Membrane Entrance Research Articles

Surgical landmarks for identification and preservation of the internal branch of the superior laryngeal nerve

To determine the topographical anatomic features of the internal branch of the superior laryngeal nerve (ibSLN) at the thyrohyoid membrane entrance area in relation to certain consistent anatomical structures. METHODS: Twenty-two fresh adult head cadavers (9 male, 13 female; age range 52-95years) with no signs of abnormality in the neck were dissected to determine the anatomic relationship of ibSLN and superior border of thyroid cartilage, thyroid notch, carotid bifurcation, hyoid corpus, and hyoid greater cornu. The topographical relationship between ibSLN and superior border of thyroid cartilage, thyroid notch, carotid bifurcation, hyoid corpus, and hyoid greater cornu was identified bilaterally in all cadavers. According to the measures, danger zone and safe zone areas for surgical could be predicted and for surgical manipulations as well. We provided the surgical anatomy and important landmarks for determining the internal branch of superior laryngeal nerve in the thyrohyoid membrane entrance region to avoid surgical damage during surgeries of this region.

Comparison of analytical film theory and a numerical model for predicting concentration polarisation in membrane gas separation

Accurate prediction of the concentration polarisation (CP) effect is very important in the design of an efficient membrane-based gas separation process. This study analyses the reliability of analytical film theory (FT) for evaluating the performance of gas separation membranes in terms of CP and flux. The analytical model is compared against a more rigorous numerical model developed by using Computational Fluid Dynamics (CFD) for various operating variables. The results show that the FT prediction is less accurate at high CP conditions when gas permeation through the membrane increases, due to higher permeance selectivity and pressure ratio. Hence, the results suggest that FT is not recommended for membranes with high permeance or high-pressure conditions. Given that the typical range of feed composition and temperature has little impact on fluid properties (i.e., gas diffusion coefficient, densities, and viscosities), the resulting CP does not vary much and hence both FT and CFD models predict a similar CP. The analysis also suggests that the FT model is more accurate in predicting CP in the region closer to the membrane entrance. Overall, the analytical film theory serves as a reliable approximation in membrane gas applications under low CP at high crossflow and low flux conditions.

Non-equilibrium molecular dynamics simulations of water transport through plate- and hourglass-shaped CNTs in the presence of pressure difference and electric field

In the present work, the water transport dynamics and properties within CNT membranes are studied under the effect of pressure and electric field, using non-equilibrium molecular dynamics (NEMD) simulations. To reduce the pressure loss at the entrance and exit regions, the pore mouth shape has been changed to an hourglass shape for CNT membranes of (6,6), (8,8) and (12,12), inspired by aquaporins, which are capable of high water permeation. It is shown that as the pressure difference increases, the water flux enhancement due to change of pore mouth from plate to hourglass increases rapidly. Furthermore, it is found that the hourglass-shaped geometry has the highest impact on the reduction of entrance resistance within the pores with a smaller diameter. By applying an axial electric field at the entrance of the hourglass-shaped CNT membrane, the enhancement in water flux could be further improved. Interestingly, our results show that applying an electric field at the membrane entrance can cause two opposing effects on the water molecules transport: reduction of water molecules steric crowding at the entrance and increasing the average hydrogen bond numbers of the water molecules entering the tube. It seems that the former effect is dominant for low-intensity electric fields.

Molecular Dynamics Simulations of Membrane Permeability.

This Review illustrates the evaluation of permeability of lipid membranes from molecular dynamics (MD) simulation primarily using water and oxygen as examples. Membrane entrance, translocation, and exit of these simple permeants (one hydrophilic and one hydrophobic) can be simulated by conventional MD, and permeabilities can be evaluated directly by Fick's First Law, transition rates, and a global Bayesian analysis of the inhomogeneous solubility-diffusion model. The assorted results, many of which are applicable to simulations of nonbiological membranes, highlight the limitations of the homogeneous solubility diffusion model; support the utility of inhomogeneous solubility diffusion and compartmental models; underscore the need for comparison with experiment for both simple solvent systems (such as water/hexadecane) and well-characterized membranes; and demonstrate the need for microsecond simulations for even simple permeants like water and oxygen. Undulations, subdiffusion, fractional viscosity dependence, periodic boundary conditions, and recent developments in the field are also discussed. Last, while enhanced sampling methods and increasingly sophisticated treatments of diffusion add substantially to the repertoire of simulation-based approaches, they do not address directly the critical need for force fields with polarizability and multipoles, and constant pH methods.

Desalination using modified configuration of supported liquid membrane with enhancement of mass transfer of NaCl.

Supported liquid membranes (SLM) suffer from very slow mass transfer of the solute from the donor phase (DP) to the receptor phase (RP) through the liquid membrane (LM). In the present work, an attempt was made to accelerate the mass transfer in SLM by creating a modified configuration in which the DP and RP are made to flow either co- or counter-currently to each other. Variables, which could affect the removal of NaCl, were the volume ratio of DP to RP, type and quantity of sequestering agent (SA), presence of mobile carrier (MC), type of LM, and flow rate of DP and RP. The results showed that the higher the flow rate of DP and RP, the higher the mass transfer of NaCl. Quantity and type of SA and type of LM were prime important factors. Remarkably, the time required for transfer of NaCl from DP to RP was reduced from several hours in the case of stagnant SLM to several minutes in the present work. The mass transfer of NaCl was analysed based on kinetic laws of two consecutive irreversible first-order reactions. The values achieved establish the process is diffusion controlled, and the membrane entrance rate constants increase directly with initial concentration (Ci) and inversely with quantity of SA.

Characteristics and formation mechanism of membrane fouling in a full-scale RO wastewater reclamation process: Membrane autopsy and fouling characterization

Membrane fouling is the bottleneck of stable operations for reverse osmosis (RO), which is the key technology for reclaimed water reuse in thermal power plants. The foulant composition, formation mechanism, and key contributors were analyzed in this study. The primary scaling substances are Ca, Mg, Al, Fe, and Si, and Ca accounts for 1.49 wt%. Humic substances, proteins, and polysaccharides are the primary organic constitutes, and among them bio-derivatives were main composition revealed by FTIR, EEM, and SEC. Thus, bio-fouling was believed to be the key contributor together with the results of the SEM and the microbial community analysis. The three leading bacteria were α-, β-, γ-proteobacteria at class levels, 38.11%, 14.19%, and 34.31%, respectively, while starkeya, acidovorax, luteimonas, and pseudoxanthomonas were the leading bacteria at the genus level. Among these bacteria, the one with metabolic processes related to nitrogen fixation and proteolysis showed higher abundance for the high concentrations of nitrogen and protein. Foulants on the endcap and membrane entrance also indicated severe bio-fouling, where Acidovorax presented significant abundance. A Vertical distribution of the microbial community was found in the cross-section of the foulant, in particular, a significant decrease of starkeya (from 48.4% to 4.65%) and acidovorax (from 17.64% to 5.61%) and an increase of pseudoxanthomonas (from 1.04% to 12.89%) from the top layer to the bottom layer were observed. The γ-proteobacteria was recognized as the pioneering bacteria for its significantly higher abundance in the deeper layer. This study helps to elucidate the RO membrane fouling composition and its key contributors, and improves our understanding of the membrane fouling mechanism and a controlling strategy.

Synthesis and in Vitro Evaluation of Monodisperse Amino-Functional Polyester Dendrimers with Rapid Degradability and Antibacterial Properties

Amine functional polymers, especially cationically charged, are interesting biomacromolecules for several reasons, including easy cell membrane entrance, their ability to escape endosomes through the proton sponge effect, spontaneous complexation and delivery of drugs and siRNA, and simple functionalization in aqueous solutions. Dendrimers, a subclass of precision polymers, are monodisperse and exhibit a large and exact number of peripheral end groups in relation to their size and have shown promise in drug delivery, biomedical imaging and as antiviral agents. In this work, hydroxyl functional dendrimers of generation 1 to 5 based on 2,2-bis(methylol)propionic acid (bis-MPA) were modified to bear 6 to 96 peripheral amino groups through esterification reactions with beta-alanine. All dendrimers were isolated in high yields and with remarkable monodispersity. This was successfully accomplished utilizing the present advantages of fluoride-promoted esterification (FPE) with imidazole-activated monomers. Straightforward postfunctionalization was conducted on a second generation amino-functional dendrimer with tetraethylene glycol through NHS-amidation and carbonyl diimidazole (CDI) activation to full conversion with short reaction times. Fast biodegradation of the dendrimers through loss of peripheral beta-alanine groups was observed and generational- and dose-dependent cytotoxicity was evaluated with a set of cell lines. An increase in neurotoxicity compared to hydroxyl-functional dendrimers was shown in neuronal cells, however, the dendrimers were slightly less neurotoxic than commercially available poly(amidoamine) dendrimers (PAMAMs). Additionally, their effect on bacteria was evaluated and the second generation dendrimer was found unique inhibiting the growth of Escherichia coli at physiological conditions while being nontoxic toward human cells. Finally, these results cement a robust and sustainable synthetic route to amino-functional polyester dendrimers with interesting chemical and biological properties.

Evaluation of Kinetic Parameters at the Transport of Indole-3-acetic Acid Through Bulk Liquid Membranes

Indole-3-acetic acid is a growth phytohormone considered the most important representative of auxin class. This paper presents the assessment of some kinetic parameters in the process of transport of indole-3-acetic acid taking into consideration the kinetic model of consecutive irreversible first order reactions. It was pursued the influence upon the process of parameters such as: feed phase concentration, stripping phase concentration in the presence of two type carriers: tributyl phosphate (TBP) and trioctylphosphine oxide (TOPO). Depending on these transport parameters were calculated kinetics parameters such as: pseudo-first-order apparent membrane entrance and exit rate constants, the maximum flux at the entrance and exit out of the membrane. The highest values of the transport flux is obtained in the presence of carrier trioctylphosphine oxide (TOPO) at the concentration in the feed phase of 10-4 mol/L indole-3-acetic acid and a concentration of 10--2mol/L NaOH in the stripping phase.

Treatment of cyanide wastewater by bulk liquid membrane using tricaprylamine as a carrier.

The transport of cyanide from wastewater through a bulk liquid membrane (BLM) containing tricaprylamine (TOA) as a carrier was studied. The effect of cyanide concentration in the feed solution, TOA concentration in the organic phase, the stirring speed, NaOH concentration in the stripping solution and temperature on cyanide transport was determined through BLM. Mass transfer of cyanide through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters (k(1), k(2), R(m)(max), t(max), J(a)(max), J(d)(max)) were also calculated. Apparently, increase in membrane entrance (k(1)) and exit rate (k(2)) constants was accompanied by a rise in temperature. The values of activation energies were obtained as 35.6 kJ/mol and 18.2 kJ/mol for removal and recovery, respectively. These values showed that both removal and recovery steps in cyanide transport is controlled by the rate of the chemical complexation reaction. The optimal reaction conditions were determined by BLM using trioctylamine as the carrier: feed phase: pH 4, carrier TOA possession ratio in organic phase: 2% (V/V), stripping phase concentration of NaOH: 1% (W/V), reaction time: 60 min, stirring speed: 250 r/min. Under the above conditions, the removal rate was up to 92.96%. The experiments demonstrated that TOA was a good carrier for cyanide transport through BLM in this study.

Kinetics of transport of sodium chloride using supported liquid pertraction

In the present work, the removal of NaCl using the present type of supported liquid membrane technique has been investigated. A simple apparatus devised and constructed was used to conduct the experiments. Various factors that would affect the progress of transport were studied and these were initial concentration (Ci) of simulated seawater in donor phase (DP), presence of mobile carrier (MC) in the liquid membrane (LM), concentration of MC in LM, presence of sequestering agent (SA) in the receptor phase (RP), and speed of stirring. The volume ratio of DP to RP was kept constant at 2:1. Type (1,2 dichloroethane (DCE)) and thickness (2 mm) of LM were kept constant. Cellophane constituted the support for the LM. The most important findings emphasized the importance of the presence of a MC in the LM to enhance mass transfer through the LM and that an optimum concentration of MC existed. Also the importance of stirring in promoting mass transfer by minimizing the boundary layer intact to the cellophane support was elucidated. The best conditions arrived at were MC = 0.0538 mol/l (mol of dibenzo-18-crown-6/l of LM), SA = 0.0617 mol/l (mol of soluble starch/l of RP), slow stirring (100 rpm) of DP, and using DCE as LM. The mass transfer of NaCl was analyzed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k1d, k2m, k2r, Rmmax, tmax, Jdmax, Jrmax) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusion-controlled. Results indicate that the membrane entrance and exit rate constants (k1, k2) increase directly with Ci and inversely with quantity of SA.

Investigation on a micro-pin-fin based membrane separator

We proposed a micro-pin-fin based membrane separator. An enclosed membrane with micron scale holes was symmetrically populated in a rectangular duct. When gas phase interacts with the membrane, the gas–liquid interface cannot break through the pin-fin holes due to the increased surface energy. A two-dimensional numerical model simulated the separation process. The volume of fluid (VOF) method tracked the gas–liquid interface. Multiscale grids were used. When a bubble attacks the pin-fin membrane, strong liquid circulation occurs at the membrane entrance. Pressures in the side region are larger than those in the core region. Liquid plugs are shortened due to the pressure driven flow from side region to core region to cause the bubble coalescence. The separation length was shortened while increasing the gas flow rates. The bubble lengths were weakly influenced by gas flow rates. Liquid plugs are quickly shortened following the membrane entrance. The frictional pressure drop of the two-phase mixture in the side region was larger than that of liquids in the core region, even at low gas flow rates. The ultra-large gas flow rates yielded quite large bubble pressure to exceed the capillary pressure limit, causing the separator failure. Ultra-low and large gas flow rates specified the separator operation range.

Bulk liquid pertraction of NaCl from aqueous solution using carrier-mediated transport

In the present work, removal of NaCl using the bulk liquid membrane (BLM) technique has been investigated, using a simple apparatus for conducting the experiments. Variables investigated were volume ratio of donor phase (DP) to receptor phase (RP), presence of sequestering agent (SA) in RP, type of organic liquid membrane (LM), quantity of mobile carrier (MC) in the LM. Stirring speed and volume of LM were kept constant at 100 rpm and 130 ml, respectively. The mass transfer of NaCl was analysed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k1d, k2m, k2r, , tmax, , and ) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusionally controlled. Results indicate that the membrane entrance and exit rate constants (k1, k2) increase with decreasing DP:RP ratio and with decrease in quantity of MC, and quantity of SA, and the presence of dichloroethane (DCE) is preferred to chloroform (CF) as LM.

Bulk liquid membrane extraction of silver(I) with 2-mercaptobenzothiazole as a carrier: Kinetic approach

The transport and separation of silver(I) ions across a bulk liquid membrane by 2-mercaptobenzothiazole (MBT) as carrier were investigated. The efficiency of Ag(I) transport was studied as a function of different parameters. The maximum of Ag(I) recovery was 85% in the presence of thiourea 0.1 M at pH 1, as complexing agent in the receiving phase, for a short extraction time of 4 h. A selective separation between Ag(I) and Mn(II) ions from equimolar mixture Ag–Cu–Mn solutions was performed. Besides, we have applied the kinetic model involving two consecutive irreversible first-order reactions to calculate the pseudo-first-order apparent membrane entrance and exit rate constants ke and ks, respectively. Under optimal conditions, the kinetic model curves of time dependence of silver concentrations (R) in the feed, membrane and receiving phases showed a good agreement with the experimental results. The apparent rate constants values were 6.93 × 10−3 min−1 for ke and 6.81 × 10−2 min−1 for ks. The transport of silver(I) is mainly controlled by the slow reaction of the formation of Ag–MBT complex at the membrane entrance.

Inhibitory and Bactericidal Properties of a Number of Dihydroxyazo Compounds

Inhibitory and bactericidal properties of a number of dihydroxyazo compounds have been studied in the Postgate medium containing sulfate-reducing bacteria (SRB) in planktonic form. Sulfate-reducing bacterium strain Luk used in this study was phylogenetically closed (99% similarity of 16S rRNA genes) to the type strain Desulfomicrobium apsheronum 1105T isolated from petroleum reservoir. The number of sulfate-reducing bacteria was counted by a method called the direct microscopic count. Special counting chamber was used. Biogenic H2S concentration was defined daily by the iodometric titration. Small concentrations (5-20 mg/L) of the compounds under study have been used. These compounds induce a decrease of the bacterial cells quantity and H2S production by SRB. Dihydroxyazo compounds inhibit carbon steel corrosion and hydrogen permeation through the steel membrane in the presence of SRB. Corrosion tests of the carbon steel samples were carried out by weight-loss method. Most high corrosion rate of steel in the inoculated media is observed in third day of bacteria development when maximum concentration of H2S is reached (190 mg/L). Its value is equal to 0.28 g/(m2h). Protective effect of the bactericides depends on the structure of their molecules. For estimation of hydrogen permeation into metal, two-chamber cell with a vertical steel membrane similar to the Devanathan cell was used. Entrance side of the membrane contacted with the working solution. The measurements were conducted under corrosion potential, cathodic and anodic polarization of the entrance membrane side. The SEM image of the membrane entrance side after the hydrogen permeation test for 2 h in the inoculated media in the absence and presence of the inhibitors is compared. Effect of dihydroxyazo compounds depends on their molecular structure. A presence of nitro-group or Cl-atom and 1-phenyl-3-methylpirazole group in the molecule increases the bactericidal and inhibitory ability of the substance. At that, a number of SRB cells, production of hydrogen sulfide by them sharply decreases, inhibitory effect essentially increases and hydrogen permeation into metal is retarded by 2.5 times in the stationary phase of bacterial vital cycle.

Kinetic of Alkaloids Extraction from Plant by Batch Pertraction in Rotating Discs Contactor

A liquid membrane process of Alkaloids extraction from Datura Innoxia solution was studied applying pertraction process in rotating discs contactor (RDC). Decane as a liquid membrane and dilute sulphuric acid as stripping solution were used. The effect of the fundamental parameters influencing the transport process, e.g. type of solvent used, effect of disks speed, amount of liquid membrane and effect of pH for feed and strip solution. The transport of alkaloids was analysed on the basis of kinetic laws of two consecutive irreversible first order reactions. Thus, the kinetic parameters (k1, k1, , tmax, and ) for the transport of alkaloids were determined. The effect of organic membrane type on percentage of Alkaloids transport was found to be in the order (n-decane> n-heptane> n-hexane> ethyl ether). The results showed that the highest alkaloids extraction was obtained when using two stages, (10 rpm) discs speed, (pH=9.5) of feed solution and (pH=2) of acceptor solution in n-decane. Observation showed that the membrane entrance rate constant k1 and percentage of alkaloids transported in strip phase increased with increasing numbers of stages but the exit rate constant k2 decreased. The alkaloids extraction ratio increased with increasing the disks speed from 5 to 10 rpm but decreased at 15 rpm and decreased when increasing the volume of membrane. Also pH of feed and strip solution affected the extraction ratio and rate constants.

Rapid transfer of methyl red using calix[6]arene as a carrier in a bulk liquid membrane

Abstract In the present investigation, a calix[6]arene-based derivative ( 1 ) is employed as a selective carrier for the efficient transport of methyl red (MR) through bulk liquid membrane (BLM). Initially, the selectivity of 1 towards MR was confirmed among different dyes, such as methyl green (MG), methyl violate (MV), methylene blue (MB), methyl orange (MO), and eosin gelblich (EG) by liquid–liquid extraction experiments. Furthermore, the effect of the initial MR concentration of salts (NaCl, Na 2 SO 4 , and Na 2 CO 3 ) and of the pH of the acceptor phase were also optimized using liquid–liquid extraction. Afterwards, the influence of basic parameters, such as carrier concentration in membrane phase, type of solvent, and stirring rate on MR transport was determined through BLM. Mass transfer of MR through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters ( k 1 , k 2 , R m max , t max , J d max , J a max ) were also calculated. Apparently, increase in membrane entrance ( k 1 ) and exit rate ( k 2 ) constants was accompanied by a rise in carrier concentration under a high stirring rate. In addition, CH 2 Cl 2 proved to be a better solvent than CHCl 3 and CCl 4 . The % transport of MR was 99% across the liquid membrane under optimized conditions. Real textile industrial wastewater samples gave also appreciable results in BLM under optimized conditions.

Transport of Hg(II) through bulk liquid membrane containing calix[4]arene thioalkyl derivative as a carrier

In this study effectiveness of 5,11,17,23 tetrakis[(propylthio)methyl]-25,26,27,28-tetrahydroxycalix[4]arene ( 1) towards Hg(II) across bulk liquid membrane has been examined. The effect of the fundamental parameters influencing the transport process, e.g. carrier concentration, type of solvent used, effect of temperature and time dependency of the process have been investigated. The mass transfer of Hg(II) was analyzed on the basis of kinetic laws of two consecutive irreversible first order reactions. Thus, the kinetic parameters ( k 1, k 2, R m max, t max, J d max, J a max) for the transport of Hg(II) were studied. The activation energy values for the extraction and re-extraction were found as 19.59 and 27.57 kJ mol − 1 , respectively. These values demonstrate that the process is diffusionally controlled by Hg(II). Observations show that the membrane entrance and exit rate constants ( k 1, k 2) increase with increasing stirring speed, carrier concentration and temperature. The effect of solvent on k 1 and k 2 was found to be in the order of CH 2Cl 2 > CHCl 3 > CCl 4. The effectiveness and reproducibility of Hg(II) transport has proved that 1 is an efficient carrier of Hg(II) in BLM process.

Kinetic study of mercury (II) transport through a liquid membrane containing calix[4]arene nitrile derivatives as a carrier in chloroform

In this study, the kinetics studies of mercury (II) ion transport through a bulk liquid membrane system which contains calix[4]arene nitrile derivatives (5,11,17,23-Tetra-tert-butyl-25,27-bis-(2-cyanobenzyloxy)-26,28-dihydroxycalix-[4]arene (membrane I) and 25,27-bis-(2-cyanomethoxy)-26,28-dihydroxycalix-[4]arene (membrane II) as a membrane were investigated at different temperatures and stirring rates. The kinetics was analyzed by means of a kinetic model involving two consecutive irreversible first order reactions. The parameters such as transport rate constants, membrane entrance rate, k 1, and the membrane exit rate, k 2, and the maximum values for membrane entrance and exit values J d max and J a max were determined for the experimental data. It was found that both membrane entrance and exit rate constants increase with temperature. The activation energies were found as 6.96 ± 0.15 and 6.91 ± 0.15 kcal/mol, for ligand membranes I and II, respectively. These activation values indicate that the transport process for both membranes is controlled by species diffusion.

Kinetic Study of an Effective Pb(II) Transport through a Bulk Liquid Membrane Containing Calix[6]arene Hexaester Derivative as a Carrier

The article describes transport of Pb(II) through bulk liquid membrane (BLM) containing calix[6]arene hexaester derivative (1) as a carrier. The effect of various parameters such as temperature, carrier concentration, stirring speed and type of solvent on the Pb(II) transport efficiency of the carrier through BLM was evaluated. The activation energy values for the extraction and re-extraction were found as 56.33 kJ mol−1 and 14.79 kJ mol−1, respectively. These values demonstrate that the process is diffusionally controlled by Pb(II). Observations indicate that the membrane entrance and exit rate constants (k1, k2) increase with increasing stirring speed as well as carrier concentration and decrease with increasing temperature. The effect of solvent on k1 and k2 was found to be in the order of CH2Cl2 > CHCl3 > CCl4.

Liquid Membrane Transport Kinetics of Hg (II) by Dithio Derivatized Macrotricyclic Compound

The present study has been undertaken to investigate a process that removes inorganic mercury from waste water streams by use of a liquid membrane system in which a novel macrocyclic ligand based on dithio derivatized biscrown ether has been used as a cation carrier. The effect of temperature, stirring rate and different solvents on the kinetic parameters like k1, k2 and flux values J a max, J d max and tmax were also investigated. It was found that the membrane entrance rate constant (k1) and the membrane exit rate constant (k2) increased with increasing temperature and stirring rate. The membrane entrance rate constants (k1), exit rate constants (k2), as well as the flux values vary in the order of CH2Cl2 > CHCl3 > CCl4 in different solvents study