Water Oil Contact Angle Research Articles

Preparation of nanocellulose by a biological method from hemp stalk in contrast to the chemical method and its application on the electrospun composite film.

In this study, CNFs were provided by an efficient, unmodified, and clean biological method with enzymes and a small amount of alkali, compared to the CNCs with the chemical method involving a strong acid. To provide an accurate targeted selection for future applications, we made the following comparison by analyzing the differences in the preparation method, performance, and application performance of the two nanocelluloses. The result of this study indicated that CNFs and CNCs exhibited a crystallinity index of 58.2 and 83.5%, respectively. CNFs had a mean length (L) of 192.3 nm and a diameter (D) of 1.9 nm, and the average L and D of CNCs reached 123.6 nm and 3.7 nm, respectively. The solution viscosity of CNFs and CNCs reached 7.46 Pa s and 1.91 Pa s, respectively. CNFs and CNCs exhibited zeta potential values of -88.26 mV and -26.40 mV, respectively. The electrospun composite film of PLA-CNFs and PLA-CNCs achieved water contact angles of 138.7 and 34.5°, and the water-oil contact angle reached 24.7 and 30.5°, respectively. The breaking strength of PLA-CNFs and PLA-CNCs reached 96.07 cN and 163.23 cN, and the break elongation followed an order of PLA-CNCs (32.16%) < PLA-CNFs (34.70%). In brief, CNFs can make the composite membrane hydrophobic and with superior extension, and CNCs can make the composite membrane hydrophilic and enhance its strength. Both the composite films conformed to the non-toxic standard, and the PLA-CNFs film more significantly contributed to the cell growth, which is expected to serve as a medical material.

An efficient and simple strategy for fabricating a polypyrrole decorated ceramic-polymeric porous membrane for purification of a variety of oily wastewater streams

A ceramic-polymeric membrane was fabricated through in-situ oxidative polymerization of pyrrole (Py) on alumina (Al2O3) ceramic ultrafiltration support. The establishment of polypyrrole (PPy) active layer on the ceramic support led to a new PPy coated ceramic-polymeric membrane. Various salient features such as surface wettability, surface morphology, composition and functional goups of PPy coated ceramic-polymeric membrane were determined by various characterization techniques water contact angle (WCA), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis and attenuated total reflectance fourier transform infrared (ATR-FTIR). The PPy coated ceramic-polymeric membrane showed superhydrophilic nature owing to its under water oil contact angle of ≥160° (superoleophobic). Thanks to stable deposition of PPy active layer on ceramic support, the membrane retained a separation efficiency of >99% for O/W emulsions at varied transmembrane pressures ranging from 0.5 bar to 2 bar with a feed concentration of 125 ppm of oil in water. Moreover, the PPy coated ceramic-polymeric membrane exhibited an ideal behaviour to the applied transmembrane pressure with a linear increase from 380 LMH to 2112 LMH in permeate flux as the pressure increased from 0.5 bar to 2 bar. As the concentration of oil was raised from 50 ppm to 250 ppm, the separation efficeincy separation remained at >99%. From among the different types of oils (Motor oil, Diesel oil and Crude oil) to mimic the oily waste water streams, the permeate flux was found to be highest in case of motor oil with a value reaching to 1690 LMH at 1 bar. The stability test revealed that the PPy coated ceramic-polymeric membrane was able to separate >99% of 125 ppm O/W surfactant stabilized emulsion for a period of 420 min.

Synthesis and properties of the active polymer for enhanced heavy oil recovery

With the continued recovery of heavy oil, conventional polymer flooding cannot be applied to heavy oil reservoirs gradually due to the characteristics of heavy oil reservoirs. To study oil displacement agent suitable for enhanced heavy oil recovery and investigate the effect of EO chain length on the performances, acrylamide, acrylic acid, lauryl methacrylate and C 10 -C 16 alkylphenol ethoxylates were selected to co-polymerize into the active polymer PAAP-x with different EO chain length (14, 16, 18, 20 and 22). Proton nuclear magnetic resonance analysis indicated PAAP-x as the target product. The optimal EO chain length of PAAP-x was determined to be 18 by the analysis of thickening, salt-tolerance, interfacial activity, wettability, viscosity reduction and recovery. Compared with conventional polymer P1, 1500 mg/L PAAP-18 exhibited superior performances with salinity of 6882.2 mg/L: (1) PAAP-18 could maintain the viscosity of 113.1 mPa . s, while P1was 44.8 mPa . s. (2) PAAP-18 could reduce the water-oil IFT from 44.4 mN/m to 13.0 mN/m, while P1 was to 30.6 mN/m, and the water-oil contact angle was 58.2°and 108.5°, respectively. (3) The heavy oil viscosity reduction rate of PAAP-18 was 81.7% at 50 °C, while P1 was only 33.8%. (4) PAAP-18 enhanced heavy oil recovery by 19.85% on the basis of water flooding while conventional polymer was only 8.69%. This study has theoretical guidance and practical significance for the study on new oil displacement agent to enhance heavy oil recovery. • Active polymer PAAP with optimal EO chain length of 18 were successfully synthesized. • PAAP-18 was better than conventional polymer in performances. • PAAP-18 could enhance heavy oil recovery by 19.85% on the basis of water flooding. • PAAP-18 simultaneously improve the oil displacement efficiency and the sweep efficiency.

Development of a superhydrophilic nanofiber membrane for oil/water emulsion separation via modification of polyacrylonitrile/polyaniline composite

In this research, polyaniline (PANI) was used to modify polyacrylonitrile (PAN) electrospun nanofibers for separating oil/water (O/W) emulsions due to its hydrophilic amino groups and simple synthesis. The fabrication of PAN/PANI membranes was carried out by two different methods: blending of PANI with PAN in pre‐electrospinning solution and coating of PANI on the PAN electrospun nanofibers using in situ polymerization of aniline. The effect of PANI composition (10, 20, 30 and 40 wt% with respect to the weight of PAN) and electrospinning temperature (25°C, 40°C and 55°C) was investigated in PAN/PANI membrane fabrication. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), water and under water oil contact angle (WCA and UOCA) measurement and mechanical tensile test. Regarding the results, PAN/40%PANI nanofibers prepared at 40°C was considered as the superhydrophilic nanofibers (WCA &lt; 5°) and the most suitable membrane among the samples for separation of O/W emulsions. Separation studies revealed a flux of 1300 Lmh (pure water) under gravity and an efficient oil rejection of about 98.8% for PAN/40%PANI@40°C membrane. Hence, the PAN/40%PANI@40°C membrane was subjected to additional tests including separation of different industrial oils, emulsion separation with surfactant agent, separation under harsh acidic/basic conditions and fouling test. The results confirmed an efficient performance of the obtained superhydrophilic membrane for O/W separation, which make it a potential candidate for the purification of water from industrial organic pollutant.

Direct observation of two-phase flow in deformable fractures of shales: A Utica shale example

Despite the success of hydrocarbon production from unconventional shale reservoirs, the physical processes controlling the production are not yet fully understood. The wettability controlling the two-phase flow in deformable natural fractures of shale is among the processes that still need special attention. With the advances of optical technologies, microfluidics can now be used to observe, measure, and analyse the dynamic changes of flow in fractured systems. However, mimicking the natural wall roughness of the fractures with high precision and having flexibility to allow fracture deformation has remained challenging.We have therefore developed a new microfluidic technique to create tensile fractures in shale with subsurface representative random geometries and roughness, and then observed two-phase flow in these deformable fractures at a high resolution for Utica shale. During the two-phase flow, dynamic contact angles of water-oil in the fractures with varying apertures of 60–100 μm were measured and analysed.Significant contact angle hysteresis was observed when oil displaced water out of the fracture and vice versa. Interestingly, water completely displaced the oil out of the fracture through spontaneous imbibition, although its contact angle in the fracture varied from 20° to 90°. The water velocity in the fracture was found to be correlated to the observed contact angles during the spontaneous imbibition test. The large change in the contact angle was further investigated using fluorescence tracking where patches of oil were observed to remain on the fracture wall despite its water wetness. It was then shown through further investigations that the formation of these oil patches was primarily controlled by mineral heterogeneity than wall roughness.

Hydrophilic/underwater superoleophobic graphene oxide membrane intercalated by TiO2 nanotubes for oil/water separation

Membrane technology for oil/water separation has received increasing attention in recent years. In this study, the hydrophilic/underwater superoleophobic membrane with enhanced water permeability and antifouling ability were fabricated by synergistically assembling graphene oxide (GO) nanosheets and titanium dioxide (TiO2) nanotubes for oil/water separation. GO/TiO2 membrane exhibits hydrophilic and underwater superoleophobic properties with water contact angle of 62° and under water oil contact angle of 162.8°. GO/TiO2 membrane shows greater water permeability with the water flux up to 531 L/ (m2$h$bar), which was more than 5 times that of the pristine GO membrane. Moreover, GO/TiO2 membrane had excellent oil/water separation efficiency and anti-oil-fouling capability, as oil residual in filtrate after separation was below 5 mg/L and flux recovery ratios were over 80%.The results indicate that the intercalation of TiO2 nanotubes into adjacent GO nanosheets enlarged the channel structure and modified surface topography of the obtained GO/TiO2 membranes, which improved the hydrophilicity, permeability and anti-oil-fouling ability of the membranes, enlightening the great prospects of GO/TiO2 membrane in oil-water treatment.

Wettability Alteration of Dolomite Rock Using Nanofluids for Enhanced Oil Recovery

Wettability alteration of rock by surfactant has been considered as feasible method for recovery of oil reservoirs by modifying the wettability of rock surface from oil-wet to water-wet condition. The impact of surfactant can be enhanced by adding nanoparticles. Cationic surfactant performed well in carbonate rock by forming ion pairs between cationic head and acidic component of the crude. Meanwhile, nanoparticles will form continuous wedge film between the liquid and solid surface. In this paper, Al2O3 and ZrO2 nanoparticles were used as enhanced oil recovery (EOR) agents. The impact of these two nanoparticles on contact angle and interfacial tension was studied. Besides that, adsorption Cetyltrimethylammonium Bromide (CTAB) surfactant on rock surface was also investigated. The results show a significant change in water-oil contact angle after application of surfactant and nanoparticles. Initial water-oil contact angle for 6 dolomites demonstrate oil-wet condition. Then, the dolomites were submerged in prepared solution for 48 hours. The result shows that, dolomites 2, 5 and 6 changes drastically to more water-wet condition with contact angle 56°, 40° and 47° respectively. For surfactant adsorption, the adsorption is very fast at the beginning. The adsorption rate after 5 minutes was 50 mg/g and after 60 minutes the adsorption rate was 310 mg/g. The adsorption rate slowed down after 60 minutes and after 180 minutes the adsorption rate was 315 mg/g in which the rate of adsorption achieve equilibrium. Nanoparticles retention test and Zeta potential shows that Al2O3 is more stable than ZrO2. The results for interfacial tension (IFT) also show a significant reduction. The IFT value reduces from 8.46 mN/m to 1.65 mN/m and 1.85 mN/m after the application of Al2O3 and ZrO2 nanofluids respectively

Investigating the effect of Water-oil repellency finish on baby clothes

In this paper, fuzzy logic method was used to model the effect of stain repellent treatment on plush knitted fabrics intended for baby clothes. In order to reduce the complexity of the models and increase the knowledge and comprehension of the underlying process, a fuzzy sensitivity variation criterion was used to select the most relevant parameters which are taken as inputs of the reduced fuzzy logic models. The outputs are the water-oil contact angles characterizing the stain repellent behavior of fabrics and the percentage of decrease of air permeability to control the change of hygienic comfort. Obtained results showed that the hydrophilic samples were transformed to water-oil repellent ones and some experimental conditions induce a high contact angle without affecting the air permeability.

Wettability alteration and oil recovery by water imbibition at elevated temperatures

This investigation adopts a new perspective on wettability alteration as a function of temperature. Colloidal (i.e., DLVO) theory and calculations are used to interpret results from laboratory-scale displacements. Water imbibition tests were conducted with 9 reservoir cores from a diatomaceous reservoir. Permeability and porosity of cores varied from 0.2 to 0.7 md and 46% to 65%, respectively. The experiments included spontaneous counter-current water imbibition followed by forced co-current water imbibition to residual oil saturation. The fluids were 34° API crude oil and synthetic formation brine. All tests were isothermal and temperatures ranged from 45 to 230 °C at pressures sufficient to maintain liquid water. The experimental results show that an increase in temperature results in: (1) a substantial increase in imbibition rate and extent of oil recovery, (2) a slight reduction in residual oil saturation, and (3) a significant shift in the Amott wettability index from intermediate and weakly water wet to strongly water wet. DLVO calculations illustrate detachment of fines from pore surfaces at high temperature. Fines detachment is a mechanism for altering wettability. Release of fines coated with oil exposes clean water-wet pore surfaces. Further calculations indicate the water–oil contact angle decreases as temperature increases indicating a systematic increase in water wettability consistent with experimental measurements of the Amott index.

Wettability heterogeneities in gas injection; experiments and modelling

We carried out experiments to study the effect of wettability heterogeneities on: (1) displacement mechanisms, (2) sweep efficiency and (3) trapped oil quantities and fluid distribution in three-phase gas injection and developed a theoretical simulator. Secondary gas injection experiments was conducted in transparent glass micromodels of heterogeneous wettability. Oil-wet patches in a water-wet matrix were obtained by selective silane grafting on the glass surface. Different heterogeneity patterns were considered for the same oil-wet over water-wet surface ratio. Displacement sequences were video-recorded and fluid saturations determined by image analysis. A theoretical model of three-phase flow in a porous structure was developed. In this model the porous medium is simulated as a network of interconnected pores. The model permits an imposition of heterogeneous wettability by assigning different water-oil contact angles according to the desired wettability pattern. The calculation of flow within the network takes into account the flow of oil through wetting and spreading films and the displacement mechanisms observed in the transparent micromodels. Comparison between experimental results and simulations shows that the size and distribution of wettability heterogeneities strongly affects microscopic and macroscopic behaviour during gas injection.