Feed Solution Concentration Research Articles

Thermolytic osmotic heat engine for low-grade heat harvesting: Thermodynamic investigation and potential application exploration

The osmotic heat engine is a promising technology for harvesting low-grade heat from different heat sources. However, a better understanding of the system performance, thermodynamic efficiencies, and suitable application circumstances (type of heat sources, system energy generation capacity, etc.) is needed before the transition can be made from conceptual design to practice. Firstly, the energy efficiency (ƞth) and exergy efficiency (ƞX) of a thermolytic osmotic heat engine (NH4HCO3 solution as the working fluid) were investigated in this study. It was found that the osmotic heat engine performs better when the operating temperature (heat source temperature) is lower (323 K). Additionally, a higher draw solution concentration and a lower feed solution concentration can increase both ƞX and ƞth. Subsequently, the energy return on investment with either low-grade industrial waste heat or solar thermal energy acting as the heat source was calculated. It was found that different energy return on investment values can be obtained with different heat sources. The results show that when industrial waste heat is used as the heat source, a much higher energy return on investment value (approximately 55) can be obtained. This finding indicates that it is suitable to generate electricity from industrial waste heat using the osmotic heat engine. When solar thermal energy is used as the heat source the energy return on investment value is 1.3–2.2 because there is a large amount of embodied energy in the flat-plate solar collector. This study represents a step forward towards the practical application of the osmotic heat engine.

Experimental investigation on the performance of series control multi-stage reverse electrodialysis

Compared with the single-stage reverse electrodialysis, multi-stage reverse electrodialysis (MSRED) is superior for reverse electrodialysis heat engine (REDHE) because it can harvest more salinity gradient energy (SGE). Generally, there are two kinds of MSRED systems, i.e., individual control MSRED system and serial control MSRED system. And the series system is more practical compared with the other one. In this paper, influences of relevant parameters on the performance of the series system were investigated experimentally. The results demonstrated that on the premise of assuring efficiency of the MSRED harvesting SGE, to increase current density might have a negative impact on the performance of the MSRED due to the phenomenon of electrodialysis. Moreover, low feed solution velocity was more suitable for REDHE since less RED stacks were employed to reduce capital input and higher efficiencies of the MSRED and even the REDHE could be reached. Besides, to increase the initial molarity of high concentration feed solution was able to improve the performance of the MSRED except for its energy efficiency which decreased. Finally, to decrease the initial molarity of low concentration feed solution could improve all performance indicators of the MSRED.

Mechanistic investigation of facilitated transport of gold(III) from HCl media using ionic liquid Cyphos IL102 as carrier across a supported liquid membrane

The transport of gold(III) across a supported liquid membrane containing the ionic liquid Cyphos IL102 (trihexyl(tetradecyl)phosphonium bromide) in Solvesso 100 has been investigated. The investigation was carried out under various experimental variables affecting to the transport process: stirring speed in the aqueous feed solution, HCl and gold(III) concentrations in this same phase, and carrier concentration in the membrane phase. The transport of gold(III) was compared against the transport of Fe(III), Cu(II), and Ni(II) from aqueous solutions containing the four elements, whereas the performance of Cyphos IL102 was compared, with respect to the gold transport, against other potential carriers for gold(III) from this acidic medium. Gold can be recovered in the strip solution as zero valent gold nanoparticles.

Nanofiltration membranes for toxic lead removal: contribution of various mass transfer mechanisms on membrane performance

ABSTRACT The performance of nanofiltration membrane process for lead retention has been modelled by the modified Donnan steric pore-flow model (DSPM). The model predictions have been used to analyse the contribution of diffusive, convective and electrical flux on ion retention. A good agreement was found between the experimental and modelling data at various operating conditions. The influence of various process parameters, such as the permeation flux, feed solution concentration and cross-velocity, on lead (Pb) ion retention, was investigated. Maximum lead ion rejection was 93.8% at permeate flux of 1.25 * 10−5 m/s. It was found that the lead retention increases initially with permeate flux and then decreases with further increase in permeate flux due to the developed concentration polarisation layer. Furthermore, the rejection drops by ∼ 80% when the uncharged membrane is used, revealing the important role of electrical potential on the performance of the nanofiltration membrane. Finally, it is confirmed that the diffusion phenomenon is the dominant mechanism for ion transfer through the membrane.

Preparation of PGX-dried gum arabic and its loading with coQ10 by adsorptive precipitation

The Pressurized Gas eXpanded (PGX) liquid technology was developed for simultaneously drying and purifying high molecular weight biopolymers, resulting in nano/micro-sized powders with large surface areas that can be loaded with various bioactives. The preparation of PGX-dried gum arabic (GA) and its loading by adsorptive precipitation with coenzyme Q10 (coQ10) was investigated in a two-step process. In step one, the effects of feed solution concentration, flow rates and flow rate ratios on the PGX-processed GA were studied. Low flow rates and high ratios resulted in larger (up to 65 m2/g) surface areas. In the second step, the impact of different recirculation flow rates and pressurization rates on the coQ10 loading was tested. Only an increased pressurization rate (4.5 vs. 1.5 MPa/min) showed an effect, increasing the coQ10 loading from 0.6 to 2.0% w/w. PGX drying followed by adsorptive precipitation shows great potential for the development of bioactive delivery systems.

Influence of osmotic mediation on permeation of water in reverse osmosis: Experimental and numerical analysis

Osmotically mediated reverse osmosis (RO), whose concept is to lower the osmotic pressure difference (Δπ) across the membrane by supplying a “mediate” solution of low or equal concentration (relative to feed solution concentration) in the permeate side, has been recently suggested as a viable way to treat hypersaline brines. However, most of the studies on the osmotically mediated RO process have focused on numerical analyses or simulation. Accordingly, we experimentally delved deeper into the permeation of water through the membrane and numerically analyzed this permeation for the process. When Δπ across the membrane was mediated in the bulk phase for the feed solution of 0.2 to 1.2 M, the water flux significantly decreased with the feed solution concentration. Specifically, for the feed solutions of 0.6 and 1.2 M, the water fluxes of 22.1 and 5.76 L m-2 h-1 were obtained at ΔP of 40 bar and Δπ of 0 bar in the bulk phase, respectively. Numerical results showed that even when Δπ was mediated in the bulk phase, effective osmotic pressure difference (Δπeff) for each concentration increased with ΔP increase and increased further with the feed solution concentration. Nevertheless, the osmotically mediated RO process can be regarded as hydraulic dilution process. By virtue of this process, the high-pressure single stage RO process may be replaced by a moderate-pressure two-stage RO process for low-energy process.

Application of PVA-b-NaY zeolite mixture membranes in pervaporation method

Abstract Pervaporation, an economical, energy-saving and eco-friendly membrane process for separating liquid mixtures, has been considered as a promising candidate for the separation of azeotropic mixtures that are difficult to separate using classical processes. In this study, isopropyl alcohol/water azeotropic mixtures were separated by the pervaporation method using poly(vinyl alcohol)-blended-NaY zeolite (PVA-b-NaY) membranes. For this purpose, different yields of PVA/NaY mixtures were prepared and characterized by using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), water contact angle and atomic force microscopy (AFM). The effect of different parameters, such as PVA/NaY yield, membrane thickness, feed solution concentration and temperature, on the pervaporation performance was examined, and the optimum conditions were determined. The best separation factor was determined to be 2690.4 at a flux of 0.00512 kg/m2.h and an IPA concentration of 87.7%. Based on the research findings, it can be said that PVA-b-NaY membranes are very effective in separating IPA and water using the pervaporation method.

Bentazon removal from aqueous solution by reverse osmosis; optimization of effective parameters using response surface methodology

Although bentazon is widely used as an agricultural herbicide, it is harmful to humans and poses many environmental threats. This study focused on the treatment of wastewater contaminated with bentazon pesticides using membrane technology. In this regard, low-pressure reverse osmosis (RO) was employed as it has already been used in the removal of other micro-pollutants. The effects of process variables on water flux and bentazon rejection were studied: temperature, pressure, and bentazon feed concentration. Based on central composite design (CCD), the quadratic model was engaged to correlate the process variables with the water flux and the bentazon removal responses. The obtained results showed that the bentazon rejection increased by enhancing the pressure while it decreased at higher feed solution concentration. However, with increasing temperature, the amount of bentazon removal was reduced. A bentazon rejection efficiency of 100 % could be achieved under optimum conditions (i.e., the temperature of 29.8 ℃ and hydrostatic pressure of 12.6 bar for a feed solution concentration of 66.9 mg/L). Therefore, reverse osmosis can effectively remove bentazon.

Tangential flow microfluidics for the capture and release of nanoparticles and extracellular vesicles on conventional and ultrathin membranes.

Membranes have been used extensively for the purification and separation of biological species. A persistent challenge is the purification of species from concentrated feed solutions such as extracellular vesicles (EVs) from biological fluids. We investigated a new method to isolate micro- and nano-scale species termed tangential flow for analyte capture (TFAC), which is an extension of traditional tangential flow filtration (TFF). Initially, EV purification from plasma on ultrathin nanomembranes was compared between both normal flow filtration (NFF) and TFAC. NFF resulted in rapid formation of a protein cake which completely obscured any captured EVs and also prevented further transport across the membrane. On the other hand, TFAC showed capture of CD63 positive small EVs (sEVs) with minimal contamination. We explored the use of TFAC to capture target species over membrane pores, wash and then release in a physical process that does not rely upon affinity or chemical interactions. This process of TFAC was studied with model particles on both ultrathin nanomembranes and conventional thickness membranes (polycarbonate track-etch). Successful capture and release of model particles was observed using both membranes. Ultrathin nanomembranes showed higher efficiency of capture and release with significantly lower pressures indicating that ultrathin nanomembranes are well-suited for TFAC of delicate nanoscale particles such as EVs.

Competition of mixed divalent ions through supported liquid membranes: Co-ion and concentration effects on permeability

Zn2+, Cu2+ and Ni2+ permeabilities through supported liquid membranes (SLMs) were determined experimentally from single, binary, and ternary ionic mixtures. Microporous polypropylene membrane was used as the frame to retain isopar-L solvent and di (2-ethylhexyl) phosphoric acid (D2EHPA) carrier. Sulfuric acid solution was used as a strip (receiving) solution. The ion permeability values were in the 10−7-10−6 cm2 s−1 range and increased with the concentrations of D2EHPA in isopar-L and the stripping sulfuric acid. The ion ideal selectivity ranged from 1.05 (Zn/Cu) to 8.40 (Zn/Ni), depending on the feed concentration. The single ion permeability was significantly higher than the binary mixtures, probably due to ion competition with D2EHPA carrier molecules. High selectivity was achieved using ternary mixtures: Zn2+ was the fast-permeating species due to preferential sorption with D2EHPA. Separating Zn2+ from Cu2+ and/or Ni2+ mixtures was most efficient with high D2EHPA concentration, concentrated H2SO4 strip solution, concentrated feed solution, and from multiple ionic mixes.

Mass Transfer Study in Brine Water Treatment by Forward Osmosis Process

Forward osmosis (FO) is an energy-saving separation process that can be used in desalination applications. This work investigated the effect of mass transfer phenomenon on the FO desalination process. For this purpose, the water flux was studied through a bench scale system using a flat sheet FO membrane and feeds with various salinity. Then, the mass transfer resistances, which appear in the form of concentration polarization (CP) for the FO process, were evaluated qualitatively and quantitatively, using the collected experimental data and by employing a mathematical model. The results indicated that the increase in feed salinity led to a decrease in water flux due to the counteracted part of the draw solution osmotic pressure, thus leading to a lower effective osmotic pressure and driving force. Also, according to the results, there was a significant difference between the theoretical and experimental fluxes, indicating the influence of the mass transfer effects on the osmotic pressure drop. The modeling results showed that the internal concentration polarization (ICP) still held more contribution to the osmotic pressure loss. Furthermore, it was observed that as the feed solution concentration increased, both the ICP and dilutive external concentration polarization (DECP) decreased, whereas the concentrative ECP (CECP) intensified. Therefore, increasing the CECP led to a significant reduction in the effective osmotic pressure. In addition, increasing the draw solution concentration was accompanied by a much more severe ICP that limited the enhancement of effective flux.

Design, performance characterization and hydrodynamic modeling of intermeshed spinning basket membrane (ISBM) module

Dynamic Shear Enhanced (DSE) membrane modules have been established as effective replacement of classical cross flow devices, especially in treatment of high fouling feed solutions. Nevertheless, even with latest modifications, no DSE module is able to regenerate permeate flux without intermittent chemical/hydrodynamic membrane cleaning. In this article, we have presented the design, performance characterization and primary CFD modeling of a DSE module with rapid on-line membrane washing facility along with high permeate production rate even in treatment of extremely fouling feed solution. Present device, named as Intermeshed Spinning Basket Membrane (ISBM) module, consists of two intermeshed counter rotating baskets, with flat sheet rectangular membranes fitted on alternate sides of their radial arms. Maximum permeate flux was evaluated to be as high as 2.4 × 10−4 m3 m−2 s−1 at moderate transmembrane pressure and rotational speed (588 kPa and 52.36 rad s−1). High rate of flux regeneration (>85% of start-up flux), even after 11 h of filtration run and moderately high flux (2.6 × 10−6 m3 m−2 s−1) for concentrated feed solution (10.5 kg m−3) clearly establish the novelty of present design. Irrespective of low packing density, outcomes of this investigation suggests viable commercial use of ISBM module in treatment of extremely fouling feed solutions, for which other standard membrane units are apprehended to be inoperative.

Mining phosphorus from anaerobically treated dairy manure by forward osmosis membrane

We investigated the effect of draw solution type on the forward osmosis (FO) performance for enriching nutrients from anaerobically treated dairy manure (ATDM) followed by chemical precipitation for phosphorus recovery as struvite crystal. The FO membrane significantly rejected COD (>97%) and phosphate (>98%) whereas there was only 70%–73% and 73%–76% rejection of ammonia-nitrogen and total nitrogen, respectively. The draw solution type had little impact on the retention of the aforementioned wastewater constituents by the FO membrane. At 60% water recovery, a water flux decline of 82%–96% was observed due to increasing contaminant concentration in the concentrated feed solution. Water flux decline was less for MgCl2 than EDTA-2Na and NaCl as draw solutes. On the contrary, the reverse solute flux was higher for NaCl than MgCl2, which in turn was higher than EDTA-2Na. Pre-concentration of ATDM by FO facilitated struvite precipitation. MgCl2 as the draw solute provided a higher purity of struvite than EDTA-2Na and NaCl. This is because when MgCl2 was used as the draw solute, the reverse salt flux of magnesium to the concentrated ATDM provided favourable conditions for struvite crystal formation. This study demonstrates the technical feasibility of phosphorus recovery from ATDM using the FO process.

Chromium removal and water recycling from electroplating wastewater through direct osmosis: Modeling and optimization by response surface methodology

Background: Considering the carcinogenic effects of heavy metals, such as chromium, it is essential to remove these elements from water and wastewater. Direct osmosis is a new membrane technology, which can be a proper alternative to conventional chromium removal processes. Methods: The wastewater samples were collected from an electroplating unit, located in Alborz industrial city, Qazvin, Iran. Magnesium chloride was used as the draw solution, and a semipermeable membrane (Aquaporin) was used in this study. The experiments were designed, using response surface methodology (RSM) and central composite design (CCD) with draw solution concentration (0.5- 1.5 M), feed solution concentration (4-12 mg/L), and experiment time (30-90 minutes) as variable factors. The chromium concentration and water flux were also measured, based on atomic absorption spectrophotometry and water flux equation, respectively. Results: Direct osmosis was highly efficient in chromium removal and water recycling. Water flux and chromium removal efficiency were 15.6 LMH and 85.58%, respectively, under optimal conditions (draw solution = 1.27 mol/L, feed solution = 4 mg/L, and experiment time = 90 min). In terms of validity, the results predicted by the quadratic polynomial model were in good agreement with the responses reported in the laboratory. Conclusion: In direct osmosis, the use of magnesium chloride as the draw solution resulted in the acceptable chromium removal from electroplating wastewater. Using this method, chromium concentration in wastewater reduced to a level lower than the discharge standards, established by Iran’s Department of Environment.

Development of A Novel Corrugated Polyvinylidene difluoride Membrane via Improved Imprinting Technique for Membrane Distillation.

Membrane distillation (MD) is an attractive technology for desalination, mainly because its performance that is almost independent of feed solute concentration as opposed to the reverse osmosis process. However, its widespread application is still limited by the low water flux, low wetting resistance and high scaling vulnerability. This study focuses on addressing those limitations by developing a novel corrugated polyvinylidene difluoride (PVDF) membrane via an improved imprinting technique for MD. Corrugations on the membrane surface are designed to offer an effective surface area and at the same time act as a turbulence promoter to induce hydrodynamic by reducing temperature polarization. Results show that imprinting of spacer could help to induce surface corrugation. Pore defect could be minimized by employing a dual layer membrane. In short term run experiment, the corrugated membrane shows a flux of 23.1 Lm−2h−1 and a salt rejection of >99%, higher than the referenced flat membrane (flux of 18.0 Lm−2h−1 and similar rejection). The flux advantage can be ascribed by the larger effective surface area of the membrane coupled with larger pore size. The flux advantage could be maintained in the long-term operation of 50 h at a value of 8.6 Lm−2h−1. However, the flux performance slightly deteriorates over time mainly due to wetting and scaling. An attempt to overcome this limitation should be a focus of the future study, especially by exploring the role of cross-flow velocity in combination with the corrugated surface in inducing local mixing and enhancing system performance.

TREATMENT OF PRODUCED WATER FROM CRUDE OIL DESALTER BY COMPOSITE POLYAMIDE RO MEMBRANE

Produced water generated from oil refinery desalting unit requires proper treatment to adhere to stringent regulations before discharging or recycling into the processing area. In this research, desalter’s produced water from PP(M)SB (PETRONAS Penapisan (Melaka) Sdn. Bhd.) was treated via AFC99 tubular thin film composite polyamide RO membrane and were investigated concerning TMP, feed pH and feed-solution concentration. The experimental results indicated that AFC99 membrane removed 100% of TSS and salinity, and more than 95% of COD, salts ions and TDS. This work shows that the RO membrane was feasible and technically viable to be used for optimum salts and contaminants removal from produced water of the desalting unit. Besides, the treated water (permeate) fulfills the watering standards and can be used for recycling and other purposes.
 Keywords: produced water, reverse osmosis, polyamide membrane, operating conditions, watering standards

Simple modeling of Donnan separation processes: single and multicomponent feed solutions

ABSTRACTSimplified engineering models are presented, characterizing Donnan dialysis separations of a single and multicomponent feed solutions by an overall transport coefficient combining mass transfer resistance and membrane diffusion resistance. Full verification of the predictions of the derived models was obtained from experimental data measured at various Reynolds numbers and feed solution concentrations using a NaCl stripping solution. Permeating target ions from single component feed solutions consisted of H2PO4−, NO3−, and HCO3−. Dual component permeation was from feed solutions of the ion pairs H2PO4−/NO3−, and NO3−/HCO3−. Permeation of all ions except the H2PO4− ion was found to be mass transfer controlled.

Inorganic coagulant induced gypsum scaling in nanofiltration process: Effects of coagulant concentration, coagulant conditioning time and fouling strategies

Nanofiltration is routinely applied as an advanced water treatment technology after conventional water treatment. However, the residual coagulant after coagulation process may affect the nanofiltration process and to our best of knowledge, few studies focused on this phenomenon. To address such issues, ferric and aluminum ions were adopted as the model coagulant, and the influences of coagulant concentrations, coagulant conditioning time and fouling strategies on gypsum scaling were systematically investigated. The results indicated that coagulant conditioned on the membrane surface could improve membrane flux, enhance scaling, and increase the conductivity of permeate. The contents of coagulant accumulated on the membrane surface gradually increased with its increasing concentration in feed solution and extending conditioning time, resulting in severer scaling and flux decline. Interestingly, the formation of heterogeneous scaling layer will contribute to membrane fouling alleviation and prevent the further flux decline regardless of the ongoing increase of coagulant concentrations in the feed water as well as on the membrane surface. As a result, a critical value of coagulant concentrations in the feed water was obtained in present conditions. Furthermore, it's found that successive fouling strategy could lead to less gypsum scaling but severer flux decline, compared to simultaneous fouling strategy. Both the scaling quantity and scaling morphologies conferred significant influence on the flux decline. It is suggested that the concentrations of coagulant should be strictly controlled prior to nanofiltration process, especially with practical relevance for the applications of it in treating the water rich in calcium ions and sulfate anions.

Photocatalytic decolorization of Basic Blue 41 using TiO2-Fe3O4-bentonite coating applied to ceramic in continuous system

Photocatalytic degradation/decolorization of Basic Blue 41 dye assisted by UV radiation has been studied over TiO2-Fe3O4 supported by bentonite. In this experiment, photocatalytic decolorization process was performed continuously; where dye feed solution was supplied to a coated-ceramic vessel. The influence of the initial concentration, pH, and flow rate of the dye feed solution on the degradation efficiency process was examined in this study. The results showed that the increase in the dye concentration and flow rate reduces decolorization efficiency. The highest decolorization efficiency was at pH of 5.5. The kinetic study of this photo-decolorization indicated that under the experimental condition, the photocatalytic kinetic process followed first-order kinetics on the basis of Langmuir–Hinshelwood heterogeneous reaction mechanism, where the reaction rate constant, namely kr, is 0.7707 and the adsorption rate constant, namely K, is 0.01298.

An experimental study on sterile filtration of fluorescently labeled nanoparticles – the importance of surfactant concentration

Nanoparticles have attracted considerable attention in the field of separation science, especially for filtration studies designed to evaluate membrane integrity, investigate membrane pore-size properties, and model membrane transport. A common reason for studying nanoparticle filtration is their potential to be used as surrogates for the various types of viruses in water treatment and bioprocessing applications. Although the effect of adding surfactants to stabilize nanoparticle suspension has been explored for a number of different applications, there is significant variation in the amounts and types of surfactants used in those studies. In this study, we used three different sizes (59, 188, and 490 nm) of spherical fluorescent polystyrene nanoparticles (PNPs) – the two smaller sizes were chosen to mimic the width and length of Rhabdovirus, a bullet-shaped enveloped virus that is currently being studied as bio-therapeutic for the treatment of cancer. The PNPs were suspended in solutions with varying concentrations of the nonionic surfactant Tween 20 (0.0005% to 0.1% (v/v) in carbonate buffer solution) and were tested in constant-flux filtration studies using two commercial microfiltration membranes (Durapore PVDF and MiniSart PES) with 0.22 µm pore size ratings. Our results clearly show that the transmission behavior of PNPs is critically dependent on the surfactant concentration in the buffer feed solution. The results could only be partially explained by interparticle interactions as we also observed major differences in the performances of the two microfiltration membranes.