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Alain Burgisser - One of the best experts on this subject based on the ideXlab platform.
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Pre-explosive conduit conditions during the 2010 eruption of Merapi volcano (Java, Indonesia)
Geophysical Research Letters, 2016Co-Authors: Mélissa Drignon, Alain Burgisser, Laurent Arbaret, Tonin Bechon, Jean-christophe Komorowski, Caroline Martel, Hayden Miller, Radit YaputraAbstract:The 2010 eruption is the largest explosive event at Merapi volcano since 1872. The high energy of the initial 26 October explosions cannot be explained by simple gravitational collapse and the paroxysmal explosions were preceded by the growth of a lava dome not large enough to ensure significant pressurization of the system. We sampled Pumice from these explosive phases and determined the pre-explosive depths of the Pumices by combining textural analyses with glass water content measurements. Our results indicate that the magma expelled was tapped from depths of several kilometers. Such depths are much greater than those involved in the pre-2010 effusive activity. We propose that the water-rich magma liberated enough gas to sustain the explosivity. Our results imply that the explosive potential of volcanoes having dome-forming, effusive activity is linked to the depth from which fresh magma can be evacuated in a single explosion, regardless of the evacuated volume.
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Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)
Bulletin of Volcanology Bull Volcanic Eruptions, 2010Co-Authors: Wim Degruyter, Olivier Bachmann, Alain BurgisserAbstract:X-ray computed microtomography (μCT) was applied to Pumices from the largest Quaternary explosive eruption of the active South Aegean Arc (the Kos Plateau Tuff; KPT) in order to better understand magma permeability within volcanic conduits. Two different types of Pumices (one with highly elongated bubbles, tube Pumice; and the other with near spherical bubbles, frothy Pumice) produced synchronously and with identical chemical composition were selected for μCT imaging to obtain porosity, tortuosity, bubble size and throat size distributions. Tortuosity drops on average from 2.2 in frothy Pumice to 1.5 in tube Pumice. Bubble size and throat size distributions provide estimates for mean bubble size (~93– 98 μm) and mean throat size (~23–29 μm). Using a modified Kozeny-Carman equation, variations in porosity, tortuosity, and throat size observed in KPT Pumices explain the spread found in laboratory measurements of the Darcian permeability. Measured difference in inertial permeability between tube and frothy Pumices can also be partly explained by the same variables but require an additional parameter related to the internal roughness of the porous medium (friction factor f0). Constitutive equations for both types of permeability allow the quantification of laminar and turbulent gas escape during ascent of rhyolitic magma in volcanic conduits.
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Bubble nucleation, growth and coalescence during the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat
Journal of Volcanology and Geothermal Research, 2010Co-Authors: Thomas Giachetti, Alain Burgisser, Timothy H. Druitt, Laurent Arbaret, C. GalvenAbstract:Soufrière Hills Volcano had two periods of repetitive Vulcanian activity in 1997. Each explosion discharged the contents of the upper 0.5–2 km of the conduit as pyroclastic flows and fallout: frothy Pumices from a deep, gas-rich zone, lava and breadcrust bombs from a degassed lava plug, and dense Pumices from a transition zone. Vesicles constitute 1–66 vol.% of breadcrust bombs and 24–79% of Pumices, all those larger than a few tens of µm being interconnected. Small vesicles (< few tens of µm) in all pyroclasts are interpreted as having formed syn-explosively, as shown by their presence in breadcrust bombs formed from originally non-vesicular magma. Most large vesicles (> few hundreds of µm) in Pumices are interpreted as pre-dating explosion, implying pre-explosive conduit porosities up to 55%. About a sixth of large vesicles in Pumices, and all those in breadcrust bombs, are angular voids formed by syn-explosive fracturing of amphibole phenocrysts. An intermediate-sized vesicle population formed by coalescence of the small syn-explosive bubbles. Bubble nucleation took place heterogeneously on titanomagnetite, number densities of which greatly exceed those of vesicles, and growth took place mainly by decompression. Development of pyroclast vesicle textures was controlled by the time interval between the onset of explosion–decompression and surface quench in contact with air. Lava-plug fragments entered the air quickly after fragmentation (not, vert, similar 10 s), so the interiors continued to vesiculate once the rinds had quenched, forming breadcrust bombs. Deeper, gas-rich magma took longer (not, vert, similar 50 s) to reach the surface, and vesiculation of resulting Pumice clasts was essentially complete prior to surface quench. This accounts for the absence of breadcrusting on Pumice clasts, and for the textural similarity between pyroclastic flow and fallout Pumices, despite different thermal histories after leaving the vent. It also allowed syn-explosive coalescence to proceed further in the Pumices than in the breadcrust bombs. Uniaxial boudinage of amphibole phenocrysts in Pumices implies significant syn-explosive vesiculation even prior to magma fragmentation, probably in a zone of steep pressure gradient beneath the descending fragmentation front. Syn-explosive decompression rates estimated from vesicle number densities (> 0.3–6.5 MPa s− 1) are consistent with those predicted by previously published numerical models.
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Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption
Bulletin of Volcanology Bull Volcanic Eruptions, 2009Co-Authors: Caroline Bouvet De Maisonneuve, Olivier Bachmann, Alain BurgisserAbstract:Silicic Pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of Pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of Pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube Pumices occur throughout the eruption. Less common Pumice types include: (1) “frothy” Pumice (highly porous with large, sub-rounded vesicles), which form 5–10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly “microvesicular” and systematically crystal-poor Pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (
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Characterisation of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a rhyolitic caldera-forming eruption
2007Co-Authors: C. Bouvet, Olivier Bachmann, Alain BurgisserAbstract:AB: Silicic Pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to the fragmentation level, as viscosity is generally high enough to limit their post-fragmentation deformation to a minimum. Pumice textures are therefore of great interest to shed light into bubble nucleation, growth and coalescence in silicic magmas ascending in a volcanic conduit, which ultimately controls the style of eruption. In this study, we have characterised the Pumices produced by the rhyolitic 161 ka Kos Plateau Tuff (KPT) eruption, Aegean Arc, Greece. Four types of Pumices were distinguished macroscopically in the non-welded deposits, and have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the types of Pumices defined are confirmed by distinct petrophysical characteristics, and the measured differences in porosity and permeability are the result of either conduit processes, differences in crystallinity or magma mixing. We also show that permeability does not depend solely on porosity, as implied by the percolation theory. Size of pore aperture, tortuosity and pathway wall rugosity also play a fundamental role in the flow of gas through the permeable magmatic foam.
Mauro Rosi - One of the best experts on this subject based on the ideXlab platform.
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The Plinian phase of the Campanian Ignimbrite eruption (Phlegrean Fields, Italy): evidence from density measurements and textural characterization of Pumice
Bulletin of Volcanology, 2003Co-Authors: Margherita Polacci, Laura Pioli, Mauro RosiAbstract:Textural characterization of Pumice clasts from explosive volcanic eruptions provides constraints on magmatic processes through the quantification of crystal and vesicle content, size, shape, vesicle wall thickness and the degree of interconnectivity. The Plinian fallout deposit directly underlying the Campanian Ignimbrite (CI) eruption represents a suitable case to investigate Pumice products with different textural characteristics and to link the findings to processes accompanying conduit magma ascent to the crater. The deposit consists of a lower (LFU) and upper (UFU) Pumice lapilli bed generated by the sub-steady eruption of trachytic magma with 0.90, with vesicle number density ranging from 10^7–10^8 cm^−3. The degree of vesicle coalescence is high for all Pumice types, with interconnected vesicles generally representing more than 90% of the bulk vesicle population. The results show a high degree of heterogeneous textures among Pumice clasts from both phases of the eruption and within each eruption phase, the different Pumice types and also within each single Pumice type fragment. The origin of Pumice clasts with different textural characteristics is ascribed to the development of conduit regions marked by different rheological behavior. The conclusions of this study are that vesicle deformation, degree of coalescence and intense shear at the conduit walls play a major role on the degassing process, hence affecting the entire conduit dynamics.
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Textural heterogeneities in Pumices from the climactic eruption of Mount Pinatubo, 15 June 1991, and implications for magma ascent dynamics
Bulletin of Volcanology, 2001Co-Authors: Margherita Polacci, Paolo Papale, Mauro RosiAbstract:The climactic event of Mount Pinatubo represents one of the most thoroughly studied eruptions of the century and has provided important insights into the dynamics of explosive volcanism. We have performed detailed textural analyses of the white and gray Pumices of the plinian and pyroclastic flow deposits, and found that differences in color and clast density reflect different crystal and vesicle amounts and size distributions. White Pumice has higher vesicularity, deformed and highly coalesced vesicles with thin walls, euhedral phenocrysts and microlite-free groundmass. Gray Pumice shows lower vesicularity, wider ranges in vesicle number density, limited coalescence, vesicles with thick walls that are less deformed, phenocrysts and microphenocrysts with abundant solution pitting, and groundmass containing ubiquitous microlites and crystal fragments. The presence of white and gray Pumice varieties and the broad range in vesicularity and vesicle number density that characterizes both of them appear to record the complexities of conduit processes such as magma vesiculation and fragmentation and the development of conduit regions marked by different rheological behaviors. In particular, the results of this study suggest the likely importance of intense shear and viscous dissipation at the conduit walls, a mechanism that may be responsible for the creation and discharge of the gray Pumice of this eruption along with the dominant white variety.
M Kitis - One of the best experts on this subject based on the ideXlab platform.
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advanced oxidation of natural organic matter using hydrogen peroxide and iron coated Pumice particles
Chemosphere, 2007Co-Authors: M Kitis, S S KaplanAbstract:The oxidative removal of natural organic matter (NOM) from waters using hydrogen peroxide and iron-coated Pumice particles as heterogeneous catalysts was investigated. Two NOM sources were tested: humic acid solution and a natural source water. Iron coated Pumice removed about half of the dissolved organic carbon (DOC) concentration at a dose of 3000 mg l(-1) in 24 h by adsorption only. Original Pumice and peroxide dosed together provided UV absorbance reductions as high as 49%, mainly due to the presence of metal oxides including Al(2)O(3), Fe(2)O(3) and TiO(2) in the natural Pumice, which are known to catalyze the decomposition of peroxide forming strong oxidants. Coating the original Pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. A strong linear correlation was found between iron contents of coated Pumices and UV absorbance reductions. Peroxide consumption also correlated with UV absorbance reduction. Control experiments proved the effective coating and the stability of iron oxide species bound on Pumice surfaces. Results overall indicated that in addition to adsorptive removal of NOM by metal oxides on Pumice surfaces, surface reactions between iron oxides and peroxide result in the formation of strong oxidants, probably like hydroxyl radicals, which further oxidize both adsorbed NOM and remaining NOM in solution, similar to those in Fenton-like reactions.
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adsorption of natural organic matter from waters by iron coated Pumice
Chemosphere, 2007Co-Authors: M Kitis, S S Kaplan, E Karakaya, Nevzat Yigit, G CivelekogluAbstract:Natural Pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural Pumice source, particle size fraction, Pumice dose, Pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coating overwhelmed the surface electrical properties of the underlying Pumice particles. Surface areas as high as 20.6 m2 g−1 were achieved after iron coating of Pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural Pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area-basis. The smallest size fractions (<63 μm) of coated Pumices generally exhibited the highest NOM uptakes. A strong linear correlation between the iron contents of coated Pumices and their Freundlich affinity parameters (KF) indicated that the enhanced NOM uptake is due to iron oxides bound on Pumice surfaces. Iron oxide coated Pumice surfaces preferentially removed high UV-absorbing fractions of NOM, with UV absorbance reductions up to 90%. Control experiments indicated that iron oxide species bound on Pumice surfaces are stable, and potential iron release to the solution is not a concern at pH values of typical natural waters. Based on high NOM adsorption capacities, iron oxide coated Pumice may be a promising novel adsorbent in removing NOM from waters. Furthermore, due to preferential removal of high UV-absorbing NOM fractions, iron oxide coated Pumice may also be effective in controlling the formation of disinfection by-products in drinking water treatment.
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Adsorption of natural organic matter from waters by iron coated Pumice
Chemosphere, 2006Co-Authors: M Kitis, S S Kaplan, E Karakaya, Nevzat Yigit, G CivelekogluAbstract:Natural Pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural Pumice source, particle size fraction, Pumice dose, Pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coating overwhelmed the surface electrical properties of the underlying Pumice particles. Surface areas as high as 20.6 m2 g−1 were achieved after iron coating of Pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural Pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area-basis. The smallest size fractions (
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heterogeneous catalytic degradation of cyanide using copper impregnated Pumice and hydrogen peroxide
Water Research, 2005Co-Authors: M Kitis, Nevzat Yigit, G Civelekoglu, Emine Karakaya, Ata AkcilAbstract:Abstract The main objective of this research was to investigate the oxidative destruction of free cyanide with hydrogen peroxide and copper-impregnated Pumice as a heterogeneous catalyst. Original or copper-impregnated Pumices added alone were not effective adsorbents of negatively charged cyanide ions due to incompatible surface interactions. Peroxide and original Pumices added together were also ineffective in removing cyanide. However, for all of the three natural Pumices tested with various particle size fractions, the use of copper-impregnated Pumices and peroxide together significantly enhanced both the initial rate and extent of cyanide removal. Although copper-impregnated specific surface area was the major factor affecting the rate and extent of cyanide destruction for a particular Pumice source with similar surface chemistries, the type of surface chemistry (i.e., specific functional groups) within different Pumice sources also appears to be a very important factor. Lower rates and extents of cyanide removals were observed at pH 11 compared to pH 8 probably because of the negative impacts of alkaline conditions in terms of scavenging peroxide and forming more negatively charged Pumice surfaces. Both the initial rate and ultimate extent of cyanide removals were generally higher at a temperature of 20 °C compared with those found at 10 °C. The use of copper-impregnated Pumice as a light, cheap, readily available, natural, and porous heterogeneous catalyst either in completely mixed/suspended or fixed-bed reactor configurations may be an effective treatment technology for cyanide removal from solution. This new approach may minimize downstream metal removal problems experienced in conventional cyanide oxidation technologies.
Thomas Giachetti - One of the best experts on this subject based on the ideXlab platform.
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Submarine giant Pumice: a window into the shallow conduit dynamics of a recent silicic eruption
Bulletin of Volcanology, 2019Co-Authors: Samuel J. Mitchell, Kristen E. Fauria, Meghan R. Jones, Chris E. Conway, Zihan Wei, S. Adam Soule, Rebecca J. Carey, Bruce F. Houghton, Michael Manga, Thomas GiachettiAbstract:Meter-scale vesicular blocks, termed “giant Pumice,” are characteristic primary products of many subaqueous silicic eruptions. The size of giant Pumices allows us to describe meter-scale variations in textures and geochemistry with implications for shearing processes, ascent dynamics, and thermal histories within submarine conduits prior to eruption. The submarine eruption of Havre volcano, Kermadec Arc, in 2012, produced at least 0.1 km^3 of rhyolitic giant Pumice from a single 900-m-deep vent, with blocks up to 10 m in size transported to at least 6 km from source. We sampled and analyzed 29 giant Pumices from the 2012 Havre eruption. Geochemical analyses of whole rock and matrix glass show no evidence for geochemical heterogeneities in parental magma; any textural variations can be attributed to crystallization of phenocrysts and microlites, and degassing. Extensive growth of microlites occurred near conduit walls where magma was then mingled with ascending microlite-poor, low viscosity rhyolite. Meter- to micron-scale textural analyses of giant Pumices identify diversity throughout an individual block and between the exteriors of individual blocks. We identify evidence for post-disruption vesicle growth during Pumice ascent in the water column above the submarine vent. A 2D cumulative strain model with a flared, shallow conduit may explain observed vesicularity contrasts (elongate tube vesicles vs spherical vesicles). Low vesicle number densities in these Pumices from this high-intensity silicic eruption demonstrate the effect of hydrostatic pressure above a deep submarine vent in suppressing rapid late-stage bubble nucleation and inhibiting explosive fragmentation in the shallow conduit.
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Bubble nucleation, growth and coalescence during the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat
Journal of Volcanology and Geothermal Research, 2010Co-Authors: Thomas Giachetti, Alain Burgisser, Timothy H. Druitt, Laurent Arbaret, C. GalvenAbstract:Soufrière Hills Volcano had two periods of repetitive Vulcanian activity in 1997. Each explosion discharged the contents of the upper 0.5–2 km of the conduit as pyroclastic flows and fallout: frothy Pumices from a deep, gas-rich zone, lava and breadcrust bombs from a degassed lava plug, and dense Pumices from a transition zone. Vesicles constitute 1–66 vol.% of breadcrust bombs and 24–79% of Pumices, all those larger than a few tens of µm being interconnected. Small vesicles (< few tens of µm) in all pyroclasts are interpreted as having formed syn-explosively, as shown by their presence in breadcrust bombs formed from originally non-vesicular magma. Most large vesicles (> few hundreds of µm) in Pumices are interpreted as pre-dating explosion, implying pre-explosive conduit porosities up to 55%. About a sixth of large vesicles in Pumices, and all those in breadcrust bombs, are angular voids formed by syn-explosive fracturing of amphibole phenocrysts. An intermediate-sized vesicle population formed by coalescence of the small syn-explosive bubbles. Bubble nucleation took place heterogeneously on titanomagnetite, number densities of which greatly exceed those of vesicles, and growth took place mainly by decompression. Development of pyroclast vesicle textures was controlled by the time interval between the onset of explosion–decompression and surface quench in contact with air. Lava-plug fragments entered the air quickly after fragmentation (not, vert, similar 10 s), so the interiors continued to vesiculate once the rinds had quenched, forming breadcrust bombs. Deeper, gas-rich magma took longer (not, vert, similar 50 s) to reach the surface, and vesiculation of resulting Pumice clasts was essentially complete prior to surface quench. This accounts for the absence of breadcrusting on Pumice clasts, and for the textural similarity between pyroclastic flow and fallout Pumices, despite different thermal histories after leaving the vent. It also allowed syn-explosive coalescence to proceed further in the Pumices than in the breadcrust bombs. Uniaxial boudinage of amphibole phenocrysts in Pumices implies significant syn-explosive vesiculation even prior to magma fragmentation, probably in a zone of steep pressure gradient beneath the descending fragmentation front. Syn-explosive decompression rates estimated from vesicle number densities (> 0.3–6.5 MPa s− 1) are consistent with those predicted by previously published numerical models.
S S Kaplan - One of the best experts on this subject based on the ideXlab platform.
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advanced oxidation of natural organic matter using hydrogen peroxide and iron coated Pumice particles
Chemosphere, 2007Co-Authors: M Kitis, S S KaplanAbstract:The oxidative removal of natural organic matter (NOM) from waters using hydrogen peroxide and iron-coated Pumice particles as heterogeneous catalysts was investigated. Two NOM sources were tested: humic acid solution and a natural source water. Iron coated Pumice removed about half of the dissolved organic carbon (DOC) concentration at a dose of 3000 mg l(-1) in 24 h by adsorption only. Original Pumice and peroxide dosed together provided UV absorbance reductions as high as 49%, mainly due to the presence of metal oxides including Al(2)O(3), Fe(2)O(3) and TiO(2) in the natural Pumice, which are known to catalyze the decomposition of peroxide forming strong oxidants. Coating the original Pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. A strong linear correlation was found between iron contents of coated Pumices and UV absorbance reductions. Peroxide consumption also correlated with UV absorbance reduction. Control experiments proved the effective coating and the stability of iron oxide species bound on Pumice surfaces. Results overall indicated that in addition to adsorptive removal of NOM by metal oxides on Pumice surfaces, surface reactions between iron oxides and peroxide result in the formation of strong oxidants, probably like hydroxyl radicals, which further oxidize both adsorbed NOM and remaining NOM in solution, similar to those in Fenton-like reactions.
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adsorption of natural organic matter from waters by iron coated Pumice
Chemosphere, 2007Co-Authors: M Kitis, S S Kaplan, E Karakaya, Nevzat Yigit, G CivelekogluAbstract:Natural Pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural Pumice source, particle size fraction, Pumice dose, Pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coating overwhelmed the surface electrical properties of the underlying Pumice particles. Surface areas as high as 20.6 m2 g−1 were achieved after iron coating of Pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural Pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area-basis. The smallest size fractions (<63 μm) of coated Pumices generally exhibited the highest NOM uptakes. A strong linear correlation between the iron contents of coated Pumices and their Freundlich affinity parameters (KF) indicated that the enhanced NOM uptake is due to iron oxides bound on Pumice surfaces. Iron oxide coated Pumice surfaces preferentially removed high UV-absorbing fractions of NOM, with UV absorbance reductions up to 90%. Control experiments indicated that iron oxide species bound on Pumice surfaces are stable, and potential iron release to the solution is not a concern at pH values of typical natural waters. Based on high NOM adsorption capacities, iron oxide coated Pumice may be a promising novel adsorbent in removing NOM from waters. Furthermore, due to preferential removal of high UV-absorbing NOM fractions, iron oxide coated Pumice may also be effective in controlling the formation of disinfection by-products in drinking water treatment.
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Adsorption of natural organic matter from waters by iron coated Pumice
Chemosphere, 2006Co-Authors: M Kitis, S S Kaplan, E Karakaya, Nevzat Yigit, G CivelekogluAbstract:Natural Pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural Pumice source, particle size fraction, Pumice dose, Pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coating overwhelmed the surface electrical properties of the underlying Pumice particles. Surface areas as high as 20.6 m2 g−1 were achieved after iron coating of Pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural Pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area-basis. The smallest size fractions (
