Polymer Solutions Research Articles

ON WEAK SOLVABILITY OF MATHEMATICAL MODEL DESCRIBING THE MOTION OF POLYMER SOLUTIONS WITH MEMORY

The weak solvability of the initial-boundary value problem describing the motion of weakly concentrated aqueous polymer solutions taking into account the memory of the fluid is considered in the paper. In this model the memory is considered along the trajectory of fluid particles, determined by the velocity field. The topological approximation approach and the theory of regular Lagrangian flows are used.

Dynamics of Nanoparticles in Solutions of Semiflexible Ring Polymers.

We use hybrid molecular dynamics-multiparticle collision dynamics (MD-MPCD) simulations to investigate the influence of chain stiffness on the transport of nanoparticles (NPs) through solutions of semiflexible ring polymers. The NPs exhibit subdiffusive dynamics on short time scales before transitioning to normal diffusion at longer times. The terminal NP diffusivity decreases with increasing ring stiffness, similar to the behavior observed in solutions of semiflexible linear chains. The NP subdiffusive exponent is found to be strongly correlated with that of the polymer center of mass (COM) for the range of chain stiffnesses examined, which is at odds with the pronounced decoupling of the NP and polymer COM motions previously observed upon increasing the stiffness of linear chains. Our analysis indicates that these marked differences in the intermediate dynamics are rooted in distinct structural changes that emerge with increasing bending stiffness: Stiffer ring polymers adopt increasingly circular conformations and stack into transient tubes. The void space created near the ring centers is occupied by NPs and other polymers, resulting in strong dynamic coupling on short time scales.

A swimming bacterium in a two-fluid model of a polymer solution

A swimming bacterium in a two-fluid model of a polymer solution

Transition path time over a barrier of a colloidal particle in a viscoelastic bath

We experimentally study the statistics of the transition path time taken by a submicron bead to successfully traverse an energy barrier created by two optical tweezers in two prototypical viscoelastic fluids, namely, aqueous polymer and micellar solutions. We find a very good agreement between our experimental distributions and a theoretical expression derived from the generalized Langevin equation for the particle motion. Our results reveal that the mean transition path times measured in such viscoelastic fluids have a nontrivial dependence on the barrier curvature and they can be significantly reduced when compared with those determined in Newtonian fluids of the same zero-shear viscosity. We verify that the decrease of the mean transition path time can be described in terms of an effective viscosity that quantitatively coincides with that measured by linear microrheology at a frequency determined by the reactive mode that gives rise to the unstable motion over the barrier. Therefore our results uncover the linear response of the particle during its thermally activated escape from a metastable state even when taking place in a non-Markovian bath. Published by the American Physical Society 2024

Experimental Investigation of Spray Drying Breakup Regimes of a PVP-VA 64 Solution Using High-Speed Imaging

Background: Atomization plays a key role in spray drying, a process widely used in the pharmaceutical, chemical, biological, and food and beverage industries. In the pharmaceutical industry, spray drying is particularly important in the preparation of amorphous solid dispersions, which enhance the bioavailability of active pharmaceutical ingredients when mixed with a polymer. Methods: In this study, a 3D-printed adaptation of a commercial spray dryer nozzle (PHARMA-SD® PSD-1, GEA Group AG) was used to investigate the atomization of PVP-VA 64 polymer solutions under varying flow conditions using high-speed diffuse back-illumination. Results: Unlike pure water, the atomization process of the polymer solution was governed by viscous effects rather than surface tension, as indicated by stringing effects in the liquid core and the formation of larger droplets. In addition, the classical Ohnesorge diagram accurately predicted the atomization regime with increasing Reynolds numbers and could be modified to reasonably predict the breakup regime by considering the transitions between regime boundaries. Conclusions: The use of such a modified diagram facilitates the efficient selection of viscous fluid solutions and process parameters to achieve complete spray formation.

Elastoinertial stability analysis and structure formation in viscoelastic subdiffusive pipe flow

The modal temporal stability analysis of viscoelastic, subdiffusive, pressure driven, axisymmetric pipe flow, representing thick polymer solutions, exhibits the presence of temporally stable regions at high fluid inertia. The stress constitutive equation, previously derived for channel flows [Chauhan et al., Phys. Fluids 35(12), 123121 (2023)] is the fractional variant of the upper convected Maxwell equation. The parameters governing the stability are the Reynolds number, Re=ρU0R0η0, the elasticity number, El=λαη0ρR02, and the ratio of the solvent to the polymer solution viscosity, ν=ηsη0, where R0,U0,ρ,λ,α are the pipe radius, the maximum mean flow velocity, density, the polymer relaxation time, and the fractional order of the time derivative, respectively. The neutral curves indicate, in the limit of small elasticity numbers or in the limit when the viscosity ratio approaches unity, El(1−ν)≪1, that the critical Reynold number, Rec diverges as Rec∼[(1−ν)El]−3α/2, while the critical wavenumber, kc increases as kc∼[(1−ν)El]−α/2. Using a novel fractional variant of the pressure correction method as well as a metric in the Riemannian manifold of symmetric positive definite conformation tensors, the direct numerical simulations quantify the formation of spatiotemporally stable macrostructures (or the non-homogeneous regions of high viscosity) at moderate inertia, thereby corroborating the qualitative features of the experimentally observed flow-instability transition of subdiffusive axisymmetric pipe flows.

Quantification of Amlodipine Maleate Content in Amorphous Solid Dispersions Produced by Fluidized Bed Granulation Using Process Analytical Technology Tools

Background: Active pharmaceutical ingredient (API) content is a critical quality attribute (CQA) of amorphous solid dispersions (ASDs) prepared by spraying a solution of APIs and polymers onto the excipients in fluid bed granulator. This study presents four methods for quantifying API content during ASD preparation. Methods: Raman and three near-infrared (NIR) process analysers were utilized to develop methods for API quantification. Four partial least squares (PLS) models were developed using measurements from three granulation batches, with an additional batch used to evaluate model predictability. Models performance was assessed using metrics such as root mean square error of prediction (RMSEP), root mean square error of cross-validation (RMSECV), residual prediction deviation (RPD), and others. Results: Off-line and at-line NIR models were identified as suitable for process control applications. Additionally, at-line Raman measurements effectively predicted the endpoint of the spraying phase. Conclusions: To the best of authors’ knowledge, this is the first study focused on monitoring API content during fluidized bed granulation (FBG) used for ASD preparation. The findings provide novel insights into the application of Raman and NIR process analysers with PLS modelling for monitoring and controlling ASD preparation processes.

Elongational flow of arrested complex fluid under the suppression of osmotic effective diffusion by surrounding flow of miscible solvent

Nonequilibrium interface (NI) of miscible fluids has long been of great interest; however, the acting effective interfacial tension and the deformation rate of the suspended phase in a steady immiscible state (SIS) have yet been delineated. We investigate the deformation rate and diffusion of complex fluids with a miscible surrounding fluid in a rectangular microchannel. We show here that the NI acts as a moving osmotic membrane and maintains a stable two-phase flow at a flow rate faster than the diffusion rate proportional to the osmotic pressure of the complex fluid. We report for the first time that a complex fluid suspended within a flow rate faster than the osmotic diffusion rate exhibits wet capillary thinning (WCT) behavior at the SIS. We demonstrate that either acting effective interfacial tension caused by Korteweg stress or elongational viscosity is measurable from the WCT behavior, and it was shown to be applicable to polymer solutions, animal blood, and even pure water. Our findings provide new insight into the phase behavior and managing diffusion in the flow stream of miscible fluids. The WCT technique enables precise measurement of elongational viscosity of a small amount of complex fluid, about the size of a drop without contact with the gas phase, providing a safe method for toxic, gas reactive liquid, or infected biofluids.

Rheology of polyacrylamide-based fluids and its impact on proppant transport in hydraulic fractures

Rheological experiments and measurements of particle settling velocity under static conditions were conducted for two types of polyacrylamide (PAA-based) fluids. The flow behavior of the viscoelastic fluids is described by a simplified, three-parameter model that integrates a constant viscosity at low shear rates with a power-law viscosity dependency at higher shear rates. The estimated dependencies of the rheological parameters and particle settling velocity on PAA concentration align with the classical power-law scaling for semi-dilute polymer solutions. The identified scaling offers valuable insight for optimizing the chemical composition of fracturing fluids, thereby improving the efficiency of hydraulic fracturing technology. By applying the lubrication approximation to the Navier–Stokes equations, a set of equations for the suspension flow in a vertical plane channel, characterized by the three-parameter rheology model, was derived. In typical fracturing conditions, the conventional power-law viscosity model used in current fracturing simulators significantly overestimates the gap-averaged apparent fluid viscosity compared to the proposed model. The novel model of the suspension flow aims to enhance the accuracy of proppant transport models applied in hydraulic fracturing simulators. Based on the three-parameter rheology model, a new model of particle settling in the studied PAA-based fluids is developed. It is based on smart Stokes' law, where viscosity is calculated according to either the plateau or power-law region, depending on the self-induced shear rate. The new model more accurately approximates experimentally determined settling velocity of proppant under static conditions across a broad range of PAA concentrations than existing models.

Preparation and Optimization of Gemcitabine Loaded PLGA Nanoparticle Using Box-Behnken Design for Targeting to Brain: In Vitro Characterization, Cytotoxicity and Apoptosis Study

Background: Treatment of glioma with conventional approaches remains a far-reaching target to provide the desired outcome. This study aimed to develop and optimize Gemcitabine hydrochloride- loaded PLGA nanoparticles (GNPs) using the Box-Behnken design methodology. The independent variables chosen for this study included the quantity of Polymer (PLGA) (X1), Tween 80 (X2), and Sonication time (X3), whereas the dependent variables were Particle size (Y1) EE % (Y2) and PDI (Y3). The optimized biodegradable nanoparticles were investigated for their anticancer effectiveness in U87MG human glioblastoma cells in vitro. Method: The formulation process involved two steps. Initially, emulsification was carried out by combining the organic polymer solution with the aqueous surfactant solution. Subsequently, in the second step, the organic solvent was evaporated, resulting in the precipitation of the polymer and the formation of nanoparticles. The quantity of PLGA, Tween 80, and PVA (at a constant concentration) was adjusted based on the experimental trial approach. Subsequently, the PLGA-based nanoparticles underwent characterization, wherein their particle size, encapsulation efficiency, polydispersity index (PDI), and cumulative release were assessed. The optimal formulation composition was determined as 200 mg of PLGA, 4 ml of Tween 80, and 2 mg of PVA. Further, the optimized GNPs were evaluated for their anti-cancer effectiveness on U87 MG cells by MTT and apoptosis assay. Results: The results demonstrated that the optimized GNPs exhibited an encapsulation efficiency of 81.66 %, a particle size of 140.1 nm, and a PDI of 0.37. The morphology of the Opt-GNPs was observed to be spherical through transmission electron microscopy (TEM). Conclusion: The Apoptosis study further confirmed the observations of MTT assay as the Opt- GNPs significantly enhanced the apoptosis in U-87 MG cells than the Standard marketed formulation.

Effects of binary polymer-humic soil amendments on soil carbon cycle and detoxication ability of heavy metal pollution

BackgroundSynthetic hydrophilic polyelectrolytes are considered as perspective tools to optimize soil properties and find increasing applications in agricultural technologies. One possible polyelectrolyte-based soil conditioner that has shown promise for improving soil hydrophysical properties is hydrolyzed polyacrylonitrile (HYPAN), linear polyanion. Combinations of HYPAN with humic substances in binary polymer-humic soil amendment presumably could provide a synergistic impact. In this study we investigated the effects of HYPAN, two different potassium humates (from lignite and lignosulfonate), and binary compositions of HYPAN with humates in the ratios of 1:1 and 1:2, on soil microbiological activity. We applied polymer solutions (0.9% on a dry matter basis) in a lab experiment and examined how they affected soil respiration, microbial biomass, metabolic quotient, and the decomposition rate constant in soil–polymer mixtures. A concurrent set of studies involved spiking soil–polymer mixes with heavy metals (copper, zinc, lead and cadmium).ResultsIn uncontaminated soil–polymer mixtures both humates stimulated the activity of soil microorganisms, expressed in increased basal respiration, microbial biomass, and mitigation of HM toxicity. The effects of binary polymer-humic formulations and HYPAN were comparable to and close in size to those of humates. On the 90th day, humates increased microbial respiration by 54–77% and HYPAN alone by 30%. Binary compositions were more efficient when combined with humate from lignosulphonate. The maximum increase in microbial biomass was obtained with the same humate both in composition and alone (65 and 91 µg C g−1). Under conditions of HM contamination at the end of the incubation, the levels of microbiological parameters in HM spiked soil–polymer mixtures did not statistically differ from the uncontaminated control. Every polymer formulation helped to partially restore microbial activity while reducing the toxic effects of HM. In these circumstances, humate from lignite both by itself and in combination with HYPAN performed better. The quality of organic matter in both humates and HYPAN was the primary determinant of the impact of the examined amendments.ConclusionsCombination of natural humate and synthetic HYPAN stimulated the activity of soil microorganisms, increased their biomass and mitigated the toxicity of heavy metals present in the soil. This allows the use of binary HYPAN-humate formulations to improve the chemical and biological properties of soil and increase its productivity.Graphical

High-filler content electrospun fibers from biodegradable polymers and hydroxyapatite: Toward improved scaffolds for tissue engineering.

One of the key challenges in tissue engineering area is the creation of biocompatible scaffolds that support cell growth and mimic the structural and mechanical properties of native tissues. Among various materials used for scaffold fabrication, composite materials based on biodegradable polymers reinforced with bioactive inorganic fillers have attracted significant attention due to their properties. One of the important problems with the preparation of composite electrospun fibers is the low filler content in the fiber. This study aims to select the best composition for electrospun polymer fibers in terms of potential application in tissue engineering. The effect of the viscosity of polymer solution/dispersion and filler content on the structure and properties of the fibers was determined. Morphology and filler content were compared. Series of electrospun composite fibers were fabricated from poly(ĺ-caprolactone) (PCL), poly(L-lactic acid) (PLLA) and hydroxyapatite (HAP), containing from 10 wt% to 40 wt% HAP. The properties of the resulting composites were studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and viscosimetry measurements. The addition of HAP to the polymer solution caused a significant increase in viscosity, but the results showed that it is possible to obtain composite electrospun fibers even with 40 wt% filler content. Scanning electron microscopy analysis shows randomly oriented electrospun fibers with an average diameter in the range of 3.8-8.5 ěm for solution and dispersion with high viscosity (1,210-2,000 mPa·s) and significantly larger diameters (approx. 12 ěm) for the PCL solution (326 mPa·s). It is possible to transform the composite dispersion from biopolymers and HAP into nonwoven fabrics at up to 40 wt% filler content. Due to their unique properties, such materials are promising for application in tissue engineering.

Fabrication of PBAT Membranes with High Separation Accuracy Based on Inverse-Opal-Structural Photonic Crystals.

Membrane technology is one of the most effective ways to cope with the filtration and separation. However, most polymer membranes are not uniform in pore size and have wide pore size distributions and low porosities, which restrict their application. A high-porosity homogeneous membrane with high filtration accuracy is an effective solution. Photonic crystals (PCs) with an inverse-opal (IO) structure provide a new way for preparing high-porosity homogeneous porous membranes. In this study, a rapid shear-induced assembly method for preparing biodegradable poly(butylene adipate-co-terephthalate) (PBAT) membranes based on PCs with an IO structure was proposed, and the design principles of the IO-structured PBAT membrane were investigated. Moreover, the effects of polymer solution concentrations, solvent evaporation temperature, and SiO2/PBAT mass ratio on the SiO2/PBAT PC structure, formation mechanism of shear-induced assembly, and the filtering efficiency of resultant PBAT membranes for solid-liquid separation were investigated. The study underscored the point that when the polymer concentration is in the range of 15-20 wt % and the drying temperature is at 80 °C, as the SiO2-to-PBAT mass ratio increases, the pore of the membrane increases, the porosity is as high as to 84.11%, and pure water flux is up to 756.19 L m-2 h-1. After five cycles, the rejection rate of PBAT membranes for the contaminant still reached more than 99%. This study proposes a simple and rapid method for constructing an IO-structured membrane that is expected to address challenges encountered in achieving efficient and high-precision separation.

Keplerian turbulence in Taylor–Couette flow of dilute polymeric solutions

Turbulent flow induced by elastorotational instability in viscoelastic Taylor–Couette flow (TCF) with Keplerian rotation is analogous to a turbulent accretion disk destabilized by magnetorotational instability. We examine this novel viscoelastic Keplerian turbulence via direct numerical simulations (DNS) for the shear Reynolds number ( $Re$ ) ranging from $10^2$ to $10^4$ . The observed characteristic flow structure consists of penetrating streamwise vortices with axial length scales much smaller than the gap width, distinct from the classic centrifugally induced Taylor vortices, which have axial lengths of the gap width. These intriguing vortices persist for the wide $Re$ range considered and give rise to intriguing scaling behaviour in key flow quantities. Specifically, the characteristic axial length of the penetrating vortices is shown to scale as $Re^{-0.22}$ ; the angular momentum transport scales as $Re^{0.42}$ ; the kinetic and elastic boundary-layer thicknesses based on angular velocity and hoop stress near the inner cylinder wall scale as $Re^{-0.48}$ and $Re^{-0.49}$ , respectively. This implies that the viscoelastic Keplerian turbulence belongs to the classical turbulent regime of TCF with the Prandtl–Blasius-type boundary layer. Furthermore, we present an analytical relation between the viscous and elastic dissipation rates of kinetic energy and the angular momentum transport and in turn demonstrate its validity using our DNS data. This study has paved the way for future research to explore astrophysics-related Keplerian turbulence and angular momentum transport via the scaling relations of the analogous TCF of dilute polymeric solutions.

Binary composite depolymerization system targeting polymer injection wells: A fusion of experiment and mechanism

With the continuous development and application of polymer flooding technology, the problem of polymer injection well blockage has become increasingly severe, and various plugging removal technologies have emerged. This paper studies the depolymerization agent system, aiming at the blockage problem caused by the injection of polymer HLCHEM-P01 in the mine. The depolymerization agent system is evaluated through gel chromatography analysis, corrosion evaluation, pH sensitivity evaluation, and core displacement experiment. Finally, an efficient, safe, low corrosion and reliable binary compound depolymerization agent system was obtained. It can almost wholly degrade the polymer solution after 90 min. Analyze the mechanism of action of the binary compound depolymerization agent system, which involves specific antagonistic or synergistic interactions. The overall oxidation performance of mixed chemical agents is not just a simple superposition of the oxidation performance of individual chemical agents. The application effect of the depolymerization agent system is significant, and the core permeability recovery reaches over 90%. Effectively solving blockage problems can help improve oilfield efficiency and increase crude oil recovery.

Separation of sticker-spacer energetics governs the coalescence of metastable condensates.

A key conundrum of biological condensates is the coexistence of multiple droplets, in direct variance with classical predictions of mean-field theories of polymer solutions. Our current study uncovers that the merging of sticker-spacer condensate is an entropy driven process, as opposed to the surface energy driven fusion that are observed for canonical liquid droplets. This entropy, stemming from the inter-condensate polymer exchange, makes the droplet merging process dependent on inter-sticker dissociation kinetics. Stronger inter-sticker interaction triggers a kinetic arrest, preventing the condensate merger even at a low density. Our prediction starkly correlates with recent experimental findings on protein-RNA condensates in vitro and in vivo, highlighting the biological relevance of the interplay of kinetics and thermodynamics.

Preparation and characterization of Pistacia atlantica oleo-gum-resin-loaded electrospun nanofibers and evaluating its wound healing activity in two rat models of skin scar and burn wound.

A growing body of research is dedicated to developing new therapeutic agents for wound healing with fewer adverse effects. One of the proceedings being taken today in wound healing research is to identify promising biological materials that not only heal wounds but also vanish scarring. The effectiveness of nanofibers like polyvinyl alcohol (PVA), in improving wound healing can be related to their unique properties. Pistacia atlantica Desf. subsp. kurdica (Zohary) Rech. f. (PAK) [Anacardiaceae], also known as "Baneh" in traditional Iranian medicine, is one of the most effective herbal remedies for the treatment of different diseases like skin injuries due to its numerous pharmacological and biological properties, including anti-inflammatory, antioxidant, and anti-bacterial effects. Our study aimed to evaluate the wound-healing activity of nanofibers containing PVA/PAK oleo-gum-resin in two rat models of burn and excision wound repair. PVA/PKA nanofibers were prepared using the electrospinning method. Scanning electron microscope (SEM) images and mechanical properties of nanofibers were explored. Diffusion and releasing experiments of nanofibers were performed by the UV visible method at different time intervals and up to 72h. The animal models were induced by excision and burn in Wistar rat's skin and the wound surface area was measured during the experiment for 10 and 21days, respectively. On the last day, the wound tissue was removed for histological studies, and serum oxidative factors were measured to evaluate the antioxidant properties of the PVA/PKA. Data analysis was performed using ImageJ, Expert Design, and statistical analysis methods. PVA/PKA nanofibers were electrospun at different voltages (15, 18, and 20kV). The most suitable fibers were obtained when the nozzle was positioned 15cm away from the collector, with a working voltage of 15kV, and an injection rate of 0.5mm per hour, using the 30:70 w/v PKA gum. In the SEM images, it was found that the surface tension of the polymer solution decreased by adding the gum and yield thinner and longer fibers at a voltage of 15kV with an average diameter of 96 ± 24nm. The mechanical properties of PVA/PKA nanofibers showed that the presence of gum increased the tensile strength and decreased the tensile strength of the fibers simultaneously. In vivo results showed that PVA/PKA nanofibers led to a significant reduction in wound size and tissue damage (regeneration of the epidermal layer, higher density of dermal collagen fibers, and lower presence of inflammatory cells) compared to the positive (phenytoin and silver sulfadiazine) and negative control (untreated) groups. Wound contraction was higher in rats treated with PVA/PKA nanofibers. Additionally, antioxidative serum levels of catalase and glutathione were higher in the PVA/PKA nanofiber groups even in comparison to positive control groups. Pistacia atlantica oleo-gum-resin-loaded electrospun nanofibers potentially improve excision and burn models of skin scars in rats through antioxidative and tissue regeneration mechanisms.

Preserving large-scale features in simulations of elastic turbulence

Simulations of elastic turbulence, the chaotic flow of highly elastic and inertialess polymer solutions, are plagued by numerical difficulties: the chaotically advected polymer conformation tensor develops extremely large gradients and can lose its positive-definiteness, which triggers numerical instabilities. While efforts to tackle these issues have produced a plethora of specialized techniques – tensor decompositions, artificial diffusion, and shock-capturing advection schemes – we still lack an unambiguous route to accurate and efficient simulations. In this work, we show that even when a simulation is numerically stable, maintaining positive-definiteness and displaying the expected chaotic fluctuations, it can still suffer from errors significant enough to distort the large-scale dynamics and flow structures. We focus on two-dimensional simulations of the Oldroyd-B and FENE-P equations, driven by a large-scale cellular body forcing. We first compare two positivity-preserving decompositions of the conformation tensor: symmetric square root (SSR) and Cholesky with a logarithmic transformation (Cholesky-log). While both simulations yield chaotic flows, only the latter preserves the pattern of the forcing, i.e. its fluctuating vortical cells remain ordered in a lattice. In contrast, the SSR simulation exhibits distorted vortical cells that shrink, expand and reorient constantly. To identify the accurate simulation, we appeal to a hitherto overlooked mathematical bound on the determinant of the conformation tensor, which unequivocally rejects the SSR simulation. Importantly, the accuracy of the Cholesky-log simulation is shown to arise from the logarithmic transformation. We also consider local artificial diffusion, a potential low-cost alternative to high-order advection schemes. Unfortunately, the artificially enhanced diffusive smearing of polymer stress in regions of intense stretching substantially modifies the global dynamics. We then show how the spurious large-scale motions, identified here, contaminate predictions of scalar mixing. Finally, we discuss the effects of spatial resolution, which controls the steepness of gradients in a non-diffusive simulation.

Production of activated biocarbons by microwave-assisted chemical activation of hardwood sawdust and their application in the simultaneous removal of polymers of different origins from aqueous systems

Sawdust from deciduous trees was used as a raw material for the preparation of carbonaceous adsorbents. Microwave-assisted chemical activation with K2CO3 and H3PO4 was used to produce materials with a well-developed porous structure. The obtained activated biocarbons were characterized in terms of their porous structure, elemental composition, morphology, thermal stability, as well as surface and electrokinetic properties. The sorption abilities of both materials towards synthetic (poly(acrylic acid)) and natural (lysozyme) polymers in the process of their removal from aqueous systems were determined. Both single adsorbates and mixed solutions of two polymeric adsorbates were tested. The stability of aqueous suspensions containing activated biocarbons and one or two polymers was also determined. As a result of microwave-assisted chemical activation two carbonaceous adsorbents were obtained, characterized by a very well-developed specific surface area (1093–1777 m2/g), a completely different type of porous structure (mesoporous or microporous), and the acidic nature of the surface. The maximum adsorption of poly(acrylic acid) was obtained from a mixed solution of both polymers and it reached values of 379 mg/g (for the sample activated with H3PO4 with mean pore diameter 3.04 nm and minimal contribution of micropores—0.3%) and 259 mg/g (for K2CO3 activated material characterized by the mean pore diameter equal to 1.72 nm and large contribution of micropores—77.4%). In the case of lysozyme, the adsorption efficiency was two times lower (sorption capacity of 127–166 mg/g). Based on the collective data analysis, it can be stated that the most probable mechanisms of polymeric destabilization (highly desirable in separation from the multicomponent solutions) are surface charge neutralization at pH 3 and bridging flocculation at pH 11 (especially for the systems containing material activated with H3PO4 and poly(acrylic acid)).

Crosslinked lignin starch copolymer as a sustainable and thermally stable drilling fluid controller

Fluid loss is a well-known challenge of drilling operations. In this work, a novel sustainable starch-lignin-based polymer was synthesized for possible use in drilling fluid applications. The X-ray photoelectron spectroscopy (XPS) analysis confirmed that kraft lignin was crosslinked with starch via ether covalent bonds. The X-ray diffraction (XRD) analysis confirmed the loss of crystallinity in starch and emerging of new amorphous structures in crosslinked starch-lignin (CSL) polymers after crosslinking with lignin. The incorporation of lignin and new covalent ether bonds improved the thermal stability of starch. The CSL had a rougher surface morphology, higher hydrophilicity, and significantly higher water absorption than starch. CSL-2, with its higher lignin content, demonstrated higher hydrophilicity, better water absorption capacity, and thermal stability than CSL-1. The rheology analysis of the CSL-2 polymer suggested that crosslinking starch with lignin would increase G′ more than G" and reduce tan δ of the polymer solution, resulting in more elastic properties and more stability against the angular frequency. Due to its improved swelling, thermal, and rheological properties as compared to native starch, the produced sustainable lignin-starch copolymer could be used as a new viscosity and rheology modifier, such as a fluid loss controller for oil extraction from wells.