Strong Water Repellency Research Articles

Engineering morphological architecture of superhydrophobic/hydrophilic composite membrane for efficient photothermal membrane distillation

The viability and efficacy of photothermal membrane distillation (PMD) is still uncertain due to its inherent energy-efficiency and throughput mass flux limitation. Herein, we develop a delamination-free multilayer photothermal membrane that simultaneously imparts slashed mass transfer resistance, enhanced photothermal effect and strong water-repellency by engineering morphological architecture. Using a one-step programmed dual-channel electrospinning followed by an electrostatic spraying technique, the proposed membrane is composited by a thick water-intrudable hydrophilic supporting layer, a thin hydrophobic layer, and an ultrathin Ti3C2Tx MXene-engineered superhydrophobic layer. It is proposed that the morphological architecture engineering could render mitigation of mass transfer resistance, firm water-repellency, and robust heat localization. Hence, in addition to superior flux of 1.27 L m−2 h−1 (inlet feed/permeate at 20/20 °C) and 15.89 L m−2 h−1 (inlet feed/permeate at 50/20 °C), prominent solar efficiency (76.34 % and 96.45 %) of the proposed composite membrane (DS15-M) also was achieved during PMD operation (1.0 kW m−2). Moreover, the DS15-M showcased not only robust wetting resistance and long-term consistency, but also obviously mitigated temperature polarization effect during the PMD operation. This research work emphasizes the important role of morphological architecture in rendering performance enhancement, which is a significant implication in engineering membrane architecture for PMD application.

Water-Borne Photo-Thermal Superhydrophobic Coating for Anti-Icing, Self-Cleaning and Oil–Water Separation

Superhydrophobic coatings with photo-thermal effects have advantages in anti-/de-icing and self-cleaning. Here, an eco-friendly and low-cost fabrication of superhydrophobic coating was proposed by spraying a water-borne suspension including carbon black and paraffin wax onto substrate-independent surfaces. The a water-borne suspension coated on stain steel plate showed a strong water-repellence, delaying the ice freezing time to 665 s, which is much higher than that of bare stain steel plate (210 s) under the same experimental condition. The ice-melting time was measured as 120 s under a solar irradiation of 0.1 W/cm2, while the control group had no sign of ice-melting during the same time. As a concept of proof, the self-cleaning, anti-corrosion, and oil–water separation were enabled by spraying the water-borne suspension on various substrates, demonstrating its diverse performances. Hence, the water-borne superhydrophibic coating provides an efficient, safe, and sustainable solution for wettability-related applications.

Bionic lotus‐leaf‐structured fluorine‐free polyurethane by combining electrospinning and electro‐spraying for waterproof and breathable textiles

AbstractDeveloping environmentally friendly and high‐performing viable waterproof and breathable membranes (WBMs) is critical but significantly challenging. Herein, we combine electrospinning and electro‐spraying methods. First, elastic thermoplastic polyurethane (TPU) is used as the polymer, and poly(methylhydrosiloxane) (PMHS) with low surface energy is introduced to prepare TPU/PMHS fiber‐based membranes by electrospinning. Electro‐spraying is performed using a dilute solution of TPU/PMHS/SiO2, with fluorine‐free hydrophobic SiO2 nanoparticles introduced to facilitate the construction of a rough lotus‐leaf‐like surface structure, ultimately obtaining TPU/PMHS/SiO2 WBMs with bead‐on‐string fiber binary structures and a strong water repellency. The results indicate that the TPU/PMHS/SiO2 WBMs comprise a three‐dimensional porous structure formed by randomly arranged fibers and a lotus biomimetic structure consisting of bead‐like fibers, providing the membrane with excellent mechanical properties and waterproof breathability, including a tensile strength of 15.8 MPa, static water pressure of 33 kPa, water vapor transmission rate of 5169 g m−2 d−1, and contact angle of 142°. Additionally, the fiber membrane exhibits an excellent strain recovery after 1000 cycles of cyclic stretching under 100% strain, verifying the excellent elastic properties of the TPU/PMHS/SiO2 WBMs. This simple preparation process and unique composite structure can facilitate the design and preparation of environmentally friendly, waterproof, and breathable materials.

Combining Chitosan, Stearic Acid, and (Cu-, Zn-) MOFs to Prepare Robust Superhydrophobic Coatings with Biomedical Multifunctionalities.

There is an urgent need to develop a series of multifunctional materials with good biocompatibility, high mechanical strength, hemostatic properties, antiadhesion, and anti-infection for applications in wound care. However, successfully developing multifunctional materials is challenging. In this study, two superhydrophobic composite coatings with good biocompatibility, high mechanical strength, strong antifouling and blood repellency, fast hemostasis, and good antibacterial activity areprepared on cotton fabric surface by simple, green, and low-cost one-step dip-coating technology. The results discussed in the manuscript reveals that the two superhydrophobic composite coatings can maintain good mechanical stability, strong water repellency, and durability under various types of mechanical damage, high-temperature treatment, and long-term strong light irradiation. The coatings also exhibit good repellency to various solid pollutants, highly viscous liquid pollutants, and blood. In vitro and in vivo hemostatic experiments show that both composite coatings havegood hemostatic and anticlot adhesion properties. More importantly, this superhydrophobic coating prevents bacterial adhesion and growth and released Cu2+ and Zn2+ ions and chitosan to achieve bactericidal properties, thereby protecting injured skin from bacterial infection. The two superhydrophobic coatings enhance the antifouling, antiadhesion, hemostatic, and antibacterial functions of blood-repellent dressings and therefore have broad application prospects in medical and textile fields.

Temporal and spatial distribution of soil water repellency in grassland soils and its relation to soil moisture, hydrophobic matter, and particle size

In grassland soils, soil water repellency (SWR) may be one of the triggers of soil erosion and degradation as it can reduce water infiltration and penetration into the soil. Few studies were focusing on the evaluation of soil hydro-physical properties, such as hydrophobicity, and their relation to soil moisture, hydrophobic matter, and particle size in grassland soils. In this study, 800 soil samples were collected from the Xilingol grassland in Inner Mongolia, China, using the water droplet penetration time (WDPT) test to evaluate water repellency and we aimed to investigate the temporal and spatial distribution of SWR in grassland soils using the Kriging and Inverse Distance Weighting (IDW) interpolation methods and determine the physical-chemical properties that trigger the SWR. The results showed that the grassland soils in the studied area were slightly water-repellent and a few portions of the area exhibited strong water-repellency. In April, areas of soils with a depth of 0–5 cm and slight to strong SWR accounted for 80 % of the total studied area, of which 5 % had strong water repellency. Moreover, in August, 90 % of the studied area consisted of soils with slight to strong SWR, of which 60 % accounted for soils with strong SWR. With a soil water content of 10.95 %, the SWR reached its peak, with an average value of 60.32 s. The SWR was positively correlated with total N, available N, and soil organic matter (SOM) contents, and therein the hydrophobic acid matter and the hydrophobic basic matter content had a positive contribution to SWR, and the hydrophilic basic matter and the hydrophilic acidic matter had a negative contribution on SWR. In addition, SWR was found to be negatively related to the soil particle size (r = −0.672). A slight SWR was also observed in the majority of the studied area, particularly in the topsoil and fine soils, especially during the monsoon period; hence, SWR must be also considered to reduce the risk of occurrence of soil erosion and degradation in grasslands.

An eco-friendly and facile method to prepare waterborne polyurethane based fire-resistant & waterproof coatings for wood protection

The fire-resistant & waterproof coatings for wood protection are highly demanded to reduce fire risk and save lives because wooden furniture and in-house decorations are widely used in our daily life. Herein, an eco-friendly and facile method was proposed to prepare such coatings, where a waterborne polyurethane (WPU) with non-volatility was blended with commercial flame retardants. A coating of ∼250 μm could generate charcoal of ∼10 mm that the painted plywood could withstand burning for ∼20 min. For the purpose to turn the hydrophilic WPU into water-repellent coating, hydrophobic nano-SiO2 were sprayed onto the surface to assemble into hierarchical structure. Consequently, the coating showed strong water repellency and the water contact angle arose from ∼89° to ∼157°. This method is conducive to the industrial production of fire-resistant and waterproof coatings due to its green and easy-to-scale up features, which will benefit thousands of households.

Soil organic matter facilitates the transport of microplastic by reducing surface hydrophobicity

Groundwater contamination by microplastic (MP) causes increasing concern about the critical factors that determine MP transport mechanisms in the vadose zone. Strong water repellency of native microplastic surfaces and respective attractive hydrophobic interactions with components of the soil matrix limits its mobility. However, adsorption of dissolved organic matter (DOM) onto microplastic surfaces can potentially make them more hydrophilic, enhancing their mobility. Consequently, the main objective of this study was to systematically determine the effects of DOM on both the surface properties and the mobility of polystyrene microplastic (PSP), and to use the extended DLVO theory (XDLVO) to predict PSP transport behavior with natural DOM for the first time. Breakthrough experiments were conducted in columns filled with quartz sand, through which PSP (1 µm) were percolated at either 0 or 5 mg/L dissolved organic carbon (DOC) derived from beech (Fagus sylvatica) litter at ionic strengths ranging from 0.5 to 2.5 mM CaCl2, since the cation background also affects wettability and mobility. Using sessile drop contact angle and zeta potential measurements, XDLVO interaction energy components including Lewis acid-base energies were approximated. Breakthrough curve analysis confirmed that DOM coming from natural sources strongly enhanced the mobility of PSP in the quartz sand matrix, in particular at higher ionic strength. At 2.5 mM CaCl2, the presence of DOM increased PSP breakthrough from 1 % to 60 %. Consequently, in the absence of DOM, laser microscope images showed much more pronounced formation of microplastic clusters on quartz grain surfaces than at co-percolation of PSP with DOM. This behavior could be clearly predicted with the XLDVO approach, which suggests at 0 mg/L DOC a deep primary energy minimum between individual PSP and between PSP and quartz surfaces. In contrast, repulsive hydrophilic interactions between the surfaces were predicted at 5 mg/L DOC. We conclude that even low concentrations of DOM, as usually found in subsoil, can significantly enhance the mobility of microplastic in soils via rendering the surfaces more hydrophilic. This implies potentially serious repercussions for the spread of this contaminant in the environment.

Stable method for electrodepositing network-like magnesium hydroxide layer with superhydrophobicity and enhanced surface performance under structure direction of xanthan gum/glycerol

Investigation of magnesium hydroxide superhydrophobic layer would significantly improve the application of green and low-cost superhydrophobic materials, for the abundant source, low economic cost, nontoxicity and environment friendliness of magnesium hydroxide. In this work, an obviously developed method which is stable and easy for fabricating network-like magnesium hydroxide superhydrophobic layer on iron substrate has been rendered, simply by cathodic electrodeposition with magnesium nitrate aqueous solution under structure direction of glycerin cross-linked xanthan gum, and subsequent surface modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane. The preparation process could be carried out at tremendously wide range of bath temperature (from 15 °C to 75 °C), xanthan gum/glycerol dissolving temperature (from room temperature to 100 °C), and storage times (from 0 day to 30 days). The superhydrophobic layer obtained at 35 °C bath temperature with addition of xanthan gum/glycerol dissolved at room temperature and stored for 7 days, shows strong water repellency (160.1° water contact angle, 3.2° sliding angle), and excellent self-cleaning performance. The layer also demonstrates good mechanical property according to cross hatch adhesion and tape peeling test, and owns an inhibition current efficiency as high as 99.98%, taking advantage of its extremely high anti-corrosion resistance (Rct = 2.87 × 105 Ω cm−2, Rf = 1.49 × 109 Ω cm−2).

Robust superhydrophobic materials with outstanding durability fabricated by epoxy adhesive-assisted facile spray method

Superhydrophobic materials are promising next-generation waterproof materials due to their excellent self-cleaning, antifouling and additional capabilities. Herein, the superhydrophobic materials with excellent comprehensive performance were developed via a simple, low-cost, environmental, and scalable spray method with epoxy adhesive assistance. The epoxy adhesive enhanced the adhesion strength between spray coating and substrates significantly. Consequently, various properties of superhydrophobic coatings were improved greatly. The as-prepared superhydrophobic surfaces exhibited excellent mechanical durability. The water contact angle maintained unchanged basically and sliding angle only increased slightly even though sandpaper abrasion distance had extended to 2100 cm or tape-peeling test had reached 30 cycles. Moreover, the strong water repellence retained even after 72 h immersion in strong acid/alkali, 1 h treatment upon 280 °C, and 7 days exposure under 254 nm UV light. These indicated that the obtained superhydrophobic materials exhibited outstanding acid, alkali, high temperature, and UV light resistance and stability. Besides, the superhydrophobic materials demonstrated excellent self-cleaning and anti-icing performance. So the synthetic superhydrophobic materials were expected to have a wide range of applications in the industrial production and daily life. More importantly, they could be applied in a variety of harsh environments for long periods of time.

Highly Water-Repellent and Anti-Reflective Glass Based on a Hierarchical Nanoporous Layer

Optically anti-reflective and water-repellent glass is required for solar cell covers to improve power-generation efficiency due to transparency improvement and dirt removal. Research has been conducted in recent years on technologies that do not use fluorine materials. In this study, we focused on the anti-reflective properties and microstructure of hierarchical nanoporous layer (HNL) glass and used it as a substrate. As a result, we have achieved both strong anti-reflectivity and high water repellency on HNL glass by coating polydimethylsiloxane (PDMS) using baking and thermal chemical vapor deposition (CVD). The surfaces showed a significantly higher sliding velocity of water droplets than the PDMS-treated material on the flat glass plate. They also showed such water repellency that the droplets bounced off the surface.

Transforming Ti3C2Tx MXene's intrinsic hydrophilicity into superhydrophobicity for efficient photothermal membrane desalination.

Owing to its 100% theoretical salt rejection capability, membrane distillation (MD) has emerged as a promising seawater desalination approach to address freshwater scarcity. Ideal MD requires high vapor permeate flux established by cross-membrane temperature gradient (∆T) and excellent membrane durability. However, it’s difficult to maintain constant ∆T owing to inherent heat loss at feedwater side resulting from continuous water-to-vapor transition and prevent wetting transition-induced membrane fouling and scaling. Here, we develop a Ti3C2Tx MXene-engineered membrane that imparts efficient localized photothermal effect and strong water-repellency, achieving significant boost in freshwater production rate and stability. In addition to photothermal effect that circumvents heat loss, high electrically conductive Ti3C2Tx MXene also allows for self-assembly of uniform hierarchical polymeric nanospheres on its surface via electrostatic spraying, transforming intrinsic hydrophilicity into superhydrophobicity. This interfacial engineering renders energy-efficient and hypersaline-stable photothermal membrane distillation with a high water production rate under one sun irradiation.

Ultrafast water permeation through nanochannels with a densely fluorous interior surface.

Ultrafast water permeation in aquaporins is promoted by their hydrophobic interior surface. Polytetrafluoroethylene has a dense fluorine surface, leading to its strong water repellence. We report a series of fluorous oligoamide nanorings with interior diameters ranging from 0.9 to 1.9 nanometers. These nanorings undergo supramolecular polymerization in phospholipid bilayer membranes to form fluorous nanochannels, the interior walls of which are densely covered with fluorine atoms. The nanochannel with the smallest diameter exhibits a water permeation flux that is two orders of magnitude greater than those of aquaporins and carbon nanotubes. The proposed nanochannel exhibits negligible chloride ion (Cl-) permeability caused by a powerful electrostatic barrier provided by the electrostatically negative fluorous interior surface. Thus, this nanochannel is expected to show nearly perfect salt reflectance for desalination.

Antibacterial fabric with contradictory functions of water repellency and absorbency realized by electrophoretic deposition of hydrophobic SiO2 and hydrophilic ZnO nanoparticles

Clothing and fabrics used in household and industrial applications can cause human-to-human cross-infection by residual bacteria attached to their surfaces. In particular, for fabrics used in the medical and healthcare sectors, it is vital to use highly antibacterial fabrics to prevent secondary infections caused by body fluids. In this work, antibacterial fabrics with strong water repellency were developed by electrophoretic deposition (EPD) of zinc oxide (ZnO) and hydrophobic silicon dioxide (SiO2) nanoparticles. The top layer of hydrophobic SiO2 nanoparticles prevents direct adhesion of bacterial droplets, while the bottom layer of hydrophilic ZnO nanoparticles provides antibacterial properties against the residual bacteria on the fabric. As a result, the developed fabrics can simultaneously reduce droplet adhesion and bacteria viability, effectively lowering the risk of bacterial infection. The ability to express these opposing wettabilities can be achieved by our EPD process, which can deposit various nanoparticles in porous form using electric fields on a non-conductive substrate. We expect that the fabrics developed in this work can be applied to various fields that require both antibacterial and antiwetting properties.

Exchange Counterion in Polycationic Hydrogels: Tunability of Hydrophobicity, Water State, and Floating Capability for a Floating pH Device.

Smart gel materials are capable of controlling and switching swelling, water state, and wettability properties triggered by external stimuli. In this study, we fabricated a series of polyelectrolyte hydrogels bearing a 3-trimethylammoniumpropyl pendant to a methacrylamide-based backbone and examined the switchability with hydrophobic-like counteranions. The exchange between the initial chloride and camphor sulfate (CaS), dodecyl sulfate (DS), and perfluorooctanoate (PFO) counterions was investigated. The kinetics of the exchange showed that the fast exchange (within 4 h) of PFO allowed for a favorable coordination for ion pairing, resulting in a decrease in hydration. The reversibility of the exchange to the Cl− ion was only enabled for the CaS ion due to its bulkiness, while the PFO and DS hydrogels were unable to exchange, even by using tetrabutylammonium chloride, which is a structurally similar reagent, due to aggregation or the coagulates in the collapsed state of the linear tails of the counterions. The hydrogels exhibited a modulable water state and water swelling. Moreover, the hydrogels containing DS and PFO, as counterions, showed surface hydrophobic (contact angle 90°) and high hydrophobic (110°) behavior, respectively. The Raman spectrometry fluorescence with a pyrene probe indicated an increase in strong hydrogen-bonded water molecules, water confinement, and hydrophobic domains in the PFO hydrogel. Moreover, the PFO-modified hydrogel demonstrated a free-floating ability on the water surface, with a strong water repellency, showing that it has the potential to be applied in a floating pH detection device to distinguish between volatile and nonvolatile bases in a controlled manner.

Soil water repellency characteristic curve of Spolic Technosols from the region of Maritsa-Iztok coal mine in Bulgaria

Soil water repellency is phenomenon which is caused by compounds of organic origin, type of clay minerals and wetting/drying cycles. Hydrophobicity is usually characterized by a great spatial and temporal variability, especially in mine spoils where different types of overburden materials are mixed with coal particles and other waste products. The aim of this study was to investigate the changes of hydrophobicity with soil moisture content of Heavy Clay textured Spolic Technosols in the region of Maritsa-Iztok open cast coal mine. The sampling was done in a stubble field at 8 points from two soil depths 10–15 cm and 30–35 cm. The samples were analyzed for particle size distribution, total organic carbon content, soil bulk density, soil moisture content at field sampling, soil particle density, soil moisture content and water-drop-penetration-time (WDPT) at different matric potentials (SWRCC). The irregular presence of coal particles and different overburden sediments lead to spatial variability of studied properties, especially of total organic carbon content. In depth the average clay content, organic carbon content, water retention properties and soil water repellency (SWR) increased and correspondingly the density properties decreased. The distribution of SWR classes of the studied samples at the applied suctions during the drying process showed that the hydrophilicity of all samples at saturation persisted at suction pF 1.0 in 73% of the samples Most of the samples at suctions pF 1.7 and pF 2.0 were with slight and strong water repellency, but still there were hydrophilic samples 27% and 18%, correspondingly. At pF 2.5, which is often accepted as field capacity of fine textured soils, all samples were water repellent. The further drainage of the samples at pF >3.3 led to domination of extreme SWR and above pF3.7 all samples were extremely water repellent. Besides the unfavorable consequences of water repellency, the dry hydrophobic topsoil at the time of sampling formed a capillary barrier that reduced the evaporation and led to nearly 3 times higher water content stored in the subsoil.

Effect of Biomass-Burning Emissions on Soil Water Repellency: A Pilot Laboratory Study

While western U.S. wildfires have increased in intensity and scale, their impacts on soil chemical composition and hydraulic processes have received little attention, despite increasing erosion, surface runoff and flooding. The relationships between biomass-burning emissions, composition of the soil, fire heat, and soil water repellency are fragmental and sometimes contradictory. Here, we characterized the water repellency of sand (soil surrogate) exposed to Jeffrey pine duff smoke under controlled laboratory conditions. Water drop penetration time (WDPT), effective contact angle, and relative sorptivity of exposed silica sand (soil surrogate) were determined. Sand samples treated with smoke and heat or with cold smoke showed severe-to-extreme water repellency (WDPT > 1020 s). Sand samples exposed to fulvic acid (surrogate for soil organic matter) showed strong water repellency (WDPT = 81 s) that increased to become severe (WDPT = 2305 s) after subsequent heating to 200 °C for two hours. All sand samples exposed to either fire emissions or fulvic acid showed WDPTs >81 s, effective contact angles between 78° and 87°, and relative sorptivities between 0.31 and 0.49 compared with the untreated sand samples, with a WDPT <0.5 s, effective contact angle of 48°, and relative sorptivity of 1. This indicates that the sorptivity-controlled water infiltration into treated sand is less than half of that into untreated sand.

Efficient Fabrication of Wear-Resistant PEEK Matrix Composite Coating with Superhydrophobicity for Self-Cleaning and Anti-Icing Applications

ABSTRACT For the potential application of superhydrophobic surface to anti-icing of Unmanned Aerial Vehicle(UAV) metal wing,a gradient composite coating was successfully prepared on the common aviation metal 7075Al alloy substrate by electrostatic spraying, with Polytetrafluoroethylene(PEEK) and Polytetrafluoroethylene(PTFE) as raw materials for physical blending. The composite structure was constructed by doping the modified hydrophobic silica(k-SiO2) particles. The wettability, microtopography and chemical components of coating were characterized by contact angle tester, SEM and FT-IR respectively. Results showed that the Water Contact Angle(WCA) of PEEK-PEEK/PTFE composite coating increased with PTFE content increase, and the maximum WCA could reach 149.6°, PTFE and PEEK were cross-linked to form nanofibers closely arranged on the surface. However, when k-SiO2 particles was were added into it, the PEEK-PEEK/PTFE/k-SiO2 superhydrophobic coating that exhibits WCA of 156.4±1° and Water Contact Sliding(WSA) of 2±0.5° was obtained. Micro-nano multi-scale protrusion surrounded by low surface energy fibrous filamentous structure distributed on the surface, which can entrap air pockets, leading to extremely strong dynamic water repellency. Interestingly, it is found that droplets can bounce back quickly after hitting the surface with shorter solid-liquid contact time of 18.25ms. Moreover, the coating exhibits excellent mechanical wear resistance to withstand 51 abrasion cycles with good adhesion to substrate of grade 0, anti-fouling and anti-scaling abilities. Furthermore, compared with the bare 7075Al alloy surface, the prepared superhydrophobic coating has obvious icing characteristic for the reason of a solid-liquid-gas composite contact surface with droplets, making it an ideal anti-icing surface.

Toward Easily Enlarged Superhydrophobic Copper Surfaces with Enhanced Corrosion Resistance, Excellent Self-Cleaning and Anti-Icing Performance by a Facile Method.

This work reports a facile method for fabricating superhydrophobic surface on copper plate by AgNO₃ treatment and dodecyl mercaptan modification. The as-prepared superhydrophobic copper plate presents hierarchical and rough morphology composed of nanosheets and nanoparticleformed matrix. Meanwhile, long alkyl chains are assembled onto the rough surface successfully. Consequently, the copper plate is endowed with excellent superhydrophobic performance with a water contact angle of 156.8° and a rolling angle of ca. 3°. Moreover, the superhydrophobicity has long-term durability and excellent stability. Grounded on the strong water repellence, the resultant superhydrophobic copper plate surface exhibits multi-functions. The excellent performance can be well explained by "Cushion effect" and Capillary phenomena. As a result, water and corrosive species can be prevented from contacting with the copper plate surface, and contaminants can be taken away easily by the rolling water droplets. Meanwhile, the icing process of water is delayed on the superhydrophobic surface. Therefore, the superhydrophobic copper is endued with enhanced corrosion resistance, excellent self-cleaning and anti-icing performance. We believe that this facile method provides a simple and cost-effective process to improve the properties of copper plate, and which may see practical application of the superhydrophobic materials.

Long-Term Effectiveness of Tree Removal to Re-Establish Sagebrush Steppe Vegetation and Associated Spatial Patterns in Surface Conditions and Soil Hydrologic Properties

Pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland encroachment into sagebrush (Artemisia spp.) steppe communities throughout western North America has substantially altered the vegetation structure and hydrologic function of one of the most ecologically important rangeland ecosystems in the world. Various pinyon and juniper tree removal practices are employed to re-establish sagebrush steppe vegetation and an associated resource-conserving ecohydrologic function. The effectiveness of these practices is highly variable owing to the vast domain in which woodland encroachment occurs, climate fluctuations, differences in treatment applications, and myriads of pre-treatment conditions and post-treatment land uses. This study evaluated the long-term (13 years post-treatment) effectiveness of prescribed fire and mechanical tree removal to re-establish sagebrush steppe vegetation and associated spatial patterns in ground surface conditions and soil hydrologic properties of two woodland-encroached sites. Specifically, we assessed the effects of tree removal on: (1) vegetation and ground cover at the hillslope scale (990 m2 plots) and (2) associated spatial patterns in point-scale ground surface conditions and soil hydrologic properties along transects extending from tree bases and into the intercanopy areas between trees. Both sites were in mid to late stages of woodland encroachment with extensive bare conditions (~60–80% bare ground) throughout a degraded intercanopy area (~75% of the domain) surrounding tree islands (~25% of domain, subcanopy areas). All treatments effectively removed mature tree cover and increased hillslope vegetation. Enhanced herbaceous cover (4–15-fold increases) in burned areas reduced bare interspace (bare area between plants) by at least 4-fold and improved intercanopy hydraulic conductivity (> than 2-fold) and overall ecohydrologic function. Mechanical treatments retained or increased sagebrush and generally increased the intercanopy herbaceous vegetation. Intercanopy ground surface conditions and soil hydrologic properties in mechanical treatments were generally similar to those in burned areas but were also statistically similar to the same measures in untreated areas in most cases. This suggests that vegetation and ground surface conditions in mechanical treatments are trending toward a significantly improved hydrologic function over time. Treatments had limited impact on soil hydrologic properties within subcanopy areas; however, burning did reduce the soil water repellency strength and the occurrence of strong soil water repellency underneath trees by three- to four-fold. Overall, the treatments over a 13-year period enhanced the vegetation, ground surface conditions, and soil hydrologic properties that promote infiltration and limit runoff generation for intercanopy areas representing ~75% of the area at the sites. However, ecological tradeoffs in treatment alternatives were evident. The variations in woodland responses across sites, treatments, and measurement scales in this long-term study illustrate the complexity in predicting vegetation and hydrologic responses to tree removal on woodland-encroached sagebrush sites and underpin the need and value of multi-scale long-term studies.

Environmentally friendly superhydrophobic osmanthus flowers for oil spill cleanup

Herein, we found osmanthus flowers (osmamthus fragrans var. thunbergii) showing interesting wetting behaviors. Fresh flowers manifested high-adhesion hydrophobicity with the water contact angles (WCAs) of 128.6 ± 3.5°. Dry flowers exhibited low-adhesion superhydrophobicity (WCA = 158.3 ± 2.7°) and superoleophilicity with the oil contact angles (OCA) of 0°. When crushed osmanthus flowers into powders, strong water repellency and oil wetting were still found. Both of osmanthus flowers and powders displayed efficient oil absorption capacities (OACs), whereby osmathus powders showed high OACs for different organic solvents ranging 5.3 ± 2.2–27.3 ± 1.8 g/g. Moreover, flowers and powders samples were featured with the abilities of emulsion purification. Importantly, from experimental result analysis and theoretical derivations, we concluded that OACs were varied regardless of sample masses while increased almost linearly upon the product of densities and surface tensions (ρ × γ) of absorbed solvents. This research not only provides a new kind of low-cost, easy-to-access and environmentally friendly raw superwettable material applied for future oil cleanup but also will be advantageous for optimizing the selection of oil-absorbing materials for certain solvents.