A new rhodamine-based single molecule multianalyte (Cu, Hg) sensor and its application in the biological system

A new single molecule multianalyte sensor, vanillic aldehyde rhodamine 6G hydrazone has been designed for the selective detection of Cu²⁺ and Hg²⁺ ions. UV/Vis spectroscopy indicates that the sensor is a good chromogenic chemosensor for Cu²⁺ in 1:99 (v/v) ethanol-water media. Whereas, other ions, such as Li⁺, Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺, Cd²⁺, Ba²⁺, Hg²⁺ and Pb²⁺ failed to generate a distinct response. Fluorescence spectral data reveals that the sensor is an excellent fluorescent chemosensor for Hg²⁺ in aqueous ethanol solution and with no fluorescent response toward other ions. The spectroscopic behavior of the sensor in living cells indicated that it can be used for the detection of Cu²⁺ and Hg²⁺ in environmental and biological systems. Mechanisms for the high selectivity of the sensor to Cu²⁺ and Hg²⁺ are discussed.     

2-Mercaptoimidazole Covalently Bonded to a Silica Gel Surface for the Selective Separation of Mercury(II) from an Aqueous Solution

Abstract

Silica gel with a specific surface area of 365 m²·g^?1 and an average pore diameter of 60 Å was chemically modified with 2-mercaptoimidazole. The degree of functionalization of the covalently attached molecule, (≡SiO)₃(CH₂)₃—MI, where MI is the 2-mercaptoimidazole bound to the silica surface by a propyl group, was 0.58 mmol·g^?1. In individual metal adsorption experiments from aqueous solutions by the batch procedure, the affinity order was Hg^II « Cd^II > Cu^II ～ Zn^II ～ Pb^II > Mn^II at solution pHs between 4 and 7. Due to the high affinity by the sulfur atom, Hg^II is strongly bound to the functional groups. When solution containing a mixture of Hg^II, Cd^II, Cu^II, Zn^II, Pb^II, and Mn^II ions was passed through a column packed with the adsorbent, Hg^II was the only one whose adsorption and elution was not affected by the presence of other ions.     

Adsorption properties of Pb2+ on thermal-activated serpentine

ABSTRACT

Adsorption properties of nature and thermal-activated serpentines to Pb²⁺ in aqueous solution were investigated. The results showed that Freundlich isotherm and pseudo-second-order kinetics model were suitable to describe the adsorption process of Pb²⁺ on serpentines. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. The serpentine activated at 700°C exhibited maximum adsorption capacity to Pb²⁺. Based on the XRD and XPS characterization, it could be found that the structure of serpentine did not change significantly during the adsorption process, and Pb²⁺ was adsorbed on the serpentine surface as the precipitation of Pb(OH)Cl and Pb(OH)₂.     

硫酸改性甘草废渣生物吸附剂对Pb~(2+)离子的吸附

以甘草废渣为原料,经硫酸处理得到了改性甘草废渣生物吸附剂,并将其用于对水溶液中重金属离子Pb2+的吸附。通过扫描电镜、红外光谱、比表面积和表面官能团的测定等方法对改性前后甘草废渣进行了表征。采用静态吸附实验,考察了Pb2+初始浓度、吸附时间、溶液p H值及投入量对吸附剂吸附性能的影响。经硫酸改性后,甘草废渣表面结构发生了变化,表面活性基团的数目增加。在p H=5.5,对浓度为1 mmol·L-1的含Pb2+离子溶液,经90 min吸附后,吸附率达97.43%。等温吸附符合Langmuir模式,根据Langmuir方程计算,25℃时饱和吸附量为1.12 mmol·L-1,高于改性前(0.8 mmol·L·-1)。甘草废渣吸附剂对Pb2+离子的吸附符合二级动力学方程。解吸再生实验表明改性后的甘草废渣吸附剂可以再生重复使用5次以上,是性能良好的重金属离子吸附剂。     

Synthesis,crystal structures and studies on Hg2+ sensing by the diazo derivatives of sulfathiazole and sulfamethoxazole

Diazocoupling of sulfathiazole and sulfamethoxazole with 2,4-pentanedione led to the syntheses of compounds R1 and R2. These were fully characterized by single crystal X-ray diffraction studies in conjunction with UV–visible, IR, ¹H NMR, and mass spectral studies. Both the compounds were further screened for their possible use in metal ion recognition. Interestingly, compound R1 showed a selective naked-eye response for Hg²⁺, while R2 did not give a color change for any metal ions. These results can be understood in terms of a solvent-assisted low-energy absorption band in R1 that disappeared upon interaction with Hg²⁺. This absorption band was not observed in the case of compound R2 that consequently failed to show any naked-eye color change in the presence of metal ions.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.     

Selective Separation of Nickel (II) and Cobalt (II) from Waste Water by Using Continuous Cross-Flow Micellar Enhanced Ultrafiltration with Addition of Chelating Agent

The performance of continuous cross-flow micellar enhanced ultrafiltration (MEUF) is evaluated for the selective separation of nickel (Ni²⁺) and cobalt (Co²⁺) from the aqueous stream using anionic surfactant sodiumdodecyl sulfate (SDS) and the mixture of the anionic and nonionic surfactant (SDS+TritonX-100) with the addition of iminodiacetic acid (IDA) as a chelating agent. Operating parameters like operating time (upto 100 min), cross flow rate (100–175 mL/min.), pH of the feed solution (3-6 Cheryan , M. ( 1998 ) Process Design in Ultrafiltration and Microfiltration Handbook ; Technomic Publishing Co. Inc : USA . Scamehorn , J.F. ; Ellington , R.T. ; Christian , S.D. ; Penny , B.W. ; Dunn , R.O. ; Bhat , S.N. ( 1986 ) Removal of multivalent metal cations from water using micellar-enhanced ultrafiltration . AIChE Symp. Ser. , 82 ( 250 ): 48 – 58 . Baek , K. ; Yang , J.W. ( 2004 ) Cross flow micellar-enhanced ultrafiltration for removal of nitrate and chromate: competitive binding . J. Hazard. Mater. , B108 : 119 – 123 . Yurlova , L. ; Kryvoruchko , A. ; Kornilovich , B. ( 2002 ) Removal of Ni (II) ions from waste- water by micellar-enhanced ultrafiltration . Desal. , 144 : 255 – 260 . ), molar concentration ratio of the chelating agent to metals (C/M ratio, 0.5–2.5), and molar concentration ratio of the surfactant to metals (S/M ratio, 5–9) were studied to investigate the effectiveness of the process on selective separation. For the single surfactant system at all empirically selected parameters, 92% Ni²⁺ in the permeate and 94% Co²⁺ in the retentate was achieved whereas for the mixed surfactant system 93% Ni²⁺ in permeate and 84% Co²⁺ in retentate was achieved. Flux variation for single and mixed surfactant system was studied. Flux observed for the single surfactant system was 36 L/m².h and for the mixed surfactant system was 31.5 L/m².h. Flux measurement also indicates insignificant fouling of the membrane.     

Synthesis of Artificial Membrane of Copolymer (Acrylic Acid/Butyl Acrylate) PAA-PBA for the Design of Polymersomes

Polymersomes are synthetic vesicles that imitate biological membrane functions. The purpose of this work is to develop an artificial copolymer (acrylic acid/butyl acrylate) PAA-PBA membrane by random synthesis. A factorial design 2^k was applied to determine the conditions for this reaction. The Fourier transform infrared spectrometer indicated that the polymerization reaction was complete without a –C=C-absorption peak. The Gordon-Taylor equation showed that the hydrophilic part of the PAA-PBA composition is 20–40% and the hydrophobic part 60–80%. The authors selected the copolymers with low molecular weight, within the range of 3134.49 ± 994.21 g/mol and a polydispersity of 1.40.     

Siting of Co2+ Ions in Cobalt-Modified High-Silica Zeolites Probed by Low-Temperature Molecular Hydrogen Adsorption

Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy was used to characterize the effects of introducing cobalt into the zeolites ZSM-5 and mordenite. Aqueous impregnation of the hydrogen form of the zeolite and subsequent in vacuo treatment at temperatures up to 920 K results in partial exchange of protons in bridging hydroxyl groups by Co²⁺ cations. These changes are evidenced by a decrease in intensity of the bands at 3606-3609 cm^-1 characteristic of Brønsted acid sites. DRIFT spectra of hydrogen adsorbed at 77 K also confirm the exchange of protons for Co²⁺ cations, as evidenced by a decrease in the intensity of the band at 4106 cm^-1 for H₂ adsorbed on protons. By contrast, the bands at 3905, 3965, and 4010 cm^-1 for H₂ adsorbed on the Co²⁺ cations increase in intensity. With increasing Si/Al ratio at a constant Co loading of 1 wt% the intensity of the band at 3905 cm^-1 for H-ZSM-5 strongly increases in intensity relative to the other bands. This feature is attributed to Co²⁺ cations interacting with two adjacent cation-exchange sites located in a 10-membered ring. It is hypothesized that the Lewis acidity of Co²⁺ cations in such environments is higher than that of Co²⁺ cations associated with oxygen atoms in individual five- or six-membered rings containing two Al atoms, because the Co²⁺ cation can interact with only two of the four basic oxygen anions located in the ring. It is proposed that Co²⁺ cations in the latter type of sites are identified by the bands at 3965 cm^-1 and 4010 cm^-1 for adsorbed H₂.     

A Green Method to Fabricate Polyethyleneimine-Alginate Multilayer Coatings Modified Polyurethane Foam for Cu2+ Adsorption from Aqueous Solution

In this study, flexible polyurethane foam (FPUF) was modified with bio-based coatings composed of polyethylenimine (PEI) and alginate (ALG), fabricated by layer-by-layer (LbL) self-assembly. LbL self-assembled coatings modified FPUFs were studied for their potentials for removing Cu²⁺ ions from aqueous solutions by using batch adsorption technique, as a function of assembled bilayers number, pH value, carrier amount and adsorption time. The maximum adsorption capacity of the modified FPUF was shown to be 54 mg/g for Cu²⁺. Results suggested that the LbL self-assembly could potentially be a promising cost-effective technique for fabricating advanced adsorbent materials for removing pollutants from wastewater.     

Selective chromogenic and fluorogenic signalling of Hg ions using a fluorescein-coumarin conjugate

A novel, Hg²⁺-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg²⁺-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg²⁺ selectivity. The Hg²⁺ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg²⁺ ions was 4.3 × 10⁻⁶ mol L⁻¹ and the conjugate dye could be used as a chemosensor for the analysis of Hg²⁺ ions in aqueous environments.     

Spectroscopic and Thermodynamic Analysis of Cd2+ Ion Sorption Kinetics by Manganese Dioxide in the Presence of Oxyanions

The present study reports the effect of contact time, nature of electrolyte, and temperature on the sorption kinetics of Cd²⁺ by manganese dioxide, which is the most active oxide in soils and sediments. The sorption kinetics of Cd²⁺ by manganese dioxide is evaluated at pH 6 in different electrolytes in the temperatures range 293-323 K. The solid samples are equilibrated in 0.45 mmol.L^?1 Cd²⁺ and different electrolytes at pH 6. The results indicate that sorption of Cd²⁺ increases with time and temperature and the system attains equilibrium within 60 min in KNO₃ as the electrolyte. However, in the presence of 0.001 M KH2PO₄ sorption of Cd²⁺ increases and the time for equilibrium shifts to 90 min. The data second-order kinetics model and the calculated rate constant k and initial sorption rate h increases with increasing temperature phosphate treatment. Among the calculated thermodynamic activation parameters the positive values of ΔH^? and ΔG^? show the sorption process to be endothermic and nonspontaneous, while the ΔS^? being negative indicates a decrease in randomness of the system during sorption process at the solid-liquid interface. The free energy of activation decreases from 15.95 kJ.mol^?1 in nitrate to 8.76 kJ.mol^?1 in phosphate. These observations suggest that the rate controlling step in Cd²⁺ sorption is diffusionally controlled, a fact that has been proved by application of Fick’s law.     

A Novel Highly Copper(ll)-selective Chelating Ion Exchanger Based on Poly(Glycidyl Methacrylate-coethylene Dimethacrylate) Beads Modified with Aspartic Acid Derivative

Abstract

Anchoring the hydroxyaspartic acid onto poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) beads or epoxysuccinic acid onto ammoniummodified poly(GMA-co-EDMA) beads resulted in a novel chelating resin, which contained up to 0.37 mmol of the ligand per gram of resin. Batch extraction experiments showed a very high selectivity for Cu²⁺ over Zn²⁺ and Cd²⁺ ions in buffered solutions under competitive conditions.     

Functionalized magnetic core-shell Fe3O4@SiO2 nanoparticles as selectivity-enhanced chemosensor for Hg(II)

A colorimetric and ‘‘turn-on” fluorescent chemosensor Rho-Fe₃O₄@SiO₂ for Hg²⁺ in which N-(rhodamine-6G)lactam-ethylenediamine (Rho-en) is conjugated with the magnetic core-shell Fe₃O₄@SiO₂ NPs has been strategically designed and synthesized. The final product was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and UV-visible absorption and fluorescence emission. Fluorescence and UV-visible spectra results showed that the resultant multifunctional nanoparticles Rho-Fe₃O₄@SiO₂ exhibited selective ‘turn-on’ type fluorescent enhancements and distinct color changes with Hg²⁺. The selectivity of the Rho-Fe₃O₄@SiO₂ for Hg(II) ion is better than that of the Rho-en in the same conditions. In addition, the presence of magnetic Fe₃O₄ nanoparticles in the sensor Rho-Fe₃O₄@SiO₂ NPs would also facilitate the magnetic separation of the Hg(II)-Rho-Fe₃O₄@SiO₂ from the solution.     

Pressure-Swing Adsorption Separation of H2S from CO2 with Molecular Sieves 4A, 5A,and 13X

The separation of bulk quantities of H₂S from CO₂ was investigated through a series of pressure-swing adsorption experiments utilizing 4A, 5A, and 13X molecular sieves. High selectivity of H₂S over CO₂ was encountered for all sieves, particularly for the 13X and 5A. Practically pure CO₂ was produced in the adsorption stage with fresh 5A and 13X sieves, at high product recovery rates. Efficient H₂S purification was obtained with fresh 5A and regenerated 4A zeolites. The experimental results were in line with theoretical predictions of the literature.     

Diglycolamic Acid Functionalized CNTs for Preferential Selection of Eu(III) over Am(III) Ion: Density Functional Theoretical Modelling Validated by Experiments

We report the structure, bonding, energetic, and thermodynamic parameters of Eu³⁺ and Am³⁺ with diglycolamic acid functionalized CNTs at BP86 and B3LYP functional level of theory using SVP and TZVP basis set. The free energy of extraction, ΔG_ext, of Eu³⁺ and Am³⁺ was computed using standard thermodynamical procedure in conjunction with COSMO (conductor like screening model) model. The value of ΔG_ext for Eu³⁺ ion was found to be higher than that of Am³⁺ as observed in the extraction experiments. The HOMO-LUMO analysis indicates that Eu³⁺ ion is harder than Am³⁺ ion leading to stronger interaction with hard donor based DGA-CNT.     

Modification and magnetization of MOF (HKUST-1) for the removal of Sr2+ from aqueous solutions. Equilibrium,kinetic and thermodynamic modeling studies

In this research, metal-organic framework MOF(HKUST-1) was synthesized, magnetized and modified by hexacyanoferrate in order to prepare an efficient adsorbent for the removal of Sr²⁺ from aqueous solutions. The synthesized adsorbent was characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, thermal methods (TG-DTG[Themogravimetry- Derivative Theromogravimetry]), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) surface area and scanning electron microscopy (SEM). The non-magnetized (MOF/KNiFC[potassium nickel hexacyanoferrate]) and magnetized (MOF/Fe₃O₄/KNiFC) adsorbents were then employed for the removal of Sr²⁺ from aqueous solutions. The adsorption capacity of 110 and 90 mg.g^?1 was obtained, respectively, for MOF/KNiFC and MOF/Fe₃O₄/KNiFC. The adsorption process was kinetically fast and the equilibration was established within 45 min. The magnetic capability of the adsorbent examined by the vibrating sample magnetometer (VSM) technique indicated that the used adsorbent was capable of separating from the solution by applying an external magnetic field. The adsorbent showed good selectivity toward Sr²⁺ in the presence of Cs⁺, Na⁺, Mg²⁺, Ca²⁺ and Ba²⁺. The regenerated adsorbent retained more than 90% of its initial capacity. Different isotherm models including Langmuir, Freundlich, Tempkin, Sips and Redlich–Peterson were employed to examine the applicability of the isotherms to the experimental data. It was concluded that the data was best fitted to the Langmuir isotherm model. The thermodynamic parameters showed that the process was endothermic.     

Evaluation of the mercury ions adsorption capacity of copper-based metal-organic frameworks/poly (lactic acid) composites

ABSTRACT

The copper-based metal-organic frameworks (Cu-MOFs) was synthesized via the hydrothermal method and modified by 1,2-ethanedithiol. Then the Cu-MOFs/poly (lactic acid) (PLA) composites with various components were prepared by the melt blending extrusion and characterized. Their mercury ions (Hg²⁺) adsorption capacity was evaluated. Cu-MOFs could be dispersed well in PLA matrix. The glass transition temperature, crystalline temperature and melting temperature of the composites were increased as a result of the addition of Cu-MOFs. The thermal stability and crystallinity of the composites slightly improved. The Hg²⁺ adsorption efficiency of the composites enhanced with the increasing of Cu-MOFs content.     

The Sites of Molecular and Dissociative Hydrogen Adsorption in High-Silica Zeolites Modified with Zinc Ions. III DRIFT Study of H2 Adsorption by the Zeolites with Different Zinc Content and Si/Al Ratios in the Framework

study of dihydrogen adsorbed at 77K by the zinc-modified hydrogen forms of mordenite and ZSM-5 zeolites with the different Si/Al ratios in the framework indicated the existence of several adsorption sites connected with the modifying zinc ions. The fraction of the sites of the strongest perturbation of adsorbed molecular hydrogen with the H–H stretching frequency of ca. 3930–3950 cm^-1 is the highest at the highest Si/Al ratios of 41 or 80. These sites dissociatively adsorb hydrogen at moderately elevated temperatures. Adsorption of hydrogen with the higher H–H stretching frequency of about 3970–4000 cm^-1 predominates at the lower Si/Al ratios. It does not result in the dissociation of adsorbed molecules. It was concluded that the most active sites are most probably connected with the zinc ions, which compensate two distantly separated negatively charged [AlO₄]^- tetrahedra localized in the adjacent five- or six-membered rings on the walls of the large channels of the pentasil's framework. The sites of the weaker perturbation of adsorbed hydrogen are most probably connected with Zn⁺² ions at the conventional exchangeable cationic positions with two aluminum atoms in the same five- or six-membered ring.     

Ion-Exchange Characteristics of a Layered Metal Sulfide for Removal of Sr2+ from Aqueous Solutions

Strontium-90 (⁹⁰Sr) is the most abundant radionuclide in radioactive wastes, and is typically isolated by treatment with an inorganic ion-exchange material. Most inorganic ion-exchange materials contain oxygen. The ion-exchange chemistry of layered metal sulfides is relatively poorly explored compared with that of oxide ion-exchange materials. Here, a layered metal sulfide (UCR-28), constructed from [ZnGe₃S₉(H₂O)]^4? supertetrahedral clusters, was prepared under hydrothermal conditions and used for the removal of Sr²⁺ ions from aqueous solution. Batch experiments showed that UCR-28 had affinity for Sr²⁺ ions at pH values ranging from 1 to 10 and the maximum ion-exchange capacity of UCR-28 (50.1 mg/g) was achieved at pH 7. Thermodynamic parameters for the ion-exchange process were evaluated, and the enthalpy and Gibbs free energy results suggested the Sr²⁺ ion-exchange process was endothermic and spontaneous. The ion-exchange data were a good fit to the Langmuir model. In addition, the metal sulfide reported here had a relatively high thermal stability. The results of this study provide insight into the largely unknown ion-exchange chemistry of metal sulfides, and could be used for design of new chalcogenide frameworks with improved ion-exchange properties.