Aqueous Solutions Of Sodium Carboxymethylcellulose Research Articles

Physicochemical characteristics of a nanocomposite film based on purified sodium carboxymethylcellulose and selenium nanoparticles

AbstractIn this study, selenium nanoparticles (SeNPs) were synthesized and stabilized by reducing sodium selenite using ascorbic acid in an aqueous solution of sodium carboxymethylcellulose (Na‐CMC) with a degree of substitution of 0.97 and a degree of polymerization of 810. IR‐Fourier spectroscopy revealed that coordination bonds between functional groups in Na‐CMC and SeNPs resulted in the development of polymer‐metal complexes. UV–Vis spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS) methods were used to determine the SeNP sizes in the structure of the nanocomposite film. Investigation of the stabilization and nonstabilization of SeNPs over several cycles has shown that the effect of the polymer matrix of Na‐CMC on the stabilization of nanoparticles was achieved for 672 h, which was confirmed by the unchanged size distribution and resistance to change of the SeNPs synthesized in Na‐CMC solutions.

Enhanced removal of VOCs from aquifers during air sparging using thickeners and surfactants: Bench-scale experiments

The effects of controlled air flow paths during air sparging on the removal of volatile organic compounds were examined in this study using a two-dimensional bench-scale physical model. An aqueous solution of sodium carboxymethylcellulose (SCMC), which is a thickener, was used to increase the resistance of water to displacement by injected air in a region around the targeted zone. At the same time, an aqueous solution of sodium dodecylbenzene sulfonate (SDBS), which is a surfactant, was used to reduce the air entry pressure to enhance the air flow through the targeted region. Trichloroethene (TCE), dissolved in water, was used to represent an aqueous phase volatile organic compound (VOC). A binary mixture of perchloroethene (PCE) and n-hexane was also used as a nonaqeous phase liquid (NAPL). Controlled air flow through the source zone, achieved by emplacing a high viscosity aqueous solution into a region surrounding the TCE-impacted zone, resulted in increased TCE removal from 23.0% (control) to 38.2% during a 2.5h period. When the air flow was focused on the targeted source zone of aqueous phase TCE (by decreasing the surface tension within the source zone and its vicinity by 28dyn/cm, no SCMC applied), the mass removal of TCE was enhanced to 41.3% during the same time period. With SCMC and SDBS applied simultaneously around and beneath a NAPL source zone, respectively, the NAPL components were found to be removed more effectively over a period of 8.2h than the sparging experiment with no additives applied; 84.6% of PCE and 94.0% of n-hexane were removed for the controlled air flow path experiments (with both SCMC and SDBS applied) compared to 52.7% (PCE) and 74.0% (n-hexane) removal for the control experiment (no additives applied). Based on the experimental observations made in this study, applying a viscous aqueous solution around the source zone and a surfactant solution in and near the source zone, the air flow was focused through the targeted contaminant zone, enhancing the removal of VOCs from either an aqueous phase or a NAPL phase.

Effect of operating conditions and physico–chemical properties on the wet granulation kinetics in high shear mixer

The wet granulation process is sensitive to changes in product properties and process variables. The optimal process and formulation are based on the knowledge of the granule growth mechanisms and of the effects of product properties and process variables. This paper presents the study of wet granulation of microcrystalline cellulose powder, MCC (Avicel PH101) using high-shear mixer granulator. It aims at understanding the effect of operating parameters (impeller rotational speed, liquid binder flow ate) and of physicochemical properties (viscosity, wettability) of a binder solution on solid particles surfaces, on the agglomeration kinetics. The experiments are carried out with water, aqueous solutions of sodium carboxymethylcellulose, polyvinylpyrrolidone, hydroxypropylméthylcellulose or a non ionic surfactant oxo-C 10C 6 at a critical micellar concentration. Concerning the process variables the experimental results show that an optimal interval of impeller speed operation exists ranging from 150 to 200 rpm for granule growth. Below, an uncontrollable agglomerate size and localised over-wetting occur, and above granule breakage occurs. Increasing the liquid binder flow rate reduces the extension of the non growth regime, but does not affect the granule mean size. The effect of the physicochemical properties is evaluated using a modified capillary viscous number, Ca′, that we define as the ratio between the viscous forces ( μ L U) and the work of adhesion W a = γ L(1 + cos θ). For Ca′ < 1, the viscosity of the solution does not significantly affect the granulation process. The dominant forces in the granulation process are the interfacial forces since increasing the work of adhesion enhances the growth kinetics. For Ca′ > 1.6, the viscous forces predominate and control the granule growth.

Rheological properties of aqueous solutions of sodium carboxymethylcellulose and methylhydroxypropylcellulose blends

It was found that a specific feature of aqueous solutions of Na-CMC and MHPC is the presence of a viscosity extremum for a polymer ratio of 80:20 wt. % and in treating the MHPC solution in a rotary-pulsed activator at the rate of 300 rpm. It was hypothesized that an increase in the size of the coils of the MHPC macromolecules as a result of improvement of the thermodynamic quality of the solvent in the first case and their stretching in the second case is the cause of the increase in the viscosity of the solutions. Films spun from solutions, characterized by anomalous high viscosity values, have high strength and elasticity.

Gas absorption in a hollow-fiber membrane contactor with pseudo-plastic liquid as an absorbent

Gas/liquid mass transfer characteristics of a membrane contactor with hydrophobic microporous hollow fibers were investigated under laminar flow conditions. Physical absorption of oxygen in a pseudo-plastic non-Newtonian liquid was studied. The experiments were carried out with aqueous solution of sodium carboxymethylcellulose. For comparison, the experiments with water as an absorbent were carried out as well. The influence of physical characteristics of liquids and operating conditions on oxygen absorption was examined. The results show that hydrophobic membrane contactors can be efficiently used for gas absorption in a pseudo-plastic liquid, especially when membrane resistance can be neglected.

Normalized particle residence times as affected by process parameters in a vertical scraped surface heat exchanger

The effects of process parameters and their two‐way interactions on the normalized particle residence times (NPRTs) of 1.0–2.0 cm potato cubes in 0.4–1.2% aqueous solutions of sodium carboxymethylcellulose (CMC), flowing at 453–599 mL s−1 in a vertical scraped surface heat exchanger, rotating at 60–160 rpm were investigated. Minimum and maximum NPRTs and the standard deviations of the mean values were not significantly affected by the conditions studied (P &lt; 0.05). Mean NPRTs were significantly influenced by process parameters, including the concentration of the carrier, mutator speed and particle size, as well as two‐way interactions between flow rate, mutator speed and particle size (P &lt; 0.001). The orientation of the heat exchanger was an important factor influencing the forces acting on the particles.

RESIDENCE TIME DISTRIBUTION of CYLINDRICAL PARTICLES IN A CURVED SECTION of A HOLDING TUBE: the EFFECT of PARTICLE SIZE and FLOW RATE1

The residence time and the residence time distributions of cylindrical particles (density 1130 kg/m3 and particle concentration 20% v/v) in a U‐bend of 22 cm radius of curvature were studied. All experiments were conducted at room temperature and with an aqueous solution of sodium carboxymethylcellulose (0.5% CMC) as the carrier medium. Two levels of particle size (11 and 20 mm) and three levels of product flow rates (0.66 × 10−3, 0.81 × 10−3, and 0.97 × 10−3 m3/s) were used. the results obtained from this study showed that the mean and the standard deviation of the normalized residence time of particles decreased as either particle size or flow rate was increased. the E(θ) and F(θ) curves indicated that flow profile of particles approached the plug flow profile as the particle size or the flow rate was increased. Results obtained from regression analyses revealed that the mean and the standard deviation of the normalized residence time were significantly influenced by particle Froude number and most strongly by particle‐to‐tube diameter ratio.

Effects of temperature and concentration on the steady shear properties of aqueous solutions of carbopol and CMC

The measured steady shear viscosities are reported in this paper for 1400∼2400wppm neutralized aqueous solutions of Polyacrylic Acid(Carbopol-934) and 4000∼11500wppm aqueous solutions of Sodium Carboxymethylcellulose(CMC). The data cover a temperature range of 10–70° C. Within the power-law viscosity range, it is the solution kind not the polymer concentration that results in the different correlations of the fluid behavior index n and fluid consistency index K with temperature. The steady shear properties of the aqueous Sodium CMC solutions seem to be more sensitive to temperature but less sensitive to polymer concentration than that of the neutralized aqueous Carbopol solutions.

Statistical method to evaluate the critical Reynolds number for pseudoplastic fluids in tubes

An experimental, non-intrusive tube system with appropriate instrumentation for measuring pressure drop and mass flow rate was developed to investigate the departure from laminar flow of pseudoplastic fluids (aqueous solutions of sodium carboxymethylcellulose). A critical Reynolds number was selected to correspond to the intersection of the two lines joining the laminar and turbulent flow data on the pressure drop versus Reynolds number plots. The standard deviation of pressure drop increased at these critical points. Results also indicated large spikes at these points in the plots of variance ratio of pressure drop versus the critical Reynolds number. This phenomenon could form the statistical basis for establishing the departure from laminar flow. In the laminar region, standard deviations were low, suggesting calm, stable flow of the fluids, a well known characteristic of laminar flow.

NATURAL CONVECTION HEAT TRANSFER BETWEEN NON‐NEWTONIAN FLUIDS and an IRREGULAR SHAPED PARTICLE1

ABSTRACTNatural convection heat transfer was investigated between aqueous solutions of sodium carboxymethylcellulose (modeled as power law fluids) and a mushroom shaped particle, under transient conditions, with various initial temperature differences. Convective heat transfer coefficients (h) were observed to decrease over time due to thermal equilibration. the average value of h was significantly higher for heating (75 to 310 w/m2‐C) than for cooling (22 to 153 w/m2. C), and decreased with increasing viscosity (CMC concentration). For the lower viscosity ranges, h increased significantly with increasing initial temperature difference. Correlations were developed between Nusselt number and generalized Rayleigh and Fourier numbers.

Predicting Steady and Oscillatory Shear Rheological Properties of CMC and Guar Gum Blends from Concentration and Molecular Weight Data

ABSTRACTThe steady shear and oscillatory shear Theological properties of aqueous solutions of sodium carboxymethylcellulose (CMC), guar gum and CMC/guar blends of ratios 3:1, 2:1, 1:1, 1:2, and 1:3 by weight were measured in the concentration range of 0.5, 0.75, 1.0, and 1.5% by weight. For the CMC/guar systems, the zero‐shear rate viscosity, η0, time constants λ1 and λ2 and the slopes of the non‐Newtonian region of the log η vs log λ and log η′ vs log ω curves, − Sη and − Sη, can be related to concentration and molecular weight.

The effect of shear rate on the viscosity of solutions of sodium carboxymethylcellulose and k‐carrageenan

AbstractThe apparent viscosities of aqueous solutions of sodium carboxymethylcellulose (NaCMC) and k‐carrageenan have been measured over a range of shear rates from 14 to 1142 s−1. Comparable measurements were also made on gum solutions to which glucose, sucrose, or glucose syrup had been added. For all the solutions the variation of relative viscosity with shear rate fits a power law equation. Addition of sugars to the most concentrated solutions of NaCMC has no effect on the non‐Newtonian behaviour but addition of glucose syrup to the most dilute solutions of NaCMC decreased the non‐Newtonian behaviour. However, the general pattern of behaviour showed close similarity with that of guar gum and locust bean gum. In the more concentrated glucose and sucrose solutions the non‐Newtonian behaviour of k‐carrageenan was increased appreciably. There was no comparable effect on k‐carrageenan in glucose syrup solutions. This different behaviour of k‐carrageenan is attributed to the development of solute‐solute interactions.

Effect of sodium carboxymethylcellulose on the reactivity of hydrated electrons and cystamine anion radicals in aqueous solutions

Rate constants for several reactions of the hydrated electron with different solutes, shown to be diffusion controlled in normal aqueous solution, were carried out in an aqueous solution of sodium carboxymethylcellulose with a relative viscosity of 250 cP, using the pulse radiolysis technique. In carboxymethylcellulose solutions, hydrated electron rate constants are not dependent on macroscopic viscosity : rate constants are ≈ 1010 dm3 mol–1 s–1 for solutions with 250 cP viscosity. For comparison the same reactions were observed in water + glycerol solutions with comparable solution viscosities. The results are rationalised on the basis that a small molecule binary solvent system such as water + glycerol has a higher microscopic and macroscopic viscosity, whereas a carboxy-methylcellulose solution has a high macroscopic viscosity but the microscopic viscosity is little or no different to the pure solvent.

Models for the formation of gas bubbles at a single submerged orifice in a non-Newtonian fluid

Nitrogen bubbles were emitted by a single horizontal orifice submerged in an aqueous solution of sodium carboxymethylcellulose (C.M.C.). Their behaviour follows the Ostwald Dé Waele rheological model: τ = mE o n ; τ is the shear stress and E o the shear rate.

Heat of dilution of aqueous solutions of sodium carboxymethylcellulose and sodium polyacrylate

The heats of dilution (ΔH) of aqueous solutions of sodium carboxymethylcellulose (NaCMC) having degrees of etherification of 0.75 and 1.4, were measured. Data for NaCMC at 25°C were in good agreement with Manning's limiting law, whereas this was not the case for sodium polyacrylate (NaPAA) at 25°C. The ΔH values of NaCMC and NaPAA at 40°C were in agreement with the theory. It was found that Manning's limiting law satisfactorily described the dependence of the ΔH of polyelectrolytes on the concentration, charge density, and temperature.

Temperature Distribution in Laminar Flow through Circular Tube

Transfer of heat in a steady state in non-Newtonian fluids flowing in laminar motion through circular tube with constant wall temperature has been treated theoretically and experimentally by a number of workers. However, on the distribution of temperature within the fluid, few experimental data have hitherto been published.The theoretical interpretations of the experimental data have so far been made under the assumptions that the physical properties, such as heat capacity, density, consistency index and thermal conductivity of the fluids are independent of temperature, and that the heat produced by viscous friction and the heat conduction in the axial direction are negligibly small.The temperature distribution in the radial directions were directly measured by thermistor probe. As samples of Newtonian and non-Newtonian fluids, water and aqueous solutions of sodium carboxymethylcellulose of various concentrations were respectively used. In the analysis of the latter fluid, the power law is assumed.The observed temperature distributions agree fairly well with the theoretical predictions except at the vicinity of the tube wall.

Flow of viscoelastic fluids past a flat plate

AbstractThe flow of viscoelastic fluids past a flat plate has been investigated. Experimental studies were performed with aqueous solutions of sodium carboxymethylcellulose used as viscoelastic fluids and corn syrup as a viscous Newtonian fluid. It was observed that the flow patterns of elastic and inelastic fluids are markedly different. Tracer particles placed in the approaching viscoelastic fluids to follow their motion were seen to first decelerate and then to accelerate until a nearly constant velocity was reached. On the other hand tracer particles in the Newtonian fluid were observed merely to decelerate smoothly to the constant velocity.The drag force measured for the viscoelastic fluids was found to be roughly twice that predicted by inelastic models of fluid behavior. Predicted and measured values of the drag force for the Newtonian fluid agreed well.A discussion of mathematical solutions to the problem of flow of viscoelastic fluids past a flat plate is given. Solutions are obtained for a prototype of flow past a flat plate, the suddenly accelerated flat plate (Stokes' problem) with linear viscoelastic models used. The results from Stokes' problem qualitatively explain the anomalous kinematical behavior and the large drag force.

Bubble motion and mass transfer in non‐Newtonian fluids

AbstractInstantaneous mass transfer coefficients were obtained for the absorption of carbon dioxide bubbles rising in an aqueous solution of sodium carboxymethylcellulose. The rheological character of the solutions was well described by the Ellis model.Mass transfer coefficients were high initially but trailed off rapidly with bubble age. Exceptions were found at specific diameters where the bubble shape went through a transition. At about 0.2 cm. a transition from ellipsoidal to a sphere shape occurred, which has also been observed in Newtonian fluids. At a larger diameter, however, the non‐Newtonian fluid showed a shape change from a spherical “cap” to a “top” shape and finally to an ellipsoid. A sudden increase of mass transfer coefficient accompanied each shape transition.Drag coefficient data were correlated successfully with a new Reynolds number. The Newtonian and power law portion of the Ellis model each contributed a component to the Reynolds number, which, when added together, correlated drag data for the bubbles as well as for glass spheres.Attempts to account for transition shape changes and bubble tailing in the non‐Newtonian fluid and their effects on bubble mass transfer are included.

Observations on the thixotropy and structural characteristics of sodium carboxymethylcellulose

AbstractThe thixotropy of aqueous solutions of sodium carboxymethylcellulose (CMC) has been investigated with a rotational viscometer at shear rates up to 4400 sec.−1. Measurements were made in relatively concentrated (1 to 3%) solutions where intermolecular effects play an important role, and differences between samples of nominally the same composition are readily apparent. The results are interpreted in terms of moleculare properties and interactions.

Non‐Newtonian viscosities in dilute aqueous solutions of sodium carboxymethylcellulose

AbstractThe reduced viscosity vs. concentration relation was measured for sodium chloride solutions of sodium carboxymethylcellulose (Na‐CMC of DP ≓ 400 and DE ≓ 0.7) in a range of low concentrations (0.003 to 0.09 g./100 ml.), and the data obtained were analyzed following the procedure of Pals and Hermans. The results confirmed in many aspects findings which had previously been made in the literature, and supplied values of the necessary molecular quantities for our own sample. They indicated that our Na‐CMC molecule was relatively uncoiled even in solutions of high ionic strength. The Huggins slope constant was found to increase approximately linearly with increasing reciprocal of the ionic strength of the solution. Next, the shear dependence of reduced viscosity in dilute solutions of this polyelectrolyte was investigated by the use of a viscometric apparatus which was especially designed for accurate measurements at low shear rates. The shear rate region investigated was from about 50 to 1000 sec.−1. The measurements were made on salt‐free solutions and on solutions of constant ionic strength; in both cases only the regions of sufficiently low concentrations were treated. In the salt‐free solutions the ηsp/C vs. q (q is shear rate) curves showed an upward curvature rather than a quadratic dependence at the limit of shear rate. In this case, the initial slope of each curve increased markedly with increasing dilution. The plots of ηsp/C vs. q for solutions of constant ionic strength (ca. 0.0015 mole/l.) were approximately represented by straight lines within the concentration range investigated. The slope of the straight lines decreased regularly with increasing dilution. Some evidence that these plots have a horizontal initial tangent was observed, but this was never conclusive due to the paucity and inaccuracy of exprimental data at shear rates smaller than 100 sec.−1. The intrinsic viscosity obtained from ηsp/C vs. C curves at constant shear rates for the isoionic system was independent of q. From these findings it was realized how markedly the viscous behavior in dilute solutions of the polyelectrolyte studied was influenced by the addition of small amounts of neutral salt, not only in viscosity value itself but also in its shear rate dependence. Our data and results herein presented were concerned only with a sample of one (average) molecular weight and one degree of etherification. More data, therefore, are needed on samples of varying degrees of polymerization and etherification before a more definite understanding of the problem herein treated is possible.