Highly Efficient and Selective Removal of Pb（II） ions by Sulfur-Containing Calcium Phosphate Nanoparticles

A facile one-step co-precipitation method was demonstrated to fabricate amorphous sulfurcontaining calcium phosphate （SCP） nanoparticles, in which the sulfur group was in-situ introduced into calcium phosphate. The resulting SCP exhibited a noticeable enhanced performance for Pb（II） removal in comparison with hydroxyapatite （HAP）, being capable of easily reducing 20 ppm of Pb（II） to below the acceptable standard for drinking water within less than 10 min. Remarkably, the saturated removal capacities of Pb（II） on SCP were as high as 1720.57 mg/g calculated by the Langmuir isotherm model, exceeding largely that of the previously reported absorbents. Significantly, SCP displayed highly selective removal ability toward Pb（II） ions in the presence of the competing metal ions （Ni（II）, Co（II）, Zn（II）, and Cd（II））. Further investigations indicated that such ultra-high removal efficiency and preferable affinity of Pb（II） ions on SCP may be reasonably ascribed to the formation of rodlike hydroxypyromorphite crystals on the surface of SCP via dissolution-precipitation and ion exchange reactions, accompanied by the presence of lead sulfide precipitates. High removal efficiency, fast removal kinetics and excellent selectivity toward Pb（II） made the obtained SCP material an ideal candidate for Pb（II） ions decontamination in practical application.

Selective removal of heavy metal ions from aqueous solutions with surface functionalized silica nanoparticles by different functional groups

The industrial silica fume pretreated by nitric acid at 80 °C was re-used in this work. Then, the obtained silica nanoparticles were surface functionalized by silane coupling agents, such as(3-Mercaptopropyl) triethoxysilane(MPTES) and(3-Amincpropyl) trithoxysilane(APTES). Some further modifications were studied by chloroaceetyl choride and 1,8-Diaminoaphalene for amino modified silica. The surface functionalized silica nanoparticles were characterized by Fourier transform infrared(FI-IR) and X-ray photoelectron spectroscopy(XPS). The prepared adsorbent of surface functionalized silica nanoparticles with differential function groups were investigated in the selective adsorption about Pb2+, Cu2+, Hg2+, Cd2+ and Zn2+ions in aqueous solutions. The results show that the(3-Mercaptopropyl) triethoxysilane functionalized silica nanoparticles(SiO2-MPTES) play an important role in the selective adsorption of Cu2+ and Hg2+, the(3-Amincpropyl) trithoxysilane(APTES) functionalized silica nanoparticles(SiO2-APTES) exhibited maximum removal efficiency towards Pb2+ and Hg2+, the 1,8-Diaminoaphalene functionalized silica nanoparticles was excellent for removal of Hg2+ at room temperature, respectively.

Selective capture of silver ions from aqueous solution by series of azole derivatives-functionalized silica nanosheets

The introduction of bifunctional groups into low-cost adsorbents for selective adsorption of Ag(I) through synergistic effect will have a profound impact on the recovery of precious metals. Organo silica nanosheets(organo-Si NSs) functionalized by series of azole derivatives(2-mercaptoimidazole(MI), 2-mercaptobenzimidazole(MBT) and 1H-1,2,4-triazole-3-thiol(MTT)), are fabricated and employed for selective removal of Ag(I). The structures of the organo-Si NSs are investigated using several characterization methods. The results of batch adsorption experiments display that the maximum adsorption amounts are 70.3, 103.2 and 139.5 mg·g^(-1) on MI-Si NSs, MBI-Si NSs and MTT-Si NSs for Ag(I) ions, and reach rapid equilibrium within 10–30 min. The adsorption processes are chemisorption and fit pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Notably, MTT-Si NSs is greatly selective for Ag(I) in multicomponent system, and the distribution coefficient value of Ag(I) ions reaches 2331.26 ml·g^(-1). The reusability of organo-Si NSs is verified by four cycles of regeneration tests with 0.1 mol·L^(-1) HNO_(3) as the eluent. A combination of experimental, structural along with theoretical analysis is conducted to proclaim the structure-adsorptivity relationship:(i) The adsorption mechanisms are attributed to complexation.(ii) The amino group and sulfhydryl group of MTT-Si NSs as well as MBISi NSs may have synergistic impacts on Ag(I) capture.(iii) The differences in adsorption behavior and selectivity of the three organo-Si NSs are mainly related to the form of function groups, charge density and steric hindrance of adsorbent. This work not only sheds light on the promise of functionalized organo-Si NSs for the rapid and selective removal/enrichment of Ag(I) ions in complex water systems,but also provides new insights for designing cost-effective Si NSs-based adsorbents.

Selective adsorption behavior of ion-imprinted magnetic chitosan beads for removal of Cu(Ⅱ) ions from aqueous solution

Heavy metal ion is one of the major environmental pollutants.In this study,a Cu(Ⅱ)ions imprinted magnetic chitosan beads are prepared to use chitosan as functional monomer,Cu(Ⅱ)ions as template,Fe_(3)O_(4) as magnetic core and epichlorohydrin and glutaraldehyde as crosslinker,which can be used for removal Cu(Ⅱ)ions from wastewater.The kinetic study shows that the adsorption process follows the pseudosecond-order kinetic equations.The adsorption isotherm study shows that the Langmuir isotherm equation best fits for the monolayer adsorption processes.The selective adsorption properties are performed in Cu(Ⅱ)/Zn(Ⅱ),Cu(Ⅱ)/Ni(Ⅱ),and Cu(Ⅱ)/Co(Ⅱ)binary systems.The results shows that the ⅡMCD has a high selectivity for Cu(Ⅱ)ions in binary systems.The mechanism of ⅡMCD recognition Cu(Ⅱ)ions is also discussed.The results show that the ⅡMCD adsorption Cu(Ⅱ)ions is an enthalpy controlled process.The absolute value of DH(Cu(Ⅱ))and DS(Cu(Ⅱ))is greater than DH(Zn(Ⅱ),Ni(Ⅱ),Co(Ⅱ))and DS(Zn(Ⅱ),Ni(Ⅱ),Co(Ⅱ)),respectively,this indicates that the Cu(Ⅱ)ions have a good spatial matching with imprinted holes on ⅡMCD.The FTIR and XPS also demonstrates the strongly combination of function groups on imprinted holes in the suitable space position.Finally,the ⅡMCD can be regenerated and reused for 10 times without a significantly decreasing in adsorption capacity.This information can be used for further application in the selective removal of Cu(Ⅱ)ions from industrial wastewater.

Studies of Adsorption of Cadmium Ions by Biowaste Adsorbent from Aqueous Solutions with Ion-Selective Electrodes and ICP-OES

Using environment-friendly and low-cost biowaste adsorbents as toxic metal ion removal substrates from aqueous solutions has a great economic advantage. This work evaluated pumpkin and potato peel biowastes for the adsorption of cadmium ions. The biowastes were treated with acid or base. Batch experiments were carried out by introducing a known concentration of metal ion solution into the biowaste sorbent at various pH levels. The pH and metal ion concentration was monitored with pH and cadmium ion-selective electrode continuously for two hours, and the final concentration for the metal ion after 24 hours was measured with the cadmium electrode and then confirmed with ICP-OES. L-type isotherms were obtained that fit to Freundlich model. Adsorption isotherms showed chemical adsorption and the kinetics following the second order model. Equilibrium adsorption capacity is higher than 29 mg/g at pH 5.6 when the initial concentration is 220 ppm. Dynamic cadmium adsorption capacity is 17 mg/g from aqueous solution when the feed solution is 220 ppm with pumpkin peel biowaste sorbent. The biowaste materials can be regenerated with acid washing.

Ion Selective Electrode Array Analysis Using Variable Step-Size Generalized Simulated Annealing

A global optimum location algorithm called Variable Step-Size Generalized Simulated Annealing(VSGSA) was applied to treating the data obtained by using an array of ion-electrodes in solutions containing mixtures of Na+, K+, Ca2+. Unlike traditional optimization algorithms such as simplex procedure, VSGSA can be used to determine the model parameters without any priori information about the analytical system under investigation and overcome the disadvantage of simplex method which might converge to local extrema depending on the starting positions. The algorithm was applied to po-tentiometric determination of ions in mixture solutions.

Binding mechanism of halide ions to bovine serum albumin and hemoglobin: investigated by ion selective-electrode

The binding mechanism of the interactions of halide ions (F–, Br– and I–) with bovine serum albumin (BSA) and hemoglobin (Hb) were studied at different temperatures, by using ion-selective electrodes. The experimental data were treated according to Klotz equation, and the number of binding sites and the binding constants were determined. The results show that the binding sites of F– on protein molecules are more than those of Br– and I–. Additionally, the number of the binding sites for halide ions on protein molecules increases with increasing temperature. This study also indicates that the binding constants for the interactions of halide ions with proteins gradually decrease as the size of halide ions and temperature increases. These behaviors were reasonably interpreted with the structural and thermodynamic factors. The thermodynamic functions at different temperatures were calculated with thermodynamic equations, and the enthalpy change for the interactions were also determined by isothermal titration calorimetry (ITC) at 298.15 K, which indicate that the interactions of halide ions with proteins are mainly electrostatic interaction.

Ion imprinted polymer particles of neodymium:synthesis,characterization and selective recognition

Neodymium ion imprinted polymer（Nd^3＋-IIP） particles for selective solid-phase extraction of Nd^3＋ were prepared and determined with inductively coupled plasma atomic emission spectrometry（ICP-AES）.The unleached Nd^3＋-IIP particles were prepared by the copoly-merization of Nd^3＋-5,7-dichloroquinoline-8-ol-4-vinylpyridine ternary complex with styrene and divinyl benzene, then Nd^3＋ was leached to obtain Nd^3＋-IIP particles.The adsorption capacity of the Nd3＋-IIP was 35.18 mg/g.The largest selectivity coefficient for Nd3＋ in the presence of competitive ions such as La^3＋, Ce^3＋, Pr^3＋ and Sm^3＋ was over 110.The proposed method was validated by analyzing two certified reference materials（GBW07301a sediment and GBW07401 soil） and the determined values were in a good agreement with standard values.The method was convenient, selective, sensitive and applicable to the determination of trace Nd^3＋ in environmental samples with complicated matrix.

Separation of mixed salts(Cl-/SO42-) by ED based on monovalent anion selective membranes

The industrial products or wastewater rich in the mixed salts(Cl-/SO4^2-) not only causes the environmental damage, but also induces waste of resource. In this study, an ED stack with monovalent selective AEMs and conventional CEMs was employed to separate the Cl-and SO42-from simulated wastewater. The effect of current density and mass fraction percentage was investigated in order to optimize the experimental conditions during ED process. It was found that at a concentration ratio between NaCl and Na2SO4 of 95/5(wt%/wt%) and a current density of40 m A·cm^-2, a current efficiency of 72%, an energy consumption of 1.6 k W·h·kg^-1 Na Cl and a Cl-/SO4^2-concentration(67.5/3.5 g·L^-1) were obtained. Hence, it is appropriate and effective to separate Cl-and SO42-by ED using the monovalent selective AEMs.

A Method of Determining Selectivity Coefficients Based on the Practical Slope of Ion Selective Electrodes

It is a problem to be solved that the experimental selectivity coefficients of ion selective electrodes (ISEs) depend on the activity. This paper studied the new method of determining selectivity coefficients. A mixed ion response equation, which was similar to Nicolsky-Eisenman (N-E) equation recommended by IUPAC, was proposed. The equation includes the practical response slope of ISEs to the primary ion and the interfering ion. The selectivity coefficient was defined by the equation instead of the N-E equation. The experimental part of the method is similar to that based on the N-E equation. The values of selectivity coefficients obtained with this method do not depend on the activity whether the electrodes exhibit the Nernst response or non-Nernst response. The feasibility of the new method is illustrated experimentally.

An efficient strategy for the preparation of MIL-53(Al)-NH_(2)membranes with high ion selectivity and desalination performance

The efficient extraction of sodium(Na^(+))and lithium(Li^(+))from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries.However,coexisting cations such as divalent calcium(Ca^(2+))and magnesium(Mg^(2+))ions are at the subnanometer scale in diameter,similar to target monovalent ions,making ion separation a great challenge.Here,we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH_(2)membranes on the surface of anodic aluminum oxide.Such membranes contain angstrom-scale(~7Å)channels for the entrance of small monovalent ions and water molecules,endowing the selectivities for monovalent cations over divalent cations and water over salt molecules.The resulting high-connectivity MIL-53(Al)-NH_(2)membranes exhibit excellent ion separation performance(a selectivity of 121.42 for Na^(+)/Ca^(2+)and 93.81 for Li^(+)/Mg^(2+))and desalination performance(a water/salt selectivity of up to 5196).This work highlights metal–organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.

Selective separation of gallium from aluminum in SDS–Ga–Al and SDS–Ga–Al–fluoride systems by ion flotation

Selective separation of gallium from aluminum by ion flotation using sodium dodecyl sulfate(SDS) as an anionic surfactant and fluoride as an inorganic ligand was investigated. The experimental results were analyzed using the stability constants and speciation diagrams of fluoride metal complexes. The presence of fluoride in the solution has a positive influence upon the separation of gallium from aluminum. The results show that increasing the fluoride concentration makes a more effective separation of gallium from aluminum because of a simultaneous increase in the complexion of aluminum with fluoride and a change in the electrical charge of the aluminum(ALF_4^-). The dehydration model of LIU and DOYLE was also applied to compare the ion flotation and the selectivity coefficients of gallium over aluminum with experimental results.

A New Type of Dibenzoyl Tartaric Acid Selective Electrode Based on Polymer Membrane Containing Calixarene Ionophore

A new type of di benzoyl tartaric acid selective electr ode has been developed. Three double\| arm calixarene derivatives were emp loyed as the neutral ionophores. The poly(vinyl chloride) membrane electrode containing an amide derivative of ca lixarene as the neutral carrier an d a dibutyl phthalate as the plastici zer exhibited the highest sensitivity for dibenzoyl tartaric acid. The slop e of linear portion was 27.8 mV per c oncertration decade. The electrode has a fast response and a long lifetime .

PVC Membrane Selective Electrode for Determination of Cadmium(Ⅱ) Ion in Chocolate Samples

Benzil bis(carbohydrazone)(BBC) is prepared and explored as new N N Schiff's base, which plays the role of an excellent ion carrier in the construction of a Cd(II) ion membrane sensor. The tris(2-ethylhexyl) phosphate best performance corresponds to a membrane composition of 30% poly(vinyl chloride), 65%(TEHP), 3.5% BBC and 1.5% tetradodecyl-ammoniumtetrakis(4-chlorophenyl) borate(ETH 500). This sensor shows very good selectivity and sensitivity towards cadmium ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition, selectivity, pH and influence of additive on the response properties of electrode were investigated. The response mechanism was discussed in the view of UV-spectroscopy. The electrode exhibits a Nernstian behavior(with slope of 29.7 mV per decade) over a very wide concentration range from 1.0×10?1 to 1.0×10?8 mol·L?1 with a detection limit of 3.2×10?8 mol·L?1. It shows rela-tively fast response time in whole concentration range(<8 s) and can be used for at least 10 weeks in the pH range of 2.0-9.0. The proposed sensor is successfully used for the determination of cadmium in different chocolate sam-ples and as indicator electrode in titration with ethylene diamine tetraacetate(EDTA).

An Amidoximated-UHMEPE Fiber for Selective and High Efficient Removal of Uranyl and Thorium from Acid Aqueous Solution

High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.

Monovalent cation perm-selective membranes(MCPMs)"New developments and perspectives

As one of the most typical and promising membrane processes, electrodialysis(ED) technique plays a more and more significant role in industrial separation. Especially, the separation of monovalent cations and multivalent cations is currently a hot topic, which is not only desirable for many industries but also challenging for academic explorations. The main aim of the present contribution is to view the advances of a wide variety of monovalent cation perm-selective membranes(MCPMs) and their preparation technologies including(1) covalent crosslinking,(2) surface modification,(3) polymer blending,(4) electrospinning,(5) nanofiltration alike membrane,and(6) organic–inorganic hybrid. The relevant advantages and disadvantages with respect to some specific cases have been discussed and compared in detail. Furthermore, we elaborately discuss the opportunities and challenges of MCPMs, the fabricating strategies to take and the future perspectives.

Determination of Boron Trifluoride in Boron Trifluoride Complex by Fluoride Ion Selective Electrode

A method was proposed to determine boron trifluoride in boron trifluoride complex using fluoride ion selective electrode(ISE). Hydroxide was chosen to mask aluminum for the determination of 0.01—0.1 mol/L of fluoride. The simulation indicated that the permissible aluminum masked at a certain p H value was limited and hardly related to F-concentration and boric acid. It is better to control p H value below 11.5 and the aluminum concentration within 0.025 mol/L to minimize the interference of hydroxide to the fluoride ISE. The decomposition conditions of boron trifluoride by aluminum chloride were investigated. It is found that the F-detection ratio will approach 1.0 if the Al/F molar ratio is 0.3—0.7 and aluminum concentration is no more than 0.02 mol/L when heated at 80 ℃ for 10 min. In one word, hydroxide is quite fit to mask aluminum for samples which contain high content of fluoride and aluminum and the BF3 content can be successfully determined by this method.

Molecular dynamics simulation of ion selectivity traits of nickel hexacyanoferrate thin films

The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.

An ion-imprinted polymer supported by attapulgite with a chitosan incorporated sol-gel process for selective separation of Ce(Ⅲ)

The surface ion-imprinting concept and chitosan incorporated sol-gel process were applied to the synthesis of a new attapulgitesupported polymer for selective separation of Ce（III） from aqueous solution. The imprinting mechanism of prepared ion-imprinted polymer were discussed with the Characteristics of FT-IR and SEM. Results from the experiments of adsorption capacity and selectivity suggested that ion-imprinted polymer offered a fast kinetics for the adsorption of Ce（III） under the optimum conditions. Its maximum adsorption capacity was 38.02 mg/g, and the selective recognition towards Ce（III） was much higher than that of the non-imprinted polymer and attapulgite. The prepared functional polymer was shown to be promising for selective separation and enrichment of trace Ce（III） in environmental samples. ？2009 Yong Sheng Yan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A comparative study of four 20-membered N_2S_4-crown ethers as ionophores for polymeric membrane silver selective electrodes

Four 20-membered N_2S_4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag^+-selective electrodes.Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag^+ ions.The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione(C) with 2-nitrophenyl octyl ether(o-NPOE) as solvent in a poly(vinyl chloride)(PVC) membrane matrix sho...