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Although silver nanoparticles (AgNPs) appear to be promising for certain medical/pharmaceutical applications, they present significant disadvantages when it comes to environmental applications due to the need for recovery of the metal (Ag) which is considered hazardous for the environment. The present study examines the antimicrobial properties and mechanism of action of immobilized (on Al2O3) silver nanoparticles’ (1 wt% Ag-iNPs) regarding the treatment of E. coli microbial solutions. Antimicrobial experiments were conducted in semi-batch mode using a three-phase continuous flow stirred tank reactor. Every treated sample was taken from the outlet of the reactor for the time intervals of 0, 5 and 25 min. To ensure that the bactericidal property of Ag-iNPs is not attributed to the dissolution of surface silver (as free Ag+), a suitable Ag+ scavenger was used as already described in our earlier studies. Regarding the molecular analysis performed under this study, the regulation of key enzymes involved in bactericidal activity of E. coli, was examined, after their treatment either with immobilized silver nanoparticles (Ag-iNPs) or AgNO3. Specifically, 50 mL sample for each case was centrifuged (10 min at 10,000 rpm) and the pellet (≈109 cells) was immediately subjected to total RNA extraction. For real-time RT-qPCR analyses, 1 μg of total RNA was converted into cDNA. It was found that PldA gene, which encodes outer membrane’s phospholipase A (OMPLA), was up-regulated after 5 and 25 min of treatment with Ag-iNPs. OMPLA’s activation appears to be the initial step of Ag-iNPs bactericidal mechanism that ultimately leads to the creation of holes on the outer membrane (OM), irreversibly disturbing the cells’ respiration cycle. In addition, after treatment with Ag-iNPs, Blue copper oxidase CueO (encoded by cueO gene) was found to be over-produced and appears to play a key-role in the oxidative transfer of silver from the surface of Ag-iNPs to the cell. This leads to the Ag-induced displacement of copper from its native protein sites such as CusS/CusR, a fact that causes the release of labile copper and ROS inside the cell. In addition, TEM analysis of bacteria treated with Ag-iNPs revealed severe morphological changes (“holes”) on bacterial outer membrane, indicating that there is an intermediate step in the proposed antimicrobial mechanism which takes place on the surface of Ag-iNPs.

For the first time ever, a 0.1 wt% Pt/Al 2 O 3 catalyst was prepared by novel inkjet printing and compared against two catalysts prepared by a standard and modified wet impregnation method. The printed catalyst was found to present excellent activity and wide operating temperature window on the selective catalytic reduction of NO by H 2 under strongly oxidizing conditions (H 2 -SCR) in the very low-temperature range of 100–200 °C. The transient studies performed in the present work indicated that the printing process followed led to a unique surface structure of the printed catalyst that probably favors the formation of different active intermediate NO x species, which are active at very low reaction temperatures. Moreover, it was found that the inkjet printing protocol followed resulted in a relatively uniform nano-spherical structure of the developed catalyst.

Detailed mechanistic studies (ex-situ SSITKA-DRIFTS) have been performed on 1 wt.% Pd-0.5 wt.% Cu/γ-Al 2 O 3 and 1 wt.% Pd-0.5 wt.% Cu/TiO 2 -Al 2 O 3 catalysts concerning the NO 3 − /H 2 and NO 3 − /H 2 /O 2 reactions, in order to elucidate the promoting role of TiO 2 and O 2 in suppressing the unwanted NH 4 + production in water media. It is demonstrated, for the first time ever, that the mechanism of N 2 production strongly depends on the nature of the support and the presence of O 2 (air) in the gas feed stream. In particular, these parameters were found to significantly affect the formation of different adsorbed active intermediate N-species on the support or/and metal (Pd, Cu) surface, providing documentary information about the signalling pathways leading to the formation of NH 4 + and N 2 . This study provides for the first time ever, an alternative stepwise pathway for the reduction of NO 2 − (ads) to NO (ads) and further to N 2 on the support or metal-support interface (metal cation sites), instead of Pd metal surface. Based on the results of the present work, it is concluded that the reduction of NO 2 − (ads) species is favoured on partially oxidized Pd (when adequate supply of oxygen is available). In the case of Pd-Cu/TiO 2 -Al 2 O 3 (NO 3 − /H 2 ), both adsorption and reduction of NO 2 − (ads) take place on the support surface leading to the formation of NO (ads) on TiO 2 (Ti 4+ -NO or Ti 4+ -NO + ), which in turns leads to enhanced N 2 production. In addition, the latter system exhibits greatly enhanced selectivity towards N 2 , under oxidizing conditions, possibly due to the interaction of NO x species (e.g., Pd-NO/N, Ti 4+ -NO/NO + ) at the metal-support interface. On the contrary, in the absence of both titanium dioxide in the support and oxygen in the feed, the sequential reduction of NO 3 − (ads) takes place on different active sites of the catalyst surface, indicating that H 2 is easily dissociated on Pd particles and then spills over onto the Cu and the metal oxides (support), and secondly that NO (ads) is possibly diffused from the support to adjusted Pd sites, for further reaction. These mechanistic findings are very important as they reveal, for the first time ever, the active involvement of the support in the reaction mechanism and its positive effect on N 2 production.

During the last four decades, inkjet printing has become one of the most prevalent printing technologies for home and office desktop printing applications. Advances in inkjet technology allow the printing of full-color, high-resolution photographs of equivalent quality to those from other printing techniques that have prevailed in the recent past. In the commercial printing sector, inkjet technology is being widely used for digital proofing prior to running a print job on a press; for short-run, wide-format digital printing such as posters for outdoor advertising; and for applications that require printing onto non-paper substrates such as rigid display boards. In addition, inkjet printers are being developed for integration with offset presses to print customized information in magazines, such as tailored advertising (Sirringhaus & Shimoda, 2003). Finally, in the general industrial sector, the inkjet technology is considered as the leading technology for printing customized information such as “sell-by” dates and product identification codes, as part of packaging or production processes.

All rights reserved.Abstract: To date, very few prescriptive studies have been reported in the literature concerning the catalytic removal of pharmaceutical substances in wastewater using H2 in the presence of O2 for the in situ formation of H2O2, while the mechanism of the reaction has not been studied in detail yet. Hydrogen peroxide is a potent oxidizing agent used extensively in catalytic wet air oxidation (CWAO) applications and can be used for the elimination of pharmaceuticals from waste water. In the present work, an attempt has been made to elucidate the actual effects of the in situ production of hydrogen peroxide on the CWAO of pharmaceuticals. Therefore, the effects of the nature of the active phase (Pd, Pt, and Rh), as well as the feed gas composition have been examined toward the reaction at hand. The results showed that 1% Pd/Al2O3 and 1% Rh/Al2O3 are the most effective catalysts for the elimination of paracetamol from the reaction medium using hydrogen-rich streams, having a conversion of up to 70% in 2 h. A maximum conversion of paracetamol of 90% was obtained in just 30 min of reaction over 1 wt.% Rh/Al2O3, when using pure hydrogen in the feed. Total organic carbon measurements performed over the latter catalyst showed that practically no organic carbon is removed from the liquid phase, indicating the conversion of paracetamol to a different organic (probably aromatic) compound, through hydrogenation. Toxicity tests that followed showed a dramatic decrease in the toxicity of the products solution, indicating that paracetamol hydrogenation might be a promising method for the elimination of its toxicity.

Presented at: IWA Regional Conference on Waste and Wastewater Management, Science and Technology, 2013, Limassol, Cyprus, 26-28 June The present work reports up-to-date information regarding the reaction mechanism of the catalytic hydrogenation of nitrates in water media. In the present mechanistic study, an attempt is made, for the first time, to elucidate the crucial role of several catalysts and reaction parameters in the mechanism of the NO3-/H2 reaction. Steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with ex situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed on supported Pd-Cu catalysts for the NO3-/H2 and NO3-/H2/O2 reactions. The latter experiments revealed that the formation and surface coverage of various adsorbed active intermediate N-species on the support or Pd/Cu metal surface is significantly favored in the presence of TiO2 in the support mixture and in the presence of oxygen in the reaction's gaseous feed stream. The differences in the reactivity of these adsorbed N-species, found in the present work, adequately explain the large effect of the chemical composition of the support and the gas feed composition on catalyst behaviour (activity and selectivity). The present study leads to solid mechanistic evidence concerning the presence of a hydrogen spillover process from the metal to the support. Moreover, this study shows that Cu clusters are active sites for the reduction of nitrates to nitrites.

The present paper involves a detailed study of the selective catalytic reduction of nitrates in aqueous mediums by the use of H 2 in the presence of O 2 over monometallic and bimetallic supported catalysts. In this study, an attempt has been made to improve the denitrification efficiency ( X NO 3 − , S N2 ) of several catalysts by regulating some experimental parameters that are involved in the process. Therefore, the effects of the type of reactor (semi-batch reactor vs continuous flow reactor), the nature of the active phase (Pd, Cu, and Pd-Cu) and the particle size of γ-Al 2 O 3 spheres (particle diameter = 1.8 mm and 3 mm) on catalytic activity and reaction selectivity, as well as the adsorption capacity of γ-Al 2 O 3 spheres for nitrates, were examined. As the review indicates, most of the research has so far been conducted on batch or semi-batch reactors. This study successfully demonstrates the benefits of using a continuous flow reactor in terms of catalytic activity ( X NO 3 − , %) and reaction selectivity ( S N2 , %). Another important aspect of this study is the crucial role of bimetallic Pd-Cu clusters for the prevention of NH 4 + formation. Moreover, the use of 1.8 mm diameter γ-Al 2 O 3 spheres as a support was proved to significantly enhance the catalytic performance of bimetallic Pd-Cu catalysts towards nitrate reduction compared to 3 mm diameter γ-Al 2 O 3 spheres. This difference may be attributed to mass (NO 3 − , OH − ) transfer effects (external mass transfer phenomena).

The selective catalytic reduction of NO by ethanol under strongly oxidizing conditions (ethanol-SCR) in the wide-temperature range of 150–400 °C has been studied over Ag supported on a series of metal oxides (e.g., MgO, Y 2 O 3 , CuO, CeO 2 , SiO 2 , MgO-CeO 2 -Al 2 O 3 ). The Ag/MgO, Ag/CeO 2 and Ag/Al 2 O 3 solids showed the best catalytic behavior with respect to N 2 and CO 2 yield and the widest temperature window of operation compared with the other single metal oxide-supported Ag solids. An optimum 25 wt% MgO-25 wt% CeO 2 -Al 2 O 3 support composition was found in terms of specific reaction rate of N 2 production (mol N 2 /g cat s) and CO 2 selectivity. High NO conversions (60–90%), N 2 selectivities (95–99%) and CO 2 selectivities (>97%) were also obtained in the 150–400 °C range at a GHSV of 40,000 h −1 with the low 0.1 wt% Ag loading and using a feed stream of 0.05 vol% NO, 0.1 vol% ethanol, 5 vol% O 2 , 5 vol% H 2 O and He as balance gas. Moreover, the latter catalytic system exhibited a high stability in the presence of 50 ppm SO 2 in the feed stream. N 2 selectivity values higher than 98% and CO 2 selectivities higher than 97% were obtained over the 0.1 wt% Ag/MgO-CeO 2 -Al 2 O 3 catalyst in the 150–400 °C range in the presence of water and SO 2 in the feed stream. The above-mentioned results led to the submission of a patent application for the commercial exploitation of Ag/MgO-CeO 2 -Al 2 O 3 catalyst towards a new NO x control technology in the low-temperature range of 150–250 °C using ethanol as reducing agent. DRIFTS studies after adsorption of NO, and transient titration of the adsorbed surface intermediate NO x species with H 2 experiments, have revealed some preliminary important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., number and location of possible active NO x intermediate species).

The present article consists a critical up-to-date review of the research conducted so far on the selective catalytic reduction of NOx with hydrogen under lean-burn conditions as an alternative technology to the existing NH3- and HC-SCR. Noble Metal based catalysts are described in detail with emphasis on the analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the support chemical composition and the preparation method and structure of the catalysts on the reaction mechanism is also discussed. Finally, the effects of various reaction parameters on the catalysts activity, selectivity and stability with reaction time are discussed in detail.

Nickel supported on alumina catalysts have been prepared using various synthesis methods (dry impregnation, co-precipitation, sol–gel) and evaluated for the hydrogenation of benzene contained in gasoline. The evaluation was carried out in a laboratory scale high pressure fixed bed reactor fed with a stream of surrogated reformate gasoline consisted by a mixture of hexane, benzene and toluene. All catalysts have been characterized by the joint use of various physicochemical characterization methods (XRF, BET, TGA, SEM, XRD, UV–vis DRS and XPS) in order to correlate their catalytic performances to their physicochemical properties. The results obtained revealed that sol–gel procedure, especially when it is followed by supercritical drying (aerogel), produced the most promising catalysts for the aforementioned catalytic process. Sol–gel methodology ensured the best compromise between dispersion of the nickel phase and its interaction with the support surface. Co-precipitated catalysts exhibited important activities but lower than those of the sol–gel catalysts. The catalyst prepared by dry impregnation proved to be the less active. Calcination of the catalysts before their activation by reduction decreased their activities.

Based on the current 2008/98/EC Directive, EU Member States are obliged to establish a waste management plan, waste prevention programmes by the end of 2013 and ensure that the general public will have the opportunity to participate in the elaboration of such plans and programmes. Energy recovery is one of the options laid down in the Directive as a possible solution and thus, the current study focuses on the environmental, technical, economical and marketing aspects of the operation of a modern Waste-to-Energy (WtE) plant in the Kotsiatis landfill. The present study includes the analysis of WtE plant aspects, such as the public’s opinions, marketing and promotional activities, environmental depollution, financing options and operational costs. Personal interviews were conducted in the villages around the Kotsiatis landfill, and the techno economical study was based on the available literature. Results have shown that the construction of a WtE plant in the area will improve the quality of life of the habitants, reduce the current environmental problems, and that it is economically viable without governmental subsidy. The construction of a WtE plant that will be capable of incinerating 100,000 tonnes of waste/year will result to 11 MW of reliable power, in addition to the environmental benefits. The Net Present Value of such an investment will be €2,655,730 with an Internal Rate of Return of 10.5 %. However, the general public in the Kotsiatis village is against the construction of such a plant, but this is due to the lack of trustworthy information about incineration technologies (and renewable energy in general) from the local media. On the contrary, the general public in the vicinity of the area is in favour of a WtE plant, as they acknowledge the potential benefits.

The present work reports data on a novel catalyst having excellent activity, selectivity and stability for the selective reduction of nitric oxide to nitrogen in the presence of ethanol or ethanol/hydrogen mixture as reducing agent, in the low temperature range of 150-300°C and in the presence of excess oxygen, H2O and SO2 in the feed. The novelty of the present catalyst compared to other patented ones, for the reaction at hand, lies upon the simplicity and the remarkably low Ag loading (wt%) used, characteristics that are required for a practical application. In addition, the latter catalyst shows significant activity (rate of NO reduction) at much lower temperatures (below 300°C) compared to other already patented catalysts. The present inventive catalyst consists of silver crystals that are in contact with a mixed oxide support comprised of MgO, CeO2 and Al2O3 in 1:1:2 wt% ratio. This novel catalyst presents high activity in terms of NO conversion (XNO = 60-90%) and high selectivities towards N2 (SN2 = 92-95%) and CO2 (SCO2 > 97%) in the range of 150-400°C, at a GHSV of 40,000 h-1 and using a feed stream of 0.05vol% NO, 0.1vol% EtOH, 5vol% O2 and 5vol% H2O. To our knowledge, this is the highest selectivity towards N2 and CO2 ever reported. In addition, the current catalyst shows remarkable stability with time on stream and in the presence of 5 vol% H2O and 50 ppm SO2 in the feed stream. After 48 h on stream the patented catalyst retains its stability expressed in high activity (XNO > 80%) and selectivities to N2 (SN2 > 95%) and CO2 (SCO2 > 97%).

The selective catalytic reduction of nitrates (NO 3 − ) in water mediums towards N 2 formation by the use of H 2 and in the presence of O 2 (air) in the gas feed has been investigated under a continuous flow process over Pd–Cu supported on various mixed metal oxides, x wt.% M x O y /γ-Al 2 O 3 (M x O y = CeO 2 , MgO, Mn 2 O 3 , Cr 2 O 3 , Y 2 O 3 , MoO 2 , Fe 2 O 3 and TiO 2 ). It is demonstrated for the first time that a remarkable improvement of both catalysts activity and N 2 reaction selectivity can be achieved when increasing the liquid flow rate in the continuous flow process. In particular, it was found that NO 3 − reduction rates up to more than two times higher and NH 4 + selectivity values up to twenty times lower can be obtained when increasing the liquid flow rate from 2 to 6 mL/min. Moreover, it was proven for the first time, in a continuous flow process, that the presence of oxygen (or air) has a remarkable positive effect on the reaction's selectivity towards nitrogen. The reaction's selectivity towards NH 4 + can be decreased by up to three times when 20 vol.% air is added in the gas feed of the NO 3 − /H 2 continuous flow reaction. The Pd–Cu clusters supported on TiO 2 -, CeO 2 - and MgO-coated γ-Al 2 O 3 spheres showed the best catalytic behaviour compared with the rest of supports examined, both in the presence and in the absence of oxygen in the reducing feed gas stream. In addition, it was found that the initial concentration of nitrates in the liquid feed can significantly affect catalysts activity and reaction's selectivity. A positive apparent reaction order towards nitrates of 0.9 was calculated on Pd–Cu/TiO 2 /Al 2 O 3 .