Arsenite and arsenate adsorption on coprecipitated bimetal oxide magnetic nanomaterials: MnFe2O4 and CoFe2O4
ABSTRACT Bimetal oxide magnetic nanomaterials (MnFe2O4 and CoFe2O4) were synthesized and characterized with transmission electron microscope (TEM), X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). The adsorption of arsenic on these nanomaterials was studied as a function of pH, initial arsenic concentration, contact time and coexisting anions. The Langmuir and Freundlich isotherm models were applied to fit the adsorption data, and the maximum adsorption capacities of arsenite (AsIII) and arsenate (AsV) on MnFe2O4 were 94 and 90 mg g−1, and on CoFe2O4 were 100 and 74 mg g−1, respectively. MnFe2O4 and CoFe2O4 showed higher AsIII and AsV adsorption capacities than the referenced Fe3O4 (50 and 44 mg g−1, respectively) prepared by the same procedure. Quantificational calculation from XPS narrow scan results of O(1s) spectra of adsorbents indicated that the higher adsorption capacities of AsIII and AsV on MnFe2O4 and CoFe2O4 than on Fe3O4 might be caused by the increase of the surface hydroxyl (M–OH) species. Phosphate and silicate were powerful competitors with arsenic for adsorptive sites on the adsorbent. Desorption study showed that over 80% of AsIII and 90% of AsV could be desorbed from MnFe2O4 with 0.1 M NaOH solution.
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ABSTRACT: tThe removal of arsenic in contaminated groundwater on magnetic nanoscale Fe–Mn binary oxides loadedzeolite (MFM) is evaluated in this study. MFM is produced by an improved precipitation method; and iseasily separated from water by an external magnetic field after arsenic removal. With the measured sur-face area of 340 m2/g by the BET method, the removal efficiency of MFM for arsenic is more than 99.0% atpH 7.0. The adsorption kinetics is well fitted with pseudo-second-order, as well as Weber–Morris model.Results show that arsenic adsorption on MFM is predominantly regulated by surface diffusion in initial15 min, followed by intraparticle diffusion in later stage. Adsorption and oxidation occur simultaneouslyin the process of arsenite removal, while adsorption is the sole driving process during arsenate removal.MFM exhibits a strong adsorption affinity to arsenic, and the adsorption isotherms are well describedby Freundlich and Redlich–Peterson models. A thermodynamic analysis indicates that the adsorption isspontaneous and endothermic. An adsorption site energy analysis illustrates a distribution of adsorptionenergy to exhibit the heterogeneous distribution nature on MFM for arsenic removal. This study provesMFM as a promising adsorbent for arsenic removal in contaminated groundwater.Colloids and Surfaces A Physicochemical and Engineering Aspects 09/2014; 457:220–227. · 2.11 Impact Factor
Article: a01/2012; 5:451-462.
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ABSTRACT: Iron oxide (ferrihydrite, hematite, and magnetite) coated silica gels were prepared using a low-cost, easily-scalable and straightforward method as the adsorbent material for arsenic removal application. Adsorption of the anionic form of arsenic oxyacids, arsenite () and arsenate (), onto hematite coated silica gel was fitted against non-linear 3-parameter-model Sips isotherm and 2-parameter-model Langmuir and Freundlich isotherm. Adsorption kinetics of arsenic could be well described by pseudo-second-order kinetic model and value of adsorption energy derived from non-linear Dubinin-Radushkevich isotherm suggests chemical adsorption. Although arsenic adsorption process was not affected by the presence of sulfate, chloride, and nitrate anions, as expected, bicarbonate and silicate gave moderate negative effects while the presence of phosphate anions significantly inhibited adsorption process of both arsenite and arsenate. When the actual efficiency to remove arsenic was tested against 1 L of artificial arsenic-contaminated groundwater (0.6 mg/L) in the presence competing anions, the reasonable amount (20 g) of hematite coated silica gel could reduce arsenic concentration to below the WHO permissible safety limit of drinking water of without adjusting pH and temperature, which would be highly advantageous for practical field application.Bulletin- Korean Chemical Society 01/2013; 34(8). · 0.84 Impact Factor