Ions In Aqueous Phase Research Articles

Effect on Si/Al ratio of Zeolite for the Removal of Calcium Ion in Aqueous Phase

Effect on Si/Al ratio of Zeolite for the Removal of Calcium Ion in Aqueous Phase

Dye‐linked Upconverting Nanophosphor‐based Ratiometric Chemosensor for NIR‐excited and FRET‐mediated Ultrasensitive Detection of Sulfide Ions

AbstractIn this article, a NIR‐excited ratiometric method for selective and ultrasensitive detection of sulfide (S2−) ions in an aqueous environment is presented, which is reliant on fluorescence resonance energy transfer (FRET). The chemosensor‐design is based on an upconverting nanophosphor (UCNP)‐linked coloured complex between a rhodamine‐B derivative and stannous ions (RBD‐Sn2+). Under the excitation of NIR light, the green emission of UCNP (at 542 nm) is reabsorbed by the linked RBD‐Sn2+ complex via FRET, which in turn emits in the orange (at 582 nm). S2− ions specifically interact with the linked RBD‐Sn2+ complex and quantitatively bleach its colour, leading to reduction in FRET and consequent recovery of the green emission of UCNP. We investigated the quantitative and ratiometric detection of S2− ions in aqueous phase using this NIR‐excited FRET‐based approach. The concentration of S2− ions is quantitatively connected to the ratiometric emission signal under NIR excitation. We have found that the detection limit for S2− ions using our FRET‐based nanoprobe is around ten times lower than that of colorimetric or fluorescence‐based approaches. Owing to the use of NIR‐light as excitation source, our proposed sensor can demonstrate background‐free sensing of S2− in complex environmental and biological samples.

Zn ion-modulated polyamide membrane with enhanced facilitated transport effect for CO2 separation

Polyamide membrane, fabricated via interfacial polymerization process, is a typical class of facilitated transport membrane for CO2 separation with amino groups serving as reactive CO2 carriers. Herein, to further enhance the CO2-facilitated transport effect of polyamide membrane, Zn(NO3)2 is directly introduced into aqueous triethylenetetramine phase for constructing Zn-N coordination polyamide membrane taking advantage of the coordination interaction between Zn ions and amino groups from triethylenetetramine. The good solubility of Zn(NO3)2 in aqueous amine solution and moderate coordinative ability of Zn ions are beneficial to a uniform distribution of Zn in polyamide layer. The coordination of N from triethylenetetramine monomer to Zn ion centre produces more tertiary amino groups and free amino groups with stronger affinity to CO2 in Zn-N coordination membrane for enhancing the facilitated transport effect. Additionally, the Zn-N coordination interaction generates smoother surface of membranes when sufficient Zn ions are introduced. The membrane with 0.1 wt% of Zn ions in aqueous phase exhibits the highest CO2/N2 and CO2/CH4 selectivity of 106.7 and 55.2, which increase, respectively, by 75.2% and 99.3% without compromising CO2 permeance in contrast with pristine polyamide membrane.

Multiplexed detection of aqueous Cd2+, Pb2+ and Cu2+ ions at mercury-on-graphene film modified electrode by DPASV

With the ever-increasing influence of heavy metal ions in environmental pollution, it is highly desirable to develop facile, rapid, and low-cost methods for the multiplexed detection of heavy metal ions in aqueous media sensitively and quantitatively. In this study, we report a facile electrochemical method for the selective, quantitative and multiplexed detection of cadmium (Cd2+), lead (Pb2+), and copper (Cu2+) ions in aqueous media. In this method, a glassy carbon electrode (GCE) is modified first with reduced graphene oxide(rGO) microflaks followed by the controlled in situ electro-deposition of a very thin mercury film. The final working electrode, denoted as (Hg|rGO)film|GCE, was employed as the detector for reported multiplexed detection of multi-ions, taking advantages of the well-established polaragraphic principles. The rGO layer was known to be capable of significantly increasing the heterogeneous interface electron-transfer rate and therefore the detection sensitivity, while the highly dispersed over-potentials of heavy metal ions on mercury allowed the multiplexed detection of several heavy metals ions at different working potentials. The differential pulse anodic stripping voltammetry (DPASV) was employed as the detection mode to further boost up the detection sensitivity. Very good quantitative relationships were observed between the peak current in DPASV and the concentration of the ions being detected. The cross-interference in the multiplexed detection was found negligible. The limit of detections (LODs) of Cd2+, Pb2+, and Cu2+ ions in aqueous phase at the (Hg/rGO)film/GCE working electrode were found to be 0.17, 0.18 and 0.69 μg/L, respectively.

Stable paper-based colorimetric sensor for selective detection of phosphate ion in aqueous phase

Phosphorus is one of the vital nutrients for sustenance; however, its excess concentration can cause adverse impacts on the ecosystem. Numerous sensors have been developed and deployed to monitor phosphate ions (Pi) in the environment in the past decade. However, their high cost, non-portability, and lengthy and complex fabrication processes are detrimental to their widespread use. Accordingly, the objective of the study was to develop a low-cost, convenient paper-based colorimetric sensor with brilliant green (BG) as the probe. The use of triarylmethane dye as a colouring reagent allows naked eye-visible detection of Pi in the range of 13.6–0.27 mg L−1 with the limit of detection as 0.07 mg L−1. Moreover, the proposed sensor resolves the challenges of traditional methods like the formation of insoluble complexes, the requirement of surfactants, poor reagents storability, dependence on time and temperature. The sensitivity and selectivity of BG toward Pi was verified in the aqueous phase. Later, the paper-based sensor (W-BG) was developed via dip coating as a portable detection tool. The storability, stability, and applicability of the developed strips were tested and validated using FT-IR, UV-DRS, and XRD. Additionally, the performance of the strips was compared with a microfluid paper-based device to ensure the feasibility and versatility of the strips. The sensing mechanism is deduced as the formation of the phosphomolybdate complex, which was responsible for the delocalization of the lone pair of electrons on BG, thus rendering a distinct endpoint. The selectivity and sensitivity of the sensor were maintained in real water and wastewater samples. Overall, with affordable cost (0.08 $) and portability, W-BG can be considered as a smart and environmentally friendly water quality monitoring tool.

Devising Mixed-Ligand Based Robust Cd(II)-Framework From Bi-Functional Ligand for Fast Responsive Luminescent Detection of Fe3+ and Cr(VI) Oxo-Anions in Water With High Selectivity and Recyclability.

Environmental issue related applications have globally surfaced as hottest areas of research, wherein luminescent metal-organic frameworks (LMOFs) with functionalized pores put unique signature in real-time monitoring of multiple classes of toxic compounds, and overcome many of the challenges of conventional materials. We report a two-fold interpenetrated, mixed-ligand Cd(II)-organic framework (CSMCRI-11) [Cd1.5(L)2(bpy)(NO3)]·DMF·2H2O (CSMCRI = Central Salt and Marine Chemical Research Institute, HL = 4- (1H-imidazol-1-yl)benzoic acid, bpy = 4,4′-bipyridine) that exemplifies bipillar-layer structure with two different Cd(II) nodes, and displays notable robustness in diverse organic solvents and water. Intense luminescence signature of the activated MOF (11a) is harnessed in extremely selective and fast responsive sensing of Fe3+ ions in aqueous phase with notable quenching constant (1.91 × 104 M−1) and impressive 166 ppb limit of detection (LOD). The framework further serves as a highly discriminative and quick responsive scaffold for turn-off detection of two noxious oxo-anions (Cr2O7 2− and CrO4 2−) in water, where individual quenching constants (CrO4 2−: 1.46 × 104 M−1; Cr2O7 2−: 2.18 × 104 M−1) and LOD values (CrO4 2−: 179 ppb; Cr2O7 2−: 114 ppb) rank among best sensory MOFs for aqueous phase detection of Cr(VI) species. It is imperative to stress the outstanding reusability of the MOF towards detection of all these aqueous pollutants, besides their vivid monitoring by colorimetric changes under UV-light. Mechanism of selective quenching is comprehensively investigated in light of absorption of the excitation/emission energy of the host framework by individual studied analyte.

Tuning the ion exchange behavior of cesium and strontium on sodium iron titanate

The sodium iron titanate (NaFeTiO) ion exchanger was synthesized by the hydrolysis of tetraethyl orthotitanate and ferric chloride solution using sodium hydroxide. The amount of Fe3+ present in the solution was varied to obtain different Ti/Fe mole ratios in the product ranging from 5 to 15. The ion exchanger obtained was characterized by Raman spectroscopy, X-ray diffraction, Thermogravimetry, SEM-EDX analysis and elemental composition. The ion exchange behavior of Cs+ and Sr2+ on sodium iron titanate was studied as a function of aqueous phase pH, equilibration time, initial concentration of Cs+ and Sr2+ and presence of interfering ions in aqueous phase. The rate of ion-exchange of Cs+ and Sr2+ was best fitted into pseudo-second order rate equation. Similarly, the loading behavior of Cs+ and Sr2+ on NaFeTiO and the data obtained were fitted into various adsorption models such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevitch adsorption isotherms. From the statistics of the fitting, it was found that the experimental isotherm was explained well by Langmuir adsorption model. The ion-exchange capacity of 127, 115, 95 mg.g−1 for Cs+ and 86,128,169 mg.g−1 for Sr2+ were obtained on NaFeTiO with Ti/Fe mole ratios 5, 10, and 15 respectively. The results showed that the selectivity of NaFeTiO can be tuned either for Sr2+ exchange by keeping higher Ti/Fe mole ratio or for Cs+ exchange by keeping lower Ti/Fe mole ratio. In view of this, NaFeTiO compound can be regarded as the potential candidate for separating cesium or strontium selectively from alkaline wastes.

Adsorption of Cesium and Strontium Ions in Aqueous Phase Using Porous Metal Organic Frameworks Connected with Functional Group

Adsorption of Cesium and Strontium Ions in Aqueous Phase Using Porous Metal Organic Frameworks Connected with Functional Group

Wettability of Calcite Surfaces: Impacts of Brine Ionic Composition and Oil Phase Polarity at Elevated Temperature and Pressure Conditions.

The interactions among the polar components of oil, aqueous phase ions, and carbonate minerals, as well as their subsequent effects on surface wettability, can significantly impact the fluid distribution and recovery in a hydrocarbon reservoir. In this study, we investigate the adsorption/desorption of molecules from oils with different levels of polarity on calcite surfaces during different displacement processes under elevated pressure and temperature conditions. We measured dynamic contact angles (CA) on untreated and aged calcite substrates using brines with different salinities and compositions and model oils, that is, mixtures of varying concentrations of stearic acid (SA) and n-decane. In particular, the impacts of the concentrations of Ca2+, SO42-, and OH- ions on the adsorption phenomena were explored. For the nonpolar oil, increasing brine salinity or removing Ca2+ ions from the aqueous phase impacted the potentials of oil-brine and brine-mineral interfaces and shifted the wettability of calcite surface toward more water-wet conditions. In the presence of polar oil, the adsorption of the polar components controls the surface wettability. Higher concentrations of Ca2+/SO42- could facilitate/obstruct the polar component adsorption and thus increase/decrease the dynamic oil-water CAs. It is also observed that the brine salinity does not impact the wettability if excess SA is added to the oil phase, that is, if the oil phase is strongly polar. Moreover, the adsorption of SA on the calcite surface under experimental conditions is found to be reversible during the displacement events. The surface energy calculation for the adsorption process indicates that the surface coverage of calcite by SA is more sensitive to the presence of Ca2+ in brine than the concentration of polar components in oil. We also conducted several experiments on calcite substrates aged with SA. The measurements demonstrate that the adsorbed SA molecules are detached when the aged mineral surface is exposed to a lower-salinity brine at high temperatures, and the SA molecules could be adsorbed back on the surface once the displacement is halted.

Organo-metallic complex and its implications

Complex formation is the reaction of a metal ion and ligands through electron pair sharing and the resulting product is called the metal coordination compound. The metal ion is the electron-pair acceptor, and the ligand is the electron-pair donor. The metal ion serves as the central ion, and the organic ions are coordinated around it in a first coordination sphere.Covelo et al., 2008 studied the heavy metal sorption and desorption behavior of a Fibric Histosol with that of its organo mineral fraction (OMF) and reported that greatest sorption capacity was for lead and copper. Urrutia et al., 2013 studied the physico-chemical characteristics of diverse types of humic-metal-phosphate acid complexes and reported that molecular size distribution of humic-metal-phosphate as a function of pH is similar to that of potassium or sodium humates and metal-humate complexes. Eshwar et al., 2017 studied the stability constant of Fe(II), Cu(II), Mn(II) and Zn(II) metal ion complexes with HA/FA at pH 7 and at 30 ⁰C and reported that for humic acid the log k values was highest for Cu (II) and in case of fulvic acid the log k values was highest for Mn (II). Mukhopadhyay and Sanyal, 2004 studied the release potential of arsenic (As) from arsenic-humic/fulvic complexes by soluble phosphate nitrate salt and examined it in terms of the appropriate exchange isotherms and reported that phosphate had a greater degree of exchangeability with arsenic than did nitrate, at both the lower and higher concentrations and also reported that stability constant of synthetic HA/FA were greater than that of natural HA/FA.Sinha and Bhattacharyya, 2011 studied the release isotherm of As from the HA/FA complexes extracted from vermicompost and FYM in presence of molybdate, nitrate, phosphate, sulfate and borate and reported that the greatest tendency to displace As from the complexes was shown by sulphate, molybdate, and nitrate. Datta et al., 2001 studied the stability constant of complexes formed by the humic acid with Cd2+ ions in aqueous phase and reported that humic phenolic-OH group was involved in the formation of Cd2+ -humic complexShahid et al., 2012 studied the effects of different organic ligands like ethylene diamine tetra-acetic acid (EDTA), low molecular weight organic acids, humic substances on lead speciation and reported that EDTA forms soluble, stable, and phytoavailable Pb-chelates due to high binding lead affinity. He et al., 2016 studied the binding behavior of Cu+2 to all ten HA fraction and reported that the FTIR and SEM-EDX image of HA fraction revealed that carboxyl and phenolic groups were responsible for the Cu2+ sorption on the ten sequentially extracted HA fractions process. Higher molecular weight humic acids bind heavy metals more strongly than low molecular weight acids, and the study of soil organic fractions that can sorb heavy metals moderating its toxicity in the soil/crop system and preventing its entry in the food chain should be explored in future.

Sensitive electrochemical measurement of As (III) using Nafion modified platinum electrode via anode stripping voltammetry

Arsenic (As) is considered to be one of the most toxic elements in water. Electrochemical techniques for the detection of As(III) have inherent advantages. In this study, a series of electrochemical experiments were performed in order to detect the concentration of As (III) ions in aqueous phase via Anode Stripping Voltammetry (ASV) technique by using a Nafion modified platinum electrode. The topology of the modified electrode was characterised with Atomic Force Microscopy (AFM). The electrochemical properties of the modified electrode were studied with ASV method and the optimisation parameters were determined: the amplitude of 0.02 V, frequency of 25 Hz, deposition time of 120 s. Under these optimised parameters, the linear response was in the range from 0 ppb to 40 ppb with high accuracy (R2 = 0.9917). The responding time was approximately 150 s. The sensitivity of the modified Nafion/Pt electrode was 0.036 μA/ppb. The limit of detection was below 10 ppb which is approximately equal to the recommended level of World Health Organization (WHO). The results showed the possibility of using the modified Nafion/Pt electrode for the detection of As3+ in order to test the quality of domestic water.

Preparation and ion exchange studies of cesium and strontium on sodium iron titanate

Sodium iron titanate (NaFeTiO) inorganic ion exchanger was synthesized and the ion exchange behaviour of cesium, strontium and europium ion on NaFeTiO was studied. The sodium iron titanate was prepared by the hydrolysis of tetraethyl ortho titanate with sodium hydroxide in the presence of ferric chloride at the Ti/Fe mole ratio of 25.7. The ion exchange material was characterized by elemental analysis, sodium exchange capacity, X-Ray diffraction, thermogravimetry, and Raman spectroscopy. The distribution coefficient (Kd, mL/g) of cesium, strontium and europium on NaFeTiO was measured as a function of pH of the aqueous phase, duration of equilibration, concentration of sodium, cesium, strontium and europium ion in aqueous phase. The Kd of cesium gradually increased with increase of pH, and that of strontium also increased up to pH 6 followed by saturation in Kd values. However, the distribution coefficient of europium increased up to pH 4 followed by the precipitation of europium at higher pH values. The rate of ion exchange of cesium and strontium on NaFeTiO was rapid in the initial stages of equilibration followed by the establishment of equilibrium occurring after 200 min. The kinetics of extraction was fitted in to pseudo-first order and -pseudo-second order rate equations. The NaFeTiO was found to follow the ion exchange mechanism, in which the sodium ion from NaFeTiO was exchanged with cesium or strontium ion from aqueous phase. The strontium exchange capacity on NaFeTiO was determined to be 233 mg g−1. The loaded metal ions was recovered using 0.5 M nitric acid.

Effect of the preparation technique of Cu-ZSM-5 catalysts on the isothermal oscillatory behavior of nitrous oxide decomposition

Abstract A set of Cu-ZSM-5 samples (Si/Al = 25) was synthesized by wetness impregnation, aqueous phase ion exchange and solid-state ion exchange, SSIE. Copper(II) acetate was used as precursor during both wetness impregnation and aqueous phase ion exchange to prepare excessively-exchanged samples (i.e. Cu/Al > 1), whereas SSIE was carried out by sublimating copper(I) chloride. Additionally, a Cu-ZSM-5 sample with extremely low Al content (Si/Al = 500) was prepared by impregnation. The samples were tested in the catalytic decomposition of N2O, with the aim of studying possible effects of the preparation technique on the isothermal oscillatory behavior of the reaction rate in a series of tests carried out by varying both the temperature and the residence time. The SSIE sample led to a non-oscillating system, whereas the highest Cu content samples prepared by the two aqueous procedures exhibited clear oscillations of the reaction rate. The Cu-ZSM-5 with Si/Al = 500 was quite inactive, but, surprisingly, gave rise to oscillations of both unconverted N2O and produced O2 concentrations at the reactor outlet. A combined IR spectroscopy and H2-TPR study showed the role of oligomeric CuxOy species with extra-lattice oxygen close to the Al atoms on the observed oscillations. Such species are much more abundant in the samples prepared by either impregnation or ion-exchange, when Cu/Al > 1. In contrast, the sample prepared by SSIE resulted to be rich in Cu+ isolated species, active for the reaction, but not inducing oscillation.

High internal phase emulsions stabilized with amyloid fibrils and their polysaccharide complexes for encapsulation and protection of β-carotene

In present study, lysozyme amyloid fibrils and their complexes with polysaccharides were investigated for stabilizing high internal phase emulsions (HIPEs). Linear polysaccharides, alginate and λ-carrageenan and branching ones, low and high methyl esterified pectins electrostatically bind to amyloid fibrils in nematic phase, forming well dispersed coacervates showing birefringence under polarized light. Comparatively, the polysaccharides associate with the globule protein monomers, leading to the precipitated coacervate. Interaction with the polysaccharides enhances the strength of the amyloid fibrils network. After converting protein monomers to amyloid fibrils, the binding between polysaccharides and the proteins is significantly enhanced with the affinity constant (KD) from sub-nmol to pmol level. For the first time, amyloid fibrils are found to stabilize HIPEs with highly packed polyhedral geometries in microstructure, which is dependent on protein concentration and volume fraction of the internal oil phase. The HIPEs stabilized with the amyloid fibril-polysaccharide complexes are stronger than those stabilized with only amyloid fibrils, which is attributed to the increase in the modulus of the disperse phase. The HIPE systems can encapsulate and stabilize β-carotene against ultraviolet irradiation, thermal treatment and iron ions in aqueous phase, which is mainly attributed to the protection effects of the interfacial lysozyme amyloid fibril membrane.

Experimental Determination of the Photooxidation of Aqueous I– as a Source of Atmospheric I2

The chemistry of iodine plays an important role in the oxidizing capacity of the global marine atmosphere. In this study, we experimentally determine the photooxidation parameters of iodide ions in aqueous phase (I–(aq)) and estimate the subsequent emission of gaseous iodine molecules (I2(g)) into the atmosphere. The values of the molar absorption coefficient (εiodide(λ)) and the photooxidative quantum yields (Φiodide(λ)) of I–(aq) in the range of 290–500 nm were determined. The influence of pH and dissolved oxygen (DO) on the values of Φiodide(λ) was also investigated. The emission of I2(g) into the atmosphere following the photooxidation of I–(aq) in deionized water solution (pH 5.6, DO 7.8 mg L–1) and artificial seawater solution (pH 8.0, DO 7.0 mg L–1) was estimated to be (2.2 × 10–8 × [I–(aq)]sea) and (1.8 × 10–8 × [I–(aq)]sea) mol L–1 s–1, respectively. Using a global chemistry-climate model, we estimated that the photooxidation of I–(aq) can increase the atmospheric iodine budget by up to ∼8% over some oceanic regions.

Efficient extraction of precious metal ions by a membrane emulsification circulation extractor

Solvent extraction is an important method for purification and separation in industrial applications. In this study, we develop a membrane emulsification circulation (MEC) extractor with simple structure, whose solution tank serves as mixing and clarification chamber simultaneously. Compared to conventional stirring extraction, the MEC extractor achieves better extraction performance of Pd(II) using Cyphos IL 101 as extractant since membrane emulsification produces smaller droplets and lager mass transfer area. The effects of volume ratio of organic and aqueous phase (O/A), molar ratio of ligands and metal ions (L/M), and Pd(II) concentration on extraction are systematically studied, revealing that the circulation extraction significantly reduces the consumption of extractant and diluent. Over 99% of Pd(II) is extracted at low O/A and L/M ratios, even with an extremely low concentration of 0.001 mM. Further investigations on parameters of the MEC extractor suggest that smaller pellet size of the sintered polyethylene membrane and higher flow rate benefit the extraction. Empirical formulas showing good agreement with the experimental data are established to predict the residual concentration of metal ions in aqueous phase. Moreover, Pd(II) and other precious metals widely used in electronics like Au(III) and Pt(IV) can be also efficiently and selectively extracted from simulated waste electrical and electronic equipment leachate by Cyphos IL 101 using the MEC extractor, and the extraction efficiency is 92.8% for Pt(IV), over 99.9% for both Pd(II) and Au(III). The MEC extractor exhibits great potential in practical application due to its simple structure, high economic benefits and extraction performance.

Kinetics and mechanism study of lithium extraction from alkaline solution by HFTA and TOPO and stripping process using Lewis cell technique

The kinetics of forward extraction of lithium from alkaline solution is investigated using a Lewis cell. Different parameters such as lithium concentration, HFTA concentration, TOPO concentration, pH value of aqueous phase, type of anion ion, as well as temperature are studied separately to examine their effect on lithium extraction rate, and an initial rate equation is deduced based on the experiment results. By changing the agitation speed and interfacial area of the Lewis cell, controlling mechanism of the extraction process is determined. Experimental results suggest that lithium extraction is controlled by chemical reaction at the interface rather than in the bulk phase. Further data analysis demonstrates that the lithium extraction is first order with respect to lithium ion concentration, HFTA concentration, and TOPO concentration. Different types of anion ions in aqueous phase show almost no effect on lithium extraction rate according to the experiments. Rate equation of lithium extraction by HFTA and TOPO is proposed as RLi,0 = 10−4.33±0.1 [Li+][HFTA][TOPO]. The rate-determining step of lithium extraction is the formation of final complex at the interface and the deduced extraction mechanism justified the experiments results well. For stripping process, effect of lithium concentration in organic, hydrogen ion concentration stirring speed and interfacial area on stripping rate are investigated. Analysis of the experimental data reveal that lithium stripping from organic phase is mainly controlled by chemical reaction and the reaction takes place at the interface rather than phase bulk. Linear regression of the plot of log[HCl] and log[Li+]org versus logRLi,st reveals that the reaction orders with respect to HCl and lithium in organic are both 1, namely the stripping process is first order with HCl and lithium concentration in organic. Rate equation of lithium stripping from organic phase by HCl is proposed as RLi,st = 10−4.0±0.1 [Li+]org[HCl].

Thermodynamic modeling of the solvent extraction equilibrium for the recovery of vanadium (V) from acidic sulfate solutions using Di-(2-ethylhexyl) phosphoric acid

A study of the reaction mechanism and thermodynamic modeling of pentavalent vanadium V(V) extraction from NaVO3-H2SO4-H2O solutions using Di-(2-ethylhexyl) phosphoric acid (D2EHPA or HA) extractant was carried out. The effects of initial pH of the solution, extractant concentration, and temperature on the extraction of V(V) were examined. The stoichiometry of the extraction reaction was determined using the slope analysis method. The extracted species was shown to be VO2A. A thermodynamic modeling approach was proposed for the prediction of equilibrium concentrations and pH of the system based on the known initial concentrations and process temperature. In the presented approach, the non-ideality of both aqueous and organic phases was taken into account. The activity coefficients of all organic components were calculated using UNIQUAC-NRF model, while the Electrolyte-UNIQUAC-NRF model was employed to calculate the activity coefficients of ions in aqueous phase. The equilibrium constant of the extraction reaction and the unknown parameters of the models were adjusted through the regression of experimental data at 25 °C, 35 °C, and 45 °C. Adjusted parameters were used for the prediction of equilibrium vanadium concentration in organic phase and equilibrium pH of the aqueous phase. Both of regressed and predicted values were in very good agreement with the experimental data. Moreover, calculated standard molar enthalpy of the reaction indicated the endothermicity of extraction reaction between VO2+ and D2EHPA.

Usage of deep eutectic solvents for the digestion and ultrasound-assisted liquid phase microextraction of copper in liver samples

In this study, we used deep eutectic solvents for digestion and ultrasound-assisted emulsification liquid phase microextraction (UA-ELPME) of copper in liver samples. Different types of DESs were prepared for digestion and microextraction steps. DESs consisting of lactic acid and choline chloride for the digestion step and DESs consisting of tetrabuthylamonium chloride and decanoic acid for ultrasound-assisted emulsification liquid phase microextraction were used in this method. The liver samples were digested by using DES-based digestion method. After digestion step, Cu(II) ions in aqueous phase were complexed with sodium dimethyl dithiocarbamate (NaDMDTC) and the obtained hydrophobic complex was extracted to tetrabuthylamonium chloride-decanoic acid DES phase. A microsample injection system coupled with flame atomic absorption spectrometer (MS-FAAS) was used in the detection of copper. LOD, LOQ, PF and % RSD were determined as 4.00, 13.2 µg L− 1, 10 and 3.2%, respectively. The proposed microextraction procedure was successfully applied to copper contents of the liver samples.

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