Cloud Point Measurements Research Articles

Specific anion effects on the interfacial properties and aggregation of alkylphenol ethoxylate surfactants

The effect of Hofmeister anions on aggregation of nonionic surfactants and the formation of microemulsion systems was evaluated. Added salt effects on the interfacial properties and aggregation of ethylene oxide condensates of nonylphenol were characterized by cloud point measurements, surface tension, fluorescence spectroscopy, light scattering, and formulation scans. The specific effects of anions on the cloud point followed the trend predicted by the Hofmeister series: H2PO4− < Cl− < Br− < NO3− < I− < SCN−, with the H2PO4− being the most kosmotropic anion and generating the most significant cloud point reduction. The specific effects of anions on the critical micelle concentration (CMC) also followed the Hofmeister series, with kosmotropic anions causing a decrease and chaotropic anions generating an increase in the CMC. Chaotropic anions decreased the size of the aggregates, while kosmotropic anions increased it, as evaluated by dynamic light scattering. The effect of Hofmeister anions on microemulsion formation in nonionic surfactant-oil–water (SOW) systems was assessed by formulation scans. Although the kosmotropicity of the anion did not influence the optimum formulation value, it did affect the phase behavior around the optimum formulation, pointing to the possibility of tuning microemulsion formulations via the choice of added electrolyte.

Synthesis and Phase Behavior of a Platform of CO2-Soluble Functional Gradient Copolymers Bearing Metal-Complexing Units.

The synthesis and characterization of a platform of novel functional fluorinated gradient copolymers soluble in liquid and supercritical CO2 is reported. These functional copolymers are bearing different types of complexing units (pyridine, triphenylphosphine, acetylacetate, thioacetate, and thiol) which are well-known ligands for various metals. They have been prepared by reversible addition–fragmentation chain-transfer (RAFT) polymerization in order to obtain well-defined gradient copolymers. The copolymers have been characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, thermal gravimetric analysis (TGA), dynamical scanning calorimetry (DSC) and cloud point measurements in dense CO2. All the investigated metal-complexing copolymers are soluble in dense CO2 under mild conditions (pressure lower than 30 MPa up to 65 °C), confirming their potential applications in processes such as metal-catalyzed reactions in dense CO2, metal impregnation, (e.g., preparation of supported catalysts) or metal extraction from various substrates (solid or liquid effluents). Particularly, it opens the door to greener and less energy-demanding processes for the recovery of metals from spent catalysts compared to more conventional pyro- and hydro-metallurgical methods.

Non-Solvent Induced Phase Separation (NIPS) for Fabricating High Filtration Efficiency (FE) Polymeric Membranes for Face Mask and Air Filtration Applications.

Protection against airborne viruses has become very relevant since the outbreak of SARS-CoV-2. Nonwoven face masks along with heating, ventilation, and air conditioning (HVAC) filters have been used extensively to reduce infection rates; however, some of these filter materials provide inadequate protection due to insufficient initial filtration efficiency (FE) and FE decrease with time. Flat sheet porous membranes, which have been used extensively to filter waterborne microbes and particulate matter due to their high FE have the potential to filter air pollutants without compromising its FE over time. Therefore, in this study, single layer polysulfone (PSf) membranes were fabricated via non-solvent induced phase separation (NIPS) and were tested for airflow rate, pressure drop and FE. Polyethylene glycol (PEG) and glycerol were employed as pore-forming agents, and the effect of the primary polymer and pore-forming additive molecular weights (MW) on airflow rate and pressure drop were studied at different concentrations. The thermodynamic stability of dope solutions with different MWs of PSf and PEG in N-methylpyrrolidone (NMP) at different concentrations was determined using cloud-point measurements to construct a ternary phase diagram. Surface composition of the fabricated membranes was characterized using contact angle and X-ray photoelectron spectroscopy (XPS), while membrane morphology was characterized by SEM, and tensile strength experiments were performed to analyze the membrane mechanical strength (MS). It was observed that an increase in PSf and PEG molecular weight and concentration increased airflow and decreased pressure drop. PSf60:PEG20:NMP (15:15:70)% w/w showed the highest air flow rate and lowest pressure drop, but at the expense of the mechanical strength, which was improved significantly by attaching the membrane to a 3D-printed polypropylene support. Lastly, the FE values of the membranes were similar to those of double-layer N95 filters and significantly higher than those of single layer of N95, surgical mask and HVAC (MERV 11) filters.

Clouding and thermodynamic behavior of the triton X-100 + metformin hydrochloride drug mixture: Investigation of the impacts of potassium salts

The cloud point (CP) of aqueous triton X-100 (TX-100) and metformin hydrochloride (MNH) mixture was investigated in the attendance of various inorganic salts (KCl, KHSO4, K2SO4, and K3PO4) media. TX-100 concentration for CP measurement was chosen well above the critical micelle concentration value of TX-100. The values of CP decrease as the electrolyte’s concentration raises, turning the clear solution cloudy. The reason of the reducing CP is the enhanced aggregation. Thermodynamic variables of the clouding process (standard free energy (ΔG0c), standard enthalpy (ΔH0c), and standard entropy (ΔSco)) were determined at CP. The Gibbs free energy (ΔG0c) values were positive but dropped as the additive (inorganic electrolytes) concentrations increased. This result demonstrated that the TX-100 + MNH mixture's phase partition was thermodynamically unfavoured, and the percentage of its non-spontaneity reduced as the electrolytes concentration enhanced. The values of enthalpy (ΔH0c) and entropy (ΔSco) for the phase separation were achieved negative at lower electrolyte concentrations and positive at higher contents. The ΔH0c and ΔSco values suggest that hydrophobic and electrostatic interactions are the primary forces amongst TX-100 and MNH. Here, the intrinsic enthalpy gain (ΔH0*c) and the compensation temperature (Tc) are as well computed and explained.

Towards Realizing High-Voltage Aqueous Zinc Batteries: An Investigation of the Zinc Anode in Concentrated Acetate-Based Electrolytes

Zinc-based aqueous battery systems are attractive for grid storage applications due to the inherent electrolyte safety, material non-toxicity, low cost, high volumetric capacity of zinc and the low polarizability of the zinc anode in aqueous solutions. Despite these key features, they possess lower energy density when compared to lithium-ion batteries primarily due to the limited working potential range for aqueous electrolytes. In addition, zinc hosts a slew of problems such as inhomogeneous material distribution upon cycling and the formation of inactive zinc species and dendrites, all of which contribute to capacity loss and ultimately, cell failure. Water-in-salt electrolytes (WiSE) have been found to be an effective strategy to expand the electrochemical window of aqueous electrolytes for high energy density aqueous-based batteries, including zinc batteries. There is a growing amount of literature on highly concentrated acetate-based electrolytes as low-cost and non-toxic WiSE for lithium, potassium, sodium and magnesium and zinc battery systems. However, work is scarce on the nature of zinc electrochemistry, morphology and reversibility in these concentrated electrolytes at realistic current densities (> 1 mA/cm2) and higher zinc utilization. Understanding the electrochemical behavior of zinc in this electrolyte system will significantly aid in the development of a high voltage zinc aqueous battery.In this work, the zinc electrochemical performance and surface morphology is studied in highly concentrated bi-salt potassium acetate (KOAc)-zinc acetate (Zn(OAc)2) electrolytes. The impact of the high concentration on the electrochemical working window of the electrolytes is measured using potential sweep and constant-current techniques. As the acetate concentration is varied from 1 m to 32 m, the largest electrochemical window is measured at 3.33 V for 31 m KOAc+ 1 m Zn(OAc)2. Zinc half cells are cycled at current densities of 1-5 mA/cm2 to examine zinc reversibility with respect to zinc depth-of-discharge (DOD) in these electrolytes. The zinc discharge product is visualized by in-operando optical microscopy as a function of the potential and is observed to be a zinc plating/stripping phenomenon in contrast to zinc dissolution/precipitation typically observed in alkaline media. Energy dispersive X-ray spectroscopy and X-ray diffraction studies display the minor presence of zinc oxide and zinc hydroxide after repeated cycling. Cloud point measurements are performed to measure the phase stability of these electrolytes at 5-25ºC as a function of acetate concentration, which show that concentrations below (and including) 27 m KOAc + 1 m Zn(OAc)2 does not induce crystallization at these temperatures. Preliminary measurements using spectroscopic techniques such as Raman and nuclear magnetic resonance (NMR) spectroscopy are conducted to elucidate ion solvation structures as a function of acetate concentration. Overall, the current and proposed studies are fruitful in understanding the relationship between zinc anode and the concentrated acetate-based electrolytes in the pursuit of a high-voltage aqueous zinc battery.

Solubility limitations of residual steryl glucosides, saturated monoglycerides and glycerol in commercial biodiesel fuels as determinants of filter blockages

AbstractNewer, improved high pressure common rail diesel engines require increased protection from damaging particles in fuel, resulting in tighter, low‐micron filtration requirements. The unobstructed flow of fuel through filters underlies the well‐known efficiencies and reduced exhaust emissions of diesel engines, and when flows are hindered, these efficiencies become severely compromised. Biodiesel fuels frequently contain saturated monoglycerides, glycerol (GLY) and/or steryl glucosides, systemic impurities that become problematic when low concentrations exceed ill‐defined solubility limits, usually unexpectedly at low temperatures. Here, filters and blended fuels from seven flow obstruction incidents were subjected to detailed compositional analyses. With one exception the fuels contain estimated levels within international specifications, yet exhibit heterophase (HP) formation in the laboratory at 2°C, well above measured cloud points. Feedstock composition, pretreatment and/or purification processes are found to modulate insolubility risks. Interferences in standard gas chromatography methods used without modification can hide or complicate estimates of residual levels of GLY. The data show that classical variables controlling solubility, such as concentrations and temperatures, play important roles in setting the risks associated with in situ formation of HPs from these common impurities. Further, such risks are likely attenuated considerably by reductions in critical impurities beyond currently specified limits.

Poly (ε‐caprolactone)‐based porous membranes for filtration applications—effect of solvents on precipitation kinetics, performance, and morphology

AbstractThis work presents fabrication, precipitation kinetics, morphological analysis, and permeation performance of poly (ε‐caprolactone) (PCL) phase inversion membrane, which is a biodegradable polymer. Asymmetric membranes of PCL were fabricated by nonsolvent‐induced phase inversion method using different casting solvents. The effect of casting solvents on the precipitation kinetics, membrane morphology, and performance for filtration applications was studied. Solvents selected based on Hansen solubility parameter value were N,N‐dimethyl formamide, N‐methyl‐2‐pyrrolidone, tetrahydrofuran, triethyl phosphate, 1,4‐dioxane, and acetone. Ternary phase diagram constructed by cloud point measurement described the precipitation kinetics and thermodynamics of the phase inversion. The fabricated membranes were characterized by its thermal, mechanical, and morphology studies. Permeation performance of the prepared membranes was analyzed by studying its equilibrium water content, porosity, and pure water flux. Morphology analysis of membranes showed porous asymmetric structure and spongy to finger like morphology in different solvents. Cloud point measurement showed different precipitation kinetics in each solvent leading to different morphological features to the polymer membranes. Size of the pores of all these membranes determined using the Guerout–Elford–Ferry equation suggests application of these membranes for microfiltration process.

Criteria Governing Rod Formation and Growth in Nonionic Polymer Micelles.

Self-assembled wormlike micelles (WLMs) are widely studied in small-molecule surfactants due to their unique ability to break and recombine; however, less is known about the structure and dynamics of nonionic polymer WLMs. Here, solutions of seven triblock poloxamers, composed of poly(propylene oxide) (PPO) midblocks and poly(ethylene oxide) (PEO) end blocks, are comprehensively examined to determine the role of poloxamer composition, temperature, and inorganic salt type and concentration on rod formation and subsequent elongation into WLMs. Phase separation and sphere-to-rod transition temperatures were quantified via cloud point measurements and shear rheology, respectively, and corroborated with small-angle neutron scattering (SANS). The local microstructure of resulting rodlike micelles is remarkably similar across poloxamer type and sodium fluoride (NaF) or sodium chloride (NaCl) content. Salt addition reduces transition temperatures, with the most pronounced effects for poloxamers with high PEO molecular weights and PEO fractions. Between these two temperatures, several poloxamers elongate into WLMs, where shear rheology detects increases in viscosity up to 6 orders of magnitude. Despite similar local microstructures, poloxamer identity and salt content impact micelle growth substantially, where large poloxamers with lower PEO fractions exhibit the highest viscosities and longest relaxation times. While sodium fluoride has little impact on micelle growth, increasing NaCl concentration dramatically increases the WLM viscosity and relaxation time. This result is explained by different interactions of each salt with the micelle: whereas NaF interacts primarily with PEO chains, NaCl may also partition to the PPO/PEO interface in low levels, increasing micelle surface tension, scission energy, and contour length.

Conductivity and cloud point studies of the interaction of lomefloxacin hydrochloride with anionic and nonionic surfactants in electrolytes solution

The interaction of lomefloxacin hydrochloride (LMFH) drug (utilized to treat different bacterial infections) with anionic (sodium dodecyl sulfate (SDS)) and nonionic (triton X-100 (TX-100)) surfactants in electrolytes media has been carried out applying the conductometric and cloud point (CP) measurement methods. SDS is very useful to prohibit different viral infections and to extract DNA/RNA. Two critical micelle concentrations (cmc) were observed for LMFH + SDS mixtures within the investigated surfactant concentration. The cmc values of SDS increase monotonically with the increase of the LMFH concentration. The cmc values of LMFH + SDS mixtures were reduced as the ionic strength of electrolytes increases. In the case of the LMFH + SDS mixture, the cmc values showed reverse U-shaped change with the augmentation of temperature in the electrolyte medium. The extent of counterion binding (β) varies significantly with the change of ionic strength of the electrolytes and concentration of the drug. The CP values of the LMFH + TX-100 mixture was increased and decreased with the enhancing of LMFH and electrolyte concentrations respectively. The standard Gibbs free energy changes both for first and second micellization (ΔG1,mo &ΔG2,mo) were attained to be negative throughout the study suggesting spontaneous micellization of LMFH + SDS mixture in all the cases. The ΔG1,mo &ΔG2,mo values increase with the increase of temperature. Again, ΔG2,mo > ΔG1,mo signify that second micellization is more spontaneous. The positive free energy changes of the LMFH + TX-100 mixture reveal the nonspontaneous nature of the clouding process. The non-spontaneity of clouding experiences a reduction with the rise of TX-100 concentration. The other thermodynamic parameters, transfer properties as well as entropy-enthalpy compensation parameters of micellization and clouding processes have been assessed. The intrinsic enthalpy (ΔHmo,∗) values reveal that micelle is more stable in electrolyte media.

Ternary Liquid–Liquid Equilibrium for Phosphoric Acid Extraction from Aqueous Solutions with 1-Pentanol or Methyl Butyl Ketone at T = (298.2, 308.2, and 318.2) K

The tie-line values of the aqueous mixture (H2O + phosphoric acid + organic solvents) were checked at several temperatures and air pressures. Methyl butyl ketone or 1-pentanol was selected as the organic solvent. Solubility data were specified for an aqueous ternary mixture employing the cloud point measurements. All the ternary mixtures exhibit the type-1 liquid–liquid phase behavior system. Experimental data were determined employing the refractive index method, the Karl–Fischer technique, and acidimetric titration. Binary interaction parameters were predicted employing liquid–liquid equilibrium modeling. The NRTL and UNIQUAC models were employed to define which model is more reliable. The trustworthiness of the experiment outcome was approved by considering the Hand and Othmer-Tobias equations. Selectivity factors and distribution coefficients were derived to determine the solvents’ extraction capacity. The effect of temperature change was checked on the solubility curve and extraction process at different temperatures.

Study on waxy crudes characterisation and chemical inhibitor assessment

Wax deposition brings severe challenges to the production, transportation, and storage of crude oils. Accumulation of wax can block the pipeline, lead to equipment failure, and lose production. The use of chemical inhibitors has been reported as one of the most effective measures to mitigate wax deposition in the pipeline. The inhibition efficiency depends on the effects of the inhibitor molecules on the formation, growth, agglomeration and morphology of wax crystals. The chemicals and their compositions in the inhibitor together with the crude composition determine wax inhibition performance. Many different types of chemical inhibitors have been developed. Oil industry benefits significantly from high-efficiency inhibitors. This paper reported a simple method to optimise the inhibition performance by blending different inhibitors. Firstly, a comprehensive characterisation of two naturally waxy crude oils (KSG#49 and Ex Mwambe) and a synthetic crude oil was presented. The synthetic crude oil was prepared by mixing a dead oil of 3% wt wax content with a solid wax sample obtained from the North Sea field. The variation in properties of the three oils was evaluated through cloud point measurements, pour point, wax content, SARA fractions, colloidal instability index, American Petroleum Institute gravity (APIg), and the n-Paraffin distribution. Then, the influence of four Polymer-based pour point depressants (PPDs) on wax crystallization were critically assessed. The PPDs induced morphological changes to wax crystals transformed the needle-shaped crystals into an agglomerate. The small particles dispersed in the oil matrix reduced the apparent viscosity and wax gelling properties, and the efficiency of PPDs could be affected by the SARA fraction. A higher fraction of flocculated asphaltenes provides active sites for wax crystallization. Hence it increases cloud point and interferes with the crystal inhibition mechanism. Finally, a blended PPD produces a synergistic effect on inhibition performance that effectively reduces apparent viscosity, wax appearance temperature (WAT) and pour point (PP). The improvement can be attributed to the interactions between the molecules of wax inhibitors with wax crystals. This works sheds light on new inhibitor development by blending different inhibitors to promote performance synergies. • The properties of three waxy crude oil were thoroughly characterised by defined methods. • The effectiveness of polymer based chemical inhibitors on wax crystallization was investigated through viscometric analysis and morphological characterisation. • The synergistic effect as a result of blending different inhibitors leads to the improved efficiency of a new inhibitor.

Phase behavior of solvent-rich compositions of the polymer/drug system poly(butylene succinate) and N,N-diethyl-3-methylbenzamide (DEET)

Poly(butylene succinate) (PBS) is used to produce micro-/nanoporous biodegradable scaffolds, suitable for the release of the mosquito repellent N,N-diethyl-3-methylbenzamide (DEET), based on thermally induced phase separation. For solvent-rich compositions up to 30 m% PBS, it was found that PBS dissolves in DEET at elevated temperatures. During cooling, spherulitic crystallization of PBS occurs, with the crystallization temperature decreasing with the content of DEET and the cooling rate, as determined by cloud-point measurements, differential scanning calorimetry, and polarized-light optical microscopy. Scaffold morphologies of quenched solutions were analyzed by scanning electron microscopy as a function of the polymer concentration and the quenching temperature. These two parameters control the nucleus density/spherulite size, the degree of intermeshing of spherulites, and the intra- and interspherulitic pore size, with the latter typically being of the order of magnitude of few micrometers.Graphical abstractFig.a

Research on the Possible Application of Polyolefin Waste-Derived Pyrolysis Oils for ANFO Manufacturing

This work aims to evaluate the possible application of pyrolysis fuel oils obtained through the pyrolysis of waste plastics. by comparing both the blasting properties and morphology results of Ammonium Nitrate Fuel Oil (ANFO), which is applied in the mining industry, and ANFO based on pyrolysis fuel oils (FOs), as well as low-temperature properties of all tested FO samples. The low-temperature research includes the measurements of density, kinematic viscosity, flash point, pour point, and cloud point. Moreover, a stability analysis was carried out based on the Turbiscan Stability Index (TSI) coefficient. Based on the obtained results it was concluded that despite pyrolysis FOs showing some differences in comparison with index FO, none of their properties indicated that pyrolysis FOs should be excluded from possible application in ANFO. Additionally, IR, XRD, and SEM analyses were conducted for all ANFO samples. The instrumental analysis did not show any dribbling effect. The blasting tests such as velocity of detonation (VOD), the heat of explosion, and post-blast fumes revealed that VOD values were lower in comparison to the reference ANFO sample. However, the observed differences were either negligible (heat of explosion) or small enough (VOD) to conclude that polyolefin waste-derived pyrolysis fuel oils can be applied as ANFO’s fuel component.

Mechanistic differences in the effects of sucrose and sucralose on the phase stability of lysozyme solutions

The effect of two disaccharide analogues, sucrose and sucralose, on the phase stability of aqueous lysozyme solutions has been addressed from a mechanistic viewpoint by a combination of experiment and molecular dynamics (MD) simulations. The influence of the added low molecular weight salts (NaBr, NaI and NaNO3) was considered as well. The cloud-point temperature measurements revealed a larger stabilizing effect of sucralose. Upon increasing sugar concentration, the protein solutions became more stable and differences in the effect of sucralose and sucrose amplified. It was confirmed that the addition of either of the two sugars imposed no secondary structure changes of the lysozyme. Enthalpies of lysozyme-sugar mixing were exothermic and a larger effect was recorded for sucralose. MD simulations indicated that acidic, basic and polar amino acid residues play predominant roles in the sugar-protein interactions, mainly through hydrogen bonding. Such sugar mediated protein-protein interactions are thought to be responsible for the biopreserative nature of sugars. Our observations hint at mechanistic differences in sugar-lysozyme interactions: while sucrose does not interact directly with the protein's surface for the most part (in line with the preferential hydration hypothesis), sucralose forms hydrogen bonds with acidic, basic and polar amino acid residues at the lysozyme's surface (in line with the water replacement hypothesis).

Self-assembly of a short amphiphile in water controlled by superchaotropic polyoxometalates: H4SiW12O40 vs. H3PW12O40

Nanometric ions, such as polyoxometalates (POMs) or ionic boron clusters, with low charge density have previously shown a strong propensity to bind to macrocycles and to adsorb to neutral surfaces: micellar, surfactant covered water–air and polymer surfaces. These association phenomena were shown to arise from a solvent-mediated effect called the (super-)chaotropic effect. We show here by combining cloud point (CP) measurements, scattering (SAXS/SANS) and spectroscopic techniques (NMR) that Keggin POMs: H4SiW12O40 (SiW) and H3PW12O40 (PW), induce the self-assembly of an organic solvent: dipropylene glycol n-propylether (C3P2), in water. The strong interaction between SiW/PW with C3P2 leads to a drastic increase in the CP, and aqueous solubility, of C3P2, e.g. SiW enables reaching full water-C3P2 co-miscibility at room temperature. At high POM concentrations, SiW leads to a continuous increase of the CP, forming SiW-[C3P2]1-2 complexes, whereas PW produces a decrease in the CP attributed to the formation of nearly “dry” spherical [PW]n[C3P2]m colloids, with n ~ 4 and m ~ 30. At high C3P2/PW contents, the [PW]n[C3P2]m colloids turn into large interconnected structures, delimiting two pseudo-phases: a PW-C3P2-rich phase and a water-rich phase. It is proposed that the stronger electrostatic repulsions between SiW (4−), compared to PW (3−), prevents the formation of mesoscopic colloids.

Anti‐cancer combination therapy by co‐delivery of hydrophilic and hydrophobic using dual temperature and pH‐responsive liposomes

A novel combination chemotherapic strategy by co-delivery of doxorubicin (DOX) and mitomycin C (MC) anti-cancers was reported using dual pH and temperature-responsive copolymer-modified liposomes to achieve superior therapeutic efficacy. The copolymer was prepared using temperature-responsive N-isopropylacrylamide and pH-responsive poly-acrylic acid monomers through reversible addition–fragmentation chain transfer polymerisation and revealed dual pH/temperature-dependent phase transitions proved by differential scanning colorimetric and cloud point measurements. With relatively high encapsulation efficiency of 81.2% for DOX and 77.3% for MC, the prepared polymer-modified responsive liposomes (PMRLs) have shown enhanced and controlled temperature/pH-dependent release profiles and significantly lower thermal dose thresholds with up to a 250-fold decrease at pH 7.4 and 1000-fold decrease at pH 5.5 compared to the traditional formulations. The temperature/pH-dependent release profile of the drugs was investigated in vitro and cytotoxicity of the carriers was evaluated using both normal and cancerous cell lines. It was found that the two drugs co-loaded PMRLs were revealed synergistic effects on cytotoxicity of the carriers against Michigan Cancer Foundation-7 breast cancer cells. The results revealed that by this combinational regimen, the prepared liposomes have the potential to dramatically decrease the risk of damage to healthy tissues normally caused by liposomal cancer therapy.

Experimental Investigation of Polymer-Induced Fouling of Heater Tubes in the First-Ever Polymer Flood Pilot on Alaska North Slope

Summary Polymer flooding is being pilot tested for the first time in the Schrader Bluff viscous oil reservoir at the Milne Point Field on Alaska North Slope (ANS). One of the major concerns of the operator is the impact of polymer on the oil production system after polymer breakthrough, especially the polymer-induced fouling issues in the heat exchanger. This study investigates the propensity of polymer fouling on the heater tubes as a function of different variables, with the ultimate goal of determining safe and efficient operating conditions. A unique experimental setup was designed and developed in-house to simulate the fouling process on the heating tube. The influence of heating tube skin temperature, tube material, and polymer concentration on fouling tendency was investigated. Each test was run five times with the same tube, and in each run, the freshly prepared synthetic brine and polymer solution was heated from 77°F to 122°F to mimic field-operating conditions. The heating time and fouling amount were recorded for each run. Cloud point measurement has also been conducted to find the critical temperature at which the polymer in solution becomes unstable and precipitates out. The morphology and composition of the deposit samples were analyzed by environmental scanning electron microscopy (ESEM) and X-ray diffraction (XRD), respectively. It was found that the presence of polymer in produced fluids would aggravate the fouling issues on both carbon steel and stainless steel surfaces at all tested skin temperatures. Only higher skin temperatures of 250°F and 350°F could cause polymer-induced fouling issues on the copper tube surface, and the fouling tendency increased with polymer concentration. At the lower skin temperatures of 165°F, no polymer-induced fouling was identified on the copper tube. A critical temperature that is related to the cloud point of the polymer solution was believed to exist, below which polymer-induced fouling would not occur and only mineral scale was deposited but above which the polymer would aggravate the fouling issue. The cloud point of the tested polymer solution was determined to be between 220°F and 230°F. From a practical safer design standpoint, we recommend a value of 220°F for operational purposes on the pilot site. The heating efficiency of the tube would be decreased gradually as more fouling material accumulates on its surface. If polymer precipitated and deposited on the surface, it would bond to the mineral crystals to form a robust three-dimensional network structure, resulting in a rigid polymer-induced fouling. The study results have provided practical guidance to the field operator for the ongoing polymer flooding pilot test on ANS.

Blending modification to porous polyvinylidene fluoride (PVDF) membranes prepared via combined crystallisation and diffusion (CCD) technique

PVDF membranes prepared by the combined crystallisation and diffusion (CCD) technique, a variation of ice templating, have shown permeation rates far superior to those made via conventional methods such as nonsolvent induced phase separation (NIPS) or thermally induced phase separation (TIPS). However, so far the smallest pore size achieved for PVDF membranes prepared by CCD is about 30 nm. In this study, the pore size of CCD PVDF membranes is reduced to 15 nm by blending poly(methyl methacrylate) (PMMA) into PVDF-dimethyl sulfoxide (DMSO) dope solutions without altering the operational conditions. Systemic study shows the pore size reduces when increasing PMMA concentration in the membranes; but after an initial drop compared to the pure PVDF membrane, the pure water flux doesn't decline with PMMA concentration. The effect of different molecular weights of PMMA (120 kDa and 35 kDa) was also investigated, where the results showed a smaller pore size for membranes prepared using the higher molecular weight PMMA. Scanning electron microscopy (SEM), cloud-point temperature measurement and Fourier transform infrared spectroscopy (FTIR) was used to characterise the membranes and help understand how PMMA affects membrane formation. From the evidence gathered, we attribute the effects of PMMA to the change in the number of nucleation centres, diffusional rates, as well as the gelation point based on a previously proposed CCD mechanism.

Influence of electrolytes on the cloud point phenomenon of tween-80+lomefloxacin hydrochloride mixtures and their thermodynamic parameters

Herein, the interaction between Tween-80 (Tw-80) and antibiotic drug lomefloxacin hydrochloride (LMFH) has been studied through the cloud point (CP) measurement of Tw-80 + LMFH mixtures in the absence/attendance of electrolytes. Tw-80 is used for different formulations of drugs and foods. LMFH is widely prescribed for the treatment of numerous bacterial infections. The cloud point (CP) values of Tw-80 + LMFH mixture were determined and found to reduce with the augmentation of concentration of LMFH. The occurrence of salts reduces the CP of the Tw-80 + LMFH mixture which further enhances with an increase of salt concentration. The effectiveness of electrolytes in decreasing CP of Tw-80 + LMFH mixture was obtained to be followed the order: CPNaCl < CPNa2SO4 < CPNa3PO4. 12 H2O which reveal that Na3PO4. 12 H2O is the most effective CP suppressor. The Gibbs free energy (∆Gco) value was achieved positive in entire systems and the positive ∆Gco value was lowered in the salt medium. The ∆Gco values were also dwindled through the augmentation of LMFH/electrolytes content in the solution. The enthalpy (∆Hco) and entropy (∆Sco) value of this system was found to be negative which drops with the rise of LMFH/electrolytes content. In addition, different thermodynamic properties of transfer along with entropy-enthalpy compensation was computed to clarify the interaction between Tw-80 and LMFH.

Functional cellulose nanocrystals containing cationic and thermo-responsive polymer brushes

Cationic and thermo-responsive polymer brushes were grafted from the surface of cellulose nanocrystals. Di(ethylene glycol) methyl ether methacrylate (MEO2MA) and poly(oligoethylene glycol) methyl ether acrylate (OEGMA300) and (2-methacryloyloxyethyl) trimethylammonium chloride (DMC) were grafted from cellulose nanocrystals (CNCs) via free radical polymerization. The CNC-g-POEGMA (CP) possessed a tunable lower critical solution temperature (LCST) of about 50 °C, and cloud point measurements confirmed that the LCST of the nanoparticles could be manipulated within the range of 40−47 °C by adjusting the DMC content. The salt effect was also investigated, and the results revealed a typical salting-out effect for the CNC-g-POEGMA after the introduction of KCl. On the other hand, the CNC-g-POEGMA-g-DMC (CPD) copolymers displayed two salt-responsive characteristics; polyelectrolyte effect at lower salt concentrations, followed by the salting-out effect at higher salt concentrations, which is dependent on the DMC content.