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Particles size distribution (PSD) is introduced as a tool for analysis of bentonite aggregation and swelling kinetics. Raw Ca-bentonite was purified using a combined wet sieving and sedimentation processes, followed by thermochemical treatment with Na2CO3 to increase its swelling capacity. The detailed analysis of the PSD shows a strong correlation between the PSD and the swelling process. For the chemically treated raw bentonite, PSD revealed two different peaks representing unswelled and swelled particles along with some aggregates. The swelling is shown to be a kinetically controlled process that depends on time, temperature, and bentonite chemical composition. At the beginning of the chemical treatment, the effect of aggregates was more dominant; therefore, the viscosity did not increase much with particle size. However, the combined chemical and thermal treatment has enhanced the Na-activation process and boosted bentonite swelling. The rheological measurements have shown enhancement in the viscosity and confirmed the PSD findings. The same optimal treatment conditions are obtained from both rheological measurements and PSD analysis. A model is developed based on classical reaction rate kinetics and used to describe the conversion from unswelled to swelled particles. The PSD has a strong correlation with the physical properties of the suspension such as the viscosity. The swelling rate fits a second order model with a rate constant, k, in the range 0.002 to 0.124 h−1 and an activation energy, E, of 87 kJ/mol. PSD analysis together with the developed kinetic model are powerful tools for studying the swelling kinetics of bentonites. [ABSTRACT FROM AUTHOR]

Separation of clay minerals from industrial wastewaters is of great academic and practical importance. Current treatment techniques are either not economically viable, not environmentally friendly, or both. Thus, researchers are actively trying to develop optimal and more environmentally friendly wastewater treatment processes. Clay minerals like montmorillonite, bentonite, kaolinite and illite have numerous applications in various industries including, mineral processing, cosmetics, pharmaceuticals, paint, dyes, cement, concrete, functional fillers, paper making, clarification of wines and oils, water treatment and improving drilling mud properties. Their wide applications increased the volume and treatment complexity of water contaminated with them since they form highly stable suspensions in water. Flocculating agents such as polyelectrolytes have the potential to separate the above-mentioned minerals from industrial wastewater effluents. Polyelectrolytes are more effective and environment-friendly flocculants, in contrast to inorganic metal salts and some non-biodegradable synthetic polymers that pose serious hazards to human health and the environment. The development of polyelectrolytes is considered to be among the most important breakthroughs in solid–liquid separation processes, which have resulted in an improved treatment of water polluted with minerals. In the characterization of clay mineral separation using polyelectrolytes, it has been common practice in the past to either emphasize on the flocculation behavior of colloidal clay-polyelectrolyte suspensions (i.e., settling behavior or floc sizes) or on the behavior of networked clay-polyelectrolyte suspensions (i.e., filterability or dewaterability of sediment). However, flocculation and rheological parameters, which are very important factors in optimizing the wastewater treatment process, have rarely been reported in the literature. The aim of this paper, therefore, is to offer a comprehensive review of the state-of-the-art contributions for polyelectrolyte systems, focusing on the development of different types of polyelectrolytes and their applications in flocculating and dewatering clay minerals. Electrokinetics and rheological behavior of different clay minerals using different polyelectrolytes are critically evaluated. The effect of several parameters related to the clay mineral (type, composition), the polyelectrolyte (e.g., synthetic/natural, molecular weight, charge type, charge density, linear vs branched) and the flocculation medium properties (e.g., pH, ionic strength, clay mineral and polyelectrolyte concentration and type) are reviewed. This paper provides up-to-date progress in the treatment of water contaminated with clay minerals using various polyelectrolytes. The gaps and potential parameters of investigation in flocculation optimization studies are identified and more economical and environmentally friendly reagents in wastewater treatment are highlighted. [ABSTRACT FROM AUTHOR]

The effects of the addition of sodium carbonate (Na 2 CO 3 ) and the subsequent simultaneous heating and stirring on the rheological behavior of Ca-bentonite colloidal dispersions have been investigated in this study. Ca-bentonite dispersions were treated with Na 2 CO 3 at various ratios (2, 4, 12 g/100 g bentonite), and then subjected to heating and stirring for variable periods. It was found that the swelling and the viscosity of the treated bentonite samples increased with increasing Na 2 CO 3 content and the optimal Na 2 CO 3 level (relative to the bentonite content) was found to be 4 g/100 g of Ca-bentonite (4%). The results also showed that simultaneous heating and stirring enhanced the bentonite swelling and ion exchange processes for sodium activation. The rheological properties of the Ca-bentonite suspensions depend on the strength of the bentonite gel structure and the inter-particle interactions. Although the treated and untreated bentonite samples showed gel and solid-like behavior in the linear viscoelastic region (LVR), the region where the storage (G′) and loss (G″) moduli are independent of applied strain and/or stress, the G′ values of the Na 2 CO 3 treated bentonite samples were higher than those of untreated samples. All bentonite samples (whether Na 2 CO 3 treated or untreated) showed more elastic than viscous response (i.e., G′ > G″) within the LVR. The results showed that bentonite dispersions treated with 4% Na 2 CO 3 displayed the highest elastic behavior. The relationship between zeta potential and pH for the untreated and Na 2 CO 3 treated Ca-bentonite dispersions were investigated. Bentonite colloids were stable in the examined range of pH (3 − 12); such wide pH range stability is essential for many industrial applications. Finally, the effect of heat treatment on the swelling behavior of 4% Na 2 CO 3 treated bentonite dispersions was extracted from particle size measurements using a laser scattering particle size analyser. The results showed that the particle size increased with the combined heating and stirring treatment for the first 3 h then remained constant. This increase in particle size is likely due to improved swelling and the existence of some of weak particle-particle interactions bentonite (aggregates). [ABSTRACT FROM AUTHOR]

The traditional way to mitigate loss circulation in drilling operations is to use preventative and curative materials. However, it is difficult to quantify the amount of materials from every possible combination to produce customized rheological properties. In this study, machine learning (ML) is used to develop a framework to identify material composition for loss circulation applications based on the desired rheological characteristics. The relation between the rheological properties and the mud components for polyacrylamide/polyethyleneimine (PAM/PEI)-based mud is assessed experimentally. Four different ML algorithms were implemented to model the rheological data for various mud components at different concentrations and testing conditions. These four algorithms include (a) k-Nearest Neighbor, (b) Random Forest, (c) Gradient Boosting, and (d) AdaBoosting. The Gradient Boosting model showed the highest accuracy (91 and 74% for plastic and apparent viscosity, respectively), which can be further used for hydraulic calculations. Overall, the experimental study presented in this paper, together with the proposed ML-based framework, adds valuable information to the design of PAM/PEI-based mud. The ML models allowed a wide range of rheology assessments for various drilling fluid formulations with a mean accuracy of up to 91%. The case study has shown that with the appropriate combination of materials, reasonable rheological properties could be achieved to prevent loss circulation by managing the equivalent circulating density (ECD). [ABSTRACT FROM AUTHOR]

• Electrokinetics and rheological behaviour of conditioned MBR sludge was studied. • Highly MW PAMs showed a better performance comparing to low MW organic coagulants. • MBR sludge with/without conditioning has a time-dependent non-Newtonian behaviour. • Values of G′ and G″ demonstrated the MBR sludge has viscoelastic behavior (G′ > G″). The influence of polyelectrolyte's type and structure on the rheological characteristics of industrial highly stable membrane bioreactor (MBR) sludge have been investigated and were related to its degree of flocculation and dewatering. The polyelectrolytes used for the conditioning of MBR sludge were polyacrylamides (PAMs) of varying charge density (CD), molecular weight (Mw) and molecular architecture, polydiallyldimethylammonium chloride (polyDADMAC) and polyamine. Rheological measurements showed that the MBR sludge with/without conditioning has a thixotropic (time-dependent) behavior with measurable yield stress. It exhibited a non-Newtonian shear thinning behavior and well represented by the Bingham model. The measurements of elastic (G ′) and viscous (G″) moduli proved the viscoelastic solid-like behavior of the MBR sludge with/without conditioning (G ′ > G″). Bingham yield stress, τ o , viscosity, µ, and G′ , were used for examining the rheological behavior of the conditioned MBR sludge. About 77–94% higher in τ o , 86–96% in µ, and 76–92% in G′ were obtained by conditioning the sludge with different types of PAMs. These percentages vary depending on the type and structure of the PAMs. The highest τ o , µ, and G′ was obtained by using a linear structure PAM, FO 4690 SSH. This behavior was in good agreement with flocs size, D 50 , zeta potential, ζ, and capillary suction time, CST. The results obtained by conditioning MBR sludge with different PAMs were compared with those obtained by conditioning with polyamine and polyDADMAC. Polyamine and polyDADMAC have raised the τ o , µ and G′ of the MBR sludge by 52%, 84%, and 63%, respectively. Overall, MBR sludge conditioned with PAMs having a high CD in the case of high Mw (FO 4690 SSH, FO 4698 SSH) and low CD in the case of low Mw (FO 4498 XXR), resulted in greater τ o , µ and G′ compare to those formed with polyamine and polyDADMAC. Therefore, PAMs are building a more compact network that highly reduces the trapped water within the sludge flocs. [ABSTRACT FROM AUTHOR]

• Utilization of onshore natural gas wastewater for Scenedesmus sp. microalgae cultivation was achieved. • Microalgae growth phase affected the flocculation and rheological properties of suspensions. • Flocculation efficiency exceeded 97% for both growth phases under optimized conditions. • Flocculated biomass matrices demonstrated high gel strength and shear resistance. Microalgae harvesting at an industrial scale remains a techno-economic bottleneck for large-scale microalgae production that can account for up to 30% of the total cost of biomass production. A wide range of harvesting techniques have been applied commercially, among which, coagulation-flocculation techniques prove to be both convenient and cost-effective as pre-treatment techniques used in conjunction with other methods. In this study, process wastewater acquired from onshore natural gas facilities in Qatar was utilized to cultivate freshwater microalgae specie Scenedesmus sp. for simultaneous pollution abatement and biomass harvesting applications. Scenedesmus sp. was cultivated in two growth phases (fast and slow growth phases) to examine the influence of the microalgae growth phase on the flocculation process and rheological behavior. Effective flocculation was achieved using a commercial high charge density and high molecular weight cationic polyacrylamide-based flocculant. Flocculation efficiencies exceeded 97% for both fast and slow growth phase suspensions at an optimum flocculant dose of 10 mg/L. Optimum conditions were well corroborated by residual turbidity and zeta potential measurements. For fast growth phase suspensions, the optimum PAM dose coincided with a minimum residual turbidity of 2.35 NTU and a zeta potential of −0.52 mV. Similarly, the optimum PAM dose was fixed based on a minimum residual turbidity of 2.30 NTU and a zeta potential of +0.63 mV for slow growth phase suspensions. Large, easily settleable and compact flocs were obtained with average D 50 values of 70.7 μm and 142.0 μm recorded for fast and slow growth phase suspensions, respectively, at optimum PAM dose. Moreover, based on rheological characterization studies, the flocculated suspensions demonstrated an overall non-Newtonian pseudoplastic (shear thinning) fluid behavior. Introduction of cationic PAM significantly improved the viscosity and yield stress of the flocculated suspensions around the optimum PAM dose range. At the optimum PAM dose, the initial viscosities were recorded as 10.37 and 39.19 mPa.s with yield stresses of 12.84 and 16.59 N/m2 for fast and slow growth phase suspensions, respectively. The flocculated biomass further displayed a viscoelastic solid (gel) behavior, characterized by high gel strength and resistance to shearing around optimum flocculant doses. At the optimum PAM dose, the storage moduli were recorded as 886.2 and 1068.6 mPa for fast and slow growth phase suspensions, respectively. [ABSTRACT FROM AUTHOR]

Natural deep eutectic solvent (NADES) produced herein this work by mixing betaine and alanine with lactic acid and malic acid with 1:1 M mixing ratios. Thermophysical properties including water content, thermal stability, density and gas solubility of CO 2 and N 2 were experimented at different isotherms for wide pressures range up to 50 bars. Moreover, detailed rheological experiments were conducted on the studied materials to obtain viscosity and deduce the dynamic flow behavior. A pressure driven physisorption mechanism was observed for the studied systems. Betaine based NADES materials showed superior carbon dioxide and nitrogen solubility when they are mixed with lactic acid. On the other hand, the rheological experimental results show shear-thinning effect in which the η is decreasing with shear rate at all temperatures. Low viscosity profiles NADES assure the less mass transfer resistance for lactic acid based NADES systems and it also confirmed that the high CO 2 and N 2 solubility for lactic acid based NADES samples. [ABSTRACT FROM AUTHOR]

The settling of drilling cuttings is important for the drilling and clean-out operations. The current article provides a Computational Fluid Dynamics (CFD) modeling study of particle settling behavior during the drilling operations, with a special focus on the impact of fluid rheology, flow regime, particle size and shape on the settling rate. The Eulerian-Lagrangian method are adopted to track particle trajectories in a shear-thinning fluid under quiescent conditions. The rheological properties of the drilling fluids are described by different rheological models. Settling of spherical and ellipsoidal cuttings, with various aspect ratios, is studied for particles with a diameter ranging between 2 and 6 mm. The settling behavior is predicted for particles with narrow (0.5–2 mm), medium (0.5–6 mm) and broad (0.5–10 mm) particle size distributions (PSD). Applying a non-Newtonian power-law model at low shear rates, where the fluid is in the Newtonian regime, resulted in 11–19% over-prediction of settling velocities as compared to the experimental data. On the other hand, ignoring the particle-induced shear rate by assuming a Newtonian fluid behavior in the transition regime showed 8–10% difference between the estimated and experimental settling rates. Therefore, the CFD computations of settling rates suggest that Cross and Carreau models provide more accurate predictions than a simple power-law model. The selection of the suitable rheological model is a key factor in predicting settling in drilling fluids. This is more important for small particles where the Newtonian behavior is dominant and particle-induced shear rate is low. Ellipsoidal cuttings exhibited significantly greater resistance to settling as compared to spherical particles, mainly due to the increased drag force. Further, the terminal settling velocity of ellipsoidal cuttings consistently increased with the particle aspect ratio. Cuttings with broad PSD showed ~32 times higher settling velocity than particles with narrow PSD. CFD results are validated with experimental measurements. Moreover, results for settling of non-spherical particles are validated with an empirical correlation. Agreement of experimental and theoretical predictions is observed when the fluid and flow regimes are well identified and described. Image 1 • Settling velocity of particles in Newtonian and non-Newtonian drilling fluids is predicted. • The Eulerian-Lagrangian method has been adopted to track particle trajectories in a shear-thinning fluid. • Simulation results have been validated with published experimental measurements. • The impact of cuttings aspect ratio on their settling behavior is investigated. • Average settling velocity of size distributed cuttings is also studied. [ABSTRACT FROM AUTHOR]

• Hybrid coagulation-flocculation on the flocculation of bentonite is investigated. • Compared to single PAM, hybrid systems performed exceptionally well. • Hybrid systems were able produce bigger flocs than single systems. In this study, the influence of the hybrid coagulation-flocculation system on the flocculation and shear resistivity of bentonite suspension has been investigated. Two short-chained coagulants, polyamine and polyDADMAC, accompanied with low and high Molecular Weight (Mw) long-chained anionic Polyacrylamide (PAM) flocculants have been used to enhance the size and mechanical properties of the produced flocs. Four characterization techniques were used as evaluation criteria of degree of flocculation including turbidity, zeta potential (ζ), floc size analysis and rheology. Optimum dosages between 5 and 10 mg/L were obtained for flocculants and between 20 and 30 mg/L for coagulants in hybrid systems. Compared to single systems, hybrid systems performed exceptionally well. Removal efficiency of 99% was achieved using hybrid systems producing water with turbidity as low as 1.05 NTU. Although differences were insignificant in the treatment quality, significant improvement was achieved in floc size and rheological behavior. Hybrid systems were able to produce large flocs of more than 400 µm, five times bigger than flocs from the single cationic coagulant systems. Most importantly, rheological testing of produced slurries revealed the remarkable advancement achieved by hybrid systems. Hybrid systems were able to increase the elastic modulus (G′) by more than ten times resulting from the compacted flocs present in the system. Furthermore, resistivity toward shear and oscillations were improved. Ultimately, hybrid systems have surpassed the single cationic systems by achieving slightly better treatment besides producing larger, denser and more resistive flocs. Generally, polyDADMAC performed better than polyamine in hybrid systems. The combination of polyDADMAC with high Mw PAM gave the best separation as well as the largest flocs, while the combination with low Mw PAM resulted in the best rheological properties. [ABSTRACT FROM AUTHOR]

• Thermo-rheological characterization of three Malic Acid based NADES is presented. • The rheological study showed the NADES can be used as CO 2 capture sorbents. • Yield stress for pumping the NADES at different shear rates and temperatures. The rheological characterization for a series of Malic Acid based Hydrogen Bond Donor Natural Deep Eutectic Solvents (NADES) is studied in this work for their potential usage as sorbents for CO 2 capture. Three different NADES combinations were synthesized based on B-Alanine, Betaine and Choline Chloride as Hydrogen Bond Acceptors. The work provides insights on the rheological behaviors of Malic Acid-based NADES at temperature ranges from 25 to 105 °C and shear rates from 0.01 to 1000 s−1, which shows the impact of altering the Hydrogen Bond Acceptor in a NADES system. All Malic Acid-based systems showed non-Newtonian, shear thinning behaviors and diverse viscoelastic flow behavior ranging from as low as 3 × 102 up to 4 × 107 mPa stress requirements showing viscous liquids to solid-like gel structures. The different NADES combinations showed strong temperature dependence behavior, where the density at different temperatures dropped from 1.42 to 1.37 g/cm3 for B-Alanine: Malic Acid. This behavior fits on the Bingham model revealed that the yield stress for all Malic Acid-NADES decreased with increasing temperature as expected for the shear thinning materials. The differences in the yield stress magnitudes of approximately 7 × 102 to 6 × 106 mPa in the case of B-Alanine: Malic Acid for example was attributed to the changes in the nature and the numbers of the interaction forces between the Hydrogen Bond Acceptor and Hydrogen Bond Donor of the NADES and the molecular weight. The viscoelasticity of these NADES systems demonstrated the fundamental differences between the ways the different Hydrogen Bond Acceptor interacts with the Hydrogen Bond Donor. The Linear Viscoelastic Region (LVR) was set to 0.1%–10% according to the type of NADES under a frequency range of 0.1–100 rad/s. The hole theory was used as a theoretical approach to describe the structural differences behind the flow behaviors. [ABSTRACT FROM AUTHOR]

The problem of lost circulation is a direct consequence of the presence of fractures or high permeability. Lost circulation material (LCM) is used to treat the loss that occurs or proactively strengthen the wellbore of the potential loss zones. The polyacrylamide (PAM)/Polyethylenimine (PEI) cross-linkable polymer gel is proven to work best in zone-sealing and plugging applications. In addition to their thermal stability, the fact that these gels are flexible gives them the advantage of deforming and sealing-off multiple and complex near wellbore fractures. The primary objective of this study is to investigate the gelation kinetics of the PAM/PEI cross-linkable polymer to be used in drilling fluids formulations to enhance wellbore stability and strength. Different combinations of polymers and crosslinkers were evaluated; potential polymers were screened for gelation kinetics and gel strength in typical drilling mud formulations. The gelation time of the polymer-based drilling mud formulation is determined in salt-free and in saline systems. The results on rheological properties and gelation kinetics were used to prepare a gelling mud formulation using PAM/PEI cross-linkable polymer as LCM. The produced gel was thermally stable under high-temperature-high-pressure reservoir conditions, which will result in enhanced wellbore strengthening. • Investigation of the gelation kinetics of the PAM/PEI cross-linkable polymer in drilling fluids. • Impact of different parameters on the strength of the PAM/PEI LCM gel. • Effect of temperature and retarder on the gelation process. • Investigation of the rheological properties of a polymer-based drilling fluid. • Treating lost circulation with PAM/PEI pill to increase the maximum sealing pressure. [ABSTRACT FROM AUTHOR]