Biomedical subjects

F Beolchini

Publications and source records attributed to F Beolchini.

5 recordsLinked to original sources

PubMed2006

Micellar enhanced ultrafiltration for arsenic(V) removal: effect of main operating conditions and dynamic modelling.

In this work arsenic removal by micellar enhanced ultrafiltration (MEUF) was investigated using cetylpyridinium chloride (CPC) in ceramic membrane apparatus. Permeability tests and discontinuous diafiltration tests were performed in different operating conditions to evaluate the effect of membrane pore size (20 and 50 nm), transmembrane pressure, pH, surfactant concentration (1-3 mM), and arsenic concentration (10-40 mg/L) on permeate flux decline, arsenic, and CPC rejections. These preliminary experimental results showed that a ceramic membrane with large pore size allows treament of high fluxes of concentrated arsenic-bearing solutions even by using low surfactant concentrations. Arsenic concentration in the permeate was at the 1 ppm level, with feed As concentrations (10 ppm) that are larger than those generally used in MEUF studies and with CPC amounts that are lower than the usual ones. In addition, operating conditions adopted in these tests obtained CPC concentrations in the permeate always lower than its critical micellar concentration (0.9 mM). Dynamic simulations of discontinuous two-step diafiltration tests allowed a simple and adequate representation of the performance of the process especially for 1 mM CPC, while discrepancies for 2.5 mM CPC level denoted complex interactions between CPC and As.

Arsenic↗

PubMed2005

Ionic strength effect on copper biosorption by Sphaerotilus natans: equilibrium study and dynamic modelling in membrane reactor.

Biosorption of copper by Sphaerotilus natans in different conditions of ionic strength and pH was studied by performing sorption tests in batch and membrane reactors. Equilibrium batch tests evidenced the negative effect of ionic strength and the positive effect of pH on biosorption performances: the highest determined value for copper specific uptake, q, was about 60 mg/g at pH 6 and about 15 mg/g at pH 4. A competitive equilibrium model was successfully fitted to experimental data at different ionic strength levels to account for copper-sodium competition. In membrane reactor tests, experimental profiles of copper concentration in the permeate vs. time did not evidence a significant effect of ionic strength at low pH values (4 and 5). On the other hand a more remarkable effect of ionic strength on copper concentration in the permeate was observed at pH 6. Experimental profiles of continuous biosorption in the membrane reactors were successfully simulated by developing a dynamic model accounting for Cu-Na competition and for binding ability of cells fragments.

Adsorption↗

PubMed2003

Sorption of copper by olive mill residues.

A study on olive mill residues (OMR) as copper adsorbing material is reported in this work. A rough characterization of this waste material has been performed, by microanalysis and SEM pictures. Sorption tests with suspended OMR evidenced copper removal from solution, of about 60% in the investigated experimental conditions. The COD release in solution was also monitored during biosorption. Considering that it was significant, OMR washings with water were performed before biosorption. In this case the COD release in solution was reduced to less than 600 mg/L after two washings, while the OMR metal sorption properties did not change. Regenerated residues by acid solutions gave a copper removal of about 40%, in the same experimental conditions of the first adsorption test: regeneration with EDTA at different concentrations suggested that it presents a damage of adsorption active sites. On the other hand, the use of HCl and CaCl(2) led to completely regenerate the biosorbent material. Tests were also performed with a column filled with 80 g of OMR and the breakpoint was demonstrated to take place after that about 1L solution was treated in the investigated experimental conditions. Regeneration tests permitted to demonstrate that a concentration factor of about 2 can be obtained in no-optimized conditions, highlighting the possibility of using OMR for the treatment of metal bearing effluents. The main advantage of the process would be the "low cost" biosorbing material, considering that it represents a waste in the olive oil production.

Adsorption↗

PubMed2001

Modeling of copper biosorption by Arthrobacter sp. in a UF/MF membrane reactor.

Copper biosorption by Arthrobacter sp. has been studied in this work. The process has been realized inside of a ultrafiltration/microfiltration (UF/MF) reactor in order to confine cells. A mathematical model has been developed that is able to predict experimental data under different operating conditions. The model takes into account different phenomena, which might occur during the process, such as a dependence of equilibrium parameters on pH, a partial cell disruption, and a change in the membrane retention properties at high biomass concentrations. Experimental tests have been performed under different operating conditions: a full factorial design has been implemented with pH (levels: 4, 5, and 6 units) and biomass concentration (levels: 1 and 5 g/L) as factors. A simple mathematical model based on metal mass balance taking into account the effect of pH on the Langmuir equilibrium adsorption parameters well fitted experimental data at low pH values and biomass concentrations. A more complex mathematical model, which considers a partial cell disruption during the biosorption trial, was proposed to understand and analyze the anomalous system behavior at pH = 6 and biomass concentration equal to 5 g/L. The effect of mechanical stress on biomass performances was also examined by using a discontinuous system (test tube trials) simulating the membrane reactor apparatus. In this alternative system biosorption trials were carried out in test tubes in such a way to avoid or at least minimize the disruption due to mechanical stress. Experimental results obtained by using this system can be modeled up to pH = 5 without considering cell disruption phenomenon, while at pH = 6 possible chemical reactions of biomass constituents could happen.

Adsorption↗

PubMed2000

Female gonad of moles, genus Talpa (Insectivora, mammalia): ovary or ovotestis?

The female gonads of moles (genus Talpa) are composed of a cortex, functioning as an ovary, and a medulla, which is structurally similar to that of the testis. In the female reproductive apparatus there are masculine glandular annexes, such as a bilobate prostate, two Cowper glands, and a penis-like clitoris. All these features have recently led to the hypothesis of the presence of hermaphroditism due to sex-reversal in Talpa. The purpose of this study is to understand the functional significance of the structural organization of the female gonads in order to verify this hypothesis. Histological, histochemical and ultrastructural analyses have been carried out on several gonads of both sexes of two species: T. europaea and T. romana, including three fetuses. In both species, the cortical region of the female gonad shows a regular oogenetic activity. While the medulla is composed of interstitial cells that are partly organized in cord-like structures, no spermatogenetic activity has been ever observed inside of them. A histochemical analysis shows that in both sexes the interstitial cells secrete steroids, presumably estrogens as well as androgens. The presence of androgens in the female gonads would therefore explain the persistence of male glandular annexes in the female reproductive apparatus and both the sexual and behavioral monomorphism typical of the genus Talpa. Nonetheless, the female gonad of moles is a real ovary and a well-defined gonochorism exists. Therefore, there is no reason to assert the presence of hermaphroditism due to sex reversal.

Androgens↗