmuir and Freundlich models as a function of temperature. The isothermal data found to be fitted Langmuir model rather than Freundlich model. The positive value of ΔH (15.2 kJ/mol) indicated that the adsorption of sulfate ions on the adsorbent was an endothermic process and the positive value of ΔS (22.1 J/mol.K) indicated that the adsorption is favorable with small positive value of the free energy (ΔG).

Adsorption kinetic parameters of Fe3+ and Ni2+ ions by gyrolite

In this work the adsorption kinetic parameters for Fe 3+ and Ni 2+ ions by gyrolite are presented. Additionally, the adsoption mechanism was described by using pseudo first order and pseudo second order equations. It was determined that the adsorption capacity of gyrolite and intrusion of heavy metals ions in its structure depends on reaction time and the pH value of adsorptive. It was observed that the incorporation of Fe 3+ ions occurs more intensive than Ni 2+ ions. It was found that in the acidic solution the intrusion of Fe 3+ ions into gyrolite structure proceeds by two types of chemical reaction mechanisms: substitution and addition. Meanwhile, nickel ions were participated only in substitution reaction: gyrolite-Ca 0 + Me x+ ↔ gyrolite-Me 0 + Ca 2+ . It was observed that the pseudo second order model fit well for iron and nickel ions adsorption mechanism. It was estimated that the adsorption reactions are not reversible process and the crystal structure of gyrolite is stable. Moreover, synthetic adsorbent and the products of sorption were characterized by XRD, STA and FT-IR methods. DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5735

Preparation and heavy metal ion adsorption behavior of novel supermagnetic nanocomposite based on thiacalix[4]arene and polyaniline: Conductivity, isotherm and kinetic study

Supermagnetic nanocomposite of polyaniline thiacalix[4]arene (Fe3O4@PANI-AmAzoTCA[4]) was prepared by coprecipitation of aniline-diaminoazo thiacalix[4]arene copolymer (PANI-AmAzoTCA[4]) and in-situ generated Fe3O4 nanoparticles. Structural, morphological and magnetic properties of the nanocomposite was studied by nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Atomic force microscopy (AFM) and vibrating sample magnetometer (VSM), and further used for the removal of metal ions from aqueous solutions. The influence of pH, contact time and initial metal ion concentration on the adsorption efficiency was investigated. The heavy metal ion adsorption mechanism of the supermagnetic adsorbent was clarified through adsorption capacity investigation from the isotherm and kinetic point of view. The related correlation coefficient for each isotherm-model showed that the equilibrium adsorption behavior of Cd(II) ion can be applied to Langmuir model with the maximum adsorption capacity of 285.7mgg−1 and for Cu(II), Co(II) and Cr(III) ions to Temkin model with the equal maximum adsorption capacity of 312.5mgg−1. The experimental data of all metal ions fitted well with the pseudo-second-order rate equation. The four-probe technique revealed that metal ion adsorption resulted in a rather significant enhancement of conductivity with a 100 order of magnitude for the supermagnetic nanoadsorbent due to charge delocalization of absorbed metal ions.

Adsorption of Selenite Ions onto Poly(1,8-diaminonaphthalene) Synthesized by Using Ammonium Persulfate

In the present work, poly(1,8-diaminonaphthalene) (poly(1,8-DAN)) was synthesized by chemical oxidation of 1,8-diaminonaphthalene (1,8-DAN) monomer with ammonium persulfate (APS) oxidant and it was used in the adsorption of selenite ions. The polymer samples synthesized at various molar ratios of 1,8-DAN to APS were characterized by FTIR analysis and they were used in the adsorption experiments. The effects of initial acidity, the molar ratio, and initial selenium concentration on the adsorption behavior of poly(1,8-DAN) were examined by using batch adsorption technique. It was found that selenite was adsorbed onto poly(1,8-DAN) in strong acidic conditions (3-8 M HCl). The experimental adsorption data were applied to the Langmuir and Freundlich isotherms. The adsorption capacities of the polymer samples at the molar ratios of 1/0.5 and 1/2 were calculated as 75.19 and 45.05 mg Se/g, respectively. It was estimated that the adsorption mechanisms of selenite ions onto poly(1,8-DAN) were governed by electrostatic interaction (>NH2+SeOCl3−) and piazoselenol type binding (-N=Se=N-).

Adsorption of nitrate and nitrite ions onto carbonaceous material produced from soybean in a binary solution system

In this study, soybean (SB) was treated with calcium chloride, hydrochloric acid, and calcination (400, 600, 800, and 1000°C) to introduce chloride ions onto the SB surfaces (SB400, SB600, SB800, and SB1000, respectively). The properties of the adsorbents (pH of the solution, acidic functional group, and basic functional group) were investigated. The adsorption of nitrate and nitrite ions onto SB surfaces at different temperatures was evaluated. SB600 had the highest concentration of acidic functional groups (3.34mmol/g). The amount of nitrate and nitrite ions adsorbed onto SB600 in a binary solution system was lower than that in a single solution system. The amount of nitrate and nitrite ions adsorbed was closely related to the chloride ions. The adsorption mechanism of nitrate and nitrite ions onto SB600 mainly involved an ion exchange (correlation coefficient=0.993). Moreover, chloride ions affected the adsorption process. The adsorption isotherm data using SB600 were fitted to both the Langmuir and Freundlich equations. The amount of nitrate and nitrite ions adsorbed increased with increasing temperature. The adsorption equilibriums of nitrate and nitrite ions onto SB600 were obtained after 24 and 16h, respectively. The experimental data fit the pseudo-second-order model better than the pseudo-first-order model. Thus, SB600 is useful for the adsorption of nitrate and nitrite ions in a binary solution system.

Application of surface complexation models to anion adsorption by natural materials

Various chemical models of ion adsorption are presented and discussed. Chemical models, such as surface complexation models, provide a molecular description of anion adsorption reactions using an equilibrium approach. Two such models, the constant capacitance model and the triple layer model, are described in the present study. Characteristics common to all the surface complexation models are equilibrium constant expressions, mass and charge balances, and surface activity coefficient electrostatic potential terms. Methods for determining parameter values for surface site density, capacitances, and surface complexation constants also are discussed. Spectroscopic experimental methods of establishing ion adsorption mechanisms include vibrational spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray absorption spectroscopy, and X-ray reflectivity. Experimental determinations of point of zero charge shifts and ionic strength dependence of adsorption results and molecular modeling calculations also can be used to deduce adsorption mechanisms. Applications of the surface complexation models to heterogeneous natural materials, such as soils, using the component additivity and the generalized composite approaches are described. Emphasis is on the generalized composite approach for predicting anion adsorption by soils. Continuing research is needed to develop consistent and realistic protocols for describing ion adsorption reactions on soil minerals and soils. The availability of standardized model parameter databases for use in chemical speciation-transport models is critical.

Adsorption Characteristics of Multi-Metal Ions by Red Mud, Zeolite, Limestone, and Oyster Shell

In this study, the performances of various adsorbents—red mud, zeolite, limestone, and oyster shell—were investigated for the adsorption of multi-metal ions (Cr3+, Ni2+, Cu2+, Zn2+, As3+, Cd2+, and Pb2+) from aqueous solutions. The result of scanning electron microscopy analyses indicated that the some metal ions were adsorbed onto the surface of the media. Moreover, Fourier transform infrared spectroscopy analysis showed that the Si(Al)-O bond (red mud and zeolite) and C-O bond (limestone and oyster shell) might be involved in heavy metal adsorption. The changes in the pH of the aqueous solutions upon applying adsorbents were investigated and the adsorption kinetics of the metal ions on different adsorbents were simulated by pseudo-first-order and pseudo-second-order models. The sorption process was relatively fast and equilibrium was reached after about 60 min of contact (except for As3+). From the maximum capacity of the adsorption kinetic model, the removal of Pb2+ and Cu2+ were higher than for the other metal ions. Meanwhile, the reaction rate constants (k1,2) indicated the slowest sorption in As3+. The adsorption mechanisms of heavy metal ions were not only surface adsorption and ion exchange, but also surface precipitation. Based on the metal ions’ adsorption efficiencies, red mud was found to be the most efficient of all the tested adsorbents. In addition, impurities in seawater did not lead to a significant decrease in the adsorption performance. It is concluded that red mud is a more economic high-performance alternative than the other tested adsorption materials for applying a removal of multi-metal in seawater.

Kinetic model investigation on lead(II) adsorption using silica-based hybrid membranes

With the rapid development of lead refineries and the wide application of leaded work in electrical industry, lead(II) pollution has deserved much attention. In this study, the kinetic models of lead(II) adsorption onto silica-based hybrid membranes as solid adsorbents were studied. To study the adsorption mechanism of heavy metal ions on these hybrid adsorbents, the experimental data were linearly fitted using six typical two-parameter kinetic equations (i.e. Lagergren pseudo-first-order and pseudo-second-order, Ritchie second-order and modified second-order, Elovich, as well as intraparticle diffusion models). It was found that the experimental results fitted well with Lagergren pseudo-second-order model, Elovich, and intraparticle diffusion models. These findings are very useful in the design and optimization of silica-based hybrid membranes for lead(II) removal from water by adsorption.

Fast, selective adsorption of Cu2+ from aqueous mixed metal ions solution using 1,4,7-triazacyclononane modified SBA-15 silica adsorbent (SBA-TACN)

A new SBA-15 supported 1,4,7-triazacyclononane modified mesoporous silica adsorbent (SBA-TACN) has been synthesized using post grafting route and has thoroughly been characterized by small angle X-ray scattering (SAXS), N2 adsorption–desorption measurements, Fourier-transform infrared (FT-IR), solid-state 29Si MAS and 13C CP MAS NMR spectroscopy, transmission electron (TEM) and scanning electron microscopy (SEM), elemental analysis (EA) and thermogravimetric analysis (TGA). The synthesized material shows excellent copper (II) ion adsorption selectivity at pH 5 in mixed metal ion solution containing Cu2+, Cr3+, Ni2+, Co2+ and Li+. The copper ion adsorption capacity of the SBA-TACN can reach a maximum value of 0.67mmol/g. Possible adsorption mechanism of metal ions on SBA-TACN has been discussed. The adsorbent can be readily regenerated by HNO3–NH3 treatment.

An adsorption diffusion model for removal of copper (II) from aqueous solution by pyrolytic tyre char

Kinetic and equilibrium adsorption experiments have been carried out in order to investigate the removal and diffusion mechanism of copper (II) ions onto pyrolytic tyre char obtained from an industrial plant. The experimental equilibrium data have been analyzed using Langmuir, Freundlich, and Redlich–Peterson isotherm models. The accuracy of the fit of the isotherm models to experimental equilibrium data was assessed using the sum of squares error (SSE) analysis. Modeling of the adsorption isotherm showed that Redlich–Peterson expression yields the best fit between experimental and predicted data. The batch kinetic data obtained at different concentrations of copper ions in the solution and also different masses of tyre char were analyzed using the intraparticle diffusion model. In the intraparticle diffusion model plots, three distinct linear sections were obtained for every batch operation. An intraparticle diffusion rate parameter, k is derived from the plots of copper adsorbed vs. the square root of time. The data indicated the potential of pyrolytic tyre char for the removal of copper from aquatic effluents and the adsorption mechanism of copper ions onto tyre char can be described by intraparticle diffusion model.

Introduction of Adsorption Mechanisms Researches on Organic Chemicals and Metallic Ions on CNTs

Carbon nanotubes (CNTs) have aroused widespread attention due to their high potential sorption capability for chemical pollutants. This review summarizes the adsorption mechanisms of organic chemicals and metallic ions with CNTs in aquatic environment and the factors affecting the adsorption. For a better understanding of the mechanism, future research works on combining the chemical experience and molecular dynamics (MD) is recommended.

Dynamic adsorption behavior and mechanism of transition metal ions on silica gels functionalized with hydroxyl- or amino-terminated polyamines

The metal ion adsorption behaviors of five silica gel adsorbents functionalized with hydroxyl- or amino-terminated polyamines (SiO2-EA, SiO2-DEA, SiO2-EDA, SiO2-DETA, and SiO2-TETA) were investigated. Four transition metal ions Au3+, Ag+, Cu2+ and Hg2+ were included in the detailed static and dynamic studies. All five resins showed better affinity for Au3+ and Ag+ than Cu2+ and Hg2+. Particularly for Au3+, the adsorption capacities of the five resins were as high as 1.27, 1.17, 1.58, 1.53 and 1.43mmoLg−1, which suggest very strong metal ion chelating ability. In the static experiments, the utilization ratio of N of amino-terminated samples decreased as the number of N increased. It was found in the dynamic adsorption experiments that the adsorption capacities did not always increase with the number of amino groups. The breakthrough curves obtained from the adsorption bed demonstrated that the mass transfer resistance not only depended on the surface area of silica gel resins, but also on the properties of metal ions. Contrary to Cu2+ and Hg2+, silica gels with larger surface area showed smaller mass transfer resistance for Au3+. Adsorption kinetics revealed that the adsorption process was governed by film diffusion and followed the pseudo-first-order model for Au3+ and pseudo-second-order model for Hg2+. Besides, the relationship between the structure and functional groups and the adsorption mechanism were also studied.

Study of Adsorption Mechanism of Heavy Metals onto Waste Biomass (Wheat Bran)

In this study, raw wheat bran (R-WB), a type of waste biomass (WB) was treated with Pectinase PL (P-WB), and the properties (yield percentage, carboxy group surface concentration, the solution pH, and specific surface area) of R-WB and P-WB were investigated. The surface concentration of carboxy groups on R-WB (3.56 mmol/g) was greater than that of P-WB (2.11 mmol/g). In contrast, the specific surface area of P-WB (24.98 m²/g) was greater than that of R-WB (3.25 m²/g). In addition, the adsorption of cadmium and lead ions to WB was evaluated. Adsorption of the heavy-metal ions reached equilibrium within 9 h, and the experimental data was fitted to a pseudo-second-order model. More heavy-metal ions were adsorbed onto R-WB than onto P-WB. The correlation coefficient between the amount of ions adsorbed and the number of carboxy groups or pectin exceeded 0.884 and 0.975, respectively. This study indicated that wheat bran was useful for the removal of cadmium or lead ions from aqueous solutions. The adsorption mechanism of cadmium and lead ions to WB was associated with presence of carboxy group in pectin.

Effect of Surface Property of Activated Carbon on Adsorption of Nitrate Ion

In this study, the removal of acidic functional groups and introduction of basic groups/sites on activated carbons (ACs) by outgassing and ammonia gas treatment were respectively carried out to enhance the nitrate ion adsorption in aqueous solution. Then, the relationships between nitrate ion adsorption and solution pH as well as surface charge of AC were investigated to understand the basic mechanisms of nitrate ion adsorption by AC. The result showed that the nitrate ion adsorption depended on the equilibrium solution pH (pHe) and the adsorption amount was promoted with decreasing pHe. The ACs treated by outgassing and ammonia gas treatment showed larger amount of nitrate ion adsorption than that by untreated AC. These results indicated that, since basic groups/sites could adsorb protons in the solution, the AC surface would be charged positively, and that the nitrate ion would be electrically interacted with positively charged carbon surface. Accordingly, it was concluded that basic groups/sites on the surface of AC could promote nitrate ion adsorption.

Two-step self-assembly of iron oxide into three-dimensional hollow magnetic porous microspheres and their toxic ion adsorption mechanism

Hollow magnetic porous Fe(3)O(4)/α-FeOOH microspheres, with abundant surface hydroxyl groups and carbonate-like species, were prepared using a simple template free solution method. The obtained magnetic microspheres were characterized by field emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption isotherms, vibrating sample magnetometry and X-ray diffraction. A two-step self-assembly mechanism for the microspheres was proposed based on the morphology of the products produced with different reaction times and the X-ray diffraction of the raw product grown at the initial stage. The toxic ion adsorption properties of the microspheres were investigated for As(V), Cr(VI), Cd(II) and Hg(II) ion removal. The adsorption mechanism was studied by an X-ray photoelectron spectrometer and Fourier transform infrared absorption spectroscopy . The results suggest that both the surface hydroxyl groups and the carbonate-like species participated in the ion-exchange process.

Adsorption kinetics, mechanism, isotherm, and thermodynamic analysis of copper ions onto the surface modified agricultural waste

The adsorption of copper ions onto the surface modified Strychnos potatorum seeds (SMSP) in a batch adsorption system has been studied. Kinetics, mechanism, isotherm, and thermodynamic parameters have been estimated. Adsorption kinetics of copper ions onto the SMSP follows a pseudo‐second order kinetic model. Adsorption mechanism was explained with the intraparticle diffusion model, Boyd kinetic model (BKM), and Shrinking core model (SCM). Adsorption process was found to be controlled by both intraparticle diffusion and film diffusion. The diffusivity values were estimated from the BKM and SCM. Adsorption isotherm data agreed well with the Freundlich adsorption isotherm model, which indicates the multilayer adsorption of copper ions onto the SMSP. The maximum monolayer adsorption capacity of the SMSP was found to be 248 mg of copper ions/g of SMSP. Adsorption thermodynamic studies show that the adsorption of copper ions onto the SMSP was spontaneous and exothermic in nature. © 2012 American Institute of Chemical Engineers Environ Prog, 33: 28–37, 2014