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.
- SourceAvailable from: Wei Jiang
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- "Much larger Q m value of PS-Fe 3 O 4 further demonstrated that nano-Fe 3 O 4 particles , after being coated upon PS beads, were better dispersed and exhibited more active sites for arsenate adsorption. Zhang et al.  reported the maximum arsenate adsorption capacities of Fe 3 O 4 with diameter of ∼20 nm was 44 mg/g. Yavuz et al.    found that for As(V) removal, the maximum adsorption capacity of "
ABSTRACT: Fe(3)O(4) is a promising material for arsenic sequestration due to its specific affinity toward arsenic and feasible magnetic separation. How to further increase its adsorption capacity while maintain its low-field separation is an interesting but challenging task. In this study nano-Fe(3)O(4) was successfully coated onto the outer surface of polystyrene (PS) beads of 350-400nm in diameter by the hetero-coacervation method, and the resulting composite PS-Fe(3)O(4) was characterized using transmission electron microscope (TEM), X-ray powder diffraction (XRD), and electrophoresis measurement (EM). Its adsorption toward arsenate was investigated as a function of solution pH, arsenic concentration, contact time, and coexisting anions. The maximum adsorption capacity of PS-Fe(3)O(4) was 139.3mg/g Fe(3)O(4), 77.7% greater than that of bulky Fe(3)O(4). More attractively, it can be readily separated from water under a low magnetic field (<0.035T). Continuous adsorption-desorption cyclic results demonstrated that arsenate-loaded PS-Fe(3)O(4) can be effectively regenerated by NaOH solution, and the regenerated composite beads could be employed for repeated use without significant capacity loss, indicating that nano-Fe(3)O(4) was steadily coated onto the surface of PS beads. Generally, PS beads could be employed as a promising host to fabricate efficient composites originated from Fe(3)O(4) or other nanoparticles for environmental remediation.Journal of hazardous materials 10/2012; 243. DOI:10.1016/j.jhazmat.2012.10.036 · 4.33 Impact Factor
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- "Natural arsenic (As) contamination in water supplies is a major environmental and health problem on a global scale and has become a challenge for the world scientists. Increasing concentrations of arsenic in groundwater and surface water have been reported from many regions of the world in recent years       . "
ABSTRACT: In the present study, we synthesized calcium peroxide nanoparticles and evaluated them as an innovative oxidant to remove As (III) from contaminated water samples. The CaO 2 nanoparticles were 15–25 nm in diameter identified by TEM. Oxidation occurred within minutes and CaO 2 nanoparticles effectively removed total As between natural pH conditions (6.5 and 8.5). Experiments were performed to investi-gate the influence of CaO 2 nanoparticles concentration, pH of solution and contact time on the efficiency of arsenic removal. Up to 88% removal efficiency for arsenic was obtained by nanoparticles dosage of 40 mg/L at time equal to 30 min and pH 7.5. It could be concluded that the removal efficiency was enhanced by increasing CaO 2 nanoparticles dosage and reaction time, but decreased by increasing arsenic concentration and pH for nano sized CaO 2 . These results suggest that CaO 2 nanoparticles may be used to develop a simple and efficient arsenic (III) removal method. Ó 2012 Elsevier B.V. All rights reserved.Separation and Purification Technology 07/2012; 95:10-15. DOI:10.1016/j.seppur.2012.04.021 · 3.07 Impact Factor
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ABSTRACT: As is well known, the problem of signal reconstruction may be reduced to estimation of coefficients of some signal decomposition. In the previous paper  we have shown that an optimal coordinate basis for this method must be formed from eigenfunctions of the Fisher information operator (so-called PIC-basis). However direct usage of the PIC-basis is not always convenient. Therefore we propose the combined technique, according to which any given basis (FFT, DCT, wavelet, filterbanks, etc.) is replaced by its projection on the subspace generated by the PIC-basis. Such projective basis, keeping all advantages of the initial representation, allows us to decrease the range of possible fluctuations of a signal estimate. The effectiveness of the proposed technique is illustrated by numerical examples from the area of nonlinear tomography of a mediumAcoustics, Speech, and Signal Processing, 2001. Proceedings. (ICASSP '01). 2001 IEEE International Conference on; 02/2001