Changes In Solution Properties Research Articles

Mechanistic analysis of post-combustion CO2 capture performance during amine degradation

Degradation of amine is often regarded as a major problem for amine-based post-combustion CO2 capture. However, the observed regeneration energy in long-term pilot plant operations does not necessarily increase, regardless of the accumulation of degradation compounds. This paper provides a mechanistic explanation for this seemingly paradoxical behavior by focusing on the influence of heat stable salts and the CO2 loading range on solution properties. Post-combustion CO2 capture using degraded amine solution was simulated in Aspen Plus®, and the influence of heat stable salts on CO2 loading, solution properties, and regeneration energy were analyzed. Results indicate that the alteration of the operational CO2 loading range and the physical properties of heat stable salts themselves cause changes in solution properties that dictate overall energy consumption, such as viscosity, vapor liquid equilibrium, and specific heat capacity. These effects often offset each other to some extent, thereby obscuring the influence of individual factors on regeneration energy. These counteracting effects can largely explain the seemingly paradoxical behavior of post-combustion capture maintaining relatively low energy consumption even when amine degradation proceeds.

Experimentally probing ionic solutions in single-digit nanoconfinement

Understanding ionic solutions in single-digit nanoconfinement is crucial to explain the behavioral transition of confined solutions. This is particularly the case when the system length scale crosses the classical key length scales describing energetics and equilibrium of ionic solutions next to surfaces. Experimentally probing nanoconfinement would open large perspectives to test modelling or theory predictions. Here, using a new test vehicle that consists in 3 and 5 nm-height silica nanochannels associated with an original characterization technique based on the interface hard X-ray reflectivity analysis, we directly probed the transport of solutions containing cations having increasing kosmotropic properties (XCl2 with X: Ba < Ca < Mg) and obtained their distributions inside the nanochannels. We observed that cation adsorption decreases with the size of the confinement and that small cation adsorption is favored. In addition, nanochannel clogging occurs when ions tend to form ion pairs. These ion pairs may play the role of nano-sized prenucleation clusters leading to phase precipitation. These results evidence the specific ion effect in single-digit nanoconfinement that may result in dramatic changes of solution properties. In this line, our new method opens new perspectives for the characterization of ionic solutions and of interfaces in single-digit nanoconfinement.

A comparitive study on morphology, solution properties of electron beam and gamma irradited edible starch

Comparison in solution and morphology properties of electron beam and gamma irradiated potato starch are investigated. In the present work, the authors investigated the changes in solution properties, morphology, granular size and blue value on radiation dose of both electronbeam, gamma radiations. The studies indicate that surface morphology of granules is altered by both the radiations but damage is more in electronbeam irradiation. Viscosity of un- irradiated starch solutions appears to have non – Newtonian behavior; while irradiation led the solutions to have Newtonian nature. This is attributed to the damage in chemical structure caused by both the radiation. Blue index of non-irradiated and irradiated starches are measured and the changes are assigned due to variations in amylose content brought by radiation.

Calcium Ion-Induced Structural Changes in Carboxymethylcellulose Solutions and Their Effects on Adsorption on Cellulose Surfaces.

The adsorption of carboxymethylcellulose (CMC) on cellulose surfaces is one of the most studied examples of the adsorption of an anionic polyelectrolyte on a like-charged surface. It has been suggested that divalent ions can act as a bridge between CMC chains and the surface of cellulose and enhance the CMC adsorption: they can, however, also alter the structure of CMCs in the solution. In previous investigations, the influence of cations on solution properties has been largely overlooked. This study investigates the effect of Ca2+ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCM-D. The presence of Ca2+ facilitated the multichain association of CMC chains and increased the hydrodynamic diameter. This suggests that the adsorption of CMCs at high concentrations of CaCl2 is governed mainly by changes in solution properties rather than by changes in the cellulose surface. Furthermore, an entropy-driven mechanism has been suggested for the adsorption of CMC on cellulose. By comparing the adsorption of CMC from H2O and D2O, it was found that the release of water from the cellulose surface is driving the adsorption of CMC.

Enhancing the Sensitivity of Surface Plasmon Resonance Measurements Utilizing Polymer Film/Au Assemblies.

Surface plasmon resonance (SPR) is used to infer information about a sample that is in contact with an Au-coated glass slide coupled to the SPR prism. Shifts in the angle of the "SPR minimum reflection" can be related to changes in the refractive index (and/or thickness) of the sample that is in contact with the Au film, which can then be used to determine the concentration of an analyte in that sample. Here, we show that by depositing a layer of poly(N-isopropylacrylamide-co-acrylic acid) [p(NIPAm-co-AAc)] microgel on the SPR's Au film, with a subsequent layer of Au deposited on top of the microgels, the sensitivity of SPR to changes in solution properties can be enhanced. We investigated the sensitivity of the SPR to changes in the temperature of water in contact with the SPR's Au film as a function of the microgel immobilization density and the thickness of the Au layer deposited on the microgel layer. The data revealed that the SPR's Au film densely coated with microgels, with 5 nm of Au deposited, exhibited the maximal enhancement. The plasmon coupling effect between the additional Au film on the microgels and the SPR's Au film was further confirmed by 3D finite difference time domain simulations.

Holistic Approach to Understanding and Managing Amine Degradation during Post-combustion CO &lt;sub&gt;2&lt;/sub&gt; Capture Operation

Since most of real-world operations of post combustion capture of CO2 are burdened with issues on oxidative and thermal degradation of amine solutions, it is advantageous to find operational means to maintain process performance even while solution degradation proceeds. Although the chemical composition of degraded amine solutions is complex and variable, the relationship between solution properties, operating conditions, and process performance is reasonably explainable. As a strategy to deal with a plethora of amine compounds and degradation products, we propose a holistic approach which connects amine degradation to process performance via the alteration of solution properties. This approach includes altering the operating condition in response to the change in solution properties caused by amine degradation. This study is based on the comparison with fresh monoethanolamine aqueous solution and its degraded solution produced by continuous operation of a 10 kg-CO2/day bench-scale CO2 capture system. The solution properties and process performance were obtained experimentally as degradation progressed. From the analysis of obtained data, it was elucidated that the decrease in the CO2 loading capacity due to the amine degradation lead to deterioration of process performance. Moreover, it was indicated that the appropriate liquid flow rate for the degraded solution tends to be higher than that for the fresh solution because of decrease in the CO2 loading capacity.

Purification of organic pollutants in cationic thiazine and azo dye solutions using plasma-based advanced oxidation process via submerged multi-hole dielectric barrier discharge

Due to industrialization and population growth, water shortage has emerged as a critical global issue. Pollution of existing water supplies is a critical part of this issue, and organic contaminants are one of the main causes of water pollution. The non-thermal plasma-based advanced oxidation process (AOP) is one of the most widely studied and best developed processes owing to its simple structure and ease of operation. In this study, a plasma-based AOP was stably generated using submerged multi-hole dielectric barrier discharge (DBD) and added to an aqueous solution. Using a plasma system, the complexity of the process for generating hydroxyl radicals (OH) can be simplified by allowing ozone, hydrogen peroxide, ultraviolet light (UV), and OH to be generated simultaneously in one device. The electrical properties and concentrations of the active species were analyzed to establish optimal plasma operating conditions. Among the organic pollutants, methylene blue (MB) and methyl orange (MO) were selected as experimental targets because they are representative cationic thiazine and azo dyes, respectively. The results were analyzed by measuring the absorbance of UV–Vis, total organic carbon (TOC), chromaticity, and changes in solution properties. The effects of hydroxyl radical (OH) scavengers (D-mannitol) on the MB and MO degradation rates were also investigated. Based on these results, degradation mechanisms of MB and MO are proposed. After 3 min of plasma treatment, the concentration, chromaticity, and TOC of MB and MO rapidly decreased. Consequently, we believe that plasma-based AOP using submerged multi-hole DBD has advantages as an alternative technology for treating organic pollutants.

Modeling and simulation of fertilizer drawn forward osmosis process using Aspen Plus-MATLAB model

Although experimental studies on the impact of feed (FS) and draw solutions (DS) on the forward osmosis (FO) applications are reported in literature, systematic mathematical modeling considering the dynamic change in solution properties is lacking. In this study, asymmetric FO membrane simulation model was established using Aspen Plus-MATLAB subroutines algorithm to account for the effect of concentration polarization (CP), types of FS and DS and in their properties on FO performance. The developed model was validated by comparing the simulation with experimental results. The model successfully predict the performance of FO process under wide varieties of operational conditions, FS and DS flow rates and concentrations. The model showed that the variation of MCFDS concentration had a marked effect on water flux (WF) in contrast to flow rate. The WFs obtained from seawater (SW) increased from 5.28 L/m2.h to 42.08 L/m2.h as MCFDS changes from 150 g/L to 300 g/L which corresponding to 11.66% to 45.33% of water recovery. As for synthetic aquaculture wastewater (SAWW), 9.70 L/m2.h to 37.32 L/m2.h of WFs were exhibited with the increase of MCFDS concentration from 50 g/L to 200 g/L, respectively. The effect of concentrated external CP (CECP) was found to be significant in case of SW and negligible with SAWW. Whereas, increasing MCFDS concentration increases the severity effect of dilutive internal CP (DICP). The degree of DICP depends on the solute resistivity (KD) of porous layer, which were elevated (4.22–5.88 s/m) as MCFDS concentration increases (150–300 g/L). The study demonstrated the effectiveness and suitability of the developed Aspen Plus-MATLAB model simulating the FO process.

Drying of supported catalysts for high metal concentrations: A reduced parameter model

Supported catalysts are widely used in many industries. Manufacturing these catalysts is complex and manufacturing processes are influenced by many interdependent parameters. Although the performance and activity of catalysts are the most critical properties, their structures and design are also critical to their effectiveness. Previous work has shown that drying of catalysts can lead to the redistribution of metal and this in turn can affect the performance of the catalyst. At the same time, drying processes are often designed and scaled up by trial-and-error so it is desirable to have predictive models of the drying process. Previous experimental and modeling work has shown how the adsorption (of metal on the catalyst support) can significantly influence metal distributions at lower concentrations. It was also observed that at higher concentrations, adsorption was no longer the controlling factor, and solution properties began to control the metal distribution characteristics. Solution properties like density, viscosity, surface tension and volume ratio of metal all change as the metal concentration increases and these properties can in turn affect the distribution of metal during drying. In previous work, a drying model was developed that takes into account six different parameters to account for changes in solution properties as the concentration of metal increased. In this work, we carry out a parametric analysis, for nickel nitrate hexahydrate on a γ-alumina support, to investigate the relative importance of these parameters in accounting for metal redistribution during drying at high concentrations. A detailed analysis on each of the solution parameters, in terms of the drying rate and redistribution of metal, showed that only three of the parameters were important: the volume ratio of metal, the vapor pressure, and the solubility of the metal in the solution. Based on this, we have created a reduced parameter model with fewer parameters. This model can be used for different metal precursors without doing multiple expensive and time-consuming experiments. We tested this reduced parameter model using a new metal precursor (cobalt nitrate hexahydrate) on the same support, and modeling and experimental results for the new metal precursor are presented in this paper. We show that the reduced parameter model does not show appreciably different results from the more complex drying model and the results are in qualitative agreement with the experimental results.

Influence of solvent solubility parameter on the power law exponents and critical concentrations of one soluble polyimide in solution

Solvent species influence the interactions of dissolved polymers in solution and consequently induce changes in solution properties. A soluble polyimide was synthesized through polycondensation, and four solvents, namely, N,N-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), were selected to investigate systematically the influence of solubility parameter on solution power law behaviors. The power law relationship between specific viscosity and concentration was established using rheology and applying concepts from the Zimm, Rouse-Zimm, and Doi-Edwards models. All power law exponents were higher than theoretical predictions, and in the three concentration regions, i.e. dilute, semidilute unentangled, and semidilute entangled, the exponents increase, decrease, and increase, respectively, with respect to solubility parameter. Arguments derived from the listed models are proposed to explain these trends. The influences of solubility parameter on the overlap and entanglement concentrations are also discussed.

A contrastive study of effects of different organic matter on the smectite illitization in hydrothermal experiments

Although influence of organic matter (OM) on smectite illitization has received considerable attention in previous studies, the effect of different OM types on smectite illitization mechanism has rarely been examined. In the present study, hydrothermal experiments were conducted with N,N-dimethylhexadecylamine (16DMA)-smectite (M2) and lysine-smectite (M3) complexes to explore the effect of OM types on smectite illitization mechanisms. X-ray diffraction (XRD) analysis showed that mineral contents, illite percentage in mixed-layer illite-smectite (I% in ISm), the average number of layers (Nave), and stacking mode of ISm changed weakly at <300 °C while changed greatly at >300 °C. The changes varied obviously between M2 and M3 at >300 °C, indicating characteristics of solid-state transformation illitization mechanism in M2 and dissolution crystallization mechanism in M3. Moreover, the mid-infrared and thermo-XRD analyses indicated that the OM was mainly adsorbed in smectite interlayers at <300 °C, which delayed the exchange of K+ by interlayer cations and thus suppressed the smectite illitization. Above 300 °C, the OM was largely desorbed and the resulting changes of solution properties led to the acceleration of illitization and difference in illitization mechanisms in M2 and M3. The bulk mineralogy, element, and infrared analyses showed that illitization was accompanied by formation of new minerals and more minerals were formed in M2 than M3. The new minerals were further increased above 300 °C, especially the ankerite in M2. The binding mechanisms and strength varied in M2 and M3 because of differences in OM types, resulting in differences in bulk mineralogy evolution. This demonstrated the effect of organic-inorganic interactions on smectite illitization and mineral formation. The disparities in smectite illitization between M2 and M3, therefore, were linked to differences in mineral evolution of water-rock-OM systems with different OM types in natural environments. The insights obtained in the present study should be of high importance in understanding organic-inorganic interactions, hydrocarbon generation, and the carbon cycle.

Properties of Poly- and Oligopentacenes Synthesized from Modular Building Blocks

We describe a facile route to well-defined, solution-processable pentacene oligomers (2 to 7) and homopolymer using Suzuki–Miyaura cross-coupling reactions. Because this synthetic strategy leads to regioisomers, regiopure syn- and anti-trimers were also synthesized, revealing minimal changes in solution properties but significant changes in the solid state arising from differing levels of crystallinity. The materials were characterized by steady state absorption spectroscopy and cyclic voltammetry to study their electronic structure. The steady state absorption spectra exhibit a new high-energy transition in the oligomers, which intensifies as a function of oligomer length, thus increasing the range of absorption to include the entire visible spectrum. Density functional theory calculations indicate that the new peak results directly from the oligomerization. Solid state UV–vis suggests that while the monomer is amorphous, bricklayer packing in the higher oligomers significantly alters the solid state abs...

Kinetic modeling of self-hydrolysis of aqueous NaBH4 solutions by model-based isoconversional method

The present work reports the kinetic modeling of self-hydrolysis of non-buffered, non-stabilized NaBH4 solutions by model-based isoconversional method. The overall kinetics is described by a ‘reaction-order’ model in a practical operating window of 10–20 wt% NaBH4 solutions at 25–80 °C and 0–50% conversions. The apparent activation energy and pre-exponential factor are interrelated through a kinetic compensation effect (KCE). The apparent reaction order remains constant at a given temperature irrespective of extent of conversion and decreases with increase in temperature. It decreases from first-order to 0.26 with increase in temperature from 25 to 80 °C. The apparent activation energy is found to increase from 65 ± 11 to 162 ± 2 kJ mol−1 with increase in extent of conversion from 0 to 50%. The variation of parameters with extent of conversion is discussed based on changes in solution properties during the progress of hydrolysis reaction.

Engineering performance of water mist fire protection systems with antifreeze

The use of antifreeze in water mist fire suppression systems offers a potential alternative to the current applications of these systems in subfreezing environments. Design and development of these systems, however, requires quantitative data detailing the effect of antifreeze on factors, such as small droplet sizes and/or higher system pressures which is currently unavailable. This study investigates the use of antifreeze, of various chemical compositions and concentrations, in water mist systems by quantifying variables that affect spray characteristics, indicate the potential risk of system failure, and evaluate the interactions of the discharged agent with the fire. Extensive testing and analysis demonstrate that no tested antifreeze solution behaves ideally with respect to quantified variables. Some of the antifreezes tested should not be used above a certain concentration in high-pressure water mist systems due to solution flammability and the resulting contribution to the heat release rate of the fire. The impact of all other tested pressure and concentration combinations is less significant on the heat release rate of the fire. Therefore, solutions used at these respective pressures and concentrations are potentially suitable for use in water mist systems unless spray performance or the potential risk of system failure discourages their use. Ignitibility of the antifreeze discharge was proven to be a function of antifreeze solution concentration and droplet size. Future testing should determine the threshold droplet size for ignition of the antifreeze discharge and at what point changes in solution properties begin to significantly impact droplet size in subfreezing environments. Language: en

Solution Properties of Inorganic Contamination in Mixed Solvents: Theory, Progress, and Limitations

Most of what is known about the environmental fate and transport of contaminants comes from studies of dilute, aqueous solutions. Theoretical and practical aspects of hydrophobic organic contaminants in aqueous mixtures of organic solvents are well developed, but relatively little attention has been paid to those situations where inorganic contaminants such as metals, water, and organic solvents occur simultaneously. The authors discuss changes in solution properties accompanying the addition of organic solvents. They review more than 500 references to available data on ion solvation, solubility, activity, acidity, pairing, and pH in electrolyte and electrolyte-free solvent mixtures and tabulate selected experimental values. Whenever available, equations developed to estimate these properties are given and their applications and limitations described. The implications of the progress in mixed-solvents solution chemistry on contaminant behavior and transport are described. Major limitations to the study of inorganic contamination in mixed solvents include the absence of complete and comprehensive data (e.g., type of ionic species, activity coefficients, solubility constants) that characterize solute and solvent properties in these mixtures and the indefinite number of possible solute and solvent combinations. The generation of models predicting such data from easily measured benchmark solute and solvent properties is a major challenge. The availability of such database and models may open the field for environmental engineers and soil scientists to study the basic chemical processes and mechanisms of metal contamination in complex multicomponent systems.

Degradation of Active Brilliant Red X‐3B by a microwave discharge electrodeless lamp in the presence of activated carbon

Degradation of Active Brilliant Red X‐3B (X‐3B) in aqueous solution by a microwave discharge electrodeless lamp (MDEL) in the presence of activated carbon was investigated. The preliminary results proved this method could effectively degrade X‐3B in aqueous solution. The removal percentages of colour and chemical oxygen demand were up to approximately 99% and 66%, respectively, at the conditions of 0.8 g/L dye concentration, 20 g/L activated carbon, pH 7.0 and 8 min microwave irradiation time. The degradation basically belonged to first‐order reaction kinetics and its rate constant was 0.42 min−1. No aromatic organics were detected in the final treated solution, indicating that the mineralization was relatively complete. By studying the change in solution properties, it could be concluded that MDEL‐assisted oxidation was the dominant reaction mechanism. In addition, the influence of operational parameters and reuse of activated carbon were also discussed.

Removal of organic dye Direct Red 79 from water solutions by DC diaphragm discharge: Analysis of decomposition products

Water solutions of organic dye Direct Red 79 were treated by DC high voltage created by diaphragm discharge (input power up to 160 W). Higher dye decoloration (60% after 40 min) was observed in the anode part of the reactor by UV–VIS spectroscopy. Recorded absorption spectra showed shifts of absorption maximum to lower wavelength values that were related to the formation of stable degradation products. Absorption spectra obtained in the cathode part of the diaphragm reactor produced only negligible shifts of absorption maximum and the dye decomposition rate reached 25% after 80 min of the treatment. HPLC-MS method revealed five main compounds in the anode part and another three ones in the cathode part. Analysis of identified products showed on the initial decomposition of one azo-group in the original dye molecule. Significant changes of solution properties during the diaphragm discharge were observed, too. Solution conductivity increased in both parts of the reactor. Solution pH dropped from the initial neutral value to acidic conditions (up to 3) in the anode part and to alkaline conditions (up to 10) in the cathode part. Changes were induced by formation of reactive species by the discharge and by electrochemical reactions on electrodes.

Long‐term reactions of Ni, Zn and Cd with iron oxyhydroxides depend on crystallinity and structure and on metal concentrations

SummaryIron oxyhydroxides are long‐term sinks for toxic trace metals and are suggested as factors to explain long‐term metal immobilization in soil. It is unknown how crystallinity and crystal structure of iron (Fe) oxyhydroxides affect the long‐term kinetics of trace metal adsorption. Adsorption kinetics of nickel (Ni), zinc (Zn) and cadmium (Cd) on to four synthetic Fe oxyhydroxides (hydrous ferric oxide (HFO), ferrihydrite (FH), goethite (GT), haematite (HT)) were characterized in suspensions during 70 days at different initial metal concentrations and various pH values (3.8–7.0) maintained within 0.2 units. The slow reactions, defined as those occurring beyond day 1 were most pronounced in GT and least in HT. The extent of the slow reaction was surprisingly unrelated to crystallinity or microporosity as determined by N2 adsorption. Freundlich adsorption isotherms fitted to the data show that ageing between 1 and 70 days decreases metal concentrations in solution by factors of 2–30 (Ni), 1–20 (Zn) and 1–4 (Cd) depending on the type of oxyhydroxide. These factors become significantly larger at smaller concentrations for Ni and Zn in some oxyhydroxides and this concentration dependency suggests that slow reactions are not only related to diffusion. The short‐term adsorption strength of carrier‐free metal radio‐isotopes was similar at 1 or 70 days after reaction with these iron oxyhydroxides and excludes the possibility that long‐term reactions are related to solid‐phase transformations or changes in solution properties. The extent of slow reactions in GT decreased with decreasing pH and was less than a factor 2 within 70 days at pH 3.7. The results confirm that slow reactions in Fe oxyhydroxides can explain lessened metal availability by ageing in pH neutral soils. The uncertainty of their actual structure and crystallinity in soils does not allow quantitative predictions based on the behaviour of synthetic oxyhydroxides.

The use of membrane-assisted precipitation for the concentration of xanthan gum

Combining ultrafiltration and precipitation was studied to improve the productivity of xanthan separation. Changes in solution properties and the association behavior of xanthan were modified by salt (KCl) and solvent (isopropanol) addition, and were assessed using scanning electron microscopy (SEM). The concentration polarization layer produced by xanthan dissolved in buffer solution had a very high specific flux resistance that was enhanced by the addition of either KCl or isopropanol. SEM analysis revealed that the fine macromolecular structure observed with xanthan in buffer was further stabilized in the presence of KCl. Isopropanol addition induced phase separation and the formation of closely packed soft aggregate particles that significantly increased fouling layer specific resistance. The simultaneous salt and organic solvent addition resulted in surface morphologies containing aggregates that associated to create gels with varying porosities. When at least 1% (w/v) KCl and >30% (v/v) isopropyl alcohol was added to 2.5% (w/v) xanthan solution, a very porous fouling layer was created, which dramatically increased membrane flux. Membrane-assisted precipitation reduced the amount of precipitating solutes used while greatly increasing membrane flux, resulting in a large improvement in separation productivity.

A Complete Structural Description of the Catalytic Cycle of Yeast Pyrophosphatase,

We have determined the structures of the wild type and seven active site variants of yeast inorganic pyrophosphatase (PPase) in the presence of Mg2+ and phosphate, providing the first complete structural description of its catalytic cycle. PPases catalyze the hydrolysis of pyrophosphate and require four divalent metal cations for catalysis; magnesium provides the highest activity. The crystal form chosen contains two monomers in the asymmetric unit, corresponding to distinct catalytic intermediates. In the "closed" wild-type active site, one of the two product phosphates has already dissociated, while the D115E variant "open" conformation is of the hitherto unobserved two-phosphate and two-"bridging" water active site. The mutations affect metal binding and the hydrogen bonding network in the active site, allowing us to explain the effects of mutations. For instance, in Y93F, F93 binds in a cryptic hydrophobic pocket in the absence of substrate, preserving hydrogen bonding in the active site and leading to relatively small changes in solution properties. This is not true in the presence of substrate, when F93 is forced back into the active site. Such subtle changes underline how low the energy barriers are between thermodynamically favorable conformations of the enzyme. The structures also allow us to associate metal binding constants to specific sites. Finally, the wild type and the D152E variant contain a phosphate ion adjacent to the active site, showing for the first time how product is released through a channel of flexible cationic side chains.