Solution Research Articles

Rheology of Ring Copolymers in Dilute Solutions.

We investigate the rheology of ring copolymers theoretically within the framework of the optimized Rouse-Zimm theory in dilute solutions. The ring copolymer is composed of two type of monomers (A and B) of different sizes (A < B), which is represented by unequal-sized beads connected via harmonic springs with different spring constants. The hydrodynamic interactions (HI) between the monomers is modeled using the preaveraged HI tensor. These interactions accelerate the collective relaxation modes and impede the local relaxation modes. In the presence of HI, the storage modulus shows a quasi-plateau regime, demonstrating a viscoelastic solid-like response of the polymer, while the loss modulus exhibits a bimodal pattern due to the difference in the mobilities of the monomers. The inverse of the crossover frequency represents the overall characteristic relaxation time, which is higher for the ring copolymers than for the Rouse rings, suggesting a slower relaxation of the ring copolymers due to the presence of relatively large sized monomers. The quasi-plateau in the storage modulus and the bimodality in the loss modulus are enhanced with an increase in the size and number fraction of B-type monomers. An increase in the size of the B-type monomers increases both storage and loss moduli, resulting in an overall decrease in the dynamics of the ring copolymers.

Enhancing Mechanical Properties of Alkali-Activated Slag SIFCON for Sustainable Construction Using Recycled Glass and Tire-Derived Waste Steel Fibers

This paper presents the outcomes of a study in which continuous steel fibers, recovered from scrap tires of vehicles, were used to prepare alkali-activated slag-based slurry infiltrated fibrous concrete (SIFCON). In this experimental study, the steel fibers used were 250 mm long, with varying fiber contents of 0%, 1%, 2%, 3%, 4%, and 5%. The alkali-activated SIFCONs were produced by activating ground granulated blast furnace slag (GGBS) with a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions. Mixtures with ordinary Portland cement (OPC) were also cast for comparison purposes. The feasibility of utilizing finely ground waste glass as a silicate source for chemical activator solution in alkali-activated SIFCONs was also investigated. In this context, two different molar concentrations of NaOH, namely 8 M and 14 M, were employed during production. As activators, one series of mixtures utilized sodium hydroxide and sodium silicate solutions, while the other series replaced sodium silicate with finely ground waste glass. As a result, three different waste materials were utilized in concrete. 30 different mixtures were cast and examined in the experimental study. Load–deflection curves were obtained in three-point bending test and mechanical properties of the mixtures such as compressive, splitting and flexural strengths, fracture energy, and toughness were determined. The flexural strength and toughness increased with the use of waste steel fibers. The continuous waste fibers derived from discarded tires yielded results comparable to commercially available fibers, demonstrating their effectiveness in enhancing mechanical properties. Depending on mix design, the alkali-activated SIFCON attained flexural strength exceeding 75 MPa and compressive strength surpassing 100 MPa. These results suggest that concretes incorporating a variety of waste materials can be effectively combined. This innovative approach bridges an existing gap in the literature by combining alkali activation, waste glass, and waste steel fibers, ultimately yielding a sustainable composite that outperforms normal concretes in terms of mechanical properties while promoting environmental sustainability. Test results demonstrate that it is possible to obtain concrete with comparable mechanical properties while primarily composed of by-products and waste materials. This approach marks a substantial step in achieving high-performance concrete that relies solely on waste or by-products.Graphical

Solvation-free energy of uncharged and charged water-soluble synthetic polymer using adaptive Poisson-Boltzmann solver: poly(acrylic acid)

ABSTRACT Implicit solvent based on the Poisson-Boltzmann model of electrostatics provides a faster approach to the calculation of solvation and conformations of polymers compared to explicit solvents in molecular dynamics simulations. While PB-based methods have been used extensively for biological macromolecules, here we present the use of the Adaptive Poisson-Boltzmann Solver (APBS) approach for the solvation of synthetic polymer in water. Stereo-specific (isotactic) poly(acrylic acid) of different chain lengths (20–55 for uncharged and 15–50 for charged) are sampled from atomistic molecular dynamic simulations in explicit water followed by APBS in implicit water. The hydration energy of uncharged and charged polymers varies linearly with the number of units (N). The variation of total solvation energy for SASA (Solvent Accessible Surface Area) and SAV (Solvent Accessible Volume) shows a crossover from one scaling to the other. While such a transition is known for small hydrophobic solutes, we report this for a dilute solution of polymer at uncharged and fully charged conditions and in implicit solvent.

An Effective Precursor‐Solutioned Strategy for Developing Cu2ZnSn(S, Se)4 Thin Film Toward High Efficiency Solar Cell

AbstractEnhancing the efficiency of Cu2ZnSn (S, Se)4 (CZTSSe) thin‐film solar cells requires the development of well‐crystallized light‐absorbing layers. A deep understanding of the role of precursor solution chemistry in film nucleation and crystal growth processes is essential. Insights into these processes enable the development of innovative strategies to enhance absorber quality, minimize detrimental bulk defects, and ultimately improve device performance. This study elucidates the condensation reactions between thiourea and metal cations, as well as the alcoholysis of 2‐methoxyethanol (MOE), at different concentrations of precursor solutions. The primary focus of this study is implementing a simple and environmentally friendly innovative spin‐coating strategy, aimed at optimizing Cu2ZnSnS4 (CZTS) precursor films and adjusting the Se content within the film bulk to promote grain growth during selenization. This strategy effectively improves absorber morphology while suppressing the formation of deep‐level defects, thereby enhancing carrier transport in both interfacial and bulk regions of the absorber layer. Consequently, CZTSSe absorbers with enhanced crystallinity and reduced defects are synthesized, resulting in a solar cell with an impressive efficiency of 14.10%. These findings underscore the potential for creating highly efficient kesterite CZTSSe solar cells through the manipulation of precursor solution chemistry using environmentally friendly solvents.

Corrosion Inspection for Hard Disk Media with Carbon-Based Overcoats by In-Liquid Open-Loop Electric Potential Microscopy.

The hard disk medium (HDM) with a carbon overcoat (COC) is a fundamental component of a hard disk drive. The conventional test for its corrosion durability, known as the "HOT/WET test," requires considerable time and effort and does not provide any local information about the corrosion. Here, we address this issue by employing open-loop electric potential microscopy (OL-EPM), a potential measurement technique based on atomic force microscopy (AFM), for corrosion inspection. To explore the applicability of OL-EPM, we observed the surface of the HDMs with different COC thicknesses in a dilute HNO3 solution. Through time-dependent and high-resolution OL-EPM observations, we found that this technique can be used for detecting nanoscale COC defects. This is because the HDM surface under a COC defect is exposed to the solution and undergoes anodic dissolution, increasing the local potential around the defect. This is readily detected by OL-EPM even before corrosion product formation around the defects induces the topographic change. This work demonstrates that OL-EPM is useful not only for understanding the local corrosion mechanisms but also for detecting the COC defects in a much shorter time (∼3 h) than the HOT/WET test (3-4 days).

The Impact of Acid Strength and Mineral Composition on Spontaneous Imbibition with Reactive Fluids

Capillary rise experiments are conducted in a set of calcareous and siliceous rocks with varying mineralogy and petrophysical properties to understand the coupled impact of reactivity and spontaneous imbibition. A capillary rise experiment is performed in each sample: first with deionized water, then with a dilute acidic solution, and finally again with deionized water, and the capillary rise profile for each is recorded. Pre- and post-acid petrophysical properties such as porosity, permeability, pore size distribution, and contact angle are measured for each sample. The mineral makeup of the rocks significantly influences how the acidic fluids penetrate the samples. The primary reactions are the dissolution of Ca- and Mg-rich minerals which alter the pore network. The higher acid strength results in higher capillary rise in calcareous rocks and results in an increase in the average pore size. The same pH acid results in lower capillary rise in the siliceous rocks, and a general decrease in the average pore size is observed. Changes in contact angle indicate increased water affinity in carbonate and reduced affinity in sandstone. The link between capillary interactions and fluid reactivity is often overlooked in fluid flow studies, and this research sheds light on the importance of reactivity during spontaneous imbibition, offering insights into dissolution and precipitation processes during capillary flow.

A pH-Dependent Phase Separation Drives Polyamine-Mediated Silicification from Undersaturated Solutions.

Silica polymerization from its soluble monomers is fundamental to many chemical processes. Although industrial methods require harsh conditions and concentrated precursors, biological silica precipitation occurs under ambient conditions from dilute solutions. The hallmark of biosilica is the presence of amine-rich organic macromolecules, but their functional role remains elusive. Here, we show a pH-dependent stimulatory effect of such polyamines on silica polymerization. Notably, this process is decoupled from the saturation degree, allowing the synthesis of polymer-silica hybrid products with controlled network morphologies from undersaturated solutions. The data suggest a two-step phase separation process. First, an associative liquid-liquid phase separation forms a micrometer-size dense phase. Second, silica undergoes a liquid-to-solid transition in the supersaturated condensates to form a bicontinuous silica structure. This study can inspire "soft chemistry" routes to design organic-inorganic nanomaterials with regulatory principles optimized by evolution.

Activities of the Solution Chemistry Group in 2023

Activities of the Solution Chemistry Group in 2023

Exploring the thermal dynamics of mango leaf hopper (Cicadellidae: Homoptera) populations and evaluating insecticide susceptibility

Effective pest management in agricultural systems requires understanding environmental conditions and chemical solutions. The efficacy of lambda cyhalothrin, imidacloprid, and acephate for mango leaf hopper control was examined in relation to temperature. A controlled laboratory setup with a Bio-Oxygen-Demand (B.O.D) incubator maintained temperatures of 25 ºC, 22 ºC, and 29 ºC for the experiment. The investigated pesticides' toxicity varied with temperature. March 2022, October 2022, and July 2023 lambda cyhalothrin LD50 values were 0.524, 0.412, and 0.992 ppm at 25 ºC. In the same timeframes, imidacloprid showed LD50 values of 0.797, 1.187, and 1.774 ppm. Acephate has 0.890, 1.572, and 1.927 ppm LD50s. Piperonyl butoxide (PBO), N-(Propargyloxy) phthalimide (PP), diethyl maleate (DEM), and S,S,S-tributyl phosphorotrithioate (DEF) were also tested for synergy. DEM and the studied insecticides had synergistic ratios, suggesting improved pest control tactics. The data showed that temperature, pesticide effectiveness, and synergistic interactions promote sustainable mango pest management.

Angular momentum transport in Taylor–Couette turbulence of dilute surfactant solution

Angular momentum transport in Taylor–Couette turbulence of dilute surfactant solution

Modelling the chronopotentiometric response of constant current hydrogen evolution from dilute solutions of strong acids

Modelling the chronopotentiometric response of constant current hydrogen evolution from dilute solutions of strong acids

Efficient removal of low concentrations of copper and lead ions in water using chitosan-condensed tannin composite microspheres

Condensed tannin was solidified onto chitosan microspheres to prepare chitosan-tannin (CT) composite microspheres with a simple preparation method to study its performance in adsorbing copper (Cu2+) and lead ions (Pb2+) in aqueous media. The study investigated the influence of the mass ratio of tannin and chitosan, pH value, adsorption time, and initial concentrations of Cu2+ and Pb2+ on the adsorption capacity of Cu2+ and Pb2+ ions. Additionally, the study examined the adsorption isotherms and kinetics of Cu2+ and Pb2+ on CT composite microspheres. The adsorption process aligns more closely with the fitting results of the Langmuir model. The maximum capacity for saturated monolayer adsorption of CT composite microspheres for Cu2+ and Pb2+ was 37.6 and 52.9 mg/g, respectively. The adsorption process of CT composite microspheres for Cu2+ and Pb2+ was primarily driven by single-layer chemical adsorption. In addition, metal ions adsorbed onto CT composite microspheres can be released by treating them with a dilute solution of strong acid. Furthermore, the CT composite microspheres exhibited impressive removal efficiencies of 82 % and 95 % for Cu2+ and Pb2+ respectively, even at low concentrations of 2 mg/L. The CT composite microspheres have the ability to easily separate the adsorbed Cu2+ and Pb2+ ions.

Effect of Firing Temperature on the Structural, Optical, and Electrical Properties of VO&lt;sub&gt;2&lt;/sub&gt; Thin Films Deposited by Chemical Solution Deposition

Effect of Firing Temperature on the Structural, Optical, and Electrical Properties of VO&lt;sub&gt;2&lt;/sub&gt; Thin Films Deposited by Chemical Solution Deposition

Stability of Ionogels upon Contact with Water: Effect of Polymer Matrix Hydrophobicity and Ionic Liquid Solubility

New composite materials (ionogels) have been obtained based on imidazolium ionic liquids immobilized in highly porous polymers, i.e., polyamide 6,6 (nylon 6,6) and low-density polyethylene. A method has been proposed for determining the rate of ionic liquid removal from an ionogel upon contact with water, with this method being based on continuous measuring the conductivity of an aqueous phase. The results of the conductometric measurements have been confirmed by high-performance liquid chromatography data. It has been shown that the stability of ionogels upon contact with water is determined by both the hydrophobicity of a polymer matrix and the solubility of an ionic liquid in water. The highest degree of ionic liquid removal (more than 80%) has been observed for composites based on porous polyamide 6,6 (hydrophilic matrix) and dicyanimide 1-butyl-3-methylimidazolium (completely miscible with water). Ionogels based on lowdensity polyethylene (hydrophobic matrix) and bis(trifluoromethylsulfonyl)imide 1-butyl-3-methylimidazolium (poorly soluble, 1 wt %, in water) have shown the highest stability (washout degree of no more than 53% over 24 h). The method proposed for analyzing the rate of ionic liquid dissolution in water has been used to discuss the mechanism of this process.

Substituting phosphorus and nitrogen in hydroponic fertilizers with a waste derived nutrients solution: pH control strategies to increase substitution ratios

Hydroponics, despite its potential for efficient crop production, relies heavily on chemical fertilizers derived from nonrenewable resources and thus contributes to environmental burdens and unsustainable use of phosphorus. Integrating hydroponics into a circular phosphorus economy is crucial for mitigating these impacts. This study quantitatively assessed the capacity of filtrates from nitrified biogas digestate (f-NBD), a nutrient solution derived from organic waste, to replace phosphorus and nitrogen in hydroponic chemical nutrient solutions. Additionally, the influence of pH control methods on phosphorus recovery and substitution was investigated using a novel pH-rebound approach involving acidification followed by alkalinization to pH 6. The experimental results demonstrated that the pH-rebound method effectively dissolved apatite phosphorus, the predominant form of precipitated phosphorus in NBD, without inducing significant reprecipitation upon alkalinization. This pH adjustment enhanced the phosphorus solubility and optimized the nitrogen-to-phosphorus (N/P) ratio in f-NBD, enabling it to substitute up to 77% of the phosphorus and 100% of the nitrogen in standard hydroponic nutrient solutions. The study also revealed that, under certain conditions, f-NBD is as a more viable option for phosphorus recovery than struvite, a widely recognized recovered phosphorus product. The identified substitution ratios and pH optimization strategies provide valuable insights for mitigating the environmental burdens of hydroponic fertilizers. By partially replacing chemical nutrient solutions with f-NBD, hydroponics can be integrated more effectively into a circular phosphorus economy, reducing the reliance on nonrenewable resources and curtailing the environmental impacts associated with the production and use of conventional fertilizers. This research provides a basis for future initiatives aimed at developing sustainable hydroponic systems and offering new utilization methods for biogas digestate.

Advanced valorization of cocoa (Theobroma cacao L.) pod husks through 40 kHz-ultrasonic bath assisted extraction of pectins

Theobroma cacao is an economically relevant agricultural commodity. In the Amazon region, Peru boasts 6 of the 10 genetic cacao families of the world. Cocoa pod husk (CPH), the main agro waste (67–76% of fruit), and its three constituent layers, endocarp (END), mesocarp (MSO) and epicarp (EPI) tissues, were separately evaluated, after drying and milling, as potential sources of pectin, a valuable industrial additive. A 40 kHz-ultrasonic bath (160 W; 100% amplitude) pretreatment (15 min; 50 °C) of tissue powders with citric acid solution (pH 3.0) followed by magnetic stirring (50 °C - 1400 rpm; 60 min for CPH, EPI and MSO or 345 min for END) gave the highest pectin yields, together with the 1:150 (g/mL) powder to solvent ratio for CPH and EPI pectins, and 1:75 (g/mL) for MSO and END pectins. END pectins were homogalacturonans with an 86-84 % uronic acid (UA) content, while the rest had ≈ 65 % UA, all with low degrees of methylesterification (5.26–35 %) and acetylation (9.56–30 %). Pectins exhibited high molecular weights (5.57–7.05 MDa). Phenolic compounds (216–4643 μg/g) and methylxanthines (theobromine, caffeine) were co-extracted with pectins. Mechanical spectra of 1.50 % w/v aqueous pectin with 30 mg Ca2+/g of UA revealed “weak gel” type networks, most structured for END pectin, but “dilute solution” for CPH pectin. CPH and its constituent tissues can be valorized as sources of thickening and gelling pectins.

Prince Nana Amaniampong.

"The most important factor in the choice of my current research topic was its potential to make a meaningful impact on sustainable energy and chemical solutions. The idea of using sonocatalysis to drive reactions with less energy, near-ambient temperatures and fewer pollutants really resonated with me… My favorite time of day is early morning, just as the sun rises…" Find out more about Prince Nana Amaniampong in his Introducing… Profile.

Dissolution and solubility of the calcium-nickel carbonate solid solutions [(Ca1−xNix)CO3] at 25 °C

A series of the calcium-nickel carbonate solid solutions [(Ca1−xNix)CO3] were synthesized and their dissolution in N2-degassed water (NDW) and CO2-saturated water (CSW) at 25 °C was experimentally investigated. During dissolution of the synthetic solids (Ni-bearing calcite, amorphous Ca-bearing NiCO3 and their mixtures), the Ni-calcite and the Ca-NiCO3 dissolved first followed by the formation of the Ni-bearing aragonite-structure phases. After 240–300 days of dissolution in NDW, the water solutions achieved the stable Ca and Ni concentrations of 0.592–0.665 and 0.073–0.290 mmol/L for the solids with lower Ni/(Ca + Ni) mol ratios (XNi), or 0.608–0.721 and 0.273–0.430 mmol/L for the solids with higher XNi, respectively. After 240–300 days of dissolution in CSW, the water solutions achieved the stable Ca and Ni concentrations of 1.094–3.738 and 0.831–4.300 mmol/L, respectively. For dissolution in NDW and CSW, the mean values of log IAP (Ion activity products) in the final stable state (≈ log Ksp, Solubility product constants) were determined to be − 8.65 ± 0.04 and − 8.16 ± 0.11 for calcite [CaCO3], respectively; − 8.50 ± 0.02 and − 7.69 ± 0.03 for the synthetical nickel carbonates [NiCO3], respectively. In respect to the bulk composition of the (Ca1−xNix)CO3 solid solutions, the final log IAP showed the highest value when XNi = 0.10–0.30. Mostly, the mean values of log IAP increased with the increasing XNi in respect to the Ni-calcite, the Ni-aragonite and the amorphous Ca-Ni carbonate. The plotting of the experimental data on the Lippmann diagram for the (Ca1−xNix)CO3 solid solution using the predicted Guggenheim parameters of a0 = 2.14 and a1 = − 0.128 from a miscibility gap of XNi = 0.238 to 0.690 indicated that the solids dissolved incongruently and the final Ca and Ni concentrations in the water solutions were simultaneously limited by the minimum stoichiometric saturation curves for the Ni-calcite, Ni-aragonite and the amorphous Ca-Ni carbonate. During dissolution in NDW, the Ni2+ preferred to dissolve into the water solution and Ca2+ preferred to remain in the solid, while during dissolution in CSW for the solids with higher XNi, the Ca2+ preferred to dissolve into the water solution and Ni2+ preferred to remain in the solid. These findings provide valuable insights into understanding the mechanisms governing Ni geochemical cycle in natural environments.

Optimizing hydrogen storage in a heterogeneous aquifer considering hysteresis and dissolution

Hydrogen (H2) is a rising solution for carbon-neutral fuel transition. Saline aquifer, ubiquitous underground, is a competitive candidate for large-scale underground hydrogen storage (UHS). This study proposed to use a heterogeneous aquifer formation for probing the functioning of UHS and optimizing its operation. By integrating geological information with lithofacies from the Ordos Basin in China, a heterogeneous triplet aquifer model was built, upon which compositional simulations of UHS operations that consider two-phase flow, relative permeability hysteresis, hydrogen and water phase behavior, rock compressibility, and dissolution mechanisms were conducted. Orthogonal array L25 (56) with mixed levels was designed to optimize the H2 recovery. Results substantiate the feasibility of storing millions of cubic meters of H2 with over 95% recovery. Ignoring dissolution and relative permeability hysteresis will result in an overestimation of the hydrogen recovery factor, with the effect of relative permeability hysteresis being more significant. Provided equal cycle length, a lower injection-withdrawal rate is suitable for long-term operation of hydrogen storage, while a higher rate can achieve a higher recovery factor during the early cycles. Measures of lowering the skin factor and pre-extracting brine could improve storage capacity and reduce water production during injection and withdrawal. The optimized case is expected to achieve an average H2 recovery of 98.8% for 30 operation cycles with moderately low saline water production. These findings provide valuable insights for developing large-scale and cost-effective UHS in saline aquifers.

Surface potentials of conductors in electrolyte solutions.

When we place conducting bodies in electrolyte solutions, their surface potential Φs appears to be much smaller in magnitude than the applied one Φ0 and normally does not obey the classical electrostatic boundary condition of a constant potential expected for conductors. In this paper, we demonstrate that an explanation of these observations can be obtained by postulating that diffuse ions condense at the "wall" due to the reduced permittivity of a solvent. For small values of Φ0, the surface potential responds linearly. On increasing Φ0 further, Φs augments nonlinearly and then saturates to a constant value. Analytical approximations for Φs derived for these three distinct modes show that it always adjusts to salt concentration, which is equivalent to a violation of the constant potential condition. The latter would be appropriate for highly dilute solutions but only if Φ0 is small. Surprisingly, when the plateau with high Φs is reached, the conductor surface switches to a constant charge density condition normally expected for insulators. Our results are directly relevant for conducting electrodes, mercury drops, colloidal metallic particles, and more.