Average Distribution Coefficient Research Articles

Investigating advection–dispersion behavior for simulation of HTO and 238Pu transport in argillaceous shale with different varying degrees of weathering

Abstract Exploring the migration behavior of radioactive nuclides in the surrounding rock media of the disposal site is the basis for the safety evaluation of radioactive waste disposal sites. In this study, the column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (HTO) and plutonium-238 (238Pu) in highly weathered argillaceous shale with different degree of weathering. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and obtain relevant migration parameters. The results showed that: (1) the breakthrough curves of HTO and 238Pu in fractured media with varying degrees of weathering exhibited clear “peak forward” and “tail dragging” phenomena; (2) the stream tube model can better fit the BTCs of the nuclides in the highly weathered fractures and obtain the average dispersion coefficient <D>, average distribution coefficient <K d>, and other parameters; (3) the two-region non-equilibrium model can better fit the BTCs of the nuclides in the penetrating fractures and weak weathering fractures and obtain the volumetric water content of the mobile liquid region (θ m), distribution coefficient (K d), and other parameters.

Transport parameters for PFOA and PFOS migration through GCL's and composite liners used in landfills

The effect of applied stress (20, 60, and 150 kPa) on the diffusion of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) through a geosynthetic clay liner (GCL) is examined. The diffusion coefficients deduced from GCL diffusion tests for PFOA and PFOS decrease linearly with decreasing final bulk GCL void ratio (increasing applied stresses). The different components of the same GCL are also tested for PFOA and PFOS sorption. No statistically significant sorption of PFOA is observed for any of the components of the GCL. However, some sorption of PFOS onto the cover and carrier geotextiles of the GCL is observed with in an average distribution coefficient, Kd ∼2.22 ml/g for the GCL. Permeants containing different PFAS compounds are tested to assess their impact on the Geomembrane (GMB) - GCL interface transmissivity in composite liners. Results show PFAS concentrations up to 20 ppm had negligible impact on the GMB-GCL interface transmissivity. Lastly, the GCL specimens extracted from the diffusion tests are tested for hydraulic conductivity. No impact of PFAS is seen on the hydraulic conductivity of GCLs subjected to high applied loads, but a small increase is seen on the GCLs subjected to relatively low applied stresses.

Progressive stirred freeze concentration: Effect of operative parameters on vital statistics of beer

AbstractFreeze concentration (FC), a low‐cost alternative technology to separate and concentrate high‐value compounds, was applied to three distinct craft ale beer styles—Witbier, Bitter, and Porter—to investigate its impact on vital beer statistics. A central composite design with freezing temperature and ice fraction as factors was employed, with response surface analysis revealing significant effects on the average ice growth rate (), concentration index (CI), and average distribution coefficient () of ethanol, total solids, color, and bitterness in the liquid fraction. Results showed that ice fraction primarily influenced solute concentrations and increased with ice fraction due to water removal. Freezing temperature affected . The type of beer had a significant impact on color and bitterness, reflecting the specific style parameters. Furthermore, response optimization yielded conditions that significantly altered beer statistics, leading to changes in ethanol content, total solids, color, and bitterness, possibly classifying them as new beer styles. The study demonstrates the potential of FC to influence the beer characteristics and broaden the range of beer styles.Practical applicationsInnovations in science and technology, added to the search for new beer styles, promote the development of new products in the beer industry. In this article, a potential use of the freeze concentration technology was identified for the development of new concentrated beer products. The impact of progressive stirred freeze concentration in three craft beers was studied. First, obtaining a concentrated beer from this technique was possible, with a higher concentration of total solids and ethanol. In addition, the vital statistics of beer could be modified using freeze concentration to obtain novel concentrated beer products.

Nanocrystalline Ce(OH)4-based materials: ruthenium selective adsorbent for highly alkaline radioactive liquid waste

Abstract Cerium hydroxide, Ce(OH)4 (Ce), has been synthesised and assessed as a Ru-selective adsorbent for treating alkaline radioactive liquid waste. Infrared spectroscopy, thermal analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy investigations confirmed the successful formation of nanocrystalline Ce from Ce(NO3)3·6H2O. Selective removal of 106Ru from the ion-exchange effluent of intermediate-level liquid waste (ILW) by Ce was assessed using a high-pure germanium (HPGe) gamma-ray spectrometer. The calculated average distribution coefficient (k D) was ∼200 mL/g. The percentage removal of 106Ru using Ce by varying time, [106Ru] and [Ce] was calculated. The adsorption of 106Ru on Ce follows pseudo-second-order and Freundlich isotherms. The calculated Q max was 93,584 Bq/g. Accelerated leaching studies of the Ru-laden Ce cement product were carried out and found suitable for transport and disposal. Further, Ce-Polyether sulphone (Ce-PES) and Ce-Chitosan (CeC) composites were prepared and assessed for their Ru-uptake capacity for engineering scale application.

Reactive extraction system: A study on recovery of itaconic acid using different natural oils

The current study explores the aptness of natural oils like sunflower oil, sesame oil, and ricebran oil as diluents for the extraction of itaconic acid using tri octylamine as extractants in the range of 0.228––0.687 (mol/L). Utmost average distribution coefficient was obtained as 8.69 for sunflower oil, 8.52 for sesame oil, and 9.66 for rice bran oil at 0.687 mol/L of tri octyl amine. Highest itaconic acid extraction efficiency is 91.52% when ricebran oil accompanied with 0.687 mol/l of tri octylamine. Thereby, rice bran oil along with tri octylamine is the appropriate solvent system for the extraction of itaconic acid from their aqueous solution. Further, the loading ratio values ϕ < 0.5 in maximum cases suggest 1:1 complex have formed between the extractant and the itaconic acid. At Higher itaconic acid concentrations in the range of 0.150–––0.250 (mol/L) and lower tri octylamine concentrations 0.228 (mol/L), loading ratio > 0.5 was observed which indicates that 2:1 and 3:1 acid-extractant complexes are formed.

Fractal characteristics of rocks and mesoscopic fractures at different loading rates

Uniaxial compression tests were conducted on rocks under different loading rates to analyze their effect on rock fragmentation. The fractal dimension of the macroscopic fragmentations of the rocks were then calculated by combining the fractal theory. Based on scanning electron microscopy (SEM), the macroscopic failure characteristics and mesoscopic fracture morphology characteristics of the rocks under different loading rates were compared and analyzed; the mesoscopic fractal dimension of the fracture was calculated using the box dimension method. The results demonstrate that when the loading rate is increased from 0.001 to 0.05 mm/s, the average fragmentation distribution coefficient decreases from 18.99 to 16.37 mm. As the loading rate increases, the fragmentation distribution coefficient gradually decreases, and the rock sample breaks; the degree of failure gradually increases, and the failure mode of the rock transforms from tension to shear failure. The SEM analysis reveals that under low loading rates, an intergranular fracture indicates the primary failure mode. The macroscopic performance primary presents tensile failure; as the loading rate increases, the range of the transgranular fracture gradually increases, and the failure mode evolves from an intergranular to transgranular fracture. The fractal dimension of the mesoscopic structure of the rock fracture tends to increase with an increase in the loading rate, and demonstrates a good positive relationship by fitting with the macrostructure fractal dimension. A larger fractal dimension of the microstructure of a rock fracture indicates more complex structure of the fractured surface. This study provides a better understanding of the meso-rock failure mechanism, and presents significant findings regarding ore rock fragmentation and rockburst prevention.

Soil heterogeneity influence on the distribution of heavy metals in soil during acid rain infiltration: Experimental and numerical modeling

Acid rain is a global environmental problem that mobilizes heavy metals in soils, while the distribution and geochemical fraction of heavy metals during acid rain infiltration in heterogeneous soils are still unclear. In this study, we performed column experiments to investigate the distribution and geochemical fraction of Cu, Pb, Ni and Cd in heterogeneously layered soils during continuous acid rain infiltration. Chloride ion used as a conservative tracer was found to be uniformly distributed during acid rain infiltration, showing insignificant preferential flow effects in the column. In contrast, however, the distribution of heavy metals was highly non-uniform, especially in the silty soil at the lower part of the column, indicating a heterogeneous distribution of adsorption capacity. In addition, in the control experiments with neutral rain infiltration, uniform distribution of heavy metals was observed, indicating that the heterogeneous distribution of adsorption coefficient during acid rain infiltration was mainly caused by different pH buffering capacities. A numerical model considering water flow and solute transport was developed, where the average water-solid distribution coefficient (Kd) in Layer 2 was only 1.5–12.5% of that in Layer 1 during acid rain infiltration. The model could predict the variation of heavy metal concentrations in soil with the majority of error less than 35%, confirming that different Kd induced the heterogeneous distribution of heavy metals. In addition, the geochemical fraction of heavy metals in the upper coarse sand layer remained stable, while the acid-extractable fractions in the lower loam and silt loam layer gradually increased. Our findings suggest that soil heterogeneity, especially chemical heterogeneity affected by rainfall acidity, has an important influence on the infiltration, migration and geochemical fraction of heavy metals in soils. This study could help guide the risk assessment of heavy metal-contaminated sites that were polluted by acid rain or landfill leachate.

Experimental investigation on recovery of bio‐based protocatechuic acid using ionic liquids

AbstractBACKGROUNDThe production of protocatechuic acid (PCA) (which has significant applications in organic intermediates, chemical reagents, pharmaceuticals, dye synthesis, etc.) by fermentation is a potential replacement to the conventional petrochemical routes of carboxylic acid production. However, the extraction processes of these carboxylic acids from fermentation broths and dilute waste water using organic solvents imply additional environment hazards. Ionic liquids (ILs) have come to the focus because of their superior properties as well as environmentally friendly nature, and are being intensively used for separation processes. The equilibrium extraction efficiency for bio PCA using two imidazolium ILs – 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (bmim‐PF6) – was investigated under isothermal conditions in diluent octanol. The distribution coefficient and extraction efficiency were determined to be much greater than those obtained with traditional extractants and diluents.RESULTSThis work is the first of its type to use ILs for PCA isolation. From the equilibrium extraction experiments conducted it was observed, in octanol, that the average distribution coefficients (KD) values for bmimBF4 and bmim‐PF6 were 5.3 and 5.36, respectively, with average extraction efficiencies of 83.84% and 84.08% at a lower IL concentration of 10% by volume, and the findings may be utilised to develop an extraction purification system for PCA separation from aqueous streams. Multiple stages of separation may lead to almost 100% recovery.CONCLUSIONPCA was efficiently extracted from aqueous solutions using bmimBF4 and bmim‐PF6 in octanol, providing preliminary practical information and theoretical support for PCA separation, purification and recovery. © 2022 Society of Chemical Industry (SCI).

Rheological Characterization and Quality of Emulsions Based on Fats Produced during the Reaction Catalyzed by Immobilized Lipase from Rhizomucor Miehei

It has been shown that structured lipids, formed in the process of enzymatic modification of natural hard fat with walnut oil, are capable of stabilizing emulsion systems without the need to add additional emulsifiers. This is especially true for emulsions containing fat formed during enzymatic modification when the amount of added water to the reaction catalyst was in the range of 12–16 wt%. Physicochemical evaluations, i.e., the average particle size, its growth, distribution, and dispersity coefficient, were comparable with the reference emulsion where the emulsifier was lecithin, well-known for its emulsifying properties. Microstructure studies also confirmed the above observations. Rheological studies performed on a set of emulsions containing structured lipids of variable composition confirmed that interesterified lipid blends can be directly utilized as a fat base in the preparation of stable emulsions. The consistency, thixotropic behavior, long-term shelf life, and thermal stability of these emulsions were found to be comparable to systems stabilized with conventional emulsifiers, i.e., sunflower lecithine. Our approach offers the opportunity for the preparation of stable emulsion systems, free from additional emulsifiers, for the food or cosmetics industry, which is extremely important from the point of view of the preparation of products free from allergens.

In-stream sorption of azithromycin and levofloxacin in a river receiving sewage treatment plant effluent

Modelling natural attenuation is crucial to managing pharmaceuticals. However, little is known about the mechanism behind their in-stream sorption. To better understand the in-stream attenuation of the highly sorptive antibiotics azithromycin (AZM) and levofloxacin (LVF), we monitored them in a 2.1-km stretch of the Asano River under diverse flow conditions. This stretch receives effluent directly from a sewage treatment plant (STP), which was a dominant source of the pharmaceuticals. Average distribution coefficients between dissolved and particulate phases (Kd,SPM) in the outflow river water were 6.3×105 L/kg for AZM and 7.5×104 L/kg for LVF, while those in the STP effluent were 1–2 orders of magnitude lower. Mass balances in the river stretch calculated by considering only dissolved phase (MBw) and both dissolved and particulate phases (MBs) were 8%–52% and 58%–102%, respectively, for AZM, and 58%–71% and 60%–105% for LVF. MBw<MBs is attributed to an increase in suspended particulate matter (SPM)-mediated mass flows in the river stretch, i.e., in-stream sorption to SPM, which was caused mainly by their much higher river Kd,SPM values than those in the effluent. Their river Kd,SPM values increased on higher-flow days with decreasing effluent content in the river water, resulting in the increase of their in-stream SPM sorption. Their in-stream loss from the entire water column (i.e., 100−MBs), which was attributable to their mass transfer from the overlying water to sediment through sorption, was decreased on higher-flow days by hydrological factors. A key finding is that AZM and LVF mostly entered the river stretch in the dissolved phase of STP effluent, whereas they existed substantially in the particulate phase in the outflow river water, especially on high-flow days.

Experimental investigation using conventional and natural extractants for liquid-liquid extraction of glutaric acid

Glutaric acid finds major application in corrosion inhibitors, anti-scaling agents, pharmaceutical synthesis, etc. mainly as a polymer building block. However, production of glutaric acid is quite difficulty, necessitated research into viable options for glutaric acid recovery. The liquid-liquid extraction method has been employed to recover glutaric acid from aqueous phase using a variety of inert extractant (cyclohexane) and natural, non-toxic extractants (rice bran and sesame oil). The extraction efficiency (%E) and distribution coefficient (K D ) were calculated based on equilibrium data obtained at 298.15 ± 1 K. The trend observed for the average distribution coefficient along with extraction efficiency respectively are as follows: rice bran oil (0.152, 12.48%) > Cyclohexane (0.075, 6.90%) > Sesame oil (0.037, 3.53%). The rice bran oil has the highest extraction efficiency, whereas sesame oil provided the lowest extraction efficiency.

Comparison of sorption and solute transport behaviour of several herbicides in an alkaline agricultural soil

ABSTRACT 2,4-Dichlorophenoxyl acetic acid (2,4-D), atrazine, glyphosate, and metribuzine, have been used extensively as herbicides, which can lead to contamination of soil and groundwater. The objective of this study was to quantify and compare the sorption and solute transport of these commonly used herbicides in alkaline agricultural soil since there is little transport data for all these contaminants under comparable conditions and for the same soil, and there is also limited information for sorption of herbicides to alkaline soils. The amount of sorption as average distribution coefficient (Kd ) obtained from water saturated-soil-column tracer experiments varied between these herbicides, and included 0.01, 0.06, 0.44, and 2.14 L/kg for 2,4-D, metribuzine, atrazine, and glyphosate, respectively. These miscible-displacement, tracer experiments indicated linear and rate-limited sorption for all herbicides studied, and they also showed that the sorption amount, or Kd , for 2,4-D and metribuzine was low and comparable, whereas increased sorption Kd was observed for atrazine and glyphosate. Hydrophobic attraction to the soil organic fraction was the dominant mechanism for the non-ideal sorption, because Kd increased with Koc and herbicide pKa values were below the soil and water pH. Two-site sorption and transport modelling, including linear sorption and rate-limited sorption, matched all of the observed herbicide breakthrough curves. The sorption of 2,4-D and metribuzine onto alkaline agricultural soil was nearly negligible, which confirms increased contamination risk of groundwater resources. Whereas, atrazine and glyphosate exhibited significant sorption to the alkaline soil with decreased leaching risk compared to 2,4-D and metribuzine.

Constructions and properties of a class of random scale-free networks.

Complex networks have abundant and extensive applications in real life. Recently, researchers have proposed a large variety of complex networks, in which some are deterministic and others are random. The goal of this paper is to generate a class of random scale-free networks. To achieve this, we introduce three types of operations, i.e., rectangle operation, diamond operation, and triangle operation, and provide the concrete process for generating random scale-free networks N(p,q,r,t), where probability parameters p,q,r hold on p+q+r=1 with 0≤p,q,r≤1. We then discuss their topological properties, such as average degree, degree distribution, diameter, and clustering coefficient. First, we calculate the average degree of each member and discover that each member is a sparse graph. Second, by computing the degree distribution of our network N(p,q,r,t), we find that degree distribution obeys the power-law distribution, which implies that each member is scale-free. Next, according to our analysis of the diameter of our network N(p,q,r,t), we reveal the fact that the diameter may abruptly transform from small to large. Afterward, we give the calculation process of the clustering coefficient and discover that its value is mainly determined by r.

Multiple probabilistic networks with scale-free property

It is well-known that the random scale-free networks are ubiquitous in the world and are applied in many areas of scientific research. Most previous networks are obtained from a single probability parameter, while our networks are produced by multiple probability parameters. This paper aims at generating a family of random scale-free networks by graphic operations based on probabilistic behaviors. These random scale-free networks can span a network space S(p, q, r, t) with three probabilistic parameters p, q, and r holding on p + q + r = 1 with 0 ≤ p, q, r ≤ 1 at each time step t. Each network N(p, q, r, t) of S(p, q, r, t) is a dynamic network that will be produced by N(p, q, r, t − 1) based on three types of operations, called the type-A operation, the type-B operation, and the type-C operation. We will show the topological structures of each network N(p, q, r, t) by its average degree, degree distribution, diameter, and clustering coefficient, and, furthermore, compute the degree exponent γ=1+ln(4−r)ln⁡2, as well as power-law distribution, in order to reveal the scale-free behavior of N(p, q, r, t), which induces the whole space S(p, q, r, t) to be scale-free. Our findings are able to enrich the fundamental structure properties of complex networks, in particular scale-free networks.

Partitioning of Catechol Derivatives in Lipid Membranes: Implications for Substrate Specificity to Catechol-O-methyltransferase.

We have utilized multiparametric surface plasmon resonance and impendance-based quartz crystal microbalance instruments to study the distribution coefficients of catechol derivatives in cell model membranes. Our findings verify that the octanol–water partitioning coefficient is a poor descriptor of the total lipid affinity for small molecules which show limited lipophilicity in the octanol–water system. Notably, 3-methoxytyramine, the methylated derivative of the neurotransmitter dopamine, showed substantial affinity to the lipids despite its nonlipophilic nature predicted by octanol–water partitioning. The average ratio of distribution coefficients between 3-methoxytyramine and dopamine was 8.0. We also found that the interactions between the catechols and the membranes modeling the cell membrane outer leaflet are very weak, suggesting a mechanism other than the membrane-mediated mechanism of action for the neurotransmitters at the postsynaptic site. The average distribution coefficient for these membranes was one-third of the average value for pure phosphatidylcholine membranes, calculated using all compounds. In the context of our previous work, we further theorize that membrane-bound enzymes can utilize membrane headgroup partitioning to find their substrates. This could explain the differences in enzyme affinity between soluble and membrane-bound isoforms of catechol-O-methyltransferase, an essential enzyme in catechol metabolism.

Mobility of 2,4-Dichlorophenoxyacetic Acid, Glyphosate, and Metribuzine Herbicides in Terra Rossa-Amended Soil: Multiple Approaches with Experimental and Mathematical Modeling Studies

2,4-Dichlorophenoxyl acetic acid (2,4-D), glyphosate, and metribuzine are used extensively as an herbicide in the vicinity of Antalya, Turkey. The objective of this study was to investigate the mobility of such herbicides in terra rossa-amended soil by multiple approaches with batch, miscible-displacement, and mathematical modeling studies. The results indicated that the sorption isotherms exhibited predominantly linear behavior over a wide range (0–100 mg/L) of selected herbicides. The average distribution coefficient (Kd) obtained from linear sorption isotherm was 0.95, 1.20, and 44.15 L/kg for 2,4-D, metribuzine, and glyphosate, respectively. After hydrogen peroxide treatment for eliminating organic carbon content in the soil, the average distribution coefficient (Kd) obtained from the linear sorption isotherm was 0.096, 0.118, and 4.37 L/kg for 2,4-D, metribuzine, and glyphosate, respectively. Miscible-displacement experiments also showed that the sorption of 2,4-D, metribuzine, and glyphosate was described by linear and rate-limited processes in the soil. Transport of metribuzine and 2,4-D was slightly but glyphosate was extensively delayed compared to non-reactive tracer experiments in the soil. Hydrogen peroxide treatment experiments also indicated that the organic carbon content was responsible for the non-ideal sorption behavior of such herbicides. The rapid desorption can be attributed to soft carbon fraction (humic/fluvic acid and lipids), whereas slower desorption can be responsible by hard carbon fraction (black carbon, kerogen) of soils that led to chemically non-ideal behavior. Two-site transport modeling analyses, including linear sorption and rate-limited sorption–desorption, provided a reasonably good match to the herbicide breakthrough curves indicating mathematical modeling results were generally consistent with the results obtained from the batch and column experiments. As a result, sorption of 2,4-D and metribuzine onto terra rossa-amended soil was low which could lead to contamination risk of karstic groundwater resources overlying the Antalya travertine plateau in the region. On the other hand, glyphosate exhibits much more sorption affinity in the soil and leaching risk is limited as with more delay. As a result, investigating the mobility of such herbicides in top soils overlying the karstic aquifer systems in Antalya would be very important to identify the contamination risk of groundwater resources. The results from the present study would also help in the design of effective herbicide management strategies in Antalya, Turkey.

Occurrence, distribution and risk assessment of abused drugs and their metabolites in a typical urban river in north China

This study investigated the presence of 11 abused drugs and their metabolites, including amphetamine, methamphetamine (METH), ketamine, ephedrine (EPH), cocaine, benzoylecgonine, methadone, morphine, heroin, codeine, and methcathinone in the surface water and sediment samples of Beiyunhe River, a typical urban river flowing through Beijing, Tianjin, and Hebei provinces in North China. An analytical method of determining these abused drugs and their metabolites in water and sediment was developed and validated prior to sample collection in the study area. Results showed that METH and EPH were predominant in water and sediment samples. The total drug concentrations ranged from 26.6 to 183.0 ng/L in water and from 2.6 to 32.4 ng/g dry weight in sediment, and the drugs mainly originated from hospitals and sewage treatment plants. The average field-based sediment water distribution coefficients of abused drugs were calculated between 149.3 and 1214.0 L/kg and corrected by organic carbon. Quotient method was used to assess the risks. The findings revealed that these drugs and their metabolites at determined concentrations in water samples will not impair the aquatic ecosystem biologically, but their potential harmful effect on the function of the ecosystem and human health should not be overlooked.

Hydrothermal Conversion of Red Mud into Magnetic Adsorbent for Effective Adsorption of Zn(II) in Water

Red mud, a Fe-rich waste generated from the aluminum industry, was recovered as an adsorbent for wastewater treatment. The separation process of red mud from water after adsorption, including centrifugation and filtration, was complicated. This study demonstrated an alternative option to recycle red mud for preparing magnetic adsorbent via a facile hydrothermal route using ascorbic acid as reductant. Red mud is weakly magnetized and consists of andradite, muscovite, hematite, and cancrinite. After hydrothermal treatment, andradite in red mud was reductively dissolved by ascorbic acid, and transformed into magnetite and morimotoite. With increasing hydrothermal temperature, the dissolution of andradite accelerated, and the crystallite size of magnetite increased. When the hydrothermal temperature reached 200 °C, the prepared adsorbent P-200 showed a desirable saturation magnetization of 4.1 Am2/kg, and could be easily magnetically separated from water after adsorption. The maximum adsorption capacity of P-200 for Zn2+ was 89.6 mg/g, which is eight-fold higher than that of the raw red mud. The adsorption of Zn2+ by P-200 fitted the Langmuir model, where cation exchange was the main adsorption mechanism. The average distribution coefficient of Zn2+ at low ppm level was 16.81 L/g for P-200, higher than those of the red mud (0.3 L/g) and the prepared P-120 (1.48 L/g) and P-270 (5.48 L/g), demonstrating that P-200 had the best adsorption capacity for Zn2+ and can be served as a practical adsorbent for real-world applications. To our knowledge, this is the first study to report the conversion of red mud into a magnetic adsorbent under mild conditions.

Two-phase flow structure assessment based on dynamic image analysis

Two-phase flow regime is an important industrial process phenomenon. Pressure drops, volume fraction and flow pattern are the most significant parameters describing the flow hydrodynamics of the two-phase mixtures. Authors propose a qualitative and quantitative description of the two-phase fluid flow structure, provided by the dynamic image analysis method. Method is based on high-speed visualization, stereological techniques and videogrammetry with grey level analysis and cross-correlation of signals. The study was conducted on a rectangular, vertical channel, with air-water co-current upwards flow. Dimensions of the channel are 5 × 50 × 1200 mm. The gas phase flux is 0.01 dm3/h and 0.16 dm3/h. The liquid phase flux is set to 0.01 dm3/h. The measurements and calculations were based on the stereology techniques, the Zuber-Finley and Mishima-Hibiki drift-flux model, and the grey level of the image. Two-phase flow parameters such as the void fraction, interfacial surface, free distance between objects, number of objects, average object size, drift and distribution coefficient was determined. Parameters were obtained as a function of time. Comparison of the image analysis results with the drift-flux models was made. To summarize, developed dynamic image analysis, provides information suitable for the assessment and reconstruction of the two-phase flow structure, which can be used for automatic process control.

Uptake of actinides by calcium silicate hydrate (C-S-H) phases

The sorption of actinides (Th, U – Am) was studied in dependence of the solid-to-liquid (S/L) ratio (0.5–20.0 g/L) and the calcium-to-silicon (C:S) ratio. The C:S ratio was varied between 1.80 and 0.70 to simulate the changing composition of the C-S-H phases during cement degradation from high to low C:S ratios. The decrease of the calcium content in the C-S-H phases by time is accompanied by a decrease in pH in the corresponding suspensions from 12.6 to 10.2. X-ray photoelectron spectroscopy (XPS) of the C-S-H phases showed an increasing depletion of Ca on the surface with increasing C:S ratio in comparison to the composition of the solid phase as a whole.The sorption experiments were performed with the redox stable species Am(III), Th(IV) and U(VI), as well as the redox sensitive Np(V) and Pu(III). The average distribution coefficients Rd for all investigated actinides are around 105 L/kg. The oxidation state of Pu retained by the C-S-H phases was investigated with high-energy resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy. Samples with C:S ratios of 0.75 and 1.65 showed that the initially added Pu(III) was oxidized to Pu(IV) in the course of the experiment.