Biomedical subjects

Carlo Vandecasteele

Publications and source records attributed to Carlo Vandecasteele.

16 recordsLinked to original sources

PubMed2007

Physico-chemical characterization of nanofiltration membranes.

This study presents a methodology for an in-depth characterization of six representative commercial nanofiltration membranes. Laboratory-made polyethersulfone membranes are included for reference. Besides the physical characterization [molecular weight cut-off (MWCO), surface charge, roughness and hydrophobicity], the membranes are also studied for their chemical composition [attenuated total reflectance Fourier spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)] and porosity [positron annihilation spectroscopy (PAS)]. The chemical characterization indicates that all membranes are composed of at least two different layers. The presence of an additional third layer is proved and studied for membranes with a polyamide top layer. PAS experiments, in combination with FIB (focused ion beam) images, show that these membranes also have a thinner and a less porous skin layer (upper part of the top layer). In the skin layer, two different pore sizes are observed for all commercial membranes: a pore size of 1.25-1.55 angstroms as well as a pore size of 3.20-3.95 angstroms (both depending on the membrane type). Thus, the pore size distribution in nanofiltration membranes is bimodal, in contrast to the generally accepted log-normal distribution. Although the pore sizes are rather similar for all commercial membranes, their pore volume fraction and hence their porosity differ significantly.

Journal Article↗

PubMed2006

Influence of mining activities in the North of Potosi, Bolivia on the water quality of the Chayanta River, and its consequences.

Mining activity in the North of Potosi (Siglo XX mine, Ingenio Catavi-Siglo XX, Pucro mine and Colquechaca mine) produces minewater containing high concentrations of heavy metals such as As (0.02-34 mg/l), Cd (45-11,600 microg/l), Cu (0.35-32 mg/l), Fe (42-1,010 mg/l), Pb(33-3,130 microg/l), Ni(20-4,320 microg/l), and Zn (1.1-485 mg/l), that exceed considerably the limit values. The rivers in the North of Potosi (Katiri and Pongoma) that do not receive minewater contain clear water with rather low heavy metal concentrations. These rivers and also other rivers contaminated with minewater, are tributaries of the Chayanta River that transports water with a high concentration of heavy metals such as As (6-24 microg/l), Cd (260-2,620 microg/l), Cu (205-812 microg/l), Pb(10-21 microg/l) and Ni(110-332 microg/l). These elements result from mining activity, as indicated by a comparison with rivers not contaminated by minewater discharges. Water of the Chayanta River, used all year long by the population of Quila Quila, (a village situated at about 75 km from the mining centers), for the irrigation of crops such as potato, maize and broad bean, contains heavy metal concentrations exceeding for several elements the guidelines for irrigation. As drinking water the population of Quila Quila consumes spring water with a generally acceptable heavy metal concentration, as well as infiltrated water of Chayanta River (which is also used in animal drinking troughs) with a high concentration of Cd (23-63 microg/l), exceeding the limit value for drinking water. The metal concentration is significantly lower in the infiltrated water than in the water of Chayanta River. Some technological solutions are suggested to improve the quality of the water used. Surveys carried out on inhabitants of the region, showed that many people present health problems, probably to be attributed to the bad quality of the water they consume and use for irrigation.

Bolivia↗

PubMed2006

Antimony leaching from uncarbonated and carbonated MSWI bottom ash.

The recycling potential of municipal solid waste incinerator (MSWI) bottom ash may be limited by the leaching of antimony (Sb). Therefore, treatment methodologies need to be developed. The pH-dependent leaching behaviour of this oxyanion-forming element in fresh and weathered bottom ash is, however, not understood. Sb leaching was investigated in a wide range of both pH and extent of carbonation. Sb came close to equilibrium with calcium antimonate (Ca[Sb(OH)(6)](2)) at acid and neutral pH. Therefore, adsorption experiments with synthetic calcite (CaCO(3)), ettringite (Ca(6)Al(2)(SO(4))(3)(OH)(12) x 26H(2)O), gypsum (CaSO(4) x 2H(2)O), and portlandite (Ca(OH)(2)) and adsorption modelling to hydrous ferric oxides (HFO) and amorphous aluminium minerals (AAM) were conducted to investigate which minerals decrease Sb leaching below equilibrium with calcium antimonate. At pH>12, calcium antimonate comes into solution due to portlandite formation, but the subsequent increase in Sb leaching is reduced due to strong interaction of Sb with portlandite and ettringite. Ettringite appears to be an important host mineral for Sb at the natural pH of mildly weathered bottom ash (11.8) because a minimum in leaching is observed. When pH is decreased below 10.5, ettringite dissolves and Sb comes into solution, approaching equilibrium with calcium antimonate near pH 9. Gypsum showed no affinity for Sb. The interaction of calcite with Sb was not clear. Adsorption modelling suggested that HFO, rather than AAM, control Sb leaching when pH<9. During carbonation, Sb leaching first increased, most likely due to dissolution of ettringite. Then, Sb leaching decreased, since the pH became low enough to allow sorption by HFO.

Adsorption↗

PubMed2006

Experimental study and modelling of Cr (VI) removal from wastewater using Lemna minor.

The removal of Cr(VI) from wastewater by Lemna minor was studied both at laboratory and pilot scale. Laboratory tests were conducted under different conditions of initial Cr(VI) concentration (0.5 and 2.0 mg/l) and temperature (285 and 291 K). Batch experiments were carried out during 16 days in which the chromium concentrations, both in the biomass and in wastewater were measured. Data were used to characterize the biouptake capacity of the biomass; results showed that it increases with the temperature and when the initial Cr concentration decreases. The biouptake process could be fitted by an equation, with a correlation coefficient of 0.98. The removal process was assessed using the data of the variation of chromium concentration in the wastewater with respect to time; this allowed obtaining constant parameters which were applied in a mathematical model for the assessment of duckweed systems in a pilot scale plant.

Araceae↗

PubMed2006

Flux decline in nanofiltration due to adsorption of dissolved organic compounds: model prediction of time dependency.

Flux decline during nanofiltration of aqueous solutions containing dissolved organic compounds is mainly caused by adsorption of these compounds in the membrane pores and on the membrane surface. In this paper, flux decline is modeled by incorporating the loss of permeability due to adsorption in the Spiegler-Kedem equation. This results in a logarithmic relation between normalized flux decline and time until the adsorption equilibrium is reached and the flux reaches a constant value. In this way, the expected flux decline due to adsorption of organic compounds can be estimated. Two different parameters were used in the model: the time delay t(0), which corresponds to the time at which the adsorption process in the membrane pores and on the membrane surface sets in, and the corresponding reduction of free (pore) volume (b). Both parameters depend on the hydrophobicity of the compounds and on the feed concentration.

Journal Article↗

PubMed2006

Accurate quantification of PAHs in water in the presence of dissolved humic acids using isotope dilution mass spectrometry.

The effect of dissolved humic acids on the recovery of PAHs from water samples has been investigated using a commercially available humic acid preparation as colloid model and a mixture containing the 16 EPA PAHs. The presence of humic acid reduced the extraction efficiency down to between 10 and 75%. An analytical protocol was therefore developed for the accurate determination of PAHs in the presence of humic acids based on isotope dilution mass spectrometry. The procedure compensates for losses due to sorption of PAHs and can be used for the determination of the total PAH concentration in water, i.e. dissolved PAHs plus PAHs adsorbed on colloids. To obtain reliable estimates it is essential to allow a certain time for equilibration between the isotope spike and the aqueous matrix which may vary between 5 and 24 h, in correlation with the water solubility of PAHs. The protocol allows one to recover the 16 PAHs studied at 94 to 105%. The expanded uncertainty of the measurements was 5-7% for all PAHs. Liquid-liquid extraction and solid-phase extraction in combination with the developed isotope dilution protocol performed equally well for the quantification of PAHs from water samples rich in colloidal material.

Adsorption↗

PubMed2005

Modeling of the adsorption of organic compounds on polymeric nanofiltration membranes in solutions containing two compounds.

The adsorption of organic compounds in aqueous solution on polymeric nanofiltration membranes is studied; this process is one of the most important fouling mechanisms influencing the flux and retention behavior of nanofiltration membranes. It is shown that the adsorption of dissolved organic compounds on polymeric nanofiltration membranes is comparable to that on activated carbon. Freundlich and Langmuir isotherms are used to describe the relation between the adsorbed mass on the membrane and the equilibrium concentration of the organic compound in a single-compound solution. Based on these results, three models for the adsorption of solutions containing several compounds [i.e., the simple competitive adsorption model (SCAM), the model of Jain-Snoeyinck, and the model of Butler-Ockrent] were used to predict the adsorption behavior of an organic compound in an aqueous solution containing two compounds. The results of the three models were compared to experimental observations. It is shown that the SCAM allows a good prediction of the adsorption behavior.

Adsorption↗

PubMed2005

Transport of pure components in pervaporation through a microporous silica membrane.

The pervaporation mechanism of pure components through a commercial microporous silica membrane was studied by performing experiments using water, methanol, ethanol, 2-propanol, and n-propanol in the 40-80 degrees C temperature range. Experimental fluxes were correlated to feed temperature and viscosity. It was found that the permeation mechanism obeys the adsorption-diffusion description, covering both the microscopic models based on configurational (micropore) diffusion and on activated surface diffusion. The contribution of convection was negligible. Size parameters for the permeating molecules such as molecular weight, kinetic diameter, and effective diameter, which are expected to have an influence on diffusion, did not correlate with the flux, thus strongly emphasizing the importance of sorption as the rate-determining step for transport in the pervaporation process. This was confirmed by correlating parameters reflecting polarity with flux: an exponential relation between the Hansen polarity (especially the hydrogen bonding component) and the flux was observed. A similar correlation was found between the dielectric constant and the flux. Furthermore, the flux increases in the same direction as the hydrophilicity of the pure components (log P). The effects of membrane surface tension and contact angles are less outspoken, but experiments performed on glass supported and silica supported membrane top layers suggest an important influence of the sublayers on the flux.

Journal Article↗

PubMed2004

Estimation of the contribution of a municipal waste incinerator to the overall emission and human intake of PCBs in Wilrijk, Flanders.

The contribution of the emission of PCBs by a municipal waste incinerator in Wilrijk, a relatively industrialized district in the largest city of Flanders, to the total emission to air and to the total human intake was estimated. Therefore it was compared to the emission of PCBs by evaporation from PCB containing applications (transformers, capacitors, paint, ink, etc.) and to the intake of PCBs with food. As there was a lack of PCB data from the incinerator, the PCB emission concentration was estimated using three different approaches. A PCB measurement of the incinerator emission, performed later on, fell within the predicted range of 0.0004-0.005 ng TEQ/Nm3. Emission of PCBs from PCB containing applications and intake from food were deduced from information available on Flemish and European level. The results indicate a PCB contribution from the incinerator to local emissions between 0.3% and 3% of the emission from PCB containing applications and a contribution to human intake less than 6 x 10(-4)% of the intake from food.

Air Pollutants↗

PubMed2003

Reuse, treatment, and discharge of the concentrate of pressure-driven membrane processes.

Application of pressure-driven membrane processes (microfiltration, ultrafiltration, nanofiltration, and reverse osmosis) results in the generation of a large concentrated waste stream, the concentrate fraction, as a byproduct of the purification process. Treatment of the concentrate is a major hurdle for the implementation of pressure-driven membrane processes since the concentrate is usually unusable and has to be discharged or further treated. This paper reviews possibilities to treat or discharge the concentrate: (i) reuse, (ii) removal of contaminants, (iii) incineration, (iv) direct or indirect discharge in surface water, (v) direct or indirect discharge in groundwater, and (vi) discharge on a landfill. General guidelines are given for the choice of a proper method as a function of the origin and composition of the water treated. Next, the further treatment of the concentrates in four application areas of pressure-driven membrane processes (drinking water industry, leather industry, and membrane treatment of landfill leachates and of textile process waters) is discussed.

Conservation of Natural Resources↗

PubMed2003

Removal of pollutants from surface water and groundwater by nanofiltration: overview of possible applications in the drinking water industry.

During the last decade, nanofiltration (NF) made a breakthrough in drinking water production for the removal of pollutants. The combination of new standards for drinking water quality and the steady improvement of the nanofiltration process have led to new insights, possible applications and new projects on lab-scale, pilot scale and industrial scale. This paper offers an overview of the applications in the drinking water industry that have already been realised or that are suggested on the basis of lab-scale research. Applications can be found in the treatment of surface water as well as groundwater. The possibility of using NF for the removal of hardness, natural organic material (NOM), micropollutants such as pesticides and VOCs, viruses and bacteria, salinity, nitrates, and arsenic will be discussed. Some of these applications have proven to be reliable and can be considered as known techniques; other applications are still studied on laboratory scale. Modelling is difficult due to effects of fouling and interaction between different components. The current insight in the separation mechanisms will be briefly discussed.

Disinfection↗

PubMed2003

Solid phase speciation of arsenic by sequential extraction in standard reference materials and industrially contaminated soil samples.

Availability, mobility, (phyto)toxicity and potential risk of contaminants is strongly affected by the manner of appearance of elements, the so-called speciation. Operational fractionation methods like sequential extractions have been applied for a long time to determine the solid phase speciation of heavy metals since direct determination of specific chemical compounds can not always be easily achieved. The three-step sequential extraction scheme recommended by the BCR and two extraction schemes based on the phosphorus-like protocol proposed by Manful (1992, Occurrence and Ecochemical Behaviours of Arsenic in a Goldsmelter Impacted Area in Ghana, PhD dissertation, at the RUG) were applied to four standard reference materials (SRM) and to a batch of samples from industrially contaminated sites, heavily contaminated with arsenic and heavy metals. The SRM 2710 (Montana soil) was found to be the most useful reference material for metal (Mn, Cu, Zn, As, Cd and Pb) fractionation using the BCR sequential extraction procedure. Two sequential extraction schemes were developed and compared for arsenic with the aim to establish a better fractionation and recovery rate than the BCR-scheme for this element in the SRM samples. The major part of arsenic was released from the heavily contaminated samples after NaOH-extraction. Inferior extraction variability and recovery in the heavily contaminated samples compared to SRMs could be mainly contributed to subsample heterogeneity.

Arsenic↗

PubMed2003

Development of a sampling train for arsenic in pyrolysis vapours resulting from pyrolysis of arsenic containing wood waste.

In the present study a sampling and analysis method for arsenic emissions during pyrolysis of arsenic containing wood, such as chromated copper arsenate (CCA) treated wood, has been developed. The procedure is based on the NIOSH (National Institute for Occupational Safety and Health) standard for arsenic trioxide sampling. Validation for this specific application is needed since pyrolysis of arsenic containing wood leads to a gas stream containing sticky tar compounds and aerosols. Validation was carried out through tube furnace experiments using both CCA treated wood and arsenic trioxide powder as input. The outlet of the tube furnace was coupled to a cooling section and sampling train. The sampling train consisted of one or more filter sections and impingers. Different combinations of filters (untreated or impregnated) and impingers, as well as different combinations of washing solutions were tested. The different units of the sampling train were analysed by inductively coupled plasma mass spectrometry (ICP-MS) in order to determine the distribution of arsenic over the different units. For the working conditions considered (pyrolysis at 350 degrees C for 20 minutes with a nitrogen flow rate of 100 Nl h(-1)) the combination of a quartz cooling tube and a cellulose ester membrane filter impregnated with a Na2CO3-glycerol solution was sufficient to capture the arsenic. Two extra impingers (the first one containing 50 ml HNO3 1 M in the case of CCA treated wood and 50 ml NaOH 0.1 M in the case of As2O3 and the second one containing 50 ml NaOH 0.1 M) were added downstream of the filter section as backup either in case of filter failure or to check whether all the arsenic released is captured by the cooling tube and filter.

Air Pollutants↗

PubMed2003

Reference materials for the monitoring of the aquatic environment--a review with special emphasis on organic priority pollutants.

During recent years, the awareness of quality assurance and quality control in environmental analyses has constantly increased, especially due to the implementation of new guidelines and regulations at both the national and international level. Achieving comparable results by using certified reference materials is one of the primary concerns of the scientific community. As a result, there is a growing demand for certified reference materials to cover different matrices and pollutants. Moreover, these CRMs should be in close relationship to the determinants and target concentrations required by environmental bodies and European Directives as well. Supplementary information to this paper presents an inventory of reference materials available on the market from different suppliers against the priority pollutants listed in the Water Framework Directive. These CRMs cover matrices such as water, sediment and biota. The use of CRMs in relationship to appropriate analytical methods and relevant determinants is discussed and the need for matrix-CRMs, particularly for organic pollutants is emphasised. The use of proficiency testing schemes as an alternative for the lack of appropriate CRMs and future trends in the production of CRMs within the BCR framework are also discussed.

Certification↗

PubMed2002

Solidification/stabilisation of arsenic bearing fly ash from the metallurgical industry. Immobilisation mechanism of arsenic.

When a fly ash waste material from a copper refining process containing large amounts of As2O3 is solidified using cement and lime, the arsenic concentration in the leachate can be lowered to ca. 5 mg/l in a saturated solution of Ca(OH)2. It is shown that the decrease of the concentration in the leachate, mainly of As(III), is due to the formation of insoluble CaHAsO3 in the leachate in the presence of Ca(OH)2. This method is compared with a method whereby use is made of oxidation of the waste before solidification to oxidise As(III) to As(V) using H2O2. The arsenic concentration in the leachate of the extraction test of an oxidised S/S sample was lowered to ca. 0.5 mg/l, a factor of 10 below the one for a non-oxidised sample. It is shown that the decrease of the concentration in the leachate mainly of As(V) is due to the formation of insoluble Ca3(AsO4)2 in the presence of Ca(OH)2. Extensive use was made of the speciation program MINTEQA2, to clarify the immobilisation of arsenic.

Arsenic↗

PubMed2002

Community shifts in a seeded 3-chlorobenzoate degrading membrane biofilm reactor: indications for involvement of in situ horizontal transfer of the clc-element from inoculum to contaminant bacteria.

Pseudomonas putida BN210, carrying the self- transferable clc-element encoding degradation of 3-chlorobenzoate on the chromosome, was used as inoculum in different membrane biofilm reactors treating 3-chlorobenzoate-contaminated model wastewater. Analysis of the bacterial population in the effluent and in the biofilm showed the loss of BN210 beyond detection from the reactors and the appearance of several novel 3-chlorobenzoate mineralizing bacteria mainly belonging to the beta-proteobacteria. In contrast, in non-inoculated reactors, no 3-chlorobenzoate degradation was observed and no 3-chlorobenzoate degraders could be recovered. Southern blots hybridization of genomic DNA using clc-element-specific probes and FIGE analysis indicated the presence of the complete clc-element in one or more copies in the isolates. Moreover, the isolates could transfer the clc genes to Ralstonia metallidurans recipients. Two representative reactor isolates, Ralstonia sp. strains KP3 and KP9 demonstrated a higher growth rate on 3-chlorobenzoate than strain BN210 in batch cultures. When BN210, KP3 and KP9 were simultaneously inoculated in a membrane reactor supplied with 3-chlorobenzoate, strain KP3 outcompeted the two other strains and remained the major 3-chlorobenzoate degrading population in the reactor. Our data suggest that in situ horizontal transfer of the clc-element from the inoculum to contaminant bacteria in the reactors was involved in the establishment of novel 3-chlorobenzoate degrading populations that were more competitive under the defined reactor conditions than the inoculum strain.

Biodegradation, Environmental↗