Pure Water Research Articles

Study on PPTA/PEMs/PA composite NF membranes for highly efficient desalination of high-saline Kevlar® brine and long-term anti-scaling performance

It produces a large number of organic brine during the polymerization process of Kevlar®, which contains N-(1-Methyl-2-pyrrolidinone) (NMP) and high concentrations of CaCl2 and NaCl. The wastewater will cause serious pollution of water and soil resources if discharged directly. The separation and recycling of inorganic salts have been an industrial difficulty. In this paper, based on the novel concept of green self-recycling, we used Poly (p-phenylene terephthamide) (PPTA, resin of Kevlar®) ultrafiltration membrane as the substrate, composited the loose and curled polyelectrolyte multilayers (PEMs) as interlayers and formed a homogeneous polyamide separation layer through interfacial polymerization, from which we obtained the homogeneous reinforcement aramid composite nanofiltration (NF) membrane. The composite NF membranes with different interlayer numbers showed different advantages. For single-component brine, the retentions of PEMs-1/PA membrane were 93 % and 98.4 % for 10 g/L CaCl2 and MgSO4 respectively. For mixed brine of 20 g/L CaCl2 and NaCl, the retentions of PEMs-3/PA membrane were 87.13 % and 1.05 % for CaCl2 and NaCl respectively with the separation factor as high as 82.95. In the test of long-term service stability, PEMs-3/PA maintained stable performance in 4 cycles total of 160 h. And the permeance could almost fully recover after pure water backwash of only 0.5 h. In addition, the structural stability and anti-scaling performance of the PEMs-3/PA membrane were further verified in high-temperature brine. Surprisingly, the obtained PPTA NF membrane in this work could effectively treat the high-saline brine in the Kevlar® polymerization process and would have more promising prospects in the treatment of industrial wastewater of brine.

An Endogenic Origin for Titan's Rampart Craters: Assessment of Explosion Mechanisms

AbstractRampart craters are a class of lakes or depressions in Titan's north polar region that have morphological attributes suggestive of an explosive origin. Two previous studies have proposed that rampart craters form via nitrogen or methane vapor explosions analogous to terrestrial maar explosions. We propose a new terrestrial analog for rampart craters: gas emission craters (GECs) found in permafrost zones. We evaluate the explosive origin of Titan's rampart craters by modeling the dispersal of material from an explosive vent. The dimensions of nine rampart craters with radar‐bright ramparts were used to model the explosion process. The model yields a range of explosion conditions (e.g., gas mass and reservoir depth) producing ejecta dispersal patterns matching the observed features. We find that gas masses of 1011–1014 kg are required to produce a rampart crater. We examine two explosion scenarios: (a) rapid, maar‐like vaporization and explosion of liquid nitrogen or methane, and (b) more gradual gas accumulation and explosion akin to a GEC driven by methane released from destabilizing clathrates. If Titan's crust is composed of pure water ice, the calculated gas pressures are consistent with a rapid, maar‐like explosion mechanism. If the subsurface is predominantly composed of organic materials or clathrate, either scenario may be plausible. Further research on the composition and tensile strength of Titan's subsurface are required to discriminate between hypotheses. Nevertheless, we conclude that explosive dispersal of ejecta from a vent can account for the morphologies of Titan's rampart craters and may contribute to atmospheric methane replenishment.

Preparation of zwitterionic polymer and its application for dual-functional inhibition in deepwater drilling

During deep-water drilling operations, due to the conditions with low temperature and high pressure in the wellbore, methane hydrate can be easily formed in the presence of methane and plug the wellbore. In addition, the deep-water sediments are dominated by clay-silty with weak cementation, so well instability may be occurred due to clay hydration. In order to inhibit hydrate formation and clay hydration in deepwater drilling, a zwitterionic polymer AADV was synthesized through quaternary copolymerization of AM/AMPS/DMDAAV/VAC. The hydrate inhibition performance of AADV was evaluated in a high-pressure reactor chamber, and the results showed that AADV can delay the hydrate formation time from 330 min in pure water to 2204 min, indicating an excellent inhibition effect of hydrate formation. Meanwhile, 1 % AADV can significantly reduce the linear swelling rate of the calcium-based bentonite to 3.69 % for 10 h and increase the rolling recovery rate to 94.7 %, suggesting an excellent inhibition effect on clay hydration. The mechanism of dual-functional inhibition of AADV was further analyzed. The zwitterionic group in AADV and the hydrophilic amide group can strongly adsorb the water molecules through a strong hydration effect and the hydrogen bonding effect, respectively, which contributes to destroy the water molecules cage structure, and thus to suppress the hydrate formation. Besides, AADV can effectively obstruct mass transfer of methane molecules by increasing the viscosity of the aqueous phase and absorbing on the hydrate surface, leading to hydrate formation inhibition. For the inhibition of clay hydration, the SEM and XRD results proved that AADC inhibits the clay hydration through the film-forming effect. In addition, the contact angle of Na-Bent/AADC composite reached to 55.68° when the polymer concentration increased to 2 %, suggesting that the hydrophobicity of Na-Bent surface can be enhanced after AADC treatment. AADV can wrap around clay particles and form hydrophobic film through adsorption and intercalation, preventing the intrusion of external fluids and inhibiting clay hydration.

Turing structured nanofiltration membrane fabricated by sulfonated cellulose nanocrystals mediated interfacial polymerization for enhanced permeability separation performance

Preparing Turing structure nanofiltration (NF) membrane is a representative strategy to obtain high permeability and selectivity. However, getting a tailored Turing structure by adjusting the interfacial polymerization (IP) process remains a significant challenge. Herein, sulfonated cellulose nanocrystals (S-CNC) with excellent hydrophilicity and negative surface charges were selected as aqueous phase additives to explore their influence on the morphology and composition of polyamide (PA) layer as well as its NF performance. It was found the surface morphology of the PA layer was effectively changed by adjusting the content of S-CNC in the aqueous phase. As the content of S-CNC increased, the Turing structure underwent a series of evolutions, from an “octopus leg structure” to a densely packed ridge-valley structure to a large ridge-valley structure filled with dense nodular particles. Finally, it changed back to the typical PA morphology of densely distributed nodular particles. By exploring the interaction between S-CNC and piperazine (PIP), it was demonstrated that the hydrogen bond and electrostatic interaction between S-CNC and PIP synergistically inhibited the diffusion of PIP, thus resulting in various Turing structures. Benefiting from the unique Turing structure, the prepared SCNF-10 NF membranes showed excellent permeability and separation properties with pure water permeability (PWP) of 16.9 LMH bar−1 and Na2SO4 rejection rate of 98.0 %. SCNF-10 NF membranes also exhibited good selectivity with a separation factor of 34.6 for mono-bivalent salts and long-term permeation stability. It is anticipated that this regulation strategy for various Turing structures preparation can provide a deeper understanding of the application of cellulose nanocrystals to NF membranes in the later stage, which will also promote the development of the high performance of NF membranes.

Stable random laser of perovskite quantum dots based on SiO2-QDs-SiO2 composite nanostructure

In recent years, metal halide perovskite has gradually become a hotspot in the field of optoelectronics. However, the inherent instability of CsPbX3 quantum dots (QDs) seriously affects the amplified spontaneous emission (ASE) or lasing performance. Herein, the highly stable CsPbBr3 random laser is realized in SiO2-QDs-SiO2 (SQS) composite nanostructure doped with Ag nanoislands. The strong scattering generated by SQS composite nanostructure and the localized surface plasmon resonance (LSPR) of metal silver nanoislands provide optical feedback for the formation of random laser. Then a coherent random laser with low threshold (∼2.2 mJ/cm2) is obtained. SiO2 microspheres anchor QDs to avoid photoinduced regeneration and fluorescence quenching caused by QDs clusters. The inner QDs of SQS are effectively protected from water erosion, thus resulting that the samples have higher water resistance. The luminescence intensity still maintains 70 % of the original intensity after 40 days with the addition of pure water. Our research provides an effective method for improving the water stability of perovskite QDs. The highly stable random laser based on perovskite quantum dot film has a wide application prospect in integrated optoelectronics, display imaging and sensing measurement.

Modification of polysulfone membranes using magnetite nanoparticles containing sulfonic acid and heteropoly acid groups to improve permeability and antifouling properties

To increase the performance of ultrafiltration membranes, it is necessary to develop new materials. In this study, membrane production was carried out using magnetite nanoparticles functionalized by sulfonic acid and phosphotungstic acid (HPW) to increase permeability and improve antifouling properties. Firstly, Fe3O4@SiO2@NH2-SO3H (FSNS) and Fe3O4@SiO2@NH2-SO3H-HPW (FSNSPW) materials were synthesized. Then, different amounts of the nanoparticles were added to the membrane solutions. While the pure water flux was 164.2 LMH in the bare membranes, it was observed as 202.8 LMH and 195 LMH as a result of adding 0.5 % FSNSPW and FSNS. While Pb removal efficiency was 90 % in the bare membrane, it was measured as 97 % for 0.1 % FSNSPW and 89.6 % for 0.5 % FSNS. Maximum flux recovery ratio is 65.3 % for 0.5 % FSNSPW and 63.4 % for 1 % FSNS. Additionally, the highest Reactive Red 120 dye permeation flux was 72.2 LMH for 0.1 % FSNSPW and 71.9 LMH for 0.1 % FSNS membrane. Additionally, the highest permeation flux of Reactive Black 5 dye solution is 83.3 LMH for 0.5 % FSNSPW and 95 LMH for 0.5 % FSNS membrane. It could be concluded that the presence of the HPW group can improve the performance of the membranes.

Enhance Oil Recovery by Carbonized Water Flooding in Tight Oil Reservoirs

The low permeability of tight sandstone reservoirs limits the application of water flooding to enhance oil recovery. Due to the properties of CO2, people improve crude oil recovery by carbonizing water flooding. However, many studies have not prioritized determining the concentration of carbonated water before comparing the recovery rates of carbonated water flooding and pure water flooding after water flooding. This article takes the Chang 6 oil reservoir as the research object, and uses a combination of nuclear magnetic resonance testing and displacement experiments to conduct experiments on optimizing the concentration of carbonated water. Based on this, experiments on water flooding and carbon water flooding after water flooding to improve crude oil recovery are conducted to compare and analyze the oil enhancement potential of carbonated water flooding. The experimental results show that the physical properties, pore throat structure and seepage capacity of sandstone samples of type I, II and III decrease in turn. With the increase of carbonated water concentration, the expansion coefficient, viscosity reduction rate, contact angle reduction rate and core permeability loss rate of crude oil increase. The damage rate of 0.4mmol/cm3 carbonated water solution (17.6g CO2: 1L water) to the core permeability is only 0.98%, which is the optimal experimental concentration. During the water flooding process, crude oil in pores of different scales in Type I rock cores is utilized, and the degree of utilization in large pores is relatively high. Continuing to use carbonated water to drive oil in the rock cores after water flooding increased the recovery rate of crude oil by 15.24%; The degree of crude oil utilization in small pores of Tpye II core after carbonization and water flooding increased by 29.4%, and the final recovery rate of crude oil increased by 11.35% compared to the core after water flooding; The physical properties of Tpye III core are poor, with a small proportion of large pores, resulting in a 9.04% increase in crude oil recovery rate. Compared with pure water flooding, the recovery rate and utilization degree of large and small pores in the three types of rock cores after carbonization water flooding have been improved to varying degrees. Among them, the utilization degree of crude oil in large pores is the most significant, which increases the recovery rate of crude oil in the rock core after displacement. This study can provide a theoretical basis for improving crude oil recovery by carbonizing water flooding.

Insights into freeze-cast hierarchical water–glass foams via in situ time-lapse phase-contrast enhanced microcomputed tomography: Correlating composition, microstructure, and compression failure

We demonstrate how continuous freeze-casting without post-treatment sintering may be successfully employed using a pure water–glass (WG) solution to fabricate hierarchically porous foams lacking a morphology gradient along the freeze direction. By adjusting the water content (dilution) and/or the alkali ratio of the solution, we achieved lamellar structures with sub-features or cellular structures, with porosities spanning ∼65% to 83%. The WG foams exhibit astounding mechanical properties; notably, foams with a relatively low density of ∼0.33 g/cm3 demonstrated the highest compressive strength (5 MPa), due to their microstructure and pore morphology. In situ uniaxial compression tests combined with phase-contrast enhanced micro-computed tomography in a synchrotron revealed bending, buckling, fracture and splitting of the lamellar structures as main failure mechanisms. Our newly developed approach of continuous freeze-casting of pure WG solutions with an improved understanding of the relationship between composition, structure, and failure mechanisms provide a basis for a customized design and manufacture of a wide range of freeze-cast WG-based materials for applications ranging from biomedicine to energy generation and storage.

Numerical study on the thermal performance of space radiator using microencapsulated phase change material slurry as working medium

Microencapsulated phase change material slurry (MPCMS) has good prospects in the field of heat transfer because of its high latent heat and stability. In this research, MPCMS is applied to a space radiator to increase its heat load and temperature stability. The thermal performance of the space radiator is numerically studied by using the two-phase Eulerian (TPE) model and a multi-scale coupling model. The effects of velocity, volume fraction, microcapsule size, and microcapsule size distribution on the thermal performance of the space radiator are studied. Results show that the temperature flat area in the tube increases with the increase in the volume fraction or flow rate of the particle phase in the MPCMS, which means the heat dissipation capacity of the space radiator is also enhanced, and the maximum increase is 14 %. Compared with the use of pure water, the temperature difference between the highest and the lowest temperature of the radiator surface can be reduced by 40 %, and the heat dissipation power can be increased by 5 %. In addition, the large size of microcapsules limits the heat transfer between the two phases, especially when the size is greater than 50 μm. Compared with uniform microcapsule size distribution, the effect of lognormal distribution of variance σ = 0.7 on heat transfer is less than 1 %.

Structure and properties of homogeneous toughened poly(vinyl alcohol) blended membrane and exploration of application in membrane separation

Polyvinyl alcohol (PVA) has excellent physical and chemical properties; however, its rigidity easily leads to brittleness and breakage during use. Additionally, due to intramolecular hydrogen bonding, the dense structure of the film limits its application. This research used a self-toughening approach by homogeneously blending PVA 0588 and PVA 0499 with different molecular weights to enhance the toughness of PVA and create a porous structure for broader application in membrane separation. Porous PVA membranes were then produced through mechanical stretching. Rheological testing, differential scanning calorimetry, and dynamic thermomechanical analysis confirmed that the blend system is partially compatible. Mechanical characterization revealed that adding PVA 0499 decreased the tensile modulus, strength, and bending modulus of the blended film but increased the elongation at break, reaching a maximum of 179 %. This result indicates that homogeneous blending effectively achieved PVA self-toughening. After this, the PVA blended membrane underwent mechanical stretching. Results showed that the stretched membrane developed a porous structure with a PVA 0588 content of 60 wt%, yielding a pure water flux of 70.3 L m−2 h−1 MPa−1 and a glucan rejection rate of 91.07 %. The molecular weight cut-off test demonstrated that the resulting porous membrane was suitable for water treatment, effectively filtering substances with a molecular weight of ≥70 kDa. The membrane also exhibited notable antifouling properties. The hydrophilicity and high roughness of the porous membrane facilitated the formation of additional hydrogen bonds between the membrane surface and water molecules, thereby reducing direct contact between pollutants and the membrane surface. This study provides preliminary theoretical and experimental insights into enhancing PVA toughness and expanding its applications in membrane separation. Furthermore, homogeneous blending opens new avenues for improving the mechanical performance of polymers.

Highly efficient adsorption and removal of phthalate esters by polymers of intrinsic microporosity

In recent years, phthalate esters (PAEs) have been found to be endocrine disruptors that pose a serious safety threat to human health. Currently, adsorption is one of the most efficient technologies to remove PAEs, and the development of adsorbent materials that combine high adsorption capacity and short equilibrium time is a challenging problem. In this study, PIM-1, a typical representative of polymers of intrinsic microporosity (PIMs), was prepared through three methods and first used as adsorbents for PAEs removal. PIM-1 prepared under high temperature (HT-PIM-1) exhibited a high capacity of 787mg/g for dibutyl phthalate (DBP), a prevalent PAE in water, which is significantly higher than most reported adsorbents. Furthermore, more than 90.0% of the equilibrium adsorption capacity can be reached within 30mins. In addition, the adsorption of DBP could be inhibited by ethanol due to the enhanced interaction between DBP and ethanol, which could be revealed by molecular simulation. The adsorption mechanism of PAEs on PIM-1 mainly included hydrophobic interactions, π-π interactions, together with the size matching between PAEs and hierarchical pores of PIM-1. This study provides an idea for the application of PIMs for PAEs removal with high adsorption capacity and high efficiency. Environmental ImplicationPhthalate esters (PAEs) are emerging pollutants that pose a significant threat to public health and safety. They have been detected not only in environmental water but also in alcoholic beverages. Adsorption is widely preferred for removing PAEs, and the adsorption of PAEs in alcoholic solutions is a more challenging process compared to pure water. In this study, PIM-1 with o-phenyl groups similar to PAEs were first used as adsorbents for PAEs and demonstrated a remarkable adsorption capacity in both water (787mg/g) and alcoholic solutions (398mg/g) within a short period, surpassing the performance of commercial adsorbents.

Tailoring the PVDF membrane surface with polyoxypropylene-polyoxyethylene brush via in-situ grafting for enhanced oil/water emulsion separation

Membrane technology has been widely applied in oil-water separation owing to low energy consumption and high separation efficiency, but membrane fouling is a fatal factor affecting membrane performance and service life. Inspired by polyether nonionic detergents, a liquid surfactant polymer with polyoxypropylene-polyoxyethylene (PPO-PEO) segments was tailored to the surface of polyvinylidene fluoride (PVDF) membrane via in-situ grafting to improve its antifouling and oil-water separation properties. Firstly, in order to activate the inert surface of the PVDF membrane, poly(styrene-co-maleic anhydride) (SMA) was blended with PVDF to prepare the MA@PVDF as membrane substrate. Then, PPO-PEO brushes were grafted onto the surface of the substrate by an alcoholysis reaction to fabricate the PPO-PEO@PVDF membrane. The chemical structure and the surface morphology of the PPO-PEO tailored PVDF membrane surface were characterized, and the separation performance for oil/water emulsion was explored. The results show that the optimized grafting amount of PPO-PEO on the PVDF membrane is up to 476.2±3.0mg·g-1, and the pure water flux of the corresponding PPO-PEO@PVDF membrane is 191.3±4.0L·m-2·h-1, which is more than 20 times higher than that of the control PVDF membrane (around 7L·m-2·h-1). The water wetted PPO-PEO brushes on the surface of the PVDF membrane can hinder the adhesion of oily substances, and the separation efficiency of the PPO-PEO@PVDF membrane for kerosene/water emulsion reaches 91.7±0.6%, which is much higher than that of the MA@PVDF membrane without PPO-PEO brushes. The PPO-PEO tailored PVDF membrane provides useful strategies for the surface modification of membranes with enhanced performances of antifouling and oil-water separation.

Unlocking desalination’s potential: Harnessing MXene composite for sustainable desalination

Amidst freshwater scarcity, desalination is an effective solution, elevating pure water to a paramount commodity. Researchers actively pursue cost-effective alternatives to traditional desalination methods, with solar steam-based technologies now-a-days. Herein we report the synthesis of hierarchical photothermal absorber consisting of Ti3C2Tx decorated polypropylene fiber (PPF) composite and further used for solar desalination applications. Ensuring system stability amidst temperature fluctuations, pH variations, and mechanical stresses is pivotal for optimal desalination and wastewater treatment performance. Seamless integration of components is imperative to achieve this. Structurally, the Ti3C2Tx MXene@PPF composite evaporator showcases impressive metrics, such as high evaporation rate of 4.63 kg m-2h−1 along with a remarkable solar-evaporation efficiency of 93.48 % when tested under 1 sun illumination. Moreover, the composite absorber exhibits good mechanical stability, exceptional chemical stability even under harsh conditions (such as acid and alkali environments), outstanding salt tolerance and maintained a consistent evaporation rate over extended durations. Also, the absorber achieves good mechanical properties. These findings underscore the Ti3C2Tx MXene@PPF composite evaporator’s potential as a groundbreaking material for solar steam generation, offering high efficiency and cost-effectiveness. Beyond saline water desalination, its salt-preserving attributes and filtration capabilities position it as a promising alternative for wastewater treatment. This study presents an innovative and scalable solar water purification system applicable to a diverse range of water contaminants and manufacture in a cost-effective way.

ZrO2 Nanoparticles Filler-Based Mixed Matrix Polyethersulfone/Cellulose Acetate Microfiltration Membrane for Oily Wastewater Separation

Membrane technology has emerged as a dynamic field of study in academia and industry for treating produced oily wastewater. ZrO2 nanoparticles (ZrO2 NPs) filler-based mixed matrix polyethersulfone/cellulose acetate microfiltration membranes were fabricated and inspected in the oily wastewater remediation. The fabricated bare PES membrane, PES/CA blended polymers membrane, and PES/CA blended polymers incorporating ZrO2 NPs (ZrO2@PES/CA) membranes by phase inversion technique were inspected by field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, and measurement of water contact angle and porosity. The ZrO2@PES/CA membrane which consisted of 0.5 wt.% ZrO2 NPs (0.5%ZrPC) afforded increased hydrophilicity and reduced water contact angle from 70° for P membrane to 30.23°. Also, the 0.5%ZrPC membrane gave pure water flux of 88.89 L/m2.h, high oil rejection of 98.2% and showed remarkable antifouling capacity with a high flux recovery ratio of 89.3% and relative flux reduction of 34.3%. The effect of transmembrane pressure (1, 2, 3, and 4 bar), feed temperature (25, 40, and 50 °C), and an initial oil concentration (250, 500, 750, and 1000 mg/L) on the permeation flux and oil rejection of the 0.5%ZrPC membrane was investigated. The results revealed that ZrO2@PES/CA membranes have a significant potential for effective oil removal with high permeability and antifouling ability. The 0.5%ZrPC membrane confirmed its durability and reusability when kept an acceptable oil removal after 5 cycles.

The molecular picture of the local environment in a stable model coacervate.

Complex coacervates play essential roles in various biological processes and applications. Although substantial progress has been made in understanding the molecular interactions driving complex coacervation, the mechanisms stabilizing coacervates against coalescence remain experimentally challenging and not fully elucidated. We recently showed that polydiallyldimethylammonium chloride (PDDA) and adenosine triphosphate (ATP) coacervates stabilize upon their transferto deionized (DI) water. Here, we perform molecular dynamics simulations of PDDA-ATP coacervates in supernatant and DI water, to understand the ion dynamics and structure within stable coacervates. We found that transferring the coacervates to DI water results in an immediate ejection of a significant fraction of small ions (Na+ and Cl-) from the surface of the coacervates to DI water. We also observed a notable reduction in the mobility of thesecounterions incoacervates whenin DI water, both in the cluster-forming and slab simulations, together with a lowered displacement of PDDA and ATP. These results suggest that the initial ejection of the ions from the coacervates in DI water may induce an interfacial skin layer formation, inhibiting further mobility of ionsin the skin layer.

Experimental Study on the Effect of Skin Friction Drag and Convective Heat Transfer for Viscoelastic and Pseudoplastic Fluid Flow

Drag Reducing Agents (DRAs) have a huge impact and major concern in engineering and industrial applications. It makes the fluid flow turbulent to laminar, dampens eddy reduces head loss by up to a certain limit, and saves pumping energy costs. Viscosity is the property that dampens eddy due to the viscous effect, which increases the fluidity up to a certain limit. Pseudoplasticity is the shear thinning effect that decreases viscosity when the flow rate increases. So, for the viscoelastic effect, we can increase the concentration up to a certain limit to reduce head loss. Still, during flow due to the pseudoplastic effect, the viscosity will start decreasing which is a negative effect. So, these combined effects are studied to reduce skin friction drag in the pipeline and save energy costs which will be convenient for the food industry, chemical, and medicine industries. In this investigation, investigation is carried out for 0.3 g/L, 0.2 g/L, and 0.15 g/L of xanthan gum in turbulent flow to observe the pressure drop and heat transfer rate. The study reveals that after increasing viscosity the pressure drop reduced significantly. Conversely, the heat transfer rate was also reduced due to the poor mixing effect. A higher performance and less vibration of the pump was also observed. It was concluded that the frictional pressure drop was reduced up to 85 % and the heat transfer rate was reduced by up to 90% by increasing the concentration of the DRA up to 0.3 g/L at 10 LPM than the pure water or base fluid as a working substance on the double pipe heat exchanger. As the heat transfer rate reduced up to 90% with reducing pressure drop another aim of the study was to establish a concentration and flowrate for which the heat transfer rate is maximum and it was found at a concentration of 0.15 g/L of DRAs (drag reducing agents) at 22 LPM (maximum flowrate at this setup).

Self-healing Hydrophobic Antifouling Polymers with Fe3+-Catechol Coordination Interaction.

Hydrophobic antifouling polymers capable of self-healing performance are highly desirable for industrial applications. However, the construction of self-healing, hydrophobic antifouling polymers is challenging considering their complex fouling environments, which are humid in aqueous environment. In this work, a self-healing hydrophobic polymer containing Fe3+-catechol coordination applicable to antifouling is synthesized. The hydrophobic fluoroalkyl segments in the polymers formed unique domains dispersed in a polydimethylsiloxane matrix. The as-synthesized polymers can completely restore their tensile strength, and their self-healing efficiency is above 90% in both artificial seawater and pure water because of the dynamic Fe3+-catechol coordination interactions. The as-synthesized polymer exhibited self-healing and antifouling properties against common marine bacteria. The colony adhesion and self-healing processes of the damaged coating in artificial seawater containing marine bacteria are characterized by laser confocal microscopy. This strategy may be useful for the development of future polymeric antifouling materials.

Spirodiclofen toxicity in Tetranychus urticae and safety to natural enemies Proprioseiopsis asetus and Amblyseius swirskii

Proprioseiopsis asetus and Amblyseius swirskii are excellent natural enemies of plant-feeding mites and small pests. In order to clarify the safety of the acaricide spirodiclofen to the predatory mites P. asetus and A. swirskii, here, we investigated the toxicity of the acaricide on the pest mite T. urticae (nymphs and adult females) and on both species of predatory mites, P. asetus and A. swiskii (eggs, nymphs, and female adults) by using the spray, slide-dip, and leaf residual toxicity methods, compared the selective toxicity and assessed the safety to these natural enemies. The results demonstrated that the corrected mortality in P. asetus and A. swirskii female adults was <5% at recommended spirodiclofen concentrations in the spray method. In the leaf residual toxicity method, P. asetus and A. swirskii egg-hatching rates did not differ significantly from the pure water control group. In the slide-dip method, spirodiclofen lethal concentration 50 (LC50) in P. asetus and A. swirskii female adults was noted to be 9,494.875 and 3,064.187 mg·L−1, respectively. In the spray method, spirodiclofen LC50 in P. asetus and A. swirskii nymphs was found to be 4,292.664 and 1,081.609 mg·L−1, respectively, and that in T. urticae female adults and nymphs was 55.189 and 40.862 mg·L−1, respectively. Spiroclofen selective toxicity ratios (STRs) in P. asetus female adults–T. urticae and P. asetus nymphs–T. urticae were 172.013 and 105.053, respectively, indicating that spiroclofen has a high positive selectivity toward the pest T. urticae and its natural enemy P. asetus. In contrast, spiroclofen STRs in A. swirskiis female adults–T. urticae and A. swirskiis nymphs–T. urticae were 55.522 and 26.470, respectively, indicating spiroclofen has a moderate positive selectivity toward the pest T. urticae and its natural enemy A. swirskii. In the safety evaluation, the spirodiclofen safety factor for P. asetus female adults and nymphs was 158.248–237.37 and 71.544–107.317, respectively, whereas that for A. swirskii female adults and nymphs was 50.070–76.605 and 18.027–27.040 respectively. All spirodiclofen safety factor values were much higher than 5, indicating that spirodiclofen is highly safe for P. asetus and A. swirskii; in particular, spirodiclofen is safer for P. asetus than for A. swirskii.

From single tube to multi-channel configuration: Constructing nanofiltration membranes with superior adhesion strength on the ceramic support by interfacial polymerization

Ceramic membranes with multi-channel configurations exhibit superior mechanical strength, high packing density, and high separation efficiency, making them more suitable for industrial applications than single tube and hollow fiber membranes. However, the preparation of thin-film composite (TFC) membranes on multi-channel ceramic supports remains a challenge because of the poor compatibility between organic and inorganic materials and their special configuration. In this study, nanofiltration membranes with a stabilized structure supported by 19-channel ceramic membranes were successfully prepared with improved adhesion strength and dynamic interfacial polymerization. TFC membranes with different channels exhibited uniform microstructure and stable performance. Specifically, polyethyleneimine, which served as a polymerization reactant, can be tightly wound on the surface of ceramic membranes via hydrogen bonding and van der Waals forces during interfacial polymerization. Owing to the enhanced cross-linked network interactions between the support and separation layers, the adhesion strength was significantly improved. Consequently, the optimized membranes maintained excellent rejection to MgCl2 of ∼94 % after the back-flush test under the pressure of 4 bar. Additionally, the multi-channel TFC membranes exhibited stable performance, with a pure water permeance of ∼14.9 LMH/bar and a molecular weight cut-off of 450 Da. When filtering sunset yellow for 10 h, the prepared membranes exhibited stable permeance and excellent rejection performance.

Boosted photocatalytic H2O2 production in pure water with amino-modified N, S-doped carbon dots

A simple hydrothermal method was adopted to modify N, S-doped carbon dots (N, S-CDs) with feathers as precursors and ammonia by amino modification. The as-prepared am-N, S-CDs in amino as in alkaline environments possessed shorter S-N bonds (S2-), which kinetically and effectively increased the rate of electron conduction and reduced the binding of electron-hole pairs. In addition, the amino modification in am-N, S-CDs effectively improved the O2 adsorption capacity, photocatalytic activity and cycling capacity of the catalysts, with the H2O2 yield (384.86 μM) being 3.73 times higher than that of the pristine N, S-CDs (103.12 μM). This study suggests a rational design strategy for chemical bonding to regulate the surface charge transfer of photocatalysts for photochemical-to-chemical energy conversion.