Total Metal Cations Research Articles

Enhanced degradation of iohexol in water by CuFe2O4 activated peroxymonosulfate: Efficiency, mechanism and degradation pathway

Iohexol as an iodinated X-ray contrast agent is widely used, and it is the potential precursor for toxic iodinated disinfection by-products in the disinfection process. In this study, a series of CuFe2O4 catalysts were prepared by sol-gel method with different molar ratios of total metal cations to citric acid ([Men+]T/CA) and employed as heterogeneous catalysts to activate peroxymonosulfate (PMS) for the removal of iohexol. The catalysts were characterized by various technologies, and the effect of [Men+]T/CA molar ratio on the catalysts' properties was explored. The CuFe2O4 synthesized with [Men+]T/CA molar ratio of 1:1 showed the best catalytic activity to PMS, and 95.0% of 1.0 mg/L iohexol was removed within 15 min by using 50 mg/L CuFe2O4 and 20 mg/L PMS. The quenching experiment and electron spin resonance (ESR) spectra indicated the generation of SO4- and OH in the CuFe2O4/PMS system, and the quantity experiments revealed that the generation concentration of SO4- was ten times higher than that of OH. The generation mechanism of SO4- and ·OH were investigated by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) spectra. The effects of catalyst dosage, PMS and iohexol concentration on the removal of iohexol were studied, and various water matrix factors including solution pH, natural organic matter (NOM) concentration and inorganic ions were also considered. Based on the twelve intermediate products of iohexol detected by UPLC-QTOF/MS, the degradation pathway was proposed. The high catalytic activity and reusability of CuFe2O4 indicated that CuFe2O4 activating PMS is an effective and sustainable way for the treatment of iohexol.

Pragmatic strategy for the removal of ammonia from gold mine effluents using a combination of electro-coagulation and zeolite cation exchange processes: A staged approach

Considerable amount of water is frequently used in gold mine for dust suppression and ore processing. The generated effluent mainly contains heavy metals, suspended solid and ammonia. This paper investigates the ammonia removal from mine effluent by a natural zeolite-adsorption process. Preliminary experiments showed that the fresh zeolite has a higher ammonia removal efficiency. Based on the results of adsorption isotherm, Langmuir isotherm model was found to be well fitted with the experimental data with a maximum adsorption capacity of 8.7 mg N g−1 zeolite. As the ammonia concentration in the mine effluent was not exceeding 30 mg L−1, column adsorption capacity was around 0.85 mg g−1; however, the regeneration of zeolite by 0.6 M NaCl was ineffective after third adsorption/regeneration cycle. To overcome this challenge, electrocoagulation process was introduced as a pre-treatment step to remove suspended solids and metal cations. With current density of 1.14 mA cm−2 and 20 min of reaction time, more than 90 % of suspended solid, turbidity and total metal cations were precipitated. For an optimal scenario, the adsorption capacity of zeolite increased up to 2.3 mg.g−1. Electrocoagulation for raw effluent significantly prolongs the life span of zeolite because the adsorption of trivalent metal cations on zeolite is irreversible.

Corrosion Behavior of Noble Metals in Different Oral Media

In this first study, the corrosion behavior of the noble (Au, Pd, Rh, Cu, Ag, Pt, Ir) metals studied in 0.1M citric acid (CA), 10% carbamide peroxide (CP), artificial saliva (AS) and in the presence of CP, mouthwash (MW) and in presence of AS, and 0.1M NaCl solutions as oral solution. Electrochemical methods investigated with open circuit potential, impedance spectroscopy, current-potential and linear polarization measurements. Metal electrodes immersed in different oral solutions during a week for the determination of total metal cations. These cations analyzed by ICP-OES/MS. This article outline determined with corrosion tendencies of the noble metals and the amount of these ions passing through the human body. Scanning electron microscope (SEM) images showed that gold surface damaged in the presence of the CP. Additionally, the surface examined with EDS. It is concluded that the corrosion rate of noble metals increased in the presence of carbamide peroxide, due to the additional reactions pathways mediated by hydrogen peroxide anions. Keywords : Noble metals, Pilling-Bedworth, Hydrogen Peroxide, Artificial Saliva, Mouthwash DOI : 10.7176/JSTR/5-4-14

A facile sol-gel strategy for the scalable synthesis of CuFe2O4 nanoparticles with enhanced infrared radiation property: Influence of the synthesis conditions

CuFe2O4 particles were successfully engineered by a facile sol-gel method. The synthesized products were characterized physically by X-ray diffraction (XRD), scanning electron microscopy (SEM). Besides, the effects of the sintering temperature and the molar ration of citric acid/the total metal cations (CA/MC) on their infrared radiant properties were investigated at the wavelength of 3–5μm. The highest infrared emission value ca. 0.911 was obtained when the test temperature was conducted at 800°C, indicating its potential application in infrared heating, infrared coating and drying fields.

Influence of the Mg2+ or Mn2+ contents on the structure of NiMnAl and CoMgAl hydrotalcite materials with high aluminum contents

In this work, layered double hydroxides with high aluminum content (aluminum atom fractions 0.3 and 0.5, relative to total metal cations) were successfully synthesized in the systems CoAl, CoMgAl, NiAl and NiMnAl, using a co-precipitation method with controlled pH. Terephthalate was used as the charge compensation anion. Different characterization techniques (XRD, FTIR, ICP, AAS, TGA, CHN and EXAFS) showed that for these high-aluminum LDHs, the terephthalate ions are vertically placed within the interlayer galleries and the cations were effectively included in the layers. The unusually large limiting value for the intralayer aluminum proportion is possibly associated with the larger length and polarizability of the terephthalate anion as compared to the usual small inorganic anions (as carbonate, nitrate or hydroxyl). However, in the trimetallic samples (CoMgAl and NiMnAl) a segregated aluminum phase was found for higher Mg or Mn contents. With high Mn content a manganese terephthalate phase was also observed.

LiY1–xEux(MoO4)2 as a promising red-emitting phosphor of WLEDs synthesized by sol-gel process

A series of LiY1–xEux(MoO4)2 red–emitting phosphors were synthesized by sol–gel technique. The phase impurity and spectroscopic properties were characterized by X-ray diffraction (XRD) and photo-luminescence (PL) spectra respectively. The effect of Eu3+ doping concentration, annealing temperature and the molar ratio of citric acid to the total metal cations (C:M) on the optical properties of the red phosphors were studied and optimized. It was found that all the samples could be excited efficiently by blue light (465 nm), which was well coincident with the emission of GaN based LED chips. The luminescent intensity reached maximum when annealing temperature was 750 °C and Eu3+ doping concentration was 5% with C:M=3:1.

Porous MAl 2O 4:Eu 2+ (Eu 3+), Dy 3+ (M = Sr, Ca, Ba) phosphors prepared by Pechini-type sol–gel method: The effect of solvents

In this work, a series of porous Eu 2+-doped alkaline earth aluminates phosphors including MAl 2O 4:Eu 2+ (Eu 3+), Dy 3+ (M = Sr, Ca, Ba) have been prepared by Pechini-type sol–gel approach, using citric acid as chelating ligand and ethylene glycol (or H 2O) as solvent. The as-obtained samples were characterized by means of XRPD, FESEM and PL techniques. MAl 2O 4:Eu 2+, Dy 3+ (M = Sr, Ca, Ba) phosphors were prepared in a reducing atmosphere (H 2/Ar, 20 + 80%) while MAl 2O 4:Eu 3+, Dy 3+ (M = Sr, Ca, Ba) phosphors were obtained in air. Upon changing the molar ratio of citric acid to total metal cations concentration in ethylene glycol can produce spherical phosphors and the higher molar ratio favors the formation of spherical ones. Otherwise, irregular shaped phosphors occur when conducting the reaction in pure H 2O. The irregular shaped phosphors have higher emission intensity than those spherical ones observed with the help of excitation spectra, emission spectra and decay curves.

Interaction of Inorganic Mercury(II) with Polyamines, Polycarboxylates, and Amino Acids

A study on chemical equilibria of different Hg2+−organic ligand systems is reported to establish the sequestration power of N/O donor groups versus metal. Ligand classes considered are: O-donors (succinate, 1,2,3,4-butanetetracarboxylate, 1,2,3,4,5,6-benzenehexacarboxylate, polymethacrylate, and polyacrylates); N-donors (ethylenediamine, diethylenetriamine, spermidine, triethylentetramine, tetraethylenpentamine, poly(allylamine), and poly(ethylenimine)); and amino acids (glycine, histidine, and aspartic acid). Equilibria were studied potentiometrically in NaNO3 at I = 0.1 mol·L−1 and t = 25 °C. For some systems, the dependence on ionic strength in the range (0 ≤ I ≤ 1) mol·L−1 (NaNO3) and the overall enthalpy changes, by calorimetric measurements, were also determined. The sequestering ability of ligands toward Hg2+ was evaluated, defining the amount of ligand necessary to sequester 50 % of the total metal cation concentration, pL50. The dependence on temperature and on ionic strength of pL50 was determin...

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

Amorphous hafnia (HfO2−y), zirconia (ZrO2−y), and hafnia-zirconia (xHfO2−y–(1−x)(ZrO2−y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2⋅8H2O), zirconium dichloride oxide (ZrOCl2⋅8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M–0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structure were prepared across the entire hafnia-zirconia compositional spectrum, with a critical particle size for the cubic structure of about 6nm. Nanoparticles of tetragonal and monoclinic structure were prepared by increasing the annealing temperature and/or using a less reducing environment. The unique role of HMT in sample preparation is discussed as well.

Synthesis of CaAl4O7 via Citric Acid Precursor.

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Synthesis of Ca 3Al 2O 6 via citric acid precursor

Ca 3Al 2O 6 was synthesized via citric acid precursor. The effects of the molar ratio of citric acid to total metal cations concentration (CA/M) on the formation of Ca 3Al 2O 6 were investigated. Increasing the CA/M promoted the formation of Ca 3Al 2O 6. Single-phase and well-crystallized Ca 3Al 2O 6 was obtained from the CA/M = 1, CA/M = 2 and CA/M = 4 precursor at temperatures 1100 °C, 1100 °C and 1000 °C, respectively. Ca 4Al 6O 13 and Ca 5Al 6O 14 were formed as intermediate phases. No Ca 12Al 14O 33 or CaAl 2O 4 was observed. The mechanism of formation of Ca 3Al 2O 6 was discussed. Differential thermal analysis and thermogravimetric (DTA/TG) and X-ray diffractometry (XRD) were used to characterize the precursors and the derived oxide powders.

Preparation of nanocrystalline Sr 3Al 2O 6 powders via citric acid precursor

Sr 3Al 2O 6 was synthesized via citric acid precursor. The effects of the molar ratio of citric acid to total metal cations concentration (CA/M) on the formation of Sr 3Al 2O 6 were investigated. Increasing the CA/M promoted the formation of Sr 3Al 2O 6. Single-phase and well-crystallized Sr 3Al 2O 6 was obtained from the CA/M = 1, CA/M = 2 and CA/M = 4 precursor at temperature 1200 °C, 1100 °C and 900 °C, respectively. Differential thermal analysis and thermogravimetric (DTA/TG), X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the precursors and the derived oxide powders. Sr 3Al 2O 6 nanoparticles with a diameter of about 50–70 nm were obtained.

Synthesis of SrAl 2O 4 from a mixed-metal citrate precursor

A mixed-metal citrate precursor method was used to synthesize SrAl 2O 4. The effects of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration (CA/M) on the formation of SrAl 2O 4 were studied. DTA, TG, FT-IR, XRD and field emission scanning electron microscopy (FESEM) were used to characterize the precursors and the derived oxide powders. XRD analysis showed that single-phase SrAl 2O 4 was synthesized from CA/M = 2 precursors at a temperature of 900 °C for 2 h, without the formation of any intermediate phase.

Synthesis of CaAl 4O 7 via citric acid precursor

CaAl 4O 7 was synthesized by citric acid precursor method. The effects of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration on the formation of CaAl 4O 7 were investigated. Increasing the molar ratio of citric acid to total metal cations concentration promoted the formation of CaAl 4O 7. When the molar ratio of citric acid to total metal cations concentration was 2, well-crystallized, single-phase CaAl 4O 7 was synthesized at 1000 °C for 2 h for the precursor with unadjusted pH, but it could not be obtained for the precursor with pH 7. Increasing the molar ratio of citric acid to total metal cations concentration up to 4, single-phase CaAl 4O 7 was synthesized at 800 °C for 2 h for the precursors with pH 7, but it was obtained at 850 °C for 2 h for the precursors with unadjusted pH. DSC, TG and XRD were used to characterize the precursors and the derived oxide powders.

Synthesis and electrical properties of CeO2-added (Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics

(Na0.5Bi0.5)0.94Ba0.06TiO3-xwt.%CeO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) powders were synthesis by a citrate method, and the piezoelectric and ferroelectric properties of the ceramics were investigated. The results indicate that the citrate method is an advantageous route in producing (Na0.5Bi0.5)0.94Ba0.06TiO3-xwt.%CeO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) ceramics. Homogeneous and fine powders with a pure perovskite structure were derived from precursor solutions with a mole ration of citric acid to total metal cation content (C/M) of 1.3 by calcining at 650°C for 1h. The sample containing 0.6wt.%CeO2 made by the citrate method shows superior piezoelectric properties and a strong ferroelectricity: high piezoelectric constant (d33=157pC/N), high electromechanical coupling factor (kp=31.2%), enhanced dielectric constant (ε33T/εo=819) and relatively low dissipation factor (tanδ=2.72%) at 1kHz, corresponding to a relatively large remanent polarization of Pr=38.0μC/cm2 and a relatively low coercive field of Ec=37.4kV/cm.

Synthesis of yttrium aluminum garnet (YAG) from an ethylenediaminetetraacetic acid precursor

Yttrium aluminum garnet was synthesized via ethylenediaminetetraacetic acid (EDTA) precursor route. The precursors and the derived oxide powders were characterized by differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The effect of the molar ratio of EDTA to total metal cation concentration (EDTA/M) on the crystallization behavior of YAG was investigated. For the EDTA/M = 1 precursors, YAG was found to crystallize from an amorphous precursor beginning at temperatures of 800 °C within 2 h in air and completely transformed into YAG at 950 °C; a certain amount of hexagonal-YAlO 3 co-existed with the YAG phase between 800 and 900 °C. For the EDTA/M = 0.5 precursors, the phase-pure YAG was obtained at 1000 °C for 2 h.

Effects of pH and citric acid contents on the synthesis of BaTi 4O 9 via polymeric precursor

BaTi 4O 9 was synthesized via polymeric precursor made of citric acid and ethylene glycol. The effects of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration on the formation of BaTi 4O 9 were investigated. Increasing the pH of the starting solutions retarded the formation of BaTi 4O 9, but the increase of the molar ratio of citric acid to total metal cations concentration enhanced the formation of BaTi 4O 9. Single-phase BaTi 4O 9 was obtained at 1100 °C for 2 h when the molar ratio of citric acid to total metal cations concentration was unity, independent of the pH of the starting solutions. Increasing the molar ratio of citric acid to total metal cations concentration up to 2, single-phase BaTi 4O 9 was synthesized at 1000 °C for 2 h for the pH unadjusted precursors, but for the precursors with pH 6.0, the formation temperature of single-phase BaTi 4O 9 was increased to 1100 °C. When the molar ratio of citric acid to total metal cations concentration was increased further up to 4, single-phase BaTi 4O 9 formed at 1000 °C for 2 h for the precursors with or without pH adjustment. DSC, TG, XRD and FESEM were used to characterize the precursors and the derived oxide powders. Details of the synthesis and characterizations of the resultant products were given.

Synthesis of SrAl 4O 7 via citric acid precursor

SrAl 4O 7 was synthesized by Pechini method using citric acid as a chelating agent and ethylene glycol as an esterification agent. The effects of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration on the formation of SrAl 4O 7 were investigated. Increasing the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration promoted the formation of SrAl 4O 7. When the molar ratio of citric acid to total metal cations concentration was 2, well crystallized, single-phase SrAl 4O 7 was synthesized at 900 °C for 2 h for the precursor with pH 7, but it could not be obtained for the precursor with pH 1. Increasing the molar ratio of citric acid to total metal cations concentration up to 4, single-phase SrAl 4O 7 was also synthesized at 900 °C for 2 h for the precursors with pH 7, but it was obtained at 1100 °C for 2 h for the precursors with pH 1. The stability of SrAl 4O 7 as a function of time and temperature was determined. We found that SrAl 4O 7 can be stable up to 1400 °C for 2 h and it shows decomposition at 1500 °C for 2 h. Heating single-phase SrAl 4O 7 powder at 1600 °C for 2 h, most of SrAl 4O 7 decomposes to SrAl 12O 19 as the major phase and an unidentified phase (main reflection at d = 3.0149). DSC, TG, FT-IR and XRD were used to characterize the precursors and the derived oxide powders.

Preparation of SrFeO ∼2.85 perovskite using a citric acid assisted Pechini-type method

Nanocrystalline SrFeO ∼2.85 perovskite was synthesized by a citric acid assisted sol–gel method. The synthesis procedure was optimized by systematically varying the pH, molar ratio of citric acid to total metal cations (Ra) and calcination temperature. The resulting effects on SrCO 3 impurity, surface area and crystallite size were studied. The as-prepared SrFeO ∼2.85 has been characterized by elemental analysis, X-ray diffraction (XRD), nitrogen adsorption isotherms (BET), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These showed that the best conditions for preparing single phase nanocrystalline SrFeO ∼2.85 perovskite powders employed pH < 5, Ra = 1.0 and a calcination temperature of 600 °C.

Preparation of ferroelectric BaNb 2O 6 by the urea method

A precipitate was formed when an aqueous solution of BaCl 2, NbF 5 and urea in required ratio (the ratio of total metal cations to the urea is five) is heated on a water bath at 100 °C. This precipitate on decomposition at 600 °C yielded the nanocrystallites of BaNb 2O 6 (BN), as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000° C) as reported for the formation of BaNb 2O 6. Transmission electron microscope (TEM) investigations revealed that the average particle size is 85 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 900. The ferroelectric hysteresis loop parameters of these samples were also studied.