Abstract:The relative adsorption of fluoroxanthates on several different coal pyrites has been found to depend on the degree to which the pyrite surfaces are oxidized. Maximum xanthate adsorption occurs in the absence of pyrite surface oxidation and is affected by the presence of polysulfides and metal‐deficient sulfides on the pyrite surface. The structure and electronic properties of the xanthate molecule may also affect its adsorption. 3‐(Trifluoromethyl)benzyl xanthate was found to selectively adsorb on pyrite vs. … Show more
“…In addition, parts c and f of Figure S1 in the SI show the sulfur spectra (S 2p) of fresh and deactivated surfaces, respectively. Sulfur was not detectable on the fresh nZVI surface compared to a significant detectable sulfur peak on the deactivated nZVI surface at a BE of 168.6 eV, which implies the presence of sulfur as sulfate (e.g., FeSO 4 , Fe 2 (SO 4 ) 3 ) rather than sulfide (e.g., FeS, FeS 2 ) or other sulfur forms. ,− In the peer-reviewed literature, ,, the reference peaks of FeSO 4 in the sulfur spectra (S 2p) were detected at 169.0 (±0.2) eV. Therefore, ferrous sulfate (FeSO 4 ) is most likely formed on the deactivated nZVI surface.…”
Recently, persulfate has caught the attention of groundwater remediation practitioners as a promising oxidant for in situ chemical oxidation. In this study, a method was applied to treat a selection of hazardous organic compounds using nanoscale zerovalent iron (nZVI) particles as activators for persulfate. The results show that degradation of these organic compounds using nZVI-activated persulfate is more effective than nZVI alone. For example, the degradation of naphthalene by nZVI-activated persulfate was >99% compared to <10% by nZVI alone. Despite the higher effectiveness, the nZVI particles were passivated quickly following exposure to persulfate, causing the reaction rate to reduce to a magnitude representative of an unactivated persulfate system. X-ray photoelectron spectroscopy analyses indicated that an iron sulfate layer was formed on the nZVI particle surfaces following exposure to persulfate compared to the FeOOH layer that was present on the fresh nZVI surfaces. Although the nZVI particle surfaces are passivated, nZVI appears to be a promising persulfate activator compared to the conventional persulfate activators such as Fe 2+ and granular ZVI.
“…In addition, parts c and f of Figure S1 in the SI show the sulfur spectra (S 2p) of fresh and deactivated surfaces, respectively. Sulfur was not detectable on the fresh nZVI surface compared to a significant detectable sulfur peak on the deactivated nZVI surface at a BE of 168.6 eV, which implies the presence of sulfur as sulfate (e.g., FeSO 4 , Fe 2 (SO 4 ) 3 ) rather than sulfide (e.g., FeS, FeS 2 ) or other sulfur forms. ,− In the peer-reviewed literature, ,, the reference peaks of FeSO 4 in the sulfur spectra (S 2p) were detected at 169.0 (±0.2) eV. Therefore, ferrous sulfate (FeSO 4 ) is most likely formed on the deactivated nZVI surface.…”
Recently, persulfate has caught the attention of groundwater remediation practitioners as a promising oxidant for in situ chemical oxidation. In this study, a method was applied to treat a selection of hazardous organic compounds using nanoscale zerovalent iron (nZVI) particles as activators for persulfate. The results show that degradation of these organic compounds using nZVI-activated persulfate is more effective than nZVI alone. For example, the degradation of naphthalene by nZVI-activated persulfate was >99% compared to <10% by nZVI alone. Despite the higher effectiveness, the nZVI particles were passivated quickly following exposure to persulfate, causing the reaction rate to reduce to a magnitude representative of an unactivated persulfate system. X-ray photoelectron spectroscopy analyses indicated that an iron sulfate layer was formed on the nZVI particle surfaces following exposure to persulfate compared to the FeOOH layer that was present on the fresh nZVI surfaces. Although the nZVI particle surfaces are passivated, nZVI appears to be a promising persulfate activator compared to the conventional persulfate activators such as Fe 2+ and granular ZVI.
“…According to the literature and blank experiments using different kinds of iron species, the former set of spectra are possibly assigned to magnetite, although it is dangerous to conclude the kind of species only by the chemical shift in the XPS. Baltrus and Diehl have assigned similar spectra to a mixture of Fe 2+ and Fe 3+ from pyrite oxidation . On the other hand, the latter reduced species is considered to be pyrrhotite or troilite .…”
Section: Resultsmentioning
confidence: 98%
“…On the other hand, the latter reduced species is considered to be pyrrhotite or troilite . The S(2p) spectra showed the peaks of elemental sulfur and sulfide on the outer surface, whereas in the inside of the residue, only the peaks of sulfide were observed. − One of possible reasons why the depth profile of the iron species was markedly changed is the oxidation of “surface” iron species into magnetite by water. 9 Effects of catalyst precursor on XPS spectra of the residue from Wandoan coal and vacuum residue using syngas−water.…”
Section: Resultsmentioning
confidence: 99%
“…Baltrus and Diehl have assigned similar spectra to a mixture of Fe 2+ and Fe 3+ from pyrite oxidation. 45 On the other hand, the latter reduced species is considered to be pyrrhotite or troilite. 44 The S(2p) spectra showed the peaks of elemental sulfur and sulfide on the outer surface, whereas in the inside of the residue, only the peaks of sulfide were observed.…”
Section: Resultsmentioning
confidence: 99%
“…44 The S(2p) spectra showed the peaks of elemental sulfur and sulfide on the outer surface, whereas in the inside of the residue, only the peaks of sulfide were observed. [43][44][45] One of possible reasons why the depth profile of the iron species was markedly changed is the oxidation of "surface" iron species into magnetite by water.…”
The effectiveness of alternative hydrogen sources compared to pressurized hydrogen gas toward the coprocessing of coals and vacuum residues was investigated in the presence of different kinds of iron-based catalyst precursors. The reactions in syngas-water using pentacarbonyliron or synthetic pyrite achieved high rates of conversion to THF solubles comparable to those in pressurized hydrogen gas, indicating the presence of the synergistic effects of the two hydrogen sources, hydrogen gas and carbon monoxide-water. Under hydrogen gas, addition of water greatly increased the yields of the desired fractions. The Fe(CO) 5 -catalyzed coprocessing of a vacuum residue of Arabian Heavy and Wandoan coal (2:1, 400 °C, 60 min, H 2 3.0 MPa, CO 3.0 MPa, water 0.5 g) in combination with the pretreatment at lower temperature (200 °C, 30 min) afforded the high yields of THF-soluble (100%) and n-hexane-soluble (69.5%) matter. At higher reaction temperatures, 425-450 °C, the use of Fe(CO) 5 with sulfur or synthetic pyrite afforded much better rates of conversion than Fe(CO) 5 without sulfur. The XRD and XPS analyses revealed the formation of a mixture of magnetite and pyrrhotite from Fe(CO) 5 without sulfur, and the surface of the used catalyst was mainly covered with iron species in a relatively high oxidation state. On the other hand, pyrrhotite was formed from Fe(CO) 5 with sulfur or synthetic pyrite. The gas consumption, eventually the efficiency of the coprocessing, was estimated to be influenced by such changes in the state of the catalyst surface.
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