Flocculation Formation Research Articles

Effect of cetyltrimethylammonium bromide on flocculation and filtration of bentonite suspensions

Separation of bentonite from wastewater is challenging because bentonite, is highly dispersible in water. Using cationic polymer flocculants has a high flocculation effect on bentonite. However, the flocculation mechanism is unclear. In this study, flocculation, filtration, and bentonite adsorption behavior are investigated using cetyltrimethylammonium bromide (CTAB) as cationic small molecule; subsequently, the flocculation mechanism of bentonite is explored. The flocculation effect increases and the filtration time is reduced with increasing CTAB concentration. In particular, when more than 1500 ppm of CTAB is used, the filtration time is reduced to 2–3 min. Bentonite forms secondary flocculates after the formation of primary flocculates with increasing CTAB concentration. Additionally, the adsorption behavior reveals that CTAB is inserted between the layers, and it is excessively adsorbed on the bentonite surface. The increase CTAB concentration was effective in improving the shortening the filtration time owing to the formation of large bentonite flocculates.

Foam-stability enhancement in biochar-infused foam concrete: Analyzing ionic strength, interparticle distance, and water state

Foam concrete boasts widespread applications in backfill engineering, energy-efficient insulation components, and road infrastructure. However, the foam concrete with lower density tends to possess the lower stability. The unstable characteristics of foam concrete restricts its application. In this study, the feasibility of employing biochars to increase stability of foamed concrete is investigated. The rheological properties of base mix are carried out to analyze the foam concrete stability. The analysis of water state, interparticle distance and ion concentration are tested to analyze the stabilization mechanisms. Our findings demonstrate that the introduction of corn husk biochar (CHBC) within the base mix expedites flocculation formation, reducing interparticle distance and subsequently elevating the yield stress. Conversely, the inclusion of rice husk biochar (RHBC) diminishes ion concentration, heightening repulsion forces between particles and thereby reducing yield stress of base mix. Higher yield stress exert the higher constraining force and frictional force to the bubbles, thereby decreasing bubble size in fresh foamed concrete, bettering pore structure, compressive strength and foam stability of foamed concrete. Additionally, the increase in CHBC content enhances pore sphericity, potentially attributed to decreased bubble deformation parameters Caη.

Monovalent Salt and pH-Stimulated Gelation of Scallop (Patinopecten yessoensis) Male Gonad Hydrolysates/κ-Carrageenan.

The gelation of scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and κ-carrageenan (KC) subjected to pH (2-8, 3-9) and NaCl/KCl stimuli-response was investigated. SMGHs/KC gels subjected to a NaCl response exhibited an increasing storage modulus G'from 2028.6 to 3418.4 Pa as the pH decreased from pH 8 to 2, with corresponding T23 fluctuating from 966.40 to 365.64 ms. For the KCl-treated group, SMGHs/KC gels showed an even greater G' from 4646.7 to 10996.5 Pa, with T23 fluctuating from 622.2 to 276.98 ms as the pH decreased from 9 to 3. The improved gel strength could be ascribed to the blueshift and redshift of hydroxyl groups and amide I peaks, enhanced enthalpy and peak temperature, and gathered characteristic diffraction peaks from SMGHs, KC, NaCl, and KCl. The CLSM and cryo-SEM images further reflected that SMGHs/KC gels showed more flocculation formation and denser and more homogeneous networks with smaller pore sizes in more acidic domains, especially when subjected to the KCl response. This research gives a theoretical and methodological understanding of the construction of salt- and pH-responsive SMGHs/KC hydrogels as novel functional soft biomaterials applied in food and biological fields.

Molecular dynamics simulation of wax deposition in crude oil systems

Molecular dynamics (MD) simulation was employed to analyze the effects of different wax contents and molecular chain lengths on the wax deposition behavior in crude oil systems and the mechanism. The results show that the wax deposition on the iron surface occurs via a three-layer adsorption process driven by van der Waals (vdW) forces. In addition, there are four important stages in the process of crude oil deposition on iron surfaces. The first stage involves the diffusion of crude oil molecules onto the iron surface, the second involves their adsorption onto the solid surface and parallel alignment with the surface, and the third and fourth stages involve the formation of floccules through intermolecular interactions and bridging between the deposited layer adsorbed on the solid surface and the crude oil system. For different wax contents and molecular chain lengths, the wax deposition process is similar to crude oil systems, and the thicknesses of the deposited layers on the iron surface were similar. The primary contribution to the interaction energy between crude oil molecules and the iron surfaces is from vdW effects. As the crude oil system's wax content and molecular chain length increase, the interactions between crude oil molecules and the iron surface are strengthened, and these interactions are further enhanced as more crude oil molecules accumulate in the deposited layer. The results of the study may provide theoretical support for an in-depth understanding of the wax deposition process.

Sodium Alginate-Quaternary Polymethacrylate Composites: Characterization of Dispersions and Calcium Ion Cross-Linked Gel Beads.

The objective of this work was to examine the effect of quaternary polymethacrylate (QPM), a water-insoluble polymer with a positive charge, on the characteristics of the sodium alginate (SA) dispersions and the calcium alginate (CA) gel beads containing propranolol HCl (PPN). The SA-QPM composite dispersions presented the formation of flocculates with a negative charge due to the electrostatic interaction of both substances. The QPM addition did not affect the SA dispersions' Newtonian flow, but the composite dispersions' viscosity enhancement was found. The PPN-loaded CA-QPM gel beads had more spherical than the PPN-loaded CA gel beads. The incorporation of QPM caused a bigger particle size, higher drug entrapment efficiency, and greater particle strength of the gel beads. Despite the similar water uptake property, the PPN-loaded CA-QPM gel beads displayed lower burst release and slower drug release rate than the PPN-loaded CA gel beads. However, the drug release from the PPN-loaded CA-QPM gel beads involved drug diffusion and matrix swelling mechanisms. This study demonstrated that adding QPM into the SA dispersions leads to a viscosity synergism. The CA-QPM gel beads display a good potential for use as a bioactive compound delivery system.

Solution combustion synthesis of high-entropy metal spinel oxide as oxygen evolution reaction catalyst

High-entropy metal spinel oxide (HEO) is proved to be a promising oxygen evolution reaction (OER) catalyst with high catalytic performance and stability. A short routine synthesis process based on solution combustion synthesis was proposed to prepare (Co0.25Ni0.25Mn0.25Zn0.25)Fe2O4 spinel HEO in this work. During the process, the products were rapidly synthesized and melted due to the high-temperature reaction, and then quickly crystallized on the surface of nickel foam to form a nano-structure coating. With the aid of nano-scale spinel structure, the overpotential of non-activation HEO electrode reaches 276 mV at the current density of 10 mA·cm−2, and after 100 h i-t test, it can be further reduced to 230 mV, which proves the high activity of OER catalysis. The promotion of OER catalytic performance can be attributed to the surface reconstruction caused by the selective element leaching and the boost of oxygen vacancy, leading to the formation of nano-scale flocculation around spinel core after the long-term OER process. This work indicates a special casting process for functional materials and explores the application of rapid crystallization.

Flocculation kinetics and mechanisms of microalgae- and clay-containing suspensions in different microalgal growth phases

Interplays between microalgae and clay minerals enhance biologically mediated flocculation, thereby affecting the sedimentation and transportation of suspended particulate matter (SPM) in water and benthic environments. This interaction forms larger flocs with a higher settling velocity and enhances SPM sinking. The aim of this study was to investigate the flocculation kinetics of microalgae and clay in suspension and to elucidate the mechanisms associated with such interactions. Standard jar test experiments were conducted using various mixtures of kaolinite and microalgal samples from batch cultures (Chlorella vulgaris) to estimate biologically mediated flocculation kinetics. The organic matter (OM) composition secreted by the microalgae was characterized using a liquid chromatography - organic carbon detection system, and quantitative analysis of transparent exopolymer particles was conducted separately. A two-class flocculation kinetic model, based on the interaction between flocculi and flocs, was also adopted to quantitatively analyze the experimental data from flocculation. Results from the flocculation kinetic tests and OM analyses, in association with other data analyses (i.e., floc size distribution and flocculation kinetic model), showed that flocculation increased with OM concentration during the growth phase (10–20 d). However, on day 23 during the early stationary phase, flocculation kinetics started decreasing and substantially declined on day 30, even though the amount of OM (mainly biopolymers) continued to increase. Our results indicate that an adequate quantity of biopolymers produced by the microalgal cells in the growth phase enhanced floc-to-floc attachment and hence flocculation kinetics. In contrast, an excessive quantity of biopolymers and humic substances in the stationary phase enhanced the formation of polymeric backbone structures and flocculation via scavenging particles but simultaneously increased steric stabilization with the production of a large number of fragmented particles.

Ceramic Papers as Structured Catalysts: Preparation and Application for Particulate Removal

Fibers represent a type of structure of great interest in catalysis since they combine high area to volume ratio and can be fabricated from many types of materials, such as ceramic oxides, polymers, and alloys. They can be used in isolated form or structured, as in the case of the ceramic papers synthesized in this work, following a modified papermaking technique. The addition of cationic and anionic polyelectrolytes improved the retention of ceramic fibers during the ceramic paper formation stage by adsorption processes, through the formation of floccules. In the complex aqueous system containing charged macromolecules, the amounts of polyelectrolytes to be added were determined by titrations. To enhance mechanical properties of ceramic papers, different classes of nanoparticle suspensions can be used as binders. As a novel alternative, we have used different borate-type compounds. Among them, we selected natural ulexite, which was purified and used as a binder of ceramic fibers. In order to improve mechanical resistance and flexibility, measured from tensile indexes and elastic module, the amounts of NaCaB5O6(OH)6.5H2O and the calcination temperature were varied. In this contribution, to take advantage of the unique characteristics of the ulexite-containing ceramic papers, they were impregnated with Co,Ce and Co,Ba,K and tested for diesel soot combustion.

Magnetite and hematite quartzites - common features and technological differences

In the process of developing deposits of magnetite quartzites, hematite quartzites are simultaneously involved in mining. But the processing of hematite quartzites is associated with significant difficulties, so they accumulate in warehouses, landfills and spread uncontrollably in the environment. A detailed study of the features of the composition, structure and technological properties of hematite ores made it possible to develop a new method for complex processing in a vortex air-mineral flow. Under laboratory conditions, a number of commercial products were produced from them: iron ore concentrate, sinter ore, clinker ore, mineral paint and quartz sand, without waste accumulation. The formation of magnetic floccules is reduced in the air stream. Therefore, this technology also improves the processing of magnetite ores.

FLOCCULATION OF DISPERSE SYSTEMS BY POLYFUNCTIONAL POLYMER-INORGANIC HYBRIDS

Development of novel high-capacity multifunctional flocculants is a promising solution to selective separation of clay suspensions. Among such flocculants, polymer-inorganic hybrids are the most attractive for their excellent performance as compared with inorganic coagulants or syn-thetic polymers. Synthesis of polymer-inorganic hybrids was carried out in two stages. At the first stage, Al(OH)3sol was obtained by condensation of aluminum chloride and ammonium carbonate in the following conditions: t = 70°C, pH = 3-4, intensive stirring. In the second stage, Al(OH)3was mixed with aqueous solutions of polymers at room temperature. By changing the melting tem-perature of hybrid samples, the presence of interactionsbetween the Al3+cation and the carboxylate groups of the analyzed acrylamide copolymers were established. This paper reports synthesis and comparative efficiency analysis of systems that contain water-soluble anionic copolymers of acryla-mide and respective polyfunctional polymer-inorganic hybrids. We performed a quantitative char-acterization of concentration and structural effects of polymer flocculants on the flocculation mechanism and sludge thickening. Sludge thickening constants were determined. Higher values of thickening constants were noted in systems with additives of hybrid samples, due to the participa-tion of their macromolecules in the formation of floccules at the first stage of the sediment process, and at the stage of thickening of sediments,their deformation and compaction were revealed while maintaining a loose structure with the formation of bulk floccules. We considered the factors al-lowing to optimize flocculation of clay dispersions by polymer-inorganic hybrids in aqueous media. These novel flocculants were shown to have a good potential for applications in filtration or flota-tion processes as well as for wastewater treatment for removal of disperse impurities.

Curcumin nanoemulsions stabilized with natural plant-based emulsifiers

The effect of natural plant-based emulsifiers, citrus peel pectin, and gum Arabic, on the stability of oil-in-water (O/W) nanoemulsions encapsulating curcumin using a microfluidizer were studied. Pectin was more efficient than gum Arabic for nanoemulsions formation, with lower amounts of emulsifier (2% w/w) needed for the generation of smaller droplets (d3,2–220 nm). The stability of prepared nanoemulsions was measured using the LUMiSizer® analytical centrifugation test. The results showed that pectin gave better protection against droplet coalescence with temperature (40–60 °C). However, gum Arabic provided more protection of oil droplets from coalescence against a series of environmental treatments, including a range of pH variations (3–9) and NaCl additions (100–500 mM). Both emulsifiers showed adequate protection against freeze-thawing treatment. Furthermore, droplet size aggregation was more critical in pectin-stabilized emulsions during 7 days of storage at 4 °C. These results were explained by the formation of bridging flocculation within the pectin biopolymers. However, gum Arabic gave greater curcumin retention (85%) and stability against degradation compared to pectin (70%) after 7 days of storage. This was attributed to the thick and high-density layers formed by gum Arabic, which could provide better physical and chemical barriers against environmental stresses. The results from this study offer important information in developing “label friendly” products for encapsulating labile lipophilic bioactive compounds for use in the food and beverage industries.

Influence of Carbide-Forming Metals on the Wear Resistance of Ceramic Inserts in Cutting Hard Steel

The influence of carbide-forming metals on the wear of ceramic inserts in cutting hard-to-machine 12Х18Н9Т steel is studied theoretically. In addition, the influence of nitrogen on the yield point of the unmodified cutting ceramic and the alloyed ceramic is analyzed, and the influence of carbon and the temperature on the cutting ceramic’s limit of proportionality is determined. It is found that the impact strength of VOK-60M ceramic inserts is changed after diffusional hardening with nitrogen at pressure р = 025 MPa and temperature θ = 250°C. The ceramic inserts undergo X-ray spectral analysis so as to detect any changes in the lattice structure under the action of a magnetic field on saturation with nitrogen; the formation of floccules (of hair type b) in the section; or carbide deposits within the grains in the ceramic inserts.

Evaluation of Bentonite Mixed Indigenous Clays for Development of Clay Liners

This study presents experimental investigation of indigenous clays mixed with Bentonite to assess their suitability in potential use as clay liners. Soil samples with 0, 4, 8, and 12% Bentonite content from three different sites in Peshawar region were tested for various geotechnical properties. Grain size distribution, specific gravity, Atterberg limits and free swell were found through laboratory tests using appropriate ASTM procedures. Maximum dry density and optimum moisture content were calculated using Atterberg limits in available relationships. Finally, one dimensional consolidation tests were conducted to find relevant parameters for calculating hydraulic conductivity. A decrease in specific gravity, increase in free swell, and in optimum moisture content, decline in maximum dry density and hydraulic conductivity was observed with increase in Bentonite content across all three soil samples. During free swell, the soil clusters become larger leading to formation of floccules resulting in the narrowing of inter-particle space and thus blocking of permeable paths. It is concluded that 8% Bentonite content by weight yields a suitable mixture for a clay liner that has hydraulic conductivity in the range of recommended limits.

Complex coacervation of scallop (Patinopecten yessoensis) male gonad hydrolysates and κ-carrageenan: Effect of NaCl and KCl

The complex coacervation between scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and κ-carrageenan (κ-C) as influenced by ionic strength (NaCl and KCl) were monitored by using turbidimetric analysis at pH 1–12. The optical density of SMGHs/κ-C complexes initially increased at lower ionic strength (0–0.5 M) whereas decreased at higher ionic strength (0.5–1.5 M) as a result of the salt-enhanced and salt-reduced effect, respectively. Both of pHc and pHφ1 exhibited ionic strength-dependent behavior that firstly shifted to acidic pH followed by an increase as salt increasing. Moreover, salt addition strongly promoted the gelation of SMGHs/κ-C which was mainly driven by electrostatic forces, as reflected by increasing storage modulus G' from 3621 to 6559 Pa, 2681–25631 Pa at 0.1 Hz and decreasing T23 relaxation time from 349.10 to 296.89 ms, 241.07–186.89 ms by 0–0.5 M NaCl/KCl, respectively. Furthermore, the rheological and relaxation time T2 data were well associated with microscopy images that SMGHs/κ-C gels with NaCl/KCl showed a denser network with more flocculation formation and larger pore sizes with thicker network wall, especially in KCl group, which indeed supported the gel elasticity. Taken together, this study could provide theoretical and methodological basis for new functional hydrogel products with modified gel strength and microstructure by understanding the complex coacervation in gel system.

Effect of particle size distribution on flocculation and its growth in cement-ground limestone suspensions

The impact of particle size distribution on flocculation and its growth in cement-ground limestone suspensions was investigated by observing the flocculation states with a microscopic image analyzer and calculating the microscopic interparticle forces based on the multifractal methods and extended DLVO theory. The results showed that the particle size distribution exhibits a clear fractal feature and the flocculation and its growth have multifractal characteristics in cement-ground limestone suspensions. The spectral width, spectral difference and minimum fractal dimension of multifractal spectrum are used to depict the spatial arrangement, size distribution and average state of flocs, respectively. The multifractal spectrum of flocculation growth can be used to describe the growth of flocs. Compare with it, the multifractal spectrum of flocculation formation process has the advantages of integrity and simplification. When the fractal dimension of particle size distribution increases, the spectral width and spectral difference increase and the minimum fractal dimension decreases, which means that it is not beneficial to flocculation and flocculation growth. However, when it continues to increase, the opposite result appears because of the increase of effective distance ratio and interparticle force between particles.

Ultrasonic modifications of fine-grained limestone concrete

The structure formation of cement stone of fine-grained limestone concrete during hydration hardening of cements and filler based on them occurs due to the development of polydisperse and polymineral conglomerate, a process associated with an increase in the volume of crystallohydrates in relation to the volume of the original cement minerals, mixed with water. Structure formation is accompanied by the process of compaction of the developing system and polycrystallization with the formation of floccules of a porous hydrating mass. In the paper, ultrasonic processing is viewed to accelerate the all- side process of modification of concrete structure and hardening thereby stipulating the growth of strength and durability of concrete.

Flocculation Analysis of Cohesive Sediment by Turbidity Measurement

In many estuaries and rivers, the contaminants such as heavy metals have became serious threat to ecosystem including human communities since eagerly development of heavy industrialization. It was found that such materials tended to bound with cohesive sediments, and this bond mechanism is affected by hydraulic characteristics, for instance, turbulence intensity. To understand the complex relationship with the sediment-bond mechanism and hydrodynamics, the study for flocculation which includes the bond between sediment particles without heavy metals should be preceded as the first step. In this study, the flocculation of single sediment (Kaolin) was analysed through laboratory experiments in which the rotational jar-flow was generated and 3D numerical simulation which was performed to obtain the detailed flow fields and calculate hydraulic characteristics. First, the PIV experiment was conducted for the verification of 3D numerical model. And the flocculation index (IF) was proposed to consider the relation with the external energy and average turbulence length scale through the regression approach. The results showed that the flocculation was more affected by turbulence length (eddy size) than by turbulence intensity, and there was the significant specific range of turbulence length about formation of flocculation.

CHARACTERISTICS OF FLOCCULES OF CLAY-SALT SLUDGE FORMED BY POLYACRYLAMIDE AND ITS COPOLYMERS

The main characteristics of aggregates formed during the flocculation of clay-salt slurry using polyacrylamide-based polymers with various types of charge and molecular weights were studied using a laser analyzer of particle size Lasentec D600L of the FBRM system. The effect of the polymer type on the size of the floccules formed and their density was shown. It has been established that when using non-ionic polyacrylamide and its anionic copolymers floccules with a size of 500-600 mm are formed, and when flocculated with a cationic reagent, the floccules do not exceed 300 mm It was shown that an increase in the molecular weight of the cationic polymer does not contribute to an increase in the size of the aggregates of the clay slurry particles. It has been proven that with the use of non-ionic polyacrylamide and its anionic copolymers, the density of floccules significantly decreases with increasing their size, which is an important property of fractal aggregates. If the charge density of anionic polymers increases, the aggregates density decreases, due to electrostatic repulsion between the negatively charged polymer and the negatively charged surface of the sludge. Analysis of the kinetics of the clay sludge flocculation process showed that when using non-ionic and anionic polymers, fast flocculation occurs, and the number of primary particles in the aggregate does not exceed several units. When using a cationic polymer, the filling of the intraflouclear volume with primary particles occurs due to the displacement of the liquid phase, which contributes to the formation of dense and compact floccules. The results obtained can be used for the selection of flocculant in order to improve the process of thickening clay-salt sludge in the production of potash fertilizers.

Магнитные свойства и флокулообразование частиц железорудных минералов окисленных руд

Магнитные свойства и флокулообразование частиц железорудных минералов окисленных руд

Novel method for the qualitative identification of chromium ions (III) using l-aspartic acid stabilized CdS quantum dots

In this study, l-aspartic acid stabilized CdS quantum dots (L-Asp-CdS QDs) were synthesized via a one-step hydrothermal method and used for the qualitative identification of Cr3+. Cr3+ could be identified rapidly based on the formation of precipitated floccules using this method. Qualitative assessment indicated the resistance of this method to interference from various metal ions and it can be applied over a wide pH range with a qualitative determination limit of 1 μM. Moreover, we demonstrated that the L-Asp-CdS QDs can be employed for the practical detection of Cr3+ in water samples.