Chemical and Biomolecular Engineering - Research Publications
Now showing items 25-36 of 512
Efficient degumming of crude canola oil using ultrafiltration membranes and bio-derived solvents
(ELSEVIER SCI LTD, 2020-01-01)
Vegetable oils derived from rapeseed and its genetic variant canola, are conventionally extracted from oilseeds by means of an organic solvent, typically hexane. Concerns regarding the toxicity of hexane have meant safer and more environmentally friendly solvents such as terpenes are becoming attractive. In this research, the degumming of canola oil/terpene mixtures using ultrafiltration is considered as a critical step in such an extraction process. Polysulfone (PSF) and polyethersulfone (PES) membranes were found to be ineffective in this application, as the oil appeared to cause swelling of the membrane structure. This meant that the original flux could not be restored after cleaning. Conversely, a ceramic membrane (MWCO 5 kDa) provided stable behaviour over several cycles of operation when cleaned with pure solvent at high cross velocity at 40 °C. This membrane showed high phospholipid retention (95 ± 2%), although some oil was also retained (16 ± 3%). Cymene emerged as the most attractive of the three terpenes tested, with higher permeate flux and phospholipid rejection than limonene or pinene.
Membrane gas-solvent contactor pilot plant trials for post-combustion CO2 capture
Membrane gas-solvent contactors are a hybrid technology of solvent absorption with membrane separation that achieves efficient and compact carbon dioxide capture. Here, we report on a successful pilot plant trial of membrane contactor technology undertaking post-combustion carbon dioxide capture from flue gas generated by an Australian black coal fired power station. The pilot plant utilised membrane contactors to undertake CO2 absorption into 30 wt% monoethanolamine (MEA) and the subsequent solvent regeneration stage to produce a pure CO2 product. The pilot plant trials identified a commercially available non-porous poly dimethylsiloxane composite hollow fiber membrane as the most suitable for both CO2 absorption and solvent regeneration. The overall mass transfer coefficient for CO2 absorption across the membrane into the solvent was comparable to laboratory results, enabling a recovery of >90% CO2 from the flue gas. Over time the mass transfer coefficient decreased because of both solvent dilution and some MEA loss, which reduced the enhancement the reaction provides to mass transfer in the solvent boundary layer. The overall mass transfer of CO2 from the solvent into the steam sweep during solvent regeneration was greater than that observed in the laboratory for the same temperature. The energy demand of the pilot plant was higher than for conventional CO2 capture technology, given the pilot nature of the process, lack of energy integration and thermal losses from uninsulated membrane modules. Accounting for these factors, the energy duty of the membrane contactor process was evaluated to be less than 4.2 MJ/kg of CO2 captured. Critically, the pilot plant demonstrated the viability of membrane contactor technology for post-combustion carbon capture on an industrial scale.
Simulation and economic assessment of large-scale enzymatic N-acetyllactosamine manufacture
N-acetyllactosamine (LacNAc) is an important lactose-derived molecule which can act as an effective prebiotic. In this study a process for the enzymatic synthesis and downstream purification of LacNAc was designed based on the use of thermostable β-galactosidases from Bacillus circulans (BgaD-D), Thermus thermophilus HB27 or Pyrococcus furiosus (CelB) respectively. Four configurations for the purification stage were simulated; anion-exchange chromatography, an activated charcoal-Celite column, N-acetylglucosamine (GlcNAc) crystallization and an activated charcoal-Celite column, as well as selective crystallization. While the enzyme CelB has greater stability at higher temperatures, this enzyme gives a lower LacNAc yield, leading to significant capital investment. For the design based on the BgaD-D biocatalyst and anion exchange chromatography, recovery of GlcNAc improved the project profitability when the GlcNAc price was greater than $10 per kg. GlcNAc was the main contributor to the raw material costs for most processes, although methanol contributed 72% of these costs for the process based on an activated charcoal column. The use of a crystallizer for GlcNAc separation before this column, reduced this methanol consumption by 73%. The use of selective crystallization proved the best approach, reducing the minimum LacNAc sales price to $2 per gram. The plant was more economic when the acceptor to donor ratio was reduced from 10 to 4 and the lactose concentration increased from 50 mM to 550 mM.
Pilot Study on the Removal of Lactic Acid and Minerals from Acid Whey Using Membrane Technology
(AMER CHEMICAL SOC, 2020-02-24)
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.
Modelling of methane and n-butane sorption, diffusion and permeation in polydimethylsiloxane using PC-SAFT
Published sorption, diffusion and permeation data for methane and n-butane in polydimethylsiloxane (PDMS) from −20 to 50 °C was simulated using a perturbed chain statistical association theory (PC-SAFT) based model. The use of a temperature-dependent interaction parameter within the PC-SAFT model allowed the pure gas sorption data to be very well represented. The mixed gas sorption results were fully predictable from these pure gas parameters, without the introduction of any additional parameters, and agreed well with the experimental data. The model was also able to model the dilation behavior of PDMS under various gas compositions, making it possible to analyse gas sorption properties using pure gas sorption data only. A diffusion model coupled with the PC-SAFT model was capable of fitting both pure and mixed gas permeation data well by applying an exponential expression to account for such dilation in the diffusivity term. Only two parameters (i.e. infinite dilution mobility coefficient L0 and plasticization factor β) were used and no coupling effect between the two penetrants was needed. The activation energies of L0 were 11.7 and 13.4 kJ mol−1 for methane and n-butane. Moreover, the model was also able to calculate the concentration profiles of the penetrants across the membrane thickness. For n-butane, the mass concentration profile changed from linear to non-linear when the feed pressure increased from 4 to 11 atm for 8 mol% n-butane at 25 °C. Conversely, methane showed a linear concentration profile under both conditions.
Eutectic freeze crystallization of saline dairy effluent
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.
Single and binary ion sorption equilibria of monovalent and divalent ions in commercial ion exchange membranes.
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.
Spider-silk inspired polymeric networks by harnessing the mechanical potential of β-sheets through network guided assembly.
The high toughness of natural spider-silk is attributed to their unique β-sheet secondary structures. However, the preparation of mechanically strong β-sheet rich materials remains a significant challenge due to challenges involved in processing the polymers/proteins, and managing the assembly of the hydrophobic residues. Inspired by spider-silk, our approach effectively utilizes the superior mechanical toughness and stability afforded by localised β-sheet domains within an amorphous network. Using a grafting-from polymerisation approach within an amorphous hydrophilic network allows for spatially controlled growth of poly(valine) and poly(valine-r-glycine) as β-sheet forming polypeptides via N-carboxyanhydride ring opening polymerisation. The resulting continuous β-sheet nanocrystal network exhibits improved compressive strength and stiffness over the initial network lacking β-sheets of up to 30 MPa (300 times greater than the initial network) and 6 MPa (100 times greater than the initial network) respectively. The network demonstrates improved resistance to strong acid, base and protein denaturants over 28 days.
Nanobiohybrids: Materials approaches for bioaugmentation.
Nanobiohybrids, synthesized by integrating functional nanomaterials with living systems, have emerged as an exciting branch of research at the interface of materials engineering and biological science. Nanobiohybrids use synthetic nanomaterials to impart organisms with emergent properties outside their scope of evolution. Consequently, they endow new or augmented properties that are either innate or exogenous, such as enhanced tolerance against stress, programmed metabolism and proliferation, artificial photosynthesis, or conductivity. Advances in new materials design and processing technologies made it possible to tailor the physicochemical properties of the nanomaterials coupled with the biological systems. To date, many different types of nanomaterials have been integrated with various biological systems from simple biomolecules to complex multicellular organisms. Here, we provide a critical overview of recent developments of nanobiohybrids that enable new or augmented biological functions that show promise in high-tech applications across many disciplines, including energy harvesting, biocatalysis, biosensing, medicine, and robotics.
Shear Induced Interactions Cause Polymer Compression.
Shear induced particle pressure occurs in concentrated suspensions of particles. Importantly, the significance of the shear induced particle pressure has not been recognized in polymer rheology. The shear induced particle pressure results in an inward pressure on the polymer chains resulting in a shear dependent compressive force. The analytical form of the force balance equations that incorporate the effect of shear induced particle pressure predict a reduced polymer blob size and reducing viscosity with increasing shear rate as has been observed experimentally. Power law behavior is found for the viscosity in accord with the general observations for concentrated polymer rheology.
Polyphenol-Mediated Assembly of Proteins for Engineering Functional Materials.
Functional materials composed of proteins have attracted much interest owing to the inherent and diverse functionality of proteins. However, establishing facile and general techniques for assembling proteins into nanomaterials is challenging owing to the complex physicochemical nature and potential denaturation of proteins. Here a simple, versatile strategy is introduced to fabricate functional protein assemblies through the interfacial assembly of proteins (>10 studied herein) and polyphenols (e.g., tannic acid) on various substrates (organic, inorganic, and biological). The dominant interactions (hydrogen bonding, hydrophobic and ionic interactions) between the proteins and tannic acid are elucidated-most proteins undergo multiple noncovalent-stabilizing interactions with polyphenols, which can be used to engineer responsiveness into the assemblies. As demonstrated, the proteins retain their structure and function within the assemblies, thereby enabling their use in various applications (e.g., catalysis, fluorescent imaging, and cell targeting).