Strong Electrostatic Forces Research Articles

A recombinant L-threonine aldolase with high catalytic efficiency for the asymmetric synthesis of L-threo-phenylserine and L-threo-4-fluorophenylserine.

To develop robust variants of L-threonine aldolases (L-TAs), potent catalysts for synthesizing asymmetric β-hydroxy-α-amino acids, it is necessary to identify critical residues beyond the known active site residues. Through virtual screening, a neglected residue Asn305, was identified as critical for catalytic efficiency. Subsequent site-saturation mutagenesis led to a potent variant N305R which exhibited excellent conversions of 88%conv (87%de) and 80%conv (94%de) for the synthesis of L-threo-phenylserine and L-threo-4-fluorophenylserine respectively. This variant not only outperformed the template enzyme, but also represented a promising L-TA for synthesizing the two β-hydroxy-α-amino acids. It was suggested that Arg305 of the variant N305R generated strong cation-arene interaction and electrostatic force with the intermediates, leading to strengthened binding, enhanced L-threo favored orientation and wider entrance. Our work not only provided an excellent variant N305R, but also suggested the crucial function of a neglected residue Asn305, which offered valuable experiences for other L-TA studies.

A label free ratiometric sensing of heparin using dynamic modulation of monomer–excimer equilibrium of coumarin 7

Heparin (Hp) is a multi-negatively charged polysaccharide with diverse physiological roles, particularly in regulating blood coagulation. Its clinical use as an anticoagulant requires a precise monitoring due to potential adverse effects at elevated levels. Therefore, there is a significant demand for an immediate, label-free, and user-friendly method to accurately quantify heparin (Hp). Herein we have explored a novel ratiometric sensing approach using coumarin-7 (C7) dye for precise Hp quantification. At pH 3, the protonated form of C7 undergoes aggregation upon interacting with polyanionic Hp via strong electrostatic forces. Consequently, there is alteration in the dynamics of the monomer-aggregate equilibrium for C7 in solution, resulting in the appearance of a new emission peak at ∼660 nm upon successive decline of the monomer peak at ∼512 nm. This leads to the generation of a ratiometric signal, which shows a nice linear response up to 6.8 μM of Hp to achieve limit of detection (LOD) of 89.6 nM for Hp in citrate buffer. Such ratiometric optical behaviour of C7 is not seen for any other interferants, which may be present in complex bio-matrices and thus, showcases a promising avenue for accurate and reliable Hp quantification even in complex biofluids. Additionally, the assembly C7 − Hp exhibits excellent responsiveness towards ionic strength of the medium, further extending its application towards the detection of an important bio-analyte, protamine (Pr). Importantly, this approach of ratiometric sensing strategy provides more accurate quantification due to its high reproducibility, minimal susceptibility to environmental effects, and self-calibration properties. The detailed spectroscopic analysis elucidates the dynamics of the C7 − Hp interaction, paving the way for advanced biosensing applications.

Selective adsorption of Cu(II) on amino-modified alginate-based aerogel: As a catalyst for the degradation of organic contaminant

In this study, amino-modified graphene oxide(NGO) was prepared by introducing amino functional groups. Based on the cross-linking between Ca(II) and sodium alginate (SA), associated with dense slit-like pore resulted from the nano-sheet accumulation of NGO and montmorillonite (MMT), composite aerogels (NGM) with stable pore structure were constructed, thus it realized the selective recovery of hydrated copper ions in complex wastewater systems. Raman analysis and density functional theory calculation confirmed the construction of amino-modified defect GO and significantly improved its chemical reactivity, which laid the foundation for the construction of slit pore structure of NGM (SEM can confirm). At the same time, it proposed that the good selective adsorption of Cu(II) on NGM was related to the synergism of strong electrostatic force, ion exchange and complexation based on the characterizations of FT-IR and XPS. In order to realize the value-added utilization of NGM aerogel (NGMC) after adsorbing Cu(II), NGMC was used as a catalyst to degrade organic pollutants in wastewater. Systematic experiments shown that NGMC can degrade organic pollutants with a degradation efficiency >80 %. In summary, NGM had a broad application prospect for selective recovery of Cu(II) from complex wastewater systems without second pollution.

Deep trapped bipolar heterocharges enable electret nanofibrous membranes for high-efficiency PM0.3 filtration

Recently frequent global pandemic outbreak triggers the demand of high-efficiency aerosol filtration materials. Most of traditional electret air filters can hardly achieve high efficiency (>99.99 %) due to limited charge density and inappropriate charge distribution. The influence mechanism of nanofibers bipolar heterocharge configuration on electrostatic capture of airborne particles is still confusing. Herein, a novel strategy to create high-efficiency air filters based on electret nanofibrous membranes with deep trapped heterocharge is reported. Space charges and dipole charges with opposite polarity are formed in electrospun membranes composed of different polymers under in-situ charge injection and electric poling during electrospinning. Nanoscale spatial surface potential mapping on individual nanofiber characterized by Kelvin probe force microscopy demonstrates bipolar heterocharge distribution. Numerical simulation shows that fiber heterocharge distribution endows the electret membrane with greater electrostatic field intensity gradient, resulting in stronger electrostatic force between nanofibers and airborne particles. With bipolar heterocharge configuration and bimodal fiber diameter distribution, the nanofibrous membranes exhibit high-efficiency low-resistance filtration property against 0.3 μm NaCl particles (99.994 %, 97.4 Pa) at 5.3 cm s−1. Furthermore, benefiting from charges with deep trap energy of 1.12 eV, the membranes still maintain 99.972 % filtration efficiency after 40 h exposure in 95 % relatively humidity. The prepared membranes brings new insight in the design of high-efficiency and long-term stability air filtration materials for public health precaution. This study not only reveals influence mechanism of nanofibers heterocharge distribution on electrostatic attraction, but also provides useful guidance for fiber charge configuration design to improve aerosol filtration performance of electret filters.

Acid-resistant chitosan/graphene oxide adsorbent for Cu2+ removal: The role of mixed cross-linking and amino-functionalized

Copper ions in wastewater pose a significant threat to human and ecological safety. Therefore, preparing macroscopic adsorbents with reusable and high adsorption performance is paramount. This paper used graphene oxide as the adsorbent and chitosan as the thickener. Additionally, a silane coupling agent was employed to enhance the acid resistance of chitosan, and amino-modification of graphene oxide was performed. Macroscopic adsorbents with high adsorption capacity were fabricated using 3D printing technology. The results show that all five proportions of inks exhibit good printability. Dissolution experiments revealed that all materials maintained structural integrity after 180 days across pH values. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) confirmed the successful preparation of the materials. Adsorption experiments showed that the best performing material ratio was 8 wt% graphene oxide and 7 wt% chitosan. Adsorption kinetics and isothermal adsorption experiments demonstrated that the adsorption process occurred via monolayer chemisorption. The adsorption process was attributed to strong electrostatic forces, van der Waals forces, and nitrogen/oxygen-containing functional group coordination. Cycling experiments showed that the material retained good adsorption performance after 6 cycles, suggesting its potential for practical heavy metal treatment applications.

Functional metal-organic framework membranes with uniform unsaturated pyridine-nitrogen sites as separators for high-performance lithium metal batteries

Lithium metal batteries are a promising successor to lithium-ion batteries due to high specific capacity, low density, and low electrochemical reduction potential. However, inhomogeneous lithium deposition on the Li surface will result in the formation of lithium dendrites and eventually puncture the separator and cause a short circuit. Herein, a functional metal-organic framework membrane with uniform unsaturated pyridine-nitrogen sites is synthesized via coating UiO-67-BPY (2,2 -bipyridine- 5,5 -dicarboxylic acid, named as BPY) on a commercial polypropylene (PP) separator. By replacing the benzene ring with a pyridine ring, the functionalization and porosity of MOF is fully utilized while maintaining the excellent porosity and pore size of MOF. The Li-ion transference number (tLi+) with the functional separator is 0.69 and the ionic conductivity is improved by order of magnitude compared to a plain PP separator. The N atom of the pyridine ring on the UiO-67-BPY has a strong electrostatic interaction force, and a weak coordination bond (N–Li bonding lattice) is formed between N and Li, which leads to an increase in the concentration of free lithium ions and makes their distribution more uniform. This allows lithium ions to migrate more smoothly, which is conducive to ionic conductivity and hinders dendrite formation.

Theoretical study on the capture of toxic gases by ionic liquids encapsulated in assembled belt[14[pyridine

In the current study, self-assembled belt[14]pyridine (BP) encapsulated IL (tetramethylammonium chloride (TMACl)) is theoretically explored to capture greenhouse gases (GHGs) at B3LYP-D3/6-311G(d,p) level of theory. The encapsulation of TMACl in assembled belt[14]pyridine is thermodynamically feasible as revealed through high interaction energy value of −50.7 kcal/mol. Moreover, the results of capturing of gas molecules (SO2, CO2, CO and CH4) show that attractive forces involved in capturing of gases are strong van der Waals forces i.e., London dispersion forces and electrostatic interactions. The synergic effect of self-assembled belts and ionic liquid results in significantly high interaction energy values ranging from −7.88 to −25.92 kcal/mol for capturing of gas molecules. Furthermore, the interaction between BP-TMACl and gas molecules is studied in detail through natural bond orbital (NBO) analysis. NBO results show the charge transfer between the fragments (BP-TMACl and gases) which is further validated through EDD analysis. The charge shifts towards all of the captured gas molecules but the most prominent change in NBO charges is shown by captured SO2. The successful charge transfer indicates better interaction in the designed systems. Additionally, the type and strength of interactions involved in the process of encapsulation is studied through quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCI) analysis. NCI analysis clearly shows that gases are captured by BP-TMACl complex through strong van der Waals forces. However, in capturing of SO2, strong electrostatic attractive forces are also involved. The nature of attractive forces is confirmed through QTAIM analysis. Furthermore, the relation between recovery time and desorption energy of captured gas molecules has been studied. The strongest absorption for SO2 results in prolonged recovery time for it (as compared to the other gas molecules). AIMD analysis is performed to find the dynamical stability of assembled-belts before and after loading ionic liquids along with gases to be captured. These results reveal that assembled-belts are suitable for encapsulation of ionic liquids along with capturing of gases. Overall, the best results are shown for SO2 capture. The study intends to deliver valuable information on the important progress in the environmental-remediation field and we hope our work is going to inspire more investigators to provide novel research on such challenging tasks.

Spiral Structured Cellulose Acetate Membrane Fabricated by One-Step Electrospinning Technique with High Water Permeation Flux

A functionally graded membrane (FGM) with a special spiral-structured cellulose acetate (CA) membrane was prepared by electrospinning under different collection distances. The membrane morphology was analyzed by scanning electron microscopy (SEM). FESEM images revealed that the high concentration shows the formation of fibers with an irregular diameter, with a large diameter distribution range. The fiber collected at a short distance of 10 cm experiences the strong electrostatic force, resulting in the short flight time for the polymer jet. This causes the bending instability of the polymer jet forming the comparatively thick fiber diameters, whereas the fiber collected at 15 cm shows the presence of a smooth, homogeneous diameter. Furthermore, the water flux of the membrane was determined using 50 mL of Amicon stirred cells. The fiber collected at different distances showed diameter variation, which is used to design a special spiral structure on the membrane by auto-moving the collector between the fixed distances of 10–20 cm. This technique will reveal a new approach for the fabrication of a special spiral structure on the nanofibrous membrane for different biomedical applications from different polymers. Meanwhile, the fabricated FGM with a special spiral-structure CA membrane demonstrates high water permeation flux.

Effects of surface property on loading octaaza bis-α-diimine Ni complex, charge separation, and H2 production activity of MnS@ZnS photocatalysts

The MnS@ZnS photocatalyst was prepared using a microwave-assisted solvothermal method. Then, the octaaza bis-α-diimine Ni complex was loaded to prepare a composite photocatalyst. The adsorption of metal complex on photocatalyst depends on the anchoring groups of the Ni complex and the colloidal surface charge of the photocatalyst. The effects of the zeta potential of MnS and MnS@ZnS photocatalysts on the loading of Ni complex, separation of photogenerated carriers, and activity of Ni complex-modified composite photocatalysts were studied. The loading of NiC complex in photocatalysts was analyzed by Raman spectra, TEM line scan, mapping images, and total reflection x-ray fluorescence spectrometer. MnS@ZnS photocatalyst exhibits negative zeta potential that provides a strong electrostatic attraction force between photocatalysts and the Ni complex (Columb attraction), leading to increased Ni complex loading. MnS@ZnS/Ni complex exhibits better photocatalytic activity than MnS/Ni complex. Loading the Ni complex facilitates the photosensitization of photocatalysts, resulting in improved light absorbance. Besides, the electron-hole separation was further improved because the Ni complex acted as a redox mediator, enabling the transfer of electrons from MnS@ZnS to the Ni complex. The H2 production activity of MnS@ZnS/Ni complex photocatalyst reaches 3997 μmol h−1g−1, which is 1.72 times the pristine MnS.

Synergistic π-Conjugation Organic Cathode for Ultra-Stable Aqueous Aluminum Batteries.

Rechargeable aqueous aluminum batteries (AABs) are promising energy storage technologies owing to their high safety and ultra-high energy-to-price ratio. However, either the strong electrostatic forces between high-charge-density Al3+ and host lattice, or sluggish large carrier-ion diffusion toward the conventional inorganic cathodes generates inferior cycling stability and low rate-capacity. To overcome these inherent confinements, a series of promising redox-active organic materials (ROMs) are investigated and a π-conjugated structure ROMs with synergistic C═O and C═N groups is optimized as the new cathode in AABs. Benefiting from the joint utilization of multi-redox centers and rich π-π intermolecular interactions, the optimized ROMs with unique ion coordination storage mechanism facilely accommodate complex active ions with mitigated coulombic repulsion and robust lattice structure, which is further validated via theoretical simulations. Thus, the cathode achieves enhanced rate performance (153.9mAhg-1 at 2.0Ag-1) and one of the best long-term stabilities (125.7mAhg-1 after 4,000 cycles at 1.0Ag-1) in AABs. Via molecular exploitation, this work paves the new direction toward high-performance cathode materials in aqueous multivalent-ion battery systems.

Heterointerface Energetics Regulation Strategy Enabled Efficient Perovskite Solar Cells

AbstractIn the domain of perovskite photovoltaics, the heterointerfaces are subject to substantial trap‐assisted non‐radiative recombination, predominantly attributed to the energy offset, interface defects, and the roughness of the contact. This phenomenon at the heterointerfaces, where carrier non‐radiative recombination and energy dissipation occur due to defects and suboptimal energy level alignment, can be principally held accountable for the Voc losses. Herein, a heterointerface energetics regulation (HER) strategy is proposed by introducing potassium trifluoroacetate (KTFA) in the perovskite precursor solution to eliminate the trap defects and optimize surface potential and Fermi level. It is first demonstrated that non‐doping K+ but precipitating at the upper and buried perovskite will improve energy‐level alignment for charge extraction dynamics. In addition, the TFA− exhibits strong electrostatic force with undercoordinated Pb2+ in the buried contact of perovskite and Sn4+ in the SnO2 electron transporting layer. Based on the vacuum flash evaporation green treatment without anti‐solvent, the Rb0.02(Cs0.05FA0.95)0.98PbI0.91Br0.03Cl0.06 and Cs0.05FA0.95PbI3 based device can achieve maximum efficiency of 23.36% and 24.48%, respectively. Further, the modified devices exhibit 92% initial efficiency output after 1200 h of aging. HER strategy for addressing interface defects and bandgap alignment are poised to advance both the performance and stability of perovskite solar cells.

Nanomembrane Approach Reuses Waste, Cleans Produced Water

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213946, “Nanomembranes From Polymeric Waste for Produced-Water Treatment,” by Anton Manakhov, Iaroslav Rybkin, and Fahd I. AlGhunaimi, Saudi Aramco, et al. The paper has not been peer reviewed. _ In the oil and gas sector, produced water is the most significant waste stream. Among the different materials used for water filtration, including ceramics, polymers, and carbon nanomaterials, polymeric nanofibers can be considered a unique solution that can be used as a membrane or an adsorbent. In the complete paper, the authors write that polymeric nanofibers can be prepared from polystyrene waste. Introduction The management of polystyrene trash and recycling creates a significant environmental problem. While most of this substance ends up in landfills, only a small portion of polystyrene is recycled or burned. By turning this trash into products with added value, recycling will become more appealing economically and will result in lower CO2 emissions and less chemical waste dumped on the ground. At the same time, the use of modified nanofiltration membranes for generated-water purification has been a subject of study for many researchers. The complete paper includes a review of the literature dedicated to advances in this approach. Dissolved polystyrene waste can be used as a feedstock in the electrospinning process to create nanofibrous membranes. Electrospinning is one of the more basic methods for producing nanofibers with dimensions ranging from micrometers to nanometers. Strong electrostatic forces are used to overcome the surface tension of a polymer solution or melt. These pressures produce the ejection of charged polymer jets, which dry as they approach a grounded electrode, where they are gathered as nanofibers. In this work, the nanofibrous polystyrene membranes were prepared from discarded expanded polystyrene waste. Initially, polystyrene waste was collected and dissolved in an organic solvent; then, the nanofibrous membranes were prepared by the electrospinning of nanofibers from this solution. The morphology, pore sizes, and other parameters were controlled and optimized by tuning the concentration of polystyrene, the nature of the solvent, and the spinning voltage to form uniformly sized nanofibrous membranes.

Molecular Interaction Mechanism between Aromatic Oil and High-Content Waste-Rubber-Modified Asphalt

High-content waste-rubber-modified asphalt (HRMA) has high viscosity and poor storage stability. HRMA not only improves the properties of road asphalt, but also reduces the environmental pollution caused by waste tires. Enhancing the molecular interaction of waste rubber and asphalt is key to making full use of HRMA. In this paper, aromatic oil was used as the activator for waste rubber. The molecular interaction mechanism between aromatic oil and HRMA was investigated. The radial distribution function, diffusion coefficient, free volume, solubility parameter, and shear viscosity were calculated through molecular simulations. Storage stability, micromorphology, and adhesive force were measured via experiments. The adhesive force of HRMA−1 (4.9 nN) was lower than that of RMA (6.2 nN) and HRMA−2 (5.8 nN). The results show that aromatic oil can promote the dispersion of waste rubber, making the storage of asphalt systems stable. There exists a strong electrostatic force between rubber and asphaltenes and an intermolecular force between rubber and aromatic oil or aromatics, which makes the aromatic oil and aromatics of parcel rubber molecules and waste rubber highly soluble in asphalt. Molecular simulations confirmed the molecular interaction between rubber and aromatic oil, and aromatic oil was shown to reduce the viscosity of HRMA.

Heparin-Mimetic Chitooligosaccharides-Based Monoliths Obtained from C/W Emulsions: Hemocompatibility and Toxin Removal Ability.

Hemoperfusion (HP) is one of the most prominent therapies for treating uremia, hyperbilirubinemia, and acute drug toxicity. The comprehensive performance of currently used porous HP adsorbents needs to be improved due to the impediment to their synthesis strategy. Herein, green carbon dioxide-in-water high internal phase emulsions (C/W HIPEs) were utilized and emulsified with poly(vinyl alcohol) (PVA) for the formation of a heparin-mimetic chitosan oligosaccharides/poly(acrylamide-co-sodium 4-styrenesulfonate) [COS/P(AM-co-SSS)] monolith, which exhibited good mechanical properties, stable swelling performance, hydrophilic properties, anticoagulant effect, and low hemolysis. It showed a strong toxin adsorption capacity (415.2 mg/g for creatinine, 199.3 mg/g for urea, 279.5 mg/g for bilirubin, and 160 mg/g for tetracycline). The adsorption process of porous COS/P(AM-co-SSS) followed the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the porous materials had a strong electrostatic force on creatinine. The removal of creatinine by simulated in vitro blood perfusion was 80.2% within 30 min. This work provides a green preparation strategy for developing novel HP materials, highlighting their potential application value in blood and environmental purification.

Sulfonated Hydrogel Formed via CO2-in-Water Emulsion: Potential in Antibiotic Removal.

Herein, a green, carbon dioxide-in-water high-internal-phase emulsion (C/W HIPEs) was developed and stabilized with polyvinyl alcohol (PVA) for the formation of chitosan oligosaccharide/poly(acrylamide-co-sodium 4-styrene sulfonate) [COS/P(AM-co-SSS)] monolithic porous hydrogel. The obtained monolith was characterized via FT-IR and SEM. The SEM patterns depicted that the monoliths were interconnected, the void sizes were 78.5 µm, and the interconnected pore throats were 28 μm approximately. Mechanical measurement results indicated that the maximum compress stress of the monolith could reach 334.4 kPa at 90% strain, and it exhibited good mechanical stability. After 200 cycles of compression, it could still recover its original shape without cracking. The obtained COS-based monolith was selected to remove tetracycline (TC) for evaluating the adsorptive features of the interpenetrating pore-containing monolith. The monolithic COS/P(AM-co-SSS) hydrogel behaved with strong antibiotic adsorption capacity (1600.4 mg/g for TC). The adsorption process agreed well with the pseudo-second-order kinetic and Langmuir isothermal models. In addition, the porous monolith had a strong electrostatic force on TC according to the thermodynamic study. This work provides a green route for the development of novel monolithic hydrogels and highlights its potential application in the treatment of antibiotic-containing wastewater.

Electrospun heterojunction nanofibrous membranes for photoinduced enhancement of fine particulate matter capture in harsh environment

Particulate matter (PM) pollution has posed a severe threat to the environment and human health. Especially for submicron-level fine particulate PM0.3, it is still difficult to achieve high-efficiency filtration. Herein, we loaded TiO2/g-C3N4 (TCN) heterojunction photocatalyst on polystyrene/polyacrylonitrile (PS/PAN) multiscale nanofiber membranes by a simple one-step blending electrospinning technique. Due to the strong long-range electrostatic force of the built-in electric field, the composite membrane has a remarkably enhanced filtration effect under light. Even under harsh conditions with a high PM0.3 concentration of more than 1,800,000 m−3 and a high flow rate of 25 L/min, it still has a high filtration efficiency of greater than 98.5%, an increase of about 20% compared with dark conditions, and the pressure drop is only low to 94 Pa. More importantly, the electrostatic field can be regenerated with light, and this preparation strategy can be effectively extended to other photocatalyst heterojunctions.

Smart superabsorbent alginate/carboxymethyl chitosan composite hydrogel beads as efficient biosorbents for methylene blue dye removal

The presence of toxic dyes in the aqueous medium has threatened environmental safety, and thereby removing them from wastewater in an efficient way is highly desired. Herein, the efficient biosorbents were successfully fabricated via a facile physical gelation process of sodium alginate (SA) and carboxymethyl chitosan (CMCTS) in an acidic aqueous solution. The as-prepared hydrogel beads not only displayed water superabsorbent properties and pH-responsive swelling characters but also exhibited excellent methylene blue (MB) adsorption capacity removal efficiency with experimental maximum MB adsorption capacity of 2518 and 1005 mg g–1, which are comparable with most reported lignocellulosic and alginate-based hydrogels. The MB adsorption process fitted well in different kinetic and isotherm models and became more heterogeneous in concentrated MB solutions as verified by principal component analysis results. The adsorption mechanism was proposed, and the high dye absorbency was attributed to the strong electrostatic forces between adsorbents and adsorbates. Our current study provides a promising and sustainable composite hydrogels platform targeted to dye decontamination.

Desalination of produced water via CO2 + C3H8 hydrate formation

Recent years have seen increased interest in gas hydrate production as a viable saline water desalination technique. Produced water is the liquid that is extracted from oil and gas fields and is typically salty. The management of produced water is a significant aspect of the petroleum industry because of its potential to serve as a source of fresh water for oil-producing nations with limited access to clean water, growing environmental concerns, and the strict laws governing the discharge of produced water into the environment. In this study, the effect of mixed gas (CO2 + C3H8 (70:30)) hydrate formation in treating produced water and kinetic studies on induction time, moles of gas consumed, rate, water recovery, and water-to-hydrate conversion were experimentally investigated. An aqueous solution with the same ion concentrations was prepared and experiments were performed at 275.15 K/277.15 K, 2.0 MPa, and 450 rpm. The findings unveiled that with an increase in salinity, the water recovery decreased showing the hindering effect of salts on mixed hydrate formation by reducing the solubility of mixed gas due to the strong electrostatic force of attraction between salt ions and water. A maximum of 67.3% water recovery was observed in 2.8 wt% produced water solution at 275.15 K, 2.0 MPa, and 450 rpm. Furthermore, the induction time increased by 52.64% in treating 2.8 wt% and a decrease in moles of gas consumed, water recovery, and water-to-hydrate conversion by 6.99%, 2.08%, and 9.69% compared to the deionized water system at 275.15 K. A removal efficiency of 47%-63% is achieved by using CO2 + C3H8 and the sequence of metal cation removal is in the order K+ > Na+ > Mg2+ > Ca2+ and anions SO42− > Cl− at 275.15 K. The results also showed that with a rise in the experimental temperature to 277.15 K the removal efficiency increased though the amount of hydrate formed is less. This study illustrates that the formation of mixed gas (CO2 + C3H8) hydrate can be used for treating produced water based on the water recovery, removal efficiency, electrical conductivity, and total dissolved solids results with lower energy consumption.

Pore size adjustment of sodium alginate-based composite aerogel spheres by zirconia for efficient selective removal of Cu(II)

In order to eliminate the great threat posed by Cu(II) in water to human health and ecosystem safety, graphene oxide-zirconium oxide/sodium alginate (GZS) aerogel spheres are prepared for adsorbing Cu(II) using the sol-gel method and freeze-drying technique in this paper. The adsorbent is preferentially selective for Cu(II) even in the presence of competing cations. This is due to the slit-shaped structure of the aerogel spheres which has strong affinity for planar Cu(II), deriving from the GO nanosheets stacking effect as well as crosslinking with SA,. The adsorption kinetics and isothermal experiments show that the adsorption process of GZS is multi-molecular layer adsorption with a maximum adsorption capacity of 132.57 mg/g, exhibiting a better capacity than previous similar adsorption materials. FT-IR and XPS mechanistic analysis indicate that the good adsorption performance of GZS on Cu(II) might be related to the synergistic effect of strong electrostatic force, ion exchange and complexation. The adsorption order of GO, ZrO2 and SA on Cu(II) is also investigated by density functional theory (DFT). In conclusion, GZS has the potential to selectively remove Cu(II) from water bodies.

Enhanced purification of kitchen-oil wastewater driven synergistically by surface microelectric fields and microorganisms

The stable structure and toxic effect of refractory organic pollutants in wastewater lead to the problem of high energy consumption in water treatment technology. Herein, we propose a synergistic purification of refractory wastewater driven by microorganisms and surface microelectric fields (SMEF) over a dual-reaction-center (DRC) catalyst HCLL-S8-M prepared by an in situ growth method of carbon nitride on the Cu-Al2O3 surface. Characterization techniques demonstrate the successful construction of SMEF with strong electrostatic force over HCLL-S8-M based on cation-π interactions between metal copper ions and carbon nitride rings. With the catalyst as the core filler, an innovative fixed bed bioreactor is constructed to purify the actual kitchen-oil wastewater. The removal efficiency of the wastewater even with a very low biodegradability (BOD5/COD = 0.33) can reach 60% after passing through this bioreactor. An innovative reaction mechanism is revealed for the first time that under the condition of a small amount of biodegradable organic matter, the SMEF induces the enrichment of electric active microorganisms (Desulfobulbus and Geobacter) in the wastewater, accelerates the interspecies electron transfer of intertrophic metabolism with the biodegradable bacteria through the extracellular electron transfer mechanism such as cytochrome C and self-secreted electron shuttle. The electrons of the refractory organic pollutants adsorbed on the surface of the catalyst are delocalized by the SMEF, which can be directly utilized by microorganisms through EPS conduction. The SMEF generated by electron polarization can maximize the utilization of pollutants and microorganisms in wastewater and further enhance degradation without adding any external energy, which is of great significance to the development of water self-purification technology.