Adsorption Mechanism Of Ions Research Articles

Characteristics of Amorphophallus campanulatus Modified Starch as Novel Adsorbent for Nickel and Cadmium Removal from Aqueous Solution

Novel adsorbents are succesfully manufactured from Amorphophalluscampanulatus (Porang or Suweg or Elephant Foot Yam or Foot Yam) starch. The experiment focused on modifiying the starch with citric acid and detailing those morphologies and chemical bonds. Analysis with FTIR and SEM showed that PTM (modified porous porang starch) sample is the best adsorbent which has most stable of chemical bonding and also has the most pores that influence an adsorption phenomena. Isotherm adsorption analysis showed that the adsorption mechanism of Cd and Ni ions onto the suface of PB, PT and PTM followed the Temkin and Langmuir isotherm adsorption. Adsorption ability of PTM is the best than the other PB and PT which can adsorps 256,23 mg Cd/g PTM and 87,45 mg Ni/g PTM in 500 ppm synthetic aqueous solution

Adsorption behaviours and mechanisms of heavy metal ions’ impact on municipal waste composts with different degree of maturity

ABSTRACTComposting may change the adsorption characteristics and mechanisms of organic materials due to their differences in organic chemical functional groups and surface structures. The adsorption properties of heavy metals onto the municipal solid waste compost (MSW-C) and its secondary fermentation form (MSW-SC) were comparatively investigated in single, binary and multiple solutions by batch experiments. In the single-metal system, the maximum adsorption capacities of Cu, Zn, Cd and Ni onto MSW-SC were 29.2, 26.3, 38.1 and 22.0 mg g−1, respectively, and showed higher than that of MSW-C. The adsorption fitted best with the pseudo-second-order kinetics and Langmuir isotherms. The competitive adsorption results indicated that the composts exhibited good selectivity in the adsorption of Cu over Cd, Zn and Ni; thus, for the quaternary-metal systems, the adsorption sequence was Cu > Zn > Cd > Ni. Humic acid content, cation exchange capacity and surface area were increased following the secondary composting. FTIR analysis indicated amine and aromatic compounds were main binding sites accounting for metal sorption. SEM–EDX analysis suggested that the MSW-SC had rough surfaces and stronger adsorption capacity. Decreasing percentage of exchangeable metals was found in the metal-loaded MSW-SC based on a speciation analysis. This study highlights the interactive impacts of different metals during adsorption by compost with different maturity, the secondary composting process was a multifunctional improvement of sorption characteristics and MSW-SC was developed to be a highly efficient biosorbent.

Ionic hydration structure, dynamics and adsorption mechanism of sulfate and sodium ions in the surface of calcium silicate hydrate gel: A molecular dynamics study

Molecular dynamics was utilized to investigate ionic structure, dynamics and adsorption behaviors of the sulfate and sodium ions highly solvated in the nanometer channel of calcium silicate hydrate (C–S–H) with two different Ca/Si ratios. Due to H-bond connection from silicate oxygen sites and attraction of surface calcium ions, a stable adsorption layer of water molecules was formed in the vicinity of the hydrophilic silicate channel: clear layered arrangements, strong orientation preferences and extremely low diffusion coefficients. Furthermore, the adsorption mechanisms differ for the sulfate and sodium ions confined in the gel pore of C–S–H: while sodium ions are connected onto the non-bridging oxygen sites by Na-Onb bonding, the sulfate ions can be attracted by the calcium ions, leading to the aggregation of Ca-SO4 ionic pairs. In the surface region, since the hydration shell of the solvated ions are partly substituted by the adsorbed water molecules, surface calcium ions and silicate oxygen sites, the diffusion of these ions is dramatically immobilized. Both the adsorbed Na+ and SO42− ions display extended exchange time for their solvation shells and longer residence time for their ionic clusters, as compared with those in aqueous solution. Besides, the increase in the surface Ca/Si ratio disturbs the local ordered arrangements and reduces the stability of the hydration layer. At high Ca/Si ratio, the highly solvated calcium ions contribute to the transformation from the outer adsorbed sulfate ions to the inner adsorbed species, enhancing the anions immobilization near the silicate surface.

Adsorption mechanisms of metal ions on the potassium dihydrogen phosphate (1 0 0) surface: A density functional theory-based investigation

The adsorption of metal ions (K+, Na+, Ca2+, Cu2+, Al3+, Cr3+) on the (1 0 0) surface of potassium dihydrogen phosphate (KDP) has been studied using density functional theory (DFT). Calculation results show that all the investigated metal ions can be spontaneously adsorbed on the surface with negative adsorption energies. The adsorption stability increases in the order of Na+ < K+ < Cu2+ < Ca2+ < Al3+ < Cr3+, and shows a consistent trend as the adsorbed metal ion valence (monovalent < divalent < trivalent). Three types of stable adsorption configurations are observed, corresponding to three different bonding mechanisms. Na+, K+ and Ca2+ ions with a large radius can form two ionic bonds and one weak covalent bond with the O and H atoms respectively. In addition, the medium-sized ion of Cu2+ forms two covalent bonds with the O and H atoms. Furthermore, Al3+ and Cr3+ ions with the smallest radius form two metal-oxygen and one metal-hydrogen covalent bonds with the surface, making one H–O bond broken. Compared with other metal ions, Al3+ and Cr3+ have the strongest interactions with the surface, which can be explained by the significant electron transfer and more stable covalent bond formations between these two ions and the surface.

STUDYING ADSORPTION PECULIARITIES OF ULTRADISPERSED ALUMINUM NITRIDE POWDER BEFORE AND AFTER WATER TREATMENT

The paper presents the results obtained when studying the adsorption and structural peculiarities of aluminum nitride nanopowder interaction with water, particularly the morphology and phase composition of oxidation products. Powder surface areas and porosities are calculated. The peculiarities of the adsorption isotherms of the investigated samples are analyzed before and after interaction with water in terms of their correspondence to a certain type according to the recommendation of the International Union for Pure and Applied Chemistry (IUPAC), as well as to a certain porosity type, which is necessary for the understanding of their further application. The mechanism of aluminum nitride powder and water interaction is discussed. It is shown that aluminum nitride interacts with water by the ion-adsorption mechanism that leads to the formation of porous agglomerates consisting of needle and platelet shaped aluminum oxyhydroxide nanoplates connected by contacts with pores 55 A in diameter. Specific surface area increases from 48 to 115 m2/g. It is also found that phase composition changes as a result of AlN nanopowder interaction with aqueous environment, and interaction products are represented by AlO(OH) and Al(OH)3 phases.

Preparation and characterization of porous cationic poly[styrene‐co‐(N,N′‐dimethylaminoethyl methacrylate)] nanoparticles and their adsorption of heavy metal ions in water

AbstractUsing styrene (St) and N,N′‐dimethylaminoethyl methacrylate (DMAEMA) as raw materials, monodispersed P(St‐co‐DMAEMA) nanoparticles (NPs) were first prepared via semi‐continuous emulsion polymerization, and using a stepwise acid–alkali post‐treatment, porous P(St‐co‐DMAEMA) NPs were then obtained and used to adsorb heavy metal ions in aqueous phase. Results showed that the post‐treatment conditions including temperature, initial pH and time of acid–alkali treatment had significant effects on the morphology of the porous P(St‐co‐DMAEMA) NPs, with higher temperature, more extreme pH condition and longer treatment time resulting in larger pores and volume swelling ratio. Under the optimized acid–alkali post‐treatment conditions (60 °C, acid treatment at pH = 4.0 for 1 h and then alkali treatment at pH = 10.0 for 1 h), the obtained porous NPs had nearly 15 times the surface area and 1.5 times the amount of surface amino groups than the corresponding solid NPs. An analysis of the mechanism of metal ion adsorption on the porous NPs indicated that the adsorbed amount of metal ions was the result of synergistic effect of physical and chemical adsorption, which was closely related to the porous NP surface area, amount of surface of amino groups and the volume of the ions. © 2018 Society of Chemical Industry

Decontamination of Hg(II) from aqueous solution using polyamine-co-thiourea inarched chitosan gel derivatives

Ethylenediamine (EDA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) had been successfully introduced into the structure of thiourea (TC) modified chitosan (CS) by using formaldehyde as linkage, respectively. The resulted materials, TC-CS, TC-EDA-CS, TC-TETA-CS, and TC-TEPA-CS were characterized and employed as adsorbents in batch experiment for the Hg(II) removal. We have found the modification enhanced the Hg(II) adsorption significantly in comparison with raw CS. Hg(II) adsorption amounts for all adsorbents increased gradually and reached maxima at pH≥4.0. The adsorption of Hg(II) achieved an equilibrium state within 12h with the process drove by the pseudo-second-order model. The ionic strength had no remarkable inhibition effect on Hg(II) adsorption. While the Hg(II) adsorption capacities of the adsorbents were strongly related with the modifier types and the length of the incorporating amino ligands. Langmuir model described Hg(II) adsorption well with the maximum adsorption capacities of prepared adsorbents in order of TC-EDA-CS (217.1mg/g)>TC-CS (164.8mg/g)>TC-TETA-CS (149.7mg/g)>TC-TEPA-CS (140.6mg/g) at room temperature. The FT-IR and XPS investigations implied that Hg(II) ion adsorption mechanism was characterized by a complexation reaction process. Adsorbents could be readily regenerated and had great reusability potential in Hg(II) ions capture from aqueous solution.

Preparation of 2-Aminothiazole-Functionalized Poly(glycidyl methacrylate) Microspheres and Their Excellent Gold Ion Adsorption Properties.

A new adsorbent(A-PGMA) has been synthesized via functionalizing poly(glycidyl methacrylate) microsphere with 2-aminothiazole and used to adsorb gold ions from aqueous solutions. The adsorbent was characterized by X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Zeta potential, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The influence factors such as the pH value of the solution, the initial gold ion concentration and the contact time were examined. Simultaneously, the adsorption process of the gold ion on A-PGMA fitted well with the Langmuir and pseudo-second-order models, respectively. The results showed that the maximum adsorption capacity was 440.54 mg/g and the equilibrium time of adsorption was about 3 h under pH 4. Moreover, the adsorbent has a high reusability after five cycles and good selectivity from coexisting ions, including Zn(II), Mg(II), Cu(II), Ge(IV) and B(III). The adsorption mechanisms of gold ions were ion exchange and chelation between the sulfur and nitrogen groups on the surface of A-PGMA and AuCl4−. Therefore, the adsorbent has a great potential for adsorption of gold ions from aqueous solutions.

Impedance spectroscopy as a tool to monitor the adsorption and removal of nitrate ions from aqueous solution using zinc aluminum chloride anionic clay

In this study, Zn3AlCl ionic clay was used to investigate the adsorption mechanism of the nitrate ions in solutions containing nitrate ions at different contact time. The clay was synthesized by coprecipitation method at room temperature, and this sample was characterized by XRD, Fourier transform-infrared (FT-IR) and inductively coupled plasma (ICP). This sample was crystallized in a rhombohedral symmetry (Space group: R-3 m). Impedance spectroscopy was used as a tool to evaluate and monitor the adsorption process at different contact time 5; 10; 20; 30; 60 min and the clay alone. The impedance measurement was well analyzed and fitted with an equivalent circuit containing both (R//CPE) connected in series. Furthermore, the σac conductivity was also investigated as a function of frequency. It was analyzed and fitted using double power law: σac(ω)=σdc+Aωs1+Bωs2,(0≤s1≤1and0≤s2≤1).This study reveals the existence of two relaxation processes with different relaxation times, which could be attributed to the grain and grain boundaries, and exhibit high values of dielectric constant at low frequencies.

Adsorption kinetics and mechanisms of copper ions on activated carbons derived from pinewood sawdust by fast H3PO4 activation.

Two kinds of pinewood sawdust activated carbon adsorbents were prepared by fast activation with H3PO4 in a spouted bed, and the application in adsorption of copper ions was investigated. With only 3min of activation time, the BET surface area of activated carbons reached 1537.5m2/g for impregnation mass ratio of H3PO4 to sawdust at 1:1 and activation temperature of 500°C (IR1-500), whereas it was 1750.7m2/g for the impregnation ratio at 4:1 and activation temperature of 800°C (IR4-800). The pseudo second-order reaction kinetics well describes the experimental adsorption of copper ion in this study, indicating chemisorption dominated in the process. By the C1s spectrum, activated carbons from IR1-500 contained more carboxyl groups (-COOH) and carbonyl groups (C=O), which played an important role in copper ions adsorption. In addition, it was found that the P-containing groups (metaphosphates) also involved in the adsorption of copper ion.

Efficient adsorption of cobalt on chemical modified activated carbon: characterization, optimization and modeling studies

Herein, granular activated carbon (GAC) was modified chemically with sodium dodecyl sulfate (SDS) to prepare MGAC as an efficient adsorbent for removal of Co(II) ion from aqueous solution. The effect of different SDS concentrations and modification time on the adsorption performance was examined. The as-prepared adsorbent was characterized by FESEM and FT-IR techniques. Moreover, some parameters affecting the adsorption efficiency like solution pH, contact time, adsorbent dosages, initial metal ion concentrations, temperature and agitation speed on the adsorption efficiency were evaluated in a batch environment. Under same operational conditions, MGAC showed a much greater adsorption rate than GAC, due to synergistic effect between GAC and SDS. The equilibrium time was 90 min and the maximum adsorption capacity based on the Langmuir was found to be 51 mg/g. Experimental data were in good agreement with Langmuir and pseudo-second-order models. The mechanism of Co ion adsorption on MGAC followed ion-exchange and mono layer chemical adsorption. The adsorption process showed better performance at neutral pH and higher temperatures. Under optimized conditions, complete removal of 20 mg/L of Co(II) was obtained in the presence of 1.2 g/L of MGAC. Thermodynamic studies indicated the adsorption process was endothermic and spontaneous in nature. © 2018 Desalination Publications. All rights reserved.

Humic acid provenance influence to the adsorption capacity in uranium and thorium removal

It is common knowledge that humic acid is organic compound without certain chemical composition since it is derived from different organic materials. Further this raises question whether the different humic acid sample used could lead to different adsorbent properties e.g. adsorption capacity. To address the problem, this paper is aimed to clarify the relation between the provenances of humic acid and synthesized adsorbent properties especially adsorption capacities by quantitative and qualitative functional groups determination including discussion on their effect to the metal ion adsorption mechanism using three humic acid samples. Two commercial samples were derived from recent compost while the other extracted from tertiary carbonaceous mudstone strata.

Crustacean derived calcium phosphate systems: Application in defluoridation of drinking water in East African rift valley

Calcium phosphate adsorbents, derived from prawns and crabs shell biomass wastes have been developed using wet chemistry and low temperature treatment. The adsorbents were characterized by X-ray diffractometry and Fourier transform infrared spectroscopy. Batch adsorption test were carried out to investigate their effectiveness in adsorption of fluoride from ground and surface waters. Adsorption capacities were compared with bone char and synthetic hydroxyapatite (CCHA). Results indicate that prawns derived adsorbent (PHA) formed hexagonal structure with phases identifiable with hydroxyapatite while crabs based adsorbent (CHA) formed predominantly monoclinic structure with crystalline phase characteristic of brushite. Vibrational analysis and kinetic studies predicted defluoridation occurred mainly by ion exchange and ion adsorption mechanisms. Defluoridation capacity of the adsorbents was found to be superior compared to bone char and CCHA. CHA was the most effective with efficiencies above 92% and highest capacity of 13.6 mg/g in field water with fluoride concentration of 5–70 mg/L. PHA had highest capacity of 8.5 mg/g which was still better than 2.6 mg/g recorded by CCHA and bone char. Adsorption was best described by pseudo 2nd order kinetics. The findings indicate that crustacean derived calcium phosphate systems have better potential for defluoridation than traditional bone char and synthetic systems.

Experimental and Theoretical Studies on the Adsorption and Desorption Mechanisms of Chromate Ions on Cross-Linked Chitosan.

In this work, chitosan bead materials were modified by cross-linking with epichlorohydrin (EP) and glutaraldehyde (GA) for the removal of heavy metals in wastewater. Using these cross-linked chitosan materials, the dependence of adsorption of chromate anions on pH was investigated experimentally and theoretically. The experimental results show that the adsorption process of the chromate (Cr) ions greatly depends on the pH of the solution, with the chitosan modified by cross-linking being an efficient adsorbent for chromate. On the other hand, quantum chemistry calculations were conducted to find out the factor determining the pH dependence of the adsorption efficiency of chromate ions on the dimer chitosan molecule, and show results similar to those found in the experiment. Both the experimental and numerical results show that the total charge numbers of the adsorbent and the adsorbate species and their relative molecular geometries are crucial in determining the adsorption efficiency.

Effect of electrode charge balance on the energy storage performance of hybrid supercapacitor cells based on LiFePO4 as Li-ion battery electrode and activated carbon

Hybrid supercapacitors using asymmetric, LiFePO4 (LFP) lithium intercalation and electric double layer activated carbon (AC) electrodes combining the high energy battery ability and high power supercapacitor ability in one device are reported. In AC/Li half-cell, AC electrode has 44.5 mAh g−1 capacity and operative voltage > 2 V (Li/Li+) to exhibit supercapacitor-like ion adsorption mechanism. The cyclic voltammetry (CV) and charge/discharge (CD) analysis on AC||LFP hybrid cells with AC/LFP mass ratio, 0.33, 1.2, 1.93, and 3.19, show the transformation from a redox reaction dominated like in battery to a system in which both faradaic redox and the physical electrostatic adsorption processes forming electric double layer are fully balanced in terms of stored charges on both electrodes. The capacity analysis by discharge at different rates shows the high capacity of 125 and 70 mAh g−1 with steep fall at high rates for AC/LFP mass ratios 0.33 and 1.2, respectively. With a specific capacity of ~ 40 mAh g−1, the hybrid cells with AC/LFP mass ratios 1.93 and 3.19 show significant capacity retention at high rates. Optimized by charge balance, the AC||LFP hybrid cell exhibits a high specific energy of 35 Wh kg−1, a high specific power of 1.69 kW kg−1, and a long cycling life.

Investigation of adsorption mechanism of Fe, Cu, and Zn ions in extraction and preconcentration process on synthesized graphene oxide using an indole derivative

3-(chloro(2-methyl-1H-indol-3-yl)methyl)-2-methyl-1H-indole (MIMI) was chosen for separation and preconcentration of iron (III), copper (II), and zinc by solid-phase extraction (SPE). Ion–MIMI chelates are adsorbed onto synthesized graphene oxide (GO) as adsorbent, eluted with HNO3 and determined by flame atomic absorption spectrometry (FAAS). The adsorption mechanism of titled metal complexes on GO was investigated by using computational chemistry approach based on PM7 semi-empirical potential energy surface. The influences of analytical parameters were investigated. The interference effect of common cations tested did not interfere with the recovery of understudied ions. The preconcentration factor of 312.5 and the detection limits of 0.62, 0.28, and 0.05 ng mL−1 for iron (III), copper (II), and zinc, respectively, were obtained. The developed SPE method was successfully utilized for the determination of trace metal ions in different certified reference materials and real samples (including water, cheese, honey, tomato, leaves of spinach, and milk) by FAAS.

Separation of valuables from spent selective catalytic reduction catalyst leaching solution by fabricated anion extraction resins

Recovery of valuables from spent selective catalytic reduction (SCR) catalysts was carried out in order to increase the TiO2 purity and reduce the environmental impact of landfill. In our previous pressure-leaching studies, the pressure leaching process using an autoclave experienced problems resulting from residual impuries (Na2SiO3). In this study, we conducted experiments using synthetic resins to remove impurities. Glycidyl methacrylate/N,N’-methylenebisacrylamide-grafted methylcellulose beads were synthesized. Leaching solutions from spent SCR catalysts were prepared using the pressure leaching process. W and V were adsorbed onto the synthetic extraction resin, followed by desorption to recover them from separated sodium silicate. Three types of reaction models were used to analyze adsorption/desorption reaction mechanisms (adsorption isotherm, thermodynamics isotherm, and kinetic models). As a result, the adsorption W of was found to be higher than that of V because the ion selectivity of WO42− is higher than that of VO3−. Langmuir and Freundlich isotherm datas included that, adsorption relied on monolayer adsorption mechanisms. According to the Temkin isotherm, experimental W and V adsorption values and calculated Gibbs free energies for both elements were similar. The D-R isotherm, suggested that WO42− followed an ion adsorption mechanism, while some VO3− ions underwent physical adsorption. The Temkin isotherm indicated that both adsorption process (W and V) were endothermic. Pseudo first order and pseudo second order reactions were investigated to compare the theoretically predicted, time-dependent adsorptions to those determined experimentally, the results of which indicate that these adsorptions follow pseudo second order kinetics. WO42− with a higher relatively selectivity, displayed experimental data similar to those obtained theoretically by the adsorption isotherm mechanism.

Mechanism of ion adsorption to aqueous interfaces: Graphene/water vs. air/water

The adsorption of ions to aqueous interfaces is a phenomenon that profoundly influences vital processes in many areas of science, including biology, atmospheric chemistry, electrical energy storage, and water process engineering. Although classical electrostatics theory predicts that ions are repelled from water/hydrophobe (e.g., air/water) interfaces, both computer simulations and experiments have shown that chaotropic ions actually exhibit enhanced concentrations at the air/water interface. Although mechanistic pictures have been developed to explain this counterintuitive observation, their general applicability, particularly in the presence of material substrates, remains unclear. Here we investigate ion adsorption to the model interface formed by water and graphene. Deep UV second harmonic generation measurements of the SCN- ion, a prototypical chaotrope, determined a free energy of adsorption within error of that for air/water. Unlike for the air/water interface, wherein repartitioning of the solvent energy drives ion adsorption, our computer simulations reveal that direct ion/graphene interactions dominate the favorable enthalpy change. Moreover, the graphene sheets dampen capillary waves such that rotational anisotropy of the solute, if present, is the dominant entropy contribution, in contrast to the air/water interface.

Insights into the activation mechanism of calcium ions on the sericite surface: A combined experimental and computational study

The adsorption behaviors and the activation mechanism of calcium ions (Ca2+) on sericite surface have been investigated by Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR), Micro–flotation tests and First principle calculations. Zeta potential tests results show that the sericite surface potential increases due to the adsorption of calcium ions on the surface. Micro-flotation tests demonstrate that sericite recovery remarkably rise by 10% due to the calcium ions activation on sericite surface. However, the characteristic adsorption bands of calcium oleate do not appear in the FT-IR spectrum, suggesting that oleate ions just physically adsorb on the sericite surface. The first principle calculations based on the density functional theory (DFT) further reveals the microscopic adsorption mechanism of calcium ions on the sericite surface before and after hydration.

Effect of phosphoric acid on the surface properties and Pb(II) adsorption mechanisms of hydrochars prepared from fresh banana peels

The acidic environment has been confirmed to have significant influence on the biochar products through hydrothermal carbonization. To investigate the effect of H3PO4 on the surface properties and adsorption mechanisms of the biochar, fresh banana peels were used as feedstock and transformed into hydrochars under the catalysis of H3PO4 with concentration ranges from 0% to 50%wt. The addition of H3PO4 greatly impacted the physicochemical properties of the as-obtained hydrochars, such as carbonization degrees, pH values, amount of surface acidic functional groups and then further affected the adsorption mechanisms of lead ions on those hydrochars. Hydrochars catalyzed by H3PO4 with higher concentration showed higher degree of carbonization, lower value of pH and fewer amount of acidic functional groups, while lower content of H3PO4 could not completely catalyze the degradation reactions and resulted in larger quantity of intermolecular locked oxygen containing groups that could not be participated into the adsorption process. Among all six samples, hydrochar generated in 30%wt H3PO4 exhibited the best adsorption property of 241 mg g−1, possibly due to the largest concentration of the acidic functional groups on the surface rather than in the intermolecular structure of the carbon. It had been confirmed that the adsorption mechanisms were the combination of surface complexation, cationic exchange and part of precipitation. Hydrochars derived from fresh banana peel via hydrothermal carbonization catalyzed by phosphoric acid could be excellent adsorbents for lead removal in aqueous environments.