Residual Salt Research Articles

Electrocoagulation reduces harvesting costs for microalgae

Centrifugation is the most commonly used method for harvesting autotrophically produced microalgae, but it is expensive due to high energy demands. With the aim of reducing these costs, we tested electrocoagulation with iron electrodes for harvesting Chlorella vulgaris. During extensive lab-scale experiments, the following factors were studied to achieve a high harvesting efficiency and a low iron content in the harvested biomass: electric charge, initial biomass concentration, pH, temperature, agitation intensity, residual salt content and electrolysis time. A harvesting efficiency greater than 95% was achieved over a broad range of conditions and the residual iron content in the biomass complied with legislative requirements for food. Using electrocoagulation as the pre-concentration step prior to centrifugation, total energy costs were reduced to 0.136 kWh/kg of dry biomass, which is less than 14% of that for centrifugation alone. Our data show that electrocoagulation is a suitable and cost-effective method for harvesting microalgae.

Study on the Effect of Crystal Size on the Performance of Ni-Rich Cathode Active Materials: Poly- Vs. Single Crystalline NCM622

Nickel-rich layered lithium nickel cobalt manganese oxides (NCMs, Li1+δNixCoyMnzO2, x+y+z+δ = 1 and δ > 0) are increasingly used as cathode active materials (CAMs) for lithium-ion batteries due to their high specific capacity; they are also expected to play a major role in future battery technologies, such as all-solid-state batteries. With increasing nickel content, however, the gained capacity is often accompanied by shorter cycle life due to undesired side reactions, resulting e.g. from the decomposition of residual lithium salts and surface contaminants that are present in greater amounts on Ni-rich materials,[1] as well as from the reaction of evolved lattice oxygen with the electrolyte,[2] which occurs at lower potentials for higher nickel content.[3] These processes degrade the NCM active material upon charge-discharge cycling and dramatically increase the impedance of the entire cell, eventually leading to cell failure. One way to minimize side reactions is to reduce the specific surface area through a greater NCM crystallite size, being known in the literature under the name of single crystals, which are expected to maintain their pristine surface area upon cycling.[4,5] By this approach, however, the NCM surface area normalized current of the CAM is significantly increased, possibly leading to critical overpotentials and compromising its rate capability.In this study, we investigate the electrochemical characteristics of two µm-sized NCM622 materials with a similar pristine BET surface area of ~0.3 m²/g: a polycrystalline material (PC) with secondary agglomerate diameters of ~5-10 µm comprised of primary crystallites with particle diameters on the order of ~10-1 µm, and a single crystalline material (SC) with individual primary crystallites of ~5 µm, both shown in the SEM images in Figure 1. Due to the highly unequal particle structure of the two material classes, one would expect significant differences in rate capability, long-term cycling behavior, extent of gassing at high state of charge (SOC), and the change of CAM surface area over the course of extended charge/discharge cycling.Calendered electrodes with PC or SC NCM622 with electrode loadings of ~12 mgAM/cm² were assembled in half-cells with a lithium metal reference electrode and then subjected to charge and discharge rate tests with potential cutoffs controlled by the reference electrode. Since clear differences in the rate-dependent discharge capacity of the two materials are observed, the impact of the particle morphology and the cause on the overpotential during (dis)charge are then further illuminated. In order to show that the difference in rate capability is owed to differences in the CAM surface increase upon cycling due to particle cracking that is induced by the NCM volume change upon (de-)lithiation, the Kr-BET surface area of pristine and charged electrodes of both PC and SC NCM622 is quantified. By this method, it is proven that, depending on the active material type, the CAM surface area may strongly increase, already during the very first charge. Due to this fundamental property, the amount of gas released from both CAMs is expected to differ significantly. We quantify the evolved O2 and CO2 during the first four cycles to >80 %SOC using On-Line Electrochemical Mass Spectrometry (OEMS). It is shown that the ratio of the surface area of both materials in charged state correlates well with the ratio of the amounts of gas released during electrochemical cycling. The obtained results on the fundamental properties of the two material classes on rate capability and gassing are complemented with long-term cycling experiments in full-cells at different upper cutoff potentials, chosen to be either below and or above the limit of oxygen release of NCM622 in order to analyze the evolution of the NCM622 particle morphology over extended charge/discharge cycling.In summary, this study gives comprehensive insights into the fundamental properties of poly- and single crystalline NCMs and into the impact of typical CAM failure mechanisms on the long-term cycling performance of these two material classes. Reference s : [1] J. Paulsen and J. H. Kim, USA Pat. US2014/0054495A1 (2014).[2] A. T. S. Freiberg, M. K. Roos, J. Wandt, R. de Vivie-Riedle, and H. A. Gasteiger, J. Phys. Chem. A, 122, 8828 (2018).[3] R. Jung, M. Metzger, F. Maglia, C. Stinner, and H. A. Gasteiger, J. Electrochem. Soc., 164, A1361 (2017).[4] Yongseon Kim, ACS Appl. Mater. Interfaces, 4, 2329 (2012).[5] G. Liu, M. Li, N. Wu, L. Cui, X. Huang, X. Liu, Y. Zhao, H. Chen, W. Yuan, and Y. Bai, J. Electrochem. Soc., 165, A3040 (2018). Figure 1

Chelator Regulation of In Situ Calcium Availability to Enable Spray-Dry Microencapsulation in Cross-Linked Alginates.

A recently patented one-step in situ cross-linked alginate microencapsulation (CLAM) by spray-drying (i.e., the UC Davis CLAMs technology) can overcome the high cost of scale-up that limits commercial applications. While increasing calcium loading in the CLAMs process can increase the extent of cross-linking and improve retention and protection of the encapsulated cargo, the potential for residual undissolved calcium salt crystals in the final product can be a concern for some applications. Here, we demonstrate an alternate one-step spray-dry CLAMs process using pH-responsive chelation of calcium. The “Chelate CLAMs” process is an improvement over the patented process that controls ion availability based on pH-responsive solubility of the calcium salt. Hyaluronic acid was encapsulated in CLAMs to minimize swelling and release in aqueous formulations. CLAMs with 61% (d.b.) hyaluronic acid (HA-CLAMs) demonstrated restricted plumping, limited water absorption capacity, and reduced leaching, retaining up to 49% hyaluronic acid after 2 h in water. Alternatively, “Chelate HA-CLAMs” formed by the improved process exhibited nearly full retention of hyaluronic acid over 2 h in water and remained visibly insoluble after 1 year of storage in water at 4 °C. Successful hyaluronic acid retention in CLAMs is likely due in part to its ability to cross-link with calcium.

Patterns of water 87Sr/86Sr variations in oil-, gas- and water-saturated rocks: Implications for fluid communication processes, distances and timescales

This study reviews 87Sr/86Sr depth profiles of formation waters sampled by Sr residual salt analysis (Sr RSA) from >100 oil/gas wells and research sites, including reservoirs with clastic and carbonate host rocks and with gas, oil and water as the continuous fluid phase. Globally, the water data form a smooth trend between low seawater-like 87Sr/86Sr ratios (~0.706) at shallow depths and high (~0.724) ratios in deeply buried rocks, where water-rock interaction dominates.We test the hypothesis that 87Sr/86Sr depth profiles in individual wells could be influenced by diffusional mixing processes by developing 1D diffusion mixing equations to simulate compositional patterns through time and comparing them with observed profiles. Different combinations of boundary and initial conditions generate various patterns characteristic of diffusion, including non-steady-state curves relating to incomplete mixing and steady-state patterns (such as vertical or inclined straight lines) where initial heterogeneities have fully mixed. The dataset yielded 193 occurrences of these patterns. Steady-state patterns are more common and longer in water zones, while non-steady-state patterns are more common and longer in oil and gas zones. The detection of diffusional mixing patterns in hydrocarbon-saturated rocks suggests that diffusion is active, although on average a factor of ~13–18 slower, than in comparable water-saturated rocks.Pattern generation and equilibration times were modelled for each non-steady-state pattern and compared with the time since reservoir filling with oil/gas, revealing that 90% of them could have been generated since filling, but 60% of them would already have mixed to steady state had the initial compositional heterogeneities arisen during or before reservoir filling. This is critical evidence that at least some of the initial heterogeneities must have arisen, and subsequently partially mixed, after filling; these patterns tend to be short (<40 m, usually <20 m). We conclude that it is essential to consider post-filling processes when interpreting 87Sr/86Sr depth profiles. This may enable the effects of post-filling processes to be stripped back to reveal larger-scale patterns inherited from oil/gas filling. This approach provides a new framework for identifying and quantifying barriers to fluid communication in petroleum reservoirs, which could be applied to help optimize oil/gas production and water or gas injection, including CO2 injection for enhanced oil recovery and/or subsurface storage.The evidence for post-fill water-rock interaction and diffusive transport has important implications for porosity/permeability prediction, indicating that key diagenetic processes like quartz cementation may be inhibited by hydrocarbon filling but not stopped altogether. Compositional differences of water within oil/gas zones reveal the folly of using one aquifer water sample as the basis for interpreting water saturations from well resistivity logs for in-place resource estimation. Sr RSA studies may thus be useful in designing water sampling strategies.

Effects of treatment agents during acid washing and pH neutralization on the fertility of heavy metal-impacted dredged marine sediment as plant-growing soil

The present study was aimed at investigating the effects of different acids and pH neutralizers applied to dredged marine sediment for the treatment of heavy metals, and the resulting influence on the sediment quality as a plant growth medium. The inspection of barley germination in the dredged marine sediment revealed that residual salts are critical plant stressors whose adverse effects exceed those exhibited by high-level heavy metals and petroleum hydrocarbons present in the sediment. Acid washing and pH neutralization reduced not only the heavy metal contents but also the sediment salinity (by factors of 6.1–9.5), resulting in 100% germination of barley. For acid-washed and calcium-oxide-neutralized sediment, the barley growth was comparable to that observed in untreated and water washed sediment despite factors of 5.2–8.0 greater sediment salinity in the former. This result represents the protective effect of residual calcium against sodium and chloride toxicity. Water washing of acid-washed and pH-neutralized sediments further enhanced barley growth owing to the reduction in osmotic pressure. This study showed the effect of different sediment-washing reagents on the product quality. It also indicated the significance of balancing the enhancement of product quality and economic cost of further treatment requirements.

Comparative investigation of characteristics and phosphate removal by engineered biochars with different loadings of magnesium, aluminum, or iron

Engineered biochars (EBCs) loaded with metal oxides/hydroxides have been used as sorbents to remove and recycle phosphate (P) from wastewater. However, P removal by EBCs made with different types and loading of metals have rarely been compared in a single study. Thus, in this study, EBCs were synthesized through pyrolysis of bamboo or hickory wood chips (25 g) pretreated with four amounts (25, 50, 75, and 100 mmol) of magnesium (Mg), aluminum (Al), or iron (Fe) salt solutions (Mg-EBC, Al-EBC, and Fe-EBC, respectively). The resulting EBCs were loaded with metal oxides/hydroxides that served as P adsorption sites. Al-EBCs showed the highest aqueous stability with little metal dissolution, which can be attributed to the low level of residual (unconverted) metal salt as well as the extremely low solubility of loaded Al metal oxyhydroxide. After the leaching/washing, the metal loading efficiencies of the Al- and Mg-EBCs were similar (50–60%) and stable metal loadings increased with pretreatment salt amounts, indicating that the amount of the two metal oxides/hydroxides in the EBCs can be controlled during pretreatment. However, stable iron oxide on the Fe-EBCs remained almost the same for all the four levels of pretreatment, reflecting saturation of the biochar surface. All the EBCs showed increasing P adsorption with increasing metal loading. At low initial P concentrations of 31 mg/L, Fe- and Al-EBCs removed up to 68% and 94% of P, likely through an electrostatic interaction mechanism. At high P concentrations, Mg-EBC had the largest P adsorption capacity (119.6 mg P/g), mainly through the combination of surface precipitation and electrostatic interaction mechanisms. This study demonstrates that metal oxide/hydroxide-loaded EBCs are promising sorbents that can be designed to meet specific needs for the removal of aqueous P in various applications.

Development, validation and regulatory acceptance of improved purification and simplified quality control of [13N] Ammonia

Background[13N]Ammonia is a cyclotron produced myocardial perfusion imaging agent. With the development of high-yielding [13N]ammonia cyclotron targets using a solution of 5 mM ethanol in water, there was a need to develop and validate an automated purification and formulation system for [13N]ammonia to be in a physiological compatible formulation of 0.9% sodium chloride since there is no widely available commercial system at this time. Due to its short half-life of 10 min, FDA and USP regulations allow [13N]ammonia to be tested in quality control (QC) sub-batches with limited quality control testing performed on the sub-batches for patient use. The current EP and the original USP method for the determination of the radiochemical purity and identity of [13N]ammonia depended on an HPLC method using a conductivity detector and a solvent free of other salts. This HPLC method created issues in a modern cGMP high volume PET manufacturing facility where the HPLC is used with salt containing mobile phase buffers for quality control analysis of other PET radiopharmaceuticals. Flushing of the HPLC system of residual salt buffers which may interfere with the [13N]ammonia assay can take several hours of instrument time. Since there are no mass limits on [13N]ammonia, a simplified TLC assay to determine radiochemical identity and purity could be developed to simplify and streamline QC.ResultsWe have developed and validated a streamlined automated synthesis for [13N]ammonia which provides the drug product in 8 mL of 0.9% sodium chloride for injection. A novel radio-TLC method was developed and validated to demonstrate feasibility to quantitate [13N]ammonia and separate it from all known radiochemical impurities.ConclusionsThe process for automated synthesis of [13N]ammonia simplifies and automates the purification and formulation of [13N]ammonia in a cGMP compliant manner needed for high-throughput manufacture of [13N]ammonia. The novel radio-TLC method has simplified [13N]ammonia quality control (QC) and now enables it to be tested using the same QC equipment as [18F]fludeoxyglucose (FDA/USP recognized name for 2-[18F]fluoro-2-deoxy-D-glucose). Both the streamlined automated synthesis of [13N]ammonia and the novel radio-TLC method have been accepted and approved by the US Food and Drug Administration (FDA) for the cGMP manufacture of [13N]ammonia.

Effect of anion type on enzymatic hydrolysis of starch-(thermostable α-amylase)-calcium system in a low-moisture solid microenvironment of bioextrusion

The effect of six anions (Clˉ, OHˉ, NO3ˉ, SO42ˉ, C6H10O62ˉ and PO43ˉ) on a starch (St)-enzyme (thermostable α-amylase, TαA)-calcium (Ca) system was investigated in a low-moisture solid state. Two levels of Ca salts (1 and 10 mmol/100 g St) added to potato starch with and without TαA were analyzed by FT-IR, DSC and SEM. The surface morphologies of the St-Ca complexes were different in the presence of various anions, and the residual Ca salts around the St granules might decrease the enzymatic action. For bioextrusion, TαA (0.5‰ and 1.5‰) were introduced for a relatively low Ca content (1 mmol/100 g). Significant differences in enzyme activity were observed, increasing the activity of TαA by SO42ˉ (146.54 %) > C6H10O62ˉ > Clˉ > control > NO3ˉ > OHˉ ≈ PO43ˉ and C6H10O62ˉ (123.20 %) ≈ Clˉ ≈ SO42ˉ > control > PO43 > OHˉ > NO3ˉ for the low and high enzyme levels, respectively.

Dilution of Li-Li2O in a metallic fuel produced through oxide reduction using ZrO2-assisted rinsing in molten LiCl

This study explored the feasibility of rinsing a metallic fuel in a separate LiCl salt as a new alternative to salt distillation, aimed to dilute Li and Li2O in the residual oxide reduction (OR) salt of the fuel and then supply the fuel for electrorefining. The rinsed metallic fuel was conducted by simply immersing the fuel in a LiCl salt at 650 °C. During the immersion, the residual OR salt in the fuel was dissolved, and Li2O and Li generated during the OR of the fuel were diluted. Li and Li2O dissolved in LiCl were successfully consumed by chemically reacting with ZrO2 immersed in the salt. Even after the metallic fuel was rinsed in a common LiCl salt, the Li-Li2O concentration in the salt was maintained at the initial concentration before the rinsing owing to the use of ZrO2. Moreover, the Li-Li2O in the fuel was significantly diluted during the rinsing.

Enhanced metastable state models of TAM kinase binding to cabozantinib explains the dynamic nature of receptor tyrosine kinases

Receptor tyrosine kinases (RTKs) are essential proteins in the regulation of cell signaling. Tyro3, Axl and Mer are members of TAM RTKs and are overexpressed in several cancer forms. Kinase inhibitors such as cabozantinib, foretinib are reported to inhibit TAM kinases at nanomolar concentrations. The atomistic details of structure and mechanism of functional regulation is required to understand their normal physiological process and when bound to an inhibitor. The docking of cabozantinib into the active state conformations of TAM kinases (crystal structure and computational models) revealed the best binding pose and the complex formation that is mediated through non-bonding interactions involving the hinge region residues. The alterations in the conformations and the regions of flexibility in apo and complexed TAM kinases as a course of time are studied using 250 ns molecular dynamics (MD) simulations. The post-MD trajectory analysis using Python libraries like ProDy, MDTraj and PyEMMA revealed encrypted protein dynamic motions in active kinetic metastable states. Comparison between Principal component analysis and Anisotropic mode analysis deciphered structural residue interactions and salt bridge contacts between apo and inhibitor bound TAM kinases. Various structural changes occurred in αC-helix and activation loop involving hydrogen bonding between residues from Lys-(β3 sheet), Glu-(αC-helix) and Asp-(DFG-motif) resulting in higher RMSD. Mechanical stiffness plots revealed that similar regions in apo and cabozantinib bound Axl fluctuated during MD simulations whereas different regions in Tyro3 and Mer kinases. The residue interaction network plots revealed important salt bridges that lead to constrained domain motions in the TAM kinases. Communicated by Ramaswamy H. Sarma

MORPHOGENETIC CHARACTERISTICS AND BIOLOGICAL ACTIVITY OF TAKYR AND MEADOW SOILS OF THE REPUBLIC OF KARAKALPAKSTAN (ON THE EXAMPLE OF SOILS OF CHIMBAY DISTRICT)MORPHOGENETIC CHARACTERISTICS AND BIOLOGICAL ACTIVITY OF TAKYR AND MEADOW SOILS OF THE REPUBLIC OF KARAKALPAKSTAN (ON THE EXAMPLE OF SOILS OF CHIMBAY DISTRICT)

This article is devoted to the problems of desertification, the problems of desertification is one of the most striking examples of complex soil degradation, which includes such unfavorable processes as erosion, deflation, salinization, salinization, re-compaction, and others. And also, the article deals with such common soils as: takyr, meadow-alluvial, salt marshes, residual-bog, takyr in combination with residual salt marshes, takyr in combination with desert sandy soils and sands, takyr-meadow, takyrno Meadow in a complex with desert meadow, meadow, bog meadow soils. In addition to the above, we are also talking about the vegetation cover, which is represented by hodgepodge, tamarix, and sometimes on saxaul on adjoined soils. As a result of global climate change, the disturbance of the natural balance for a long time and, first of all, the redistribution of water reserves, the intensification of the drought of the coastal area under the influence of the drying of the Aral Sea, caused a noticeable change in the soil cover. These changes led to a sharp decrease in groundwater in the territories of the former “living” Amu Darya delta, an increase in their mineralization, a decrease in vegetation cover, and a manifestation of the evolutionary process characteristic of the soil cover. These and other signs of soil and soil cover of these territories are highlighted.

Effect of Alkalinity on Catalytic Activity of Iron-Manganese Co-Oxide in Removing Ammonium and Manganese: Performance and Mechanism.

In this study, a pilot-scale experimental filter system was used to investigate the effect of bicarbonate alkalinity on the activity of an Fe–Mn co-oxide for ammonium and manganese removal from surface water. The results showed that an increase in alkalinity to 150 mg/L (calculated as CaCO3) by the addition of NaHCO3 significantly promoted the activity of the Fe–Mn co-oxide. The ammonium and manganese removal efficiencies of the Fe–Mn co-oxide increased from 40% to 95% and 85% to 100%, respectively. After NaHCO3 was no longer added, the activity of the filter column remained. Moreover, pH (7.4–8.0) and temperature (12.0–16.0 °C) were not the main factors affecting the activity of the filter, and had no significant effect on the activity of the filter. Further characterization analysis of the Fe–Mn co-oxide filter film showed that after alkalinity was increased, the accumulation of aluminum on the filter media surface decreased from 3.55% to 0.16% and the oxide functional groups changed. This was due to the action of bicarbonate and the residual aluminum salt coagulant in the filter, which caused the loss of Al from the surface of the filter media and weakened the influence of the aluminum salt coagulant on the activity of the Fe–Mn co-oxide; hence, the activity was recovered.

Effect of residual metal salt on reverse osmosis membrane by coagulation-UF pretreatment process

Effect of residual metal salt on reverse osmosis membrane by coagulation-UF pretreatment process

Dehalogenation of electrochemical processing salt simulants with ammonium phosphates and immobilization of salt cations in an iron phosphate glass waste form

This study demonstrates the conversion of a simulated salt waste from electrochemical fuel reprocessing into a chemically durable iron phosphate glass waste form through reaction of the salt with ammonium hydrogen phosphate precursors [i.e., NH4H2PO4 and (NH4)2HPO4] and adding Fe2O3. The reaction of the salt simulant ERV2 with the phosphate precursors resulted in dehalogenation of the salt through the production of gaseous NH4Cl and water vapor (plus other minor byproducts) with the residual salt cations incorporating into the iron phosphate glass as oxides. Physical properties and chemical durabilities were measured for iron phosphate glasses made using different salt/phosphate/Fe2O3 ratios. These iron phosphate glasses accommodate high salt cation loadings and have high bulk densities (∼3 × 103 kg/m3), which would provide a high storage volume waste form option (i.e., the volume required to immobilize a given mass of waste). A proof-of-concept demonstration was conducted to show that the NH4Cl off-gas generated during this process reacts with uranium dendrites to directly produce UCl3 that can be recycled as a feedstock for electrochemical processing.

Impacts of topography change on saltwater intrusion over the past decade in the Changjiang Estuary

Saltwater intrusion in estuaries is mainly controlled by tides and river discharge, as well as by topography and other factors. The Changjiang estuary has been seen a significant change in its topography from the data obtained in 2007 and 2017. In this study, a well-validated 3D numerical model was used to simulate and analyze the residual water and salt transport, water diversion ratio (WDR) in bifurcated channels and water resources in the Changjiang Estuary in 2007 and 2017. The comparisons of the model results showed that due to the North Branch becoming much shallower and narrower over the period from 2007 to 2017, the overall salinity in the North Branch decreased and the intensity of saltwater spillover (SSO) from the North Branch into the South Branch weakened. In the North Channel, the simulated residual or net transection water flux (NTWF) and WDR decreased during spring tides, resulting in increased saltwater intrusion. During neap tides, the saltwater intrusion was weakened despite the decreased NTWF and WDR because the water depth at the river mouth became shallower. The changes of topography during that period also resulted in changes of DWR, NTWF, salt transport across the tidal flats and dykes in the North Passage, South Passage and the South Channel, as well as overall dynamic mechanism. The results indicated that the salinity at the water intakes of the three reservoirs in the estuary slightly decreased, indicating that the time that reservoirs can take water from the estuary become longer in dry seasons. In the scenario of complete silt-up of the North Branch, the saltwater intrusion was weakened in the South Branch because of the disappearance of the SSO, which was favorable for the utilization of freshwater resources, but enhanced in the North Channel, North and South Passages. The overall influence from the topographic change over the period is that the saltwater intrusion is weakened in the North Branch, and enhanced during spring tides and weakened during neap tides in the North Channel, North and South Passages. Sediment accretion in the North Branch is favorable for utilization of freshwater resources.

Automatic classification of Alzheimer disease based on MRI volumetric features

The cost of polyhydroxyalkanoates (PHAs) can be reduced by improving their productivity and recovery. In this study, we attempted to obtain a high cell density culture from a 13 L bioreactor and subsequently improved the recently developed biological recovery process using mealworms to obtain the PHA granules. A cell dry weight of 161 g/L containing 68–70 wt% P(3HB) was obtained. The freeze-dried cells contained a significant amount of mineral salts from the culture medium which reduced the cells’ palatability for the mealworms. A simple washing procedure with water was sufficient to remove the residual mineral salts and this improved the cells’ consumption by up to 12.5% of the mealworms’ body weight. As a result, one kilogram of mealworms consumed 125 g of the washed cells daily and 87.2 g of feacal pellets were recovered, which was almost twice the weight of the unwashed cells. In addition, it also improved the purity of the PHA in the faecal pellets to a value <90% upon washing with water to remove the water-soluble compounds. This study has demonstrated a significant improvement in the production and recovery of PHA. In addition, the resulting mealworms showed a significant increase in protein content up to 79% and a decrease in fat content down to 8.3% of its dry weight.

Effective sericin-fibroin separation from Bombyx mori silkworms fibers and low-cost salt removal from fibroin solution

Silk from Bombyx mori has two main proteins: fibroin and sericin. Fibroin is a protein that exhibits good biocompatibility and high surface reactivity, desirable properties for many biomedical applications. Sericin is related with adverse immune response in some medical uses. Therefore, its removal (degumming) is desirable in almost all fields, including the textile industry and biological applications. In this study, three degumming methods (distilled water, liquid neutral detergent and sodium carbonate solution) were evaluated using Raman spectroscopy. Degummed silk treated with sodium carbonate solution exhibits a pattern consistent with previous studies for sericin-free fibroin, and significant differences with the untreated silk pattern. Also, degummed fibroin fibers were dissolved in a calcium chloride solution, in pursuit of a more versatile material. Additionally, different porous membranes of dialysis tubes were tested to remove residual salts, and were compared by conductivity measurements and EDS analysis, identifying good performance for an affordable food cellulose membrane. The results showed that it is possible to obtain fibroin with adequate chemical properties, using low-cost process and membrane of dialysis tubes.

Water-Soluble 2,5-Anhydro-d-mannofuranose Chain End Chitosan Oligomers of a Very Low Molecular Weight: Synthesis and Characterization.

Five chitosans with different degrees of N-acetylation (DAs), molar masses, and origins were depolymerized by nitrous acid treatment in acidic media, leading to water-soluble 2,5-anhydro-d-mannose chain end oligomers with DPn < 20. The kinetics of the reaction was studied, and the best work conditions were found to be 3 h reaction at 50 °C. It was shown that the DPn of oligomers only depends on the quantity of NaNO2 involved. Molar masses or DAs do not have an impact on the depolymerization process when targeting oligomers with less than 20 units. This depolymerization process also leads to free 2,5-anhydromannofuranose (AMF) that might react with the free amines of obtained oligomers to form imines. This reaction is pH-dependent and in acidic condition leads to the formation of 5-hydromethyl-2-furfural (HMF). At the end, the oligomers were purified by dialysis to get rid of most of the free AMF (<5%) and other residual salts and appeared to have no acute toxicity.

High cell density culture of Cupriavidus necator H16 and improved biological recovery of polyhydroxyalkanoates using mealworms

The cost of polyhydroxyalkanoates (PHAs) can be reduced by improving their productivity and recovery. In this study, we attempted to obtain a high cell density culture from a 13 L bioreactor and subsequently improved the recently developed biological recovery process using mealworms to obtain the PHA granules. A cell dry weight of 161 g/L containing 68–70 wt% P(3HB) was obtained. The freeze-dried cells contained a significant amount of mineral salts from the culture medium which reduced the cells’ palatability for the mealworms. A simple washing procedure with water was sufficient to remove the residual mineral salts and this improved the cells’ consumption by up to 12.5% of the mealworms’ body weight. As a result, one kilogram of mealworms consumed 125 g of the washed cells daily and 87.2 g of feacal pellets were recovered, which was almost twice the weight of the unwashed cells. In addition, it also improved the purity of the PHA in the faecal pellets to a value <90% upon washing with water to remove the water-soluble compounds. This study has demonstrated a significant improvement in the production and recovery of PHA. In addition, the resulting mealworms showed a significant increase in protein content up to 79% and a decrease in fat content down to 8.3% of its dry weight.

A simple novel route for porous carbon production from waste tyre.

In this research, waste tyre rubber was used for activated carbon production with a novel route by modified physo-chemical approach. Potassium hydroxide and carbon dioxide were selected as chemical and physical activating agents, respectively and the process was carried out without carbonization under inert atmospheric conditions. The experiments were designed by applying the central composite design (CCD) as one of the subsets of response surface methodology (RSM). The effects of activation temperature (550-750 °C), activation time (15-75 min), impregnation ratio of KOH/rubber (0.75-3.75) and CO2 flow rate (200-400 mL/min) on production yield and specific surface area of produced activated carbon were studied. Based on the results, the 2FI and quadratic models were selected for production yield and specific surface area, respectively. The activation temperature was the main effective parameter on both responses in this process. The production yield and specific surface area of produced activated carbon at optimized conditions for each model were 47% and 928 m2/g, respectively. BET, XRF, XRD, FT-IR, EDS and FE-SEM analyses were carried out on the optimized sample of specific surface area model in order to investigate the residual salts and morphological porous structures. Based on the surface properties and the presence of sulfur compounds in produced activated carbon, this activated carbon has the ability of eliminating heavy metals such as mercury from industrial waste water.