molecules along with aqueous phase monomer through the IP films and plays a favorable role in increasing the water flux without substantial loss of salt rejection of the resulting membrane [7, 8]. Similar DMSO, acetone can also play the significant function in lessening the solubility difference between two immiscible solutions. Kong et al.  prepared TFC NF membranes by adding co-solvent (acetone) into the organic phase to control thickness of active layer having nanopores. Mansourpanah et al.  added surfactants such as cationic cetyltrimethylammonium bromide and non-ionic Triton X-100 in an organic phase to modify the PA layer characteristics. Their results showed superior overall membrane performance and produced the membranes with the thicker PA layer due to increase in diffusion of amine monomer to the organic phase. The second class of additives, such as nanoparticles, metal salts, metal oxides and catalysts have entrapped within the PA matrix, either physically or chemically. For instance, inclusion of the nanoparticles (zeolite, silica, TiO 2 ) to prepare TFC nanomembranes offered
Abstract: The degradation and detachment of the polyamide (PA) layer in thin-filmcomposite (TFC) membranes due to chlorine based chemical cleaning and material difference of PA layer and substrate are two major bottlenecks of forward osmosis (FO) technology. In this study, a new type of FO membranes were prepared by controlling self-polymerization of dopamine (DA) in the aqueous phase and the reaction with trimesoyl chloride (TMC) during interfacialpolymerization (IP) process. These membranes were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM) and water contact angle measurements. The influence of synthesis parameters such as pH of the aqueous phase, reaction time, temperature, and monomer concentrations were systematically investigated. The optimized membrane showed enhanced structure stability in ethanol (7.1 times higher) and chlorine resistance (72.3 times higher) than the conventional Piperazine(PIP)/TMC membrane due to （ poly-dopamine ） PDA bio-adhesion and polyester groups in the membrane structure. In general, DA/TMC membranes could be an effective strategy to fabricate high-performance FO membranes with excellent structural stability and chlorine resistance.
It is also reported that the presence of additives during IP process could play a role in ﬂ uencing the morphology and properties of fabri- cated PA ﬁ lm by improving monomer solubility and diffusivity . Previous studies showed that the addition of an acid-acceptor e.g. salt of triethylamine with camphorsulfonic acid (TEACSA) in aqueous solution could speed-up reaction by removing hydrogen halide by- products formed during amide bond formation [59,62,63]. Besides enhancing substrate surface wettability, there were studies to show that sodium lauryl sulfate (SLS) or sodium dodecyl sulfate (SDS) could prevent pore collapse in PSF substrate during heat treatment process [62,63]. An attempt was also made by employing polar apro- tic solvent during interfacialpolymerization. It is proven that polar aprotic solvent was able to accelerate ﬁ lm-formation rate through expansion of miscibility between water and organic phases [63,64]. Recently, hexamethyl phosphoramide (HMPA) has been added to aqueous amine solution in order to facilitate the diffusion rate of MPD in the organic solution and create a thicker zone for IP reaction . Results indicated that the higher the HMPA concentration, the greater the degree of PA cross-linking and the thicker the PA ﬁ lm formed. Greater degree of cross-linking also led to enhancement in water ﬂ ux which can be due to the increasing surface area as a result of irregular clusters formation.
In order to analyze the surface topology of the polyamide coated membranes in detail, the membranes’ surface were scanned by the AFM. Figures 7-9 showed the AFM images as well as roughness analysis by taking a horizontal section in the image frame for samples. In the images, the brightest areas indicate the highest points of the membrane surface and the dark regions show valleys or pores. Figure 7 shows the surface AFM images of the PSF membranesprepared with various TETA concentration in the aqueous phase. It visually seems that the membranes roughness prepared with TETA is lower than that of the original PSF NF membrane. Also, decreasing roughness by increasing TETA concentration could be due to expansion of the IP reaction, possibly leading to the formation of the polyamide smoothly active layer. In this condition, decreasing the roughness might cause lower fouling. Table 3 demonstrates a decreasing trend in roughness with addition of additive. As can be seen in Figure 8, images recorded for compositemembranes confirm that SiO 2 nanoparticles were successfully coated onto the
Desalination driven by renewable energies is an attractive combination in many regions. Its feasibility and reliability are guaranteed by innumerable designs implemented and experiences gained. Nevertheless, desalination systems driven by renewable energy technologies are usually for small capacities since, in most cases, they have been built within the framework of R&D or international cooperation projects. In addition, there are very few commercial desalination systems driven by renewable energy technologies and also their capacities are limited. Only mature and efficient technologies are suitable for medium to high scale desalination. In the case of seawater desalination, wind powered ReverseOsmosis (RO) is the most efficient, mature and cost-effective technology. However, if the use of wind power is not possible in a given arid coastal location, the second option is to use solar energy (Peñate and García-Rodríguez 2012).
Casting solution for the preparation of ultrafiltration membrane support was prepared by dissolving 18% wt. of PSf and 11 % wt. PEG in NMP at the temperature of 70°C. The solution was magnetically stirred for at least one day and sonicated (Bandelin DT 255H, Germany) for 2 min to guarantee complete dissolution of polymer. The homogenous solution stayed for 1 h where its bubbles were removed. The bubble significantly influenced the membrane porosity. After that, the prepared homogeneous solution was cast using a film applicator to 200 μm clearance gap on a glass plate substrate. Temperature and relative humidity of casting environment were ~24°C and 23%, respectively. The cast film was immediately (without a gap time) immersed in a deionized water bath to complete the phase separation, where the exchange between solvent (NMP) and non- solvent (water) was induced. After complete coagulation, the membrane was transferred into a pure water bath. The bath was refreshed frequently for at least 24 h. This was done to ensure the complete removal of the residual solvent from the membrane.
Salt passage was found to be relatively insensitive to changes in MPD concentration. This suggests the forma- tion of defect-free membranes in all cases. Maximum permeate flux was exhibited near 2 w / v % MPD. As the MPD concentration was increased, the driving force for MPD diffusion into the organic phase increased. In- creased MPD concentration could, therefore, increase the barrier layer thickness and, thus, causes a lower per- meate flux. As MPD concentration decreased, layer thickness was expected to decrease, which would tend to increase flux, but the resulting layer was also ex- pected to become more dense as the molar ratio of amine/acyl chloride approached unity, which would lower flux [41, 44].
The research work was conducted in order to establish the optimum condi- tions for preparing the expanded polystyrene beads without harmful sub- stances and was aimed at the preparation of the microcapsules containing wa- ter and investigation of the effect of the water content on the expansion beha- vior of microcapsules. Microcapsules were prepared with the suspension po- lymerization method and the suspension polymerization in parallel with in- terfacial polycondensation method using the multiple emulsion (W/O)/W and adding a few additives. With increasing the crosslinking agent concentration in the suspension polymerization method, the water content increased from R = 5.8 wt% (C T = 0) to R = 8.2 wt% (C T = 4 wt%) and then, decreased to R = 7.5
nanofillers for TFN membranes fabrication may cause significant particle aggregation. This agglomeration can further negatively affect the potential antifouling abilities o f TiO: particles and result in surface defects in PA layer (Razmjou et al., 2 0 11 ). Supported technology, which relies on deposition o f TiC >2 nanoparticles on the platform o f supported nanomaterials with large surface area, is a promising and effective method for avoiding TiC >2 nanoparticles aggregation. The presence o f hydroxyl radicals enable FINTs to be directly used as a support for TiC >2 nanoparticles. It can be concluded that the unique tubular structure o f HNTs coupled with the excellent anti-fouling features o f TiC >2 have made TiC^/HNTs nanocomposites a reliable material with a bright perspective in improving the antifouling affinity o f conventional thinfilmcompositemembranes for FO applications.
Asymmetric PSf substrate was prepared via phase inversion tech- nique using a polymer dope with a PSf concentration of 15 wt.%. In order to increase the porosity, 1 wt.% PVP was added into the dope solu- tion. PVP was ﬁ rst dissolved in NMP solvent, followed by the addition of the PSf. The solution was stirred continuously until it became homoge- neous. The solution was then cast on a glass plate using a casting bar to a thickness of around 100 μ m. The cast polymer solution ﬁ lm was kept for 30 s at ambient temperature before being immersed into coagulant (water) that was kept at room temperature. After coagulation, the sub- strate membrane was washed thoroughly with DI water to remove re- sidual solvent and kept wet at 5 °C prior to use. PES and PEI substrate membranes were prepared in the same way as PSf. Those membranes were denoted as PSf, PES and PEI substrates, respectively, hereafter.
crater-like structure could be obtained [7,8]. But it is dif- ficult to be in master of the acid etching craft; and also, the textured ZnO thin-film with crater-like structure has poor performance in light trapping comparing to those with pyramid-like structure . The second method is preparation of the textured ZnO thin-film with pyramid-like structure directly by MOCVD. However, the expensive equipment and high cost as well as bad thin-film den- sity have limited its wide application . In this paper, we attempt to prepare three kinds of textured ZnO thin-films by different methods. In order to compare the light trap- ping effect of these thin-films, the solar cells’ performance using three different kinds of ZnO thin-films as a front electrode are investigated, respectively.
To report conveniently the efficiency of a RO membrane, mathematical models are required [31, 32]. These mathematical equations may be subsequently employed for convenient design of RO units . This need has conducted to the expansion of some transport models . The main goal of a transport model is to describe the membrane efficiency, habitually shown as permeation flux and separation (percentage of solute removal from feed solution), to the conditions in operation (such as pressure or feed concentration) or the driving forces (frequently pressure and concentration gradients) through some coefficients (known as phenomenological transport coefficients) which comprise the model parameters [35, 36]. The coefficients (or the parameters) have to be established from experimental information. The triumph of a model can be quantified in matter of the capacity of the model to show mathematically the information with coefficients (or parameters) that are rationally constant through the interval of working conditions. Finally, the model with the established transport coefficients can illustrate the efficiency of a membrane through a large interval of working conditions. This capacity to anticipate the efficiency is the real potential of a transport model. This can be employed, partially, to avoid the elevated costs of experimentation. Integrated with a research program in membrane manufacturing, this may conduct to better conception standards for customizing producing membranes, and joined with a process design program may conduct to a more rational scale-up for RO systems [5, 37, 38].
of Ca 2+ . The results are shown in Figure 7. This shows that flow through membranes dropped quite a bit at high Ca 2+ concentration. This confirms that Ca 2+ supports the precipitation of silicates. It is known that silicates are charged with negative charge at natural conditions of pH = 7. But addition of CaCl 2 causes the forces of repulsion to decrease and silica gel to form which plays a great role in scaling and
This paper describes a study on electrical resistivity under loading of polyaniline (PANI)/gra- phene nanocomposite powders and compacts. The composites were prepared by an in-situ inter- facial dynamic inverse emulsion polymerization technique under sonication of aniline in the presence of graphene sheets in chloroform. During polymerization the graphene nanoplatelets are coated with PANI and are well dispersed both in the polymeric suspension and then in the dried polymer matrix as evidenced by cryogenic transmission electron microscopy (Cryo-TEM) and high resolution scanning microscopy (HRSEM). The presence of graphene nanoplatelets lowers the electrical resistivity of the polyaniline by two orders of magnitude for both the powder and the compact composites as demonstrated by their electrical resistance measurements conducted un- der loading. The lowest measured electrical resistivity values were 5 Ω∙cm for 33% wt. graphene powder and 8 Ω∙cm for 41% wt. graphene compacted composites. Cyclic electrical measurements under loading showed a distinct reproducible dependence of the bulk resistivity vs. applied pres- sure. This repetition is a key component for electro-mechanical sensors. To the authors’ best knowledge, this is the first report on polymerization of aniline in presence of graphene by the in-situ interfacial dynamic inverse emulsion polymerization technique and also the first report on cyclic electrical measurements under pressure of PANI/graphene nanocomposites.
Membranes in the Tajoura RO plant used to be installed every five to seven years. The estimated number of membrane modules in each period is 594 for each row (total rows = 4). This number clearly shows that the total number of membrane modules changed in the first stage (6 inches in diameter) reached to 1188, while in the second stage (8 inches in diameter) 252 membrane modules were replaced by new ones. Figure 1 shows membrane modules as currently used in the Tajoura desalination plant. The lifespan of the Tajoura RO desalination plant is about to reach its end; therefore, urgent action is required regarding the disposal of most of the plant’s systems (intake, high pressure pumps, membranes, and all the related equipment).
Liquid wettability indicating hydrophilicity and hydrophobicity properties are influenced by chemistry, sur- face charge and surface morphology. Figure 7 shows the wettability of the plasma modified surfaces was investi- gated with measurements of contact angle before and after plasma treatment. The hydrophilicity was significantly increased for all plasma treated membranes. At 10 W, the water contact angles were found to decrease, with increasing plasma duration from 60.8 ± 5.0° for the control membrane, down to 23.5 ± 9.0° after 30 min of plasma treatment. A consistent and similar trend was also found at 50 W in contact angle measurements. Water contact angles were reduced at 50 W from 32.2 ± 9.0° to 19.4° ± 9.0 for 1 to 30 min of treatment duration. Furthermore, the water contact angles were further reduced at 80 W when compared to 10 and 50 W, down to 29.4° ± 3.0 and Figure 6. Streaming potential with increasing excitation power and plasma durations: (A) 10 W, (B) 50 W and (C) 80 W.
The synthesis and characterization of zinc sulphide via different techniques have attracted considerable attention due to their potential application prospects in thinfilm devices such as pholuminescent and electroluminescent devices and more recently as n-type window layer heterojunction solar cell¹. The II-VI group of sulphides has distinctive features of high ionicity (compared to Si, Ge and III-V compounds), large band gap, and transparency in the visible region. In this regard zinc sulphide (ZnS) deserves a special mention because of its large optical band gap, in fact, the highest (>3.6 eV) among all II-VI compound semiconductors. Accordingly, different physical and chemical techniques have been utilized to grow ZnS thin films. These include sputtering, evaporation, molecular beam epitaxy, chemical vapor deposition, atomic layer epitaxy², chemical bath deposition (CBD) 3-4 and many others. One of the relatively less
Materials: Amphotericin B was obtained from symbiotic – Gujarat; Distearoyl phosphatidyl glycerol (DSPG), Hydrogenated Soy Phosphatidyl Choline (HSPC) and Cholesterol were obtained from Avanti Polar Lipids - USA. The laboratory grade chemicals used for the work are Sucrose, Disodium succinate hexahydrate, Alpha Tocopherol, Chloroform, Methanol, Sodium hydroxide, Hydrochloric acid, Triton X-100, Acetonitrile are purchased from Merck Chemicals Pvt., Ltd. Mumbai.
Surface coating with polymers possessing hydrophilic end groups, dendritic or hyperbranched polymers, is of great interest to researchers in order to impart protein resistance to the surface of TFC membrane [21,22]. A large number of functional groups and low solution viscosity cause the hyperbranched polymers to be advantageous for various ap- plications . Nikolaeva et al.  used hydrophilic hyperbranched poly(amido amine) (PAMAM) for the surface modi ﬁ cation as represent- ed in Fig. 3. Highly reactive acid chloride groups are, therefore, used for the covalent bonding of PAMAM to the PA layer by the formation of amide linkages between TMC moieties of the PA layer and amine groups of PAMAM molecules. The modi ﬁ cation is accomplished by spraying a 10 wt.% solution of PAMAM onto the PA surface of using either metha- nol (PAMAM1) or water (PAMAM2) as solvent. In comparison to the unmodi ﬁ ed membranes, both modi ﬁ cations led to a signi ﬁ cant increase in water ﬂ ux which is attributed to the suppression of subsequent cross- linking during the ﬁ nal curing step. In view of salt rejection and protein adsorption, the use of water (PAMAM2) has been found to be bene ﬁ cial over the use of methanol (PAMAM1). This is primarily due to the forma- tion of an additional highly hydrophilic PAMAM layer, which can be rec- ognized as a hydrogel layer when in contact with water. Additionally, PAMAM can be synthesized in a simple one-pot polymerization and is also easily puri ﬁ ed, making it a low cost material .