Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Salinity and Hardness

A series of experiments have been conducted to characterize and quantify the effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. A set of correlations were developed to predict the viscosity of polymer solutions. These correlations consider the individual and combined effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. The power-law model for the viscosity behavior has been modified to accommodate the influence caused by these three factors. Nonlinear regression was performed on the experimental data to develop the proposed correlations. The proposed correlations can be integrated into any reservoir simulator for polymer injection and should prove useful for the initial screening for the selection of the polymer for enhanced oil recovery applications in oil reservoirs.      

Experimental Study and Numerical Modeling of Rheological and Flow Behavior of Xanthan Gum Solutions Using Artificial Neural Network

This study investigated effect of temperature, concentration, and shear rate on rheological properties of xanthan gum aqueous solutions using a Couette viscometer at temperatures between 25°C and 55°C and concentrations of 0.25 wt% to 1.0 wt%. The Herschel–Bulkley model described very well the non-Newtonian behavior of xanthan gum solutions. Shear rate, temperature, and concentration affected apparent viscosity and an equation was proposed for the temperature and concentration effect valid for each shear rate. This article also presents an artificial neural network (ANN) model to predict apparent viscosity. Based on statistical analysis, the ANN method estimated viscosity with high accuracy and low error.     

Rheological Behavior of Viscoelastic Wormlike Micelles in CTAB/SSS/H2O Systems

The effect of the addition of sodium 4-styrenesulfonate (SSS) and KNO3 as well as temperature and shear rate on the structural transition of aqueous micellar solutions of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) was studied by viscosity. The effect of hydrocarbons on viscoelastic CTAB solutions was also examined. Possible mechanism for formation of CTAB wormlike micelles in the presence of sodium 4-styrenesulfonate (SSS) and KNO3 was discussed. The rapid increase in the apparent viscosity of CTAB solutions on the addition of SSS and KNO3 was due to the transition in micellar shape from spheres to wormlike ones. The rheological properties of CTAB solutions fit Maxwell model at low shear frequency. AFM image indicated a structure of transient network of CTAB/SSS/KNO3/H2O solution.     

Experimental Investigation on Yield Stress of Water-in-Heavy Crude Oil Emulsions in Order to Improve Pipeline Flow

An experimental study on yield stress of water-in-heavy crude oil emulsions has been carried out by using a HAAKE RS6000 Rheometer with a vane-type rotor. Several factors such as oil volume fraction, shear rate, temperature, and emulsifying agent on the yield stress of emulsions were investigated. Zero shear viscosity of heavy crude oil was 6000 mPas at 30°C, with a density 955 kg/m³. This study shows that the yield stress increases linearly with the increasing shear rate, and displays an exponential decay with increasing the temperature and oil volume fraction. Although the addition of emulsifying agent enhanced the stability of the emulsion, to some extent it also increased the yield stress, especially for the emulsions with high oil volume fractions. Therefore, to reduce the start-up force for the pipeline transport of water-in-heavy crude oil emulsions, the starting rate should be decreased, temperature increased, or oil volume fraction increased. These results are helpful to improve the transportation of water-in-heavy crude oil in pipeline.      

Modeling and Scaling of Food Dispersions

Scaling laws, determined by dimensional analysis, have been used to make experimental predictions of constitutive shear-flow rheology. This study aimed to scale and model the flow curves of various suspensions consisting of xanthan gum (0.5, 1 wt%) and WPI (2, 4 wt%), and to determine the best-scaling law and rheological model. The scaling methods were relative viscosity, Péclet number, and Reynolds number. When the apparent viscosity is reduced relative to the viscosity of the medium at zero-shear rate, a distinct reduced flow curve is obtained, regardless of xanthan and WPI concentrations. This study tough to develop a technique of simplifying complex non-Newtonian flow curves and, therefore, predicting the rheological flow curves and fluid mechanics when different modifiers are added to food suspensions. The flow behavior of all samples was successfully modeled with the power law, Ellis, and Cross models; the power law model best described the flow behavior of dispersions. Results showed that both G′ and G″ increased with xanthan and WPI. However, viscoelastic behavior was mainly governed by the xanthan gum content.     

Influence of Glycerol and Temperature on the Phase Behavior and Micellization of CTAB and SDS in Aqueous Solutions

In this work the micellization of sodium dodecylsulfate (SDS) and cetyltrimethyammonium bromide (CTAB) in water-glycerol mixed solvent have been investigated at 25, 35, and 45°C, respectively. The micellization of both surfactants in pure water at different temperatures has also been studied. The phase diagrams of the surfactants in water-glycerol mixed solvent were also established. From the conductivity measurements, the critical micelle concentration (CMC) and the degree of counterion dissociation (β) were obtained as a function of glycerol-water ratio and temperature. Standard free energy of micellization (ΔG°_mic) as a function of glycerol contents and temperature was calculated and discussed. It has been found that the micellization of the two surfactant in solutions with glycerol at 25°C and in pure water at higher temperatures are not the same although they have equal dielectric constants values.     

Studies on p-Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis-Schiff Base Manganese(III) and Cobalt(II) Complexes in CTAB Surfactant Micellar Solution

The unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹Cl, MnL²Cl) or morpholino pendant (MnL³Cl, CoL³) have been employed as models for hydrolase by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit higher catalytic activity in the buffered CTAB micellar solution and the rate increases with pH of the buffered CTAB micellar solution under 25°C. The complexes containing a crown ether group exhibit higher catalytic activities than the free-crown analogues. The catalytic activity of manganese(III) complex is superiority over cobalt(II) complex in catalyzing hydrolysis of PNPP under the same ligand.     

Kinetics and Equilibria of Synthesized Anionic Surfactant onto Berea Sandstone

We present static adsorption studies of anionic surfactants on crushed Berea sandstone. The maximum adsorption density was 0.9604 mg/g. The kinetics of adsorption process was modeled using pseudo-first-order and pseudo-second-order rate equations at 25°C and 70°C. The equilibrium adsorption process was validated using Langmuir and Freundlich adsorption models. In addition, the effects of different parameters that govern the effectiveness of these surfactants such as pH and temperature were also investigated. The kinetic study results show that the surfactant adsorption is a time dependent process. The apparent rate constant of adsorption process determined by the first-order kinetic model at 25°C and 70°C were 0.11768 and ?0.04513, respectively. The rate constant for pseudo-second-order kinetic model was 0.0086 at 25°C and 0.0101 at 70°C. The adsorption of anionic surfactant followed pseudo-second-order kinetic model. The Freundlich and Langmuir model constant were 1.6509 × 10^?4 and ?9.775 × 10^?5, respectively. The equilibrium results showed that the adsorption of anionic surfactant onto Berea sandstone was well described by Langmuir adsorption model. It was concluded that anionic surfactants performed better at higher pH and temperature.      

Experimental Design Approach to Investigate the Effects of Operating Factors on the Surface Tension,Viscosity, and Stability of Heavy Crude Oil-in-Water Emulsions

In this article, the effects of various operating factors on the surface tension, viscosity, and stability of two heavy oil types in water emulsions for pipeline transportation are studied using the Taguchi experimental design approach. The surface tension of heavy crude oil-in-water emulsion is decreased by increasing the emulsifier concentration while the stability of emulsions is increased. The viscosity and stability are increased by an increase in oil content. An increase in the salinity and mixing speed leads to an increase in the stability of emulsion.     

Prediction of Density,Surface Tension,and Viscosity of Quaternary Ammonium-Based Ionic Liquids ([N222(n)]Tf2N) by Means of Artificial Intelligence Techniques

In this work, thermophysical properties of quaternary ammonium-based ionic liquids (ILs) including density, surface tension, and viscosity are produced by two powerful artificial intelligence techniques: genetic function approximation (GFA) and artificial neural network (ANN). In proposed GFA and ANN models, the critical temperature and water content of studied ILs ([N_222(n)]Tf₂N with n = 5, 6, 8, 10, and 12) as well as operation temperature were given as the input parameters and the density, surface tension, and viscosity were predicted as the output results. The obtained results reveal that the selected input parameters are appropriate for prediction of thermophysical properties of quaternary ammonium-based ILs. In addition, the high statistical quality represented by various criteria and the low prediction errors of the presented models indicate that they can accurately predict the density, surface tension, and viscosity of new ILs without recourse to experimental data.     

Membrane Permeability and Stability of Liposomes Suspended in Shear Flow

The 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposome has been characterized in its stability and membrane permeability to 5(6)-carboxyfluorescein (CF) in the shear flow generated in the cone-and-plate geometry. The CF-containing liposomes (CFLs) were 101–323 nm in the mean diameter D _P as measured with the dynamic light scattering (DLS) method. Adsorption of lipids to the cone-and-plate was observed, which clearly depended on the shear stress applied at the shear rate γ up to 1.5 × 10³ s^?1. The permeability of CFLs with D _P of 101 and 117 nm definitely increased at the maximum γ value where the adsorption was negligible. The permeability coefficient of CF at 40°C in the shear flow was 5.7 times larger than that in the static liquid system. The DLS measurements revealed that the size distribution of CFLs with D _P of 101–189 nm was practically unchanged under the shear stress even at 55°C. The results obtained show that the shear stress can permeabilize the CFL membranes with neither structural collapse nor coalescence.     

Effect of Water Fraction on Rheological Properties of Waxy Crude Oil Emulsions

This article discusses the effect of water fraction on the rheological properties of waxy crude oil emulsions including gel point, yield stress, viscosity, and thixotropy. The experimental results reveal that the rheological behaviors of the w/o emulsion samples all intensify with the increase of water volume fraction within 60%. Of more significance is that a correlation for w/o emulsions between yield stress and water volume fraction is put forward with an average relative error of 6.75%. In addition, some mainstream viscosity prediction models of w/o emulsions are evaluated, and Elgibaly model is the best-fit for the emulsions in this study.     

Rheological Scaling Methods in Food Matrices Containing Stabilizer

Relative viscosity, Peclet, and Reynolds scaling methods were used in various food matrices consist of tragacanth gum (TG) (0.5, 1% wt), Oleic acid (5, 10% v/v) and WPI (2, 4% wt) and the best scaling law was selected. As these emulsions are non-Newtonian, they do not obey the usual, simple, scaling laws. When the apparent viscosity is reduced to relative viscosity of the medium at zero shear rate, a distinct reduced flow curve is obtained, regardless of TG, oleic acid, and WPI concentrations. This will lead to a technique of simplifying complex non-Newtonian flow curves and therefore predicting the rheological flow curves and fluid mechanics when different modifiers are added to food emulsions. The flow behavior of all samples was successfully modeled with the Cross model, Power law model, and Ellis model, and Power law model was found as the better model to describe the flow behavior of dispersions. Results showed that both G′ and G″ increased with TG, oleic acid and WPI concentrations. However, the viscoelastic behavior was mainly governed by the TG content.     

Evaluation of Pomegranate (Punica Granatum L.) Pulps for the Removal of Copper(II) Ions: Kinetic,Equilibrium, and Desorption Studies

Pomegranate pulp has been used as novel adsorbent for removing Cu(II) ions from aqueous solution. The optimum conditions for removal of Cu(II) ions were found to be pH 5.32, biosorbent dose 0.1 g, contact time 120 minutes, initial concentration 50 mg/L, and temperature 30°C. The kinetic data were well fitted to the pseudo-second-order model. The biosorption process agreed with the Langmuir isotherm model. Maximum monolayer biosorption capacity was 7.30 mg/g. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic. Desorption studies were carried out with different desorbing agents.      

Investigation of Oil–Asphaltene Slurry Rheological Behavior

The presence of asphaltene means additional difficulties related to transport and processing due to the increased crude oil viscosity caused by the asphaltene. For a better knowledge of the flow properties of asphaltene containing crude oils, it is necessary to understand how asphaltene affects the rheological properties. The aim of this article is to provide information on such rheological properties of oil–asphaltene slurry systems. The results of rheological experiments show that the non-Newtonian flow curves can be approximated by the Bingham plastic model to determine the apparent viscosity and the yield stress as a function of asphaltene concentration and temperature. An explanation is also provided for the observed behavior.     

Effect of Ionic Surfactants on the Adsorption of Quercus infectoria Natural Dye on Cotton Fiber: A Kinetic Study

The adsorption kinetics of Quercus infectoria natural dye on cotton in the absence and presence of the cationic (cetyl trimethyl ammonium bromide; CTAB) and anionic (sodium lauryl sulfate; NaLS) surfactants has been investigated at three temperatures, namely, 40°C, 50°C, and 60°C. On increasing the surfactant content in the surfactant-dye mixture, the initial rate of adsorption (h _i) and the adsorption capacity at equilibrium (q _e) were found to increase while pseudo-second-order rate constant (k ₂) was found to decrease. The retarding effect of surfactant on k ₂ was in order of CTAB > NaLS. The activation parameters for adsorption process have been evaluated in each case, and the mechanism of adsorption process has been discussed.     

Adsorption of Fe(III) from Aqueous Medium onto Glycine-Modified Chitosan Resin: Equilibrium and Kinetic Studies

The adsorption of Fe(III) onto glycine-modified chitosan (G@Chs) resin has been investigated. The parameters studied include the effects of pH, contact time, and initial metal ion concentrations by batch method. The optimal pH for the adsorption of Fe(III) was found to be 2.5. The results obtained from equilibrium adsorption studies are fitted in various adsorption models such as Langmuir and Freundlich, and each model parameter were evaluated. Kinetics and thermodynamic parameters of the adsorption process were also investigated. The maximum uptake was found to be 0.9 mmol g^?1 at 25°C.