Removal Of Divalent Metal Ions Research Articles

Understanding adsorption of divalent metals ions (Mg, Ca) on Nitrogen-, Boron- doped, and defective graphene in nanofiltration process using van der Waals density functional method

Removal of divalent metal ions (Mg and Ca) by graphene membrane has a great implication for manufacturing chitin and chitosan in filtration process. Despite its importance, influences of the doping and vacancy in graphene on the adsorption of those metal ions remain unclear. Here, we study the adsorption of those metal ions on several graphene surfaces, namely pristine graphene (Gra), graphitic N- and B- doped graphene (N- and B-Gra), monovacancy graphene (MV-Gra), monovacancy graphene functionalized by an epoxy (O-MV-Gra), and monovacancy graphene functionalized by an hydroxyl group (OH-MV-Gra) by van der Waals density functional (vdW-DF) method. It was found all considered graphene surfaces have strong interactions with Ca, whereas Mg only chemisorbs on MV-Gra and B-Gra. Energetically, comparing with Ca adosprtion on pristine graphene, both B doping and vacancy creation strengthen the Ca adsorption, while N doping slight decreases it. The electronic structure analysis uncovers enhancement of the Cagraphene interaction by B doping and vacancy formation. Because of the results that have been observed, the removal of Ca ions from aqueous solution can be enhanced by the creation of nanopore or B doping in graphene, in which Ca atom are strongly captured by graphene.

Tailoring the properties of polyamide thin film membrane with layered double hydroxide nanoclay for enhancement in water separation

This current paper presented a new candidate and potentially to improve the current membrane materials in water filtration process. With that, the primary materials used in this research study is layered double hydroxides (LDH) nanoclay which can be obtained from earth minerals and self-synthesized from inorganic salts were discussed thoroughly to help a better understanding of these materials. However, the current technologies of water separation were still lagging behind and ineffective especially in removal of divalent metal ions and multivalent salts. Infeasibility of reverse osmosis membrane make it not a viable option for divalent salts filtration. With that, nanofiltration (NF) membrane offered as an alternative to substitute available method. In this study, thin film nanocomposite (TFN) membranes were fabricated by incorporating layered double hydroxides (LDH) nanoclay. The LDH nanoclay with different loading ratio of 0, 0.05, 0.1, 0.15 and 0.2 were impregnated into polyamide layer on top of polysulfone substrates. The fabricated TFN were characterized in terms of physicochemical properties (SEM and FTIR) and membrane hydrophilicity (contact angle). After the addition of LDH, the morphological structures of TFN membranes were changed and the surface hydrophilicity was enhanced significantly. FESEM images displayed a typical ridge and valley morphology with nodule-like structures. As the LDH loading was increased, the contact angle decreased from 34.56° to 15.76° showing the surface hydrophilicity of membrane is improved. The separation performance of membrane was evaluated in terms of salt rejection ability by cross flow filtration system. The best performance NF membrane was found to be TFN 0.05 with high water flux and MgCl2 rejection with values of 24.18 L/m2.h and 91% respectively. This study has experimentally validated the potential of LDH materials in membrane process for improvement in water separation process.

A novel multifunctional sandwiched activated carbon between manganese and tin oxides nanoparticles for removal of divalent metal ions

Combination of nano-metal oxides (NMOs) with other granular materials of porous characteristics offer excellent and promising hybrid nanosorbents with the advantages of high efficient surface and hydraulic characteristics to break out the technical barriers for application in scaled-up water decontamination. Therefore, the present study is aimed to take advantage of activated carbon (AC) as granular-porous material with reactive functional groups to encapsulate in a sandwich between manganese oxide nanoparticles (MnO2-NPs) and tin oxide nanoparticles (MnO2-NPs) to produce a novel nanosorbent (SnO2-NPs-AC-MnO2-NPs). The characterization of this nanosorbent was evaluated using FT-IR, XRD, TGA, SEM and HR-TEM. The removal performance of lead (ІІ), cadmium (ІІ) and copper (ІІ) ions on SnO2-NPs-AC-MnO2-NPs was investigated and optimized by the batch adsorption technique and applying a number of controlling parameters as pH of contact solution, shaking time, nanosorbent dosage, ionic metal concentration and interfering species. The maximum metal up-take capacities were 4100, 2600 and 2500 μ mol g−1 for copper (ІІ), lead (ІІ) and cadmium (ІІ), respectively by applying concentration of Cu(II), Cd(II) and Pb(II) (0.2 mol L−1), time of reaction (30 min), pH 7 of reaction solution and mass of SnO2-NPs-AC-MnO2-NPs (5.0 mg). Several oxygenated functional groups, especially O-H, C-O, Mn-O, and SnO are suggested to take part in the adsorption with excellent affinity and superiority in removal of the target metal ions from wastewater. This study is aimed to confirm the capability of implementation SnO2-NPs-AC-MnO2-NPs as an excellent nanosorbent for decontamination of heavy metals from different water samples with percentage range (91.2–97.6%) Cu(II), (92.4–95.5%) Pb(II) and (92.9–99.1%) Cd(II).

Silver nanoparticle-embedded pectin-based hydrogel for adsorptive removal of dyes and metal ions

Silver nanoparticles made by green synthesis have been incorporated into pectin-based copolymer gel to make a nanocomposite gel to be used as an adsorbent material for the removal of divalent metal ions and dyes from aqueous solutions. Silver nanoparticles were obtained by mixing silver nitrate with aqueous solution of pectin followed by microwave irradiation. The nanocomposite hydrogel was obtained by the microwave-assisted polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and acrylamide (AAm) in the presence of N,N’-methylene-bis-acrylamide (MBA) in pectin solution containing silver particles. Characterization of the nanocomposite gel was done by FTIR, TGA, XRD, FESEM and EDS techniques. The system was evaluated for its capacity to adsorb cationic dye, crystal violet (CV) and metal ions [Cu(II) and Pb(II)] from aqueous solutions. The presence of Ag nanoparticles is observed to enhance the adsorption capacity of the gel for the above mentioned adsorbates. The kinetic studies revealed second-order adsorption processes which fit well into Langmuir model. The evaluation of thermodynamic parameters indicated the adsorption process to be exothermic and spontaneous. A maximum of 1950 mg/g CV, 111 mg/g Cu(II) and 130 mg/g Pb(II) could be removed from the aqueous solution which is quite high in comparison with other reported materials. The desorption studies indicated the possible reusability of the nanocomposite.

Synthesis and implementation of nano-chitosan and its acetophenone derivative for enhanced removal of metals

In the present study, nano-chitosan (Nano-Ch) was synthesized by ionic gelation of chitosan/tripolyphosphate system and successfully modified with acetophenone via Schiff's base condensation to produce nano-chitosan-modified-actophenone (Nano-Ch-Ac). The produced nano-materials were characterized by FT-IR, SEM, HR-TEM and TGA techniques. The average particle sizes were found in the range of 5.20–14.54nm based on the HR-TEM analysis. The metal interaction properties of Nano-Ch and Nano-Ch-Ac with Cu(II), Cd(II), Hg(II) and Pb(II) were compared in presence of various experimental parameters. Nano-Ch-Ac sorbent was found more superior in the extraction processes of all examined metal ions under the evaluated experimental parameters. This trend was confirmed from the highest determined metal sorption capacity values of metal ions as 1298–1608 and 810–1236μmolg−1 in pH 7.0 by Nano-Ch-Ac and Nano-Ch sorbents, respectively. The adsorption equilibrium was established at 30.0min of contact time by the two nano-chitosan sorbents. The superiority of Nano-Ch-Ac was also confirmed from the dynamic applications of this nano-sorbent for removal of divalent metal ions from tap water, sea water and industrial wastewater (91.3–100.0±1.0–3.0).

Effective removal of divalent metal ions: synthesis and characterization of pH-sensitive guar gum based hydrogels

The present paper reports the modification of Guar gum network through grafting of acrylamide by free radical polymerization. The amide groups in the grafted network have been subsequently hydrolyzed by saponification. The hydrogels have been characterized by FTIR, Elemental Analysis, DSC, and TGA techniques. The nature and extent of swelling of these hydrogels is observed to be dependent on gel structure and pH. The pH dependence of uptake capacity of the hydrogels for metal ions Cu, Ni, Pb, and Zn2+ has been studied. The results reveal a very high metal uptake capacity of modified hydrogel attributed to the presence of carboxylic acid functionality. The metal adsorption is found to follow pseudo-first-order kinetics under pH 1.2 and pseudo-second-order kinetics under pH 7.0.

Increasing mechanical strength of gelatin hydrogels by divalent metal ion removal.

The usage of gelatin hydrogel is limited due to its instability and poor mechanical properties, especially under physiological conditions. Divalent metal ions present in gelatin such as Ca2+ and Fe2+ play important roles in the gelatin molecule interactions. The objective of this study was to determine the impact of divalent ion removal on the stability and mechanical properties of gelatin gels with and without chemical crosslinking. The gelatin solution was purified by Chelex resin to replace divalent metal ions with sodium ions. The gel was then chemically crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Results showed that the removal of divalent metal ions significantly impacted the formation of the gelatin network. The purified gelatin hydrogels had less interactions between gelatin molecules and form larger-pore network which enabled EDC to penetrate and crosslink the gel more efficiently. The crosslinked purified gels showed small swelling ratio, higher crosslinking density and dramatically increased storage and loss moduli. The removal of divalent ions is a simple yet effective method that can significantly improve the stability and strength of gelatin hydrogels. The in vitro cell culture demonstrated that the purified gelatin maintained its ability to support cell attachment and spreading.

Synthesis of positively charged polyelectrolyte multilayer membranes for removal of divalent metal ions

Abstract

Synthesis of ethylenediamine modified chitosan and evaluation for removal of divalent metal ions

Selective modification of chitosan has been achieved by incorporating ethylene-1,2-diamine molecule in a regioselective manner using N-phthaloylchitosan and chloro-6-deoxy N-phthaloylchitosan as precursors. The present modification results in additional nitrogen centres which function as potential binding sites during adsorption of metal ions. The derivative ethylene-1,2-diamine-6-deoxy-chitosan and its pthaloylated precursor have been evaluated for divalent metal ion removal. The former is found to have higher capacity for adsorption due to the presence of additional NH2 group. The samples exhibited highest affinity for Cu and least for Zn. About 80% of the adsorbed metal ions could be stripped in a solution of pH 1.2. The interaction between acidic metal centres and basic nitrogen centres on surface of the adsorbent appears to govern adsorption. Intrachain and interchain co-ordinate bonding involving NH and NH2 groups is proposed to be the mechanism of formation of metal–adsorbent complex. The adsorption process is described by Langmuir model.

Selective Recovery Process of Lithium from Seawater Using Integrated Ion Exchange Methods

Selective recovery of lithium from seawater was conducted by using two successive processes of ion exchange methods. The preliminary concentration process of lithium from seawater, using the benchmark-scale chromatographic operation with a granulated λ-MnO2 adsorbent, showed the recovery efficiency of lithium at ca. 33%. The purification of lithium from concentrated liquor from the benchmark plant was then conducted with a novel separation process which was developed by a combination of ion exchange methods using cation exchange resin and solvent impregnated resin. The purification process of lithium consists of the removal of divalent metal ions in the liquor with strongly acidic cation exchange resin; the removal of Na+ and K+ with the β-diketone/TOPO impregnated resin; and lastly the recovery of Li+ as precipitates of Li2CO3 using (NH4)2CO3 saturated solution. The yield of recovered Li2CO3 with the present recovery process was 56% with more than 99.9% purity.

Removal of some divalent cations from water by membrane-filtration assisted with alginate

The removal of divalent metal ions from hard waters or galvanic wastewater by polymer-assisted membrane filtration using alginate was investigated. The ability of this natural polymer to form aggregates and gels in presence of metal ions was studied, in order to carry out metal removal by ultra or micro-filtration. Alginate titrations have shown the presence of amine groups in addition to carboxylates onto the polymer backbone. The binding properties of alginate with divalent cations have been studied, showing an increasing affinity for Ca 2+ over Mg 2+ as polymer concentration increases, and the relative affinity Pb 2+⩾Cu 2+>Zn 2+>Ni 2+. The softening of hard natural waters was achieved successfully and easily, but needs an optimal alginate concentration ∼4×10 −2 M. The alginate powder can be directly added to hard waters. Except for Ni 2+, metal-removal was efficient. Polymer regeneration has shown that Cu 2+-complexes are labiles.

Novel predicting methods for the removal of divalent metal ions by magnetite/amorphous iron oxide composite systems

Several multi-regressive equations for the quantitative prediction of the percentage of divalent metal ions removal by magnetite/amorphous iron oxide composite systems have been established in the present study. The systems were synthesized from ferrous sulfate mixing with aqueous Mg 2+, Ca 2+, Mn 2+, Zn 2+, Cd 2+ and Pb 2+ nitrate solutions. The results showed that using the thermodynamic properties of divalent metal ions, the predicting model with the best linear regression result (correlation coefficient ( r)=0.9345) can be obtained from: M 2+ Removal%=−1.15984× ΔG° solv +339.91154×R M 2+ −984.57433. where Δ G° solv and R M 2+ are the experimental solvation free energies and Shannon–Prewitt ionic radii of divalent metal ions, respectively. Obeying our previous ‘linear atomization energy relationships (LAER)’, the atomization energies of metal ions (AE cation) and metal monoaquo complexes (AE complex) can supply well governing parameters for universally predicting various kinds of aqueous reactions of metal ions. The density functional calculated results thus revealed that the atomization energies of metal ions (AE cation) and metal monoaquo complexes (AE complex), coupling with the interatomic metal–oxide bond lengths ( R MO) in metal monoaquo complexes, can accurately predict the removal percentage of divalent metal ions by magnetite/amorphous iron oxide composite systems (correlation coefficient ( r)=0.9935). The linear predicting model can be expressed as: M 2+ Removal%=−2.43375× AE cation +2.40201× AE complex +235.44139×R M O −1164.56703.

Existence of efficient divalent metal ion-catalyzed and inefficient divalent metal ion-independent channels in reactions catalyzed by a hammerhead ribozyme.

The hammerhead ribozyme is generally accepted as a well characterized metalloenzyme. However, the precise nature of the interactions of the RNA with metal ions remains to be fully defined. Examination of metal ion-catalyzed hammerhead reactions at limited concentrations of metal ions is useful for evaluation of the role of metal ions, as demonstrated in this study. At concentrations of Mn2+ ions from 0.3 to 3 mM, addition of the ribozyme to the reaction mixture under single-turnover conditions enhances the reaction with the product reaching a fixed maximum level. Further addition of the ribozyme inhibits the reaction, demonstrating that a certain number of divalent metal ions is required for proper folding and also for catalysis. At extremely high concentrations, monovalent ions, such as Na+ ions, can also serve as cofactors in hammerhead ribozyme-catalyzed reactions. However, the catalytic efficiency of monovalent ions is extremely low and, thus, high concentrations are required. Furthermore, addition of monovalent ions to divalent metal ion-catalyzed hammerhead reactions inhibits the divalent metal ion-catalyzed reactions, suggesting that the more desirable divalent metal ion-ribozyme complexes are converted to less desirable monovalent metal ion-ribozyme complexes via removal of divalent metal ions, which serve as a structural support in the ribozyme complex. Even though two channels appear to exist, namely an efficient divalent metal ion-catalyzed channel and an inefficient monovalent metal ion-catalyzed channel, it is clear that, under physiological conditions, hammerhead ribozymes are metalloenzymes that act via the significantly more efficient divalent metal ion-dependent channel. Moreover, the observed kinetic data are consistent with Lilley's and DeRose's two-phase folding model that was based on ground state structure analyses.

Metal removal from aqueous solutions using chitosan-enhanced membrane filtration

The removal of divalent metal ions including Cu(II), Co(II), Ni(II), and Zn(II) from aqueous solutions by membrane filtration was studied with the help of water-soluble chitosan. The Amicon regenerated cellulose YM10 and YM30 were used as ultrafilters. Experiments were performed as a function of aqueous pH, the concentration ratio of chitosan to metals ( β), and applied pressure (Δ P). It was shown that at neutral condition the removal of Cu(II) was more efficient compared to other metals. Furthermore, metal removal from acidic solutions (pH < 6) could be enhanced by 6–10 times via the addition of chitosan. The effect of the presence of inorganic salts on the removal was also studied. Finally, the fouling phenomena during filtration was analyzed by conventional filtration theory considering compressible nature of the deposited gel.

Sorption of toxic metals by fungi and clay minerals

Removal of divalent metal ions from pH buffered solutions by the soil fungi Rhizopus arrhizus and Trichoderma viride has been examined at Cu2+, Cd2+ and Zn2+ concentrations ranging from 0 to 1000 m , in the presence and absence of the clay minerals montmorillonite and kaolinite. Uptake of the metals was followed, at three different pH values, by analysis of the reaction filtrates using atomic absorption spectrophotometry (AAS) and ion specific electrodes (ISE). The clays showed a more rapid uptake of the metal ions with equilibrium being reached in Cd2+). Accumulation of the metals by all of the sorbents was dependent on the external pH and decreased with lower pH: maximum uptakes were achieved at pH 6·5 for Cd2+ and Zn2+ and at pH 5 for Cu2+.