Browsing by Subject "Oil/water separation"

Now showing 1 - 3 of 3

Open Access
Superhydrophobic hexamethylene diisocyanate modified hydrolyzed polymers of ıntrinsic microporosity electrospun ultrafine fibrous membrane for the adsorption of organic compounds and oil/water separation
(American Chemical Society, 2018) Satılmış, Bekir; Uyar, Tamer
Polymers of intrinsic microporosity (PIMs) have gained significant research interest because of their successful applications in adsorption and separation. PIM-1 is the first and most studied member of this class because it shows specific interactions with some certain organic species. Chemical modification of PIM-1, which can be achieved by simply hydrolyzing the nitrile groups in the backbone, provides an advantage of tailoring its adsorption and separation performances. In this study, electrospinning of ultrafine fibers from hydrolyzed polymer of intrinsic microporosity (HPIM) and blends of hexamethylene diisocyanate (HMDI)/HPIM was achieved in several different ratios of HMDI/HPIM ranging from 1:9 to 1:1 (w/w). Bead-free and uniform fibers were obtained in the form of self-standing ultrafine fibrous membranes, which were then thermally treated at 150 °C to introduce chemical cross-linking between HMDI units and carbonyl groups of HPIM, resulting in HMDI-modified HPIM fibrous membranes (HMDI/HPIM-FMs). The solubility behavior has been altered by an introduced modification that makes membranes insoluble in all common organic solvents. Chemical cross-linking has been confirmed by using a Fourier transform infrared technique showing urethane linkage between HMDI and HPIM, and it was further supported by X-ray photoelectron microscopy and elemental analysis techniques that show a significant increase in the relative ratio of nitrogen in HMDI/HPIM-FMs compared to HPIM-FM. The average fiber diameters of fibrous membranes were found between 1.38 ± 0.29 and 0.96 ± 0.22 μm depending on the blend compositions and applied electrospinning parameters. Moreover, the water contact-angle value for HPIM-FM increased with the introduced HMDI modification from 140 ± 4° to 159 ± 7°, changing the nature of the membrane from hydrophobic to superhydrophobic. Consequently, HMDI/HPIM-FMs were successfully employed in oil/water separation due to the superhydrophobicity. In addition, the adsorption properties of HPIMFM and HMDI/HPIM-FMs were explored for common organic solvents. While both HPIM-FM and HMDI/HPIM-FMs show promising results, the structural stability of HMDI/HPIM-FMs in liquids was found to be more stable and reusable with respect to HPIM-FM. Hence, HMDI/HPIM-FMs are more favorable for organic adsorption and separation purposes from an aqueous system.
Open Access
Superhydrophobic, hybrid, electrospun cellulose acetate nanofibrous mats for oil/water separation by tailored surface modification
(American Chemical Society, 2016) Arslan, O.; Aytac Z.; Uyar, Tamer
Electrospun cellulose acetate nanofibers (CA-NF) have been modified with perfluoro alkoxysilanes (FS/CA-NF) for tailoring their chemical and physical features aiming oil-water separation purposes. Strikingly, hybrid FS/CA-NF showed that perfluoro groups are rigidly positioned on the outer surface of the nanofibers providing superhydrophobic characteristic with a water contact angle of ∼155°. Detailed analysis showed that hydrolysis/condensation reactions led to the modification of the acetylated β(1 → 4) linked d-glucose chains of CA transforming it into a superhydrophobic nanofibrous mat. Analytical data have revealed that CA-NF surfaces can be selectively controlled for fabricating the durable, robust and water resistant hybrid electrospun nanofibrous mat. The -OH groups available on the CA structure allowed the basic sol-gel reactions started by the reactive FS hybrid precursor system which can be monitored by spectroscopic analysis. Since alkoxysilane groups on the perfluoro silane compound are capable of reacting for condensation together with the CA, superhydrophobic nanofibrous mat is obtained via electrospinning. This structural modification led to the facile fabrication of the novel oil/water nanofibrous separator which functions effectively demonstrated by hexane/oil and water separation experiments. Perfluoro groups consequently modified the hydrophilic CA nanofibers into superhydrophobic character and therefore FS/CA-NF could be quite practical for future applications like water/oil separators, as well as self-cleaning or water resistant nanofibrous structures.
Open Access
Waxing the soot: Practical fabrication of all-organic superhydrophobic coatings from candle soot and carnauba wax
(Elsevier, 2021-02-04) Celik, N.; Celik, N. B.; Ruzi, M.; Önses, Mustafa Serdar
Commercial application of superhydrophobic coatings is hindered by insufficient durability and use of materials with high costs and limited availability. In this study, we report a robust water impact resistant all-organic superhydrophobic coating that is prepared from low-cost colloidal dispersion composed of carnauba wax and candle soot. The colloidal dispersion is stable and can be spray-coated onto virtually any surfaces. The coated surfaces exhibit superhydrophobicity with a water contact angle of 172° and sliding angle of 3°, and retain superhydrophobicity even after 400 cycles of continuous water spray with an impact pressure of 7.4 kPa. The synergetic combination of candle soot and carnauba wax, together with the deposition method, solvent used to disperse materials, and spray-coating distance are critically important for the superhydrophobicity and mechanical durability. The robustness of the coatings emerges from the two-tier hierarchical structure of the dried particles which is formed by evaporation induced self-assembly of wax molecules and candle soot nanoparticles. Applications in self-cleaning and oil/water separation are demonstrated, where a coated membrane can be continuously operated, solely driven by gravity, and can separate common organic liquids such as hexane and toluene from water with a separation efficiency of more than 90 % at a high flux of 1061 L / (m2 h).