Water Contact Angle Analysis Research Articles

Investigation on the interaction mechanism between nanocellulose and adhesion RH

A complex of resorcinol and hexamethylenetetramine (RH) was utilized to modify nanocellulose (NCC) using in‐suit solution method, where NCC was extracted from eucalyptus pulp paper with ultrasonic oxidation steps. The modified NCC was then put into vulcanized condition to simulate vulcanization process of rubber; the product was called vulcanized RH‐NCC model compound. In this paper, we study whether vulcanized conditions have influence on the interaction between RH and NCC by comparing changes of RH‐NCC model compounds before and after vulcanization. The analysis of thermogravimetry (TG), X‐Ray Diffraction (XRD), and water contact angle shows that addition of RH can improve some properties of NCC, which demonstrates well interaction between them. Fourier transform infrared (FTIR) test shows that there are no big changes before vulcanization; however, after simulated vulcanization, characteristic peaks of compound have changed a lot, illustrating that some chemical reactions have occurred. Further research on data from fitting peaks of hydrogen bonds and X‐ray photoelectron spectroscopy (XPS) analysis found that before vulcanization, mechanism between RH and NCC was mainly physical hydrogen interaction, and chemical interaction mechanism was also put forward after vulcanization.

Preparation and characterizations of oil palm fronds cellulose nanocrystal (OPF-CNC) as reinforcing filler in epoxy-Zn rich coating for mild steel corrosion protection

Oil palm frond (OPF) is one of largest contributions to the biomass waste from oil palm plantation. In this work, OPF has been successfully utilized to prepare cellulose nanocrystal (OPF-CNC) by acid hydrolysis. OPF was initially treated with autohydrolysis treatment. The obtained OPF-CNC was characterized via complementary analyses. The produced OPF-CNC showed a high crystallinity index value (60%) and high BET surface area (26.10 m2 g−1) as compared to α-cellulose (crystallinity index: 54% and BET surface area:7.14 m2g−1). The surface analyses via scanning electron microscope (SEM) and transmission electron microscopy (TEM) demonstrated that the OPF-CNC has a smooth surface with a needle-like shape, where the average length and diameter are 95.09 nm and 6.81 nm, respectively. The corrosion analyses via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) illustrate that the coated mild steel with the inclusion of 0.5 wt% OPF-CNC has managed to sharply reduce the corrosion (99%). The coated mild steel with the inclusion of 0.5 wt% OPF-CNC showed the highest hydrophobicity (100.5 ± 0.7°) and has lowest amount of O via water contact angle and energy dispersive X-ray spectroscopy (EDX) analyses respectively, indicating lowest corrosion rate.

Effect of nanoboehmite/poly(ethylene glycol) on the performance and physiochemical attributes EPVC nano-composite membranes in protein separation

The synergistic effect of nanoboehmite particles and various amounts of poly(ethylene glycol) (PEG 4000, 0−4 wt.%) as a pore-former agent on the characteristics, permeability and fouling resistance ability of the nanoboehmite/EPVC blended membranes has been investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and water contact angle analyses were utilized to examine the morphology, surface roughness, nanoboehmite dispersion and surface hydrophilicity, respectively. By increasing the PEG content in the EPVC dope solution, hydrophilicity, porosity and pores diameter improved, leading to the performance promotion of the membranes. The pure water flux (PWF), flux recovery ratio (FRR) and bovine serum albumin (BSA) flux of the nanoboehmite/EPVC composite membrane improved by enhancing the PEG loading up to 2 wt.% and then they dropped at higher content of it. Anti-fouling ability of the mixed-matrix nanoboehmite/EPVC composite membrane including 2 wt.% of PEG had a dramatic growth (68.3%) relative to the pristine EPVC membrane. Moreover, all the membranes were able to reject BSA proteins more than 98%. The obtained results displayed that the influence of PEG concentration enhancement on the characteristics and efficiency of the EPVC and EPVC/nano-composite membrane was different. The addition of various amounts of PEG to the nano-composite membranes matrix has not unfavorably influenced the amount of BSA rejection and membrane structure.

Facile and Effective Preparation of the Lotus Leaf-based Adsorbent by Exposing Cellulose Nanocrystal for Waste Water Treatment and Air Purification

One substantial plant waste, lotus leave was fabricated into lotus leave powder with different diameters by ball milling. The surface morphology, chemical composition, particle size, porosity parameters, crystal structure, and wettability of lotus leaf powders (LLPs) were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), laser particle size analysis, N2 adsorption/desorption, X-ray diffraction (XRD) analysis, and water contact angle (WCA) analysis, respectively. The results showed that the micro- and nanoscale waxy papilla structures on the surface of the lotus leaf were gradually destroyed by mechanical forces along with extended balling time. Accompanied re-exposing of -OH affluent cellulose nanocrystals (CNCs) was proved by HR-TEM, XRD, and FTIR. FTIR also revealed a hydroxyl to carboxyl transition on the surface of CNCs. Both the re-exposure of CNCs and thereof chemical structure transition after ball milling made the LLP a good candidate for pollutant adsorbent for dye, formaldehyde, and heavy metal ions.

Zwitterion Co-Polymer PEI-SBMA Nanofiltration Membrane Modified by Fast Second Interfacial Polymerization.

Nanofiltration membranes have evolved as a promising solution to tackle the clean water scarcity and wastewater treatment processes with their low energy requirement and environment friendly operating conditions. Thin film composite nanofiltration membranes with high permeability, and excellent antifouling and antibacterial properties are important component for wastewater treatment and clean drinking water production units. In the scope of this study, thin film composite nanofiltration membranes were fabricated using polyacrylonitrile (PAN) support and fast second interfacial polymerization modification methods by grafting polyethylene amine and zwitterionic sulfobutane methacrylate moieties. Chemical and physical alteration in structure of the membranes were characterized using methods like ATR-FTIR spectroscopy, XPS analysis, FESEM and AFM imaging. The effects of second interfacial polymerization to incorporate polyamide layer and ‘ion pair’ characteristics, in terms of water contact angle and surface charge analysis was investigated in correlation with nanofiltration performance. Furthermore, the membrane characteristics in terms of antifouling properties were evaluated using model protein foulants like bovine serum albumin and lysozyme. Antibacterial properties of the modified membranes were investigated using E. coli as model biofoulant. Overall, the effect of second interfacial polymerization without affecting the selectivity layer of nanofiltration membrane for their potential large-scale application was investigated in detail.

Ionic liquids-modified cellulose coated magnetic nanoparticles for enzyme immobilization: Improvement of catalytic performance

In this work, ionic liquids-modified magnetic carboxymethyl cellulose nanoparticles (IL-MCMC) were prepared and used as supports for enzyme immobilization. The specific activity of immobilized lipase PPL-IL-MCMC was 1.43 and 2.81 folds higher than that of free PPL and PPL-MCMC, respectively. Water contact angle analysis indicated that the introduction of ionic liquids increased the hydrophobicity of supports, which in tune induced the lid-opening of lipase, allowing its active sites to become more accessible. In addition, the affinity between lipase and substrate immobilized on the prepared supports was enhanced. The same method was also applied to analyze immobilize penicillin G acylase (PGA) to further investigate the general applicability of the method. The results showed that the immobilized PGA exhibited higher stability than many other reported PGAs. The developed composites may be utilized as excellent supports for enzyme immobilization in industrial application.

Characterization and physical properties of electrospun gelatin nanofibrous films by incorporation of nano-hydroxyapatite

In this study, the gelatin/nano-hydroxyapatite (n-HAP) composite nanofibrous films were fabricated by electrospinning. The gelatin/n-HAP mixtures in acetic aqueous solutions as the spinning dispersions showed a shear thinning behavior, and the apparent viscosity increased with the increasing n-HAP content. However, the average diameter of the gelatin nanofibers decreased from 516 to 510, 458 and 403 nm after the addition of 10%, 25% and 50% n-HAP, due to the decreased entanglement density. The EDS and TEM analysis indicated that n-HAP was uniformly dispersed within the nanofibers. As indicated by the FTIR results, the hydrogen bonding formed between gelatin and n-HAP resulted in the conformational transition of gelatin from β-sheet to turns. The water contact angle and XPS analysis suggested that the incorporation of n-HAP favored the wettability of the electrospun nanofibrous films, which was ascribed to the rough fiber surface and higher ratio of polar groups on the surface. The incorporation of 10% n-HAP did not affect the mechanical strength significantly, but the higher ratios of n-HAP led to the brittle and fragile property of the electrospun films. In addition, the water barrier property of the gelatin nanofibrous film was significantly improved by the addition of n-HAP. These results suggest that the surface wettability, mechanical strength and water barrier property of the electrospun gelatin nanofibrous films may be tuned by the incorporation of nano-hydroxyapatite.

Fabrication of PVDF/HMO Mixed Matrix Membrane: Effect of HMO Loading on Oil/Water Separation

In this research, polyvinylidene fluoride (PVDF) polymer was mixed with hydrous manganese oxide (HMO) nanoparticles to form a mixed matrix membrane (MMM) with excellent wetting properties to separate oil/water emulsion. Accordingly, the effects of different HMO loading (3, 5, 7 and 10 wt%) on the membrane’s water flux and oil rejection performance were studied. The characteristics of the MMM were demonstrated via scanning electron microscopy (SEM), atomic force microscopy (AFM), as well as water and oil contact angle analysis. The HMO nanoparticles, which has large amounts of hydroxyl (-OH) groups, enhanced the membrane’s hydrophilicity. The fabricated MMM became hydrophilic and underwater oleophobic with the presence of -OH groups on the membrane surface. Specifically, the MMM surface repelled the oil droplets and had high affinity towards the water molecules, thereby demonstrating good oil/water separation performance. PVDF/HMO with 10 wt% of HMO had the highest water flux (402 L/m2.h) and oil rejection rate (93%).

A Direct Comparison Between Poly(vinylidene) Flouride and Polysulfone Flat Sheet Membrane; Characterization and Mechanical Strength

Selecting a proper material is the first key step for determining suitable membrane application. Hence, the comparison of membrane properties is urgently required to be conducted. This work aimed to compare two common materials of polymer flat sheet membranes, i.e poly(vinylidene) fluoride (PVDF) and polysulfone (PSf), from preparation to characterization. Phase inversion method was applied for both materials using different solvent. PVDF was dissolved in N, N, dimethyl acetamide (DMAc) whereas PSf was dissolved in N-methyl pyrrolidone (NMP) with the same composition ratio of polymer and solvent. The properties of membranes were investigated by FTIR, FE-SEM, water contact angle, and Universal pull machine. FE-SEM result indicates that PSf membrane has larger pores than PVDF membrane. Meanwhile, water contact angle analysis describes that PVDF membrane is more hydrophilic than PSf membrane.

Utilization of waste polyvinyl chloride (PVC) for ultrafiltration membrane fabrication and its characterization

Waste plastic that has generally been considered as a nuisance in the environment is now being converted into a useful product. This work shows the feasibility of the utilization of waste polyvinyl chloride (PVC) as a membrane precursor. Waste derived PVC was blended with cellulose acetate to overcome the hydrophobic nature of PVC in membrane fabrication. The membranes were prepared via phase inversion using N-dimethyl formamide (DMF) induced by non-solvent. The characterization of the membranes was done using various techniques including field emission scanning electron microscopy, ImageJ software, Fourier transform infrared spectroscopy in attenuated total reflectance mode, thermo-gravimetric analysis, and measurement of water contact angle. The membrane properties were assessed by pure water flux (PWF) and bovine serum albumin (BSA) rejection, respectively. The outcome showed that the membrane had a PWF of 85 L/m2 h, BSA rejection of more than 90 % for the neat PVC membrane was recorded. The equilibrium water content was improved by ∼19 %, contact angle decreased by ∼25 % and hydrophilicity enhanced. Thus, this study gives insights that waste PVC can be utilized to fabricate an ultrafiltration (UF) membrane.

Thermodynamic Studies of Bovine Serum Albumin (BSA) Adsorption on Nylon Membrane

The aim of this study was to investigate the nylon membrane’s characteristics and thermodynamic aspects for adsorption of Bovine Serum Albumin (BSA) as a model protein on nylon membrane. The morphology characteristics analyzed by FESEM and wetting and weighting technique showed the nylon membrane possessed micro-pore size (0.159±0.039 µm) with high porosity (74.2820±0.0411 %) respectively. Thermodynamic studies indicated that the adsorption reaction was endothermic with positive value of standard enthalpy (∆rHθ = 107.7 kJ/mole) and dominated by chemical adsorption. The results were supported with the analysis of functional groups of the nylon membrane with FTIR-ATR. Bands corresponding to the NH bonds stretching were generally detected in the 3500-3100 cm-1 range. The existence of C=O stretching vibration of carbonyl group was further confirmed with the observation of peak at 1632. 42 cm-1. The water contact angle analysis showed the hydrophilicity nature of nylon membrane with contact angle of 55.6°. These findings are expected to be used in the modification of nylon membrane for an optimum adsorption of protein.

Susceptibility of hybrid sol-gel (TEOS-APTES) doped with caffeine as potent corrosion protective coatings for mild steel in 3.5 wt.% NaCl

A series of hybrid sol-gel matrices were synthesized using 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) incorporating caffeine extracted from leaves of tea. Corrosion inhibition performances of coated mild steel panels exposed to 3.5 wt.% NaCl were evaluated employing electrochemical measurements. Data acquired using complementary corrosion analyses were in accordance where 100 ppm caffeine-doped hybrid sol-gel coating offered the highest inhibition efficiency at 88.79 %. Tafel curves suggested that silane coatings mitigated both the anodic and cathodic reactions simultaneously, i.e. a mixed-type inhibition. Coatings were characterized using FT-IR, SEM/EDX and water contact angle measurements. IR absorption peak obtained at 954 cm−1 revealed the formation of FeOSi bonds. 100 ppm caffeine-doped silane coating offered the highest corrosion resistance since the corrosion protective barrier minimized the oxidation of mild steel to a greater extent where the EDX analysis showed a high intense signal of Fe. Water contact angle analysis depicted the hydrophobicity of coated panels suggesting the tendency of being less prone to water.

Preparation of floatable TiO 2 /poly(vinyl alcohol)‐alginate composite for the photodegradation of ammonia wastewater

The use of floatable photocatalyst supports is an operable strategy of increasing photocatalytic performance in terms of improving light absorption. In this work, floatable organic support based on poly(vinyl alcohol) (PVA) was used to float commercial TiO2 P25 nanoparticles. At first, by the use of CaCl2 and boric acid at pH 3 the cross-linking of PVA blended with sodium alginate (PVA-Alg) was improved to enhance chemical and mechanical stability, and then it was chemically modified by trimethylchlorosilane to achieve floatable organic support (modified or MPVA-Alg). The prepared support and photocatalyst were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX)-elemental mapping, inductively coupled plasma optical emission spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, photoluminescence (PL), thermalgravimetry, Brunauer-Emmett-Teller (BET), and water contact angle (WCA) analyses and applied for the ammonia degradation under UV to visible regions. Results of WCA and FTIR confirmed that chemical modification of PVA-Alg led to lowering hydrophilicity to be floated on the ammonia wastewater. UV-vis analysis indicated that the MPVA-Alg acts as a light absorbent in UV-vis ranges and makes TiO2/MPVA-Alg a visible light active composite. Also, the PL analysis showed that the charge recombination process was strongly suppressed in the case of the TiO2/MPVA-Alg sample. BET theory suggested that the textural properties were not the key factor in determining photocatalytic performance. The maximum photocatalytic ammonia removal was obtained to be 63% and 57% by the TiO2/MPVA-Alg composite under UV-vis light irradiations, respectively. The MPVA-Alg and TiO2 exhibited the ammonia degradation of 28.5% and 15.2% under visible and 29.4% and 40.0% under UV irradiation, respectively. The TiO2/MPVA-Alg showed favorable reuse ability after five runs due to desirable chemical and mechanical resistance. This study provides an insight into the modification of polymeric structures to be used as both floatable photocatalyst support and light sensitizer.

Facile preparation of medical segmented poly(ester-urethane) containing uniformly sized hard segments and phosphorylcholine groups for improved hemocompatibility.

In order to improve the hemocompatibility of durable medical-grade polyurethane, a novel series of segmented poly(ester-urethane)s containing uniformly sized hard segments and phosphorylcholine (PC) groups on the side chains (SPU-PCs) was prepared by a facile method. The 2-methacryloyloxyethyl phosphorylcholine (MPC) was first reacted with α-thioglycerol by Michael addition to give a diol compound (MPC-diol), then the SPU-PCs with various PC content were prepared by a one-step chain extension of the mixture of MPC-diol and poly(ε-caprolactone) diol (PCL-diol) with aliphatic diurethane diisocyanates (HBH). The chemical structures of MPC-diol and SPU-PCs were confirmed by 1H NMR and FT-IR, and the influences of PC content on the physicochemical properties of the SPU-PC films were studied. The introduction of PC groups enhanced the degree of micro-phase separation and improved the hydrolytic degradation of the films. Due to the denser hydrogen bonds formed in the uniformly sized hard segments, the films exhibited favorable tensile properties and a slow hydrolytic degradation rate. The results of water contact angle and XPS analysis indicated that the PC groups on the flexible side chains were concentrated on the surface after contact with water. The surface hemocompatibility of the films was evaluated by testing the protein adsorption and platelet adhesion, and the results revealed that the films surfaces could dramatically suppress the protein adsorption and platelet adhesion. The PC-containing polyurethane films possessed outstanding tensile properties, low degradation rate and good surface hemocompatibility, implying their great potential for use as long-term implant or blood-contacting devices.

Improving the performance of loose nanofiltration membranes by poly-dopamine/zwitterionic polymer coating with hydroxyl radical activation

A growing number of sewage treatment plants are utilizing the membrane separation technology for wastewater bleaching and desalination. The surface characteristics of the membrane selective layer have a great impact on the filtration and separation performance. In this study, a facile mussel-inspired method was employed for fabricating loose NF membrane. Hydroxyl radical activation generated by CuSO4/H2O2 was used to realize a rapid polydopamine (PDA) deposition. To obtain an electroneutral, anti-fouling and anti-bacterial surface, a zwitterionic polymer (SBMA) was introduced for PDA/SBMA codeposition and polymerization. XPS, FTIR, SEM, AFM and water contact angle analysis were employed to investigate the characteristics of the selective layer. The RD-1S membrane (2 mg/mL PDA and 2 mg/mL SBMA utilized) shows the optimal surface property. In addition, the filtration and separation performance of multivalent salts (monovalent and divalent ion) and dyes (negatively and positively charged) were investigated in detail. The separation capability of membrane exhibited a high dye rejection and a low salt rejection. The anti-fouling performance of the RD-1S membrane was observed to be excellent, especially from the point of view of fouling resistance reversibility. The elevated surface charge might be the main reason for the significant decrease of irreversible fouling of the RD-1S membrane. Furthermore, the co-existence of chelated copper and SBMA resulted in a reliable anti-bacterial performance. Overall, the separation and anti-bacterial performance of the functional loose NF membrane were comprehensively investigated.

Electrospun cellulose acetate butyrate/polyethylene glycol (CAB/PEG) composite nanofibers: A potential scaffold for tissue engineering

Electrospinning is a common method to prepare nanofiber scaffolds for tissue engineering. One of the common cellulose esters, cellulose acetate butyrate (CAB), has been electrospun into nanofibers and studied. However, the intrinsic hydrophobicity of CAB limits its application in tissue engineering as it retards cell adhesion. In this study, the properties of CAB nanofibers were improved by fabricating the composite nanofibers made of CAB and hydrophilic polyethylene glycol (PEG). Different ratios of CAB to PEG were tested and only the ratio of 2:1 resulted in smooth and bead-free nanofibers. The tensile test results show that CAB/PEG composite nanofibers have 2-fold higher tensile strength than pure CAB nanofibers. The hydrophobicity of the composite nanofibers was also reduced based on the water contact angle analysis. As the hydrophilicity increases, the swelling ability of the composite nanofiber increases by 2-fold with more rapid biodegradation. The biocompatibility of the nanofibers was tested with normal human dermal fibroblasts (NHDF). The cell viability assay results revealed that the nanofibers are non-toxic. In addition to that, CAB/PEG nanofibers have better cell attachment compared to pure CAB nanofibers. Based on this study, CAB/PEG composite nanofibers could potentially be used as a nanofiber scaffold for applications in tissue engineering.

Synthesis and surface properties of novel fluorinated polyurethane base on F‐containing chain extender

A novel fluorinated chain extender, (1‐(ethyl(2‐hydroxyethyl)amino)‐3‐ ((3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)oxy)propan‐2‐ol) (FPO), was synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and elemental analysis. Poly (ether urethane)s containing various amounts of the chain extender with fluorinated side chains (FPUs) were prepared by isophorone diisocyanate (IPDI), polytetra‐methylene‐ether‐glycol (PTMG), 3‐aminopropyltriethoxysilane (KH‐550), and 1,4‐butandiol (BDO). Films of FPUs were investigated by water absorption, contact angle, pencil hardness, adhesive force, and thermal analysis. Coating FPUs on micro‐nano concave‐convex structure plate realizes superhydrophobic performance. Scanning electron microscope (SEM) and atomic force microscopy (AFM) demonstrated that there is a lot of irregular concave‐convex structure, which forms a typical air cushion model. X‐ray photoelectron spectroscopy (XPS) analysis showed that surface fluorine content is 165% more than that of film average fluorine content. The superhydrophobic plate with 10% or higher F‐containing FPUs coating is of outstanding chemical corrosion resistance, excellent solvent resistance, and wear resistance.

Osteogenic scaffolds based on fumaric/N-isopropylacrylamide copolymers: Designed, properties and biocompatibility studies

In the present work the creation of a new biomaterial aimed at bone tissue regeneration is shown, covering the synthesis of the polymers, the material design and their exhaustive physicochemical and biological characterization. The copolymers of dioctyl fumarate (DOF) and N-isopropylacrylamide (NIPAM) were synthetized and characterized by size exclusion chromatography, 1H NMR and its thermal properties were studied by DSC and TGA analyses. Based on their properties, two copolymers with different DOF content were selected as raw material to design scaffolds for bone tissue regeneration. The scaffolds were prepared by casting and electrospinning technique, giving rise to biomaterials with particular chemical and topographic surface which were characterized by water contact angle and scanning electron microscopy (SEM) analysis. The cytotoxicity and biodegradation by murine macrophage RAW 264.7 cells was assay, while biocompatibility and osteogenic induction were made using bone marrow progenitor cells (BMPC). None of the biomaterials obtained showed cytotoxicity. The biological properties suggest that the cells adhere and proliferate better on biomaterials with higher DOF content and fibrous morphology. All scaffolds support osteoblastic cell differentiation, but to a greater extent on the biomaterial that has higher DOF content prepared by casting. Altogether, our results suggesting that these biomaterials could be useful in the bone tissue engineering.

Surface modification of polyvinylidene fluoride membranes with ZIF-8 nanoparticles layer using interfacial method for BSA separation and dye removal

In this research, porous polyvinylidene fluoride (PVDF) membranes were prepared by the phase inversion method and coated with ultra-thin zeolitic imidazolate framework-8 (ZIF-8) layer using interfacial synthesis to fabricate an inorganic-organic nanofiltration membrane with good antifouling properties. The ZIF-8 layer was created by interfacial reaction of Zn2+ aqueous solution and 2-methylimidazole/n-hexane solution by two steps immersion of the PVDF support in these solutions with different contact times (1, 2, 3, 5 and 8 h). The coated ZIF-8 layer on the surface of membranes was characterized with SEM, EDX, ATR-FTIR and XRD analyses. Effect of the ZIF-8 on membrane hydrophilicity was studied by the water contact angle analysis. Also, water flux, BSA protein solution flux and dye rejection were investigated using a dead-end membrane cell test. The results showed that the membranes flux was significantly increased by modifying the membrane surface by ZIF-8 due to hydrophilicity improvement and formation of special water-pass channels in ZIF-8 layer. With increasing reaction time of interfacial synthesis, the flux decreased due to the increased thickness of the deposited layer. Three types of dyes (Rhodamine B, Reactive Green 19 and Direct Black 38) were applied for rejection test and the fabricated membranes indicated high capability in the dyes solution removal (74%, 82% and 98%, respectively). The ZIF-8 coated membranes presented appropriate antifouling properties.

Phase separation and performance of polyethersulfone/cellulose nanocrystals membranes

We investigate the effect of cellulose nanocrystals (CNC) as a hydrophilic nanoparticle on the characteristics of polyethersulfone (PES) based membranes. The membranes are fabricated using typical nonsolvent induced phase separation (NIPS) method. We study the radius of gyration and aggregation of PES in dimethylformamide in the presence of CNC, the rheological behavior of dope dispersions, and the morphology, permeability, irreversible fouling, MWCO, ζ-potential, water contact angle and mechanical properties of final membranes. Small-angle X-ray scattering (SAXS) analysis show that high CNC and water concentrations lead a transition from mass fractal to surface fractal scattering. Addition of CNC into the PES solution induces the formation of an interconnected polymer network, yet excess CNC loading eventually results in a heterogeneous composite with diminished mechanical properties. Additionally, an increase in the viscosity and elasticity of the dope dispersions is observed in the presence of CNC, which changes the morphology of the final membranes. The CNC concentration up to 1.5 wt% increases the water permeability of membrane while retaining the same dye rejection and fouling resistance as the neat one. The enhanced performance of PES/CNC membrane is related to the rheological properties and phase separation behavior of the cast dispersion. The results of water contact angle analysis confirm the higher wettability of the CNC filled membranes. Incorporation of up the 2 wt% CNC leads to a higher strength but lower ductility in comparison to the neat PES membrane.