Effect of wet milling on the adsorption capacity of a greek natural zeolite used for the removal of heavy metals from solutions

Ο στόχος της παρούσης εργασίας είναι η διερεύνηση της επίδρασης της λειοτρίβισης στην προσροφητική ικανότητα ενός ελληνικού φυσικού ζεόλιθου ως προς την απομάκρυνση ιόντων βαρέων μετάλλων από υδατικά διαλύματα. Ο απώτερος στόχος είναι να μελετηθεί η δυνατότητα παραγωγής και χρήσης υπέρλεπτου ζεόλιθου σε βιομηχανικές και περιβαλλοντικές εφαρμογές. Για τον σκοπό αυτό, φυσικός ζεόλιθος πλούσιος σε κλινοπτιλόλιθο υποβλήθηκε σε υγρή λειοτρίβιση σε ραβδόμυλο ώστε να προκύψουν τρία κοκκομετρικά κλάσματα (<10 μm, 10-63 μm, and 63-200 μm). Η ορυκτολογία των κλασμάτων προσδιορίστηκε με την μέθοδο της Περιθλασιμετρίας Ακτίνων-Χ (XRD) και της Φασματοσκοπίας Φθορισμού Ακτίνων-Χ (XRF), ενώ η κατανομή του μεγέθους των κόκκων και η ειδική τους επιφάνεια με την τεχνική της Περίθλασης Ακτίνας Laser και την μέθοδο BET αντίστοιχα. Η προσρόφηση των ιόντων Cu2+, Ni2+, Mn2+ και Cd2+ από κάθε κοκκομετρικό κλάσμα ζεολίθου μελετήθηκε χρησιμοποιώντας διαφορετικές αρχικές συγκεντρώσεις ιόντων (10 και 100 mg/L) και χρόνους παραμονής (έως 72 ώρες). Η συγκέντρωση του ροφητή διατηρήθηκε σταθερή (5 g/L), ενώ δεν έλαβε χώρα ρύθμιση του pH. Τα πειραματικά αποτελέσματα απέδειξαν ότι με υγρή λειοτρίβιση μπορεί να παραχθεί εξαιρετικά λεπτομερής ζεόλιθος (d50= 4.37 μm) χωρίς απώλεια κρυσταλλικότητας και ότι αυτό το κλάσμα παρουσιάζει εξαιρετική ικανότητα προσρόφησης ιόντων βαρέων μετάλλων. Η διεργασία της προσρόφησης περιγράφεται πολύ καλά από την ισόθερμη Freundlich.The aim of the present work is the investigation of the effect of wet milling on the adsorption capacity of a Greek natural zeolite to remove heavy metal ions from solutions. The ultimate objective is to explore the potential of producing and using fine- grained zeolite in industrial and environmental applications. For this, a rich in clinoptilolite natural zeolite, was subjected to wet milling and 3 fractions were obtained (<10 μm, 10-63 μm, and 63-200 μm). The mineralogy of each fraction was determined through powder XRD and XRF analyses, while their particle size distribution and specific surface area were determined using the Laser Beam Diffraction Technique and the BET method respectively. The adsorption of Cu2+, Ni2+, Mn2+ and Cd2+ ions by each zeolite fraction was investigated using different initial metal ion concentrations (10 and 100 mg/L) and contact times (up to 72 h). The concentration of the adsorbent was kept constant (5 g/L), whereas no pH adjustment took place. The experimental results proved that wet grinding can result in the production of very fine natural zeolite (d50= 4.37 μm) without any loss of crystallinity and that this fraction exhibits substantial metal ion adsorption capacity. Adsorption is best described by the Freundlich isotherm

Epidemiology of intra-abdominal infection and sepsis in critically ill patients: “AbSeS”, a multinational observational cohort study and ESICM Trials Group Project

Purpose: To describe the epidemiology of intra-abdominal infection in an international cohort of ICU patients according to a new system that classifies cases according to setting of infection acquisition (community-acquired, early onset hospital-acquired, and late-onset hospital-acquired), anatomical disruption (absent or present with localized or diffuse peritonitis), and severity of disease expression (infection, sepsis, and septic shock). Methods: We performed a multicenter (n = 309), observational, epidemiological study including adult ICU patients diagnosed with intra-abdominal infection. Risk factors for mortality were assessed by logistic regression analysis. Results: The cohort included 2621 patients. Setting of infection acquisition was community-acquired in 31.6%, early onset hospital-acquired in 25%, and late-onset hospital-acquired in 43.4% of patients. Overall prevalence of antimicrobial resistance was 26.3% and difficult-to-treat resistant Gram-negative bacteria 4.3%, with great variation according to geographic region. No difference in prevalence of antimicrobial resistance was observed according to setting of infection acquisition. Overall mortality was 29.1%. Independent risk factors for mortality included late-onset hospital-acquired infection, diffuse peritonitis, sepsis, septic shock, older age, malnutrition, liver failure, congestive heart failure, antimicrobial resistance (either methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase-producing Gram-negative bacteria, or carbapenem-resistant Gram-negative bacteria) and source control failure evidenced by either the need for surgical revision or persistent inflammation. Conclusion: This multinational, heterogeneous cohort of ICU patients with intra-abdominal infection revealed that setting of infection acquisition, anatomical disruption, and severity of disease expression are disease-specific phenotypic characteristics associated with outcome, irrespective of the type of infection. Antimicrobial resistance is equally common in community-acquired as in hospital-acquired infection

Investigation of adsorption of the dyestuff astrazon red violet 3rn (basic violet 16) on montmorillonite clay

In this study, color removal by absorption from synthetically prepared wastewater was investigated using montmorillonite clay by adsorption. As dyestuff Astrazon Red Violet 3RN (Basic Violet 16) was used. Experimental parameters selected were pH, temperature, agitation speed, initial dyestuff concentration, adsorbent dosage and ionic strength. It was established that adsorption rate increased with increasing pH, temperature, dye concentration and agitation speed, but decreased with increased ionic strength and adsorbent dosage. Adsorption equilibrium data obtained by a series of experiments carried out in a water bath were employed with common isotherm equations such as Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich. It was found that the Langmuir equation appears to fit the equilibrium data better than the other models. Furthermore, the fit of the kinetic data to common kinetic models such as the pseudo-first-order, second-order, Elovich and intraparticle diffusion models was tested to elucidate the adsorption mechanism. Kinetic data conformed to the pseudo-second-order model, indicating chemisorptions. In addition, the thermodynamic parameters activation energy, Ea, enthalpy ΔH*, entropy, ΔS*, and free energy change, ΔG*, were calculated. The values of the calculated parameters indicated that physical adsorption of ARV on the clay was dominant and that the adsorption process was endothermic

Effect of wet milling on the adsorption capacity of a greek natural zeolite used for the removal of heavy metals from solutions

The aim of the present work is the investigation of the effect of wet milling on the adsorption capacity of a Greek natural zeolite to remove heavy metal ions from solutions. The ultimate objective is to explore the potential of producing and using fine- grained zeolite in industrial and environmental applications. For this, a rich in clinoptilolite natural zeolite, was subjected to wet milling and 3 fractions were obtained (&lt;10 μm, 10-63 μm, and 63-200 μm). The mineralogy of each fraction was determined through powder XRD and XRF analyses, while their particle size distribution and specific surface area were determined using the Laser Beam Diffraction Technique and the BET method respectively. The adsorption of Cu2+, Ni2+, Mn2+ and Cd2+ ions by each zeolite fraction was investigated using different initial metal ion concentrations (10 and 100 mg/L) and contact times (up to 72 h). The concentration of the adsorbent was kept constant (5 g/L), whereas no pH adjustment took place. The experimental results proved that wet grinding can result in the production of very fine natural zeolite (d50= 4.37 μm) without any loss of crystallinity and that this fraction exhibits substantial metal ion adsorption capacity. Adsorption is best described by the Freundlich isotherm.</jats:p

Complex electrical conductivity measurements of a KTB amphibolite sample at elevated temperatures

In the present work, complex electrical conductivity measurements in the frequency range of 10 mHz–1 MHz and at elevated temperatures (423 K–1373 K) were carried out in amphibolite sample, originating from the KTB drilling. Impedance Cole–Cole plots were used to discriminate the contributions of grain interior, grain boundaries and electrode polarization effects to the measured conductivity spectra. At frequencies above 10 Hz where the electrode effects are negligible, ac-conductivity exhibits frequency dispersion according to a two-term power law behaviour, in most cases of the isothermal spectra. A conductivity relaxation step is observed during heating of the sample up to 773 K, which is attributed to strongly bound water, either in the form of hydroxyls in the crystal lattice of grains, or in the form of molecules trapped between the grain boundaries. The hysteresis plot of dc-conductivity shows an anomalous behaviour at around 1000 K during the heating procedure, due to the dehydroxylation of the sample. The electric modulus M* representation provides additional information over the low temperature range and the conductivity relaxation times were estimated for a limited temperature range. Thermal activation energies of Arrhenius type vary from 0.58 eV up to 1.50 eV, and they are ascribed to proton conduction at low temperature and hopping conduction of small polarons at higher temperatures

Accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas

Purpose:To investigate in vitro the accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas.Methods:Experimental study included 20 freshly enucleated porcine eyes. Epithelium was debrided, and eyes were divided in four groups. Groups were immersed in 35%, 40%, 50%, and 60% glycerin solutions for 3 hours. Subsequently, globes were mounted in a special holder, and their intraocular pressure was hydrostatically adjusted. Intraocular pressure was measured by means of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL while adjusting true intraocular pressure to 17, 33, and 50 mm Hg. Ultrasound pachymetry was performed.Results:Mean corneal thickness was 914.5 ± 33.3 μm (730–1015 μm). In true intraocular pressure of 33 mm Hg, Goldmann applanation tonometry and dynamic contour tonometry significantly underestimated true intraocular pressure (mean Goldmann applanation tonometry: 14.7 ± 4.8 mm Hg, p &lt; 0.001, mean dynamic contour tonometry: 21.6 ± 6.8, p &lt; 0.001). Tono-Pen XL also underestimated, but difference was not statistically significant (Tono-Pen XL: 27.9 ± 9.7, p = 0.064). In true intraocular pressure of 50 mm Hg, all three methods significantly underestimated (Goldmann applanation tonometry: 17.6 ± 5.3 mm Hg, p &lt; 0.001, dynamic contour tonometry: 26.8 ± 6.3 mm Hg, p &lt; 0.001, Tono-Pen XL: 35.6 ± 8.4 mm Hg, p &lt; 0.001). The error in measured intraocular pressure for each method (true minus measured intraocular pressure) was significantly correlated to true intraocular pressure ( p &lt; 0.001). The intraocular pressure measurements of each eye taken under true intraocular pressure of 17 and 33 mm Hg with the three methods were correlated to each other. Measurements taken under intraocular pressure of 50 mmHg were not correlated to each other. Corneal thickness was not correlated to intraocular pressure measurement.Conclusion:Goldmann applanation tonometry, dynamic contour tonometry, and Tono-Pen XL underestimate intraocular pressure when measured under edematous conditions. Tono-Pen XL showed better accuracy, especially in lower true intraocular pressure. The measurement error increases when true intraocular pressure increases in all three methods.</jats:sec

Discovery of two novel laccase-like multicopper oxidases from Pleurotus citrinopileatus and their application in phenolic oligomer synthesis

Background: Laccases and laccase-like multicopper oxidases (LMCOs) oxidize a vast array of phenolic compounds and amines, releasing water as a byproduct. Their low substrate specificity is responsible for their tremendous biotechnological interest, since they have been used for numerous applications. However, the laccases characterized so far correspond to only a small fraction of the laccase genes identified in fungal genomes. Therefore, the knowledge regarding the biochemistry and physiological role of minor laccase-like isoforms is still limited. Results: In the present work, we describe the isolation, purification and characterization of two novel LMCOs, PcLac1 and PcLac2, from Pleurotus citrinopileatus. Both LMCOs were purified with ion-exchange chromatographic methods. PcLac2 was found to oxidize a broader substrate range than PcLac1, but both LMCOs showed similar formal potentials, lower than those reported previously for laccases from white-rot fungi. Proteomic analysis of both proteins revealed their similarity with other well-characterized laccases from Pleurotus strains. Both LMCOs were applied to the oxidation of ferulic and sinapic acid, yielding oligomers with possible antioxidant activity. Conclusions: Overall, the findings of the present work can offer new insights regarding the biochemistry and variability of low-redox potential laccases of fungal origin. Low-redox potential biocatalysts could offer higher substrate selectivity than their high-redox counterparts, and thus, they could be of applied value in the field of biocatalysis