A Definition and Categorization System for Advanced Materials: The Foundation for Risk-Informed Environmental Health and Safety Testing.

Novel materials with unique or enhanced properties relative to conventional materials are being developed at an increasing rate. These materials are often referred to as advanced materials (AdMs) and they enable technological innovations that can benefit society. Despite their benefits, however, the unique characteristics of many AdMs, including many nanomaterials, are poorly understood and may pose environmental safety and occupational health (ESOH) risks that are not readily determined by traditional risk assessment methods.

The Technology Horizon for Photocatalytic Water Treatment: Sunrise or Sunset?

Advanced oxidation processes via semiconductor photocatalysis for water treatment have been the subject of extensive research over the past three decades, producing many scientific reports focused on elucidating mechanisms and enhancing kinetics for the treatment of contaminants in water. Many of these reports imply that the ultimate goal of the research is to apply photocatalysis in municipal water treatment operations. However, this ignores immense technology transfer problems, perpetuating a widening gap between academic advocation and industrial application.

Coupling Light Emitting Diodes with Photocatalyst-Coated Optical Fibers Improves Quantum Yield of Pollutant Oxidation.

A photocatalyst-coated optical fiber was coupled with a 318 nm ultraviolet-A light emitting diode, which activated the photocatalysts by interfacial photon-electron excitation while minimizing photonic energy losses due to conventional photocatalytic barriers. The light delivery mechanism was explored via modeling of evanescent wave energy produced upon total internal reflection and photon refraction into the TiO surface coating. This work explores aqueous phase LED-irradiated optical fibers for treating organic pollutants and for the first time proposes a dual-mechanistic approach to light delivery and photocatalytic performance.

Phosphate Changes Effect of Humic Acids on TiO Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

A major challenge for photocatalytic water purification with TiO is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated.

Inhibitory effect of natural organic matter or other background constituents on photocatalytic advanced oxidation processes: Mechanistic model development and validation.

The ability of reactive oxygen species (ROS) to interact with priority pollutants is crucial for efficient water treatment by photocatalytic advanced oxidation processes (AOPs). However, background compounds in water such as natural organic matter (NOM) can significantly hinder targeted reactions and removal efficiency. This inhibition can be complex, interfering with degradation in solution and at the photocatalyst surface as well as hindering illumination efficiency and ROS production.

Trading oxidation power for efficiency: differential inhibition of photo-generated hydroxyl radicals versus singlet oxygen.

The ability of reactive oxygen species (ROS) to interact with target pollutants is crucial for efficient water treatment using advanced oxidation processes (AOPs), and inhibition by natural organic matter (NOM) can significantly reduce degradation efficiency. We compare OH-based degradation (H2O2-UV) to (1)O2-based degradation (Rose Bengal) of several probe compounds (furfuryl alcohol, ranitidine, cimetidine) interacting in water containing background constituents likely to be found in treatment water such as natural organic matter (NOM) and phosphate, as well as in effluent from a waste-water treatment plant (WWTP). Hydroxyl radicals were much more susceptible to hindrance by all three background matrices (NOM, phosphate and WWTP effluent) tested, while (1)O2 was only slightly inhibited by NOM and not by phosphate or WWTP effluent.

Influence of carbon and metal oxide nanomaterials on aqueous concentrations of the munition constituents cyclotrimethylenetrinitramine (RDX) and tungsten.

There is an increasing likelihood of interactions between nanomaterials and munitions constituents in the environment resulting from the use of nanomaterials as additives to energetic formulations and potential contact in waste streams from production facilities and runoff from training ranges. The purpose of the present research was to determine the ability of nano-aluminum oxide (Al(2)O(3)) and multiwalled carbon nanotubes (MWCNTs) to adsorb the munitions constituents cyclotrimethylenetrinitramine (RDX) and tungsten (W) from aqueous solution as a first step in determining the long-term exposure, transport, and bioavailability implications of such interactions. The results indicate significant adsorption of RDX by MWCNTs and of W by nano-Al(2)O(3) (but not between W and MWCNT or RDX and nano-Al(2)O(3)).

Photocatalytic generation of multiple ROS types using low-temperature crystallized anodic TiO₂ nanotube arrays.

This study investigates the photocatalytic efficiency, type of reactive oxygen species (ROS) produced, and potential for structural and morphological modification of anodic TiO₂ nanotubes (NTs) synthesized using a novel, energy efficient, low temperature crystallization process. These TiO₂ NTs show greater photocatalytic efficiency than traditional high-temperature sintered NTs or supported Degussa P25 TiO₂, as measured by degradation of methyl orange, a model organic dye pollutant. EPR analysis shows that low-temperature crystallized TiO₂ NTs generate both hydroxyl radicals and singlet oxygen, while high-temperature sintered TiO₂ NTs generate primarily hydroxyl radicals but no singlet oxygen.

Photocatalytic pre-treatment with food-grade TiO(2) increases the bioavailability and bioremediation potential of weathered oil from the Deepwater Horizon oil spill in the Gulf of Mexico.

Using the 2010 Deepwater Horizon oil spill in the Gulf of Mexico as an impetus, we explored the potential for TiO(2)-mediated photocatalytic reactive oxygen species (ROS) generation to increase the bioavailability (solubility) and biodegradability of weathered oil after a spill. Food grade TiO(2), which is FDA approved for use as food additive in the United States, was tested as a photocatalyst for this novel application. Photocatalytic pre-treatment (0.

Nanotechnology for a safe and sustainable water supply: enabling integrated water treatment and reuse.

Ensuring reliable access to clean and affordable water is one of the greatest global challenges of this century. As the world's population increases, water pollution becomes more complex and difficult to remove, and global climate change threatens to exacerbate water scarcity in many areas, the magnitude of this challenge is rapidly increasing. Wastewater reuse is becoming a common necessity, even as a source of potable water, but our separate wastewater collection and water supply systems are not designed to accommodate this pressing need.