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Acid whey is a by-product of cheese and yoghurt manufacture. The protein and lactose within acid whey can be recovered using nanofiltration and electrodialysis, but this leaves a waste stream that is a mixture of salts and lactic acid. To further add value to the acid whey treatment process, the possibility of recovering this lactic acid was investigated using either low energy reverse osmosis membranes or an electrodialysis process. Partial separation between lactic acid and potassium chloride was achieved at low applied pressures and feed pH in the reverse osmosis process, as a greater permeation of potassium chloride was observed under these conditions. Furthermore, lactic acid retention was enhanced by operating at lower temperature. Partial separation between lactic acid and potassium chloride was also achieved in the electrodialysis process. However, the observed losses in lactic acid increased with the addition of sodium chloride to the feed solution. This indicates that the separation becomes more challenging as the complexity of the feed solution increases. Neither process was able to achieve sufficient separation to avoid the use of further purification processes.

This work presents the impact of propane and n-butane on the CO2/CH4 separation performance of both cellulose diacetate (CDA) and cellulose triacetate (CTA) membranes by exposing both pristine membranes to either propane (400 kPa) or n-butane (200 kPa) at room temperature (22 ± 2 °C) for 4 weeks. The propane and n-butane sorption isotherms in both membranes were anomalous at 35 °C. X-ray diffraction (XRD) results indicated that the crystalline nature of both polymers was altered by this exposure, although dynamic scanning calorimetry (DSC) did not detect a significant change in the overall crystallinity. Positron Annihilation Lifetime Spectroscopy (PALS) revealed that the average pore size of the CTA polymer and the number of free volume elements of both membranes also increased, even though the sorption uptake was less than 2 wt%. CO2 and CH4 permeabilities at 35 °C were essentially unaffected by the propane or n-butane exposure, indicating that while the crystalline regions of the polymer were affected, plasticization of the glassy amorphous region did not occur. There was a slight decrease in CH4 permeability for the CDA membrane after n-butane exposure, consistent with a slight decline in the CH4 solubility at this feed pressure. The propane and n-butane permeabilities were 0.029 Barrer at 300 kPa and 0.019 Barrer at 125 kPa for the fresh CTA membrane, but these fell significantly after long term exposure to these gases, possibly due to penetrant clustering.

The feasibility of using electrodialysis with bipolar membranes (EDBM), combined with monovalent selective anion exchange membranes was investigated to purify organic acids from fermentation broths or wastewater streams. A simulated beet molasses feed containing a mixture of monobasic lactic acid and polybasic citric acid was used for this purpose. The impact of the feed pH, the configuration of the membrane stack and the voltage applied on the selectivity of the process was investigated. At a pH of 9–10 and an electric field intensity of 9 V/cm, a lactic acid product with a purity of at least 97% can be obtained by using both two chamber (BP-A) and three chamber (BP-A-C) configurations with the monovalent selective membrane. When using the BP-A configuration, the hydroxide ions generated by the bipolar membrane compete with the lactate anions to move into the acid solution and so the energy efficiency is lower than with the BP-A-C configuration. To mimic a multiple pass process and increase the lactic acid concentration of the final product, experiments were performed across a range of volume ratios between the feed and acid solutions. As this ratio is varied, the purity of lactic acid produced remains higher than 95% while the energy consumption is essentially unaffected. Due to the osmotic flow of water during experiments, the highest lactic acid concentration that can be achieved is limited to 153 g/L at a volume ratio (VA: VF) of 1:10.

The authors regret that in the original version, the y-axes of Figures 5 and 8 were labelled incorrectly. The corrected figures are presented here. The authors would like to apologise for any inconvenience caused.

This work investigates the separation performance of a commercial carbonized polyimide hollow fiber membrane module for post-combustion CO2 capture applications. In particular, the resilience to water and sulfur and nitrogen oxides (SOx and NOx) as gas impurities was examined. The membrane exhibited a CO2 permeance of 660 Gas Permeance Units (GPU) and a CO2/N2 permselectivity of 20 at 50 °C when the permeate side was controlled at 0.2 bar absolute pressure. With an increase in water vapor in the feed stream, this CO2 permeance decreased slightly, while the CO2/N2 selectivity increased slightly, due to the combination of competitive sorption and concentration polarization. The water vapor permeance was high, which made accurate measurement difficult due to the concentration polarization but a value of 1090 ± 200 GPU was recorded. The membrane was then examined under three mixed gas conditions (i.e. SO2/CO2/O2/N2, NO/CO2/N2, and NO/NO2/N2) for a time frame of 30 days. The permeances of SO2, O2, NO, and NO2 were 650 ± 50, 155 ± 5, 125 ± 10, and 70 ± 5 GPU at 30 °C, respectively. All of these minor components had a marginal impact on the membrane separation performance during the testing period, indicating strong commercial potential. The higher permeance of SO2 and NO relative to nitrogen meant that these penetrants were concentrated in the permeate stream, which might lead to issues with downstream corrosion in a humid environment. Conversely, the permeance of NO2 was low.

The co-ion and counter-ion sorption of monovalent (Na+, K+, Cl- and NO3-) and divalent ions (Ca2+ and SO42-) in commercial Neosepta ion exchange membranes were systemically studied in both single and binary salt systems. The new generation of Neosepta cation exchange membrane (CSE) showed a significant difference in water uptake and co-ion sorption compared to the earlier generation (CMX). Use of the Manning model confirmed that there were significant differences between these membranes, with the estimated value of the Manning parameter changing from 1.0 ± 0.1 for CMX to 2.8 ± 0.5 for CSE. There were fewer differences between the two Neosepta anion exchange membranes, AMX and ASE. In single salt solutions, potassium sorbed most strongly into the cation exchange membranes, but in binary salt mixtures, calcium dominated due to Donnan exclusion at low concentrations. While these trends were expected, the sorption behaviour in the anion exchange membranes was more complex. The water uptake of both AMX and ASE was shown to be the greatest in Na2SO4 solutions. This strong water uptake was reflected in strong sorption of sulphate ions in a single salt solution. Conversely, in a binary salt mixture with NaCl, sulphate sorption fell significantly at higher concentrations. This was possibly caused by ion pairing within the solution, as well as the strongly hydrophobic nature of styrene in the charged polymer. Water uptake was lowest in NaNO3 solutions, even though sorption of the nitrate ion was comparable to that of chloride in these single salt solutions. In the binary mixture, nitrate was absorbed more strongly than chloride. These results could be due to the low surface charge density of this ion allowing it to bond more strongly with the hydrophobic polymeric backbone at the exclusion of water and other ions.

Large quantities of salty whey are produced during cheese manufacturing, posing an environmental problem. Here the feasibility of electrodialysis with bipolar membranes (EDBM) is evaluated for the first time as a mechanism to transform this saline effluent into sodium hydroxide and hydrochloric acid for reuse within the factory. This work also seeks to find the maximum acid and base concentration that can be achieved. For a pure sodium chloride solution, maximum acid/base concentrations of 3.6 ± 0.2 mol/L and 3.0 ± 0.3 mol/L are achieved using a stack of ten membranes including four bipolar membranes. The effects of proton leakage and water migration limit the generation of higher concentrations. The presence of calcium phosphate also has a negative effect on the EDBM performance, suggesting that pretreatment to remove this impurity is needed. In industrial practice, this pretreatment could be achieved by recycling around 9% of the base produced to precipitate these salts. The use of a partially cyclic operation allows 99% demineralization of pretreated salty whey, with high purity acid/base solutions of concentration near 3.5 mol/L. This work demonstrates EDBM as an effective process for transforming salty whey into chemicals for clean in place and ion exchange resin regeneration.

Isolation of high value minor proteins such as lactoferrin and immunoglobulins from crude dairy streams is a major challenge for the dairy industry. Here we investigate an electrodialysis with filtration membrane (EDFM) approach to separate lactoferrin (LF) and immunoglobulins (Ig) from other dairy proteins. A polyvinyl alcohol (PVA) membrane is prepared using phase inversion in a coagulation bath with 80% ethanol to serve as the filtration membrane. A range of treatment times and two electric field strengths (38.5 and 77 V/cm) were then investigated within the electrical cell. The results show that the filtration membrane prepared in-house can offer strong rejection for LF and Ig while allowing a high flux of other proteins. The separation of LF and Ig from a simulated whey solution can be achieved. The use of a partially demineralised whey reduces protein loss, but there is a tradeoff between the energy consumption and the protein removal rate as the extent of this demineralisation is increased.

Acid whey presents a major disposal issue for the dairy industry due to its high lactic acid and mineral concentrations. In this work, the feasibility of using membrane technology to treat acid whey to produce high quality whey powder was demonstrated at pilot scale. Three process combinations were tested, namely, (1) ultrafiltration and electrodialysis; (2) ultrafiltration, nanofiltration, and electrodialysis; and (3) ultrafiltration, dia-nanofiltration, and electrodialysis. All three combinations were successful in reducing the levels of lactic acid and minerals in acid whey. However, the lowest ratio between lactic acid and lactose (0.017 g lactic acid/g of lactose) was obtained with the process that utilized dia-nanofiltration. The energy required for the electrodialysis of the ultrafiltration permeate and dia-nanofiltration retentate were comparable (7.5 and 7.8 kWh/tonne of feed, respectively). However, the dia-nanofiltration retentate was at least 3.5 times more concentrated than the ultrafiltration permeate, thus reducing the annual energy consumption and capital investment of the electrodialysis unit. The product of the nanofiltration and electrodialysis process was successfully dried to produce a powder with an ash and moisture content of 4% and 2.5%, respectively.

In this study, the sorption behaviour and conductivity of two anion exchange membranes (AR103 and AR204) equilibrated with sodium acetate and sodium lactate solutions are studied across a range of concentrations and pH values. The results indicate that the dissociation equilibria of the organic acids differ between the membrane phase and the external solution. There are significant concentrations of the neutral organic acid in the membranes at pH 6.5 even though the dissociation is virtually complete in the external solution. The concentration of this neutral acid increases as the pH is lowered, leading to a reduction in membrane conductivity. The diffusion coefficients of acetate and lactate ions in these membranes are determined from conductivity data. The results show that these diffusion coefficients are relatively constant but decrease slightly with an increase of external solution concentration due to osmotic deswelling. The diffusion coefficient of the acetate anion decreases as the pH falls, possibly due to dimer formation. Models extended from Manning's condensation theory have been utilized in the prediction of the co-ion concentrations within the membrane and the diffusion coefficients of the lactate and acetate anions. There is an excellent agreement between the experimental values of these parameters and the model predictions for the sodium lactate system but the model is unable to accurately fit the sodium acetate data.

The disposal of saline effluent in the dairy industry is subject to increasingly strict regulatory requirements. In this work, eutectic freeze crystallization (EFC) was investigated as a mechanism for the simultaneous separation of salts and ice in a typical saline effluent, namely salty whey. Experiments were conducted using salty whey samples collected from a dairy processing facility. The eutectic point of the salty whey was determined using differential scanning calorimetry and was found to be lower than that of NaCl solutions (−24 °C for salty whey vs. −21 °C for aqueous NaCl solutions). Crystallization experiments were then used to construct the phase diagram of this dairy stream under equilibrium conditions. The change in cation composition in the supernatant at the eutectic temperature was measured as a function of time and showed that pure NaCl salts and ice formed within 5 min after this temperature was reached. The energy consumption of this process was estimated to be ~120 kWh/t for salty whey, which is comparable to that for conventional thermal crystallization of brine.

This work assesses the feasibility for concentrating process streams within dairy processing facilities using commercial forward osmosis membranes; to increase their total solids concentrations before entering energy intensive unit operations including thermal evaporators and spray dryers. These streams include demineralised whey, lactose, whey protein concentrate, sweet whey and skim milk. FTSH2O cellulose acetate (CTA) and Aquaporin flat sheet membranes are used with magnesium chloride concentrations of 1.66 ± 0.12 M as the draw solution. The experimental data are fitted to conventional mathematical models for forward osmosis, further modified by considering the nonlinear relationship between osmotic pressure and solute concentration. The diffusion coefficients of magnesium chloride in 1.6 M solutions at 10 °C, 20 °C and 50 °C are obtained and reported for the first time. Minimal fouling and a significantly smaller degree of concentration polarisation was observed on the membrane surface during lactose concentration compared to the concentration of other dairy solutions, due to the absence of proteins and calcium phosphate salts. The transfer of magnesium into the concentrated products was monitored and shown to be below 100 mg per 100 g dry powder. Acid cleaning alone was not effective in recovering pure water flux, and enzyme cleaners at neutral pH were needed given the limited pH tolerance (3–8) of the CTA membranes. Total solids concentrations of the concentrated dairy streams by forward osmosis (up to 40%) exceed those which can be achieved by nanofiltration and reverse osmosis (i.e., 15–20%). This study shows that forward osmosis is an effective approach to concentrate relevant dairy streams to achieve high concentration factors (e.g. >4 for sweet whey samples) without jeopardising product quality.

Cheese whey was concentrated to a concentration factor of 2.7 in a pilot scale forward osmosis filtration system, using a commercial cellulose triacetate membrane in a spiral-wound configuration. The whey was concentrated in a batch mode, using sodium chloride as the draw solution at initial osmotic pressures of 53–75 bar. During the process, flux was shown to reduce due to the simultaneous decrease in the bulk osmotic pressure of the draw solution, increase in the bulk osmotic pressure of the whey and the effect of concentration polarisation on both sides of the membrane. The flux is known to be driven by the effective osmotic pressures of whey and the draw solution on the surface of the membrane active layer. A short-cut approach that requires minimal information in advance about the osmotic pressure of whey and the geometry of the filtration system was implemented, enabling the determination of these effective osmotic pressures. The results obtained were shown to be in agreement with the fundamental forward osmosis flux model. The short-cut approach can be utilised for estimating effective osmotic pressures of other liquid food streams to be concentrated by forward osmosis, without the need of external measurements.

Skim milk was concentrated at 10 °C using forward osmosis (FO), reverse osmosis (RO) and pressure-assisted forward osmosis (PAFO). A pressure of 40 bar, in the form of draw solution osmotic pressure (FO and PAFO modes) or transmembrane hydraulic pressure (RO mode) was applied; an additional hydraulic pressure of 2 bar was applied in the PAFO mode. More severe protein fouling was observed in RO, followed by PAFO and then FO. This was credited to the difference in the initial permeate flux, induced by the different effective driving pressures, with RO having a greater deviation of the initial flux from the critical flux value. The critical flux was determined for the FO and RO modes using a step-wise increase of draw solution osmotic pressure or hydraulic pressure, at a constant milk solids content. The critical flux was between 5.4 L/m2h (1.5 × 10−6 m3/m2s) and 7.2 L/m2h (2 × 10−6 m3/m2s) for both the FO and RO modes at a cross flow velocity of 0.2 m/s. The similarities in the critical flux for FO and RO suggests that the critical flux does not depend on the nature of pressure applied on the system (hydraulic or osmotic). Therefore, when operated at the same flux and crossflow velocity, FO would not fundamentally provide a lower fouling environment compared to RO. An increase of the solids content from 8.7% to 17.3% caused a reduction in the critical flux from 5.4 L/m2h to 3.1 L/m2h (8.5 × 10−7 m3/m2s).

The effect of organic fouling on both capacitive deionisation (CDI) and membrane capacitive deionisation (MCDI) was studied using two model foulants, the sodium salt of alginic acid and humic acid. Fouling of the activated carbon electrodes in the CDI cell was significant. The salt adsorption fell to 75% and the charge efficiency to 90% of their initial values after 18 cycles of operation with 0.5 mM CaCl 2 and 60 mg L −1 of sodium alginate. Similarly, the salt adsorption fell to 70% and the charge efficiency to 65% of their initial values after 18 cycles of operation with 60 mg L −1 of humic acid. The effect on MCDI was much more limited with these two foulants. The ability to clean the CDI cell with alkali cleaning agents was also investigated. While this cleaning was effective in restoring the salt adsorption, the alkali solution caused erosion of the activated carbon electrode or its PVDF binder, evidenced by an accumulation of carbon within the cleaning solution. Alternative electrode designs or alternative cleaning solutions will be needed if this approach is to be used in systems with similar foulants.

The wastewater discharged by cheese manufacturing processes is highly saline. This waste is generated from whey demineralization, chromatography and clean-in-place processes. Salty effluent can be diluted with other effluents and discharged as trade waste but the high salinity can trigger penalties imposed by local water authorities. Alternatively, such waste can be sent to evaporation ponds, but in some areas in Australia, environmental impacts regarding land degradation, odor and dust have prevented further pond construction. Similar concentrate and brine management issues are emerging in the seawater desalination and mining industries. This paper reviews a range of commercial and emerging separation technologies that may be suitable to both reduce the costs of salty wastewater treatment and to improve the recoveries of dairy and salt-based products. These technologies have been commercialized or applied at a laboratory scale to the fields of desalination and brine concentration. Each technology is discussed in terms of its principle of operation and suitability for treating high-salinity dairy wastewater. The potential energy requirement and processing cost of each technology is identified with respect to feed water salinity, to provide additional insights into the energy and cost efficiencies of these technologies.

In recent decades, the advancements in layer-by-layer (LBL) assembly technology have provoked increasing interest in the preparation of multilayer polyelectrolyte membranes with excellent performance. In the current study, a novel nanofiltration (NF) membrane was prepared by pressure-driven layer-by-layer (LBL) assembly of polyethylenimine (PEI) and polyacrylicacid (PAA) on a porous substrate with chemical crosslinking. The effect of deposition pressure on separation performance of the prepared membranes was studied. The surface morphology, hydrophilicity and the charge property of the dynamically-deposited membranes were compared with those prepared by static adsorption. The characterization results showed that dynamic deposition process resulted in a smoother membrane surface with improved hydrophilicity. The mechanism of water-path formation was proposed to interpret the effect of pressure on the membrane performance. Glutaraldehyde (GA) was used as a crosslinker to reduce the number of polyelectrolyte bilayers for obtaining good separation performance. The rejections of different inorganic salts of the dynamically-deposited NF membrane were also investigated.

Salty whey is a waste by-product that incurs increasingly high disposal costs for the dairy industry. This study investigated electrodialysis of the ultrafiltration permeate of salty whey as either a concentrate for the treatment of sweet whey or as a source of lactose and salt. The type of concentrate (0.1 m NaCl or salty whey permeate) did not affect the rate of sweet whey demineralisation or the energy consumed per tonne of whey, but less sodium and more divalent cations were removed when salty whey permeate was used as the concentrate. Salty whey permeate could be effectively demineralised using either 0.1 m NaCl or a second stream of salty whey permeate as the concentrate. The concentrate purity could be enhanced using monovalent selective membranes without increasing the energy consumption of the process (3.2 ± 0.3 kWh per kg of NaCl removed from the diluate at 15 V).

This work investigated the fouling of ion-exchange membranes during the electrodialysis of sweet and acid dairy whey. Fresh whey was used, rather than solutions made up in the laboratory, giving a unique perspective. While membrane fouling occurred in all experiments, the effects on system performance were limited. Reductions in the current during pure NaCl circulation fell to a minimum of 80% of the original value after 5 h of whey processing. The use of an alkaline concentrate resulted in the strongest increase in system resistance, but the mineral deposits formed appeared to detach readily, thereby reducing these effects. The use of an acidic concentrate gave significantly greater rates of lactic acid removal, which is important in industrial applications. A solution of HCl with a pH of 1.0 ± 0.15 was effective for in-situ cleaning of the mineral deposits. However, protein deposits were not readily removed using the recommended base cleaning formula of 3% NaCl at a pH of 9.2 ± 0.2.

Saline wastewater is a by-product of cheese manufacturing and whey processing that can have serious environmental and economic consequences. Salty streams originating from dairy processing operations include chromatography wastes, clean-in-place wastewater, acid whey, salty whey and waste generated from whey demineralization processes such as nanofiltration, electrodialysis and ion exchange. With the participation of the major dairy companies in Australia, an industry wide survey was conducted to acquire a comprehensive understanding of the management strategies for these salty waste streams. High salinity waste streams are commonly directed to evaporation ponds. However, environmental impacts from land degradation, odour and dust have prevented the construction of further evaporation ponds in some areas of Australia. The survey results also show that disposal to municipal trade waste is not always effective, as the current levels of some salinity-related parameters are significantly higher than the levels allowed by the local water/environmental authorities. For high salinity streams, salt removal can lead to more substantial savings in trade waste charges compared to wastewater volume reduction. Thus, salt removal and recovery from salty waste streams has become a major focus of the sustainability agenda of the Australian dairy industry.

In this study, the desalination performance of Capacitive Deionization (CDI) and Membrane Capacitive Deionization (MCDI) was studied for a wide range of salt compositions. The comprehensive data collection for monovalent and divalent ions used in this work enabled us to understand better the competitive electrosorption of these ions both with and without ion-exchange membranes (IEMs). As expected, MCDI showed an enhanced salt adsorption and charge efficiency in comparison with CDI. However, the different electrosorption behavior of the former reveals that ion transport through the IEMs is a significant rate-controlling step in the desalination process. A sharper desorption peak is observed for divalent ions in MCDI, which can be attributed to a portion of these ions being temporarily stored within the IEMs, thus they are the first to leave the cell upon discharge. In addition to salt concentration, we monitored the pH of the effluent stream in CDI and MCDI and discuss the potential causes of these fluctuations. The dramatic pH change over one adsorption and desorption cycle in CDI (pH range of 3.5-10.5) can be problematic in a feed water containing components prone to scaling. The pH change, however, was much more limited in the case of MCDI for all salts.

The solubility of calcium phosphate in concentrated dairy brine streams is important in understanding mineral scaling on equipment, such as membrane modules, evaporators, and heat exchangers, and in brine pond operation. In this study, the solubility of calcium phosphate has been assessed in the presence of up to 300 g/L sodium chloride as well as lactose, organic acids, and anions at 10, 30, and 50 °C. As a neutral molecule, lactose has a marginal but still detectable effect upon calcium solubility. However, additions of sodium chloride up to 100 g/L result in a much greater increase in calcium solubility. Beyond this point, the concentrations of ions in the solution decrease significantly. These changes in calcium solubility can readily be explained through changes in the activity coefficients. There is little difference in calcium phosphate speciation between 10 and 30 °C. However, at 50 °C, the ratio of calcium to phosphate in the solution is lower than at the other temperatures and varies less with ionic strength. While the addition of sodium lactate has less effect upon calcium solubility than sodium citrate, it still has a greater effect than sodium chloride at an equivalent ionic strength. Conversely, when these organic anions are present in the solution in the acid form, the effect of pH dominates and results in much higher solubility and a calcium/phosphate ratio close to one, indicative of dicalcium phosphate dihydrate as the dominant solid phase.

Ion-exchange membranes (IEMs) are unique in combining the electrochemical properties of ion exchange resins and the permeability of a membrane. They are being used widely to treat industrial effluents, and in seawater and brackish water desalination. Membrane Capacitive Deionisation (MCDI) is an emerging, energy efficient technology for brackish water desalination in which these ion-exchange membranes act as selective gates allowing the transport of counter-ions toward carbon electrodes. This article provides a summary of recent developments in the preparation, characterization, and performance of ion exchange membranes in the MCDI field. In some parts of this review, the most relevant literature in the area of electrodialysis (ED) is also discussed to better elucidate the role of the ion exchange membranes. We conclude that more work is required to better define the desalination performance of the proposed novel materials and cell designs for MCDI in treating a wide range of feed waters. The extent of fouling, the development of cleaning strategies, and further techno-economic studies, will add value to this emerging technique.

The utilisation of acid whey by the dairy industry is limited by the high concentrations of lactate in the solution. In the present study, three commercially available nanofiltration membranes: HL, XN45 and DK were used in to evaluate the separation of lactose and lactate as a function of pH. Raw acid whey was used after microfiltration, while two laboratory prepared solutions comprising lactic acid and lactose; and sodium lactate and lactose were also tested for comparison. The rejection of lactic acid was found to increase with the degree of acid dissociation. About 50% of the lactate could be removed at pH ∼3 due to the lower degree of dissociation. For all pH values tested, over 90% of the lactose was retained. The molecular weight cutoff and permeability of the membranes had little influence on the separation performance.

Membrane technology can be used for both post combustion carbon dioxide capture and acidic gas sweetening and dehydration of natural gas. These processes are especially suited for polymeric membranes with polyether functionality, because of the high affinity of this species for both H₂O and CO₂. Here, both crosslinked polyethylene glycol diacrylate and a polyether-polyamide block copolymer (PEBAX 2533(©)) are studied for their ability to separate CO₂ from CH₄ and N₂ under single and mixed gas conditions, for both dry and wet feeds, as well as when 500 ppm H₂S is present. The solubility of gases within these polymers is shown to be better correlated with the Lennard Jones well depth than with critical temperature. Under dry mixed gas conditions, CO₂ permeability is reduced compared to the single gas measurement because of competitive sorption from CH₄ or N₂. However, selectivity for CO₂ is retained in both polymers. The presence of water in the feed is observed to swell the PEG membrane resulting in a significant increase in CO₂ permeability relative to the dry gas scenario. Importantly, the selectivity is again retained under wet feed gas conditions. The presence of H₂S is observed to only slightly reduce CO₂ permeability through both membranes.

Cellulose acetate is the predominant material used in membrane separation of acid gases from natural gas and biogas. However, the sensitivity of these membranes to water vapor is not well understood. In this work, flat-sheet membranes of two different degrees of acetylation, were exposed to both dry and humidified CH4 and CO2/CH4 mixtures. Positron Annihilation Lifetime Spectroscopy experiments showed that the number of free volume elements decreased as water concentration increased, indicating pore filling effects. The size of the free volume elements declined initially, followed by an increasing trend at vapor partial pressures greater than 2.5 kPa, indicating polymer swelling. Gas permeabilities of CH4 and CO2 followed a similar trend, with an initial decline due to hindered diffusion and competitive sorption, followed by an increase as the humidity exceeded 2.5 kPa. Water vapor permeabilities increased from 11,000 to 27,000 Barrer as the water activity increased but a change in the rate of increase was also noted at 2.5 kPa. At humidities in excess of 0.8, the extent of membrane swelling was such that equilibrium was not established even after 8 h of operation. Importantly, plasticization had significantly less impact on the polymer with a higher degree of acetylation.

A series of mixed matrix membranes (MMMs) using nanoparticles involving carbons, porous organic polymers and metal organic frameworks (MOFs) were prepared to investigate the impact of water vapor on CO2 separation performance. The water uptake of MMMs using hydrophilic MOFs increased relative to more hydrophobic particles such as the porous organic polymers and carbons and this trend was reflected in the water vapor permeability, which varied by a factor of three between the hydrophobic and hydrophilic MMMs. These changes in water vapor permeability were strongly correlated with the water solubility, indicating that it is this solubility that is the controlling parameter. The calculated water diffusivity was consistent with previously published results. The gas permeability of MMMs in the presence of water vapor was also strongly affected by the nanoparticle hydrophobicity, with membranes composed of hydrophobic fillers out-performing hydrophilic fillers of comparable porosity. However in general, the differences in performance between MMMs and the pure polymer narrowed in the presence of water vapor.

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused o