Dionisios Panagiotaras

TiO2/palygorskite composite nanocrystalline films prepared by surfactant templating route: synergistic effect to the photocatalytic degradation of an azo-dye in water.

Microfibrous palygorskite clay mineral and nanocrystalline TiO(2) are incorporating in the preparation of nanocomposite films on glass substrates via sol-gel route at 500°C. The synthesis involves a simple chemical method employing nonionic surfactant molecule as pore directing agent along with the acetic acid-based sol-gel route without direct addition of water molecules. Drying and thermal treatment of composite films lead to the elimination of organic material while ensure the formation of TiO(2) nanoparticles homogeneously distributed on the surface of the palygorskite microfibers. TiO(2) nanocomposite films without cracks consisted of small crystallites in size (12-16 nm) and anatase crystal phase was found to cover palygorskite microfibers. The composite films were characterized by microscopy techniques, UV-vis, IR spectroscopy, and porosimetry methods in order to examine their structural properties. Palygorskite/TiO(2) composite films with variable quantities of palygorskite (0-2 w/w ratio) were tested as new photocatalysts in the photo-discoloration of Basic Blue 41 azo-dye in water. These nanocomposite films proved to be very promising photocatalysts and highly effective to dyes discoloration in spite of the small amount of immobilized palygorskite/TiO(2) catalyst onto glass substrates. 3:2 palygorskite/TiO(2) weight ratio was finally the most efficient photocatalyst while reproducible discoloration results of the dye were obtained after three cycles with same catalyst. It was also found that palygorskite showed a positive synergistic effect to the TiO(2) photocatalysis.

Attachment of Pseudomonas putida onto differently structured kaolinite minerals: a combined ATR-FTIR and 1H NMR study.

The attachment of Pseudomonas (P.) putida onto well (KGa-1) and poorly (KGa-2) crystallized kaolinite was investigated in this study. Batch experiments were carried out to determine the attachment isotherms of P. putida onto both types of kaolinite particles. The attachment process of P. putida onto KGa-1 and KGa-2 was adequately described by a Langmuir isotherm. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance were employed to study the attachment mechanisms of P. putida. Experimental results indicated that KGa-2 presented higher affinity and attachment capacity than KGa-1. It was shown that electrostatic interactions and clay mineral structural disorders can influence the attachment capacity of clay mineral particles.

Comprehensive Review on the Biodiesel Production using Solid Acid Heterogeneous Catalysts

Biodiesel can be produced by domestic resources like straight vegetable oil, animal oil/fats, tallow and waste cooking oil. Its use, instead of the conventional diesel, contributes to the reduction of the CO2 emissions. Production of biodiesel occurring from base catalyzed transesterification of the oil, direct acid catalyzed transesterification of the oil and/or conversion of the oil to its fatty acids and then to biodiesel. Two types of catalytic mechanisms can be used for the biodiesel production. These are the homogenous and heterogeneous catalytic processes. However, heterogeneous catalysis can be identified as solid and enzymatic. In addition solid heterogeneous catalysts can be classified as acid or base. Ηeterogeneous solid acid catalysts are of a great importance for biodiesel production. The most known catalysts of this type are zeolites, mixed oxides, sulfonic acid group catalysts, sulfonic acid modified mesoporus silica, heteropoly acids and polyoxonetalates, supported and substituted heteropoly acids and solid acids catalysts based in waste carbon. The major advantages of this type of catalysts are their reusability, their non-toxic and non-corrosive attributes as well as decrement of the biodiesel production cost.

Self-organised critical features in soil radon and MHz electromagnetic disturbances: Results from environmental monitoring in Greece

This paper addresses the issues of self-organised critical behaviour of soil-radon and MHz-electromagnetic disorders during intense seismic activity in SW Greece. A significant radon signal is re-analysed for environmental influences with Fast Fourier Transform and multivariate statistics. Self-organisation of signals is investigated via fractal evolving techniques and detrended fluctuation analysis. New lengthy radon data are presented and analysed accordingly. The data did not show self-similarities. Similar analysis applied to new important concurrent MHz-electromagnetic signals revealed analogous behaviour to radon. The signals precursory value is discussed.

Arsenic Geochemistry in Groundwater System

Dionisios Panagiotaras1, George Panagopoulos2, Dimitrios Papoulis3 and Pavlos Avramidis4 1Department of Mechanical Engineering, Laboratory of Chemistry, Technological Educational Institute (T.E.I.) of Patras, Patras 2Department of Mechanical and Water Resources Engineering, Technological Educational Institute (T.E.I.) of Messolonghi, Nea Ktiria, Messolonghi 3Department of Geology, University of Patras, Patras 4Technological Educational Institute (T.E.I.) of Mesolonghi, Laboratory of Geology for Aquatic Systems, Nea Ktiria Mesolonghi 1,2,3,4Greece

Comprehensive Experience for Indoor Air Quality Assessment: A Review on the Determination of Volatile Organic Compounds (VOCs)

Volatile Organic Compounds (VOCs) are toxic chemicals harmful for the environmental sustainability and human health. Due to the several types of VOCs and the diversity in their physico-chemical properties, it is difficult to develop standard methods for sampling and analysis. The majority of methods depend on the compounds of interest and the required duration of sampling. Each method is associated with a certain value of specificity and sensitivity. To date, however, no specific method qualifies as being the most accurate. This review reports the most common methods employed in determination of VOCs, based on the international literature.

Long-range memory patterns in variations of environmental radon in soil

This paper addresses issues of long-range memory and self-organisation in variations of radon in soil in Greece. The methods of rescaled-range, roughness-length, variogram, fractal dimension and block entropy were employed through lumping. Sliding was utilised with the wavelet spectral fractal technique. Antipersistent Hurst exponents in the range 0 < H < 0.5 were mainly identified. Persistent exponents (0.5 < H < 1) were also detected. Switching between persistency and antipersistency was observed and considered consistent with an underlying geo-environmental long-memory self-organisation. Fractal dimensions were in the range 1.2 < D < 2. The anomalous parts of the 2008 radon signal presented significantly lower fractal dimensions. Value ranges of Shannon, Shannon-per-letter, conditional, Tsallis and normalised Tsallis block entropies were 0.67 ≤ H(n) ≤ 2.73, 0.2 ≤ h(n) ≤ 0.7, 0.2 ≤ h(n) ≤ 0.6, 0.36 ≤ Sq ≤ 1.11, 0.50 ≤ Ŝq ≤ 9.55 respectively. The entropy values were affected by the block-size n. The entropic index values of the radon anomalies were significantly lower indicating long-memory underlying patterns. Underlying sources are discussed. The asperity-model is proposed.

Geochemistry of halloysite-7Å formation from plagioclase in trachyandesite rocks from Limnos Island, Greece

Abstract Trachyandesite rocks, occurring over an area of about 1 km2 in the southwest part of Limnos Island, Greece, are altered mainly to halloysite. The samples were collected and analysed by polarizing microscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analysis. The alteration of plagioclase to halloysite follows seven discrete stages that are described in detail. The geochemical evaluation of the data shows enrichment of the light REE (LREE) over heavy REE (HREE) as expressed by the (La/Yb)n ratio. The ΣLREE range from 206.44 to 272.30, while the sum of HREE varies from 11.01 to 26.26. The (La/Yb)n ratio ranges from 9.72 to 27.64. Fractionation among ΣLREE expressed as (La/Sm)n and between middle REE (MREE) and HREE is shown as (Tb/Yb)n ratios. The most altered rocks close to the fault zone have high (Tb/Yb)n ratios and low (La/Sm)n and Eu/Eu* ratios. Although mineralogy and clay mineral textures indicate hydrothermal genesis of halloysite, the geochemical data are not conclusive due to a secondary weathering effect.

Preliminary background indoor EMF measurements in Greece

The main purpose of this work was to investigate the fluctuation of Greek indoor electromagnetic field (EMF) intensity values and identify peaks that might occur. The scientific interest is mainly focused on the bands of extremely low-frequency (ELF) magnetic fields and radiofrequency (RF) electric fields which have been suggested to be possibly carcinogenic to humans by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). Electromagnetic radiation (EMR) measurements were performed in a variety of indoor dwellings, in Attica and in the islands of Zakynthos and Lesvos. A total number of 4540 measurements were taken in a wide frequency range (50 Hz-2100 MHz) of which 3301 in Attica, 963 in Lesvos and 276 in Zakynthos. Statistical analysis of the data revealed specific statistically significant differences between the mean values of the electric (ELF and RF) but not the magnetic (ELF) field strengths measured at different distances from the EMF source, as well as between some of the mean values of the RF electric field at different bands. Some statistically significant differences between mean electric field values at different geographic locations were also identified. As far as the RF electric field is concerned, the maximum values, in most cases, were below 0.5 V/m, however increased values above 1 V/m and up to 5.6 V/m were occasionally observed. The ELF magnetic field values were lower than 1 μT. It may be concluded that overall, the observed indoor EMF intensity values remained well below domestic and European established limits.

Use of halloysite nanotubes to reduce ammonium concentration in water and wastewaters

Halloysite nanotubes (HNTs) were used for the reduction of ammonium concentration in aqueous solutions under various experimental conditions. The results indicated that HNTs exhibit fast adsorption rates and high removal capacity for the NH4+ ions at neutral pH. The removal efficiency of the treated halloysite depends on the mass/volume ratio and the initial concentration of NH4+ ions. The adsorption capacity of the material was examined for different mass/volume ratios at initial concentration <40 mg/L and it was found that in some cases the material exhibit up to 30% removal efficiency. Halloysite clay removal efficiency was also examined in a 4–10 pH range and it was found that it is increasing continually upon increasing pH values. Additionally the adsorption efficiency is strongly and negatively related to temperature. Langmuir adsorption models were applied to describe the equilibrium isotherms. Estimation of thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and change in free energy (ΔG°) confirms that the process is spontaneous and exothermic. Adsorption experiments were also performed in aqueous NH4+ solutions in the presence of other cations and it was found that the removal efficiency for NH4+ follows the order Na > K > Zn > Cu > Mn > Ca > Fe > Mg. The above results indicate that halloysite clay mineral can be considered as a new material for use in large and/or industrial-scale applications for water and wastewater purification purposes.