Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus ... more Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus in natural waterbodies. Slag has been applied for the phosphorus removal by several mechanisms. In this study, sodium hydroxide coating was applied on the slag surface to enhance the efficiency of precipitation-coagulation process. In the batch test, it was found that the capacity of the slag to maintain high pH decreases with increasing its exposure time to the aqueous solution. In the column test, the coarse-grained coated slag showed higher phosphorus removal efficiency than the fine-grained uncoated slag. The coated slag maintained pH higher than uncoated slag and, accordingly, the removal efficiency of phosphorus was higher. Especially, when pH was less than 8, the removal efficiency decreased significantly. However, coated slag provided an excess amount of aluminum and sodium. Thus, a return process to reuse aluminum and sodium as a coagulant was introduced. The return process yiel...
Phosphorus is one of the elements that have a significant impact on such environmental problems a... more Phosphorus is one of the elements that have a significant impact on such environmental problems as eutrophication or algal bloom. Phosphorus compounds in water can be hydrolyzed to orthophosphate that is the only form of phosphorus that algae can assimilate. In this study, phosphorus removal in terms of orthophosphate and total phosphorus from wastewater was studied using alum or ferric ions as coagulants. It was observed that alum shows higher phosphorus removal efficiency than ferric ions in the same mole ratio concentrations. The proportion of orthophosphate among total phosphorus did not change significantly during coagulation process when the coagulant concentration is low. However, the proportion becomes gradually decreased as the coagulant concentration increases. Not only the electrolyte concentration difference in solution, but the characteristics of orthophosphate and polyphosphate such as reactivity and ionic size might also cause the differences in the removal rate. Orth...
We recently reported that C(60) aminofullerenes immobilized on silica support (aminoC(60)/silica)... more We recently reported that C(60) aminofullerenes immobilized on silica support (aminoC(60)/silica) efficiently produce singlet oxygen ((1)O(2)) and inactivate virus and bacteria under visible light irradiation. (1) We herein evaluate this new photocatalyst for oxidative degradation of 11 emerging organic contaminants, including pharmaceuticals such as acetaminophen, carbamazepine, cimetidine, propranolol, ranitidine, sulfisoxazole, and trimethoprim, and endocrine disruptors such as bisphenol A and pentachlorophenol. Tetrakis aminoC(60)/silica degraded pharmaceuticals under visible light irradiation faster than common semiconductor photocatalysts such as platinized WO(3) and carbon-doped TiO(2). Furthermore, aminoC(60)/silica exhibited high target-specificity without significant interference by natural organic matter. AminoC(60)/silica was more efficient than unsupported (water-suspended) C(60) aminofullerene. This was attributed to kinetically enhanced (1)O(2) production after immobilization, which reduces agglomeration of the photocatalyst, and to adsorption of pharmaceuticals onto the silica support, which increases exposure to (1)O(2) near photocatalytic sites. Removal efficiency increased with pH for contaminants with a phenolic moiety, such as bisphenol A and acetaminophen, because the electron-rich phenolates that form at alkaline pH are more vulnerable to singlet oxygenation.
The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently u... more The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently used synthetic filter materials, on depth filtration performance was investigated.
Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles wi... more Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.
Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was ... more Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was experimentally and theoretically investigated in this study. Topography analysis via atomic force microscopy (AFM) and electron microscopy indicates that Bt spores are rod shaped, approximately 1.3 mum in length and approximately 0.8 mum in diameter. The adhesion force of Bt spores and silica particles on gold-coated glass was measured at various relative humidity (RH) levels by AFM. It was expected that the adhesion force would vary with RH because the individual force components contributing to the adhesion force depend on RH. The adhesion force between a particle and a planar surface in atmospheric environments was modeled as the contribution of three major force components: capillary, van der Waals, and electrostatic interaction forces. Adhesion force measurements for Bt spore (silica particle) and the gold surface system were comparable with calculations. Modeling results show that there is a critical RH value, which depends on the hydrophobicity of the materials involved, below which the water meniscus does not form and the contribution of the capillary force is zero. As RH increases, the van der Waals force decreases while the capillary force increases to a maximum value.
A laser beam is focused on the cantilever tip, and the position movement of the reflected spot is... more A laser beam is focused on the cantilever tip, and the position movement of the reflected spot is monitored via a position-sensitive detector (PSD). The PSD is connected to an oscilloscope for direct observation of the signal and to a computer for data acquisition. . Resonance frequency shift of (a) cantilever C5 and (b) cantilever C3.
Although some differences have been observed, the transport behavior of radioactive aerosol parti... more Although some differences have been observed, the transport behavior of radioactive aerosol particles has often been assumed to be analogous to the behavior of nonradioactive aerosols in dispersion models. However, radioactive particles can become electrostatically charged as a result of the decay process. Theories have been proposed to describe this self-charging phenomenon, which may have a significant effect on how these particles interact with one another and with charged surfaces in the environment. In this study, atomic force microscopy (AFM) was employed to quantify surface forces between a particle and a planar surface and to compare measurements with and without the involvement of radioactivity. The main objective of this work is to assess directly the effects of radioactivity on the surface interactions of radioactive aerosols via the measurement of the adhesion force. The adhesion force between a silicon nitride AFM tip and an activated gold substrate was measured so that any possible effects due to radioactivity could be observed. The adhesion force between the tip and the gold surface increased significantly when the gold substrate (25 mm(2) surface area) was activated to a level of approximately 0.6 mCi. The results of this investigation will prompt further work into the effects of radioactivity in particle-surface interactions.
The adhesion of spores of Bacillus anthracis -the cause of anthrax and a likely biological threat... more The adhesion of spores of Bacillus anthracis -the cause of anthrax and a likely biological threat -to solid surfaces is an important consideration in cleanup after an accidental or deliberate release. However, because of safety concerns, directly studying B. anthracis spores with advanced instrumentation is problematic. As a first step, we are examining the electrostatic potential of Bacillus thuringiensis (Bt), which is a closely related species that is often used as a simulant to study B. anthracis. Scanning surface potential microscopy (SSPM), also known as Kelvin probe force microscopy (KPFM), was used to investigate the influence of relative humidity (RH) on the surface electrostatic potential of Bt that had adhered to silica, mica, or gold substrates. AFM/SSPM side-by-side images were obtained separately in air, at various values of RH, after an aqueous droplet with spores was applied on each surface and allowed to dry before measurements. In the SSPM images, a negative potential on the surface of the spores was observed compared with that of the substrates. The surface potential decreased as the humidity increased. Spores were unable to adhere to a surface with an extremely negative potential, such as mica.
Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus ... more Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus in natural waterbodies. Slag has been applied for the phosphorus removal by several mechanisms. In this study, sodium hydroxide coating was applied on the slag surface to enhance the efficiency of precipitation-coagulation process. In the batch test, it was found that the capacity of the slag to maintain high pH decreases with increasing its exposure time to the aqueous solution. In the column test, the coarse-grained coated slag showed higher phosphorus removal efficiency than the fine-grained uncoated slag. The coated slag maintained pH higher than uncoated slag and, accordingly, the removal efficiency of phosphorus was higher. Especially, when pH was less than 8, the removal efficiency decreased significantly. However, coated slag provided an excess amount of aluminum and sodium. Thus, a return process to reuse aluminum and sodium as a coagulant was introduced. The return process yiel...
Phosphorus is one of the elements that have a significant impact on such environmental problems a... more Phosphorus is one of the elements that have a significant impact on such environmental problems as eutrophication or algal bloom. Phosphorus compounds in water can be hydrolyzed to orthophosphate that is the only form of phosphorus that algae can assimilate. In this study, phosphorus removal in terms of orthophosphate and total phosphorus from wastewater was studied using alum or ferric ions as coagulants. It was observed that alum shows higher phosphorus removal efficiency than ferric ions in the same mole ratio concentrations. The proportion of orthophosphate among total phosphorus did not change significantly during coagulation process when the coagulant concentration is low. However, the proportion becomes gradually decreased as the coagulant concentration increases. Not only the electrolyte concentration difference in solution, but the characteristics of orthophosphate and polyphosphate such as reactivity and ionic size might also cause the differences in the removal rate. Orth...
We recently reported that C(60) aminofullerenes immobilized on silica support (aminoC(60)/silica)... more We recently reported that C(60) aminofullerenes immobilized on silica support (aminoC(60)/silica) efficiently produce singlet oxygen ((1)O(2)) and inactivate virus and bacteria under visible light irradiation. (1) We herein evaluate this new photocatalyst for oxidative degradation of 11 emerging organic contaminants, including pharmaceuticals such as acetaminophen, carbamazepine, cimetidine, propranolol, ranitidine, sulfisoxazole, and trimethoprim, and endocrine disruptors such as bisphenol A and pentachlorophenol. Tetrakis aminoC(60)/silica degraded pharmaceuticals under visible light irradiation faster than common semiconductor photocatalysts such as platinized WO(3) and carbon-doped TiO(2). Furthermore, aminoC(60)/silica exhibited high target-specificity without significant interference by natural organic matter. AminoC(60)/silica was more efficient than unsupported (water-suspended) C(60) aminofullerene. This was attributed to kinetically enhanced (1)O(2) production after immobilization, which reduces agglomeration of the photocatalyst, and to adsorption of pharmaceuticals onto the silica support, which increases exposure to (1)O(2) near photocatalytic sites. Removal efficiency increased with pH for contaminants with a phenolic moiety, such as bisphenol A and acetaminophen, because the electron-rich phenolates that form at alkaline pH are more vulnerable to singlet oxygenation.
The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently u... more The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently used synthetic filter materials, on depth filtration performance was investigated.
Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles wi... more Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.
Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was ... more Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was experimentally and theoretically investigated in this study. Topography analysis via atomic force microscopy (AFM) and electron microscopy indicates that Bt spores are rod shaped, approximately 1.3 mum in length and approximately 0.8 mum in diameter. The adhesion force of Bt spores and silica particles on gold-coated glass was measured at various relative humidity (RH) levels by AFM. It was expected that the adhesion force would vary with RH because the individual force components contributing to the adhesion force depend on RH. The adhesion force between a particle and a planar surface in atmospheric environments was modeled as the contribution of three major force components: capillary, van der Waals, and electrostatic interaction forces. Adhesion force measurements for Bt spore (silica particle) and the gold surface system were comparable with calculations. Modeling results show that there is a critical RH value, which depends on the hydrophobicity of the materials involved, below which the water meniscus does not form and the contribution of the capillary force is zero. As RH increases, the van der Waals force decreases while the capillary force increases to a maximum value.
A laser beam is focused on the cantilever tip, and the position movement of the reflected spot is... more A laser beam is focused on the cantilever tip, and the position movement of the reflected spot is monitored via a position-sensitive detector (PSD). The PSD is connected to an oscilloscope for direct observation of the signal and to a computer for data acquisition. . Resonance frequency shift of (a) cantilever C5 and (b) cantilever C3.
Although some differences have been observed, the transport behavior of radioactive aerosol parti... more Although some differences have been observed, the transport behavior of radioactive aerosol particles has often been assumed to be analogous to the behavior of nonradioactive aerosols in dispersion models. However, radioactive particles can become electrostatically charged as a result of the decay process. Theories have been proposed to describe this self-charging phenomenon, which may have a significant effect on how these particles interact with one another and with charged surfaces in the environment. In this study, atomic force microscopy (AFM) was employed to quantify surface forces between a particle and a planar surface and to compare measurements with and without the involvement of radioactivity. The main objective of this work is to assess directly the effects of radioactivity on the surface interactions of radioactive aerosols via the measurement of the adhesion force. The adhesion force between a silicon nitride AFM tip and an activated gold substrate was measured so that any possible effects due to radioactivity could be observed. The adhesion force between the tip and the gold surface increased significantly when the gold substrate (25 mm(2) surface area) was activated to a level of approximately 0.6 mCi. The results of this investigation will prompt further work into the effects of radioactivity in particle-surface interactions.
The adhesion of spores of Bacillus anthracis -the cause of anthrax and a likely biological threat... more The adhesion of spores of Bacillus anthracis -the cause of anthrax and a likely biological threat -to solid surfaces is an important consideration in cleanup after an accidental or deliberate release. However, because of safety concerns, directly studying B. anthracis spores with advanced instrumentation is problematic. As a first step, we are examining the electrostatic potential of Bacillus thuringiensis (Bt), which is a closely related species that is often used as a simulant to study B. anthracis. Scanning surface potential microscopy (SSPM), also known as Kelvin probe force microscopy (KPFM), was used to investigate the influence of relative humidity (RH) on the surface electrostatic potential of Bt that had adhered to silica, mica, or gold substrates. AFM/SSPM side-by-side images were obtained separately in air, at various values of RH, after an aqueous droplet with spores was applied on each surface and allowed to dry before measurements. In the SSPM images, a negative potential on the surface of the spores was observed compared with that of the substrates. The surface potential decreased as the humidity increased. Spores were unable to adhere to a surface with an extremely negative potential, such as mica.
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