David G. Cahill University of Illinois, Urbana-Champaign
Viatcheslav (Slava) Freger Ben Gurion University of the Negev
Anthony G. Sommese Nalco Company
Q4: Ion Exchange and Adsorption
Wednesday AM, April 15, 2009
Room 2020 (Moscone West)
9:30 AM - **Q4.1
New Ion Exchange Resins for the Remediation of Water: Arsenate, Perchlorate, Uranyl and Beyond
Spiro Alexandratos 1 Show Abstract
1 Dept of Chemistry, Hunter College of the City University of New York, New York, New York, United States
The remediation of water in the environment and the treatment of wastewater continues to be one of the most challenging problems facing societies around the world. Ion exchange resins offer an important avenue for water treatment processes because of their long-term stability and adaptability to column operations. When properly designed, they are also selective and achieve high loading capacities at rapid rates of throughput.Our research has focused on the design of new ligands for ion-selective separations. The ligands are immobilized onto crosslinked polystyrene beads with a diameter of 250 - 420 mm. The polystyrene is then modified with ligands whose binding characteristics are complementary to the requirements of the ion being targeted for separation from aqueous media.Immobilization of N-methyl-D-glucamine onto polystyrene gave a resin that was selective for arsenate at a pH of 3.5 - 6.5. The resin is regenerable with a mild base solution. Selectivity requires a flexible matrix and that the amine site is protonated.The polarizable perchlorate ion has a high affinity for the trihexylammonium ligand. That resin has a very slow rate of loading and requires the binding of a second ligand to the polymer support in order to enhance the kinetics of complexation. That ligand must be relatively hydrophilic and the triethylammonium ligand seems to be most appropriate for this purpose. Given their similar chemistry, the same resin also has a high affinity for the pertechnetate ion that contaminates the groundwater in certain parts of the United States.Recent research has shown that the phosphate ligand has a high affinity for metal cations when immobilized on a polyol scaffold bound to the polystyrene beads. One such scaffold is pentaerythritol. Aminoalcohols have an even greater potential as scaffolds for the preparation of resins with a high affinity for ions such as uranyl. The latest results will be presented.Acknowledgements: The arsenate resin was developed in collaboration with Dr Rich Salinaro, formerly of the Pall Corporation, and funded by the New York State Energy Research and Development Authority and the Pall Corporation. All other research was funded by the Department of Energy, Office of Basic Energy Sciences. The perchlorate / pertechnetate resin was developed in collaboration with Dr Bruce Moyer and his group at the Oak Ridge National Laboratory. The experimental work on the arsenate resin was completed by post-doctoral associate Dr Laurent Dambies; the work on the polyol resins was completed by post-doctoral associate Dr Xiaoping Zhu.
10:00 AM - **Q4.2
Novel Media for Removing Toxic Species from Water to Parts per Trillion Levels.
David Graham 1 , Douglas Adamson 1 , Ward Collins 1 , Robert Mininni 1 Show Abstract
1 , Captur Technologies.Co., LLC, Long Valley, New Jersey, United States
The capture and removal of toxic metals from waste water to the limits of parts per million is currently not an easy process, thereby driving many companies to seek variance permits from local authorities. Such variance permits are the last resort for many as they seek to meet the ever tightening environmental discharge specifications to protect our environment, including many rivers and lakes. This presentation will describe the development and use of a novel medium that will capture a wide range of toxic species and allow them to be removed from a broad spectrum of water streams, to meet the hitherto difficult to attain environmental limits of part per trillion.The medium consists of a polymer that is chemically grafted and crosslinked onto a solid substrate creating an open gel structure. This swollen gel with its high concentration of charges will capture many charged toxic species. By reversing the polymer charges we can release the captured toxic species for disposal by environmentally safe methods. Initially, the medium has been used to treat water streams in a packed bed column, thereby allowing the use of packed bed cartridges. This allows their use in modular designs to meet expanding and contracting water processing streams. The engineering designs are those currently employed as standard fluid process operations and require no new technologies.The emphasis for this new medium has been with toxic metals such as copper, mercury and radium236 and all have been removed to the levels of sub and single digit parts per trillion as measured by independent EPA approved Analytical Laboratories. As well as removing these toxic species, we have shown that others metals, such as lead, iron, silver and gold could be handled in a similar fashion. In addition, we have been able to remove a wide range of organic dyes from dye processing waste water streams. An added benefit of this novel medium is that other organic molecules including humates, dioxin and organic acids can be captured and removed. An engineering process is currently under development for these applications.
10:30 AM - **Q4.3
Iron Oxide Nanostructured Materials in Water Treatment.
Maria Fidalgo de Cortalezzi 1 , Paola Sabbatini 1 , Laura De Angelis 1 Show Abstract
1 Chemical Engineering, Buenos Aires Institute of Technology, Buenos Aires Argentina
Iron oxides are low cost and well studied materials that have been applied extensively in traditional water treatment processes such as coagulation.The availability of these materials in the nanoscale has made them interesting for a wider array of uses in the environmental field, such as sorbents for drinking water treatment, catalyst in waste and ground water remediation and membrane materials to list a few. In recent years, our work has focused on the investigation of iron oxide nanoparticles as base materials for the fabrication of new devices and processes for drinking water treatment.Iron oxide nanoparticles were used as precursor for high specific surface area ceramics. Their adsorption properties regarding arsenic and other heavy metals were studied in a variety of conditions and water matrixes, and the material characterized extensively through SEMs, XRDs, XAS and nitrogen adsorption isotherms. Based on that information, we developed a low cost arsenic adsorbent device tailored for application in rural and remote areas with minimum requirements. A membrane-adsorbent reactor was also designed to more efficiently use the material for applications high water demand such as municipalities. Water samples from naturally arsenic contaminated groundwater in the Buenos Aires province in Argentina was used to perform field tests of the systems. The study showed that the good performance observed in artificial arsenic solutions was kept for the natural samples and allowed for a preliminary cost assessment of the technology, which is usually a determining factor in arsenic abatement processes. The technology is inexpensive and easy to use, though some areas for improvement were identified to work with in the scale up process. The iron oxide ceramics were also investigated as ultrafiltration membranes. Retention and fouling potential of different organic macromolecules was measured. The work on this area has focus on the evaluation of new cleaning methods for the ceramics, through degradation of the adsorb foulants by Fenton type reactions. Cleaning of the fouled membrane with Fenton reagent recovered 100% of the initial membrane permeability, with no detectable membrane material loss.
11:30 AM - **Q4.4
Desalination and pH control using Resin-Wafer Electrodeionization.
Yupo Lin 1 , Seth Snyder 1 Show Abstract
1 Energy System Division, Argonne National Laboratory, Argonne, Illinois, United States
Many processes for removing ions from aqueous solutions are strongly dependent on the solution pH. pH adjustments are a common industrial water treatment step. Electrodeionization, a platform that incorporates a mixed bed of ion exchange resins in an Electrodialysis (ED) system can influence localized solution pH with water splitting. Argonne developed a novel ion-exchange resin wafer EDI (RW-EDI) platform that provides in-situ pH control to enhance ion removal efficiency. The localized pH manipulation enables RW-EDI to handle separations that conventional ED cannot achieve. RW-EDI offers significant advantages in removing ions at low concentrations and minimizing power consumption. In this presentation, we will introduce Argonne’s RW-EDI device, its operation and performance in removing alkalinity, hardness, and organic acids. A case study of RW-EDI for impaired water purification will be discussed.
12:00 PM - Q4.5
Rapid, Selective, Removal of Perchlorate from Water Using Ion-Exchange Fibers.
James Langer 1 , James Economy 1 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Perchlorate is an anionic contaminant found in many groundwater supplies throughout the United States, especially in areas near Air Force bases and rocket-manufacturing facilities. Due to physicochemical properties similar to iodide, perchlorate inhibits uptake of iodide into the human thyroid. As a result, the US EPA has issued a guidance indicating a reference level of approximately 25 ppb perchlorate in drinking water. Many states have established or are considering regulatory limits as low as 1 ppb. For this reason it is important to develop methods for removal of perchlorate to safe levels in drinking water.Conventional ion-exchange processes using ion-exchange beads are commonly used to treat perchlorate-contaminated water. While these technologies are pervasive they are at the same time flawed by problems such as slow exchange kinetics and poor selectivity for perchlorate. The former problem leads to undesirable leakage of perchlorate in column effluent (requiring either the use of very low throughputs and/or very large columns) while the latter leads to very low capacity for perchlorate, which is typically present in much smaller concentrations than competing anions such as sulfate, chloride, bicarbonate, and nitrate. In order to achieve high selectivity for perchlorate, it is desirable to use ion-exchange resins with hydrophobic exchange sites, such as quaternary ammonium salts derived from tributylamine or trihexylamine. Use of such functional groups leads to slow diffusion in the resin, resulting in poor exchange kinetics. As an engineered form, ion-exchange fibers provide an alternative solution for selective removal of perchlorate, allowing rapid exchange kinetics in concert with high selectivity, in addition to ease of use in column purifications. We report the preparation and properties of ion-exchange fibers based on non-woven glass substrates coated with poly(vinyl benzyl chloride), cross-linked with 1,4-diazabicyclo[2.2.2]octane (DABCO), and treated with various tertiary amines. These composite fibers display an order of magnitude increase in ion-exchange kinetics as compared to the Purolite A-530E perchlorate-selective resin. We propose this new class of ion-exchange materials as an excellent treatment option for both municipal and, more importantly, point-of-use applications.
12:15 PM - Q4.6
Carboxylate Rich Carbonaceous Adsorbents via One Step Hydrothermal Carbonization for Water Purification.
Titirici Magdalena 1 , Demir-Cakan Rezan 1 , Markus Antonietti 1 Show Abstract
1 Colloid Chemistry, Max-Planck Institute for Colloids and Interfaces, Potsdam Germany
Water pollution caused by heavy metals is a serious world wide environmental problem with a significant impact on human health and environment. Chromium, nickel, cadmium, and lead are classified as heavy metals and are commonly associated with water pollution. Among them, cadmium and lead are the most toxic elements to human being and are often present at high concentration in liquid industrial waste. The present study concerns the one step aqueous route production of carbonaceous materials loaded with carboxylic groups using hydrothermal carbonization of glucose in the presence of small amounts of acrylic acid. This method provides a “green” solvent and surfactant free access to hydrophilic functionalized carbons with very good water dispersivity. Thus, organic monomers can be partially replaced by the controlled dehydration products of carbohydrates, which can be then copolymerised or can undergo cycloaddition reaction with functional co-monomers to give a new type of hybrid between carbon and polymer latex. These latexes consist mainly of renewable raw materials, having a low cost base and expanding heterophase polymerization processes to carbonaceous materials. This method offers a general platform for the production of carbonaceous materials with different functionality provided by the availability of water soluble functional organic monomers. The final products consist mainly of an amorphous carbon framework with its high thermal and chemical stability, however with increased functionality brought in by the organic monomer. By solid state NMR and other analytical techniques, it was proven that the acrylic acid is not added in a polymerization type process, but presumably undergoes cycloaddition to a more conjugated and therefore more effective binding site.The synthesized materials proved to be feasible for use in adsorption experiments for removal of heavy metals from aqueous solutions. The adsorption capacity was as high as 351.4 mg/g for Pb(II) and 88.8 mg/g for Cd(II), which is well beyond ordinary sorption capacities and proving the efficiency of the materials to bind and buffer ions, or more specifically to remove heavy metal pollutants. The possibility of water purification archived with carbonaceous materials produced under mild conditions and with an overall low cost base is definitely an attractive alternative.
12:30 PM - Q4.7
Molecular Imprinted Polymers by Miniemulsion Polymerization for Selective Hospital Waste Water Treatment.
Achim Weber 1 , Klaus Niedergall 2 , Tino Schreiber 2 , Juergen Riegler 2 , Dieter Bryniok 1 , Thomas Hirth 1 2 , Guenter Tovar 1 2 Show Abstract
1 , Fraunhofer Institute for Interfacial Engineering and Biotechnology, Stuttgart Germany, 2 , Institute for Interfacial Engineering, University Stuttgart , Stuttgart Germany
Molecular recognition capabilities are evoked at artificial materials by the NANOCYTES™-technology of the Fraunhofer IGB. The biomimetic nanoparticles described here, possess such molecularly recognizing properties. For this purpose they carry molecularly defined binding sites at their surface. Molecularly imprinted nanospheres (NanoMIPs) were developed for the specific adsorption of micropollutants from hospital waste water. Active pharmaceutical substances and their meta-bolite which cannot decompose in waste water treatment plants were chosen as model compounds (Carbamazepine, Oxcarbazepine, Diclofenace and Pentoxifylline). Molecularly imprinted nanospheres (nanoMIPs) are prepared by a miniemulsion polymerization technique, where the monomer, the template, the cross-linker, and the initiator are reacted in the droplet cavities of an emulsion. The reaction, although complex, runs in a single reaction chamber and in a single step chemical process. The molecularly imprinted nanospheres are synthesized by the classic mini-emulsion polymerization and inverse miniemulsion polymerization. In both polymer systems we use p(methacrylicacid-co-ethylenglycoldimetharylate) and p(acrylamide-co-N,N'-ethylene-bis-acrylamide) as polymer system. The described technique of mini-emulsion polymerization results in particles with typical sizes between 50 and 300 nm. Besides classic mini-emulsion polymerization (hydrophobic phase emulsified in hydrophilic phase – here water), a MIP technique also based on inverse mini-emulsion polymerization is established. Thus, possible templates can be chosen from the full range of hydrophilic over amphiphilic to hydrophobic molecules. Additives like inorganic nanocrystals or organic fluorophores can be added to polymerization process. Thus nano-hybridmaterials with multiple properties (fluorescence, magnetism) and especially specific binding sites are easily designed as valuable material in modern bio-analytics and diagnostics as well as in down stream processing in chemical and pharmaceutical industry. A magnetic core will facilitate the separability of the nanoparticles from waste water. It could be shown that magnetite could be incorporated into the polymer system p(methacrylicacid-co-ethylenglycoldimetharylate) and it could be shown that the templates Carbamazepine, Oxcarbazepine, Diclofenace and Pentoxifylline do not effect the polymerization process. The first performed adsorption experiments showed that the molecularly imprinted polymers adsorb more Pentoxifyllin and Diclofenac compared to the non-imprinted polymers. Furthermore experiments to produce imprinted polymer nanoparticles with a magnetisable core are shown.
12:45 PM - Q4.8
Chemically Stable Magnetic Chelating Agents – Attaching Metal Chelators to Nanomagnets for Water Purification, Heavy Metal and Noble Metal Recovery.
Michael Rossier 1 , Fabian Koehler 1 , Evagelos Athanassiou 1 , Robert Grass 1 , Wendelin Stark 1 Show Abstract
1 Chemistry and Applied Biosciences, ETH Zurich, Zurich Switzerland
Magnetic particles are routinely applied in biochemistry separations. Unfortunately their application is often limited due to high costs, poor stability and low binding capacities. Recently we prepared graphene-like coated metallic nanoparticles by reducing flame spray synthesis [1,2]. The coating on the one hand protects the metal nanoparticles from oxidation below 190°C and dissolution in concentrated acids. On the other hand it allows the introduction of covalently bound functional groups via diazonium chemistry  or physical adsorption offering the freedom of organic chemistry on the particle surface.The functionalized magnetic particles represent a promising modular platform for removing a wide range of contaminants. Attaching EDTA-like chelating agents to the surface allows the removal of heavy metal ions from aqueous solutions. Furthermore, attaching a thiourea-like chelating agent allows the efficient removal of precious metal ions in highly acidic solutions. The low costs and particle stability favor this preparation method and material for large-scale separation application of metal ions in ultra low concentrations.R. N. Grass, W. J. Stark, J. Mater. Chem. 2006, 16, 1825. R. N. Grass, M. Dietiker, R. Spolenak, W. J. Stark, Nanotechnology 2007, 18, 035703.R. N. Grass, E. K. Athanassiou, W. J. Stark, Angewandte Chemie 2007, 26, 4909
Q5/S4: Joint Session: Environmental Applications of Photocatalytic Materials and Systems
Wednesday PM, April 15, 2009
Room 2016 (Moscone West)
2:30 PM - Q5.1/S4.1
Polymer-Titania Composites for Photocatalysis of Organics in Aqueous Environments.
Cecil Coutinho 1 , Vinay Gupta 1 Show Abstract
1 Chemical and Biomedical Engineering, University of South Florida, Tampa, Florida, United States
Novel composites were prepared that were composed of titania (TiO2) nanoparticles embedded within cross-linked microgels of poly(N-isopropylacrylamide). Interpenetrating linear chains of poly(acrylic acid) were used to functionalize the nanoparticles of TiO2 for dispersal within the porous framework of the stimuli responsive microgels. The composite particles showed rapid sedimentation, which is useful for gravity separation of these particles in applications such as environmental remediation via photocatalytic degradation. Methyl orange was employed as a model contaminant to investigate the degradation kinetics using these composites in aqueous suspensions. Kinetics of the photodegradation was evaluated by monitoring the decline in the methyl orange concentration using UV-Vis spectroscopy. Degradation of methyl orange using freely suspended titania (DegussaTM P25) was also conducted for comparison with the composites. In this presentation, the effects stemming from different loading of TiO2 and the pH of the solution will be discussed. These variables influence the interplay between the ionization of the poly(acrylic acid) and methyl orange, the surface charge of the titania, and adsorption of the methyl orange all of which determines the degradation kinetics.
2:45 PM - **Q5.2/S4.2
Photocatalytic Processes in Water Purification and in Environmental Systems Mediated by Dissolved Iron and Iron Containing Solid Phases.
Stephan Hug 1 Show Abstract
1 Water Resources and Drinking Water, Eawag , CH-8600 Duebendorf, Zurich, Switzerland
Photocatalytic processes in water purification and in the environment, mediated by dissolved iron and iron containing solid phasesPhotoinduced transformations involving naturally occurring metal ions and solid phases are of crucial importance for metal and nutrient cycling in the aquatic environment. The photoreactive properties of transition metal (hydr)oxides and of dissolved transition metals can be applied for water purification. In addition to synthetic nanoparticles such as TiO2, synthetic and natural iron(hydr)oxides have received considerable attention, in part due their extended absorption bands into the visible range of the solar spectrum. The application of naturally occurring and synthetic iron(hydr)oxides is promising for the development of inexpensive solar water treatment units, for example in developing countries. In contrast to TiO2 and other synthetic photocatalytic materials designed for optimal stability, iron(hydr)oxides can undergo photoreductive dissolution. Phototoinduced ligand to metal charge transfer leads to formation of Fe(II) and of oxidized radical species and can start efficient cycling between dissolved and newly precipitated iron phases and the generation of reactive oxygen species in aerated water. The reaction pathways are highly dependent on pH and the presence of organic and inorganic ligands. H2O2, generated by reduction of dissolved O2, reacts with Fe(II) to highly reactive OH-radicals at low pH, but leads to more selectively oxidizing species (possibly Fe(IV) species) at neutral pH. UV-A illumination of aerated waters containing dissolved iron and/or suspended iron colloids can lead to reductive as well as to oxidative transformation of pollutants. We will show reaction pathways and kinetic models for the photoinduced reduction and removal of Cr(VI) and the oxidation and removal of As(III). The photo-efficiency of these and similar systems can be greatly increased by organic ligands which form complexes with dissolved Fe(III) and with Fe(III) surface sites. We investigate reaction pathways by measuring reactive intermediates in solution and by probing reactions and structures of surface adsorbed species by application of in-situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). Inner-sphere complexation of organic ligands on the surface of iron(hydr)oxides appears to be an important factor for the efficient transformation of adsorbed compounds and for the generation of reactive oxygen species. In contrast, most organic ligands are indiscriminately and completely oxidized and degraded on the surface of rutile and anatase particles under UV-A irradiation. By assessing and comparing structures and reactivities of adsorbed species on different surfaces by spectroscopic tools and with kinetic modeling of the reaction pathways on the surface and in solution, a better molecular level understanding of reactions in heterogeneous systems can be developed. Two important aims of our current investigations are a better understanding of the relevant processes in natural and engineered systems and the development of low cost solar treatment units for the purification of contaminated water.
3:15 PM - Q5.3/S4.3
Enhanced Photocatalytic Efficiency and Catalytic Memory from PdO Nanoparticles on Nitrogen–doped Titanium Oxide
Qi Li 1 2 , Yin Li 1 2 , Rongcai Xie 1 2 , Jian Shang 1 2 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 The Center of Advanced Materials for the Purification of Water with Systems, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Visible light photocatalysts enable a greater portion of the solar spectrum or just indoor light to be used to provide photocatalytic capability for environmental application. However, anion-doping brings intrinsically the serious problem of massive charge carrier recombination, largely limiting the photoactivity of anion-doped TiO2 under visible light illumination. Another inherent problem of the current anion-doped TiO2 photocatalysts is that they lose their photocatalytic capability in the dark environment, where they could not produce electron and hole pairs. In this research, a palladium modification of nitrogen-doped n-TiO2 was introduced, hereafter referred to as TiON/PdO, which has demonstrated not only a much faster photocatalytic disinfection rate on Escherichia coli (E. coli) under visible light illumination than nitrogen-doped titanium oxide (TiON), but also a memory catalytic disinfection capability after visible light illumination is turned off for extended periods. These unusual antimicrobial properties of TiON/PdO are derived from the optoelectronic coupling between PdO nanoparticles and TiON semiconductor, which promotes the charge carrier separation in TiON and results in the chemical reduction of Pd(2+) to Pd(0). While the separation of the charge carriers greatly enhances the visible light photocatalytic killing of E. coli, a memory antimicrobial effect results from the catalytic effect of Pd(0). The strong antimicrobial effects of TiON/PdO photocatalyst under visible light illumination and their post-illumination activity open up new possibilities, such as continuous solar-powered disinfection during daytime and at night, for a broad range of environmental applications.
3:30 PM - Q5.4/S4.4
Photocatalytic Materials for Water Disinfection
Qi Li 1 2 , Pinggui Wu 1 2 , Rongcai Xie 1 2 , Jian Shang 1 2 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 The Center of Advanced Materials for the Purification of Water with Systems, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Despite much progress, microbials in water still pose a great threat to individual health. The conventional water-disinfection technique, chlorination, has been practiced for over 100 years owing to its good effectiveness against bacteria and viruses, low cost and low maintenance. However, chlorination is now known to produce potentially toxic and carcinogenic disinfection by-products (DBPs). To search for a viable alternative disinfection approach, new antimicrobial materials have been developed which rely on visible light photocatalysis to inactivate microbial species. Both chemical and physical approaches have been pursued in design of oxide semiconductor photocatalysts, to promote visible light absorption, to reduce charge recombination, to create catalytic memory, to increase the microbial contact efficiency and to control microbial absorption. Mechanisms of microbial inactivation have been elucidated by atomic force microscopy, scanning and electron microscopy, fluorescence microscopy, and cell culture analysis. While virus activated is primarily controlled by the electrostatic force between the semiconductor surface and the virus, bacterial killing is realized by oxidative damages on the cell membrane in forms of membrane thinning and perforations.
4:15 PM - **Q5.5/S4.5
TiO2 Solar Photo-assisted Bacterial Inactivation in Water: Influence of Physicochemical, Biological and Engineering Parameters.
Cesar Pulgarin 1 Show Abstract
1 , Ecole Polytechnique Federale de Lausanne, Lausanne Switzerland
In sunny regions, helio-photocatalysis by TiO2 has been considered as a possible new approach for disinfection of small volumes (1 to 100 litres) of water. It is generally accepted that, in presence of TiO2, the inactivation of microorganisms is essentially due to oxidative radicals (mainly OH) produced on TiO2 through irradiation by UV part of solar light. In fact, oxidative radicals attack the bacterial cell membrane leading to the perturbation of different cellular processes and finally to bacterial death.In this presentation, experiments on disinfection of synthetic and real contaminated waters in different photo-reactors and illumination systems are described. Among other experiments, disinfection of natural E. coli K 12 contaminated water was carried out under direct solar radiation using a 35 L compound parabolic collector (CPC). Under these conditions, total disinfection was reached in 4 h and bacterial recovery was not observed during subsequent 24 hours of dark. Latter results show that efficiency of photocatalytic inactivation depends on biological characteristics of bacteria, chemical composition of treated water, type of illumination and engineering parameters. Limitations, advantages and drawbacks of photocatalytic disinfection are pointed out. Sensitivity of bacteria to TiO2 solar photoassisted treatment varies for each species of microorganism according to strain, stage of culture, growth medium and initial bacterial load. Physico-chemical parameters, for example intensity and intermittency of radiance, also influence the process. Further, the presence of natural anions such as HPO4-2, HCO3-, NO3- and Cl-, can affect the bacterial inactivation rate. The use of suspended TiO2 for solar disinfection requires a subsequent settling-filtration process whereas typical supported TiO2 shows considerably lower disinfection rate compared to suspended TiO2. In consequence, to improve disinfection efficiency of supported TiO2, the titanium oxide was immobilized together with iron oxides on a functionalized polymer film. The chemical composition of surface and its properties changes were measured at each step of preparation by SEM, XPS and UV-vis analysis. It was observed that the simultaneous action of immobilized photo-Fenton reaction and supported TiO2 photocatalysis considerably enhances E. coli disinfection rate. For this synergistic effect, a possible mechanism has been proposed. Finally, as TiO2 takes advantage of only 4% of the solar radiation, N, S co-doped TiO2 powder absorbing visible light was prepared. Under visible light, phenol and dichloroacetic acid (DCA) are not degraded whereas E. coli is inactivated. Under whole solar spectrum N, S co-doped TiO2 is not more active than the not doped material. In this case as well, a mechanistic explanation is also suggested.
5:00 PM - Q5.7/S4.7
Micron-scale Sensors for Spatiotemporal Study of Water Photodecontamination.
Alexander Scheeline 1 , Rebekah Wilson 1 Show Abstract
1 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Photocatalytic oxidation of water contaminants may proceed in at least two ways: adsorption and activation of contaminants on photocatalysts (followed by reaction with dissolved oxygen after desorption) or by homogeneous oxidation by reactive oxygen species generated by the photocatalyst. Distinguishing these two mechanisms is feasible if one can spatially measure concentration of H2O2 and superoxide radical in thin aqueous layers near the catalysts. We report development of ~ 200 μm wide 3 electrode amperometric microsensors and characterize their response to the species of interest and interferents.
5:15 PM - Q5.8/S4.8
TiO2 Anatase Nanotubes for the Photocatalytic Purification of Uranium and Arsenic Containing Water.
Marco Bonato 1 , Vala Ragnarsdottir 2 3 , Geoffrey Allen 1 Show Abstract
1 Interface Analysis Centre, University of Bristol, Bristol, Bristol, United Kingdom, 2 Department of Earth Sciences, University of Bristol, Bristol, Bristol, United Kingdom, 3 School of Engineering and Natural Sciences, University of Iceland, Reykjavik Iceland
IntroductionTitanium dioxide is one of the most important photocatalytic materials for ground water purification and heterogeneous photocatalysis using UV light. Surface reactivity makes it an excellent adsorbent material for the potential uptake of inorganic pollutants such as uranium, lead and arsenic from ground waters. In the case of arsenic(III), it is possible to couple the adsorbent capability of titania with its photocatalytic properties. As(III) is easily adsorbed and oxidised to As(V), less noxious than the trivalent ion and easier to eliminate using coagulation methods. In this communication we report a study of the adsorbtion of the metals uranium and arsenic on TiO2 using X-ray photoelectron spectroscopy. The amount of metal adsorbed has been quantified by measurements of surface coverage expressed in atomic percent. TiO2 anatase nanotubes have recently been given special scientific attention for their increased surface area, enhanced photocatalytic effect and simplicity of synthesis.ExperimentsNanotubes used in the current experimental work were synthesised via anodic oxidation of titanium in a fluorine ion solution. A titanium foil (1x1 mm) was mechanically polished with silicon carbide paper (up to 4000 grade, ~2 μm). Preparation of the anatase nanotubes on the titanium metal surface was achieved by anodic oxidation at room temperature (21 ○C), carried out for 20 min at a constant 20 V, in 0.5 wt% HF aqueous solution with a platinum counter electrode. High spatial resolution images of the sample surface were recorded using focussed ion beam (FIB) stimulated secondary electron microscopy. The samples were then annealed at 320 ○C for 5 h to induce transformation of the amorphous nanotubes into the desired anatase form as confirmed by Raman spectroscopy. ResultsThe role of the TiO2 nanotubes as an efficient adsorbent for the uptake of the uranyl ion (UO2)2+ from water was investigated. Batch adsorption carried out in both air and in anoxic (N2) atmospheres showed a higher uptake when the experiments were performed in the latter N2 atmosphere and at alkaline pH (higher that 8). Experiments in the pH range 5-8 and in the presence of O2 and CO2 favoured the formation of uranyl carbonate complexes that were easily extracted from the solution. Analysis of TiO2 surfaces exposed to uranyl solutions was performed using X-ray photoelectron spectroscopy. TiO2 anatase nanotubes were also investigated as a potential photocatalyst for the oxidative removal of arsenite (As(III)-AsO33-) from water. The oxidation of As(III) to As(V) was promoted by the irradiation of TiO2 with UV light in oxygen atmospheres. The reaction was studied in the pH range 3-9. XPS analysis of the surface of the TiO2 photocatalyst revealed the percentage of the adsorbed As(III) oxidised to arsenate (As(V)-AsO43-). The amount of arsenic adsorbed from the solution was quantified by recording high resolution XPS spectra in the As3d photoelectron region.
5:30 PM - Q5.9/S4.9
Adsorption and Degradation of Progesterone onto Muscovite Mica.
Bernadette Goritschnig 1 2 , Keith Hallam 1 , Terence McMaster 2 , Vala Ragnarsdottir 3 4 Show Abstract
1 Interface Analysis Centre, University of Bristol, Bristol United Kingdom, 2 Department of Physics, University of Bristol, Bristol United Kingdom, 3 Department of Earth Sciences, University of Bristol, Bristol United Kingdom, 4 Faculty of Engineering and Natural Sciences, University of Iceland, Reykjavik Iceland
In recent years, Endocrine Disrupting Chemicals (EDCs) have become a major focus in environmental chemistry, marine biochemistry and medicine. These substances derive from various industrial products, e.g. in agriculture, and pharmaceuticals and residues are not completely eliminated in the human body. They are often excreted only slightly transformed or even unchanged, and are detected in sewage and surface water samples at concerning levels. Compounding the problem is that they are not easily removed by water treatment. EDCs interfere with hormone action, block natural hormones from working or mimic them and are implicated in harmful biological trends, e.g. feminisation of fish, decreasing sperm counts in humans and cancer of the reproductive organs. For these hormonally active compounds, conventional removal methods are questionable because very little is known about the ultimate degradation products.Progesterone is the most important and only naturally occurring hormone of the progestagens. It is secreted by the female reproductive system, is responsible for ovulation, prepares the uterus for the foetus and maintains pregnancy.The aim of this work is to investigate whether mineral surfaces can catalyse hormone decomposition under UV light. We are studying the interface between an aquatic pollutant, progesterone, and a mineral surface, via the adsorption kinetics and characteristics of the hormone and its reaction under UV light. In contrast to earlier progesterone studies, including chlorination and ozonolysis, this work is at the nanoscale and single molecule level.An Atomic Force Microscopy (AFM) liquid cell has been used, allowing surface-adsorbed molecules to be imaged and/or manipulated in situ in physiological buffer solutions. This also allows dynamic biological processes to be imaged at the water-mineral interface as the imaging environment is altered by, for example, the addition of chemicals to the buffer solution. By imaging the surface in water, subsequently injecting a solution containing the hormone and the addition of a divalent cation the adsorption process can be followed from time zero. Hormone adsorption onto Au- and Cu-coated mica and glass was also studied with in situ stress measurements based on a cantilever bending method and the Quartz Crystal Microbalance (QCM). For degradation experiments in air, a 254 nm wavelength UV lamp was used to initiate changes on the progesterone covered mineral surface. Exposure was either constant, during scanning, or intermittent, between successive scans. Significant structural changes of the hormone on the mineral have been observed. For UV degradation of progesterone in liquid optical fibres from a deuterium light source are applied in situ onto a very constrained area of the sample.The main results from experiments performed in liquid and in air show that adsorption and degradation can be imaged in situ and in real time which provides a significant basis for further research.