Static Experimental Conditions Research Articles

Micro-column testing of the dynamic adsorption of Pb by Fe-Mg clay–quartz beds

AbstractClays have been used widely as sorbents of potentially toxic elements, especially Pb. However, their adsorption efficiency has been studied mostly under static experimental conditions, which are labour-intensive. In this study, dynamic adsorption experiments were established using micro-columns to assess the adsorption behaviour of natural Fe-Mg-rich clays for Pb ions by varying the inlet solution pH, Pb concentration and flow rate. The clays, consisting of varying amounts of palygorskite and Fe-smectite, were diluted with quartz (Qz) sand to enhance their permeability. Greater adsorption capacity was observed for the mixed palygorskite/Fe-smectite-rich clay beds (45.2 ± 0.01 mg g–1) followed by the Fe-smectite-rich (35.7 ± 0.07 mg g–1) and palygorskite-rich (20.0 ± 0.03 mg g–1) clay beds. The results indicated that the greater adsorption efficiency of palygorskite/Fe-smectite-rich clays could be attributed to synergistic effects due to the coexistence of palygorskite and Fe-smectite clay phases, which have distinct physicochemical characteristics. Moreover, the results obtained showed good agreement with the static experiments, implying that the use of micro-columns could describe adsorption adequately over shorter experimental times.

Critical surface density of zwitterionic polymer chains affect antifouling properties

Membrane technologies play an increasingly important role in producing clean drinking water. There is a great interest to design an optimal membrane surface with low-cost compound, simplicity and efficiently production. Importantly, an optimal membrane surfaces requires better permeate and prolong the membrane performance. Herein, we design distinct poly(zwitterion) modifications and investigate the effect of polymer density on the efficiency of the antifouling properties. We present combination of molecular modeling tools and experimental techniques for characterizing the effect of grafting density on antifouling properties and for providing insights into the molecular mechanisms of the antifouling process. Our results suggest that antifouling property in poly(zwitterion) is flux depended. Under dynamic flow conditions, high-density surfaces presented better antifouling performance compared with low-density surfaces by providing robust hydration layer that reduced the foulant adsorption. However, in static experimental conditions the extraction of the foulant from low-density surfaces is more favored because the poly(zwitterion) chains more fluctuate compared to high-density surfaces, thus produce less electrostatic interactions with the foulants.

Biotransformation of Ferulic acid to Vanillin by the fungus, Schizophyllum commune Fr.

The abundant and readily available precursor Ferulic acid (4-hydroxy-3-methoxycinnamic acid) was utilized to evaluate the biotransformation potential of S. commune in catabolizing the precursor Ferulic acid, Ferulic acid metabolism is expected to occur via. propanoic chain degradation to form Vanillic acid which was further metabolized to Protocatechuic aldehyde (3,4-dihydroxybenzaldehyde) via. Protocatechuic acid (3, 4-dihydroxybenzoic acid) or by reductive pathway forming Vanillin (4-hydroxy-3- methoxybenzaldehyde) The percentage of biotransformation was found to be 93 in production of Vanillic acid (4-hydroxy-3- methoxybenzoic acid) from Ferulic acid for biomass of 0.025gms (fresh weight) at a concentration of 02.5mM Ferulic acid in 50ml. Minimal media, at 370 C, pH (6.0) and an incubation period of 10 days. The presence of Vanillin is detected. along with Protocatechuic acid. Vanillin accumulation was found to be in remarkable amounts when Vanillic acid was fed as sole carbon source. Vanillic acid is an intermediate metabolite of Ferulic acid and immediate precursor of Vanillin. The potential of the fungus to convert Vanillic acid (10.0mM) concentration was explored and an yield of 4.5gl-1 was found on 12th day of incubation. Formation of Protocatechuic acid alone from Ferulic acid was noticed at pH (8.0) under static experimental conditions. This indicates that S. commune follows an entirely novel path of catabolism in alkaline conditions in comparison to acidic environment.

Assessment of the Possibilities for the Use of Selected Waste in Terms of Biogas Yield and Further Use of Its Digestate in Agriculture.

The utilization of municipal waste and sewage sludge as a source of energy is technically very difficult due to high variability of their physical and chemical properties. The aim of this study was to evaluate the efficiency of the conversion of biomass contained in the whitewater fraction of municipal waste and sewage sludge by means of methanogenesis. The second objective was to assess the chemical composition of the digestate in the context of its use for fertilizer purposes. The whitewater fraction of municipal waste and sewage sludge was subjected to methanogenesis under static experimental conditions, according to DIM DIN 38414 methodology. The methanogenesis of concentrated substrates used in agricultural biogas plants was taken as a reference to evaluate the efficiency of the process. The organic fraction of the municipal waste was characterized by approximately 30% lower value of the soluble COD, with a comparable level of total COD compared to other materials. The total biogas yield, i.e., 404 dm3 per 1 kg of dry weight of the batch, was measured in the facility with sewage sludge. In COD value, this is 0.232 dm3·g O2 COD. In the case of corn, these values were, respectively, 324 dm3 and 0.193, and for the organic sub-sieve fraction of municipal waste, 287 dm3·kg−1 dw or 0.178 dm3·g O2 COD, respectively. The type of fermented material did not affect the intensity of biogas production. The maximum level of biogas production occurred between the 13th and 15th day of the process. The digestate obtained in the process of methanogenesis of corn silage and the organic fraction of municipal waste was characterized by good parameters in terms of possible use for fertilization purposes.

Use of Lignite as a Low-Cost Material for Cadmium and Copper Removal from Aqueous Solutions: Assessment of Adsorption Characteristics and Exploration of Involved Mechanisms

Lignite, as an available and low-cost material, was tested for cadmium (Cd) and copper (Cu) removal from aqueous solutions under various static experimental conditions. Experimental results showed that the removal efficiency of both metals was improved by increasing their initial concentrations, adsorbent dosage and aqueous pH values. The adsorption kinetic was very rapid for Cd since about 78% of the totally adsorbed amounts were removed after a contact time of only 1 min. For Cd and Cu, the kinetic and isothermal data were well fitted with pseudo-second order and Freundlich models, respectively, which suggests that Cd/Cu removal by lignite occurs heterogeneously on multilayers surfaces. The maximum Langmuir’s adsorption capacities of Cd and Cu were assessed to 38.0 and 21.4 mg g−1 and are relatively important compared to some other lignites and raw natural materials. Results of proximate, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) showed that the removal of these metals occurs most likely through a combination of cation exchange and complexation with specific functional groups. The relatively high adsorption capacity of the used lignite promotes its future use as a low cost material for Cd and Cu removal from effluents, and possibly for other heavy metals or groups of pollutants.

Researches regarding the static and dynamic behaviour of composites with natural reinforcements

In this paper, some composite materials were built in this way: the reinforcement is made with natural fibers (there were used two types of natural fibers in this way: hemp and cotton) and the matrix is made from epoxy resin. The Resoltech 1050 epoxy resin is used, with its Resoltech 1050 hardener. The casting was made at room temperature and the matrix was applied using the brush. The static experimental conditions are characterized by tensile loading of the build specimens and the determination of statically Young modulus. There was used an Instron Universal testing machine and the force-extension curves were obtained. The dynamic parameters were determined from the bars free vibrations. The next experimental montage was used: the bars were clamped at one end and were left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms−2 sensitivity was placed in order to record the beams dynamic response. A force was applied at the free end to bend the beams and after bending, the force was cancelled and the beams were left to freely vibrate. The accelerometer was connected to a signal conditioner Nexus and the signal conditioner was connected to a data acquisition system SPIDER 8 made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook and the experimental parameters were obtained through CATMAN EASY software. From the free vibrations recording, the next mechanical parameters were determined: the eigenfrequency of the first eigenmode, the damping factors per unit mass and per unit length, the loss factor and the dynamic Young modulus.

Mechanical properties determination for a hybrid sandwich bar reinforced with steel wire mesh

In this paper, some new original hybrid sandwich beams were built in this way: the core is made with polypropylene honeycomb and the reinforcement is made with steel wire mesh. The connection between the reinforcement and the core was made with epoxy resin. The aim of this study is to create a beam from classic materials but combined in a way to obtain a new and original structure. The static experimental conditions are characterized by bending loading of the beams and the determination of statically stiffness. The dynamic parameters were determined from the beams free vibrations. The next experimental montage was used: the beams were clamped at one end and were left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms−2 sensitivity was placed. A force was applied at the free end to bend the beams and after bending, the force was cancelled and the beams were left to freely vibrate. From the free vibrations recording, the next mechanical parameters were determined: the eigenfrequency of the first eigenmode, the damping factors per unit mass and per unit length, the loss factor, the dynamic stiffness and the dynamic Young modulus.

New insights into bacterial cellulose materials: production and modification strategies

Komagataeibacter xylinus cultures produced high amount of bacterial cellulose (BC), which has a structure of nanoporous network of interlaced fibers. When the culture is performed under static experimental conditions, a membrane with characteristics of highly hydrated hydrogel and good mechanical properties is obtained with promissory applications in the biomedical field. Bacterial cellulose films can be used from dermal dressing and even as a controlled drug release system. Besides, stirred cultures of K. xylinus produced amorphous cellulose structures dispersed in the medium with physical and mechanical characteristics different from the membrane. In addition, new properties of BC can be obtained or added if the hydrogel is mixed with other compounds or modified post-purification using both organic and inorganic compounds.

Natural active molecule chemical grafting on the surface of microfibrillated cellulose for fabrication of contact active antimicrobial surfaces

In this work, a naturally occurring phenyl isothiocyanate (PITC) molecule was covalently bonded to the surface of microfibrillated cellulose (MFC) to prepare contact active antimicrobial surfaces based on presently used materials. A preliminary comparative study was carried out on the reactivity of the hydroxyl group of cellulose and lignin compounds with phenyl isothiocyanate. Classical second order reaction kinetics was established between the hydroxyl containing model alcohol compounds and phenyl isothiocyanate with the conversion up to 80% in 20min. X-ray diffraction and scanning electron microscopy (SEM) were utilized to monitor the change in crystallinity and morphology of the surface after grafting. Further, the successful immobilization of isothiocyanate was confirmed after grafting with contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and presence of sulfur by elemental analysis. Antibacterial activity was investigated against gram positive bacteria, Staphylococcus aureus and Bacillus subtilis, in dynamic and static experimental conditions. The PITC grafted MFC did not exhibit a bactericidal activity in dynamic condition, however, a very strong activity (complete killing) was revealed under static condition with 3.5 log initial CFU. These findings may help in the establishment of new and safe strategy for the preparation of antimicrobial contact surfaces for packaging applications.

A perfusion bioreactor system efficiently generates cell-loaded bone substitute materials for addressing critical size bone defects.

Critical size bone defects and non‐union fractions are still challenging to treat. Cell‐loaded bone substitutes have shown improved bone ingrowth and bone formation. However, a lack of methods for homogenously colonizing scaffolds limits the maximum volume of bone grafts. Additionally, therapy robustness is impaired by heterogeneous cell populations after graft generation. Our aim was to establish a technology for generating grafts with a size of 10.5 mm in diameter and 25 mm of height, and thus for grafts suited for treatment of critical size bone defects. Therefore, a novel tailor‐made bioreactor system was developed, allowing standardized flow conditions in a porous poly(L‐lactide‐co‐caprolactone) material. Scaffolds were seeded with primary human mesenchymal stem cells derived from four different donors. In contrast to static experimental conditions, homogenous cell distributions were accomplished under dynamic culture. Additionally, culture in the bioreactor system allowed the induction of osteogenic lineage commitment after one week of culture without addition of soluble factors. This was demonstrated by quantitative analysis of calcification and gene expression markers related to osteogenic lineage. In conclusion, the novel bioreactor technology allows efficient and standardized conditions for generating bone substitutes that are suitable for the treatment of critical size defects in humans.

Cross-correlations between low-γ nuclei in solids via a common dipolar bath

Correlation of chemical shifts of low-γ nuclei (such as 15N) is an important method for assignment of resonances in uniformly-labeled biological solids. Under static experimental conditions, an efficient mixing of low-γ nuclear spin magnetization can be achieved by a thermal contact to the common reservoir of dipole–dipole interactions in order to create 15N– 15N, 13C– 13C, or 15N– 13C cross-peaks in a 2D correlation spectrum. A thermodynamic approach can be used to understand the mechanism of magnetization mixing in various 2D correlation pulse sequences. This mechanism is suppressed under magic-angle spinning, when mixing via direct cross-polarization with protons becomes more efficient. Experimental results are presented for single-crystalline and powder samples of 15N-labeled N-acetyl- l- 15N-valyl- l- 15N-leucine (NAVL). In addition to the thermodynamic analysis of mixing pulse sequences, two different new mixing sequences utilizing adiabatic pulses are also experimentally demonstrated.

Barnacle Larvae of Megabalanus coccopoma (Darwin, 1854) as a Toxicity Test Organisms

In Brazil, Marine Ecotoxicology is a retelatively new science with few species routinely used in toxicity tests. Barnacle larvae (Naupliu) have been used for different research groups in the world as test organisms with a variety of methods and applications. These organisms have the advantages of easy obtainment in the field, availability throughout the year and easy manipulation in the lab. The use of these organisms in Brazil is still limited to tests of the activity of anticrustant substances and few work has been done to investigate their sensitivity as test-organisms in Ecotoxicology. This work presents a standard operating procedure to perform toxicity tests with naupliu of the barnacle Megabalanus coccopoma one of the biggest examplers of the subordem Balanomorpha and of great distribution around the Brazilian coast. The sensitivity of naupliu II to Zinc (Zn) was evaluted through mobility and mortality endpoints. Nauplius of the M. coccopoma were obtained from egged lamels of adults and used in 48 hours toxicity tests to assess the effect of zinc sulphate in static experimental conditions; poorly mobile and dead organisms were quantified every 12 hours. On the mobility tests, the EC50 of 0.24 mg L–1 (Zn) was obtained following 24 hours expousure; whilst the LC50 of 0.27 and 0.22 mg L–1 (Zn) were obtained following 36 and 48 hours of exposure, respectively. Significant differences were not observed between the EC50 and LC50 values for zinc therefore allowing the development of 24 h mobility and 48 h mortality tests. The EC50; 24 h and LC50; 48 h for zinc demonstrate similar sensitivity between the studied species the mysids Mysidopsis juniae and the copepod Acartia lilljeborgi.

Mathematical model of static platelet adhesion on a solid surface.

The scheme of platelet/surface interaction and a kinetic model of platelet adhesion on a solid surface are suggested. The elaborated approach takes into account the platelet activation by the surface and accumulation of free activated cells in the bulk of the liquid phase. This effect has an especially important role in static experimental conditions. The suggested model explains three types of adhesion kinetic curves, obtained in experiments in vitro: sigmoid curves with or without saturation and an exponential curve with saturation. According to the model, the curve shape is determined by material surface properties, platelet functionality, and experimental conditions of the platelet/surface interaction. The data of static platelet adhesion from platelet rich plasma on glass, siliconized glass, hexadecyltrichlorosilane monolayers, and low-density polyethylene are described mathematically with the proposed model. Numerical parameters are calculated from approximation of experimental data by the model. These parameters allow quantitative characterization of platelet interaction with the material surface.

Photochemical Smog Systems: Heterogeneous Decay of Ozone

Fox et al. (1) describe the results of two experiments from which they conclude that dilution as opposed to static experimental conditions may prove to be more important if smog chamber data are to be used as guides in developing certain future control strategies. Although the above suggestion may be correct, the evidence presented by Fox et al. (1) is incomplete in at least one serious aspect.