Pure Water System Research Articles

Conformational Fluctuations and Induced Orientation of a Protein, Its Solvation Shell, and Bulk Water in Weak Non-Unfolding External Electric Fields.

Extreme external electric fields have been reported to disrupt the tertiary structure of stably folded proteins; however, the effects of weaker electric fields on many biomolecules, especially net-uncharged proteins, and on the surrounding aqueous environment have been rarely discussed. To explore these effects at the atomic level, here, we have used molecular dynamics simulations to estimate rotational motion and induced structural fluctuations in the model protein ubiquitin and its hydration layer due to applied non-unfolding electrostatic fields. When exposed to weak electric fields of up to 0.2 V nm-1, ubiquitin displayed competition between internal structure-maintaining molecular interactions and the external orienting force, which disrupted the local structure in certain regions of the protein. Moreover, relative to hydration water, bulk water showed a greater tendency to align with the electric field, indicating that the presence of protein caused hydration water to acquire rotational mobility different from that in a pure-water system. The differential influence of the applied electric field on the hydration and bulk water surrounding ubiquitin will be common to almost all (nonmembrane) biomacromolecules. Our findings highlight the importance of local dipoles and their electric polarizability even in net-uncharged biomolecules.

Transition from nanobubble-induced-blockage to enhancing water flux

Gas bubbles often form and accumulate in microfluidic devices, which is a critical obstacle in microfluidic applications. Here, we report by molecular dynamics simulations that “nanobubbles” can form and hinder water flow through the carbon nanotubes which are core components of nanofluidic devices. It is exceedingly difficult to remove the “nanobubble” trapped in the nanotube by a conventional method of hydrostatic or osmotic pressure gradient. Ratchet-like mechanics is applied to resume water flow powered by mechanical resonance. Interestingly, the water flow is even faster as compared to the pure water system without nanobubbles. Our findings provide a new means for solving pore-blocking problems in nanochannels and have potential applications in the design of high-flux nanofluidic systems.

Experimental study and chemical affinity model on the inhibition of CO2 gas hydrate formation

Natural gas and water can form complex cage crystals in oil and gas pipelines under certain conditions. The natural gas hydrate formed after crystal clustering can block the pipeline and affect the operation efficiency of the pipeline, and even cause equipment damage, bringing economic and security problems to enterprises. In the present study, we experimentally investigated the inhibition of CO2 formation hydrate using attapulgite (ATP) and glucose (GLC). The kinetic influence on the formation of CO2 hydrate by the complex pairing of kinetic inhibitor ATP is conducted under the working conditions of 277.15 K and 3.5 MPa. The effect of compound inhibitors on the temperature and pressure conditions, growth process and gas consumption of hydrate formation are revealed. The chemical affinity model of CO2 hydrate formation under a compound inhibitor system is derived and established based on experimental studies. The results show that the combination of GLC and ATP can inhibit the formation of CO2 hydrate to varying degrees, prolong the induction time of hydrate, and reduce the consumption of CO2. The optimized experimental studies demonstrate that the best inhibitory compound system is 15 mg/mL GLC + 1.00 mg/mL ATP. Compared with the pure water system and single 15 mg/mL GLC system, the induction time is extended by 122.61% and 122.23%, while the gas consumption is reduced by 23.72% and 3.41%. The results provide new ideas and methods for the prediction of hydrate formation in the compound inhibitor system for the safe operation of oil and gas pipelines.

Bismuthene nanosheets prepared by an environmentally friendly method and their thermoelectric epoxy nanocomposites

Theoretical research has predicted high thermoelectric performance for bismuthene nanosheets, but it is a great challenge to prepare these nanosheets due to low efficiency and intensive oxidation. We herein report an efficient, environmentally friendly preparation method for bismuthene nanosheets, each being 1–1.5 nm thick in average, through mechanochemical treatment with an ethanol system. The system was found to prevent adverse oxidation in comparison with a pure water system. Although neither the oxidation reactions nor the exfoliation could significantly change the Seebeck coefficient of bismuthene nanosheets, their power factor was measured as 155.6 ± 15.4 μW·m-1K-2. An epoxy nanocomposite was prepared containing 99 vol% of bismuthene nanosheets, to create a thermoelectric generator. It converted a temperature gradient of 11°C generated by human body into an electrical output of 18.62 nW. Our mechanochemical exfoliation method for the preparation of low-oxidation bismuth nanosheets offers insights for large-scale fabrication of nanosheets and their composites for industrial applications. It advances the field of thermoelectric nanocomposites.

The effect of salinity on the pressure susceptibility of the NF270 membrane

To avoid structural changes within nanofiltration membranes during operation, pre-compaction of filtration membranes is usually performed. However, even after pre-compaction, the NF270 membrane has previously been shown to display a level of pressure susceptibility in pure water systems, particularly evident at low pressures. For the first time, this study provides experimental evidence for the effect of salinity on the pressure susceptibility of the NF270 membrane. Permeability was shown to decrease with increasing salinity up to 189 mM MgSO4, with the largest reduction (22 %) observed at the lowest MgSO4 concentration (31.49 mM MgSO4). A significant reduction (35 %) in the membrane susceptibility was also observed following the introduction of MgSO4 to a concentration of 31.49 mM. A mathematical expression, developed for pure water systems, was modified to account for salinity effects and fitted the experimental data well for concentrations up to 0.2 M. These results are explained by compaction of the membrane polymer, due to either charge neutralisation at the membrane surface, or electric double layer compression, or both. However, further increases in salinity had no significant effect on membrane susceptibility, suggesting that salt induced membrane compaction occurs at very low concentrations.

Facile synthesis of carbon dots incorporated carbonized pomelo peel by one-step method for enhanced solar evaporation

Solar evaporation can be enhanced by incorporating carbon dots (CDs) decorated onto base materials. However, existing literature primarily focuses on multi-step synthesis methods involving separate preparation of CDs and base materials. This study proposes a novel one-step method for synthesizing CDs decorating carbonized pomelo peel (CDs@CPP) composites for solar evaporation. The pomelo peel itself acted as the carbon source and base material. To demonstrate the performance of the proposed method, the properties of CDs@CPP were compared with those of another CDs-decorated carbonized pomelo peel composite (CDs-CPP) prepared through the conventional multi-step method. Additionally, the role of CDs was also demonstrated by comparing carbonized pomelo peel (CPP) and its CDs-based composites (CDs-CPP). The resultant three different materials (CPP, CDs-CPP, and CDs@CPP) were then characterized to identify their structure, chemical components, wettability, and other properties. The results demonstrate significant improvements in sample properties due to the introduction of CDs and the advantages of the proposed one-step method. The resultant materials were then tested in solar evaporation experiments, revealing that CDs-CPP observed an increase of around 3 times and 1.5 times in the evaporation rate compared with the pure water system and CPP system, respectively. Notably, these values increased to 5 and 2.2, respectively, in the CDs@CPP system. Moreover, CDs@CPP exhibited a solar-to-vapor conversion efficiency of 120%, with an evaporation rate of 2.43 Kg·m−2·h−1 at one sun illumination. This work highlights the performance of our proposed one-step method and provides new insights for synthesizing CDs decorated biomass composites for efficient solar evaporation.

(TA-APTES)Plus: A rapid, green and universal coating for membrane modification toward oil-in-water emulsion separation

In our previous work, we have developed tannic acid (TA)-3-aminopropyltriethoxysilane (APTES) coating (TA-APTES coating) for membrane surface modification, which has several distinct advantages: suitable for various membranes, hierarchical structures, mild conditions, etc. In this work, we developed (TA-APTES)Plus coating, which exhibits much better performance than our previous TA-APTES coating: (1) Much faster: The membrane modification process based on our (TA-APTES)plus coating only needs 40 min, while our previous TA-APTES coating needs 12 h; (2) Much greener: The (TA-APTES)Plus coating is prepared in pure water system, without Tris-HCl buffer solution, without oxidants such as H2O2 or KIO4; (3) More stable: The (TA-APTES)Plus coating can remain superhydrophilic even after 30 days, which cannot be achieved by our previous TA-APTES coating. Moreover, the (TA-APTES)Plus coating reserves the advantages of our previous TA-APTES coating, such as universality and distinct hierarchical structures. Take polypropylene (PP) microfiltration membrane as an example, the PP membrane modified by (TA-APTES)Plus not only possesses ultra-high pure water flux (11,990 L m−2 h−1 bar−1) and high separation efficiency (>99.8%) of oil-in-water emulsion, but also exhibits excellent stability. Considering its much better performance, the (TA-APTES)Plus coating may become a more powerful tool for membrane modification toward oil/water separation.

The intrinsic effects of using rhenium gaskets in hydrothermal diamond anvil cell experiments on background fluorescence, contamination, and redox control

Because of the great stiffness and high melting point of rhenium (Re) metal, Re gaskets are widely used in hydrothermal diamond anvil cell (HDAC) experiments that involve aqueous fluids and even hydrous melts under high pressure–temperature (P–T) conditions. This metal was usually considered chemically inert in hydrothermal experiments, but some concerns have been raised about its reactivity with the fluids. Therefore, this communication addresses the intrinsic effects of using Re gaskets in HDAC experiments, including background fluorescence in Raman spectroscopy, contamination, and redox control. A series of hydrothermal experiments involving rhenium were performed in pure water, H2O-NaCl, and SiO2-COH systems using the HDAC up to 28.9 kbar and 850 °C and fused silica capillary capsule (FSCC) up to 87 bar and 300 °C, and Raman spectroscopy was employed for in situ analysis. The results indicate that (1) strong background fluorescence, often occurring between 200 and 700 °C, is caused by the dissolution of Re gaskets and the formation of aqueous species of Re with a low oxidation state, such as a Re2+cation and eventually, its hydroxide complexes; (2) in addition to the fluorescent Re species and unwanted carbon species produced from the diamond-water reaction catalyzed by Re, a considerable amount of ReO4−, which does not cause fluorescence and shows a dominant Raman peak at ∼970 cm−1, is detected in the fluids either in situ at high temperatures above 700 °C or under cooling conditions, and it can reduce the activity of H2O and the pH of the fluids and interfere with the assignments of Raman peaks of other species in the samples; and (3) the production of oxidizing aqueous species at high temperatures, including ReO4− and CO2, is attributed to the substantial loss of H2 and the corresponding increase in oxygen fugacity. Because of these intrinsic effects of using Re gaskets in HDAC experiments, implications for hydrothermal experiments are discussed with several previously reported examples such as the discrepancy in the solubility of rutile in water under elevated P–T conditions. Based on the results of the current and previous studies, four suggestions have also been made to minimize the unwanted effects of using Re gaskets, including the generation of a reduced experimental condition, a pre-heating treatment of Re gaskets, a gasket pre-indentation approach, and a gold-lined gasket method. Armed with the knowledge of these intrinsic effects as well as the advantages of using different HDAC metal gaskets, the researchers will be able to create appropriate experimental designs.

Morphology Study of Hydrate Shell Crystal Growth on a Microbubble Interface in the Presence of Additives

Bubble dispersions in water can be observed in both wellbore or subsea piping as well as subsea gas seepages. The hydrate risk in subsea pipelines or methane leaks from the cold spring into seawater can be strongly influenced by the hydrate crystal growth on bubbles. In addition, the bubbling method has been proven to be an effective method to enhance the gas–liquid mixing pathway and promote hydrate’s rapid formation in the application of hydrate-based technologies, yet the microscopic mechanism of hydrate film growth on the bubbles still needs to be further clarified. In this study, the hydrate crystal growth morphology evolution at the microbubble interface was investigated by a high-resolution microscope combined with the temperature-controlled stage. The results showed that the hydrate crystals nucleated rapidly at the bubble interface to form a hydrate shell-coated structure in a pure water system. The defect growth mechanism dominated the hydrate crystals growth at the bubble interface in additive solutions. Hydrate did not nucleate directly on the surface of bubbles but by trapping guest molecules around the shrinking bubbles to form aggregated hydrate agglomeration in the presence of surfactants. In addition, the bubbles tend to provide a steady stream of gas source for hydrate formation. The growth of hydrate shells contributed to a normal distribution of bubble shrinking rates, with an average rate of 9 μm/s in 0.5 wt % NaCl solution. The existence of a high concentration of ions or organic molecules at the microbubbles’ interface and the exclusive effect played a dominant role in the process of hydrate formation. In addition, it was found that the repulsive effect of ions at the bubble interface on hydrate formation was weak under a high subcooling degree. However, other organic molecule promoters still accelerated the hydrate’s formation rate because they increased the dissolution and diffusion rate of gas in solution. The results are expected to strengthen further the applications relating to hydrate-based phase transition promotion technology in the industry in energy storage, gas separation, or inhibition techniques in flow assurance of the offshore industry.

Co-deposition characteristics of hydrates and sands in gas-salty water-sands flow system

The study of hydrate flow assurance is critical for the efficient and safe development of natural gas hydrates. The natural gas produced by the dissociation of hydrate may re-hydrate in the gathering pipeline, and even lead to the blockage of the gathering pipeline. However, the co-deposition mechanism of the Micron-sized Sand Particles(MSPs) produced in the exploitation, and natural gas hydrate particles during pipeline transportation is still unclear. Therefore, the hydrates and MSPs slurry flow law and co-deposition mechanism are studied by horizontal high-pressure flow loop experiments. A new method to calculate the thickness of the deposition layer for water-dominant systems is proposed. Then, based on the variation of deposition layer thickness, the solid deposition process and flow behaviors are discussed in the pure water system, the salt-containing system, the sand-containing system, and the salt-sand coexistence system, respectively. The results show that the hydrate-MSPs co-deposition process is divided into five stages in the salt-sand coexistence system: the initial deposition stage, hydrate formation and adhesion on the pipe wall stage, rapid deposition stage, deposition layer sloughing stage, and stable deposition stage. And the hydrate-MSPs co-deposits in various stages are characterized by the Hydrate Aggregates Deposition Rate, the Hydrate Aggregates Deposition Layer Thickness, and the particle Chord Length Distribution. The influence of sand particle concentration and initial flow velocity on the hydrate-MSPs co-deposition process in the salt-sand coexistence system is also explored. In addition, the interaction between particles in the deposition process is revealed by Particle Vision and Measurement. The findings of this work provide insights into the solid deposition process in the salt-sand coexistence system, which is beneficial for flow assurance in natural gas hydrate production.

Synthesis of 2D/2D structural Ti3C2 MXene/g-C3N4 via the Schottky junction with metal oxides: Photocatalytic CO2 reduction with a cationic scavenger

A series of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites were successfully fabricated by the integration of 2D Ti3C2 MXene and 2D polymeric carbon nitride (CN) with ZnO and Cu2O. The HF etching on Ti3C2 MXene offered significant improvement for the photocatalyst fabrication, while the close 2D/2D junction of Ti3C2/CN created the Schottky junction to enable proficient electron transfer in the ternary nanocomposite. Next, the junction of 2D MXene and 2D CN with the metal oxides (Cu2O and ZnO) prevented the quick recombination of photoexcited electrons and holes and contributed multiple electron pathways for the CO2/CH3OH process. At the same time, the formation of analogue Z-scheme heterojunctions through the synergistic effect of 2D Ti3C2 MXene and 2D metal-free CN with ZnO contributed to the rapid separation and transfer of photogenerated charge carriers. As a result, the photocatalytic CO2 reduction activity of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites was significantly enhanced. Meanwhile, adding a Na2SO3 sacrificial electron donor with pure water and NaHCO3 solvent system supply in CO2 photoreduction experiments contributed to the formation of CH3OH. In particular, the yield of CH3OH was up to 18.72% and 19.98%, 5times and 6-times fold than the pure Cu2O and ZnO, while 3-times fold than the TCCN in a water system. In a NaHCO3 solvent with the sacrificial electron donor, the CH3OH rates over Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O were 22.41% and 20.12%. Taking into account the chemical and structural tunability of ternary nanocomposites, the excellent photocatalytic ability of Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O could be used in the future production of hydrocarbon fuels, as well as increasing the possibility of using 2D MXene in photocatalyst fabrication.

Electrodepositing NiCo-double hydroxides with high electrochemical performance by adjusting the rheological behavior of electrolyte

Electrodeposition is a facile and convenient method to prepare NiCo double hydroxides for binder-free electrode materials that are equipped with superior electrochemical performance. But the samples synthesized by electrodeposition exhibit monotonous nanosheets array morphology and poor durability. In this paper, we proposed a novel electrodeposition way by introducing a water-soluble polymer, i.e. polyacrylamide (PAM) with different molecular weights (Mw) into the electrolyte to manipulate the morphology and electrochemical property. By adjusting the rheological behavior of the electrolyte, the NiCo hydroxides with different morphology can be acquired as the active materials can grow along the soft template constructed by polymer chains. The morphology of the active materials varies along with the concentration and molecular weight of the polymer as well. Furthermore, amorphous phases are accompanied by the crystal during the deposition. Benefit from the unique multilevel morphology and high specific surface area, the electrodes synthesized at the electrolyte containing an appropriate concentration of polymer exhibit higher specific capacitance and longer cycling performance than that prepared in the pure water system. This work provides a novel strategy to prepare double hydroxides with diverse morphology and electrochemical performance.

Interfacial tension of water near to critical conditions by using the pendant drop method: New experimental data and a correlation based on the parachor method

The interfacial tension (IFT) at vapor/liquid equilibrium was measured for the pure water system following the saturation line (further named as water (l)/water (v) or pure water) as well as for the binary water/nitrogen system (further named water/nitrogen). In order to obtain vapor/liquid IFT data, the pendant drop method was applied in a high-pressure-high temperature view cell. The vapor/liquid IFT of the binary water/nitrogen system was investigated at 10, 15 and 18 MPa and for temperatures in the range of 323–598 K. For the water (l)/water (v) system, the temperature ranges from 423 K to 623 K at the respective saturation pressure. The IFT of the binary water/nitrogen system is in a similar range compared to the IFT of the pure water system up to temperatures of 500 K although showing an influence of the nitrogen pressure due to solubility and adsorption effects. At temperatures above 500 K, the IFT starts to considerably differ as a function of temperature, reflecting the respective phase behaviour of both systems. The parachor method following Macleod-Sugden was used to correlate the IFT of the binary water/nitrogen system, as well as the pure water system. The equation is in good agreement with the experimental results, showing an AAD of 4.97% for the water/nitrogen system and 3.02% for the pure water system. The obtained experimental results are further in good agreement with comparable literature data.

A novel Sunflower-like MOF@COF for improved photocatalytic CO2 reduction

Metal-organic framework (MOF) and covalent organic framework (COF) hybrid materials have drawn much research attention in the field of photocatalysis due to their complementary advantages, massive specific area, customizable structure and performance, and suitable band gap. Herein, the MOF@COF hybrid platform with a novel sunflower-like strong π-π bond stacking was formed by introducing the preformed synthetic COF into the MOF precursor solution and modulating its morphology by vacuum thermal-assisted growth. More importantly, the synthesized MOF on the COF hybrid platform with multiple active centers exhibits excellent catalytic activity in the sacrificial agent-free photocatalytic CO2 reduction reaction under simulated sunlight. Additionally, the maximum CH4 yieldrate of the synthesized PCN-222-Cu@TpPa-1 (1:2) reached 21.27 μmol g-1h -1, with an AQY (apparent quantum yield) about 10.46 % (in pure water system, λ = 550 nm) and a methane selectivity of about 27.25 %. The best performance of PCN-222-Cu@TpPa-1 is approximately 4.3 times higher than that of pure PCN-222-Cu and 100 times higher than that of the reported NH2-MIL-125(Ti) NMB. The selectivity of the products CO and CH4 can be improved by adjusting the ratio of MOF and COF. Finally, the goal of providing an optimal photocatalytic platform for increased photocatalytic CO2 reduction with highly effective morphology-tunable MOF@COF was expanded upon by a potential photocatalytic reaction mechanism, which was suggested based on the analysis of experimental results.

Kinetic Properties of CO2 Hydrate Formation in the Wax-Containing System at Different Concentrations

Precipitation of wax crystals and hydrate formation during deep-sea multiphase pipeline transportation would limit pipeline transportation flow and even trigger accidents. It is necessary to study the hydrate formation behavior in the wax-containing system. This paper utilized a mixture of number 60 Kunlun paraffin wax and number 2 industrial white oil to simulate the wax-containing system, and the CO2 hydrate was formed in the wax-containing system. The morphology of CO2 hydrate formation was captured by the microscope and the charge-coupled device imaging system. In this study, the influences of the wax crystal concentrations on the induction time and cumulative gas consumption of hydrate formation were investigated, and the effects of wax crystal precipitation on the CO2 hydrate nucleation mechanism were discussed. The experimental results indicated that, for the wax crystal concentrations of 1.50 and 2.50 wt %, the induction time of CO2 hydrate formation in the wax-containing system was reduced by 29.23 and 69.23% compared to that in the pure water system, respectively. However, for the wax crystal concentration of 0.50 wt %, the induction time of CO2 hydrate formation in the wax-containing system was increased by 130.77% compared to that in the pure water system. The reason for this was that the precipitation of wax crystals at high concentrations increased the chance of heterogeneous nucleation and the probability of heterogeneous nucleation increased with the increase of wax crystal concentrations. However, for the wax crystals at low concentrations, it not only lowered the chance of cross nucleation but also increased the mass transfer resistance for gas diffusion, thereby resulting in the increase of the induction time of hydrate formation. It was also found that, with the increase of the wax crystal concentrations, the cumulative gas consumption during hydrate formation decreased gradually. When the wax crystal concentration increased to 2.50 wt %, the cumulative gas consumption was reduced by 32.96% compared to that of the pure water system. The experimental results obtained in this study were helpful for understanding the kinetic characteristics of hydrate formation in the wax-containing system, which is meaningful for the pipeline flow assurance, safety, and economic security of pipeline transportation as well as the development of carbon capture and storage.

Effect of a Terminated PVCap on Methane Gas Hydrate Formation

Polyvinylcaprolactam (PVCap) is an economic kinetic inhibitor for hydrate formation in pipelines during oil and gas transportation. However, its application is limited because of the low inhibition performance under certain conditions. In this work, a modified PVCap on its chain end is proposed. 2-amino-3-propionic acid mercapto-terminated polyvinyl caprolactam (PVCap-NH2-COOH) was synthesized and its performance as a KHI for methane hydrate formation was evaluated under different conditions. Results showed that the performance of PVCap-NH2-COOH as a KHI was better than that of PVCap at the same concentrations. Gas hydrate samples with 1 wt.% PVCap-NH2-COOH were measured using Raman spectroscopy, XRD, and cryo-SEM. PVCap-NH2-COOH had a selective action on a specific crystal surface of the hydrates and could prevent methane molecules from entering large cages. Its inhibition ability increased with the decrease in the occupancy rate of large cages. The morphology of the gas hydrate crystal changed from porous in a pure water system to a chaotic but compact structure state in the system with PVCap-NH2-COOH.

Preparation of mesoporous La2Zr2O7 aerogel via non-alkoxide sol-gel process with different solvent systems

Mesoporous La2Zr2O7(LZO) aerogels were successfully prepared by combining the epoxide-mediated sol-gel method with non-alkoxide salts. Gelation was controlled by adding propylene oxide to the solution of nitrate. The effect of solvent systems of pure water, pure ethanol, and a mixture of water and ethanol on the sol-gel was investigated. Gels cannot be obtained using either pure water or mixed solvent systems. However, LZO aerogels synthesized with pure ethanol solvent exhibited a mesoporous structure with a surface area of 413.2 m2/g and an average pore size of 12.3 nm. The prepared LZO aerogels had an amorphous structure containing some organic components. After heat treatment, the organics were pyrolyzed and the LZO started to crystallize. At about 1000°C, the LZO transformed from fluorite structure to pyrochlore structure. In addition, LZO still maintains a good skeletal structure after calcined at 1000°C. Above 1200°C, the grains start to stick as well as the grain size increases significantly due to the sintering of nanocrystalline LZO grains. The surface area can be maintained at 149.6 m2/g after heat treatment at 600°C and dropped to 9.3 m2/g after 1400°C for 3h.

The selective heating effect of microwave irradiation on a binary mixture of water and polyethylene oxide: a molecular dynamics simulation approach.

In this study, we investigate the molecular mechanisms of a microwave-driven selective heating process by performing molecular dynamics simulations for three different systems including pure water, pure polyethylene oxide (PEO), and water-PEO mixed systems in the presence of a microwave with two different intensities of electric field such as 0.001 V Å-1 and 0.01 V Å-1 at a frequency of 100 GHz. First, from performing molecular dynamics simulations of CO and CO2 in the presence of the microwave, it is confirmed that the molecular dipole moment is responsible for the rotational motion induced by the oscillating electric field. Second, by analyzing the MD simulations of the pure water system, we discover that the dipole moment of water exhibits a time lag with respect to the microwave. During the heating process, however, the temperature, kinetic, and potential energies increase synchronously with the oscillating electric field of the microwave, showing that the heating of the water system is caused by the molecular reaction of water to the microwave. Comparing the water-PEO mixed system to the pure water and pure PEO systems, the water-PEO mixed system has a higher heating rate than the pure PEO system but a lower heating rate than the pure water system. Therefore, we conclude that heating the water-PEO mixed system is driven by water molecules selectively activated by microwave irradiation. We also calculate the diffusion coefficients of water molecules and PEO chains by describing their mean square displacements, demonstrating that the diffusion coefficients are increased in the presence of microwaves for both water and PEO in pure and mixed systems. Lastly, during the microwave heating process, the structures of the water-PEO mixed system are altered as a function of the intensity of electric field, which is mainly driven by the response of water molecules.

Ice recrystallization inhibition mechanism of zwitterionic poly(carboxybetaine methacrylate).

Understanding the ice recrystallization inhibition (IRI) mechanism is of fundamental importance for the rational design of novel antifreeze protein mimetics and reducing IR-related damage. In this communication, using quantitive experimental methods and molecular dynamics simulations we demonstrate that zwitterionic poly(carboxybetaine methacrylate) (PCBMA) can serve as a novel IRI-active substance. This work unravels the atomic-level details of the IRI mechanism of zwitterionic antifreeze protein mimetics and provides insight into the development of next-generation antifreeze protein mimetics.

Efficient H2 Production from PET Plastic Wastes over Mesoporous Carbon-Supported Ru-ZnO Catalysts in a Mild Pure-Water System

The massive consumption of plastic is posing severe pollution-related challenges globally. As the most abundant polyester plastic, polyethylene terephthalate (PET) waste represents a largely untapped resource for generating chemicals and fuels. However, the current widespread use of alkali/organic solvents and the complex processing of PET reduce its environmental sustainability. Herein, a novel and simple one-pot strategy was first reported for the catalytic conversion of PET into H2 fuel and terephthalic acid in a pure-water system under mild conditions. A high H2 yield of 19.97 mol/kgPET and carbon conversion efficiency of 97.22% were obtained for the Ru-5ZnO/mesoporous carbon (MEC) catalyst at a low temperature of 250 °C. This process proceeds through tandem catalytic reactions with an initial PET depolymerization step, followed by in situ aqueous phase reforming (APR) of ethylene glycol of Ru. Remarkably, ZnO inhibited the deactivation of Ru/MEC in the PET depolymerization stage, causing an increase in H2 production from the in situ APR stage. Importantly, this strategy was successfully applied to four types of real-world PET waste and their mixtures, demonstrating that it has considerable potential in practical applications and provides a sustainable and clean solution to the plastic waste problem.