Hydroxytyrosol Enrichment of Olive Leaf Extracts via Membrane Separation Processes.

Antioxidants isolated from plant materials, such as phenolics, have attracted a lot of attention because of their potential uses. This contributes to the idea of the biorefinery, which is a way to produce useful products from biomass waste. Olea europaea byproducts have been extensively investigated for their large contents in phenolics. Oleuropein is a phenolic compound abundant in olive leaves, with its molecule containing hydroxytyrosol, elenolic acid, and glucose. In this work, olive leaf extracts were treated using different combinations of ultrafiltration and nanofiltration membranes to assess their capacity of facilitating the production of hydroxytyrosol-enriched solutions, either by separating the initially extracted oleuropein or by separating the hydroxytyrosol produced after a hydrolysis step. The best performance was observed when an ultrafiltration membrane (UP010, 10,000 Da) was followed by a nanofiltration membrane (TS40, 200-300 Da) for the treatment of the hydrolyzed extract, increasing the purity of the final product from 25% w/w of the total extracted compounds being hydroxytyrosol when membrane processes were not used to 68% w/w.

Impact of Microbial Uptake on the Nutrient Plume around Marine Organic Particles: High-Resolution Numerical Analysis.

The interactions between marine bacteria and particulate matter play a pivotal role in the biogeochemical cycles of carbon and associated inorganic elements in the oceans. Eutrophic plumes typically form around nutrient-releasing particles and host intense bacterial activities. However, the potential of bacteria to reshape the nutrient plumes remains largely unexplored. We present a high-resolution numerical analysis for the impacts of nutrient uptake by free-living bacteria on the pattern of dissolution around slow-moving particles. At the single-particle level, the nutrient field is parameterized by the Péclet and Damköhler numbers (0 < Pe < 1000, 0 < Da < 10) that quantify the relative contribution of advection, diffusion and uptake to nutrient transport. In spite of reducing the extent of the nutrient plume in the wake of the particle, bacterial uptake enhances the rates of particle dissolution and nutrient depletion. These effects are amplified when the uptake timescale is shorter than the plume lifetime (Pe/Da < 100, Da > 0.0001), while otherwise they are suppressed by advection or diffusion. Our analysis suggests that the quenching of eutrophic plumes is significant for individual phytoplankton cells, as well as marine aggregates with sizes ranging from 0.1 mm to 10 mm and sinking velocities up to 40 m per day. This microscale process has a large potential impact on microbial growth dynamics and nutrient cycling in marine ecosystems.

High-Yield Production of a Rich-in-Hydroxytyrosol Extract from Olive (Olea europaea) Leaves.

The aim of the present study was to explore the high-yield production of hydroxytyrosol, a phenolic compound with very high antioxidant capacity. Olea europaea leaves were chosen as feedstock as they contain significant amounts of oleuropein, which can be hydrolyzed to hydroxytyrosol. The chosen techniques are widely used in the industry and can be easily scaled up. Olive leaves underwent drying and mechanical pretreatment and extractives were transported to a solvent by solid-liquid extraction using water-ethanol mixtures. The use of approximately 60-80% ethanol showed an almost 2-fold increase in extracted phenolics compared to pure water, to approximately 45 g/kg of dry leaves. Extracted oleuropein was hydrolyzed with hydrochloric acid and the hydrolysate was extracted with ethyl acetate after pH adjustment. This step led to a hydroxytorosol content increase from less than 4% to approximately 60% w/w of dry extract, or 10-15 g of hydroxytyrosol recovery per kg of dry leaves.

Recovery of Water from Secondary Effluent through Pilot Scale Ultrafiltration Membranes: Implementation at Patras' Wastewater Treatment Plant.

Fresh water shortages affect larger areas each year due to the increased human population combined with climate change. Reuse of treated sewage water (mostly for nonpotable uses) can have a significant impact on reducing water scarcity. Ultrafiltration membranes are widely considered as a very good candidate for the remediation of this type of water. The case of Patras' sewage treatment plant was examined for the treatment of its secondary settling tank effluent using a pilot ultrafiltration unit to produce permeate water suitable for reuse according to Greek legislation. The physicochemical characteristics of the membrane permeate stream showed significant improvements in the quality of the produced water. Turbidity was reduced by 99%, total suspended solids were decreased by more than 94%, while COD was reduced by 37%. E. coli and Enterococcus were detected at high concentrations in the feed stream but were eliminated in the membrane permeate. The results presented herein indicate that the installed equipment is capable of producing improved quality water suitable for reuse even with the strictest limits imposed by Greek legislation.

Treatment of Two-Phase Olive Mill Wastewater and Recovery of Phenolic Compounds Using Membrane Technology.

The semi-solid wastes (pomace or alperujo) produced in the two-phase olive oil extraction process contains extremely high organic load and phenolic substances. Efficient treatment of such kinds of wastes using membrane filtration, should be sought to reduce the hazardous effects to the environment. On the other hand, phenolic compounds can be isolated and purified up to a level of commercial exploitation using the membrane technology. Firstly, the extraction process with mixtures of water and ethanol was optimized by testing extraction parameters (e.g., solvent's mixture, duration, and temperature) at laboratory scale. Next, extraction was conducted using larger volumes and the treatment was continued in a pilot membrane filtration system, consisted of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. The extracted solution from the olive oil pomace was fed to the pilot membrane filtration system, where all fat, lipids, and solids were removed while the phenolic compounds were concentrated in the retentate streams of NF and/or RO. Total phenolic content (TPC) at the RO's concentrate stream was 225 mg/L and at the final effluent was lower than 10 mg/lt. The chemical oxygen demand (COD) value at the final effluent was much lower (~280 mg/L) than in the feed stream (>32,000 mg/L).

Theoretical Insight into the Biodegradation of Solitary Oil Microdroplets Moving through a Water Column.

In the aftermath of oil spills in the sea, clouds of droplets drift into the seawater column and are carried away by sea currents. The fate of the drifting droplets is determined by natural attenuation processes, mainly dissolution into the seawater and biodegradation by oil-degrading microbial communities. Specifically, microbes have developed three fundamental strategies for accessing and assimilating oily substrates. Depending on their affinity for the oily phase and ability to proliferate in multicellular structures, microbes might either attach to the oil surface and directly uptake compounds from the oily phase, or grow suspended in the aqueous phase consuming solubilized oil, or form three-dimensional biofilms over the oil-water interface. In this work, a compound particle model that accounts for all three microbial strategies is developed for the biodegradation of solitary oil microdroplets moving through a water column. Under a set of educated hypotheses, the hydrodynamics and solute transport problems are amenable to analytical solutions and a closed-form correlation is established for the overall dissolution rate as a function of the Thiele modulus, the Biot number and other key parameters. Moreover, two coupled ordinary differential equations are formulated for the evolution of the particle size and used to investigate the impact of the dissolution and biodegradation processes on the droplet shrinking rate.

Isolation of organic compounds with high added values from agro-industrial solid wastes.

Phenols are organic compounds with high antioxidant activity. Occurring mainly in plants, where they act as pigments or even as part of defense mechanisms against insects and herbivores. Given the positive impact on on human health, their isolation and purification from agricultural products is of particular interest for the production of nutritional, pharmaceutical and cosmetics supplements. In our study different materials rich in phenolic compounds were used, in order to separate the phenolic content and maximum condensation using physicochemical methods such as solvent extraction, filtration through membranes, adsorption/desorption on resins and vacuum distillation. The materials tested were solid wastes from winery, cocoa residuals, olive leaves, etc. The first step for the treatment was the extraction of phenolic content using water-ethanol solutions which was initially optimized. Then, sequential membrane filtration of the extracts by Ultrafiltration membranes, Nanofiltration and Reverse Osmosis was performed to separate the contained compounds, based on their molecular weight. To remove non-polar compounds, with similar molecular weights with phenols, methods of adsorption/desorption on specific resins were developed, in order final ethanolic solutions rich in phenolic compounds to be obtained. Finally, the ethanol was removed by vacuum evaporation at low temperatures. The purification of olive leaf phenols is illustrated in details in the present work. The final obtained concentrate, was a rich phenolic concentrate and contained 98 g/L phenols in gallic acid equivalents. This technique, after modification, can be applied to a variety of phenol-rich byproducts, allowing the operation of phenol separation plant adjustable to local agricultural activities.

Purification of olive mill wastewater phenols through membrane filtration and resin adsorption/desorption.

Olive tree cultivation has a long history in the Mediterranean countries, and even today consists an important cultural, economic, and environmental aspect of the area. The production of olive oil through 3-phase extraction systems, leads to the co-production of large quantities of olive mill wastewater (OMW), with toxic compounds that inhibit its biodegradation. Membrane filtration has been used for the exploitation of this byproduct, through the isolation of valuable phenolic compounds. In the current work, a fraction of the waste occurring from a membrane process was used. More specifically the reverse osmosis concentrate, after a nanofiltration, containing the low-molecular-weight compounds, was further treated with resin adsorption/desorption. The non ionic XAD4, XAD16, and XAD7HP resins were implemented, for the recovery of phenols and their separation from carbohydrates. The recovered phenolic compounds were concentrated through vacuum evaporation reaching a final concentration of 378 g/L in gallic acid equivalents containing 84.8 g/L hydroxytyrosol.

Membrane filtration of agro-industrial wastewaters and isolation of organic compounds with high added values.

The aim of the current study was the exploitation of agro-industrial wastes or by-products such as olive mill wastewater (OMW) and defective wines. A cost-effective system for their maximum exploitation is suggested, using a combined process of membrane filtration and other physicochemical processes. Wastewaters are first treated in a membrane system (prefiltration, ultrafiltration, nanofiltration, and reverse osmosis) where pure water and other organic fractions (by-products) are obtained. Organic fractions, called hereafter byproducts and not wastes, are further treated for the separation of organic compounds and isolation of high added value products. Experiments were performed with OMW and defective wines as characteristic agro-industrial wastewaters. Profit from the exploitation of agro-industrial wastewaters can readily help the depreciation of the indeed high cost process of membrane filtration. The simple phenolic fraction of the OMW was successfully isolated from the rest of the waste, and problems occurring during winemaking, such as high volatile acidity and odours, were tackled.

Valorization of solid waste products from olive oil industry as potential adsorbents for water pollution control--a review.

The global olive oil production for 2010 is estimated to be 2,881,500 metric tons. The European Union countries produce 78.5% of the total olive oil, which stands for an average production of 2,136,000 tons. The worldwide consumption of olive oil increased of 78% between 1990 and 2010. The increase in olive oil production implies a proportional increase in olive mill wastes. As a consequence of such increasing trend, olive mills are facing severe environmental problems due to lack of feasible and/or cost-effective solutions to olive-mill waste management. Therefore, immediate attention is required to find a proper way of management to deal with olive mill waste materials in order to minimize environmental pollution and associated health risks. One of the interesting uses of solid wastes generated from olive mills is to convert them as inexpensive adsorbents for water pollution control. In this review paper, an extensive list of adsorbents (prepared by utilizing different types of olive mill solid waste materials) from vast literature has been compiled, and their adsorption capacities for various aquatic pollutants removal are presented. Different physicochemical methods that have been used to convert olive mill solid wastes into efficient adsorbents have also been discussed. Characterization of olive-based adsorbents and adsorption mechanisms of various aquatic pollutants on these developed olive-based adsorbents have also been discussed in detail. Conclusions have been drawn from the literature reviewed, and suggestions for future research are proposed.

Sand consolidation with calcium phosphate-polyelectrolyte composites.

A new method for the consolidation of loose sand formations has been developed. The method involves in situ precipitation of a composite calcium phosphate-polyelectrolyte salt that binds together with loose sand grains, thus resulting to their consolidation. Three different polyelectrolytes (PE) were tested, i.e., polyacrylic acid (PAA), polyallylamine hydrochloride (PAH), and polyethylenimine (PEI). The effect of PE tested on the thermodynamics and the kinetics of precipitation of calcium phosphate salts was investigated. Three types of experiments were done. Investigation of the adsorption of PE on either hydroxyapatite (Ca(5)(PO(4))(3)OH, HAP) crystals or on sand grains. Measurement of the kinetics of heterogeneous nucleation of HAP on the solid substrates and the mechanical properties of the obtained crystals in batch experiments of low and high supersaturation solutions, respectively. Evaluation of the consolidation in sand packs in order to investigate the effectiveness of the method. The crystallization rates, R(p), on HAP crystals in the presence of the PE tested were found in the order R(p)(PAA)>R(p)(PEI)>R(p)(PAH), while nucleation and crystal growth on silicate sand took place only in the absence of adsorbed PE. PAH favored strongly the consolidation process, whereas PEI and PAA resulted in the formation of poorly consolidated grain agglomerates.

Adsorption of atrazine from aqueous electrolyte solutions on humic acid and silica.

The adsorption of, the still widely used, herbicide atrazine on model soil components, such as humic acid and humic acid-silica gel mixtures, was investigated in a series of batch experiments, under different experimental conditions (ionic strength, temperature, and pH). The investigation aimed at obtaining an estimate of the contribution of each of the soil components on the adsorption of atrazine from aqueous solutions. The kinetics of atrazine adsorption on humic acid showed two steps: a fast step, of a few hours duration, and a second slow step, which continued for weeks. The kinetics of adsorption data gave a satisfactory fit to the Elovich equation. Τhe adsorption of atrazine on the test substrates was found to be reversible in all cases. The atrazine uptake data on the test substrates were fitted best with the Freundlich adsorption isotherm. The ionic strength of the atrazine aqueous solutions did affect the amount of the atrazine adsorbed on the test substrates, suggesting that electrostatic forces between atrazine molecules and soil play a significant role in the adsorption process. An increase of temperature resulted in a decrease of atrazine adsorption on humic acid at low atrazine equilibrium concentrations. However, for higher levels of equilibrium concentrations (≥3 mg/L) the amount of atrazine adsorbed onto the test substrate increased as temperature increased. The calculated isosteric enthalpies of adsorption ranged between slightly exothermic at low atrazine uptake and slightly endothermic at high atrazine uptake, all values being in the range of physisorption.

Computational representation and hemodynamic characterization of in vivo acquired severe stenotic renal artery geometries using turbulence modeling.

The present study reports on computational fluid dynamics in the case of severe renal artery stenosis (RAS). An anatomically realistic model of a renal artery was reconstructed from CT scans, and used to conduct CFD simulations of blood flow across RAS. The recently developed shear stress transport (SST) turbulence model was pivotally applied in the simulation of blood flow in the region of interest. Blood flow was studied in vivo under the presence of RAS and subsequently in simulated cases before the development of RAS, and after endovascular stent implantation. The pressure gradients in the RAS case were many orders of magnitude larger than in the healthy case. The presence of RAS increased flow resistance, which led to considerably lower blood flow rates. A simulated stent in place of the RAS decreased the flow resistance at levels proportional to, and even lower than, the simulated healthy case without the RAS. The wall shear stresses, differential pressure profiles, and net forces exerted on the surface of the atherosclerotic plaque at peak pulse were shown to be of relevant high distinctiveness, so as to be considered potential indicators of hemodynamically significant RAS.

Heterogeneous nucleation and growth of calcium carbonate on calcite and quartz.

The precipitation of calcium carbonate as a binding salt for the consolidation of loose sand formations is a promising approach. The heterogeneous nucleation and growth of calcite were investigated in supersaturated solutions. The ionic activities in the solutions tested were selected so that they included both supersaturations in which crystal growth took place only following the introduction of seed particles and supersaturations in which precipitation occurred spontaneously past the lapse of induction times. In the latter case the supersaturation conditions were sufficiently low to allow the measurement of induction times preceding the onset of precipitation. The stability domain of the calcium carbonate system was established at pH 8.50, 25 degrees C, measuring the induction times in the range between 30 min and 2 h. The rates of precipitation following the destabilization of the solutions were measured from the pH and/or concentration-time profiles. The induction times were inversely proportional and rates proportional to the solution supersaturation as expected. The high-order dependence of the rates of precipitation on the solution supersaturation suggested a polynuclear growth mechanism. Fitting of the induction time-supersaturation data according to this model yielded a value of 64 mJ/m2 for the surface energy of the calcite nucleus. In the concentration domain corresponding to stable supersaturated solutions, seeded growth experiments at constant supersaturation showed a second-order dependence on the rates of crystal growth of calcite seed crystals. Inoculation of the stable supersaturated solutions with quartz seed crystals failed to induce nucleation. Raising supersaturation to reach the unstable domain showed interesting features: calcite seed crystals yielded crystal growth kinetics compatible with the polynuclear growth model, without any induction time. The presence of quartz seed crystals reduced the induction times and resulted in nucleation in the bulk solution. The kinetic data in the latter case were consistent with the polynuclear growth model and the surface energy for the newly forming embryo was calculated equal to 31.1 mJ/m2, because of the dominantly heterogeneous nature of the process.

Calcium sulfate precipitation in the presence of water-soluble polymers.

The effect of four different polymers on the precipitation of calcium sulfate was investigated in the present work. The degree of inhibition was estimated from measurements of the calcium ion activity and from specific solution conductivity measurements in the supersaturated solutions during the course of the precipitation process. The effects of polyacrylic acid (PAA, three different polymers with average molecular weight 2000, 50,000, and 240,000, respectively) and of a co-polymer of PAA with polystyrene sulfonic acid (PSA, average molecular weight<20,000) were investigated with respect to their effect on the kinetics of spontaneous precipitation of calcium sulfate salts. The results of the kinetics experiments suggested that the spontaneous precipitation from supersaturated calcium sulfate solutions at 25 degrees C yielded exclusively calcium sulfate dihydrate (gypsum) both in the absence and in the presence of the polymeric additives. The induction times, preceding the formation of the solid increased in all cases in the presence of the polymeric additives. Polymer concentrations as low as 2.0 ppm increased induction time from practically zero to 10 min. The rates of precipitation were reduced according to the solutions content in the polymers added and precipitation was completely suppressed in the presence of 6.0 ppm of the polymers tested, depending on their molecular weight. The lower the molecular weight of PAA, the more efficient was the threshold inhibition and the stronger the reduction of the rates of spontaneous precipitation. PSA yielded the poorest inhibition efficiency in comparison with the PAA, possibly because of the relatively lower affinity of the sulfonate groups for the calcium ions of the surface of the solid forming. The kinetics results analysis assuming Langmuir-type adsorption of the polymeric molecules on the growing supercritical gypsum nuclei showed different affinity for the polymers tested in agreement with the respective inhibition efficiency, in the order: PAA1>PAA2>PSA>PAA3. The presence of the polymers in the supersaturated solutions resulted in modification of the precipitated gypsum crystals morphology.

Adsorption of atrazine on soils: model study.

The adsorption of the widely used herbicide atrazine onto three model inorganic soil components (silica gel, gamma-alumina, and calcite (CaCO(3)) was investigated in a series of batch experiments in which the aqueous phase equilibrated with the solid, under different solution conditions. Atrazine did not show discernible adsorption on gamma-alumina (theta=25 degrees C, 3.8