High Metal Ion Concentrations Research Articles

Removal of Methylene Blue by Granitic Residual Soil Supported Nano Zero Valent Iron (Gr-nZVI): Kinetic and Equilibrium Studies

The presence of dyes in water sources that act as contaminants is hazardous to human and animal health. Therefore, this research was conducted on the removal of methylene blue (MB) using granitic residual soil-supported nano zero-valent iron (Gr-nZVI), to examine its potential use as an efficient adsorbent. Batch adsorption experiments were conducted in this study to examine the impact of initial dye concentration, contact time, dosage, pH and temperature effets. Based on the results, it can be inferred that Gr-nZVI (with Kd=0.1 L/g and R2 =1) exhibits superior adsorption of MB at higher metal ion concentrations when compared to granitic residual soil (Gr) (with Kd=0.0588 L/g and R2 =0.9267). The removal percentage of Gr-nZVI was found to be 100%, obtained at 100 mg/L MB ion concentration. Sorption data have been correlated with both Langmuir and Freundlich adsorption models. However, the Langmuir isotherm was the only model that showed a good fit for the adsorption of MB on Gr-nZVI. The mechanistic phases of the process were determined through kinetic energy studies. Kinetic data showed the removal of MB was 100% within 5 min for both Gr-nZVI and Gr. This indicates the very fast adsorption of MB and data followed a pseudo-second order. According to adsorption analysis, Gr demonstrated a higher adsorption capacity for MB removal compared to Gr-nZVI and nZVI. This study also highlights that nZVI does not facilitate MB adsorption, making the composite nZVI unnecessary due to Gr is capable of removing MB on its own.

Investigation on the effect of Cu2+, Mn2+ and Fe3+ on biotreatment of Cr(VI) by Shewanella oneidensis and Bacillus subtilis in bimetallic system

Coexistence of chromium and iron, manganese and copper in industries is common, which may affect the microbial treating efficiency and toxicity to microorganisms, thus restricting the application of microbial treatment technology. In this research, Cu2+ promoted the reduction of Cr(VI) and the fixation of total chromium in bimetallic systems for both Shewanella oneidensis MR-1 and Bacillus subtilis, while Mn2+ and Fe3+ exhibited inhibition effects. Generally, groups with coexisting heavy metal of 0.1 mM were most affected, no matter promotive or inhibitive. Toxicity analysis revealed that high concentration of heavy metal ions led to damage to the cell membranes and reduction of their survival rate. To clarify the optimal condition for microbial treatment, response surface methodology was used to investigate the influencing factors of Cr(VI) reduction by S. oneidensis. The total chromium concentration in the supernatant was correlated with three factors, and the significant order of influence was: culture time > culture temperature > pH.

Gene Expression in Cadmium Sulfide Biological-Nanoparticle Hybrids

Through millions of years of evolution, bacteria have developed unique and complex ways to survive, allowing them to inhabit ecosystems all over the Earth, including places with high metal ion concentrations. Bacteria have developed many survival mechanisms to evade metal ion toxicity. Survival mechanisms to evade metal toxicity include the ability to transform metal ions into nanoparticles. When metal ions bind to other constituents to form nanoparticles, the metal ion concentrations in the environment can be lowered, in turn lessening the likelihood of cells encountering toxic concentrations of metals. These nanoparticles can be expelled by the bacteria into the environment, remain inside the bacteria, or attached to the cell surface. Bacteria and metal nanoparticles have many useful functions on their own. Furthermore, these functions can be combined when the two come together. Cells that produce metal nanoparticles that remain attached to their surface are referred to as biological-nanoparticle hybrids (bionanohybrids), as shown in the scanning electron image in Fig. 1. Surface-associated nanoparticles (SANs) can enhance biological functions, enabling a variety of new applications related to bioremediation, energy production and storage, and agricultural and medical advances. Bionanohybrid research also creates new opportunities to investigate microbial communities, synthetic biology, and the origins of life. Metal-sulfide SANs are of particular interest due to their semi-conductor abilities and examples of their generation by multiple bacterial species. This includes bacteria inhabiting metal-rich extreme environments like the Mariana Trench, to bacteria found in the human gut (such as E. coli). While these bacteria are very different, they do share in common the cysteine desulfhydrase enzyme—which plays a crucial role in the formation of metal-sulfide bionanohybrids. Cysteine desulfhydrase converts the amino acid cysteine into sulfide that then reacts with environmental metal cations to create metal sulfide nanoparticles (Raouf Hosseini and Nasiri Sarvi 2015). Under the right conditions (e.g., optimal ratios of metal and cysteine to cell density and growth phase), the resulting nanoparticles remain attached to the surface of the cell, as shown in Fig. 1 (Barnes et al. 2022). Despite the emergence of bionanohybrid applications, very little is known about how the bionanohybrid lifestyle impacts cells. This project aims to uncover some of the fundamental questions regarding bionanohybrid gene expression by analyzing the RNA transcripts from E. coli K-12 cells with different degrees of cadmium sulfide (CdS) SAN coverage. Gene expression studies may reveal fundamental differences between bionanohybrids and uncoated bacteria, potentially informing development of industrially advantageous bacteria strains that can produce more SANs. Gel electrophoresis and/or density gradient centrifugation will be used to separate cells that are uncoated, lightly coated, medium coated, and heavily coated proir to RNA isolation and purification. Scanning electron microscopy will confirm SAN coverage in these different fractions. RNA sequencing will indicate if there are any differences in gene expression between uncoated cells and bionanoybrids, as well as examine if SAN cell coverage has any relationship to gene expression. This research promises to open doors to new applications related to bionanohybrids while expanding our knowledge of microbial biology.

Enhanced removal of dibutyl phthalate in a laccase-mediator system: Optimized process parameters, kinetics, and environmental impact

The persistence and recalcitrance of endocrine-disrupting chemicals (EDCs) in the environment have raised momentous concerns due to their carcinogenic, teratogenic, genotoxic, and cytotoxic effects on humans, animals, and plants. Unarguably, dibutyl phthalate (DBP) is one of the most ubiquitous EDCs because of its bioavailability in water, soil, and atmosphere. This study aims to investigate the efficiency of Agaricus bisporus laccase in the degradation of dibutyl phthalate (DBP) in laccase-mediator system. Here, enhanced removal efficiency was recorded during DBP degradation in laccase-mediator systems than in reaction medium containing laccase only. About 98.85% of 30 mg L−1 DBP was efficiently removed in a medium containing 1.3 U mL−1, 0.045 mM Syringaldehyde (SYR) at incubation temperature 30 aC and pH 5 within 24 h. This finding was further corroborated by the synergistic interplay of the optimal parameters in the laccase-SYR system done using response surface methodology (Box-Behnken Design). Furthermore, the addition of 1.5 mM of metal ions in the laccase-SYR system further promoted the enhanced removal of DBP in the following order: Cr3+> Pb2+> Ca2+> Al3+>Zn2+ > Cu2+. A significant decrease in DBP degradation was observed at higher concentrations of metal ions above 1.5 mM due to the inhibition of laccase active sites. The coefficient of correlation (R2 = 0.9885) recorded in the Lineweaver bulk plot affirmed that the removal efficiencies are highly dependent on DBP concentration in the laccase-SYR system. The Gas-Chromatography Mass Spectrometry (GC-MS) analyses affirmed that the ortho-cleavage due to hydrolysis of DBP in the reaction system led to the formation of two metabolic degradation products (MBP and PA). The phytotoxicity assessment affirmed the detoxified status of DBP after treatment with significant improvement (90 and 91%) in the growth of Lens culinaris and Sorghum bicolor. This is the first report on DBP degradation in the laccase-SYR reaction system, underscoring the unique, eco-friendly, economical, and promising alternative to known conventional methods.

Metal Binding of Alzheimer's Amyloid-β and Its Effect on Peptide Self-Assembly.

ConspectusMetal ions have been identified as key factors modulating the aggregation of amyloid-β peptide (Aβ) implicated in Alzheimer's disease (AD). The presence of elevated levels of metal ions in the amyloid plaques in AD patients supports the notion that the dysfunction of metal homeostasis is connected to the development of AD pathology. Here, recent findings from high- and low-resolution biophysical techniques are put into perspective, providing detailed insights into the molecular structures and dynamics of metal-bound Aβ complexes and the effect of metal ions on the Aβ aggregation process. In particular, the development of theoretical kinetic models deducing different microscopic nucleation events from the macroscopic aggregation behavior has enabled deciphering of the effect of metal ions on specific nucleation processes. In addition to these macroscopic measurements of bulk aggregation to quantify microscopic rates, recent NMR studies have revealed details about the structures and dynamics of metal-Aβ complexes, thereby linking structural events to bulk aggregation. Interestingly, transition-metal ions, such as copper, zinc, and silver ions, form a compact complex with the N-terminal part of monomeric Aβ, respectively, where the metal-bound "folded" state is in dynamic equilibrium with an "unfolded" state. The rates and thermodynamic features of these exchange dynamics have been determined by using NMR relaxation dispersion experiments. Additionally, the application of specifically tailored paramagnetic NMR experiments on the Cu(II)-Aβ complex has been fruitful in obtaining structural constraints within the blind sphere of conventional NMR experiments. This enables the determination of molecular structures of the "folded" Cu(II)-coordinated N-terminal region of Aβ. Furthermore, the discussed transition-metal ions modulate Aβ self-assembly in a concentration-dependent manner, where low metal ion concentrations inhibit Aβ fibril formation, while at high metal ion concentrations other processes occur, resulting in amorphous aggregate formation. Remarkably, the metal-Aβ interaction predominately reduces one specific nucleation step, the fibril-end elongation, whereas primary and surface-catalyzed secondary nucleation mechanisms are less affected. Specific inhibition of fibril-end elongation theoretically predicts an enhanced generation of Aβ oligomers, which is an interesting contribution to understanding metal-Aβ-associated neurotoxic effects. Taken together, the metal binding process creates a metal-bound Aβ complex, which is seemingly inert to aggregation. This process hence efficiently reduces the aggregation-prone peptide pool, which on the macroscopic level is reflected as slower aggregation kinetics. Thus, the specific binding of metals to the Aβ monomer can be linked to the macroscopic inhibitory effect on Aβ bulk aggregation, providing a molecular understanding of the Aβ aggregation mechanism in the presence of metal ions, where the metal ion can be seen as a minimalist agent against Aβ self-assembly. These insights can help to target Aβ aggregation in vivo, where metal ions are key factors modulating the Aβ self-assembly and Aβ-associated neurotoxicity.

Cobalt and nickel separation in aqueous two-phase systems with polyethylene glycol 20,000 and sodium electrolytes

The separation of Co(II) and Ni(II) in aqueous two-phase systems (ATPSs) formed by the polymer polyethylene glycol 20,000 and several sodium electrolytes, coupled with the organic extractant 1-nitroso-2-naphthol was studied. First, the liquid-liquid equilibrium experiments were carried out to describe the phase diagrams of the ATPS. Then, the metal separation efficiency was evaluated considering several factors. It was observed that pH had a great influence on the selective metal chelation. When lowering the pH to 2 and 1 in the system with sodium sulfate, it was possible to suppress the Ni extraction under 5%. These results showed that the differences in the metal chelate stabilities could displace the equilibrium reaction with Ni(II) for selective extraction. In addition, experimental results showed that the interactions between metal cations and the salt anions also determined the separation efficiency. For the system with sodium sulfate (Na2SO4), Ni(II) extraction was suppressed at pH 2, but when sodium citrate (Na3C6H5O7) was used, the suppression occurred at pH lower than 0.5, while sodium tartrate (Na2C4H4O6) and sodium hydrogen phosphate (Na2HPO4) were not suitable for selective extraction. High separation factors of 11,080, 1136, and 3300 were obtained for the aqueous systems with Na2SO4 at pH 2, and pH 1, and Na3C6H5O7 at pH 0.5, respectively. Finally, the extraction at higher metal ion concentrations was tested. When the concentration of 1N2N was 1000 mg/kg, the maximum amount of extracted Co reached about 85 mg/kg within 15 min, which corresponds to complete extraction considering a metal:1N2N ratio of 1:4.

Metal-DNA interactions: Exploring the impact of metal ions on key stages of forensic DNA analysis.

Forensic DNA analysis continues to be hampered by the complex interactions between metals and DNA. Metal ions may cause direct DNA damage, inhibit DNA extraction and polymerase chain reaction (PCR) amplification or both. This study evaluated the impact of metal ions on DNA extraction, quantitation, and short tandem repeat profiling using cell-free and cellular (saliva) DNA. Of the 11 metals assessed, brass exhibited the strongest PCR inhibitory effects, for both custom and Quantifiler Trio quantitation assays. Metal ion inhibition varied across the two quantitative PCR assays and the amount of DNA template used. The Quantifiler Trio internal PCR control (IPC) only revealed evidence of PCR inhibition at higher metal ion concentrations, limiting the applicability of IPC as an indicator of the presence of metal inhibitor in a sample. Notably, ferrous ions were found to significantly decrease the extraction efficiency of the DNA-IQ DNA extraction system. The amount of DNA degradation and inhibition in saliva samples caused by metal ions increased with a dilution of the sample, suggesting that the saliva matrix provides protection from metal ion effects.

Dielectric properties of iPP and aPS nanocomposites with core‐shell particles obtained by treatment in transition metal salt solutions

AbstractThe dielectric properties of nanocomposites based on isotactic polypropylene (iPP) and atactic polystyrene (aPS) obtained by novel, simple, and environmentally friendly treatment technique have been analyzed in this study. The best treatment conditions to obtain nanocomposites with embedded core‐shell particles with enhanced dielectric properties were considered. Treatment of polymer matrices in water solution iron(II)‐chloride had the most pronounced precipitation effect, that was directly related to the appearance of higher transition metal concentrations in the iPP and aPS matrices, in comparison to treatments in the other two transition metal salts, MnCl2 and NiCl2. Relative dielectric constant and loss tangent have been studied in the frequency range from 20 Hz to 9 MHz. Embedded core‐shell nanoparticles (from 15 to 150 nm in diameter) in a very small amount (1.72E‐8 mol/cm3 to 1.17E‐5 mol/cm3) resulted in significant improvement (2.5% up to 9.1%) and stabilization of relative dielectric constant value toward higher frequencies and also lowering loss tangent in compare to starting polymer matrices. These properties indicate that materials obtained with the presented treatment technique can be applied as microelectronic packing and with further development of the method in order to obtain a higher concentration of metal ions as energy storage devices.

Hydrogeochemical Responses of MTMS-Coated Capillary Cover under Heavy Rainfalls

To limit the oxidation of waste rocks that originates from mining operations and the subsequent leaching of acidic solutions with high concentration of metal ions, a tailing–rock–clay triple layer capillary cover system was developed to prevent rainwater infiltration in humid climatic regions. The fine grained soil (FGS) layer consists of mine tailing and a hydrodesulfurization (HDS) clay from waste-water treatment with a 95:5 mass ratio. The coarse grained soil (CGS) layer consists of local waste rock granules with a size of 1–10 mm. Methyltrimethoxysilane (MTMS), an oxidation-inhibiting agent with strong hydrophobicity, was passivated on the rock grains to further reduce water infiltration and leaching of metal ions. Prototype-scale column tests were performed with matric suction and water content measurements under 680 min rainfall of 60 mm/h, the most severe annual precipitation case scenario for the Dexing Copper Mine (Jiangxi Province, China, 28.95° N, 117.57° E, humid climate). Both the uncoated and the coated covers exhibited zero leakage throughout the experiment. The passivation on rock granules in the coated cover increased the water entry value (WEV) of the CGS layer to −0.56 kPa. This led to a 15 mm water storage increment in the overlain FGS layer as compared to that in the uncoated cover, and induced lateral drainage (5% of the precipitation) in the FGS layer, which was not overserved in the uncoated cover. The concentrations of the leached Fe2+, Cu2+, Zn2+, Mn2+ and Mg2+ cations drained from the CGS layers of the uncoated cover were 0, 0.4, 0.8, 73.5, and 590.5 mg/L, which are all within the regulation limits of industrial discharge water standards. The concentrations of Cu2+, Mn2+ and Mg2+ cations drained from the coated CGS layer were reduced by 1–3 orders of magnitude. The abovementioned laboratory studies validated the water retention and leaching prevention abilities of the proposed three-layer capillary covers and the MTMS coating, which hold promises in engineering applications.

Degradation behaviour of fresh and pre-used ethanolamine

The oxidative degradation of previously used ethanolamine from three different CO2 capture pilot plants was studied in a laboratory-scale degradation setup. Different solvents behave differently under the same experimental conditions, indicating that different solvent contaminants, resulting from different operational conditions, can act either stabilising or destabilising under oxidising conditions. Some ionic compounds in the solvent seem beneficial to amine stability under oxidising conditions, while the presence of some inorganic compounds appears to have a negative effect on the stability of the solvent. The most stable pre-used ethanolamine solutions were those that contained the highest total concentrations of heat-stable salts, calcium, sodium, sulphur, potassium, and silicon. These solutions were previously used for CO2 capture from a lignite-fired power plant and a waste-to-energy plant. The least stable amine solution had a higher concentration of metal ions like chromium, magnesium, and zinc, making these suspects of deteriorating solvent stability.

A surface metal ion-modified 3D-printed Ti-6Al-4V implant with direct and immunoregulatory antibacterial and osteogenic activity.

The high concentration of antibacterial metal ions may exhibit unavoidable toxicity to cells and normal tissues. The application of antibacterial metal ions to activate the immune response and induce macrophages to attack and phagocytose bacteria is a new antimicrobial strategy. Herein, 3D-printed Ti-6Al-4V implants modified by copper, and strontium ions combined with natural polymers were designed to treat implant-related infections and osseointegration disorders. The polymer-modified scaffolds rapidly released a large amount of copper and strontium ions. During the release process, copper ions were employed to promote the polarization of M1 macrophages, thus inducing a proinflammatory immune response to inhibit infection and achieve the immune antibacterial activity. Meanwhile, copper and strontium ions promoted the secretion of bone-promoting factors by macrophages, induced osteogenesis and showed immunomodulatory osteogenesis. This study proposed immunomodulatory strategies based on the immunological characteristics of target diseases and provided ideas for the design and synthesis of new immunoregulatory biomaterials.

The influence of transition metal ions on the oxidation of kraft pulp using hydrogen peroxide under mildly acidic conditions

Abstract Oxidation of kraft pulp using hydrogen peroxide under mild acidic conditions can be applied in order to obtain new functionality of the fibres, in the form of carbonyl groups. The hydrogen peroxide concentration must, however, be higher than consumed by the oxidation reactions meaning that the liquid must be recirculated to fully utilize the hydrogen peroxide. This paper investigates the consequences of recirculation of the oxidation liquor. It was found that recirculation results in an accumulation of ions of transition metals (copper, iron and manganese) in the oxidation liquor. The transition metal ions are known for catalytic decomposition of hydrogen peroxide, producing radicals which may react with carbohydrates, forming carbonyl groups as well as causing carbohydrate degradation. This was confirmed through the recirculation of oxidation liquor as well as through controlled addition of transition metals. At high transition metal ion concentration the reactions were fast and a severe degradation of carbohydrates was observed, accompanied by a rapid hydrogen peroxide consumption. The consequence of this, in an industrial context, is that the concentration of metal ions must be carefully controlled in order to add functionality to the cellulose without causing excessive degradation of carbohydrates or consumption of hydrogen peroxide.

Altering the Alkaline Metal Ions in Lepidocrocite-Type Layered Titanate for Sodium-Ion Batteries

The relatively large ionic radius of the Na ion is one of the primary reasons for the slow diffusion of Na ions compared to that of Li ions in de/intercalation processes in sodium-ion batteries (SIBs). Interlayer expansion of intercalation hosts is one of the effective techniques for facilitating Na-ion diffusion. For most ionic layered compounds, interlayer expansion relies on intercalation of guest ions. It is important to investigate the role of these ions for material development of SIBs. In this study, alkali-metal ions (Li+, Na+, K+, and Cs+) with different sizes were intercalated into lepidocrocite-type layered titanate by a simple ion-exchange technique to achieve interlayer modulation and those were then evaluated as anode materials for SIBs. By controlling the intercalated alkaline ion species, basal spacings of layered titanates (LTs) in the range of 0.68 to 0.85 nm were obtained. Interestingly, the largest interlayer spacing induced by the large size of Cs did not yield the best performance, while the Na intercalated layered titanate (Na-ILT) demonstrated a superior performance with a specific capacity of 153 mAh g-1 at a current density of 0.1 A g-1. We found that the phenomena can be explained by the high alkaline metal ion concentration and the efficient utilization of the active sites in Na-ILT. The detailed analysis indicates that large intercalating ions like Cs can hamper sodium-ion diffusion although the interlayer spacing is large. Our work suggests that adopting an appropriate interlayer ion species is key to developing highly efficient layered electrode materials for SIBs.

Probing Cell-Surface Interactions in Fungal Cell Walls by High-Resolution 1 H-Detected Solid-State NMR Spectroscopy.

Solid-state NMR (ssNMR) spectroscopy facilitates the non-destructive characterization of structurally heterogeneous biomolecules in their native setting, for example, comprising proteins, lipids and polysaccharides. Here we demonstrate the utility of high and ultra-high field 1 H-detected fast MAS ssNMR spectroscopy, which exhibits increased sensitivity and spectral resolution, to further elucidate the atomic-level composition and structural arrangement of the cell wall of Schizophyllum commune, a mushroom-forming fungus from the Basidiomycota phylum. These advancements allowed us to reveal that Cu(II) ions and the antifungal peptide Cathelicidin-2 mainly bind to cell wall proteins at low concentrations while glucans are targeted at high metal ion concentrations. In addition, our data suggest the presence of polysaccharides containing N-acetyl galactosamine (GalNAc) and proteins, including the hydrophobin proteins SC3, shedding more light on the molecular make-up of cells wall as well as the positioning of the polypeptide layer. Obtaining such information may be of critical relevance for future research into fungi in material science and biomedical contexts.

Simultaneous detection of Lead and Cadmium using a composite of Zeolite Imidazole Framework and Reduced Graphene Oxide (ZIF-67/rGO) via electrochemical approach

Present work reports the application of a composite of ZIF-67/rGO for the simultaneous detection of traces of lead and cadmium via square wave anodic stripping voltammetry (SWASV) technique. For this, graffoil sheets were modified with synthesized composite for the electrode fabrication [(ZIF-67/rGO)/Graffoil] for its use in sensing studies. The SWASV response of (ZIF-67/rGO)/Graffoil electrode was optimized against deposition potential (-1.0 V) and time (350 s), required for the accumulation of metal ions onto the sensor electrode. The performance of the sensing electrode was then evaluated for lead (Pb<sup>2+</sup>) and cadmium (Cd<sup>2+</sup>) ions at various concentrations. The sensor displayed linear response in a wide concentration range of 5-100 ppb. The peak current of the electrode was found to be shifted towards the higher potential at higher metal ion concentrations. Based on the response measured, the limit of detection (LOD) of the fabricated sensor has been estimated and found to be 5 and 2.93 ppb for Pb<sup>2+</sup> and Cd<sup>2+</sup> ions, respectively. The results obtained revealed good specificity of the proposed sensor towards Pb<sup>2+</sup> and Cd<sup>2+</sup> ions in the co-presence of several other ions. In addition, the sensor exhibited good reproducibility with a relative standard deviation (RSD) of ~2% for both Pb<sup>2+</sup> and Cd<sup>2+</sup> ions.

Experimental and simulation study on the capture and separation of CO2/CH4 by alkali metal complex ionic liquid

Solutions of [Bmim][BF4] ionic liquid (IL) mixed with three alkali metal tetrafluoroborate salts, i.e. LiBF4, NaBF4 and KBF4, were used to capture and separate CO2/CH4 at 303.15, 313.15 and 323.15 K under different pressures ranged from 500 to 3000 kPa. CO2 solubility in three alkali metal doped solutions decreases with the increase of temperature and decreasing pressure. High concentration of alkali metal salts does not show a very improvement for CO2 absorption, and even reduce CO2 capture instead in the presence of high concentration of LiBF4 in ionic liquid. Unexpectedly, KBF4 has the least solubility in [Bmim][BF4] and LiBF4 dissolved most in [Bmim][BF4] ionic liquid. On the contrary, the solubility of metal complex ionic liquids to CH4 decreased after adding alkali metal salts of any concentration. 0.01 mol·L−1 KBF4-IL showed the best CO2/CH4 solubility selectivity at 303.15 K, up to 54.5. On a basis of Quantum chemical calculations, binding energies between metal-doped ionic liquids and CO2/CH4 were calculated, following an order of KBF4-IL-CO2 > NaBF4-IL-CO2 > LiBF4-IL-CO2 and LiBF4-IL-CH4 > NaBF4-IL-CH4 > KBF4-IL-CH4, which is consistent with the experimental results. [BF4]− anions are approaching the metal ions and the larger metal cations, i.e. Na+ and K+, have longer distances with the anions than Li+, which explains the reason of reduced CO2 solubility when Li+ becomes more. Generally, high concentration of metal ions in ionic liquids are inferior for CO2 absorption because of the association of MBF4 with the ionic liquid. Therefore, the results of this paper can lay a theoretical foundation for CO2/CH4 capture separation.

Strategies for anti-oxidative stress and anti-acid stress in bioleaching of LiCoO2 using an acidophilic microbial consortium.

High metal ion concentrations and low pH cause severely inhibit the activity of an acidophilic microbial consortium (AMC) in bioleaching. This work investigated the effects of exogenous spermine on biofilm formation and the bioleaching efficiency of LiCoO2 by AMC in 9K medium. After the addition of 1mM spermine, the activities of glutathione peroxidase and catalase increased, while the amount of H2O2, intracellular reactive oxygen species (ROS) and malondialdehyde in AMC decreased. These results indicated that the ability of AMC biofilm to resist oxidative stress introduced by 3.5g/L Li+ and 30.1g/L Co2+ was improved by spermine. The activity of glutamate decarboxylase was promoted to restore the intracellular pH buffering ability of AMC. Electrochemical measurements showed that the oxidation rate of pyrite was increased by exogenous spermine. As a result, high bioleaching efficiencies of 97.1% for Li+ and 96.1% for Co2+ from a 5.0% (wv-1) lithium cobalt oxide powder slurry were achieved. This work demonstrated that Tafel polarization can be used to monitor the AMC biofilm's ability of uptaking electrons from pyrite during bioleaching. The corrosion current density increased with 1mM spermine, indicating enhanced electron uptake by the biofilm from pyrite.

Changes in the enzymes, amino acids, metal ions and flavor profile during fermentation of African locust bean seeds ‘Parkia biglobosa’ to Daddawa

Daddawa/iru, a product of African locust bean (Parkia biglobosa) seeds, is widely used as food condiment by many tribes in West Africa. This study aimed to determine some of the changes which occur during the microbial fermentation of African locust bean seed. The daily changes in pH, amylase, lipase and protease secretion were monitored. Changes in amino acid concentration, mineral ion composition were also monitored; the presence of hydrocarbons and volatile flavor compounds were also determined. The pH increased throughout fermentation and was above 8.5 by 96 h fermentation. Enzyme production was highest after 48 h fermentation. The highest increase in amino acid concentration was observed after 72 h fermentation. The essential amino acids which increased after 72 h fermentation include arginine (48.8%), threonine (25.2%), valine (24.8%), and methionine (20.0%), histidine (10.3%), isoleucine (19.2%), leucine (15.9%), lysine (15.24%), phenylalanine (14.9%), and tryptophan (12.5%). A higher metal ion concentration was observed before fermentation (0 h) than during or after fermentation of the locust bean seeds. Various hydrocarbons, fatty acids, esters and alcohols were observed at different stages of the fermentation.

Influence of pollutant concentration on the separation efficiency of chelating membranes for removing simultaneously metal ions and proteins from simulated industrial wastewater

AbstractBACKGROUNDA novel chelating membrane was fabricated for removing simultaneously metal ions (Cd2+, Pb2+ and Cu2+) and proteins (bovine serum albumin and lysozyme) from simulated industrial effluent. The purpose of the study was to investigate the influence of pollutant concentration on the separation efficiency of the chelating membrane for pollutants.RESULTS(i) The removal of metal ions mainly relies on the adsorption capacity of the chelating membrane, and seems to be independent of the concentration of protein. (ii) The retention of proteins depends mainly on their concentration in solution. (iii) When the wastewater contains high concentration of metal ions (C = 100 mg L−1) and low concentration of proteins (C = 10 mg L−1), the chelating membrane exhibits overall poor separation performance, with a low ion removal efficiency (55–70%) and a low protein rejection rate (ca 60%). (iv) When the wastewater contains low concentration of metal ions (C = 10 mg L−1) and high concentration of proteins (C = 100 mg L−1), the chelating membrane exhibits overall excellent separation performance, with ion removal rates of higher than 90% (except for Cd2+) and protein rejection rates of higher than 90%.CONCLUSIONSThe separation efficiency of the chelating membrane for metallic and organic pollutants greatly depends on the pollutant concentration in the wastewater. This study provides a theoretical basis for membrane technology for removing simultaneously heavy metals and organic pollutants in wastewater. © 2022 Society of Chemical Industry (SCI).

Heterologous expression and characterization of a novel lytic polysaccharide monooxygenase from Natrialbaceae archaeon and its application for chitin biodegradation

Lytic polysaccharide monooxygenases could enhance the enzymatic conversion of recalcitrant polysaccharides by glycoside hydrolases. This study reports the expression and identification of a novel AA10 LPMO from Natrialbaceae archaeon, named NaLPMO10A, as a C1 oxidizer of chitin. The optimal temperature and pH for NaLPMO10A activity were 40 °C and 9.0, respectively, and NaLPMO10A exhibited high thermostability and pH stability under alkaline conditions. NaLPMO10A was also highly tolerant and stable when treated with high concentration of metal ions (1 M). Moreover, metal ions (Na+, K+, Ca2+ and Mg2+) significantly promoted NaLPMO10A activity and improved the saccharification efficiency of chitin by 22.6%, 45.9%, 36.7% and 53.9%, respectively, compared to commercial chitinase alone. Together, the findings of this study fill a gap in archaeal LPMO research, and for the first time demonstrate that archaeal NaLPMO10A could be a promising enzyme for improving saccharification under extreme condition, with potential applications in biorefineries.