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Acoustically enhanced ganglia dissolution and mobilization in a monolayer of glass beads

(2006) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Eric T. Vogler

A pore network consisting of a monolayer of glass beads was constructed for experimental investigation of the effects of acoustic waves on the dissolution and mobilization of perchloroethylene (PCE) ganglia. Dissolution experiments were conducted with acoustic wave frequencies ranging from 75 to 225 Hz at a constant pressure amplitude of 3.68 kPa applied to the inlet of the monolayer. Ganglia mobilization experiments were conducted with a constant acoustic wave frequency of 125 Hz and acoustic pressure amplitudes ranging from 0 to 39.07 kPa. Effluent dissolved PCE concentrations were observed to increase in the presence of acoustic waves with the greatest increase (over 300%) occurring at the lowest frequency employed (75 Hz). Acoustic waves were also observed to mobilize otherwise immobile PCE ganglia, break them apart, and further enhance dissolution.

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Acoustically enhanced multicomponent NAPL ganglia dissolution in water saturated packed columns

(2004) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Eric T. Vogler

The impact of acoustic pressure waves on multicomponent nonaqueous phase liquid (NAPL) ganglia dissolution in water saturated columns packed with glass beads was investigated. Laboratory data from dissolution experiments with two and three component NAPL mixtures suggested that acoustic waves significantly enhance ganglia dissolution due to the imposed oscillatory interstitial water velocity. The dissolution enhancement was shown to be directly proportional to the acoustic wave frequency. Furthermore, it was demonstrated that the greatest dissolution enhancement in the presence of acoustic waves is associated with the component of the NAPL mixture having the smallest equilibrium aqueous solubility. Finally, square shaped acoustic waves were shown to lead to greater NAPL dissolution enhancement compared to sinusoidal and triangular acoustic waves. The results of this study suggested that aquifer remediation using acoustic waves is a promising method particularly for aquifers contaminated with NAPLs containing components with very low equilibrium aqueous solubilities.

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Analysis of a ,model for contaminant transport in fracture media in the presence of colloid

(1995) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Assem Abdel-Salam

A mathematical model has been developed to study the cotransport of contaminants with colloids in saturated rock fractures. The contaminant is assumed to decay, and sorb on to fracture surfaces and on to colloidal particles, as well as to diffuse into the rock matrix; whereas, colloids are envisioned to deposit irreversibly on to fracture surfaces without penetration into the rock matrix. The governing one-dimensional equations describing the contaminant and the colloid transport in the fracture, colloid deposition on to fracture surfaces, and contaminant diffusion into the rock matrix are coupled. This coupling is accomplished by assuming that the amount of contaminant mass captured by colloidal particles in solution and the amount captured by deposited colloids on fracture surfaces are described by modified Freundlich reversible equilibrium sorption relationships, and that mass transport by diffusion into the rock matrix is a first-order process. The contaminant sorption on to fracture surfaces is described by a linear equilibrium sorption isotherm, while the deposition of colloids is incorporated into the model as a first-order process. The resulting coupled contaminant transport non-linear equation is solved numerically with the fully implicit finite difference method. The constant concentration as well as the constant flux boundary conditions have been considered. The impact of the presence of colloids on contaminant transport is examined. According to model simulations the results show that, depending on the conditions of the physical system considered, colloids can increase or decrease the mobility of contaminants.

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Analysis of one-dimensional solute transport through porous media with spatially variable retardation factor

(1990) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Peter K. Kitanidis

A closed-form analytical small-perturbation (or first-order) solution to the one-dimensional advection-dispersion equation with spatially variable retardation factor is derived to investigate the transport of sorbing but otherwise nonreacting solutes in hydraulically homogeneous but geochemically heterogeneous porous formations. The solution is developed for a third- or flux-type inlet boundary condition, which is applicable when considering resident (volume-averaged) solute concentrations, and a semi-infinite porous medium. For mathematical simplicity it is hypothesized that the sorption processes are based on linear equilibrium isotherms and that the local chemical equilibrium assumption is valid. The results from several simulations, compared with predictions based on the classical advection-dispersion equation with constant coefficients, indicate that at early times, spatially variable retardation affects the transport behavior of sorbing solutes. The zeroth moments corresponding to constant and variable retardation are not necessarily equal. The impact of spatially variable retardation increases with increasing Péclet number.

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Analysis of polycyclic aromatic hydrocarbons in wastewater treatment plant effluents using hollow fibre liquid phase microextraction

(Elsevier, 2005) Charalabaki Magdalini; Psyllaki Eleftheria; Ψυλλακη Ελευθερια; Mantzavinos Dionysis; Μαντζαβινος Διονυσης; Kalogerakis Nikos; Καλογερακης Νικος

A simple and efficient method for the enrichment of low molecular weight polycyclic aromatic hydrocarbons (PAHs) in effluents originating from wastewater treatment plants is presented here. The proposed protocol couples the recently introduced hollow fibre liquid-phase microextraction (LPME) method with gas chromatography–mass spectrometry. Method parameters were controlled and the optimised experimental conditions were: 5 ml aqueous samples, containing 2.5% NaCl w/v, stirred at 1000 rpm, extracted with toluene for 15 min. The developed protocol yielded a linear calibration curve in the concentration range from 0.5 to 50 lg l1 for all target analytes (namely acenaphthene, phenanthrene, fluoranthene and pyrene) and limits of detection in the low lg l1 level (0.005–0.011 lg l1). The repeatability and interday precision of the method varied between 2.7% and 11.3% and 7.9% and 14.4% respectively. The relative recoveries from different types of natural water samples revealed that matrix had a small effect on the hollow fibre LPME process. The developed method was then applied for the determination of PAHs contamination in effluent samples taken from two major municipal wastewater treatment plants. The results were compared with those obtained with solid-phase microextraction. The ability of both microextraction methods to concentrate organic analytes was demonstrated as both methods confirmed the presence of PAHs as well as of phthalates in the examined effluent samples.

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Analytical models for one-dimensional virus transport in saturated porous media

(1995) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Youn Sim

Analytical solutions to two mathematical models for virus transport in one-dimensional homogeneous, saturated porous media are presented, for constant flux as well as constant concentration boundary conditions, accounting for first-order inactivation of suspended and adsorbed (or filtered) viruses with different inactivation constants. Two processes for virus attachment onto the solid matrix are considered. The first process is the nonequilibrium reversible adsorption, which is applicable to viruses behaving as solutes; whereas, the second is the filtration process, which is suitable for viruses behaving as colloids. Since the governing transport equations corresponding to each physical process have identical mathematical forms, only one generalized closed-form analytical solution is developed by Laplace transform techniques. The impact of the model parameters on virus transport is examined. An empirical relation between inactivation rate and subsurface temperature is employed to investigate the effect of temperature on virus transport. It is shown that the differences between the two boundary conditions are minimized at advection-dominated transport conditions.

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Analytical models for virus adsorption and inactivation in unsaturated porous media

(1999) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Youn Sim

Analytical models for virus adsorption and inactivation in batch systems of homogeneous, isothermal, unsaturated porous media were developed. The models account for virus sorption onto liquid–solid as well as air–liquid interfaces and inactivation of viruses in the liquid phase and at both interfaces. Mathematical expressions appropriate for virus sorption onto liquid–solid and air–liquid interfaces were developed as functions of the soil moisture variation. The models were solved analytically by Laplace transform procedures. The effects of soil moisture variation on virus sorption at the liquid–solid as well as air–liquid interfaces were investigated. Available experimental data from virus adsorption-inactivation batch studies were successfully simulated by one of the models developed in this work.

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Analytical solutions for monodisperse and polydisperse colloid transport in uniform fractures

(2003) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Scott C. James

Analytical solutions are derived describing the transport of suspensions of monodisperse as well as polydisperse colloid plumes of neutral buoyancy within a fracture with uniform aperture. Various initial and boundary conditions are considered. It is shown that both the finite colloid size and the characteristics of the colloid diameter distribution significantly affect the shape of colloid concentration breakthrough curves. Furthermore, increasing the standard deviation of the colloid diameter enhances colloid spreading and increases the number of attached colloids when colloid–wall interactions are taken into account. Excellent agreement between available experimental data and the analytical solution for the case of an instantaneous release of monodisperse colloids in a natural fracture is observed.

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Analytical solutions for one-dimensional colloid transport in saturated fractures

(1994) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Assem Abdel-Salam

Closed-form analytical solutions for colloid transport in single rock fractures with and without colloid penetration into the rock matrix are derived for constant concentration as well as constant flux boundary conditions. A single fracture is idealized as two semi-infinite parallel plates. It is assumed that colloidal particles undergo irreversible deposition onto fracture surfaces and may penetrate into the rock matrix, and deposit irreversibly onto rock matrix solid surfaces. The solutions are obtained by taking Laplace transforms to the governing transport equations and boundary conditions with respect to time and space. For the case of no colloid penetration into the rock matrix, the solutions are expressed in terms of exponentials and complimentary error functions; whereas, for the case of colloid penetration into the rock matrix, the solutions are expressed in terms of convolution integrals and modified Bessel functions. The impact of the model parameters on colloid transport is examined. The results from several simulations indicate that liquid-phase as well as deposited colloid concentrations in the fracture are sensitive to the fracture surface deposition coefficient, the fracture aperture, and the Brownian diffusion coefficient for colloidal particles penetrating the rock matrix. Furthermore, it is shown that the differences between the two boundary conditions investigated are minimized at dominant advective transport conditions. The constant concentration condition overestimates liquid-phase colloid concentrations, whereas the constant flux condition leads to conservation of mass.

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Analytical solutions for solute transport in saturated porous media with semi-infinite or finite thickness

(1999) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Youn Sim

Three-dimensional analytical solutions for solute transport in saturated, homogeneous porous media are developed. The models account for three-dimensional dispersion in a uniform flow field, first-order decay of aqueous phase and sorbed solutes with different decay rates, and nonequilibrium solute sorption onto the solid matrix of the porous formation. The governing solute transport equations are solved analytically by employing Laplace, Fourier and finite Fourier cosine transform techniques. Porous media with either semi-infinite or finite thickness are considered. Furthermore, continuous as well as periodic source loadings from either a point or an elliptic source geometry are examined. The effect of aquifer boundary conditions as well as the source geometry on solute transport in subsurface porous formations is investigated.

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Anion-templated assembly of a supramolecular cage complex

(Wiley‐vch verlag gmbh, 1998) Elefteria Psillakis; Michael D Ward; Jon A McCleverty; John C Jeffery; Charles‐Antoine Carraz; Karen LV Mann; James S Fleming

THe templating effect of the tetrafluoroborate ion leads to assembly of four CoII ions and six bridging ligands around this anion to give a tetrahedral complex with a bridging ligand along each edge and the anion trapped in the central cavity (shown below). Surprisingly under identical conditions but with NiII a simpler dinuclear complex forms.

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Anionengesteuerter aufbau eines supramolekularen käfigkomplexes

(WILEY‐VCH Verlag GmbH, 1998) KLV Mann; James S Fleming; Charles‐Antoine Carraz; John C Jeffery; E Psillakis; Jon A McCleverty; Michael D Ward

Der Templateffekt eines Tetrafluoroborat-Ions führt dazu, daß sich vier Co II-Ionen und sechs zweifach zweizähnige Liganden um dieses Ion zusammenlagern, wobei ein tetraedrischer Vierkernkomplex mit einem verbrückenden Liganden entlang jeder Kante entsteht und das Anion im zentralen Hohlraum eingeschlossen ist (siehe unten). Überraschenderweise wird mit Ni II unter gleichen Bedingungen ein einfacherer Zweikernkomplex erhalten.

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Application of solvent microextraction to the analysis of nitroaromatic explosives in water samples

(Elsevier, 2001) Psyllaki Eleftheria; Ψυλλακη Ελευθερια; Kalogerakis Nikos; Καλογερακης Νικος

The application of solvent microextraction to the analysis of nitroaromatic explosives is presented. Extraction of 11 nitroaromatics was achieved by suspending 1 ml of organic solvent to the tip of a microsyringe in a stirred aqueous solution. Parameters such as extraction solvent, stirring rate, salt concentration and sampling time were studied and optimized. The limits of detection using bench-top quadrupole mass spectrometry and short extraction times (15 min) were found to be between 0.08 and 1.3 mg/ l and the relative standard deviations ranged between 4.3 and 9.8%. Although precision and accuracy of quantification of the method are still needed, solvent microextraction proved to be a fast, simple and inexpensive tool for preconcentration and matrix isolation of nitroaromatics on a microscale

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Artificial tracers for geothermal reservoir studies

(1993) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος

Safe disposal of thermally spent geothermal brines that contain environmentally hazardous constituents is commonly obtained by reinjection. The reinjection process also serves to maintain reservoir pressure, enhance thermal recovery, and eliminate possible compactional subsidence. To avoid premature thermal breakthrough of reinjected fluids, tracer tests are employed for detection and evaluation of preferential path networks. In this paper some promising tracers that have not received much attention in geothermal reservoir studies are discussed, and a comprehensive tabulation of field sites of artificial tracer utilization is presented. Chemical and transport processes responsible for tracer retention by the formation of reservoir solids, as well as available tracer detection techniques, are emphasized.

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Attachment of bacteriophages MS2 and ΦX174 onto kaolinite and montmorillonite: Extended-DLVO interactions

(2011) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Vasiliki I. Syngouna

This study aims to gain insights into the interaction of virus particles with clay colloids. Bacteriophages MS2 and X174 were used as model viruses and kaolinite (KGa-1b) and montmorillonite (STx-1b) as model colloids. The experimental data obtained from batch experiments of MS2 and X174 attachment onto KGa-1b and STx-1b suggested that virus attachment is adequately described by the Freundlich isotherm equation. Both MS2 and X174 were attached in greater amounts onto KGa-1b than STx-1b with MS2 having greater affinity than X174 for both clays. Furthermore, extended-DLVO interaction energy calculations explained that the attachment of viruses onto model clay colloids was primarily caused by hydrophobic interaction. The theoretical and experimental results of this study were found to be in good agreement with previous findings.

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

(2011) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Georgios Papavassiliou; Michael Fardis; Eleni Karakosta; Ioanna A. Vasiliadou; Dionisios Panagiotaras; Dimitris Papoulis

The attachment of Pseudomonas (P.) putida onto well (KGa-1) and poorly (KGa-2) crystallized kaolinitewas 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 wasadequately 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.

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Biosorption of Cu 2+ and Ni 2+ by Arthrospira platensis with different biochemical compositions

(2015) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Dimitris Georgakakis; Hüseyin Bozkurt; Abuzer Çelekli; Dimitris Mitrogiannis; Giorgos Markou

This study is focused on copper and nickel biosorption onto Arthrospira platensis biomass of different biochemical compositions. Four types of A. platensis were employed, namely: (1) typical dry biomass (TDB), (2) carbohydrate-enriched dry biomass (CDB), (3) typical living biomass (TLB), and (4) carbohydrateenriched living biomass (CLB). The CDB was produced using a cultivation mode where phosphorus was the limiting nutrient. The biosorption of both metals investigated was shown to be very fast. Most of the metal sorption capacity of the biomass was filled within 15–30 min, and equilibrium was achieved within 30–60 min. The cultivation conditions (nutrient repletion or depletion) did not affect the pattern of copper and nickel biosorption kinetics. The capacity for copper ions biosorption was significantly positively affected by the accumulation of carbohydrates in the dry biomass, but was negatively affected by the accumulation of carbohydrates in the living biomass. For nickel ions, the alteration of biomass had a little but positive effect on the dry biomass, and a greater negative effect (about 30% lower biosorption capacity) on the living biomass. Living biomass exhibited a higher biosorption capacity than dry biomass, for both metals. The biosorption of copper and nickel onto A. platensis biomass occurred mainly due to the mechanisms of ion exchange and complexation, and less to physical adsorption.

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Bootstrap estimation of the mass transfer coefficient of a dissolving nonaqueous phase liquid pool in porous media

(2002) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Pin-Yi Hsuan; Marios M. Fyrillas

A new method for confidence interval estimation of mass transfer coefficients suitable for dissolving dense nonaqueous phase liquid pools in homogeneous, water-saturated porous media is developed. The method is based on the bootstrap resampling technique in conjunction with a least squares regression procedure. The method is successfully applied to experimental data collected from bench scale trichloroethylene pool dissolution experiments. INDEX TERMS: 1829 Hydrology: Groundwater hydrology; 1831 Hydrology: Groundwater quality; 1832 Hydrology: Groundwater transport; KEYWORDS: NAPL pool dissolution, mass transfer coefficient, bootstrap, estimation, contaminant transport

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Boronic acid dendrimer receptor modified nanofibrillar cellulose membranes

(Royal Society of Chemistry, 2010) Elefteria Psillakis; chael J. Bonn; Matthew Helton; Karen J. Edler

Cellulose nanofibrils from sisal of typically 4–5 nm diameter and ca. 250 100 nm length are reconstituted into thin films of ca. 6 mm thickness (or thicker freestanding films). Pure cellulose and cellulose composite films are obtained in a solvent evaporation process. A boronic acid appended dendrimer is embedded as a receptor in the nanofibrillar cellulose membrane. The number of boronic acid binding sites is controlled by varying the dendrimer content. The electrochemical and spectrophotometric properties of the nanocomposite membrane are investigated using the probe molecule alizarin red S. Pure cellulose membranes inhibit access to the electrode. However, the presence of boronic acid receptor sites allows accumulation of alizarin red S with a Langmuirian binding constant of ca. 6000 1000 M1. The 2-electron 2-proton reduction of immobilized alizarin red S is shown to occur in a ca. 60 nm zone close to the electrode surface. With a boronic acid dendrimer modified nanofibrillar cellulose composition of 96 wt% cellulose and 4 wt% boronic acid dendrimer, the analytical range for alizarin red S in aqueous acetate buffer pH 3 is approximately 10 mM to 1 mM.

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Comparison of pah levels and sources in pine needles from Portugal, Spain, and Greece

(Taylor & Francis Group, 2012) Elefteria Psillaki; Arminda Alves; Damià Barceló; Nuno Ratola; José Manuel Amigo; Sílvia Lacorte

The main objective of this work was to assess and compare the levels, patterns, and sources of contamination of 16 polycyclic aromatic hydrocarbons (PAHs) between Portugal, Spain, and Greece (in the island of Crete). A total of 9 sampling sites were chosen (4 in urban and 5 in non-urban areas) in each country and pine needles from the Pinus pinea L. species were collected. Although the mean total PAH levels was similar in the three countries (279 ± 236 ng g−1 for Portugal, 294 ± 258 ng g−1 for Spain, 301 ± 253 ng g−1 for Greece, all dry weight) and, in general, 3-ring and 4-ring PAHs were predominant (being phenanthrene consistently the most abundant), there were some visible differences in the aromatic ring patterns and possible sources between the three regions. Source apportionment was done using PAH ratios (Phen/Ant and Flt/Pyr crossplots) and reflected mixed petrogenic and pyrogenic sources. Furthermore, Principal Component Analysis (PCA) clearly separated the urban and the non-urban sites and all three countries, which reinforces that the sources of contaminations vary in each case and the suitability of pine needles for trans-boundary biomonitoring of PAHs.

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