Amount Of Chelating Agent Research Articles

Evolution of physicochemical and leaching characteristics of municipal solid waste incineration fly ash in China under ultra-low emission standard

The physical and chemical characteristics of fly ash has changed significantly under ultra-low emission system and the current leaching system is no longer suitable for high alkalinity fly ash. This work investigated the pH values and evolution of physical and chemical characteristics of fly ash from 24 typical municipal solid waste incineration plants in China. The pH value of the leaching solution obtained by HJ/T 300–2007 presented two different acid and alkali characteristics, where high and low alkalinity fly ash accounted for 54.17% and 45.83%, respectively. The alkali content in fly ash increased significantly after ultra-low emission standard, increasing by 18.24% compared with before the implementation of GB 18485-2014. The leaching behavior of high alkalinity fly ash showed the illusion that they could enter the landfill only by the addition of a small amount of chelating agent or even without stabilization treatment, and its long-term landfill risk is significant. The phase change of high alkalinity fly ash and pH value change of the leaching solution after carbonation were the key factors for the leaching concentration change of heavy metals. Therefore, it is recommended to improve the existing leaching system or conduct accelerated carbonization experiments to scientifically evaluate the long-term leaching characteristics of high alkalinity fly ash, and to reduce the risk of heavy metal release from high alkalinity FA after entering the landfill site.

Synthesis of a Nickel-Rich LiNi0.6Mn0.2Co0.2O2 Cathode Material Utilizing the Supercritical Carbonation Process

This study aims to develop a novel efficient process for the synthesis of a nickel-rich LiNi0.6Mn0.2Co0.2O2 cathode material for lithium-ion batteries utilizing supercritical CO2. In this work, the effect of operating parameters including the amount of chelating agent, coprecipitation temperature, and sintering temperature on the composition, structure, and electrochemical performance of Ni0.6Mn0.2Co0.2CO3 precursors and LiNi0.6Mn0.2Co0.2O2 cathode materials is investigated through systematic characterization and electrochemical testing. When using 1.5 M NH4OH at 60 °C for 8 h followed by sintering at 850 °C for 12 h in air, the LiNi0.6Mn0.2Co0.2O2 cathode material delivers an initial discharge capacity of 176.3 mAh g–1 at 60 mA g–1 with a capacity retention of 94.9% after 50 cycles. This work demonstrates the application of carbon capture and utilization for battery material synthesis with the advantages of no caustic precipitating agent, no impurity introduction, and good electrochemical performance compared with a conventional carbonate coprecipitation process.

Supramolecular solvent-based liquid phase extraction of antimony prior to spectrophotometric quantification.

Antimony (Sb) is highly hazardous to human health even in minute concentration. Therefore, its accurate and precise determination in the real environmental samples is of immense importance. In this work for the first time, UV-Vis spectrophotometric method was developed for the quantification of Sb(III) from water samples using supramolecular solvent (undecanol-tetrahydrofuran)-based extraction. The maximum absorption wavelength for antomony-diathizone complex was found to be 590nm having molar absorptivity of 3.1 × 104 L.mol.cm-1. Factors affecting extraction efficiency like solution sample volume, amount of chelating agent, pH, matrix effect, and type and volume of supramolecular solvent were determined and optimized. Analytical parameters like limit of detection (0.19µg L-1), limit of quantification (0.62µg L-1), pre-concentration factor (15), enhancement factor (15), and relative standard deviation for 8 successive analysis (0.8%) were calculated under optimized experimental conditions. The method was applied to real water samples like tap water of laboratory, waste water from Kohat hospitals, and dam water (Tanda dam Kohat) with quantitative addition recovery (94-100%).

Ultrasound-assisted deep eutectic solvent-based liquid–liquid microextraction for simultaneous determination of Ni (II) and Zn (II) in food samples

A new approach was developed for the simultaneous pre-concentration and determination of Ni (II) and Zn (II) in food samples. This method is based on ultrasound-assisted liquid–liquid micro extraction using hydrophobic deep eutectic solvent (DES) and 1,10-phenanthroline as chelating agent. The effect of several parameters, such as pH, selection and volume of DES, amount of chelating agent, time of sonication and centrifugation, was studied. Under optimized conditions, the developed procedure offered exceptional sensitivity and linearity. The limit of detection was approximately 0.029 µg/Kg and 1.5 µg/Kg for Ni (II) and Zn (II), respectively. The proposed method was applied for the pre-concentration and determination of Ni (II) and Zn (II) in hydrogenated edible oils, fishes, and milk samples. The results of this study were compared with reported methods in the literature revealing its advantages.

Assessment of arsenic in water, rice and honey samples using new and green vortex-assisted liquid phase microextraction procedure based on deep eutectic solvent: Multivariate study

The aim of present study was to determine the arsenic in water, honey and rice samples using a new and green vortex-assisted liquid phase microextraction (VA-LPME), which is based on deep eutectic solvent (DES) by hydride generation-atomic absorption spectrometry. Ethylenediamine-N,N'-disuccinic acid (EDDS) was used as chelating reagent for As(III) ions. Four different DES was prepared by using different combination and molar ratios of hydrogen bond donor (HBD) as benzyltriphenylphosphonium chloride, tetra-n-butylammonium bromide, choline chloride and hydrogen bond acceptor (HBA) groups as ethylene glycol, glycerol and diethanolamine. Different parameters such as pH, chelating agent amount, DES types, molar ratio and its volume, emulsifier agents and its volume, vortex time and sample volume were optimized. The accuracy of the method was confirmed with certified reference materials. The DES-VA-LPME method was validated by using linearity r2 0.9985, working range 20–600 ng L−1, limit of detection 6.5 ng L−1, limit of quantitation 20 ng L−1 and enhancement factor 70. Intra and inter day relative standard deviation was found in the range of 3.6 and 4.1% and 4.2 and 4.9%, respectively. The developed procedure was successfully utilized for determination of arsenic in water, honey and rice samples. The factorial design was used to investigate the individual and combined effects of variables as well significant and insignificant effects.

Cadmium uptake and transfer by Sedum plumbizincicola using EDTA, tea saponin, and citric acid as activators

Sedum plumbizincicola (S. plumbizincicola) is known as a sufficient plant for phytoremediation of cadmium (Cd) polluted soils. This study aimed to investigate the effects of ethylene diamine tetraacetic acid (EDTA), tea saponin (TS), and citric acid (CA) on Cd uptake and translocation by S. plumbizincicola. To do so, using a pot experiment, we set four concentration levels of activators (1, 3, 5, and 10 mmol L−1) and a control (CK). Results showed that none of the applied activators had significant impact on soil pH. Except for CA-10, the concentration of available Cd in Cd polluted soils increased by 65.8–72.9% compared with CK. The EDTA-1, CA-1, and TS-5 treatments caused significant increases of 52.3, 67.2, and 38.4%, respectively, in the biomass of aerial parts of S. plumbizincicola (p < 0.05) compared with CK. Except for CA-3, activators increased Cd accumulation in the aerial parts of plants by 47–124% compared with CK. Of all activators, EDTA-3 caused the highest Cd accumulation of 6.64 g pot−1 in the aerial plant tissues followed by CA-10 (6.25 g pot−1) and TS-1 (5.48 g pot−1). Finally, our results suggested that the application of S. plumbizincicola together with different activators sufficiently reduced soil total Cd by 4.64–48.4% compared with CK. These findings suggest that appropriate application of EDTA, TS, and CA can promote phytoremediation of Cd contaminated soils by hyper-accumulators. In particular, the combined use of EDTA and S. plumbizincicola is an affordable and promising strategy for remediation of Cd contaminated soil. Novelty statement: Sedum plumbizincicola (S. plumbizincicola) is a well-known hyper-accumulator plant for remediation of cadmium (Cd) and zinc (Zn) contaminated soils. In addition, low molecular rganic acids and macromolecular chelating agents can improve the solubility and leaching of soil heavy metals. In the present work, we examined the combined effects of three activators (EDTA, tea saponin, and citric acid) with S. plumbizincicola to remediate a Cd contaminated soil in Anhui Province, East China. Our results indicated the effectiveness of these activators to increase soil available Cd, as well as improving the biomass of S. plumbizincicola and its Cd uptake. We believe that this study provides an efficient approach to increase the uptake of Cd by S. plumbizincicola, restoring Cd contaminated soils. Nevertheless, excessive activators may have adverse effects on soil aggregates and soil microorganisms. Therefore, it is necessary to control the amount of chelating agents and subsequently the deterioration of soil quality.

Homogeneous liquid-liquid microextraction via flotation assistance for determination of trace amounts of manganese prior to inductively coupled plasma-mass spectrometry

In the present study, homogeneous liquid-liquid microextraction via flotation assistance method is described for preconcentration of trace amounts of Mn(II). 1-(2-pyridylazo)-2-naphthol (PAN) is used as a ligand. The enriched analyte in the floated organic phase has been determined by inductively coupled plasma-mass spectrometry (ICP-MS). In this work, low density organic solvent is used and there is no need of centrifugation. Several factors influencing the microextraction efficiency, such as pH, the amount of chelating agent, nature and volume of extraction and homogeneous solvents have been investigated and optimized. Under the optimum conditions, the linear dynamic range is 1.0-500.0 ng L-1 with a correlation coefficient of 0.9998 and the detection limit of 0.1 ng L-1. The proposed method has been successfully applied for separation and determination of manganese in different water samples.

An environmentally friendly, simple and novel microextraction procedure for copper at trace level from urine, sweat, dialysis solution and water samples before its FAAS detection

ABSTRACT In order to determine copper at trace level by flame atomic absorption spectrometry (FAAS), a supramolecular solvent-based liquid-phase microextraction method has been developed. 1-(2-pyridylazo)-2-naphthol (PAN) was used as a chelating agent to obtain the copper complex. In this method, supramolecular solvent was prepared by using tetrahydrofuran (THF) and decanoic acid. pH, THF volume, amount of decanoic acid, amounts of chelating agent, ultrasonic bath and centrifugation time, matrix effects and sample solution volume parameters which were effective on the recovery of the method were optimised. The detection limit (LOD) and quantification limit (LOQ) were 7.30 µg/L, 24.2 µg/L, respectively. The preconcentration factor was found to be 40. The accuracy of the method was determined by analysing TMDA 53.3 and TMDA 64.2 certified reference materials and some addition recovery tests. The presented method was applied to urine, sweat, dialysis solution and water samples to determine their copper level by flame atomic absorption spectrometry (FAAS).

Propylene Oxide−Ethylene Oxide Block Polymer as a Surfactant for Cloud Point Extraction of Some Metal Ions

Propylene oxide-ethylene oxide block polymer (PO-EO) is a surfactant with low cloud point. It has been used for separation of Cu2+, Fe3+, Mn2+, Cd2+ and Cr3+ ions in aqueous media. The effect of different factors on recovery percent, like pH, temperature, amount of chelating agent, and amount of surfactant have been studied. A very good separation of metal ions could be achieved at different pH values with good effeciency of separation under the optimum conditions. The analyses of metal ions were carried out using flame atomic absorption spectrometer with duterium lamp background correction and calibration curve method curve method.

Analysis of Zinc and Chromium in Grain Samples Using Ionic Liquid-Based Ultrasound-Assisted Microextraction Followed by Flame-AAS After Microwave Digestion

A simple, rapid and eco-friendly microextraction method was developed for the determination and preconcentration of zinc (Zn) and chromium (Cr) from grain products by ultrasonic-assisted ionic liquid dispersive liquid-liquid microextraction (UA-IL-DLLME) combined with flame atomic absorption spectrometry (FAAS). Quercetin (2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one dihydrate) was used for the complexation of Zn(II) and Cr(III) ions at different pHs. The 1-hexyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl]imide ([Hmim][NTf2] and acetonitrile were used as extraction solvent and dispersive solvent, respectively. To provide quantitative extraction of analytes, important experimental variables such as pH of sample solution, temperature, ultrasonic time, amount of chelating agent, amount of ionic liquid, type and amount of dispersive solvent, and interference effect were extensively studied and optimized. The detection limits and operating ranges for Zn(II) and Cr(III) using the optimized conditions were 7.5, 25-450 and 2.4, 8-300μgL-1, respectively. For the validation of the proposed method, the certified reference material was tested using the standard addition method. After microwave digestion analysis of grain products, relative standard deviations (RSDs%) and recoveries were ranged from 1.2 to 2.3% and from 91.2 to 103.7%, respectively. The UA-IL-DLLME method has been successfully applied for the determination of Zn and Cr in grain samples (chickpea, broad bean, pea, beans, and wheat).

Phenolic compounds profile, neuroprotective effect and antioxidant potential of a commercial Turkish coffee

ABSTRACT Objective The purpose of this study is to determine the phenolic and flavonoid contents, and antioxidant activities and neuroprotective effects of powdered coffee sample of a commercial coffee brand originated from Sivas, Turkey. Methods Total phenolic, flavonoid and antioxidant contents, enzymatic and non-enzymatic antioxidative activities based on 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, metal chelating potential, reducing power, superoxide dismutase and catalase activity tests and lipid peroxidation inhibition potentials of the ethanolic and aqueous extracts of the coffee sample were assayed using the commonly preferred spectrophotometric methods. Furthermore the extracts’ cholinesterase and tyrosinase inhibition potentials were evaluated. Phenolic profiles of the coffee sample were investigated using high performance liquid chromatography. Results Catechin was the most frequently detected phenolic acid. In addition, it was demonstrated that the water extract has a significant impact when compared with standard antioxidants. While the SC50 (sufficient concentration to obtain 50% of a maximum scavenging capacity) value for the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl free radical was calculated as being 0.08mg/mL for water extract, the amount of chelating agents with half Fe2+ ions in the medium was found to be 0.271mg/mL. Additionally, it was shown that 0.1mg/mL concentration of both extracts prevents lipid peroxidation by 8%. Compared with standard drugs, inhibition potentials of cholinesterase and tyrosinase enzymes were considered as moderately acceptable in these samples. Conclusion Besides the extracts’ enzymatic antioxidant activity, their inhibition potential on cholinesterase and tyrosinase enzymes – which are important clinical enzymes – reveal that this natural source can be used as a valuable resource in different fields, especially in medicine.

Structural and magnetic properties of nanocrystalline nickel ferrite (NiFe2O4) synthesized in sol-gel and combustion routes

Nano-crystalline Nickel ferrite (NiFe2O4) was synthesized in sol-gel and combustion methods with different chelating agents like PVA, citric acid and urea. In the synthesis, the amount of chelating agent was taken exactly equal to the optimal output mass of the nickel ferrite which is unlike to conventional sol-gel or combustion method of synthesis. The powder X-ray diffraction technique was performed to identify the structure of the nickel ferrite and crystallite sizes of these samples were measured. The crystallite size was observed to be in the range of 6–14 nm. Dynamic light scattering was performed to analyze the particle size distribution. DLS measurements revealed that the average particle diameters for the three samples were in the range of 10–25 nm. All the three samples were studied for magnetization and the measurements were carried out using Vibrating Sample Magnetometer at room temperature. Among the three samples, sample synthesized via citric acid auto combustion method displayed a highest magnetization of 27.05 emu/g and sample synthesized through combustion method with Urea displayed low saturation magnetization owing to its smaller crystallite size and improper development of crystal planes. Magneto-crystalline anisotropy (K1) constants were determined using law of approach and the three samples displayed an order of 105 erg/cm3.

The separation–preconcentration and determination of ultra-trace gold in water and solid samples by dispersive liquid–liquid microextraction using 4-ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) as chelating agent and flame atomic absorption spectrometry

A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO3 concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L−1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L−1. The relative standard deviation obtained 2.1% at 50 µg L−1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples.

Removal of copper ions from an aqueous solution containing a chelating agent by electrosorption on mesoporous carbon electrodes

Abstract The ordered mesoporous carbon (OMC) synthesized by the template method was prepared as an electrosorption electrode in this study to discuss the electrosorption capacity of copper ions from an aqueous solution containing a chelating agent when the potential was applied. The physicochemical properties of OMC were analyzed by TEM, a nitrogen adsorption/desorption apparatus, an X-ray photoelectron spectrometer, and a Zeta potential meter. The concentration change of copper ions in the aqueous solution was measured by atomic absorption spectrometry, so as to calculate the electrosorption capacity. When the chelating agent was added in, the Cu-chelated complexes were adsorbed onto the anode, and the free copper ions were adsorbed by the cathode. When 0.8 V voltages were applied, the electrosorption capacity for copper ions from the aqueous solution with a slight amount of chelating agent was larger than that in the solution without chelating agent. For aqueous solution without chelating agent, the equilibrium electrosorption capacity for copper ions was 35.90 mg/g at pH = 4. For solutions with 10% citric acid or EDTA chelating agent, the copper ion electrosorption capacities increased to 70.18 mg/g and 59.26 mg/g, respectively.

Morphological Characterization of Tungsten Trioxide Nanopowders Synthesized by Sol-Gel Modified Pechini's Method

Sol-gel modified Pechini's method was used to prepare WO3 nanopowders using dicarboxylic acid and polyethylene glycol as the chelating agent and polymeric source, respectively. WO3 powders were first prepared by calcination of resin precursor at 550oC under various initial concentrations of metal ion (12.5-50 mmol), acid (125-500 mmol), a complexing agent (32-262 mmol), and polyethylene glycol (1-16.5 mmol) in the air atmosphere. The products were characterized using X-ray powder diffraction, field emission scanning electron microscopy, and energy dispersive spectroscopy. The results revealed that the WO3 nanopowders prepared with different amounts of chelating agent and polyethylene glycol, crystallized in monoclinic phase. The nanopowders were impurity-free due to the presence of the complexing agent and polyethylene glycol as carbon sources. Morphological evolution indicated that the nanopowders evolved from rod-like to regular and spherical shapes, depending on complexing agent and polyethylene glycol amounts. Nanopowders with an average particle size of approximately 58 nm and a narrow size distribution were obtained.

Optimizing parameters affecting synthesis of a novel Co–Mo/GO catalyst in a Naphtha HDS reaction utilizing D-optimal experimental design method

In this research effects of important synthesis parameters upon catalytic performance of a novel graphene based catalyst for an HDS reaction were investigated. The graphene oxide (GO) used as a support was initially prepared through chemical exfoliation of graphite via modified Hummers method. In this venue the impregnation method, promoter/main metallic spices ratio, total metal loading of the active phase and amount of chelating agent were systematically understudied. Thus, GO was impregnated with active metallic phases through the hydrothermal and modified incipient wetness impregnation techniques. In both procedures, 1:2, 1:3 and 1:4 weight ratios of Co/Mo with the percentages of the total metals amounting to 5, 10, and 15, respectively, were utilized. This was done together with the citric acid (CA) as a chelating agent with a CA/Mo molar ratio varying in the range of 1–5. The synthesized materials were characterized through the X-ray diffraction (XRD) technique as well as; the BET–BJH surface area measurements, Field Emission Scanning Electron Microscopy (FESEM), Inductively Coupled Plasma (ICP) and Temperature programmed desorption of ammonia (NH3-TPD) analyses. After a thorough characterization of this material, the catalyst was evaluated in an HDS reaction through a fixed-bed reactor under industrial conditions for a Naphtha feed. Obtained results revealed 95–100% conversions. This rendered the prepared material very promising for the purpose at hand. Then the D-optimal experimental design software was utilized to optimize the preparation of the GO based catalysts. In this venue, although the hydrothermally prepared material provided a more economical catalyst, the wetness impregnation method prevailed as the preferred one to synthesize an optimum catalyst with 0.3 wt% Co/Mo ratio, 10% total metal loadings and CA/Mo molar ratio of 2.

MICROWAVE-ASSISTED LIQUID PHASE MICROEXTRACTION FOLLOWED WITH FLAME ATOMIC ABSORPTION SPECTROMETRY FOR TRACE DETERMINATION OF ZINC IN FOOD SAMPLES

In this work, microwave-assisted liquid phase microextraction (MA-LPME) was followed by flame atomic absorption spectrometry for determination of zinc in food samples. Zinc was complexed with a chelating agent to form hydrophobic species.1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]) ionic liquid (IL) was used as environmentally-friendly extraction solvent. In order to disperse the extraction phase into the sample solution and improve the extraction efficiency, microwave irradiation was used as a disperser agent. The heating effect of microwave irradiation makes the ionic liquid dissolved and dispersed through the sample, which significantly improves the speed and efficiency of extraction. After extraction process, sample solution was centrifuged and the settled phase was diluted and introduced to flame atomic absorption spectrometry by conventional aspiration. Various parameters including amount of ionic liquid, microwave power, irradiation time, pH, amount of chelating agent and salt amount were studied and optimized. At optimized condition, a limit of detection (LOD) of 1.5 ng mL-1, a linear range of 5-32 ng mL-1 and a RSD of 4.3% were obtained. Finally, the developed protocol was utilized for determination of zinc in food samples.

Toward a Complete Removal of Barite (Barium Sulfate $$\hbox {BaSO}_{4}$$ BaSO 4 ) Scale Using Chelating Agents and Catalysts

Barite scale is the most common oilfield scale in oil and gas wells. Barite scale removal still represents a challenge to the oil and gas industry because of its low solubility in mineral acids such as HCl. Chelating agents such as diethylene triamine pent acetic acid (DTPA), ethylene diamine tetra acetic acid (EDTA), and hydroxy ethyl ethylene tri acetic acid were introduced as barite scale removers, but the solubility of barite in these chelates was very low. Huge amount of chelating agents are required to remove the barite scale, but we are constrained by the hole volume of the well. In this study, a novel formulation was developed to dissolve the barite scale by using chelating agents and a catalyst to enhance the solubility of barite in chelating agent (DTPA) with small volume of chelating agents. Using the catalyst in this formulation is the main feature of the treatment. Solubility experiments were conducted to determine the dissolution rate of barite in DTPA chelating agent at different temperatures. The effect of pH on the dissolution rate of barite was studied using two bases (potassium base KOH and sodium base NaOH). The optimum chelating agent (DTPA) concentration and time were identified that will achieve the maximum barite scale solubility. Also, the catalyst type and concentration were determined using high-temperature high-pressure solubility experiments. Kinetics experiments using rotating disk apparatus were performed to investigate the mechanism of catalyst during the reaction of DTPA with barite. Based on the results from this study, DTPA (0.5M concentration) potassium base chelating agent was able to dissolve 60% of barite scale at high pH (11–12) in 24 h. The solubility of barite in the DTPA increased with time up to 24 h and after that it remained constant which means the optimum time for the barite scale removal is 24 h. The removal of barite scale increased up to 80–90% after adding (5–7 wt %) of one of the following catalyst: potassium carbonate $$(\hbox {K}_{2}\hbox {CO}_{3})$$ , potassium chloride (KCl), and potassium formate $$(\hbox {CHKO}_{2})$$ . The developed formulation (DTPA/catalyst) can be used to remove the barite scale from oil and gas wells effectively. Rotating disk experiments showed that the catalyst enhanced the DTPA diffusion to the rock surface and in turn enhanced the mass transfer reaction rate.

A new supramolecular based liquid solid microextraction method for preconcentration and determination of trace bismuth in human blood serum and hair samples by electrothermal atomic absorption spectrometry.

A simple and reliable supramolecule-aggregated liquid solid microextraction method is described for preconcentration and determination of trace amounts of bismuth in water as well as human blood serum and hair samples. Catanionic microstructures of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants, dissolved in deionized water/propanol, are used as a green solvent to extract bismuth (III)-diethyldithiocarbamate complexes by dispersive microextraction methodology. The extracted solid phase is easily removed and dissolved in 50μL propanol for subsequent measurement by electrothermal atomic absorption spectrometry (ET-AAS). The procedure benefits the merits of supramolecule aggregates' properties and dispersive microextraction technique using water as the main component of disperser solvent, leading to direct interaction with analyte. Phase separation behavior of extraction solvent and different parameters influencing the extraction efficiency of bismuth ion such as salt concentration, pH, centrifugation time, amount of chelating agent, SDS:CTAB mole ratio, and solvent amounts were thoroughly optimized. Under the optimal experimental conditions, the calibration curve was linear in the range of 0.3-6μgL-1 Bi (III) with a limit of detection (LOD) of 0.16μgL-1 (S/N=3). The relative standard deviations (RSD) of determination were obtained to be 5.1 and 6.2% for 1 and 3μgL-1 of Bi (III), respectively. The developed method was successfully applied as a sensitive and accurate technique for determination of bismuth ion in human blood serum, hair samples, and a certified reference material.

Complexing Agents on Carbon Content and Lithium Storage Capacity of LiFePO4/C Cathode Synthesized via Sol-Gel Approach

Olivine-structured LiFePO4faces its intrinsic challenges in terms of poor electrical conductivity and lithium-ion diffusion capability for application to lithium-ion batteries. Cost-effective sol-gel approach is advantageous to in situ synthesize carbon-coated LiFePO4(LiFePO4/C) which can not only improve electronic conductivity but also constrain particle size to nanometer scale. In this study, the key parameter is focused on the choice and amount of chelating agents in this synthesis route. It was found that stability of complexing compounds has significant impacts on the carbon contents and electrochemical properties of the products. At the favorable choice of precursors, composition, and synthesis conditions, nanocrystalline LiFePO4/C materials with appropriate amount of carbon coating were successfully obtained. A reversible capacity of 162 mAh/g was achieved at 0.2Crate, in addition to good discharge rate capability.