The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO2 for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997–3027, 2010) and of modelling of TiO2 action have recently been published (Dalrymple et al. , Appl Catal B 98(1–2):27–38, 2010). In this review, we give an overview of the effects of photoactivated TiO2 on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO2 catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.

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Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity

Nanotechnology, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for treatment of surface water, groundwater, and wastewater contaminated by toxic metal ions, organic and inorganic solutes, and microorganisms. Due to their unique activity toward recalcitrant contaminants and application flexibility, many nanomaterials are under active research and development. Accordingly, literature about current research on different nanomaterials (nanostructured catalytic membranes, nanosorbents, nanocatalysts, and bioactive nanoparticles) and their application in water treatment, purification and disinfection is reviewed in this article. Moreover, knowledge regarding toxicological effects of engineered nanomaterials on humans and the environment is presented.

Nanotechnology and Water Treatment: Applications and Emerging Opportunities

The rapidly increasing population, depleting water resources, and climate change resulting in prolonged droughts and floods have rendered drinking water a competitive resource in many parts of the world. The development of cost-effective and stable materials and methods for providing the fresh water in adequate amounts is the need of the water industry. Traditional water/wastewater treatment technologies remain ineffective for providing adequate safe water due to increasing demand of water coupled with stringent health guidelines and emerging contaminants. Nanotechnology-based multifunctional and highly efficient processes are providing affordable solutions to water/wastewater treatments that do not rely on large infrastructures or centralized systems. The aim of the present study is to review the possible applications of the nanoparticles/fibers for the removal of pollutants from water/wastewater. The paper will briefly overview the availability and practice of different nanomaterials (particles or fibers) for removal of viruses, inorganic solutes, heavy metals, metal ions, complex organic compounds, natural organic matter, nitrate, and other pollutants present in surface water, ground water, and/or industrial water. Finally, recommendations are made based on the current practices of nanotechnology applications in water industry for a stand-alone water purification unit for removing all types of contaminants from wastewater.

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A Review of Removal of Pollutants from Water/Wastewater Using Different Types of Nanomaterials

We have shown that pulmonary exposure to fine particulate matter (PM) impairs endothelium dependent dilation in systemic arterioles. Ultrafine PM has been suggested to be inherently more toxic by virtue of its increased surface area. The purpose of this study was to determine if ultrafine PM (or nanoparticle) inhalation produces greater microvascular dysfunction than fine PM. Rats were exposed to fine or ultrafine TiO2 aerosols (primary particle diameters of ~1 μm and ~21 nm, respectively) at concentrations which do not alter bronchoalveolar lavage markers of pulmonary inflammation or lung damage. By histopathologic evaluation, no significant inflammatory changes were seen in the lung. However, particle-containing macrophages were frequently seen in intimate contact with the alveolar wall. The spinotrapezius muscle was prepared for in vivo microscopy 24 hours after inhalation exposures. Intraluminal infusion of the Ca2+ ionophore A23187 was used to evaluate endothelium-dependent arteriolar dilation. In control rats, A23187 infusion produced dose-dependent arteriolar dilations. In rats exposed to fine TiO2, A23187 infusion elicited vasodilations that were blunted in proportion to pulmonary particle deposition. In rats exposed to ultrafine TiO2, A23187 infusion produced arteriolar constrictions or significantly impaired vasodilator responses as compared to the responses observed in control rats or those exposed to a similar pulmonary load of fine particles. These observations suggest that at equivalent pulmonary loads, as compared to fine TiO2, ultrafine TiO2 inhalation produces greater remote microvascular dysfunction.

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Nanoparticle inhalation augments particle-dependent systemic microvascular dysfunction

The application of titanium dioxide for deactivation of bioparticulates: An overview

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Antibacterial performance of photocatalyst thin film fabricated by defection effect in visible light

The molecular structures of binuclear copper(II) complexes [Cu2REP(μ-OH)(ClO4)2] (4) and [Cu2REP(μ-Cl)Cl2] (5), in which REP = deprotonated 2,6-bis(1′-(4′-(2″-pyridyl)-2′-thiabutyl))-4-methylphenol, have been characterized by single-crystal X-ray diffraction. The former crystallizes in the triclinic space group Pl with a = 10.156(3), b = 12.631(3), c = 25.128(10) A, α = 92.03(3), β = 96.84(3), γ = 108.02(2),° and Z − 2. Complex 5 crystallizes in the monoclinic space group C2/c with a = 12.166(2), b = 11.825(2), c = 18.240(4) A, β = 100.97(2)°, and Z =4. All copper ions are pentacoordinated with ligation to a sulfur, a nitrogen, and the bridging phenolato oxygen of the REP ligand, the exogenous bridge, and a counteranion. The coordination geometry of each copper of the binuclear copper sites is square pyramidal in both 4 and 5. Magnetic susceptibility measurements in the temperature range 6–300 K reveal a strong antiferromagnetic spin exchange in 5 (exchange integral 2J = −460 cm−1). A diamagnetic behavior is observed for 4 according to a similar cryomagnetic investigation. The diamagnetism of 4 is further confirmed by measurements of magnetic susceptibility through Evan's method at room temperature. Complex 4 has no EPR signal. The powder EPR spectrum of 5 shows the typical triplet state characteristics with Δm = ±1 transitions at g = 2.15 and a weaker Δm = 2 transition at half field with g = 4.24.

Molecular Structures and Magnetic Properties of Strongly Antiferromagnetically Coupled Binuclear Copper(II) Complexes [CU2 REP(μ-X)(Y)2]

On decrit une methode d'analyse en phase liquide a haute pression (HPLC) pour le RDX et le HMX avec une nouvelle phase stationnaire, le copoly(vinylthiazole-vinylimidazole). Les temps d'elution pour le RDX et le HMX avec cette phase stationnaire en utilisant du methanol/ eau (proportion 60/40 a 90/10) en tant que phase mobile donnent HMX > RDX, ce qui est tres different d'une phase RP-18 de type commercial. La selectivite chromatographique (valeurs α) entre RDX et HMX est de l'ordre de 2,40 a 2,55. Cet avantage peut etre utilise, lors de la synthese de HMX p. ex., pour detecter la presence de petites impuretes d'env. 1 ppm de RDX dans le HMX.

Stationary phases. Part 39(1): Trace analysis of RDX in HMX on a novel copoly(vinylthiazole‐vinylimidazole) stationary phase by HPLC

Stationary Phases 21: A New Polar Substituted Triazine Stationary Phase for HPLC

By means of ultraviolet and visible spectroscopy we have studied the catecholase activity of two binuclear copper(II) complexes of general formula [Cu2REP(u-X)(Y)2] (1, X=OH and Y=ClO4; 2, X=Y=CI), REP =deprotonated 2, 6-bis(1′-(4′-(2″-pyridyl)-2′-thiabutyl))-4-methylphenol. Both complexes promote catalytic autoxidation of 3, 5-di-tert-butylcatechol (3, 5-DTBC) to 3, 5-di-tert-butylquinone (3, 5-DTBQ) in methanol, but not in acetonitrile.

Kuan-Jiunn Shieh

Papers

Antibacterial performance of photocatalyst thin film fabricated by defection effect in visible light

Molecular Structures and Magnetic Properties of Strongly Antiferromagnetically Coupled Binuclear Copper(II) Complexes [CU2 REP(μ-X)(Y)2]

Stationary phases. Part 39(1): Trace analysis of RDX in HMX on a novel copoly(vinylthiazole‐vinylimidazole) stationary phase by HPLC

Stationary Phases 21: A New Polar Substituted Triazine Stationary Phase for HPLC

UV/VIS Spectral Studies of Catecholase Activity of Binuclear Copper(II) Complexes [Cu2REP(μ-X)(Y)2]