NanoMagnetics Instruments Ltd.

Ankara, Turkey

NanoMagnetics Instruments Ltd.

Ankara, Turkey
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Kantar C.,Canakkale Onsekiz Mart University | Ari C.,Canakkale Onsekiz Mart University | Keskin S.,NanoMagnetics Instruments Ltd. | Dogaroglu Z.G.,Mersin University | And 2 more authors.
Journal of Contaminant Hydrology | Year: 2015

Laboratory batch and column experiments, in conjunction with geochemical calculations and spectroscopic analysis, were performed to better understand reaction mechanisms and kinetics associated with Cr(VI) removal from aqueous systems using pyrite as the reactive material under both static and dynamic flow conditions similar to those observed in in situ permeable reactive barriers (PRBs). The X-ray photoelectron spectroscopy (XPS) and geochemical calculations suggest that the Cr(VI) removal by pyrite occurred due to the reduction of Cr(VI) to Cr(III), coupled with the oxidation of Fe(II) to Fe(III) and S2 2 - to SO4 2 - at the pyrite surface. Zeta potential measurements indicate that although the pyrite surface was negatively charged under a wide pH range in the absence of Cr(VI), it behaved more like a "metal oxide" surface with the surface potential shifting from positive to negative values at pH values > pH 6 in the presence of Cr(VI). Batch experiments show that increasing solution pH led to a significant decrease in Cr(VI) removal. The decrease in Cr(VI) removal at high Cr(VI) concentrations and pH values can be explained through the precipitation of sparingly soluble Cr(OH)3(s), Fe(OH)3(s) and Fe(III)-Cr(III) (oxy) hydroxides onto pyrite surface which may, then, lead to surface passivation for further Cr(VI) reduction. Batch results also suggest that the reaction kinetics follow a first order model with rate constants decreasing with increasing solution pH, indicating proton consumption during Cr(VI) reduction by pyrite. Column experiments indicate that nearly 100% of total Fe in the column effluent was in the form of Fe(II) species with a [SO4 2 -]/[Fe2 +] stoichiometric ratio of 2.04, indicating that the reduction of Cr(VI) by pyrite produced about 2 mol of sulfate per mole of Fe (II) release under excess surface sites relative to Cr(VI) concentration. Column experiments provide further evidence on the accumulation of oxidation products which consequently led to a significant pressure build up in pyrite packed columns over time. © 2015 Elsevier B.V. All rights reserved.


PubMed | Canakkale Onsekiz Mart University, NanoMagnetics Instruments Ltd., Yildiz Technical University and Mersin University
Type: | Journal: Journal of contaminant hydrology | Year: 2015

Laboratory batch and column experiments, in conjunction with geochemical calculations and spectroscopic analysis, were performed to better understand reaction mechanisms and kinetics associated with Cr(VI) removal from aqueous systems using pyrite as the reactive material under both static and dynamic flow conditions similar to those observed in in situ permeable reactive barriers (PRBs). The X-ray photoelectron spectroscopy (XPS) and geochemical calculations suggest that the Cr(VI) removal by pyrite occurred due to the reduction of Cr(VI) to Cr(III), coupled with the oxidation of Fe(II) to Fe(III) and S2(2-) to SO4(2-) at the pyrite surface. Zeta potential measurements indicate that although the pyrite surface was negatively charged under a wide pH range in the absence of Cr(VI), it behaved more like a metal oxide surface with the surface potential shifting from positive to negative values at pH values >pH 6 in the presence of Cr(VI). Batch experiments show that increasing solution pH led to a significant decrease in Cr(VI) removal. The decrease in Cr(VI) removal at high Cr(VI) concentrations and pH values can be explained through the precipitation of sparingly soluble Cr(OH)(3(s)), Fe(OH)(3(s)) and Fe(III)-Cr(III) (oxy) hydroxides onto pyrite surface which may, then, lead to surface passivation for further Cr(VI) reduction. Batch results also suggest that the reaction kinetics follow a first order model with rate constants decreasing with increasing solution pH, indicating proton consumption during Cr(VI) reduction by pyrite. Column experiments indicate that nearly 100% of total Fe in the column effluent was in the form of Fe(II) species with a [SO4(2-)]/[Fe(2+)] stoichiometric ratio of 2.04, indicating that the reduction of Cr(VI) by pyrite produced about 2 mol of sulfate per mole of Fe (II) release under excess surface sites relative to Cr(VI) concentration. Column experiments provide further evidence on the accumulation of oxidation products which consequently led to a significant pressure build up in pyrite packed columns over time.


Sonusen S.,Sabanci University | Karci O.,NanoMagnetics Instruments Ltd. | Dede M.,NanoMagnetics Instruments Ltd. | Aksoy S.,Technical University of Istanbul | And 2 more authors.
Applied Surface Science | Year: 2014

Graphene micro-Hall probes were developed for a scanning Hall probe microscope system and used for the direct magnetic imaging domains of demagnetized NdFeB permanent magnet for the first time. The Hall coefficient and minimum magnetic field resolution of graphene Hall probes at 1 kHz were found to be 0.18 Ω/G and 0.20-G/Hz for a drive current of 3 μA at room temperature in vacuum. The magnetic domains in NdFeB demagnetized magnet were observed at 300 K, 126 K and 3 K successfully. © 2014 Elsevier B.V.


Karci O.,NanoMagnetics Instruments Ltd. | Karci O.,Hacettepe University | Dede M.,NanoMagnetics Instruments Ltd. | Oral A.,Middle East Technical University
Review of Scientific Instruments | Year: 2014

We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ∼12 fm/√Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system. © 2014 AIP Publishing LLC.


PubMed | Ecole Polytechnique Federale de Lausanne, NanoMagnetics Instruments Ltd. and Middle East Technical University
Type: Journal Article | Journal: The Review of scientific instruments | Year: 2014

We describe the design of a low temperature scanning Hall probe microscope (SHPM) for a dilution refrigerator system. A detachable SHPM head with 25.4 mm OD and 200 mm length is integrated at the end of the mixing chamber base plate of the dilution refrigerator insert (Oxford Instruments, Kelvinox MX-400) by means of a dedicated docking station. It is also possible to use this detachable SHPM head with a variable temperature insert (VTI) for 2 K-300 K operations. A microfabricated 1m size Hall sensor (GaAs/AlGaAs) with integrated scanning tunneling microscopy tip was used for magnetic imaging. The field sensitivity of the Hall sensor was better than 1 mG/Hz at 1 kHz bandwidth at 4 K. Both the domain structure and topography of LiHoF4, which is a transverse-field Ising model ferromagnet which orders below TC = 1.53 K, were imaged simultaneously below 40 mK.


Bulbul M.S.,Canakkale Onsekiz Mart University | Kantar C.,Canakkale Onsekiz Mart University | Keskin S.,NanoMagnetics Instruments Ltd.
Water, Air, and Soil Pollution | Year: 2016

Laboratory batch and column experiments were performed to better understand the effects of Ca2+, Mg2+, and HCO3 - on Cr(VI) removal from aqueous systems with pyrite. Batch results show that increasing HCO3 - concentration led to an increase in Cr(VI) removal by pyrite due to pH buffering capacity of HCO3 -. However, while Ca2+ and Mg2+ individually had no effect on Cr(VI) removal at pH 4, the addition of Ca2+ or Mg2+ to systems containing HCO3 - resulted in a significant decrease in Cr(VI) removal at pH 8 relative to the systems containing HCO3 - alone. The XPS data proved that while Ca2+ precipitated as CaCO3(S) onto pyrite surface, Mg2+ sorbed and/or accumulated as Mg(OH)2(S) onto oxidized pyrite surface. The formation of surface precipitates (e.g., CaCO3) inhibited further Cr(VI) reduction by blocking electron transfer between Cr(VI) and pyritic surface sites. While the precipitation of Ca2+ as CaCO3 led to a significant decrease in effluent pH, the decrease in effluent pH was very low in systems containing Mg2+, most probably due to much higher solubility of Mg2+ at pH 8. Zeta potential measurements provided further evidence that while Ca2+ or Mg2+ had no effect on zeta potential of pyrite particles under acidic conditions (e.g., pH < 7), the addition of Ca2+ or Mg2+ to systems containing Cr(VI) reversed the pyrite surface potential from negative to positive under alkaline pH conditions (e.g., pH > 8) relative to system containing only Cr(VI), suggesting the sorption and/or accumulation of surface precipitates on pyrite surface. © 2016 Springer International Publishing.


Kantar C.,Canakkale Onsekiz Mart University | Ari C.,Canakkale Onsekiz Mart University | Keskin S.,NanoMagnetics Instruments Ltd.
Water Research | Year: 2015

New technologies involving in-situ chemical hexavalent chromium [Cr(VI)] reduction to trivalent chromium [Cr(III)] with natural Fe(II)-containing minerals can offer viable solutions to the treatment of wastewater and subsurface systems contaminated with Cr(VI). Here, the effects of five different chelating agents including citrate, EDTA, oxalate, tartrate and salicylate on reductive Cr(VI) removal from aqueous systems by pyrite were investigated in batch reactors. The Cr(VI) removal was highly dependent on the type of ligand used and chemical conditions (e.g., ligand concentration). While salicylate and EDTA had no or little effect on Cr(VI) removal, the ligands including citrate, tartrate and oxalate significantly enhanced Cr(VI) removal at pH<7 relative to non-ligand systems. In general, the efficiency of organic ligands on Cr(VI) removal decreased in the order: citrate≥oxalate≈tartrate>EDTA>salicylate≈non-ligand system. Organic ligands enhanced Cr(VI) removal by 1) removing surface oxide layer via the formation of soluble Fe-Cr-ligand complexes, and 2) enhancing the reductive iron redox cycling for the regeneration of new surface sites. While citrate, oxalate and tartrate eliminated the formation of surface Cr (III)-Fe(III)-oxides, the surface phase Cr (III) species was observed in the presence of EDTA and salicylate indicating that Cr(III) complexed with EDTA and salicylate sorbed or precipitated onto pyrite surface, thereby blocking the access of CrO42- to pyrite surface. The binding of Fe(III) with the disulfide reactive sites (≡Fe-S-S-Fe(III)) was essential for the regeneration of new surface sites through pyrite oxidation. Although Fe(III)-S species was detected at the pyrite surface in the presence of citrate, oxalate and tartrate, Fe(III) complexed with EDTA and salicylate did not strongly interact with the disulfide reactive sites due to the formation of non-sorbing Fe(III)-ligand complexes. The absence of surface Fe(III)-S species indicated that no new reactive sites were generated through Fe redox cycling in the presence of salicylate and EDTA. © 2015 Elsevier Ltd.


PubMed | Canakkale Onsekiz Mart University and NanoMagnetics Instruments Ltd.
Type: | Journal: Water research | Year: 2015

New technologies involving in-situ chemical hexavalent chromium [Cr(VI)] reduction to trivalent chromium [Cr(III)] with natural Fe(II)-containing minerals can offer viable solutions to the treatment of wastewater and subsurface systems contaminated with Cr(VI). Here, the effects of five different chelating agents including citrate, EDTA, oxalate, tartrate and salicylate on reductive Cr(VI) removal from aqueous systems by pyrite were investigated in batch reactors. The Cr(VI) removal was highly dependent on the type of ligand used and chemical conditions (e.g., ligand concentration). While salicylate and EDTA had no or little effect on Cr(VI) removal, the ligands including citrate, tartrate and oxalate significantly enhanced Cr(VI) removal at pH<7 relative to non-ligand systems. In general, the efficiency of organic ligands on Cr(VI) removal decreased in the order: citrateoxalatetartrate>EDTA>salicylatenon-ligand system. Organic ligands enhanced Cr(VI) removal by 1) removing surface oxide layer via the formation of soluble Fe-Cr-ligand complexes, and 2) enhancing the reductive iron redox cycling for the regeneration of new surface sites. While citrate, oxalate and tartrate eliminated the formation of surface Cr (III)-Fe(III)-oxides, the surface phase Cr (III) species was observed in the presence of EDTA and salicylate indicating that Cr(III) complexed with EDTA and salicylate sorbed or precipitated onto pyrite surface, thereby blocking the access of CrO4(2-) to pyrite surface. The binding of Fe(III) with the disulfide reactive sites (Fe-S-S-Fe(III)) was essential for the regeneration of new surface sites through pyrite oxidation. Although Fe(III)-S species was detected at the pyrite surface in the presence of citrate, oxalate and tartrate, Fe(III) complexed with EDTA and salicylate did not strongly interact with the disulfide reactive sites due to the formation of non-sorbing Fe(III)-ligand complexes. The absence of surface Fe(III)-S species indicated that no new reactive sites were generated through Fe redox cycling in the presence of salicylate and EDTA.


Trademark
NanoMagnetics Instruments Ltd. | Date: 2012-02-23

Easy to use scanning tunneling microscope and associated computer operating software sold as a unit.


Trademark
NanoMagnetics Instruments Ltd. | Date: 2012-02-23

Easy to use atomic force microscope and associated computer operating software sold as a unit.

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