Aqueous Systems Research Articles

One‐Step Green‐Synthesized UiO‐66‐NH2 /Alginate Composite Hydrogels with Improved Methylene Blue Adsorption

AbstractZirconium‐based metal‐organic frameworks (Zr‐MOFs) represent an important class of MOFs with high stability and outstanding properties, the green preparation and shaping of which are still challengeable works to hinder their real‐world applications. In this presentation, UiO‐66‐NH2 MOFs were in‐situ grown accompanied by alginate (Alg) hydrogelation under aqueous conditions, achieving UiO‐66‐NH2/Alg composite hydrogels. Relevant characterizations demonstrate the in‐situ generated UiO‐66‐NH2 MOFs were evenly distributed in hydrogel networks by attaching on Alg fiber surfaces. The network structure became denser, but both specific surface area and pore volume were augmented due to the presence of MOFs, which in turn increased active sites to interact with adsorbates. Thus, the adsorption capacity to methylene blue (MB) of composite hydrogels became higher with more dosage of MOF ligand, and the pH sensitivity of Alg adsorption to MB in the pH range of 4 to 10 was eliminated. Furthermore, the study of adsorption kinetics and isotherm reveals MB adsorption on the obtained hydrogels belong to rate controlling chemisorption mechanism. In summary, this manuscript presents a facile approach to realizing the green synthesis and shaping of Zr‐MOFs by one‐step compositing of UiO‐66‐NH2 with Alg‐based hydrogels in aqueous system, achieving MOFs‐based composite hydrogels with enhanced MB adsorption.

Spin-Electrochemistry of Transition Metal Oxides for Energy Storage: Concepts, Advances and Perspectives.

Developing high-capacity and cyclically stable transition metal (TM)-based electrode materials for energy storage devices, such as aqueous ion energy storage systems, is crucial for addressing the growing issue of energy scarcity. The spin state, or spin configuration of the d-electrons, plays a vital role in the electrochemical energy storage performance of these materials. However, there has been a lack of systematic descriptions regarding the role of spin configurations in electrochemical energy storage to date. This review aims to elucidate the advantages of controlling the spin states of metal centers to enhance energy storage performance and highlights recent progress in employing spin state regulation in electrochemical energy storage. Additionally, it covers the various characterization techniques used to determine spin states. Finally, we discuss the future prospects and challenges within this emerging field, with the aim of accelerating the development of spin-based electrochemical energy storage technologies. This review also seeks to provide clear and reliable directions for the design and preparation of novel energy storage materials.

Roseomonas aestuarii, as a Potential In Situ Surfactin Producer During Hydrocarbon Biodegradation.

In situ biosurfactant production by hydrocarbon degrader microorganisms is an attractive approach in the bioremediation of oil contamination because of their compatibility, biodegradability, environmental safety, and stability under extreme environmental conditions. Given the high efficiency of bacteria in degrading petroleum hydrocarbons, the present work studied the detection and characterization of a biosurfactant-producing hydrocarbon degrader, Roseomonas aestuarii NB833. This strain was able to synthesize a biosurfactant during the biodegradation of crude oil, which reduced the surface tension of the aqueous system from 70 to 34 mN m-1, with a critical micelle concentration of 200 mg L-1. The emulsification ability of the biosurfactant was sustained at various temperatures, pH values, and salinities. The biosurfactant chemical structure was identified via FT-IR, LC-MS, and NMR analyses. These analyses confirmed the production of surfactin-C14 with a molecular mass of 1007 g mol-1. These results revealed the high potential of R. aestuarii NB833 as an in situ surfactin-producing bacteria for bioremediation applications under extreme environmental conditions.

One-step simultaneous and efficient extraction of multiple active compounds from Lycium barbarum by aqueous three-phase system: Focusing on polysaccharides

In the past few years, the aqueous three-phase system (A3PS) has attracted a lot of attention due to its effectiveness in the efficient separation. Polysaccharides, carotenoids and polyphenols were separated simultaneously from Lycium barbarum by an aqueous three-phase system (A3PS) formed by acetonitrile/betaine/K2HPO4 as a novel extraction technique. The system is characterized by small amount of machine reagents, few consumables and simple extraction steps. The effects of acetonitrile, betaine and K2HPO4 concentrations on the extraction efficiency were investigated by Response Surface Methodology. The optimum composition of A3PS were 26.2 % (w/w) acetonitrile, 10.2 % (w/w) betaine and 27.6 % (w/w) K2HPO4. Under this condition, the extraction efficiencies of carotenoids, polyphenols, and Lycium barbarum polysaccharides (LBP) were 42.12±0.10 %, 88.61±0.95 % and 84.63±0.46 %, respectively. The obtained LBP was characterized by several technologies. The LBP was proved to consist of mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, arabinose and fucose in a proportion of 4.14:0.80:4.00:4.43:22.20:39.9:12.44:3.22:8.46:0.41. The molecular weight of LBP was 12554 Da. In addition, LBP exhibited excellent antioxidant activity. In general, as a rapid developing method of extraction and separation, A3PS had potential application in the simultaneous separation of multiple substances.

The Many-Body Expansion for Aqueous Systems Revisited: IV. Stabilization of Halide-Anion Pairs in Small Water Clusters.

We report the structures, energetics, many-body effects, and vibrational spectra of water clusters stabilizing pairs of halide-anions, X-(H2O)kY- (k = 2-6, X/Y = F, Cl, Br, I) as well as their stability in the gas phase relative to fragmentation. We find that these metastable cluster structures mimicking the solvent-separated ion pair (SSIP) configurations in aqueous solutions are less stable relative to fragmentation into smaller ionic aqueous clusters containing a single halide anion. The many-body expansion (MBE) at these geometries was found to converge at the 4-body term, which is, however, significant, amounting to >20% of the total binding energy in several instances. The binding motif of these ion pair aqueous clusters starts as networks in which the water molecules form a "bridge" between the two halide-anions. As the cluster grows, these structures become destabilized by a more repulsive 3-body term for distances R(O-O) < 3.45 Å with respect to networks in which water molecules move outside the bridge, solvating the other side of the anion.

Chemometrics: A Vital Implement for Understanding the Water Structures by Near‐Infrared Spectroscopy

ABSTRACTWater structures take an important role in chemical and biological systems, because the structure and function of a molecule may depend on the structure of water with which the molecule interacts. Near‐infrared (NIR) spectroscopy has been proven to be powerful in analyzing the structure of water due to its sensitive response to OH. However, chemometrics is vitally important in the analysis of NIR spectrum of water due to the low resolution of the spectrum and the complexity of the water structures. In this review, chemometric methods for structural analysis of water in aqueous systems, particularly in chemical and biological processes, by NIR spectroscopy were summarized, from the improvement of spectral resolution to the effective extraction of the spectral information of different water structures. Through the changes of the spectral features of the water structures, the structural transformation of proteins, thermo‐responsive polymers, antifreeze agents, as well as the structural variation of water in the transformation were elucidated. Water was proved to be a good probe for analyzing the structure and interactions in aqueous solutions and chemical/biological processes by NIR spectroscopy.

Kinetic Modeling of Brilliant Blue Discoloration by Ozonation

This paper presents the results of investigations on the kinetic modeling of Brilliant Blue FCF (BB) discoloration reactions in aqueous solutions with different ozone concentrations and pH conditions. Kinetic studies involve knowledge of the structure and properties of dye and ozone, as well as of the experimental conditions. In general, scientists admit that the predominant oxidation pathway is direct (by free oxygen atoms) or indirect (by free hydroxyl radicals); this will depend on influencing factors such as the physicochemical properties of the dye, the pH of the aqueous solution, ozone concentration, reaction time, and the contact mode with/without stirring. In this experimental research, two pathways were chosen following CBB = f(t)—1. a constant dye concentration and different ozone concentrations, in the concentration range of 100–250 mg/L, in three pH media (acidic, neutral, and basic), with and without stirring; 2. a constant concentration of ozone and different dyes in the concentration range of 2.5–10 mg/L, under the conditions of point 1. With the obtained experimental data, the curves CBB = f(t) were drawn and processed according to the integral method of classical kinetics, based on first- and second-order equations. Unfortunately, this simple procedure did not give any results for the pH values studied. The rate constants were negative, and/or the reaction order depended on the initial conditions. Due to its structure, the BB dye has several chromophore groups, and thus multiple attack centers, resulting in several oxidation by-products, which is why the 1H-NMR spectrum was recorded for the discoloration of BB with ozone. Since the stoichiometry of the overall oxidation reaction, as well as the relationship between the rate constant and the reaction conditions mentioned above, is not known, a kinetic model based on mass transfer coupled with a chain reaction in the bulk liquid phase was proposed and successfully tested at pH = 7. This research approach also involves the consolidation of the theoretical bases of the ozonation process through the kinetic study carried out, as well as the proposal of a kinetic model. These systematics lead to results that are applicable to other aqueous systems that are impure with dyes, allowing for generalizations and the development of the field, ensuring the sustainability of the research.

Assessment of Cerium Adsorption Potential of Phosphoric acid Activated Biochar in Aqueous System: Modelling and Mechanistic Insights

Cerium pollution in waterbodies by improper industrial waste disposal is a major concern due to its detrimental impacts on the environment. Therefore, treatment of cerium-contaminated water is inevitable. Hence, this study is focused on the remediation of cerium pollution using phosphoric acid-activated biochar (PPMB) as an adsorbent, synthesized upon pyrolytic activation of palmyra palm male flower-based pristine biochar (PMFB) with H3PO4 at 500°C. The physico-chemical surface properties of PMFB and PPMB were evaluated through various microscopic and spectroscopic analyses. The key parameters such as biochar dosage, pH, temperature, contact time and initial cerium concentration were optimized as 0.5 g/L, 5.0, 303 K, 180 min and 50 mg/L respectively via batch adsorption. Pseudo-second order kinetic and Toth isotherm are the best-fitted models. The thermodynamic parameters including ΔG◦ (-30.4707±0.7618 kJ/mol at 303 K), ΔH◦ (16.1499±0.78 kJ/mol), and ΔS◦ (153.617±3.8404 J/mol/K) conveying that cerium adsorption onto PPMB was spontaneous, endothermic, and highly disordered at PPMB-bulk adsorption medium interface. Precipitation, electrostatic attraction, and surface complexation are predicted to be the predominant mechanisms for the chosen PPMB-cerium adsorption system. Moreover, cerium phytotoxicity on Vigna radiata explains the real-time applicability and feasibility of cerium adsorption using PPMB. Thus, the key findings of this study specified that the higher adsorption capacity of PPMB (141.3484±6.9856 mg/g) contributed by the incorporated phosphate groups, predominant mesoporosity, SSABET of 230.559 m2/g and anionic surface at a wider pH range (pH>3.08) make PPMB as efficient, economically feasible and environmentally friendly adsorbent for cerium adsorption in aqueous system.

Preparation and characteristics of zein/ethyl cellulose composite coating applied in aqueous system

Zein and ethyl cellulose (EC) were used as raw materials to prepare a composite coating applied in aqueous systems with mechanical properties, water stability, water solubility (including room-temperature (RT)/high-temperature and neutral/acidic conditions), and oil resistance as evaluation index. Results showed the most suitable conditions were mass ratio of zein/EC at 1:9, 93 % (v/v) aqueous ethanol, oleic acid as the plasticizer with the amount of 0.3 g/g, and curing temperature at 70 °C. Under these conditions, the tensile strength of composite coating was 4.61 MPa and elongation at break was 21.60 % after 4 weeks of soaking in water. Oil seepage was not observed within 1 week. The water solubility of coating in neutral water was 5.13 % at RT for 24 h, and 3.79 % at 80 °C for 2 min; in acidic water (pH = 4) was 4.54 % at RT for 24 h, and 5.44 % at 80 °C for 2 min. SEM results showed swelling occurred in zein coating after soaking, presenting micropores in soaked zein coating; zein microparticles in composite coating partially broke down and fell off after soaking. Water contact angle results revealed surface hydrophobicity by the following order: EC coating > composite coating > zein coating. FTIR results showed composite coating was physically compounding by hydrophobic interactions and hydrogen bonds.

Physicochemical and processing properties and in vitro fecal fermentation characteristics of Prunus cerasifera Ehrhart polysaccharide

Prunus cerasifera Ehrhart fruit polysaccharide (PCP) was obtained after determining the optimal extraction conditions for complex enzyme-assisted hot buffer extraction based on single-factor experiments and response surface methodology, followed by characterization of its physicochemical, processing, rheological, and biological properties. PCP was a thermally stable carbohydrate with acidic functional groups and a molecular weight of 1398.69 kDa, exhibiting smooth, dense flake and honeycomb network microstructures. PCP had favorable hygroscopicity, moisturizing properties, water and oil-holding capacity, proemulsification capability, and in vitro antioxidant activity. The apparent viscosity of PCP in an aqueous system was dependent on concentration and temperature and was altered by the variety and amount of metal ions added; its aqueous solutions exhibited strong viscosity and hydrogel-forming tendencies at suitable concentrations, along with excellent hydrogel properties after gelation. Furthermore, PCP favored the growth of beneficial gut microbiota and associated microbes responsible for producing essential short-chain fatty acids. Overall, PCP displayed high potential as a multifunctional additive for applications in the food, pharmaceutical, and cosmetic industries.

Congo red Removal using Microwave assisted Pyrolysis derived Magnetic Hemp hurd Biochar

Industrial hemp hurd (HH) are the residue obtained after the decortication of the hemp plant for fibre production, which is seldom explored for biochar potential and as adsorbent for dye removal. The present study focused on the microwave-assisted pyrolysis (MAP) of HH for biochar production, magnetization and application for Congo red (CR) removal from aqueous solutions. Magnetic hemp hurd biochar (MHB) depicted a heterogeneous surface with 4.84µm pore size, 17.64 m2/g surface area, and 10.05wt. % Fe. CR removal of 92% was achieved under optimum conditions i.e., treatment time: 120min, pH: 8, and initial CR concentration: 10mg/L with MHB dosage of 0.6g/L. The CR adsorption on MHB was well-fitted with the Freundlich isotherm (R2 - 0.971), owing to the heterogeneous surface of MHB. A strong match with pseudo-second order model (R2 - 0.973), indicated chemisorption as the likely adsorption mechanism. MHB exhibited 87% CR removal efficiency after three successive reutilization cycles. The outcomes of CR removal efficiency and MHB reusability indicated its potential application for adsorptive removal of CR from aqueous systems.

Aqueous fibrous membrane electrolyte for ultrathin flexible Zinc-air batteries

Membrane electrolytes are key to constructing planar energy storage devices of low thickness and high flexibility, requesting simultaneous optimization of ionic conductivity and mechanical stability. Herein, aqueous phase electrospinning (APE) was implemented to co-spin polyvinyl alcohol and pullulan polysaccharide for fabricating crosslinked fibrous membrane electrolytes. While the hydroxyl-rich polymeric backbone grafted with quaternary ammonium endows a strong hydrogen-bonding network affording a large ionic conductivity of 30.2 mS cm−1, the cellulose-braced fibrous structure manifests a high tensile strength of 4.6 MPa. What’s more, the porous structure of the membrane electrolyte with enhanced charge mobility and uniformity helps to guide homogeneous Zn plating/stripping with suppressed dendrite growth. As a result, the assembled ultrathin flexible ZAB delivers a superb round-trip energy efficiency of 59.8 %, a maximum power density of 102 mW cm−2 and a long-term cycling stability over 100 h at 5 mA cm−2. By innovating the concept and methodology of aqueous fibrous membrane electrolytes, this study opens up a new chapter on the development of solid electrolytes in aqueous battery systems for powering wearable electronics.

Deciphering the multi-electron redox chemistry of metal-sulfide electrode toward advanced aqueous Cu ion storage

While neutral aqueous metal batteries, featuring cost-effectiveness and non-flammability, hold significant potential for large-scale energy storage, their practical application is hampered by the limited specific capacity of cathode materials (less than 500 mAh g−1). Herein, capacity-oriented CoS2 and rate-optimized Co9S8 cathodes are developed based on the aqueous copper ion system. The charge-storage mechanism is systematically investigated through a series of ex-situ tests and density functional theory calculations, focusing on the reversible transitions of Co9S8→Cu7S4→Cu9S5/Cu1.8S and CoS2→Cu7S4→Cu2S, which are associated with the redox reactions of Cu2+/Cu+‖Co2+/Co and Cu2+/Cu+‖S22−/S2−, respectively. The electrochemical results show that CoS2 can exhibit a superior capacity of 619 mAh g−1 at 1 A g−1 after 400 cycles, while Co9S8 maintains an outstanding rate performance of 497 mAh g−1 at 10 A g−1 (the retention rate is 95% compared to 521 mAh g−1 at 1 A g−1). As a proof of concept, an advanced CoS2//Zn hybrid aqueous battery demonstrates a working voltage of 1.20 V and a specific energy of 663 Wh kgcathode−1. This work provides an alternative direction for developing sulfide cathodes in energetic aqueous metal batteries.

Breath inspired multifunctional low-cost inorganic colloidal electrolyte for stable zinc metal anode

The practical application of aqueous zinc-ion batteries (AZIBs) is primarily constrained by issues such as corrosion, zinc dendrite formation, and the hydrogen evolution reaction occurring at the zinc metal anode. To overcome these challenges, strategies for optimizing the electrolyte are crucial for enhancing the stability of the zinc anode. Inspired by the role of hemoglobin in blood cells, which facilitates oxygen transport during human respiration, an innovative inorganic colloidal electrolyte has been developed: calcium silicate-ZnSO4 (denoted as CS-ZSO). This electrolyte operates in weak acidic environment and releases calcium ions, which participate in homotopic substitution with zinc ions, while the solvation environment of hydrated zinc ions in the electrolyte is regulated. The reduced energy barrier for the transfer of zinc ions and the energy barrier for the desolvation of hydrated ions imply faster ion transfer kinetics and accelerated desolvation processes, thus favoring the mass transfer process. Furthermore, the silicate colloidal particles act as lubricants, improving the transfer of zinc ions. Together, these factors contribute to the more uniform concentration of zinc ions at the electrode/electrolyte interface, effectively inhibiting zinc dendrite formation and reducing by-product accumulation. The Zn//CS-ZSO//Zn symmetric cell demonstrates stable operation for over 5000 h at 1 mA cm−2, representing 29-fold improvement compared to the Zn//ZSO//Zn symmetric cell, which lasts only 170 h. Additionally, the Zn//CS-ZSO//Cu asymmetric cell shows stable average Coulombic efficiency (CE) exceeding 99.6% over 2400 cycles, significantly surpassing the performance of the ZSO electrolyte. This modification strategy for electrolytes not only addresses key limitations associated with zinc anodes but also provides valuable insights into stabilizing anodes for the advancement of high-performance aqueous zinc-ion energy storage systems.

Hydrate phase equilibrium of hydrogen with THP, DCM, TBAB+THF and sulfur hexafluoride +TBAB aqueous solution systems

Hydrate phase equilibrium of hydrogen with THP, DCM, TBAB+THF and sulfur hexafluoride +TBAB aqueous solution systems

Emerging Micromolecule-based Aqueous Two-phase Systems and Their Application in Biofuels

Aqueous two-phase system (ATPS) is a system composed of two incompatible solutions, which has excellent performance for extracting proteins, antibiotics, and other bioactive molecules, so it is a very simple, efficient, and green extraction and separation method. In this paper, we introduced three different emerging micromolecule-based ATPSs and introduced their characteristics, applications, advantages, and disadvantages respectively. This is of guiding significance for the synthesis of new ATPSs. One of the important prospects of this ATPS in industrial application is the separation and purification of fermentation-based biofuel. Adding a salt, sugar, or ionic liquid to a biofuel solution can remove most of the water, enabling efficient recovery and dehydration of biofuel. The two-step process can replace the traditional distillation and molecular sieve adsorption processes to obtain high-purity bioalcohols, thus introducing a new purification process for biofuel. An in-depth analysis of the separation performance of the emerging micromolecule-based ATPSs as well as an objective indication of their application provides valuable insights for further optimization and application of this kind of ATPSs in separation science.

The study of micellar transitions in mixed systems of dibranched cationic/nonionic fluorinated surfactants using various physicochemical methods

AbstractIn this study, a new method was introduced to induce micellar transitions by using vesicles formed from mixed surfactants, which offer enhanced stability. Different physicochemical analysis methods were used to study the transition mechanism and the aggregation behavior of the mixed aqueous system composed of the double‐chain cationic didodecyldimethylammonium bromide (DDAB) and a single‐chain nonionic fluorinated surfactant undecafluoro n‐pentyl decaoxyethylene ether (C5F11(EO)10), by varying the fraction of DDAB, then the total surfactant concentration of DDAB/C5F11(EO)10 mixed system at XDDAB = 0.9. The obtained results indicated that the addition of the fluorinated surfactant C5F11(EO)10 to the mixed system resulted in a reduction of the surface tension (γ) and a decrease in the Electrical conductivity (K). Furthermore, even at high total concentrations of the mixed system, the conductivity and charge density at the surface remained stable. As XDDAB values increased, a higher degree of dissociation (α) was observed, along with negative values in the thermodynamic parameters of micellization (Δ, Δ, and Δ), confirming the transition from micelles to vesicles. The dynamic light scattering (DLS) analysis revealed the formation of two stable types of aggregates at both low and high concentrations, as supported by the zeta potential (ζ). Upon increasing the concentration of surfactants, UV–Vis absorption measurements indicated that small spherical micelles grow into large multilamellar vesicles, as evidenced by an increase in turbidity and confirmed transmission electron microscopy images.

Thorium Recovery with Crown Ether–Polymer Composite Membranes

Thorium is a weak radioactive element, but the control of its concentration in natural aqueous systems is of great interest for health, because it is a toxic heavy metal. The present paper presents the recovery of thorium from diluted synthetic aqueous systems by nanofiltration. The membranes used for the nanofiltration of systems containing thorium species are composites containing 4′-Aminobenzo-15-crown-5 ether (ABCE) and sulfonated poly–etherether–ketone (sPEEK). The composite membranes (ABCE–sPEEK) were characterized by scanning electron microscopy (SEM), energy-dispersive X–Ray spectroscopy (EDAX), thermal analysis (TG and DSC), and from the perspective of thorium removal performance. To determine the process performance, the variables were the following: the nature of the composite membrane, the concentration of thorium in the aqueous systems, the rotation speed of the stirrer, and the pressure and the pH of the thorium aqueous system. When using pure water, a permeate flux value of 12 L·m−2 h−1 was obtained for the sPEEK membrane, and a permeate flux value of up to 15 L·m−2 h−1 was obtained for the ABCE–sPEEK composite membrane. The use of mechanical stirring, with a propeller stirrer, lead to an increase in the permeate flux value of pure water by about 20% for each of the studied membranes. Depending on the concentration of thorium and the pH of the feed solution, retentions between 84.9% and 98.4% were obtained. An important observation was the retention jump at pH 2 for the ABCE–sPEEK composite membrane. In the paper, a thorium ion retention mechanism is proposed for the sPEEK membrane and the ABCE–sPEEK composite membrane.

Combined Deep Learning and Optimization for Hydrogen-Solubility Prediction in Aqueous Systems Appropriate for Underground Hydrogen Storage Reservoirs

Combined Deep Learning and Optimization for Hydrogen-Solubility Prediction in Aqueous Systems Appropriate for Underground Hydrogen Storage Reservoirs

Enhanced Olivine Reactivity in Wet Supercritical CO2 for Engineered Mineral Carbon Sequestration.

The success of CO2 mineralization as a potential solution for reducing carbon emissions hinges on understanding chemical interactions between basaltic minerals and CO2-charged fluids. This study provides a detailed analysis of olivine dissolution in CO2-water mixtures at 90 and 150 °C, 2-9 MPa, and for 8 and 24 h, in both water- and CO2-dominant conditions. By using olivine crystal sections instead of powders, surface agitation is prevented, closing the gap between laboratory studies and natural settings. Surface chemistry, texture, and cross-sectional properties were examined pre- and postreaction using a multiscale approach combining spectroscopic and imaging techniques. Results show that wet supercritical CO2 environments lead to significant olivine dissolution, forming Mg-depleted, Si-enriched etched surfaces, and under certain conditions, the formation of passivating silica precipitates. In contrast, reactions in aqueous fluids caused minimal changes in surface chemistry and texture with no silica precipitation. These observations indicate that reaction extent in the CO2-rich phase is greater relative to water-rich mixtures at equivalent temperature, pressure, and reaction duration. The presence of silica precipitates incorporating leached metals indicates limited transport of reactant away from reaction sites in a CO2-rich medium. This study semi-quantitatively evaluates reaction extents in both CO2-rich and aqueous systems across a wide range of parameters, demonstrating faster mineralization in CO2-rich environments and highlighting their potential for enhancing the CO2 storage efficiency.