Search Results (90)

Stabilizing micron-sized particles in low-viscosity polymer dispersions is challenging when density differences are present. This study demonstrates that graphite particles in aqueous polyurethane dispersions can be efficiently prevented from sedimentation using the capillary suspension concept. Capillary suspensions are solid/liquid/liquid systems and the capillary forces inferred from adding a second immiscible fluid can lead to drastic changes in texture and flow. Here, both spherical and flake-shaped graphite particles were used as fillers, with octanol as the secondary liquid. At low graphite concentrations, octanol increases the low-shear viscosity significantly attributed to the formation of loose particle aggregates immobilizing part of the continuous phase. Above a critical graphite concentration, capillary forces induce a self-assembling, percolating particle network, leading to a sharp yield stress increase (>100 Pa). The corresponding percolating particle network efficiently suppresses sedimentation; for the system including 28 vol% spherical particles, a shelf life of at least six months was achieved. Capillary forces do not affect the high-shear viscosity of suspensions; here, a hydrophobically modified polyether thickener can be used. Transfer of the stabilization concept presented here to other high-density particles like silver or metal oxides suspended in other polymer dispersions is straightforward and is applicable in various fields like flexible printed electronics. Full article

The experiments in this study investigated the toxicity of naphthenic acids (NAs) on the algal culture Spirulina platensis. The tests monitored the progression of the algal suspension in media contaminated with various concentrations of naphthenic acids. The evolution of the algal culture during the metabolism of NAs was investigated. The monitoring also included the determination of the values of some parameters during the biodegradation process (pH, conductivity, cell viability, dissolved oxygen). Optical density measurements (OD₆₀₀) were used to quantify the growth of Spirulina platensis, alongside the determination of the sedimentation index (IS). Cell viability was assessed microscopically using TEM and optical microscopy. The results facilitated the estimation of the percentage of cell growth inhibition and the inhibitory concentration value, determined by estimating ECb50 (concentration of NAs corresponding to 50% inhibition). The chemical quantification of naphthenic acids in the samples analyzed was performed by calculating the acidity value (AV) and characterizing the naphthenic acids through FTIR analysis. The graphical representation of ECb50 was established by extrapolating to a concentration of 110 mg/mL of naphthenic acids. We have demonstrated that pollution caused by NAs can be mitigated by the algae Spirulina platensis, which can metabolize these compounds and thus biodegrade them. Full article

Functional polymeric materials play a critical role in optimizing flocculation and sedimentation processes in mining tailings, where complex interactions with mineral surfaces govern polymer performance. This study examines the structure–performance relationship, which describes how the internal structure of aggregates (e.g., compactness, porosity and fractal dimension) influences sedimentation behavior, specifically for anionic polyacrylamide (SNF 704) in kaolin-quartz-pyrite suspensions at a pH of 10.5. Using focused beam reflectance measurement (FBRM) and static sedimentation tests, we demonstrate that pyrite exhibits the highest flocculant adsorption capacity, inducing a train-like polymer conformation on its surface. This reduces the formation of effective polymeric bridges, resulting in less compact and more porous aggregates that negatively impact sedimentation rates. Increasing the flocculant dosage improves the capture of fine particles; however, at high pyrite concentrations, rapid saturation of adsorption sites limits flocculation efficiency. Additionally, the fractal dimension of the aggregates decreases with increasing pyrite content, revealing more open structures that hinder consolidation. These findings underscore the importance of optimizing polymer dosage and tailoring flocculant design to the mineralogical composition, thereby enhancing water recovery and sustainability in mining operations. This study highlights the role of structure–property relationships in polymeric flocculants and their potential for next-generation tailings management solutions. Full article

Objective: This manuscript describes an innovative, non-destructive, high-throughput method for the quantification of aluminum hydroxide in aluminum-adjuvanted vaccines, eliminating the need of reagents and providing real-time results. The method is based on a spectrophotometric principle, and several model proteins were studied and tested with the aim to simulate the behavior of aluminum-adjuvanted antigens. Methods: As a proof of concept, the MenB vaccine was used, and the titration of aluminum hydroxide (AH) with ethylenediaminetetraacetic acid (EDTA) was used as an orthogonal reference, as it is one of the current release methods for the content determination of aluminum-hydroxide-adjuvanted vaccine drug products (DPs). The factors influencing the spectrophotometric analysis, such as different plate 96/well containers, variation in the sedimentation of the suspension due to component addition errors during formulation, and batch-to-batch variation were studied to assess the method’s robustness. Five concentration levels (ranging from 2.0 to 4.0 mg/mL AH) with two different batches of aluminum hydroxide were each measured with independent preparations performed by three different operators, for a total of four sessions/operator and 20 formulations/session. An in-depth statistical study was carried out with generated data to assess the precision (in terms of intermediate precision and repeatability), accuracy, linearity, and specificity of the method. Results: The novel spectrophotometric method and the official release one (potentiometric) yielded comparable results, demonstrating the potential of this new method as a release test for AH-adjuvanted products. A simple calibration curve enabled the measurement of samples in a 96-well plate in just a few minutes. Conclusions: We developed a novel method for Aluminum concentration determination in Aluminum-containing pharmaceutical products, like alum-adjuvanted vaccines. This method is fast, completely automatable, and as precise and accurate as already-in-place release methods. Full article

Diatoms are critical indicators in marine paleoecology and contemporary ecosystem studies, yet the accuracy of diatom analysis depends on effective purification methods. Current screening and purification techniques often yield low accuracy. This study introduces a multi-stage screening purification method that integrates both physical and chemical techniques to enhance the extraction of diatom remains from marine sediments, thereby improving the reliability of subsequent analysis. Using surface sediment samples from the Pacific Ocean, we compared the effectiveness of three purification methods: heavy liquid suspension purification, single-layer screening purification, and the newly developed multi-stage screening purification method. The study aimed to evaluate the impact of each method on diatom abundance, valve size distribution, and the accuracy of taxonomic identification. The results revealed that the multi-stage method significantly improved the accuracy of diatom abundance calculation. With this method, diatom abundance was 21.9 times higher than that obtained using the heavy liquid suspension method and 6.5 times higher than that obtained using the single-stage method. This method also proved to be cost-effective, easy to use, and produced samples with low impurity levels, which enhanced microscopic observation, identification, and the reliability of taxonomic statistics. Key factors influencing diatom abundance included sieve pore size, heavy liquid concentration, and valve size and density, while the type of acid and oxidant had minimal effect. Additionally, the multi-stage screening method facilitated the classification of diatoms into various size categories, providing a comprehensive view of diatom size distribution, including nano-sized diatoms (diameter < 20 μm) that are often overlooked in traditional studies. These findings demonstrate that the multi-stage screening purification method is an effective tool for improving the analysis of diatom remains in sediments, potentially refining the accuracy of diatom-based environmental investigations and paleoceanographic reconstructions. Full article

High dewatering costs, resulting from the harvesting and separation of microalgae from the cultivation medium, pose a significant challenge to the large-scale commercial production of algae-based products, accounting for 20–60% of total cultivation expenses. This study presents research findings on the recovery of Baltic green microalgae Chlorella vulgaris BA-167 from water under static sedimentation conditions, evaluating its potential as a cost-effective harvesting method. The study investigates the effect of suspension concentration on the kinetics and efficiency of sedimentation under both autoflocculation and targeted flocculation conditions, using the Flokor 1.2A coagulant, which is commonly employed in industrial water treatment processes in Poland. The novelty of this research lies in the application of the new coagulant Flokor 1.2A to explore its potential for harvesting Chlorella vulgaris BA-167 cultivated under laboratory conditions. The results demonstrate a strong correlation between the algae removal rate and their initial concentration in the suspension, within the range of 0.375–2.380 g/L. Under autoflocculation conditions, the final minimum algae concentration in the liquid after sedimentation ranged from 0.078 to 0.148 g/L, corresponding to initial concentrations of 0.960 g/L and 0.615 g/L, respectively. Experimental results indicate that combining sedimentation with targeted flocculation significantly increases microalgae harvesting efficiency. Flokor 1.2A facilitates the coagulation and agglomeration of microalgae cells, promoting the formation of larger aggregates (flocs) ranging from 20 μm to 690 μm, which settle more easily during gravity-driven sedimentation. Within the coagulant concentration range (C_F) of 0.01–0.36 g/L, sedimentation time was reduced by 3–7 times, and algae harvesting efficiency exceeded 92%. The greatest reductions in algae concentration occurred with 0.12 g/L of coagulant for 0.615 g/L algae and 0.17 g/L for 0.960 g/L algae, achieving maximum harvesting efficiencies of 83.2% and 92.9%, respectively. These results represent a 2.02–2.53-fold improvement over autoflocculation. Full article

There is currently a critical need for understanding how the response and activity of whole-cell bacterial reporters positioned in a complex biological or environmental matrix are impacted by the physicochemical properties of their micro-environment. Accordingly, a comprehensive analysis of the bioluminescence response of Cd(II)-inducible PzntA-luxCDABE Escherichia coli biosensors embedded in silica-based hydrogels is reported to decipher how metal bioavailability, cell photoactivity and ensuing light bioproduction are impacted by the hydrogel environment and the associated matrix effects. The analysis includes the account of (i) Cd speciation and accumulation in the host hydrogels, in connection with their reactivity and electrostatic properties, and (ii) the reduced bioavailability of resources for the biosensors confined (deep) inside the hydrogels. The measurements of the bioluminescence response of the Cd(II) inducible-lux biosensors in both hydrogels and free-floating cell suspensions are completed by those of the constitutive rrnB P1-luxCDABE E. coli so as to probe cell metabolic activity in these two situations. The approach contributes to unraveling the connections between the electrostatic hydrogel charge, the nutrient/metal bioavailabilities and the resulting Cd-triggered bioluminescence output. Biosensors are hosted in hydrogels with thickness varying between 0 mm (the free-floating cell situation) and 1.6 mm, and are exposed to total Cd concentrations from 0 to 400 nM. The partitioning of bioavailable metals at the hydrogel/solution interface following intertwined metal speciation, diffusion and Boltzmann electrostatic accumulation is addressed by stripping chronopotentiometry. In turn, we detail how the bioluminescence maxima generated by the Cd-responsive cells under all tested Cd concentration and hydrogel thickness conditions collapse remarkably well on a single plot featuring the dependence of bioluminescence on free Cd concentration at the individual cell level. Overall, the construction of this master curve integrates the contributions of key and often overlooked processes that govern the bioavailability properties of metals in 3D matrices. Accordingly, the work opens perspectives for quantitative and mechanistic monitoring of metals by biosensors in environmental systems like biofilms or sediments. Full article

Sustainable development is one of the main directions of modern agriculture. First of all, sustainability in the agricultural sector can be achieved through the possible abandonment of traditional mineral fertilizers. Many decades of using these fertilizers have led to the degradation of arable soils and to soil and environmental pollution. As a result, this causes reductions in yields and the environmental quality of agricultural products and affects the health of the population. An alternative to traditional mineral fertilizers may be the use of innovative organomineral fertilizers obtained from local resources. These include manure, humus, compost, sediments, etc. In recent years, fertilizers obtained from the sapropels of the bottom sediments of lakes have become widespread. Their distinctive feature is the environmental friendliness and completeness of the content of chemical elements and substances necessary for the development and growth of plants. In addition, the methods of obtaining and applying these fertilizers allow us to talk about their effectiveness in use. The range of applications of these fertilizers is diverse, from use in the form of a dry extract applied directly to the soil to the use of liquid suspensions used at various stages of processing and from pre-sowing seed treatment to watering and spraying plants at different periods of vegetation. Moreover, an important aspect is the research work on the variational use of sapropel fertilizers on different crops, with different methods of production and concentrations and at different stages of processing. This publication contains the results of a study of the effect of the obtained innovative sapropel fertilizer on productivity, wheat grain quality, and economic efficiency (Triticum aestivum L.). To identify the optimal concentration of sapropel extract, laboratory studies were carried out to determine the germination energy and germination of wheat seeds of different varieties when they were soaked in various concentrations: 0.4, 0.8, 1.2, 1.6, and 2.0 g/L. The best indicators of germination energy and germination of wheat seeds during treatment with the extract were obtained at a concentration of 1.2 g/L. The research was conducted at an accredited variety testing laboratory. A field experiment was conducted in the fields of the agrobiological station of North Kazakhstan University named after Manash Kozybayev. The treatment of the seeds was carried out by soaking them in sapropel extract to evenly distribute the substance. The scheme of the field experiment included the option of using foliar treatment with a solution of sapropel extract at the tillering stage. As a result of the application of the obtained extract in the field, environmental and socio-economic efficiency was noted. The conducted field studies note its positive effect and effectiveness on the morphological, qualitative, and quantitative indicators of the wheat harvest. In the areas where wheat seeds were pretreated, as well as where foliar treatment with the resulting sapropel suspension was carried out, the best yield indicators were revealed. In these variants of the experiment with pre-sowing and pre-sowing and foliar treatment with the sapropel extract solution, the yield was 3.63 and 3.81 tons per hectare, respectively. The introduction of sapropel extract at the stage of seed treatment before sowing, as well as foliar processing of wheat at the tillering stage, will increase the efficiency and profitability of the agricultural industry and obtain a synergistic effect in the form of socio-economic efficiency and environmental safety of production. In our opinion, this will contribute to the development of sustainable agriculture and the production of environmental products. Full article

The transition to electric vehicles (EVs) has introduced new challenges in lubrication, demanding innovative solutions to ensure consistent performance. One promising approach is the use of nanoparticle additives, which have the potential to improve lubrication performance significantly. However, achieving a stable suspension of these nanoparticles in lubricating oils remains a critical challenge, as suspension stability is essential for maintaining consistent performance and maximizing the benefits of these advanced additives. In this study, carbon nanoparticles (CNPs) were modified with dodecylamine (DDA) to achieve stable suspension in nonpolar fluids. The successful functionalization was confirmed by the FTIR results, which showed characteristic peaks of various bonding. The suspension stability tests demonstrated that DDA-CNPs remained suspended for over 60 days in the Polyalphaolefin (PAO) oil, whereas unmodified CNPs were sedimented within 3–7 days. The rheological behavior was measured under different shear rates and temperatures. Viscosity measurements indicated that DDA-CNPs maintained a lower value compared to base PAO. The lubricants’ friction coefficient (COF) was also determined under various speeds and loads. The addition of DDA-CNPs at a concentration of 0.05 wt.% resulted in a significant reduction in COF, with values decreasing by 26% compared to base PAO oil under a load of 1 N. Additionally, the COF for DDA-CNPs was consistently lower than that of PAO, with reductions ranging from 15% to 18% across all tested speeds. The Stribeck curve further highlighted the improved performance of DDA-CNPs across boundary, mixed, and hydrodynamic lubrication regimes. These findings suggest that DDA-CNPs significantly improve the lubrication performance of PAO oil, making them suitable for advanced lubrication applications in automotive and industrial systems. Full article

Seasonal variations of drainage waters and ochreous products of their discharge from the closed abandoned old gallery at the Grantcharitsa scheelite deposit (Bulgaria) were studied by field and laboratory methods for the period 2019–2023. The drainage is generated under anoxic conditions and is inherently diluted (EC = 100–202 µS/cm) with S (6–12 mg/L), Si (6–22 mg/L), Na (6–10 mg/L), Fe (0.2–3.3 mg/L), and W (0.19–3.5 µg/L), at a pH 4.4–6.5 and temperature 7–11.5 °C, with dissolved oxygen DO (2.1–7.7 mg/L). The concentrations of Fe and W and the pH of the water are variable and reach their maximum values during the dry (autumn) season. It was found that such parameters as pH, Eh, DO, Fe and W content change dramatically at a distance of up to 3 m from the water outlet; the values of pH, DO and Eh are sharply increased with a simultaneous nearly 5–6-times reduction in iron and tungsten content. The decrease in the contents of these elements is associated with the precipitation of ochreous material consisting of nanoscale ferrihydrite with an intermediate structural ordering between 2-line and 6-line ferrihydrite (major phase), hematite, goethite, quartz, montmorillonite and magnetite. The formation of ferrihydrite occurs as a result of abiotic and biotic processes with the participation of iron-oxidizing bacteria. Besides Fe₂O₃ (55.5–64.0 wt.%), the ochreous sediment contains SiO₂ (12.0–16.4 wt.%), SO₃ (1.3–2.4 wt.%), Al₂O₃ (3.1–6.8 wt.%) and WO₃ (0.07–0.11 wt.%). It has been shown that drainage waters and ochreous sediments do not inherently have a negative impact on the environment. The environmental problem arises with intense snowmelt and heavy rainfall, as a result of which the accumulated sediments are washed away and carried in the form of suspensions into the water systems. It is suggested that by providing atmospheric oxygen access to the closed gallery (via local boreholes), it is possible to stop the generation of iron-enriched drainage. Full article

Sedimentation is an undesirable phenomenon that complicates the design of microsystems that exploit dense microparticles as delivery tools, especially in biotechnological applications. It often informs the integration of continuous mixing modules, consequently impacting the system footprint, cost, and complexity. The impact of sedimentation is significantly worse in systems designed with the intent of particle metering or binary encapsulation in droplets. Circumventing this problem involves the unsatisfactory adoption of gel microparticles as an alternative. This paper presents two solutions—a hydrodynamic solution that changes the particle sedimentation trajectory relative to a flow-rate dependent resultant force, and induced hindered settling (i-HS), which exploits Richardson–Zaki (RZ) corrections of Stokes’ law. The hydrodynamic solution was validated using a multi-well fluidic multiplexing and particle metering manifold. Computational image analysis of multiplex metering efficiency using this method showed an average reduction in well-to-well variation in particle concentration from 45% (Q = 1 mL/min, n = 32 total wells) to 17% (Q = 10 mL/min, n = 48 total wells). By exploiting a physical property (cloud point) of surfactants in the bead suspension in vials, the i-HS achieved a 58% reduction in the sedimentation rate. This effect results from the surfactant phase change, which increases the turbidity (transient increase in particle concentration), thereby exploiting the RZ theories. Both methods can be used independently or synergistically to eliminate bead settling in microsystems or to minimize particle sedimentation Full article

In the present work, an investigation on the influence of the chemical environment on the sedimentation behaviour of bentonite suspensions is performed with particular reference to the effect of lime addition on the clay particle arrangement. The role of lime content, cation valence and source of calcium ions is considered in the experimental work. At the microscale, particle interaction is analysed by means of zeta potential measurements. Soil fabric formation during sedimentation and its physical properties are inferred from dynamic light scattering measurements, sedimentation tests and Atterberg limits. The addition of cations to pore water promotes the flocculation of montmorillonite particles favouring the formation of particle aggregates, whose dimension depends on ion valence and concentration. The final height of sediments reflects the combined effect of the mutual interactions among particles and the development of secondary phases due to pozzolanic reactions. The influence of clay mineralogy and its effects on the physical properties of lime-treated bentonite is highlighted by comparison with experimental evidence on lime-treated kaolin. Full article

Research has been conducted on the development of an innovative organomineral fertilizer based on local lake resources as a stimulator of germination and growth of crops, as one of the factors in achieving the goal of environmental sustainability. The results obtained are based on the environmental friendliness of the technology, increasing yields, and obtaining environmentally friendly products. This, in turn, will not only save mineral resources but also make it possible to use the resources from the bottom sediments of local lakes, and their rational extraction will contribute to the sustainable development and restoration of lake ecosystems. This article highlights the results of laboratory and field studies on the use of sapropel extract at the stage of pre-sowing seed treatment obtained by extraction of bottom sediments from lakes in Northern Kazakhstan. Solutions of aqueous alcohol extract of sapropel extract with concentrations of 0.4, 0.8, 1.2, 1.6, 2.0 g/L and table beet seeds (Beta vulgaris L.) of Bordo 237 variety were used as objects of research. Statistical analysis of laboratory experience data, based on the determination of germination energy and seed germination, allowed us to identify the optimal concentration of sapropel working solution for pre–sowing seed treatment—1.6 g/L. The index of germination energy and germination of seeds during pretreatment with sapropel extract of this concentration was 40% and 50%, respectively. This contributed to an increase in germination energy by almost 2 times and in seed germination by more than 40%. Pre-sowing treatment of seeds with sapropel extract at a concentration of 1.6 g/L in a field experiment contributed to the improvement of biometric indicators of beet fruits, such as diameter, length, and weight. The results of the data on fetal weight of the experimental variant compared with the control were 27% higher, and they were 26% and 32% higher compared with other experimental variants. In the experimental group, the highest yield index was also established, which is 2.15 times, or 53%, higher than the control, which emphasizes the effectiveness of pre-sowing seed treatment with the resulting sapropel suspension. A patent of the Republic of Kazakhstan was issued for the method we developed for obtaining a sapropel product for pre-sowing treatment of seeds: “A method for obtaining a sapropel product for pre-sowing treatment of vegetable seeds”. The research presented in the article confirms its effectiveness. The use of this product in pre-sowing seed treatment reduces the number of agrotechnological operations and costs, which makes this method more efficient and economically beneficial for the agricultural industry. Thus, the principle of food security will be implemented, contributing to the preservation of sustainable development and having a positive impact on the health of the population. Full article

Clay minerals have different negative effects on the froth flotation process such as low adsorption of collectors on valuable minerals, increased pulp viscosity, and the reduction in recovery and grade concentrates of copper sulfides. This study aims to evaluate the use of polystyrene-based nanoparticles (NPs) for the froth flotation of chalcopyrite and their ability to mitigate the negative effect of montmorillonite on the recovery of this sulfide. The experimental stage consisted of preparing a type of polystyrene-based nanoparticle (St-CTAB-VI), which was analyzed by dynamic night scattering (DLS) to establish its hydrodynamic size. Then, the effect of NPs on chalcopyrite’s angle’s in the presence and absence of montmorillonite (15%) was evaluated and compared with the contact angle achieved using potassium amyl xanthate (PAX) and a mixture of PAX and NPs. In addition, zeta potential measurements were carried out to investigate the interactions between the chalcopyrite and the montmorillonite or the NPs under fixed concentrations and microflotation tests were performed employing different times to evaluate the chalcopyrite recovery in the presence of montmorillonite, using NPs and mixtures with PAX. Finally, turbidity analysis as a function of time was performed to evaluate the occurrence of sedimentation and flocculation phenomena in suspensions of 15% montmorillonite in the presence and absence of chalcopyrite, nanoparticles, and mixtures of NPs and PAX. The results indicated that the mixture of NPs and PAX contributed to increasing the contact angle of chalcopyrite in the presence of montmorillonite. This can be associated with the presence of molecular and nanometric collectors that generated a higher hydrophobicity on the chalcopyrite particles, contributing to reducing the presence of clay minerals on the mineral surface. In addition, the mixture of NPs and PAX promoted the generation of nanoparticles on the sulfide mineral surface, which helps to detach the slime and facilitate the bubble/mineral attachment step during flotation. Full article

The effect of shear on heat-induced changes in milk protein concentrate suspensions was examined at different pH levels, revealing novel insights into micellar dissociation and protein aggregation dynamics. Milk protein concentrate suspensions, adjusted to pH of 6.1, 6.4, 6.8, or 7.5, underwent combined heat (90 °C for 5 min or 121 °C for 2.6 min) and shear (0, 100, or 1000 s⁻¹) treatment. The fragmentation of protein aggregates induced by shear was evident in the control MPC suspensions at pH 6.8, irrespective of the temperature. At pH 7.5, shear increased the heat-induced micellar dissociation. This effect was particularly pronounced at 121 °C and 1000 s⁻¹, resulting in reduced particle size and an elevated concentration of κ-casein (κ-CN) in the non-sedimentable phase. At pH 6.1 or 6.4, shear effects were dependent on sample pH, thereby modifying electrostatic interactions and the extent of whey protein association with the micelles. At pH 6.1, shear promoted heat-induced aggregation, evidenced by an increase in particle size and a significant decline in both whey proteins and caseins in the non-sedimentable phase. At pH 6.4, shear-induced fragmentation of aggregates was observed, prominently due to comparatively higher electrostatic repulsions and fewer protein interactions. The influence of shear on heat-induced changes was considerably impacted by initial pH. Full article