Extraction of Cellulose from Ulva lactuca Algae and Its Use for Membrane Synthesis

Green algae are a sustainable source of biopolymers for the global demand due to their high photosynthetic efficiency. This article describes the extraction of cellulose from plant systems represented by Ulva lactuca species. In order to extract various substances, algae were finely ground with the help of solvents (liquid media). This was carried out to achieve the necessary conditions that help reduce the resistance this phase shows in regard to the transport and transfer of the species being extracted. The highest yield of extracted cellulose (20,944%) was obtained for the following factors: S/L = 1/20; conc. ethanol = 90%, conc. salts = 4 g/L. Hydrogel membranes are a unique class of macromolecular networks that contain a large fraction of aqueous solvent within their structure. With the cellulose extracted from algae, we obtained membranes which underwent the process of swelling in liquid media (ethyl alcohol) of different concentrations. The swelling of biocellulose membranes in alcoholic solutions of high concentrations was investigated. It was observed that the process of absorption of the alcoholic solution by the membrane occurred rapidly in the first part. After stabilization, the membranes continued to absorb at a slower rate until stabilization or saturation concentration was reached.

Full factorial design and dynamic modelling of silent and ultrasound-assisted lead and cadmium removal by porous biosorbent

Present work aimed to analyse single and competitive lead and cadmium batch adsorption, using experimental studies and mathematical modelling. The experiments were conducted in silent and ultrasound-assisted systems, in aqueous environment, using grinded hazelnut shells as porous biosorbent. The influence of process factors (pH, adsorbent concentration, adsorbent particle size, and initial species concentration in liquid phase) on species removal efficiency was evaluated when process equilibrium was attained. The statistical study, following a 2⁴ factorial experimental design, allowed the development of a model to predict variables influence. Based on the obtained results a deeper analysis of the separation efficiency, depending on process factors, was conducted. The dynamic study was performed based on experimentally obtained removal rates, modelled considering species diffusion, with reversible kinetics of sorption inside solid particles. Hence, the dynamics of removal efficiency was determined for several representative experiments. The equilibrium isotherms data, best fitted by an appropriate Langmuir model, were used in the dynamic model to reduce the number of model parameters which normally require experimental identification.

Heavy Metalspatial Distribution and Pollution Assessment in the Surface Sediments of the North � Western Black Sea Shelf

22 surface sediment samples were collected in August 2018 from the Romanian inner shelf (Nord-Western Black Sea). Concentrations of some metals (Al, Cr, Cu, Ni, Zn, As, Pb, and Hg), TOC content, and grain size of sediment samples were determined by specific techniques. The order of accumulation of heavy metals was Zn]Cr]Ni]Cu]Pb]As]Hg. Multivariate analysis indicated that As, Ni, Cu, Zn, Pb, and Hg concentrations had similar behavior and they were positively correlated with the clay content, whereas Al and Cr concentrations presented close patterns and they were negatively correlated with the water depth. Sediment pollution assessment indices (enrichment factor, contamination factor, and geo-accumulation index) suggested no/low pollution for most of the metals analyzed, excepting for Pb and Hg (moderate pollution). Values of pollution indices highlighted a higher sediment pollution with Pb and Hg along the Danube�s plume direction, in the oil platform area (eastern edge of the Portita Bay), and partially in the Constanta and Mangalia area, suggesting the influence of port activities, tourism, urban wastewater discharges, oil and gas extraction.

Natural Wool for Removal of Oil Spills from Water Surface

Romanian Merino wool was tested as a natural sorbent for oil spill cleanup. Rebco crude oil placed in distilled water was used as an oily water model. Experiments of batch sorption were performed under various conditions. The effects of process factors, i.e., initial density of packed bed sorbent (0.05-0.99 g/cm3), initial volume ratio of oil and water (0.25 and 0.14 cm3/cm3), and contact surface between adsorbent and oily water, on wool sorption capacity (6.4-11.8 g/g) were evaluated. Experimental data were fitted using pseudo-first order rate and pseudo-second order rate models.

Extraction and Characterization of Alginate from an Edible Brown Seaweed (Cystoseira barbata) Harvested in the Romanian Black Sea

Cystoseira barbata is an edible brown seaweed, traditionally used in the Black Sea area as functional food. Both alginate and brown seaweed biomass are well known for their potential use as adsorbents for heavy metals. Alginate was extracted from C. barbata recovered from the Romanian coast on the Black Sea with a yield of 19 ± 1.5% (w/w). The structural data for the polysaccharide was obtained by HPSEC-MALS, 1H-NMR. The M/G ratio was determined to be 0.64 with a molecular weight of 126.6 kDa with an intrinsic viscosity of 406.2 mL/g. Alginate beads were used and their adsorption capacity with respect to Pb2+ and Cu2+ ions was determined. The adsorption kinetics of C. barbata dry biomass was evaluated and it was shown to have an adsorption capacity of 279.2 ± 7.5 mg/g with respect to Pb2+, and 69.3 ± 2 with respect to Cu2+. Alginate in the form of beads adsorbs a maximum of 454 ± 4.7 mg/g of Pb2+ ions and 107.3 ± 1.7 mg/g of Cu2+ ions.

Romanian Merino Wool Sorbent for Oil Spill Cleanup

Removal of some pollutants (Basra, Azeri, and Rebco crude oils, diesel, gasoline, and 1/1 (w/w) diesel-gasoline mixture) from water by sorption using Romanian Merino wool as a natural sorbent was studied in this paper. Batch experiments were conducted at different levels of initial sorbent mass (1 and 3 g), oily water pH (5 and 10), and operating temperature (30 and 45 �C). The effects of these factors on wool sorption capacity were evaluated. The sorption capacity of more viscous fuels (crude oils), i.e., 4.13-21.87 g/g, increased with an increase in oily water pH and a decrease in initial sorbent mass and temperature. For less viscous pollutants (diesel, gasoline, and their mixture), the sorption capacity (3.32-9.19 g/g) increased with a decrease in sorbent mass, the effects of pH and temperature being negligible. Experimental results were processed according to a 2 3 factorial plan and regression equations between the process factors and sorption capacity were obtained. SEM analysis revealed that the removal process was governed by both adsorption and absorption mechanisms.

Study on Alumina Supported Heterogeneous Catalysts for Biodiesel Production

In this work four heterogeneous catalysts were studied first by preparing a gama-alumina catalytic support then by impregnating with acidic and base compounds to gain certain properties needed to catalyze vegetable oils conversion to biodiesel. The resulted new catalytic properties allowed us to simultaneously conduct esterification and transesterification reaction in a single step when waste cooking oils with a high free fatty acid content were converted to biodiesel. The prepared catalysts were thermally and chemically stable and exhibited good catalytic activity when tested in (trans)esterification reactions to yield biodiesel. The effects of catalyst loading, methanol/oil molar ratio and reaction time on biodiesel yield along with catalyst reusability were investigated. The highest biodiesel yield reached was 88.10% at 65oC reaction temperature, 15:1 methanol/oil molar ratio, 5% catalyst loading and 4 h reaction time.

Experimental and Modelling of Aqueous Radioactive Waste Treatment by Ultrafiltration

Ultrafiltration of untreated and pretreated aqueous radioactive wastes was conducted using a spiral-wound polysulphonamide membrane. The influence of process factors on its performances was experimental studied and predicted. Permeate volumetric flux and permeate total suspended solids (TSS) were measured at different values of feed flow rate (7 and 10 m3/h), operating pressure (0.1-0.4 MPa), and feed TSS (15 and 60 mg/L). Permeate flux (42-200 L/(m2�h)) increased with feed flow rate and operating pressure as well as it decreased with an increase in feed TSS, whereas permeate TSS (0.1-33.2 mg/L) exhibited an opposite trend. A 23 factorial plan was used to establish correlations between dependent and independent variables of ultrafiltration process.

Fresh Ulva Lactuca Alcoholic Fermentation Products and yields

The optimization of the ethanol yield obtained by alcoholic fermentation of fresh Ulva lactuca in the presence of cellulase and Saccharomyces cerevisiae yeast was performed. Three main factors affecting the process were considered: the solid-to-liquid ratio (S), cellulase-to-algal biomass ratio (R), expressed as cellulase units (U) per gram of dry matter (DM), and the alcoholic fermentation temperature (t). The optimal parameters were: S=1/24 g/g, R=16 U/ g DM and t=35�C, when alcohol yield was 0.34 g/100 g fresh alga, within the range of other authors� experimental data. Over 200 compounds were identified in the distillate from the fermentation broth, recommending Ulva lactuca as a sustainable source of drugs, intermediates for biosyntheses and biomaterials. The yield of these compounds was 5.92 g/100 g fresh alga, in the same conditions. The yields of ethanol (0.013-0.023 g/g DM) and volatile compounds (0.199-0.398 g/g DM) were predicted depending on the process factors using regression equations obtained by ANOVA analysis of experimental data.

Slow Pyrolysis of Cystoseira Barbata Brown Macroalgae

Slow pyrolysis of algal biomass of Cystoseira barbata was performed in a fixed bed reactor using carbon dioxide as a sweeping gas and a reactant in the process. Pyrolysis products consisted of a biochar, a bio-oil, and pyrolytic gases. According to a 23 factorial experiment, 8 tests were conducted for 1 hr at two levels of each process factor, i.e., specific heat flow rate (7540, 9215 W/m3), carbon dioxide superficial velocity (1.3, 2.6 cm/s), and bulk density of fixed bed biomass (221, 332 kg/m3). Correlations between these factors and final process responses in terms of mean bed temperature (461-663 oC), biochar yield (15.2-26.7%), bio-oil yield (29.9-34.8%), and BET surface area of biochar (45.17-91.12 m2/g) were established.

Modelling of Ethanol Fermentation Coupled with Product Recovery by Pervaporation

Bioethanol is the most important biofuel produced by fermentation of sugars from various biomass types. The main disadvantages associated to this process consist in the negative effect of high ethanol concentration on the cell growth and in the separation cost of ethanol-water system resulted in the fermentation process. Sugar fermentation using Saccharomyces cerevisiae yeast coupled with bioethanol recovery by pervaporation has been modeled and simulated in this paper. In order to avoid the clogging of pervaporation membrane, the yeast cells were previously retained into an ultrafiltration unit. Three operating modes were analyzed and compared, i.e., classical batch fermentation (BF), batch fermentation coupled with external ultrafiltration and pervaporation (BFPV), and fed batch fermentation coupled with external ultrafiltration and pervaporation (FBFPV). Surface areas of ultrafiltration and pervaporation units were selected as process control variables.

Effects of Process Factors on Carbon Dioxide Reforming of Methane over Ni/SBA-15 Catalyst

The process of CO2 reformation of CH4 was conducted over a 5% Ni/SBA-15 catalyst under various experimental conditions. Operating temperature (600-750 �C), gas hourly space velocity (4000-12000 hr-1), and CO2/CH4 feed molar ratio (0.67-1.50) were selected as independent parameters (factors). Process performances were evaluated as conversions of CH4 (21.1-79.6%) and CO2 (42.4-98.7%) as well as H2/CO product molar ratio (0.573-0.992). All process performances were enhanced at higher levels of temperature and low values of gas velocity. An increase in feed molar ratio has determined a significant increase in CH4 conversion and a slighter decrease in CO2 conversion and H2/CO molar ratio. A statistical model based on a 23 factorial plan was used to predict the process performances depending on its factors.

Rheological Characterization of Algal Suspensions for Bioethanol Processing

The paper has aimed at studying the rheology of macroalgae aqueous suspensions in the presence of cellulase enzyme relevant to bioethanol processing by a subsequent fermentation. Rheological measurements of aqueous suspensions of Ceramium virgatum and Cladophora vagabunda macroalgae species were performed using a Couette geometry rotational viscosimeter. The effects of operation temperature (t=25, 50 �C), cellulase/dried algae ratio (R=0, 16 U/mgda), and algal suspension mass concentration (c=5-15%) on rheological behaviour and parameters were evaluated. Algal suspensions behaved as non-Newtonian fluids obeying either a Bingham plastic linear relationship or an Ostwald-de Waele power law corresponding to a pseudoplastic fluid. Characteristic dynamic viscosity of Bingham plastic fluids were in the range 0.045-0.115 Pa�s for C. virgatum suspensions and 0.021-0.114 Pa�s for C. vagabunda ones, whereas apparent viscosity varied from 0.138 Pa�s to 43.551 Pa�s for C. virgatum and from 0.181 Pa�s to 45.417 Pa�s for C. vagabunda. Data obtained in 8 rheological tests corresponding to a Bingham plastic behaviour of C. vagabunda suspensions, which were processed according to a 23 factorial experiment, emphasized an increase in suspension viscosity with all process factors. The results could be useful for optimization of enzymatic hydrolysis process in order to develop efficient and cost effective saccharification and fermentation strategies.

Effect of Process Factors on Pervaporation Dehydration of Isopropanol

The paper aimed at studying the performances of pervaporation separation of isopropanol-water system using a Pervatech ceramic membrane at various values of feed mixture flow rate (F=1000 kg/hr), feed water mass fraction (xF=0.1-0.2), operation temperature (t=60-90 �C), permeate pressure (pP=1000-9000 Pa) and water separation degree (sW=0.9, 0.95). Membrane total flux and separation factor were predicted applying a second order response surface model with 3 factors, i.e., xF, t and pP. An algorithm for estimating the membrane surface area was presented. Membrane area increased with sW and xF and its lowest values (A=13 m2 for xF=0.1 and A=24 m2 for xF=0.2) were attained for t=60 �C and pP=9000 Pa. These findings could be applied for optimizing the process of isopropanol dehydration by pervaporation.

Ultrasound influence upon calcium carbonate precipitation on bacterial cellulose membranes

The effect of ultrasonic irradiation (40 kHz) on the calcium carbonate deposition on bacterial cellulose membranes was investigated using calcium chloride (CaCl(2)) and sodium carbonate (Na(2)CO(3)) as starting reactants. The composite materials containing bacterial cellulose-calcium carbonate were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and color measurements. The polymorphs of calcium carbonate that were deposited on bacterial cellulose membranes in the presence or in the absence of ultrasonic irradiation were calcite and vaterite. The morphology of the obtained crystals was influenced by the concentration of starting solutions and by the presence of ultrasonic irradiation. In the presence of ultrasonic irradiation the obtained crystals were bigger and in a larger variety of shapes than in the absence of ultrasounds: from cubes of calcite to spherical and flower-like vaterite particles. Bacterial cellulose could be a good matrix for obtaining different types of calcium carbonate crystals.

Researches Concerning the Intake of Carbon Dioxide Resulted from the Fossil Carbon Burning

The research by modelling has been particularized at the case of removal of carbon dioxide from hot burning gases. The gases washing with specific solution in mobile packed bed expresses the basic of proposed removal procedure of carbon dioxide. A large assembly of differential equations give the mathematical model of the considered procedure. The given simulations show that the carbon dioxide and sulphur dioxide removal occurs with high intensities depending of the concentration level of the liquid active species.

Factors Influence on Bacterial Cellulose Growth in Static Reactors

Synthesis of bacterial cellulose by Acetobacter xylinum in static conditions was performed. In order to optimize the cultivation conditions a factorial experiment with four factors (operating temperature, substrate concentration, co-substrate concentration and air specific flow rate) and two levels was used. Correlations between cellulose yield, respectively added water specific use, and process factors were established.

On the Corrosion of Spent Fuel Aluminium Cladding During Wet Storage

The paper presents the results obtained from the curves curent-potential when Al-Mg3 samples polarization occurs in solutions that simulate the water from the storage pool. The samples used in research are characteristic for the fuel spent C-36 and EK-10 and also for the storage pool from the Magurele- Romania research reactor deactivation. The study is unique due to the material samples used and due to the fact that the results of electrochemical experiments are correlated to the results from the chemical analysis of water samples from spent fuel storage basins. The paper is in the class of those which serve to the estimation of the dynamics of the degradation of spent fuel cladding during wet storage.