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In this work simulation results for the pore wetting of vacuum membrane distillation (VMD) are reported, considering heat and mass balance at liquid/vapor interface when steady state is achieved. Two cases were studied. In case 1, the system is in isothermal condition. In case 2, heat enters only from the pore inlet and is removed at the liquid/vapor interface as liquid vaporizes. The simulation has shown that the liquid/vapor boundary may remain inside the pore at the steady state condition, which means the partial pore wetting is possible. The significant temperature drop from the pore entrance to the liquid/vapor interface has also been predicted. It was found from case 2 simulation that VMD is possible in a wider range of pore radius, r, than the Laplace equation predicts. As well, the possibility of VMD for the contact angle (θ) below 90° was justified.

Functionalization of poly(vinylidene fluoride) (PVDF) nanohybrid has been performed in template system using two-dimensional layered silicate and superior fuel cell membrane has been demonstrated. Sulfonation of nanohybrid has been carried out at control condition to maintain the mechanical stiffness and toughness of the membrane using chlorosulfonic acid and the results have been compared with pure PVDF. The sulfonation and its relative extent have been confirmed through NMR, FTIR and UV–vis measurements showing greater degree of functionalization in nanohybrid which arises from the specific arrangement of polymer chains on top of nanoplatelets. The structural change over from common crystallized form α- to piezoelectric β-phase in nanohybrid has been established and the amount of β-phase has been enhanced after sulfonation as evident from deconvoluted XRD patterns and DSC measurement. A plausible mechanism has been proposed for this improvement which led to the formation of smart membrane. Essential criteria of an ideal membrane have been verified through high water uptake, low permeability and hydrophilic nature by measuring contact angle. The molecular level clustering due to the attachment of sulfonate group in main chain has been explored which in turn explain the higher barrier property both for gas and liquid (fuel). Proton conductivity of functionalized nanohybrid has been found to be quite high along with significantly low methanol cross over as compared to standard Nafion membrane. I–V characteristics of the nanohybrid membrane show high potential at low current density with considerably lower value of slope. Membrane electrode assembly using functionalized nanohybrid exhibit significantly high value of current density and prove its worth for superior fuel cell membrane using common thermoplastic polymer.

Porous asymmetric polyvinylidene fluoride (PVDF) hollow fiber membrane were fabricated via a phase-inversion method using surface modifying macromolecules (SMM) (1 wt%) as the additive in the spinning dope. Distilled water and tap water were used as internal and external coagulation bath, respectively. The membranes were characterized in terms of gas permeation, wetting resistance, overall porosity, contact angle and collapsing pressure. CO2 stripping from diethanolamine (DEA) solutions was conducted through the gas–liquid membrane contactor. The effect of some operating conditions such as gas and liquid velocities, DEA concentration and rich solution temperature on the CO2 stripping flux and efficiency were investigated. By increasing liquid flow rate to 200 ml.min−1, the maximum CO2 stripping efficiency of almost 82% was achieved. In addition, an increase in the liquid flow rate resulted in a significant increase of CO2 stripping flux. By increasing the liquid flow rate from 50 to 200 ml min−1, the CO2 flux increased by 900%. By increasing the gas velocity the CO2 desorption flux increased but this changing was negligible. The effect of rich solution temperature was investigated and the results showed that the CO2 desorption flux increased with increasing the solution temperature from 80 to 90 °C. The results of DEA concentration enhancement on the CO2 desorption flux showed that the CO2 stripping flux increased drastically with enrichment of the DEA concentration from 1.0 to 3.0 (mol l−1). Therefore, the higher stripping efficiency can be achieved by applying the higher liquid flow rate, temperature and DEA concentration in the absorbent liquid in the membrane contactor module.

A novel surface modified polyvinylidene fluoride (PVDF) hollow fiber membrane was fabricated via a dry–wet phased inversion process. A surface modifying macromolecule (SMM) was used as an additive in the spinning dope. During phase inversion SMM migrates to the membrane surface and functions as both a pore former and surface modifier. The surface modified PVDF membrane showed large pore size, higher effective surface porosity, contact angle and porosity but lower critical water entry pressure compared to the PVDF hollow fiber membrane without SMM. The performance of the surface modified membrane in contactor application for CO2 absorption via distilled water as absorbent was studied. The results show that the surface modified PVDF membrane has higher performance compared to control PVDF membranes. With the membrane prepared from SMM in the spinning dope a maximum CO2 flux of 7.7×10−4 mol/m2 s was achieved at 300 ml/min of absorbent flow rate, which was almost 93% more than the other membrane. In a long-term stability study, CO2 flux was decreased only about 7.7% by using surface modified PVDF membrane during 150 h operation.

Pharmaceutical and personal care products (PPCPs) enter the environment mainly through municipal wastewater effluents, agricultural run-off, pharmaceutical and related chemical industry discharges. The present study was conducted to remove PPCPs through nano-filtration (NF) membranes prepared with two different tailor-made polymeric additives. The first is a novel charged surface modifying macromolecule (CSMM) additive synthesized by reactive diisocyanate and dihydroxy naphthalene disulfonate. The second additive was a tailor made hydrophi l ic SMM (LSMM), which was manufactured incorporating poly(ethylene glycol) as end groups. Cellulose acetate (CA) membranes with and without 3 wt% CSMM or LSMM were prepared by the phase inversion technique. The membranes were characterized by static contact angle, X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive spectrometer, and atomic force microscopy. The NF filtration studies were conducted at two different operating pressures (150 and 400 psig). They consisted of pure water flux tests, sodium chloride separation tests, and individual PPCP (ppm level carbamazepine, ibuprofen, and sulfamethazine) separation tests. The long term NF performance for the removal of ibuprofen was also conducted. Significant effect of CSMM blending on the separation performance of ibuprofen for long hours operation was observed.

Electrospun nanofiber membranes consisting of poly(vinylidene fluoride) (PVDF) blended with clay nanocomposites were prepared and tested in this paper for direct contact membrane distillation (DCMD) applications. Various compositions of PVDF–clay nanocomposite nanofiber membranes (NNMs) were prepared and characterized by water contact angle, Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy and investigated for DCMD. The incorporation of clay nanocomposites increase the hydrophobicity of the membranes, which increase as the concentration of clay nanocomposite increases in the mixture. The highest water contact angle achieved was 154.20 ± 3.04°. The melting point of the PVDF–clay electrospun nanofiber membrane increases with the increasing concentration of clay indicating that the clay particles influence the crystallization process of the nanocomposite membrane. The PVDF–clay NNMs showed improved performance in DCMD applications and provide a way to prevent pore wetting in DCMD process.

Polyvinylidene fluoride (PVDF) ultrafiltration membranes were modified using a new type of hydrophilic polyurethane additive, called L2MM. During phase inversion L2MM migrates to the membrane surface and functions as both a pore former and surface modifier. L2MM improved the surface hydrophilicity and significantly increased the PVDF membrane's pure water permeation (PWP) rate. PVDF membranes were modified with two L2MMs: L2MM(PEG-600) and L2MM(PEG-200). PWP tests, contact angle measurements, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to assess the impact of L2MM type, L2MM concentration and PVDF concentration on the performance and characteristics of modified PVDF membranes. XPS analysis and contact angle measurements indicated that the L2MM migrated to the membrane surface and the contact angle decreased by up to 19%. SEM and AFM images were used to investigate the relation between surface morphology and ultimate performance. The L2MMs had a significant effect on flux; increasing the L2MM concentration improved membrane PWP fluxes up to a maximum with further increases resulting in flux decreases. Both L2MM(PEG-200) and L2MM(PEG-600) increased the final PWP flux of modified PVDF membranes up to 6.5 times that of the control membranes. Furthermore, L2MM(PEG-200) increased the 100 kDa polyethylene oxide (PEO) separation from 88 to 96% compared to the control membrane.

The present contribution provides detailed information about the development of antifouling novel thin-film-composite (TFC) membranes for mostly water purification with special emphasis on seawater desalination in particular. The novel membranes were prepared by incorporating in-situ hydrophilic surface modifying macromolecules (iLSMM) into the TFC membranes, rendering the surface of the TFC membranes significantly more hydrophilic. The prepared membranes were then subjected to long term fouling studies using model foulants, including sodium humate (SH), silica particles (SPs), and chloroform (CF) spiked in the feed NaCl solution. The biofouling effect of silver salts was also studied by incorporating some silver salts (silver citrate hydrate, SCH; silver lactate, SL; and silver nitrate, SN) simultaneously with iLSMM into the TFC membranes. Halo test was conducted with Escherichia coli to examine the antibiofouling performance of the silver incorporated TFC membranes. It can be concluded by this work that iLSMM incorporated TFC membranes have performed excellently for the desalination of salty water (3.5 wt% NaCl), especially when the solution was spiked with typical foulants such as SH, SPs, and CF. The flux reduction was reduced significantly when iLSMM was incorporated in the TFC membranes by a newly developed technique. The antimicrobial fouling intensity of the studied membrane was in the order of: SN (ring width 0.55 mm) > SL (0.27 mm) > SCH (0.19 mm).

The separation performances and physico-chemical characteristics of poly(ether sulfone) membranes were evaluated by blending of surface modifying macromolecules (SMMs). Hydrophobic SMMs (bSMM) and charged SMMs (cSMM) were synthesized and characterized. By addition of SMMs, glass transition temperature decreased and membrane pore size increased. The membrane became more hydrophobic by blending of bSMM, and became more hydrophilic after addition of cSMM. It was also demonstrated by the result of surface free energy study that the bSMM blended membrane showed the lowest solid–liquid (water) interaction by low Lifshitz–van der Waals interaction and Lewis acid (liquid)–base (solid) interaction. In contrast, cSMM blended membrane showed the highest Lewis acid–base interaction, which resulted in the highest interaction energy between membrane surface and liquid (water). It was also found from the result of differential scanning calorimeteric measurement that bound water was formed in the cSMM blended membrane.

Polyethersulfone (PES) hollow fiber membranes were fabricated using water and polyvinylpyrrolidone as additives and N-methyl pyrrolidinone as solvent. Asymmetric hollow fiber membranes were spun by the dry-wet phase inversion method. A charged surface modifying macromolecule (cSMM) was synthesized and blended into the PES dope. The modification of PES hollow fiber membranes with cSMM was evaluated via contact angle measurement, field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR-ATR) and ionic solute separation performance. Experimental results showed that pure water permeation flux was increased by surface modification with the blended cSMM, which at the same time produced higher ionic solute rejection. From the FESEM, a small increase in the thickness of the hollow fiber outer layer was noticed when the surface was modified by cSMM blending. Nevertheless, there was no significant difference in the overall membrane morphology between the membranes with and without cSMM blending, indicating that the morphology of the base polymer remained practically unchanged. On the other hand, DSC scan and FTIR analysis confirmed the miscibility of cSMM with PES and the presence of cSMM's functional group, respectively.

Modification of sulfonated poly(ether ether ketone) (SPEEK) membrane was attempted by blending three newly developed charged surface modifying macromolecules (cSMMs) having three different polyols. Sulfur content of the cSMMs was analyzed by Fourier transform infra-red spectroscopy and elemental analysis to be in the following order: PEG200-HBS > PEG400-HBS > PPG-HBS, which was also the order for their glass transition temperature (Tg). The control and modified membranes were characterized by contact angle measurement, thermal analysis, X-ray photoelectron spectroscopy, atomic force microscopy and water uptake. The modified SPEEK membrane surfaces were more hydrophilic on the top surfaces than the bottom surfaces as indicated by the water contact angle and by XPS, confirming the stronger migration of cSMM to the top than the bottom surfaces. The cSMM has migrated and formed SO3 dense layer-like on top and bottom surfaces of the modified membrane. The morphology study of the membrane surfaces showed that the nodule size and surface roughness has also influenced the water uptake, apart from the additional SO3 group. The modified membranes were tested for methanol permeability and proton conductivity. Employing PEG200-HBS has resulted in the smallest nodule size, the lowest water uptake and the lowest methanol permeability. On the contrary, employing PPG425-HBS had the largest nodule size, the highest water uptake and the highest proton conductivity. The proton conductivity is more dependent on the capability of the membrane to sorb more water rather than the additional SO3 group introduced by the cSMM.

Two different types of hydrophobic surface modifying macromolecules (SMMs) were synthesized and characterized for fluorine content, average molecular weight and glass transition temperature. The synthesized SMMs were blended into polyetherimide (PEI) hydrophilic host polymer to form porous hydrophobic/hydrophilic composite membranes by the phase inversion method. The prepared membranes were characterized by the contact angle measurements, X-ray photoelectron spectroscopy test, gas permeation test, liquid entry pressure of water and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation (DCMD). Different parameters affecting the membrane preparation process were studied and their effects on the membrane morphology as well as on the membrane performance in clesalination by DCMD were identified. These parameters include the SMMs type, SMMs concentration, solvent type and solvent evaporation time before gelation. An attempt to link the membrane morphology to its performance in DCMD is presented. This leads to better understanding of the effect of the membrane preparation on its performance. it was found that increasing the solvent evaporation time before gelation decreased the membrane flux since smaller pore sizes were observed. The membranes with higher contact angles and fluorine contents (more hydrophobic) exhibited smaller permeate fluxes. The membranes having sponge-like structures at the hydrophilic layer exhibited higher fluxes than those having finger-like structure at the hydrophilic layer. Moreover, the results were compared to a commercial polytetrafluoroethylene (PTFE) membrane. It was observed that most of the SMMs blended PEI membranes achieved better DCMD fluxes than those of the commercial membrane. A permeate flux 55% higher than that of PTFE was achieved. For both PTFE commercial membrane and all SMMs blended PEI membranes, the NaCl separation factor was found to be higher than 99% except for the PEI membrane prepared without SMMs.

A new concept for the preparation of thin-film-composite (TFC) reverse osmosis (RO) membrane by interfacial polymerization on porous polysulfone (PS) support using novel additives is reported. Hydrophilic surface modifying macromolecules (LSMM) were synthesized both ex situ by conventional method (cLSMM), and in situ within the organic solvent of the TFC system (iLSMM). The effects of these LSMMs on the fouling of the TFC RO membranes used in the desalination processes were studied. FTIR results indicated that both cLSMM and iLSMM were present in the active layer of the TFC membranes. SEM micrographs depicted that heterogeneity of the surface increases for TFC membranes compared to the control PS membrane, and that higher concentrations of LSMM provided smoother surface. AFM characteristic data presented that the surface roughness of the skin surface increases for TFC membranes compared to the control. The RO performance results showed that the addition of the cLSMM significantly decreased the salt rejection of the membrane and slightly reduced the flux, while in the case of the iLSMM, salt rejection was improved but the flux declined at different rates for different iLSMM concentrations. The membrane prepared by the iLSMM exhibited less flux decay over an extended operational period.

Modification of sulfonated poly(ether ether ketone) (SPEEK) membrane was attempted by blending charged surface modifying macromolecule (cSMM). The modified membrane was tested for direct methanol fuel cell (DMFC) application; i.e. a SPEEK/cSMM blend membrane was compared to a SPEEK membrane and a Nafion 112 membrane for the thermal and mechanical stability, methanol permeability, and proton conductivity. Thermal and mechanical stability of the blended membrane were slightly reduced from the SPEEK membrane but still higher than the Nafion 112 membrane. The blend membrane was found to be promising for DMFC applications because of its lower methanol diffusivity (2.75 × 10 −7 cm 2 s −1 ) and higher proton conductivity (6.4 × 10 −3 S cm −1 ), than the SPEEK membrane. A plausible explanation was given for the favorable effect of cSMM blending.

A new type of hydrophilic surface modifying macromolecules (LSMMs) were synthesized by end-capping urethane prepolymer with poly(ethylene glycol)s, PEGs, of average molecular weights 400, 600, and 1000 Da and poly(propylene glycol) of a average molecular weight 425 Da. They were characterized and blended into the casting solutions of poly(ether sulfone), PES, to prepare ultra-filtration (UF) membranes by the phase inversion technique. The membranes, both pure PES and LSMM blended PES, were then characterized by contact angle (CA) measurements and UF studies using PEG and poly(ethylene oxide), PEO, solutes of different molecular weights. LSMM blended PES membranes were more hydrophilic than the PES membranes based on CA data. The molecular weight cut-off (MWCO), mean pore size (μp) with geometric standard deviation, pore size distribution, pore density, and surface porosity of the membranes were determined by using UF solutes (PEG and PEO) transport data. LSMMs created lower MWCO, lower μp, and also narrower pore size distributions of the PES UF membranes. The significant effect of LSMM blending is discussed.

A hydrophiLic Surface Modifying Macromolecule (LSMM) was synthesized, characterized, and blended into the casting solution of polyethersulfone (PES) membranes. Ultra-filtration membranes were prepared by the phase inversion technique. The membranes were then characterized by contact angle measurements and a solute transport study using poly(ethylene glycol) (PEG) and poly(ethylene oxide) (PEO) solutes of different molecular weights. Pore size and pore size distribution of the membranes were determined by using PEG and PEO separation data. The Ottawa River water was treated by the membranes. The LSMM blended PES membranes showed higher fouling resistance and long-term stability than the PES membrane without LSMM.