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Johan Schijf - One of the best experts on this subject based on the ideXlab platform.

  • sorption of yttrium and rare earth elements by amorphous Ferric Hydroxide influence of temperature
    Environmental Science & Technology, 2007
    Co-Authors: Kelly A Quinn, Robert H Byrne, Johan Schijf
    Abstract:

    The sorption of yttrium and the rare earth elements (YREEs) by amorphous Ferric Hydroxide was investigated between 10 and 40 °C over a range of pH (4.7−7.1) in the absence of solution complexation. Distribution coefficients, defined as iKFe = [MSi]T/([M]T[Fe3+]S), where [MSi]T is the concentration of sorbed YREEs, [M]T is the total dissolved YREE concentration, and [Fe3+]S is the concentration of precipitated iron, increased with increasing temperature over the entire investigated pH range. The observed increase in iKFe was largest for the heavy REEs, indicating that relative log iKFe values (i.e., YREE patterns) vary somewhat with temperature. The pH dependence of YREE sorption was described by a surface complexation model of the form iKFe = (Sβ1[H+]-1 + Sβ2[H+]-2)/(SK1[H+] + 1), where Sβn are stability constants for sorption of free YREE ions (M3+) and SK1 is a surface protonation constant for amorphous Ferric Hydroxide. The influence of temperature on the YREE surface stability constants (Sβ1 and Sβ2) ...

  • sorption of yttrium and rare earth elements by amorphous Ferric Hydroxide influence of solution complexation with carbonate
    Geochimica et Cosmochimica Acta, 2006
    Co-Authors: Kelly A Quinn, Robert H Byrne, Johan Schijf
    Abstract:

    The influence of solution complexation on the sorption of yttrium and the rare earth elements (YREEs) by amorphous Ferric Hydroxide was investigated at 25 °C over a range of pH (4.0–7.1) and carbonate concentrations (0M⩽[CO32-]T⩽150μM). Distribution coefficients, defined as iKFeT=[MSi]T/(MT×[Si]), where [MSi]T is the total concentration of sorbed YREE, MT is the total YREE concentration in solution, and [Si] is the concentration of amorphous Ferric Hydroxide, initially increased in magnitude with increasing carbonate concentration, and then decreased. The initial increase of iKFeT is due to sorption of YREE carbonate complexes (MCO3+), in addition to sorption of free YREE ions (M3+). The subsequent decrease of iKFeT, which is more extensive for the heavy REEs, is due to the increasing intensity of YREE solution complexation by carbonate ions. The competition for YREEs between solution complexation and surface complexation was modeled via the equation: iKFeT=(Sβ1[H+]-1+Sβ2[H+]-2+β1SCO3×β1CO3H[HCO3-]T[H+]-2)(SK1[H+]+1)×(1+HCO3β1[HCO3-]T+β1CO3H[HCO3-]T[H+]-1+β2CO3H[HCO3-]T2[H+]-2) where Sβ1 and Sβ2 are equilibrium constants for free YREE surface species, β1SCO3 is the equilibrium constant for the YREE-carbonate surface species, SK1 is the surface protonation constant for amorphous Ferric Hydroxide, and HCO3β1HCO3β1, β1CO3H, and β2CO3H are YREE solution complexation constants expressed in terms of bicarbonate concentrations. The equation, which includes (i) a single new constant (β1SCO3) for each YREE, (ii) previously published sorption coefficients (Sβ1 and Sβ2) determined in the absence of carbonate, and (iii) previously published solution complexation constants, precisely predicts both the absolute magnitude of iKFeT and the pattern of iKFeT values over our range of experimental conditions. Experimentally observed iKFeT values, spanning more than five orders of magnitude, are accurately described by our surface/solution complexation model. The logβ1SCO3values determined for each YREE in this work are: Y(−1.30 ± 0.04), La(−0.39 ± 0.02), Ce(−0.21 ± 0.02), Pr(−0.22 ± 0.02), Nd(−0.20 ± 0.02), Sm(−0.20 ± 0.02), Eu(−0.26 ± 0.02), Gd(−0.38 ± 0.02), Tb(−0.40 ± 0.02), Dy(−0.51 ± 0.02), Ho(−0.57 ± 0.02), Er(−0.59 ± 0.02), Tm(−0.56 ± 0.02), Yb(−0.62 ± 0.02), and Lu(−0.59 ± 0.02).

Patrick Paullier - One of the best experts on this subject based on the ideXlab platform.

  • concentration of Ferric Hydroxide suspensions in saline medium by dynamic cross flow filtration
    Journal of Membrane Science, 2000
    Co-Authors: Roger Bouzerar, Michel Y Jaffrin, Amelie Lefevre, Patrick Paullier
    Abstract:

    Abstract We have investigated the concentration of Ferric Hydroxide suspension in saline solution by high shear cross-flow filtration using a prototype unit with a disk rotating parallel to a circular membrane at speeds up to 1500 RPM. Three different membranes were used in the tests: two organic (nylon with 0.2 μm pores, PVDF with 40 kDa cut-off) and a mineral one (zirconium oxide, 0.1 μm pores). The system operates in the laminar boundary layer regime with a core fluid rotating at about 42% of the disk angular speed. The local permeate flux increases with increasing radius and is twice as large in the external ring as in the central part of the membrane within a 3 cm radius. With the nylon membrane at a speed of 1500 RPM, the permeate flux averaged over the total membrane area decays from 520 l/h m 2 at a Fe 3+ concentration of 15 g/l to 250 l/h m 2 at 100 g/l, values which are much higher than those obtained with the same suspension in tubular membranes. With the zirconium oxide membrane which has a lower permeability, the permeate flux at a concentration of 9 g/l rises linearly with pressure and reaches 450 l/h m 2 at 110 kPa, which is exactly the value given by hydraulic permeability, confirming the absence of fouling. A particular feature of this device is that the permeate flux actually rises when concentration increases up to 30 g/l because transmembrane pressure increases with suspension density and viscosity. This work confirms that dynamic filtration is well suited to the concentration of Ferric Hydroxide suspensions up to concentrations of 130 g/l.

Byonghun Jeon - One of the best experts on this subject based on the ideXlab platform.

Emur Henden - One of the best experts on this subject based on the ideXlab platform.

  • Study of arsenic(III) and arsenic(V) removal from waters using Ferric Hydroxide supported on silica gel prepared at low pH.
    Environmental technology, 2020
    Co-Authors: Tulin Deniz Ciftci, Onur Yayayuruk, Emur Henden
    Abstract:

    Removal of As(III) and As(V) species using Ferric Hydroxide supported on silica gel was studied. Laboratory reagent quality silica gel was used as to avoid uncertainties that may be caused by impurities. Ferric Hydroxide precipitation was realized at various pH values and a relatively low pH 6.0 was chosen because, at this pH, the highest arsenic removal capacity and removal efficiency were obtained and clear supernatant solution was observed. It was also shown by arsenic speciation analysis at trace level that As(III) is adsorbed onto Ferric Hydroxide partly without oxidation to As(V); this has been a controversial point in the literature. The effects on arsenic removal of some parameters such as pH, flow rate and matrix ions were investigated. In the batch method, initial pH change of the solution did not significantly affect the arsenic removal efficiencies for As(III) and As(V) in the pH range of 3.1-9.7. This was attributed to the decreases of the initial pH values to around 5 at equilibrium. The column capacities of 1.32 mg As(III)/g sorbent and 1.21 mg As(V)/g sorbent were found for initial concentration of 1.00 mg/L arsenic. Batch capacities were 16.2 mg As(III)/g sorbent and 17.7 mg As(V)/g sorbent for initial arsenic concentration of 100 mg/L. The method was applied successfully to the removal of As(III) and As(V) from drinking water, geothermal water and mineral water.

  • study of arsenic iii and arsenic v removal from waters using Ferric Hydroxide supported on silica gel prepared at low ph
    Environmental Technology, 2011
    Co-Authors: Tulin Deniz Ciftci, Onur Yayayuruk, Emur Henden
    Abstract:

    Removal of As(III) and As(V) species using Ferric Hydroxide supported on silica gel was studied. Laboratory reagent quality silica gel was used as to avoid uncertainties that may be caused by impurities. Ferric Hydroxide precipitation was realized at various pH values and a relatively low pH 6.0 was chosen because, at this pH, the highest arsenic removal capacity and removal efficiency were obtained and clear supernatant solution was observed. It was also shown by arsenic speciation analysis at trace level that As(III) is adsorbed onto Ferric Hydroxide partly without oxidation to As(V); this has been a controversial point in the literature. The effects on arsenic removal of some parameters such as pH, flow rate and matrix ions were investigated. In the batch method, initial pH change of the solution did not significantly affect the arsenic removal efficiencies for As(III) and As(V) in the pH range of 3.1–9.7. This was attributed to the decreases of the initial pH values to around 5 at equilibrium. The col...

Kazuo Sakata - One of the best experts on this subject based on the ideXlab platform.

  • preparation of monodisperse pseudocubic α fe2o3 particles from condensed Ferric Hydroxide gel
    Journal of Colloid and Interface Science, 1992
    Co-Authors: Tadao Sugimoto, Kazuo Sakata
    Abstract:

    Abstract Monodispersed pseudocubic particles of hematite (mean edge length 1.65 μm) with an exceedingly narrow size distribution (coefficient of variation 6.0%) have been prepared from highly condensed Ferric Hydroxide gel of approximately 1 mol dm−3 with a nominal excess concentration of Ferric ions of 0.10 mol dm−3 through aging at 100°C for 8 days. The mean diameter of the hematite particles was drastically lowered down to about 0.1 μm and the time required for the total conversion into hematite was shortened to less than 1 day as the excess concentration of Ferric ions was reduced to nominally 0. In addition, the yield of the hematite was close to 100% for all cases. The method may be referred to as the gel-sol method.