Dataset for Hydrophobic poly(vinylidene fluoride) / siloxene nanofiltration membranes

Data collection method:

Materials Characterisation: The nanosheet morphology with elemental mapping was investigated by high-resolution TEM (JEM-2100Plus, JEOL) with EDS detector (X-Max detector, Oxford Instruments) and SAED was also obtained. The average thickness of the nanosheets was measured by AFM (Asylum Research Jupiter XR, Oxford Instruments). FTIR analysis was performed on siloxene-embedded KBr pellets using a Frontier FTIR spectrometer (Perkin Elmer) and Raman spectra were recorded with a RM1000 Raman Microscope (Renishaw) at 532 nm. XRD (D8-Advance PXRD, Bruker) with Cu Kα1 radiation source was operated at 40 kV and 40 mA (0.015° step size) to examine the crystallinity and phase of the siloxene powders. XPS was performed using a K-alpha+ spectrometer (Thermo Fisher Scientific) with survey scans recorded at 150 eV (1 eV step size) and high-resolution scans at 40 eV (0.1 eV step size). Hydrophilicity of the membranes was assessed using water contact angle goniometer (OCA15, Date Physics) in sessile mode at room temperature. 1 μL droplets of water were used and the values reported are the average of ten measurements at different positions. The surface zeta potential of each membrane sample was measured using a Zetasizer Nano (ZS, Malvern Instruments Ltd.) with the surface ζ accessory at neutral pH = 7.0. A tracer solution was prepared by adding a low concentration of polystyrene in 10 mM NaCl solution. Each sample was measured at least three times and the reported values were the average of the measurements. The surface roughness of the membrane samples was assessed by AFM (AFM Multimode IIIA, Bruker) in tapping mode over scan areas of 5 × 5 μm2. ATR-FTIR (Frontier, Perkin Elmer) was employed to characterize the chemical bonds on the membrane surface. The spectra were collected in the wavenumber range of 4000 to 600 cm-1 by accumulating 10 scans at a resolution of 4 cm-1. The distributions of siloxene on membrane surfaces were investigated by Raman mapping (RM1000 with inVia system, Renishaw) at 532 nm [25]. Areas of 100 × 100 μm2 were scanned on each membrane sample with the line mapping technique. XRD (D8-Advance PXRD, Bruker) with Cu Kα1 radiation source (1.5406 Å) was operated at 40 kV and 40 mA (0.015° step size) to examine the compactness of the PVSi membrane samples. The obtained spectra were analyzed using CrystalDiffract software (CrystalMaker Software Ltd, UK). 2 theta values are reported in Table 3 with 4 significant figures for ease of readability, whereas the original values have 6. The melting behavior of each membrane sample was characterized using differential scanning calorimetry (DSC Q20, TA Instruments). The samples were heated from room temperature (⁓ 20 °C) to 220 °C with a ramping rate of 10 °C min-1. The percentage crystallinity of PVDF in each sample was determined by crystallinity (%)=(ΔH_m)/(∆H_m^0 )×100% (1) where ΔHm is the enthalpy associated with membrane melting and ΔH0m is the theoretical melting enthalpy of 100% crystalline PVDF, which is 104.7 J g-1. The reported data were the average of three measurements taking from the same membrane sample. The dynamic mechanical properties of the membrane samples were analyzed using dynamic thermo-mechanical analysis (DMA1, Mettler Toledo) in auto-tension mode. The samples were cut into 20 × 5 mm2 strips. The sample strips were heated from – 80 °C to 145 °C with ramping rate of 3 °C min-1 in air. The data recorded were the average of three measurements. Membrane performance: Pure water and hexane permeation tests were conducted using a dead-end filtration cell (Sterlitech Corporation) connected with a 5 L feed tank. The operating pressure was fixed at 2 bar with compressed air. All the samples were compacted for 3 h prior to sample collection. The permeance, K (L m-1 h-1 bar-1), of the membrane was calculated by using Equation 2: K= V/∆t∆pA (2) where K is the permeance, V is the permeate volume, A is the effective membrane area (i.e., 14.6 cm2), Δt is the time for permeate collection and Δp is the operating pressure (i.e., 2 bar). After the pure water or solvent test, the membrane sample was transferred into a cross-flow cell for the rejection tests of different dyes and salts. The concentrations of all the dye feed solutions were 0.01 g L-1, whereas the concentrations of salt solutions were 1 g L-1 except for NaCl, which was 2 g L-1. The concentrations of dyes and salts in the feed, permeate and retentate solutions were measured by UV-visible spectrophotometer (Cary 100, Agilent) and conductivity meter (Thermo Fisher), respectively. The rejection of the tracer was calculated using Equation 3: R=(1-C_p/C_f )×100% (3) where R is the rejection, Cp and Cf are the tracer concentrations in the permeate and feed solutions, respectively. The mass balance for each rejection test was also calculated according to mass balance (%)=(C_p V_p+C_r V_r)/(C_f V_f )×100% (4) where Cr is the tracer concentration in the retentate solution, Vp, Vr and Vf are the volume of permeate, retentate and feed solutions, respectively. For all the filtration/separation tests, at least three samples were tested for each membrane and the average value was recorded.