R-3 Repository :: Browsing by Author "Wiesner, Mark R."

Browsing by Author "Wiesner, Mark R."

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A cost model for membrane filtration
(1992) Pickering, Karen Dunphy; Wiesner, Mark R.
A model is developed that calculates capital and operating cost of cross-flow membrane filtration as a function of relevant design parameters. An expression for capital cost is empirically derived from information gathered from membrane manufacturers. Operating cost is divided into components for energy consumption, chemical demand, membrane replacement and concentrate disposal and is determined from attributes of the membrane system. The effect of operating parameters and membrane characteristics on cost are examined. The flux of permeate across a membrane is the principle factor determining cost. Energy cost, although important to the daily operating cost of a water treatment plant, is overshadowed by the membrane replacement cost. The effect of backflushing procedures on cost is evaluated using empirical functions for permeate flux derived from a microfiltration pilot study. Microfiltration is determined to be a cost-competitive alternative to ultrafiltration. Costs calculated by this study are compared to reported costs for membrane filtration.
A model packed bed filtration
(2000) Okhuysen, Mary Ann; Wiesner, Mark R.
A mathematical simulation model is developed that calculates the evolution of particle removal and headloss in a packed bed filter, as functions of the morphology of the colloidal particle deposits in the filter. The expressions derived are based on the postulate that particles form deposits that grow as mass fractals. The model is calibrated and validated with a set of laboratory data previously obtained. The calibrated value of fractal dimension was found to coincide with measurements obtained in an earlier study using light scattering. The effect of the filtration velocity and particle size on the fractal dimension of the deposits is evaluated. The hypothesis that higher filtration velocities create denser deposits is supported. However, a trend of increasing fractal dimension with decreasing particle size runs counter to theoretical expectations. The model is extended to include the effect of variable conditions in the influent.
An evaluation of produced water treatment and the associated costs
(1996) Hackney, John Michael; Wiesner, Mark R.
Produced waters are characterized with respect to the amounts and chemical constituents generated in oil and gas production. Removal of portions of total suspended solids, total dissolved solids, volatile organic chemicals, and adsorbable organic chemicals were simulated and costs associated with each treatment scenario have been estimated. Treatment facility size is a key parameter in determining unit cost. Desalination was the most costly process evaluated. Produced water treatment costs range from $0.25 to \$35.00/m$\sp3$ and are dependent on the nature and level of treatment. Under the most cost-effective scenario, the industry-wide cost of removing emulsified oils and dissolved organic materials to a level suitable for coastal discharge is approximately $4.00 \$/m$\sp3$. This translates to an annual industry-wide cost of some twenty billion dollars. Costs for reclaiming produced water for agricultural purposes may be as high as $35.00/m$ sp3$ due to desalting costs.
Characteristics of ceramic membranes derived from metal-oxide nanoparticles
(2001) Fidalgo, Maria Marta; Wiesner, Mark R.
Carboxylate alumoxanes were cast onto alpha-alumina supports by slip-coating to develop asymmetric ceramic membranes. Carboxylate ferroxanes were also analyzed as possible precursor for ceramic membranes. Different support materials were studied. Membrane layers as thin as 1 or 2 mum were achieved. The effect of sintering conditions was investigated. The molecular weight cut off was evaluated for these membranes and compared to pore size data obtained by nitrogen adsorption in an effort to correlate pore size and actual performance of the membrane. Membranes were sintered at temperatures between 600°C and 1100°C. The pore sizes increased with higher sintering temperature, from 7 nm at 600°C to 10 nm at 1000°C, followed by a sharp increase due to the transformation to alpha alumina at higher firing temperatures. The molecular weight cut off showed no considerable variation up to 1000°C. These results are in good agreement with equations reported by several authors that correlate molecular weight with size.
Characterization of alumina membranes derived from alumoxanes
(1999) Bailey, Diane Amy; Wiesner, Mark R.
Alumoxane-derived membranes are characterized and compared with commercial anodized alumina and polycarbonate track-etched membranes. The alumoxane-derived membranes were produced using two different types of ligands, acetic acid and (methoxyethoxy)acetic acid, or mixes of the two to alter the membrane characteristics. Membranes were studied using scanning electron microscopy, atomic force microscopy, nitrogen adsorption-desorption, cleanwater flux experiments, goniometer measurements, and Zeta-meter measurements to determine membrane morphology, pore size distribution and shape, permeability, hydrophobicity, and surface charge. Alumoxane-derived membranes were found to have a nodular morphology with over 90% of pores between 5 and 25 nm and permeability ranging from 0.3 to 1.5 nm$\sp2$. The two ligands used did not produce large differences in the overall characteristics of the membranes. Alumoxane-derived membranes exhibited similar permeabilities to the commercial membranes tested. Carboxylate-alumoxanes show considerable promise as precursors to membranes and other alumina products.
Characterization of particles, metals and water quality in urban runoff
(1994) Characklis, Gregory William; Wiesner, Mark R.
This study was designed to characterize the quality of Houston area stormwater and its potential impact on receiving waters, including Galveston Bay. Stormwater samples were analyzed with regard to standard water quality parameters, as well as for metals. Large increases in the concentration of particles, suspended solids, organic carbon, iron, mercury and zinc were observed in storm runoff. Concentrations of barium and strontium, which occur naturally in area soils, decreased as result of a storm. Data suggested a link between increasing concentrations of smaller solids (0.45-20$\mu$m) and that of iron and mercury. Organic carbon showed evidence of being similarly related to zinc and larger solids ($>$20$\mu$m). Higher concentrations of these materials, in conjunction with increased runoff flows, resulted in storm loadings equivalent to months or even years of background flow. Particle size distributions measured in situ and laboratory simulations indicated significant aggregation in the runoff stream.
Collision efficiency of colloidal particles and morphology of deposits: Implications for membrane filtration
(2001) Tarabara, Volodymyr Valentinovich; Wiesner, Mark R.
On-lattice Monte Carlo simulations were performed to investigate the effect of collision efficiencies alpha of particles on the morphology of heterodeposits. The model predicts that the structure and surface chemistry of such deposits are determined by particles with large and small values of alpha, correspondingly. The case of homodeposition onto a rough substrate was also studied. The best "memory" of the deposit measured as a rate of decay of the Fourier amplitude corresponding to the wavelength of the initial roughness, was found to correspond to intermediate values of alpha. Cross-flow membrane filtration experiments using monodisperse latex suspensions were performed for validation of the Sethi's extended model. A slightly more complex structure at the cake-suspension interface was hypothesized to explain differences between model calculations and experiments. A representation of the cake with a gradually changing solids concentration allowed for better matching of the extended model and experimental results for particles diffusively depositing onto membrane.
Colloidal fouling of membrane filters: Constant transmembrane pressure versus constant permeate flux
(2000) Hovinga, Rik Martyn; Wiesner, Mark R.
A previously developed model describing colloidal fouling of membrane filters (Sethi, 1997) predicts that operation under conditions of constant transmembrane pressure should result in less fouling than operation at constant permeate flux. These predictions were tested in a series of laboratory experiments. The influence of particle size and mode of operation on the specific permeate flux performance of a cross-flow flat slit membrane unit, was evaluated using an ultra-filtration membrane mounted in an existing Osmonics SEPA CF membrane module. Experiments of three hours in duration were conducted with polystyrene latex particles (100 nm, 430 nm, and 1000 nm) which resulted in a strong correlation between particle size and specific permeate flux. Consistent with theoretical prediction, less fouling was observed in a constant pressure mode of operation. However difference in between the two modes of operation with different particle sizes were not as great as anticipated. Indications for a strong influence of the flowing layer on the specific permeate flux performance were found for the 1000 nm particles. Future research for a better understanding of the role of the flowing layer and cake resistance in membrane fouling is needed and recommended.
Development of nanostructured membranes for environmental applications
(2004) Cortalezzi, Marta Fidalgo; Wiesner, Mark R.
Two new methods for the fabrication of porous membranes were studied. Ceramic membranes were obtained from alumoxane and ferroxane nanoparticles casted onto porous support materials. The synthesis of ferroxane nanoparticles was further investigated, in particular the kinetics of the reaction and the structure of the materials obtained by particle size measurements and EXAFS. The ceramics were characterized by nitrogen absorption isotherms, scanning electron microscope, and atomic force microscope. The permeability and molecular weight cut off (MWCO) of the ferroxane derived membranes were measured. These membranes have an average pore size of 24 run and a MWCO of 180,000 Daltons, which corresponds to the ultrafiltration range. The ferroxane nanoparticles were reacted with compounds containing other metallic atoms and mixed metal oxide nanoparticles were obtained. The nanoparticles can be applied to the fabrication of mixed metal oxide ceramics used in catalysis, fuel cells and other applications. The conductivity and surface acidity were determined in order to evaluate these materials as possible proton exchange membranes for fuel cells. The second fabrication method considered in this study is the template-derived process. Deposits of silica nanoparticles of variable morphology were prepared to be used as templates for porous membranes. The variables that control the morphology of the deposits were investigated, in particular those related to the solvent chemistry of the nanoparticle suspensions. The templates were obtained by self-assembly and Langmuir-Blodgett layer-by-layer deposition. By controlling the template deposition process, the self-assembly method was used to create dendritic templates with an asymmetric structure. The Langmuir-Blodgett technique was used to create bilayers of different pore size. Polystyrene membranes were fabricated as replicas of these template structures. The pore structure of the polymeric membranes was studied by scanning electron microscopy.
Development of novel membrane for proton exchange membrane fuel cell using nanostructured ferroxanes
(2005) Tsui, Eliza M.; Wiesner, Mark R.
An iron-based ceramic material is shown to have excellent properties as an electrolyte material for proton exchange membrane in fuel cells. These membranes have comparable conductivity to the NafionRTM membrane with the advantages of lower material costs, and the ability to operate at higher temperatures. Iron oxide nanoparticles (ferroxane) were prepared as precursor materials for membrane fabrication. The structure of ferroxane-derived ceramics was characterized with FTIR, SEM, TEM, and nitrogen adsorption-desorption. Protonic conductivity of the membranes was studied by electrochemical impedance spectroscopy (EIS) to determine their feasibility in fuel cell applications. The conductivity improved as relative humidity increased. Conductivities of sintered samples were significantly higher than those of green bodies. However, sintered samples were less dependent on relative humidity, which would make their performance more reliable than other ceramic materials and Nafion. The protonic conductivity of ferroxane derived ceramics fired at 300°C (ranged from 2.31 to 2.65 x 10-2 S/cm at relative humidities of 58% to 100%). The values are comparable to the conductivities of Nafion membranes.
Filtration of polydisperse suspensions
(1991) Veerapaneni, Srinivas; Wiesner, Mark R.
The effect of polydispersivity of the influent suspension on the ripening stage of a granular media filter has been studied experimentally. Suspensions of spherical latex particles of sizes 0.09$\mu$m, 0.944$\mu$m and 7.04$\mu$m were filtered through a porous bed of glass spheres, under well controlled physical and chemical conditions. Effluent concentrations and headloss development were monitored. The presence of small particles is observed to improve the removal of large particles, while the removal of small particles is not enhanced by the presence of large particles. Relative particle removal appears to be predictable based on the surface area available in the bed for deposition to take place. Deposition morphology and relative distribution of the mass in the bed play an important role in headloss development during filtration of polydisperse suspensions. If smaller particles are present in the filter influent, the practice of "filter to waste" should improve the initial removal of particles near 1$\mu$m in diameter that might otherwise be poorly removed by clean filter beds.
Fluid mechanics and particle transport in a channel with one porous wall: Application to membrane filtration
(1991) Chellam, Shankararaman; Wiesner, Mark R.
Fluid mechanics of a channel with one porous wall was studied from first principles as the initial step towards understanding polarization phenomena in membrane modules. A regular perturbation method was used to solve the steady-state Navier-Stokes equations for an incompressible, constant property fluid in two dimensions with uniform suction and slip at the permeable boundary. The effects of solute and hydrodynamic parameters on concentration polarization during potable water treatment applications are investigated numerically. Inertia dominated and permeation drag dominated particle transport is discussed. Experimentally determined residence time distributions of particles in a microporous channel are interpreted in the light of inertial and permeation forces. Inertial lift theory is shown to predict initial particle transport. Experimentally observed long trailing edges in particle residence time distributions indicate the importance of other transport mechanisms even in dilute suspension mechanics. It is seen that inertial effects are negligible under conditions typical of microfiltration.
Formation and morphology of colloidal deposits in porous media
(1996) Veerapaneni, Srinivas; Wiesner, Mark R.
The effects of physical parameters such as fluid velocity, particle size and influent particle concentration on the morphology of colloidal deposits, removal efficiency and head loss development in porous media are investigated. Monte Carlo (MC) simulations of colloid deposition on a one-dimensional permeable surface from a uniform flow field and on an impermeable one-dimensional surface in plane stagnation flow are performed. Simulation results indicate that (i) the morphology of the deposits formed in uniform flow field vary from open porous structure for small particles and low fluid velocities to compact structure with increase in particle size and fluid velocity and, (ii) the shape and structure of deposits formed in stagnation flow strongly depend on particle size and fluid velocity. At low velocities in stagnation flow, large particles form compact deposits while small particles form open porous structures. At high velocities, large particles form unstable pillar-like structure with fewer particles quickly building up the height of the deposit while smaller particles form fewer and more dense columns. Experimental observations of monodispersed latex particles filtered through a bed of spherical glass beads indicated that at high flow rates, influent particle concentration did not appear to have significant effect on the removal efficiency of the packed beds or on the head loss development as a function of retained particle mass. At low flow rates ($<$0.1 cm/sec), most of the head loss was observed to occur in the top section of the bed. At high flow rates, the particle deposition was relatively more uniform along the depth of the bed. The fractal dimensions of the deposits was observed to vary from 1.6 to 2.4 with increasing fluid velocity from 0.002 to 0.4 cm/sec. A window of low fractal dimensions was observed at intermediate flow rates (0.04-0.15 cm/sec). It is hypothesized that in this flow regime, deposits may have attained pillar-like structures, similar to those observed in simulations. The fractal dimensions of such columnar structures are expected to be low.
Fouling of ultrafiltration and nanofiltration membranes by dissolved organic matter
(2000) Mackey, Erin Devitt; Wiesner, Mark R.
Fouling is the drop in permeate flux per unit of applied pressure due to the accumulation of materials in the pores and on the surface of the membrane. Dissolved organic matter (DOM) in natural waters is often an important factor in irreversible fouling of membranes. This work characterizes fouling of nanofiltration and ultrafiltration membranes by compounds selected as models for the polysaccharide, polyhydroxyaromatic: and proteinaceous fractions of DOM commonly obtained by pyrolysis-GC/MS. Polygalacturonic acid, rosolic acid and bovine serum albumin were selected as model compounds. Although proteins have been observed to foul membranes, pyrolysis-GC/MS analysis alone of DOM extracted from foulant cakes on membranes yields relatively little proteinaceous material. It was hypothesized that proteins are more significant foulants than is indicated by pyrolysis-GC/MS analysis of the foulant cakes. It was also hypothesized that mixtures of organic molecules would not foul the membrane to the same extent as they will separately and that these flux-reducing foulants were both in the pores and on the surface. Membranes were employed in a dead-end filtration configuration. Surface topology was characterized using atomic force microscopy, the data from which was used to calculate surface roughness by a multifractal analysis algorithm. Foulant location was investigated using infrared spectroscopy with attenuated total reflectance. These laboratory data were compared to pilot plant data collected at the San Patricio Municipal Water District (SPMWD). Long-chain PgA molecules and BSA had the strongest influence on fouling. Mixing the different DOM fractions enhanced fouling. Combinations of the different organic molecules produced more fouling than would be predicted from the sum of each compound's fouling potential. The degree to which the organic molecules fouled the membranes was influenced by both the nature of the membrane materials and by their MWCOs. The fouling effect per millimole foulant was higher in the UF range, likely due to greater pore fouling. Results from the laboratory experiments and from the pilot plant at the SPMWD were not strictly comparable, but do indicate that the presence of a substantial deposit on the membrane surface does not necessarily account for an observed reduction in permeate flux.
Investigation of membrane filtration in a rotating disk geometry: Use of computational fluid dynamics and laboratory evaluation
(1997) Engler, James A., Jr; Wiesner, Mark R.
The feasibility, fluid dynamics and particle transport mechanics of rotary membrane filtration were investigated. The hypothesis tested was that, by rotating a disk membrane filter, a significant back-transport of suspended particles from the membrane could be accomplished due to centrifugal force and high shear rates. This hypothesis was tested by investigating in computational simulations and laboratory experiments the fluid dynamics of rotary membrane filtration, developing a better understanding of particle transport and fouling and evaluating the feasibility of treating feed streams with high solids loading. A commercial prototype rotary membrane disk filtration pilot and a laboratory pilot, which was designed and constructed as part of this research, were evaluated with respect to permeate flux performance as a function of feed solids concentration. The laboratory pilot was further evaluated to investigate particle transport and fouling behavior as a function of the operating parameters of rotation rate and transmembrane pressure drop. A high-fidelity computational fluids dynamics model of the laboratory pilot was developed. Results from simulations carried out with this model were used in concert with results from laboratory experiments to analyze particle transport and to draw general conclusions. Permeate flux in rotary membrane disk filtration was found to be very insensitive to particle loading in the feed stream. The correlation between rotation rate and permeate flux was very strong. Permeate flux performance was linked to high centrifugal force and radial drag near the membrane surface. A performance trade-off existed between the generation of high shear rates and centrifugal accelerations via high rotation rates and the radial distribution of the transmembrane pressure drop across the membrane. Permeate interior to the disk was under the influence of centrifugal force and therefore imparted a back pressure opposing filtration which increased with rotation rate.
Laminar fluid flow, particle transport and permeate flux behavior in crossflow membrane filters
(1996) Chellam, Shankararaman; Wiesner, Mark R.
Similarity solutions for axial and lateral velocity profiles, pressure gradients and wall skin friction are derived for the laminar, isothermal single phase flow of incompressible fluids in channels having porous boundaries. Results from a finite difference solution to the vorticity-stream function formulation of the Navier-Stokes equations are compared with previously reported perturbation, asymptotic, similarity and infinite series solutions. Initial transport of non-interacting particles suspended in laminar flow in the membrane far-field is reported to be accurately predicted by trajectory theory. RTDs obtained in response to pulse inputs in slow axial crossflows and high permeation rates appear to reveal a minimum in back-transport for 7 $\mu$m particles in the range of experimental conditions investigated here. Back-transport of smaller particles is due to Brownian diffusion whereas shear-induced diffusion appears to control the behavior of larger macrocolloids. The effects of suspension concentration, shear rate, Particle Size Distribution (PSD) and initial permeation rate on permeate flux are reported. Existing transient models based on shear-induced diffusion and particle adhesion as well as the steady state inertial lift model are found inadequate in predicting experimental observations of the specific permeate flux during the laminar crossflow filtration of narrow PSD suspensions. Under the range of experimental conditions investigated here, smaller particles deposit preferentially in the cake. Also, under identical experimental conditions higher permeate fluxes are obtained during the filtration of suspensions with a higher average particle size. Hence, pretreatment aimed at coagulating smaller particles could have a beneficial impact on permeate flux production. In all cases, specific resistances of cakes are higher in the crossflow mode compared to the dead-end mode. Also, cake specific resistances increased with shear and decreased with increasing permeation rate. Cumulative resistance to permeation is reported to increase on application of shear even without particle feed. Thus, even though cake mass decreases with increasing shear, it may not result in higher permeate flux. Therefore, pilot scale testing may still be necessary to evaluate the fouling potential of feed waters as well as in optimizing the operation of existing crossflow membrane filters.
Morphology of particle deposits
(2004) Tarabara, Volodymyr Valentinovich; Wiesner, Mark R.
The premise that the structure of particle deposits can be predicted based on the knowledge of particle hydrodynamics, solution chemistry and surface chemistry of particles is explored in the framework of three environmental application areas: membrane filtration, in situ capping of contaminated sediments, and environmental sensing. The role of deposit morphology in membrane filtration was evaluated in bench-scale filtration experiments. Results from experiments were compared with theoretical expectations based on a mathematical model for permeate flux for limiting cases of dominant membrane and filter cake resistances. Microscopic examination of membrane cake cross-sections revealed a stratified structure and underscored the importance of coupling between hydrodynamic conditions and interparticle interactions for the permeate flux performance. The influence of suspension heterogeneity on the membrane cake structure was investigated in simulations of particle deposition. Particle Peclet number and collision efficiency were related to trends in colloidal deposit morphology as a function of particle transport and surface chemistry. The simulations identified potential limitations in modeling filter cakes as homogeneous material when suspensions are composed of several chemically distinct particulate fractions. The relationship between sediment cap morphology and transport characteristics across the cap were explored. Bentonite-cement composite is proposed as a new material for in situ capping of contaminated underwater sediments. In addition to being mechanically stable, such composites provide for a possibility to control cap microstructure through the fine-tuning of postdepositional hydration processes in the cap. Cement content and liquid-to-solid fraction were identified as two dominant factors that determine overall cap performance. Microscopic studies of composite structure, strength testing as well as numerical and laboratory modeling of diffusion across composite caps were used to establish formation-structure-performance links for the composites. Finally, the impact of variable deposit morphology on the efficiency of surface-enhanced Raman substrates was investigated. Ionic strength mediated silver nanoparticle deposition was explored as a route for the morphological design of optically active substrates for water quality monitoring. The critical dependence of the effect of surface-enhanced Raman scattering on the morphology of enhancing substrate was quantified as a basis for developing sensors with tunable sensitivity. Fractal analysis was used to quantify deposit morphologies and to correlate these to enhancement factors afforded by the substrates.
Performance and cost modeling of low-pressure membrane filtration processes
(1994) Sethi, Sandeep; Wiesner, Mark R.
An integrated numerical model for examining the technical performance and estimating associated costs of low-pressure membrane filtration processes is presented. A model for removal of contaminants predicts permeate quality with respect to colloidal and organic material. A shear-induced diffusion model for estimating permeate flux is modified to also include Brownian diffusion as a particle transport mechanism. These two diffusion mechanisms lead to a minimum in permeate flux through a typical ultrafiltration membrane for particles in the size range of 0.1 $\mu$m in diameter. Lower shear rates are predicted to move this unfavorable size towards larger particle diameters. The effect of raw water quality and operating parameters on the performance and cost of typical ultrafiltration and microfiltration facilities is investigated. Particle size appears to be an important variable in determining both performance and cost. A product of this research is a software application package, MeMsys, developed for the PC-DOS environment.
Performance of nanostructured metal oxane derived ceramic membranes for fuel cell applications
(2007) Tsui, Eliza M.; Wiesner, Mark R.
An iron-based ceramic material is shown to be a practical candidate as an electrolyte material for proton exchange membrane in fuel cells. These membranes have comparable conductivity to the NafionRTM membrane with the advantages of lower permeability of methanol, less sensitivity to humidity, good chemical stability in fuel cell environment and lower material costs. Iron oxide nanoparticles (ferroxane) and aluminum oxide nanoparticles (alumoxane) were prepared as a pre-cursor materials for membrane fabrication. The structures of ferroxane and alumoxane derived ceramics were characterized with FTIR, SEM, TEM, and nitrogen adsorption-desorption. Protonic conductivity of the sintered membranes was studied by electrochemical impedance spectroscopy (EIS) to determine their feasibility in fuel cell applications. Ferroxane derived ceramics fired at 300°C has high proton conductivity and low dependence of humidity (ranging from 1.29 x 10-2 to 2.65 x 10-2 S·cm-1 at relative humidities of 33% to 100%). The values are comparable to, but on the low end of, the reported conductivities of Nafion. Aluminum-based ceramic material (alumoxane) has a lower conductivity at 2.23 x 10-4 to 3.83 x 10-4 S·cm -1 from 33% RH to 100% RH. The conductivity study as a function of operating temperature indicated the proton transfer for sintered ferroxane-derived membrane likely occurs via a Grotthus mechanism. The results of H2/air fuel cell indicated sintered ferroxane electrolyte could be operated at low temperature. The fuel cell exhibited steady performance with increasing power density over time. The sintered ferroxane-derived membrane with PVA sintered at 500°C has a power density of 5.21 mW·cm-2 and a current density of 16.5 mA·cm-2 measured at room temperature. The methanol permeabilities of sintered ferroxane and alumoxane derived ceramics were lower than that of Nafion and were 1.23 x 10-7 and 1.65 x 10-7 cm2·s-1 respectively. However, the open circuit voltage of ferroxane in DMFC was not improved in comparison to Nafion. Ferroxane-derived ceramic electrolyte sintered at 300°C in methanol/air fuel cell measured at 20°C had a power density of 7.7 muW·cm-2 with 2 M methanol solution. The power density increased to 30 muW·cm-2 with increasing methanol concentration to 18.5 M.
Photochemistry and environmental applications of water-soluble fullerene compounds
(2005) Pickering, Karen D.; Wiesner, Mark R.
The use of water-soluble fullerene-based compounds as sensitizers for reactive oxygen species (ROS) was investigated for the photodegradation of organic contaminants. A variety of conditions were evaluated to determine the production of ROS species by water soluble fullerene. Fullerol was an effective photosensitizer, particular under ultraviolet light. Fullerol produced a mixture of reactive oxygen species under both visible and ultraviolet irradiation. Evidence of both singlet oxygen and superoxide production was obtained. Water-soluble fullerene aggregates were not photocatalytic. Under dark conditions, fullerol appears to act as an antioxidant, while n-C60 had no antioxidant properties and under certain conditions may accelerate the production of ROS. Finally, it was demonstrated that membrane filtration can be used to separate the fullerene compounds from the process water. Nanofiltration membranes were used to remove fullerol from an aqueous solution. Fullerol rejection was approximately 98% and no fouling of the membrane was observed.

Browsing by Author "Wiesner, Mark R."

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