Pre-wetting Process Research Articles

An Eco-Friendly Manner to Prepare Superwetting Melamine Sponges with Switchable Wettability for the Separation of Oil/Water Mixtures and Emulsions.

Oil/water separation processes have garnered significant global attention due to the quick growth in industrial development, recurring chemical leakages, and oil spills. Hence, there is a significant demand for the development of inexpensive superwetting materials in an eco-friendly manner to separate oil/water mixtures and emulsions. In this study, a superwetting melamine sponge (SMS) with switchable wettabilities was prepared by modifying melamine sponge (MS) with sodium dodecanoate. The as-prepared SMS exhibited superhydrophobicity, superoleophilicity, underwater superoleophobicity, and underoil superhydrophobicity. The SMS can be utilized in treating both light and heavy oil/water mixtures through the prewetting process. It demonstrated fast permeation fluxes (reaching 108,600 L m-2 h-1 for a light oil/water mixture and 147,700 L m-2 h-1 for a heavy oil/water mixture) and exhibited good separation efficiency (exceeding 99.56%). The compressed SMS was employed in separating surfactant-stabilized water-in-oil emulsions (SWOEs), as well as surfactant-stabilized oil-in-water emulsions (SOWEs), giving high permeation fluxes (reaching 7210 and 5054 L m-2 h-1, respectively). The oil purity for SWOEs' filtrates surpassed 99.98 wt% and the separation efficiencies of SOWEs exceeded 98.84%. Owing to their remarkable capability for separating oil/water mixtures and emulsions, eco-friendly fabrication method, and feasibility for large-scale production, our SMS has a promising potential for practical applications.

The Use of Pre-Wetting to Improve the Mechanical Behavior of Masonry Mortar Elaborated with Crushed Oyster Shell

In this research, the use of the pre-wetting technique is proposed as an ecological alternative to reduce water absorption in waste oyster shells used in the production of masonry mortar as a partial substitute for natural sand. An experimental study was conducted to assess the properties in both the fresh and hardened states of masonry mortars. Two mortar groups were prepared based on a control mixture, with natural aggregate replaced by crushed oyster shell (COS) in varying proportions. In one group, the COS was pre-wetted, while in the other group, the COS was used at its natural moisture content. The experimental results demonstrated that the pre-wetting process aided in reducing the water–cement ratio (w/c) in the mortar mixture, thereby improving its properties. In both mortar groups, favorable results were observed with respect to capillary water absorption. Although the compressive strength was affected by the incorporation of COS, pre-wetted mortars with substitutions of up to 30% achieved the reference value established in this research. The pre-wetting process proves to be a straightforward and cost-effective technique; it is environmentally friendly and will contribute to decreasing the accumulation of COS in landfills, thereby safeguarding natural material reserves.

High efficiency and selective separation of oily wastewater based on superamphiphilic biomass aerogel: Characteristics, mechanisms and application

The design and development of multifunctional materials to meet the sophisticated requirements of oily wastewater treatment is an urgent need and remains a great challenge. Herein, a superamphiphilic bio-aerogel (PTGA) with honeycomb-like porous structure was synthesized. The directional and reversible control of interfacial wettability can be achieved by simple pre-wetting process and solvent replacement method. Combined with the advantages of structure and wettability, PTGA was proved to be ideal for high-efficient oil-water mixture separation (J> 1500 L/m2·h, η > 99.8%), oils absorption (Cabs = 17–26 g/g) and dye selective removal (MO: 73.552 mg/g, MB: 45.876 mg/g). Furthermore, based on the newly developed dynamic separation device and excellent mechanical property of PTGA, enhanced separation of oil-water mixture (J = 3007 L/m2·h) and synergistic removal of co-existing pollutants (MB: 51.274 mg/g) were realized. Mechanism results indicated that the transition of interfacial wetting properties of PTGA was a multi-stage process, while oil/water separation and dye adsorption were two independent processes. Benefit from facile synthesis and unparalleled characteristics, the designed PTGA promise to be reliable and competitive candidates in wastewater remediation.

Facile construction of multifunctional bio-aerogel for efficient separation of surfactant-stabilized oil-in-water emulsions and co-existing organic pollutant

The deep treatment of robust oily emulsion wastewater has long been an arduous challenge. Herein, a biomass-derived PEI-TiO2@Gelatin aerogel (PEI-TiO2@GA) with honeycomb-like porous structure was fabricated. The interface wetting characteristics of PEI-TiO2@GA could be selectively switched between the superlipophilicity and superoleophobicity through the merely pre-wetting process. Combined with extraordinary structure and superwetting properties, PEI-TiO2@GA was proved to be ideal for oils absorption (17–26 g/g) and MO dye adsorption (73.549 mg/g) with high up-taking rate. Simultaneously, as-prepared PEI-TiO2@GA could realize various surfactant-stabilized oil-in-water emulsions separation simply under gravity with the separation efficiency as high as 99.25%. In addition, PEI-TiO2@GA was highly resistant toward mechanical compression (1.952 MPa), and exhibited acceptable regenerability within 5 cycles by performing solvent replacement approach. Combining with the newly developed separator and dynamic emulsion separation device, the continuous deep separation of the emulsion and the synergistic removal of co-existing pollutants can be achieved with the enhanced separation efficiency and permeation flux. Most importantly, the mechanism results show that the transition of interface wetting properties was a reversible multi-step process, and the demulsification separation of emulsion and the adsorption removal of co-existing pollutants were two independent processes. This work opens up a new avenue to customize advanced bio-aerogels for industrial effluent treatment and environmental remediation.

Multiphase media superwettability regulated by coexisting prewetting phase

Understanding the wetting behaviors of a given superwetting surface in multiphase media is important for elaborately tailoring superwettability. Here the surface chemistry of two types of superhydrophobic surfaces was programmed to reveal crucial effect of a coexisting prewetting phase rather than the prewetting process on their wetting states in water and oil–water separation application. After prewetting with ethanol to remove the air layer, underwater contact angles of superhydrophobic surfaces for oil droplet and bubble gradually decreased from over 150° along with the reduced surface energy. When the superhydrophobic surfaces were directly immersed in water or prewetted with oil, a stable air layer or infused oil as the prewetting phase enabled oil droplet and bubble to rapidly spread out. Moreover, air-prewetting superhydrophobic/underwater superoleophobic fabric can selectively adsorb oils from water, whereas it showed an excellent antifouling property without the air layer. For the separation of oil-in-water emulsions using superhydrophobic/underwater superoleophilic sponge, the stable air layer obstructed emulsions into three-dimensional porous structures. After removing the air layer, emulsion separation can be efficiently realized. This discovery provides a feasible approach for the regulation and development of unusual superwettability in multiphase media.

Effect of Pre-Wetting Recycled Mortar Aggregate on the Mechanical Properties of Masonry Mortar.

In this research we evaluated the use of recycled fine mortar aggregate (RFMA) as a fine aggregate for new masonry mortar creation. The pre-wetting effect on the aggregate before creating the mixture was analyzed as a method to reduce its absorption potential. A control mixture of conventional mortar and two groups of recycled mortars were designed with a partial replacement of natural sand by RFMA (pre-wetted and not pre-wetted) performed in different proportions. The results established that the pre-wetting process allows a reduction in the amount of water required during the creation of new mixtures, regulating the water/cement (W/C) ratio and improving the properties of recycled mortars such as air content, fresh and hardened densities, and compressive and adhesive strength for all substitution levels. Mortar made with a 20% substitution and pre-wetted until it was at 67% of its absorption capacity displayed adhesive values higher than the ones shown by the reference mortar. The pre-wetting process proves to be an easy performance technique; it is inexpensive, environmentally friendly, and the most valuable fact is that specialized equipment is not necessarily needed. This process is the most profitable option for improving RFMA exploitation and reuse.

Capillary Replacement in a Tube Prefilled with a Viscous Fluid.

Capillary invasion of a liquid into an empty tube, which is called capillary rise when the tube axis is in the vertical direction, is one of the fundamental phenomena representing capillary effects. Usually, the tube is filled with another pre-existing fluid, air, whose viscosity and inertia can be practically neglected. In this study, we considered the effect of the pre-existing fluid, when its viscosity is non-negligible, in a horizontal geometry. We observed the dynamics when a capillary tube that is submerged horizontally in a liquid gets in contact with a second liquid. An appropriate combination of liquids allowed us to observe that the second liquid replaces the first without any prewetting process, thanks to a careful cleaning of capillary tubes. As a result, we experimentally observed three distinct viscous dynamics: (i) the conventional slowing-down dynamics, (ii) an unusual accelerating dynamics, and (iii) another unusual dynamics, which is linear in time. We derived a simple unified expression describing the three distinct dynamics, which accounts well for the observations. We also demonstrated a thorough experimental confirmation on the initial velocity of the replacement and the replacement time, the time required for the invading fluid to completely replace the pre-existing fluid in the horizontal geometry.

High-strength corrosion resistant membranes for the separation of oil/water mixtures and immiscible oil mixtures based on PEEK

Nowadays, PEEK, as a kind of high performance polymer characterized with high strength, great corrosion resistance and thermal stability is regarded as a promising membrane material. In this study, PEEK fibers were prepared by melt spinning and then woven into textiles. Furthermore, interface reduction was utilized to give a more hydrophilic textile (PEEK-OH textile). In addition, considering to make full use of the huge membrane pores of the textile, a liquid-infused method was employed to regulate its surface energy and to establish an under-water oleophobic surface. Surprisingly, PEEK-OH textile functioned in not only oil/water separation, but also separating immiscible organic liquids with different polarities just through a liquid-infused approach. More importantly, we firstly introduced ‘mediator effect’ during the pre-wetting process before separation, taking ethanol as a ‘mediator’. Furthermore, according to the ‘mediator effect’, an under-oil hydrophobic membrane was established using dichloromethane as a ‘mediator’. As we expected, both PEEK and PEEK-OH textiles revealed features such as high flux, admirable selectivity, competitive strength, great corrosion resistance and thermal stability, herein, they promised to be used for oil/water separation in practical environment.

Quantitative Measurement of Water Absorption of Coarse Lightweight Aggregates in Freshly-Mixed Concrete

The high water-absorption of lightweight aggregate causes a high slump loss and poor workability of concrete. A prewetting process is usually recommended to compensate for the workability problem, but its application needs more delicate consideration in field. A method is proposed to measure the additional water absorption of lightweight aggregate, and its application in cement paste and concrete mixes confirms the absorption amount remaining unaffected by the mix proportion. The additional water absorption in cement-based materials can be considered as a material property, and its value is smaller than the water absorption measured by a standard test method (water-soaking). Compensating the additional water absorption finally allows to use dry lightweight aggregates for concrete, which is more robust and stabler than taking a saturated surface-dry lightweight aggregates.

Fabrication of pre-wetting induced superamphiphobic meshes for on-demand oil-water separation of light or heavy oil-water mixtures

In this study, a facile approach was proposed to fabricate superamphiphobic meshes for on-demand separating light or heavy oil and water mixtures after pre-wetting process. The micro-nano hierarchical structures on superamphiphobic stainless steel mesh were fabricated via vacuum thermal evaporation and chemical deposition. Low surface energy was acquired by modification with perfluorooctanoic acid. The effect of reaction time on wettability was investigated to obtain the optimal parameters of fabricating samples exhibiting superhydrophobicity and superoleophobicity simultaneously. The wettability of superamphiphobic meshes was controlled by the liquids of pre-wetting process. The superamphiphobic surfaces pre-treated with ethanol and water were used to separate the mixtures of light oil and water, while the meshes sequentially pre-soaked with ethanol and oil to separate the mixtures of heavy oil and water. The separation efficiency of up to 98 % was found even after multiple cycles. The fabricated superamphiphobic surfaces can avoid contamination and achieve on-demand oil-water separation without any external forces, which will have promising potential for application in oil-water separation.

Effects of pre-wetting time on surface topography and floatability of lignite particles

The laser particle size analyzer, NMR, SEM/EDS, induction time tests and surface roughness analysis were employed in the mechanism analysis of this investigation. The floatability of lignite was decreased with the pre-wetting increasing from 0 – 5min because the pores and fractures of lignite surface can be filled with water. However, the floatability of lignite was increased with the pre-wetting from 5 – 480min. NMR and SEM indicate that a long pre-wetting process (>5min) polished and rubbed the surface of lignite reducing the amount of macropores and fractures as well as the porosity. The rough lignite surface was also polished to be smooth. As the pre-wetting time increases, the topography of lignite surface, such as porosity, macropores, fractures and roughness decreased, which results in the decrease of water filling negative effects, and hence the floatability of lignite gradually increased with the pre-wetting time over 5min.

A New Prewetting Process of Through Silicon Vias (TSV) Electroplating for 3D Integration

Three-dimensional (3-D) integration based on the through silicon via (TSV) technology involves the processes of wafer thinning, TSV etching and plating, re-distribution layer (RDL) formulation, and FC chip bonding. TSV plating is a key to the 3-D electrical interconnection, whereas the prewetting process is one of the important factors that can decide the filling depth and quality of the TSV plating. In this paper, a new three-step prewetting process with high efficiency and low cost is developed and includes absolute ethanol infiltration, deionized water washing, and a copper electrolyte bath. In the electroplating process, blind vias with an aspect ratio of 10:1 prewetted by our three-step prewetting process were fully filled. [2018-0190]

Effect of UAV prewetting application during the flowering period of cotton on pesticide droplet deposition

Prewetting process can reduce the contact angle between the droplet and the leaf blade, so that the droplet can more easily wet and spread, thereby increasing the quantity of deposition. To improve the effectiveness of pesticides on cotton leaves, prewetting by single-rotor electric unmanned aerial vehicles (UAV) was studied, focusing on the effects of pesticide deposition on cotton leaves during the flowering period. Cotton leaves in 0°–30°, 30°–60°, 60°–90° leaf blade angle ranges (angle between the leaf blade and the horizontal plane) were examined. In the first experiment, four different prewetting volumes (0, 1.6, 3.2 and 4.8 L) were sprayed by a single-rotor electric UAV on four cotton plots (plots A–D) each with an area of 120 m², and then each area was sprayed with a 0.8% (w/v) ponceau 2R solution by another single-rotor electric UAV. The results revealed that with no prewetting, droplet deposition quantity decreased with increasing leaf blade inclination. After prewetting, the mean droplet deposition quantity on plots B, C and D increased by 39.8%, 9.7% and 24.9%, respectively. The prewetting rate of 1.6 L per 120 m² had the most significant effect on improving the deposition of droplets. It was also found that the mean droplet deposition quantity in each leaf blade angle range increased after prewetting. For the leaf blade angle range 60°–90°, this increase was the most pronounced, with 0.043, 0.062, 0.057 and 0.048 <font style="font-family:Symbol">m</font>L·cm⁻² in plots A–D, respectively. Also, droplet deposition uniformity in the leaf blade angle range 60°–90° was better after prewetting. These results should provide a valuable reference for future research and practice to improve the effectiveness of pesticides applied to cotton by aerial applications.

MULTI CRITERIA DECISION ANALYSIS AND ITS APPLICATION TO TECHNOLOGY SELECTION

Recently, environmental technologies are widely available to prevent pollution from industrial activities. The term Best Available Techniques (BAT) refers to technologies that can be used to overcome certain environmental problems. The selection of the right technology for pollution prevention involves a complicated process. Not only technical and economic aspects, but also environmental aspect should be considered as well. However, environmental aspect is difficult to quantify due to uncertainty in the real value of the environment. The aim of this study is to develop a framework for decision making process that incorporates the three aspects: technical, environmental, and economic in selecting the best technology which is relevant to a certain textile industry. One multi criteria decision analysis tool, Analytic Hierarchy Process (AHP), is used in this study to help decision maker in a textile industry to compare and rank three alternative technologies: substitution of mineral oil, pre-wetting process and compact spinning technology. Substitution is the most feasible option having benefit/cost (B/C) ratio 2.154, followed by compact spinning with B/C ratio 0.879. The result shows that AHP is capable to quantify both qualitative and quantitative criteria to aid decision maker in comparing several options and determining the best option.

Properties of recycled aggregate concrete with different water control methods

The paper studies the properties of Recycled Aggregate Concrete (RAC) with four different water control methods: the control group, pre-wetting with the same total water amount group, pre-wetting with the same mixing water amount group and adding extra mixing water group. Macro properties of concrete materials, i.e., compressive strength, drying shrinkage and chloride penetrability, and micro properties of Interfacial Transition Zone (ITZ), i.e., length and elastic modulus, are tested. The results show that RAC with a pre-wetting process has lower compressive strength and a higher Cl− diffusion coefficient, but a smaller shrinkage value compared to RAC with the same total water amount and no pre-wetting process. Adding extra mixing water process weakens the properties of RAC. The comprehensive elastic modulus is defined as an integrated interface parameter, and it has a good correlation with the macro properties like compressive strength and diffusion coefficient of Cl− of RAC.

Effects of Snailase Treatment on Wettability of Raw Cotton Yarns in Pre-wetting Process of Foam Sizing.

The main objective of the present study was to meticulously investigate an inclusive set of physicochemical properties of pre-wetted cotton yarns and optimize the snailase treatment for raw cotton yarns. Based on single factor design, effects of snailase treatment on the removal percentage of pectins and cotton waxes, wettability, and weight loss were studied in different snailase concentrations and the optimal concentration range was obtained. The Box-Behnken design was employed to determine the optimal condition of snailase treatment for achieving the maximum wettability of cotton yarns. The maximum wettability was obtained when treated at 16.90g/L of snailase concentration at 56.85°C for 27.77s. The theoretical and observed values were in reasonably good agreement, and the deviation was less than 1%. Results revealed that snailase had a positive effect on pectin and wax removal, had an obvious impact on weight loss, and significantly enhanced the wettability of raw cotton yarns.

Shrinkage of internal cured high strength engineered cementitious composite with pre-wetted sand-like zeolite

In this paper, shrinkage and internal relative humidity of internal cured with calcinated zeolite particles of high strength engineerined cementitious composite (HSECC) are experimentally investigated, in which the natural sand-like zeolite particles with average particle size of 0.18mm were used as internal curing agent. Impacting factors, such as calcination, pre-wetting process and amount of internal curing agent, on shrinkage of HSECC were considered in the test program; meanwhile their effects on compressive strength of the composites were included as well. The test results show: 1) Two-stage progressing mode of shrinkage and internal relative humidity of HSECC are observed; 2) Applying the pre-wetted calcined zeolite particles in HSECC, more than 60% of autogenous and/or drying shrinkage at 28days is reduced while the strength of the composite remains as higher as the reference; 3) Calcination on zeolite particles is necessary for internal curing of high strength cementitious composites.

Study on interface structure and performance of homogeneous-reinforced polyvinyl chloride hollow fiber membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating and matrix layers were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influence of various pre-wetting solutions on interface structure and performance of HR membranes were investigated. The results showed that the HRPVC membranes had a dense and smooth outer surface with no obvious pores. A dense interface was formed in the HR membrane between the coating layer and the matrix membrane without pre-wetting process. Due to the filling of the pores of the outer edge of the matrix membrane by pre-wet solutions, the HRPVC hollow fiber membranes formed porous interface in the coating process. The pure water flux of the pre-wet HR membranes was higher than that of the un-pre-wet HR membrane, but lower than that of the matrix membrane. The optimum properties of HRPVC membranes were obtained as the ethanol weight fraction reached 60 wt% in the pre-wet solutions. In the optimum pre-wetting conditions, the tensile strength of HRPVC hollow fiber membranes was 9.5 MPa, while the elongation-at-break value was 97.4 %.

Preparation and interface structure study on dual-layer polyvinyl chloride matrix reinforced hollow fiber membranes

Polyvinyl chloride (PVC) matrix reinforced hollow fiber membranes including separation layer and porous supported matrix were fabricated via dry–wet spinning process. The mixtures of PVC or polyvinylidene fluoride (PVDF) polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by a melt-spinning method. The influences of pre-wetting solutions and polymer concentration on structure and performance of homogenous-reinforced (HMR) PVC hollow fiber membranes were investigated. Furthermore, the interfacial bonding state of HMR PVC hollow fiber membranes was characterized by an indirect method and comparative analysis. The results showed that a dense interface formed in the HMR PVC hollow fiber membrane between these two layers without pre-wetting process. Compared with the matrix membrane which had a rougher outer surface with obvious big pores, the prepared HMR PVC hollow fiber membrane possessed a dense and smooth outer surface with no obvious big pores. Due to the filling of the pre-wet solutions into the pores in the outer edge of the matrix membrane, the HMR PVC hollow fiber membranes formed porous interface in the coating process which improved its permeability. The HMR PVC hollow fiber membranes had a more favorable interfacial bonding than the heterogeneous-reinforced (HTR) PVDF hollow fiber membranes. The tensile strength of prepared PVC matrix reinforced hollow fiber membranes was higher than 12MPa but lower than the original PVC hollow fiber matrix membrane.

Effect of pre-wetting time on oxidized coal flotation

In this investigation, we discussed the flotation behavior of oxidized coal treated by different pre-wetting times. The pre-wetting time is 1min, 2min, 3min, 4min and 5min, respectively. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle measurements were used to indicate the surface properties of oxidized coal. XPS results show that the hydrophobicity of oxidized coal is very low and the oxidized coal should be pre-wetted quickly as there are many hydrophilic functional groups and few hydrophobic functional groups on the oxidized coal surface. In addition, there are also many cracks and holes on the oxidized coal surface from SEM pictures. The cracks and holes should be covered or filled up with water during pre-wetting process. Contact angle measurement results show that the contact angle between the water drop and oxidized coal surface decreases rapidly with the increase of measurement time. Both of the combustible matter recovery and concentrate ash content decrease with the increase of pre-wetting time.