Mild pH Conditions Research Articles

Preliminary Study of LiCoPO4 cathode material synthesis for LiCoPO4/Graphite Cell

<p>Nowadays, the race towards a high-performance Li-ion batteries discovery for energy storage has become an interesting technological challenge. New or improved Li-ion battery cathodes have been developed relentlessly in this decade. LiCoPO<sub>4</sub> (LCP) is a cathode material that allow a battery to operate at high voltage which resulted a high energy density battery. The presence of strong P-O bond adds a thermal stability feature to LIB cells. In this study, a LiCoPO<sub>4</sub> material were prepared by precipitation of Co<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> (CP) followed by high temperature Li insertion. H­<sub>3</sub>PO<sub>4</sub> were used as the phosphate source. The crystallization or precipitation of CP can only be achieved under mild pH condition, which can be controlled using sodium hydroxide. XRD, SEM and FTIR analysis were used to characterize the final product. The as-obtained LCP were applied as cathode material while graphite was used as the counter anode. The cell can deliver a charge-discharge capacity at a voltage of 2.0-4.95 V. This preliminary can be a groundwork toward the commercialization of LCP based Li-ion batteries for high duty application.</p>

Development of Mild Chemical Catalysis Conditions for m1A-to-m6A Rearrangement on RNA.

The conversion of N1-methyladenosine (m1A) to N6-methyladenosine (m6A) on RNA is an important step for both allowing efficient reverse transcription read-though for sequencing analysis and mapping modifications in the transcriptome. Enzymatic transformation is often used, but the efficiency of the removal can depend on local sequence context. Chemical conversion through the application of the Dimroth rearrangement, in which m1A rearranges into m6A under heat and alkaline conditions, is an alternative, but the required alkaline conditions result in significant RNA degradation by hydrolysis of the phosphodiester backbone. Here, we report novel, mild pH conditions that catalyze m1A-to-m6A arrangement using 4-nitrothiophenol as a catalyst. We demonstrate the efficient rearrangement in mononucleosides, synthetic RNA oligonucleotides, and RNAs isolated from human cell lines, thereby validating a new approach for converting m1A-to-m6A in RNA samples for sequencing analyses.

Click Bioconjugation: Modifying Proteins Using Click-Like Chemistry.

Bioconjugation deals with the chemical modification of proteins. The reactions used exploit either the intrinsic chemical reactivity of the biomolecule or introduce functionalities that can then be subsequently reacted without interfering with other functional groups of the biological entity. Perfectly selective, high yielding chemical transformations are needed that can be run in aqueous environment under mild pH conditions. Requirements that have an obvious overlap with the definition of click chemistry. This review shows a selection of successfully applied click-type reactions in bioconjugation as well as some recent developments to broaden the chemical toolbox to meet the challenge of selective, bioorthogonal modification of biomolecules.

Incorporation of manganese carbonyl sulfide ((Mn2S2 (CO)7) and mixed metal oxides-decorated reduced graphene oxide (MnFeCoO4/rGO) as a selective anode toward efficient OER from seawater splitting under neutral pH conditions

Applying non-noble metal-based electrocatalysts toward efficient and cost-effective oxygen evolution reaction (OER) from seawater under mild pH conditions are of paramount importance for advancing green hydrogen production through renewable energy. Amongst several predicaments, the presence of chloride ions in seawater competes with the OER as a more kinetically facile anodic reaction that results in the formation of toxic chlorine products. Herein, we propose a novel material combination, which exhibits higher OER activity and selectively over chlorine evolution reaction (CER) during simulated saline water electrolysis under neutral pH conditions. The proposed hybrid nanocomposite system, based on electroactive mixed metal oxides-decorated reduced graphene oxide (MnFeCoO4/rGO) which is incorporated with manganese carbonyl sulfide (Mn2S2(CO)7), are fabricated by a single-step hydrothermal technique. Benefiting from their heterogeneous interfaces, lower charge transfer resistance, and higher electrochemical (EC) and BET surface area, the hybrid graphene MnFeCoO4/Mn2S2(CO)7 nanocomposite (HGNC) yields the best performance among various options towards OER from pH-neutral seawater (1 M PB + 0.6 M NaCl; pH 7.0) electrolysis, with small Tafel slope of 74.1 mVdec−1 and correspondingly low overpotential of ∼310 mV to achieve a current density of 10 mAcm−2. The high activity at the aforementioned current density allows for overpotential operation below the minimum thermodynamic requirement needed for activating CER, thus ruling out progression of CER. Further, benefiting from the strong coupling effect between the MnFeCoO4/Mn2S2(CO)7 species and the graphene support, appreciable stability was achieved for 15 h to deliver steady-state current stability without obvious decay, which demonstrating that HGNC is a promising candidate as an OER electrocatalyst for neutral seawater electrolysis.

Importance of laccase enzyme and triiodide for gold leaching from silicate ore by marine bacterium Acinetobacter sp.

The effect of enzymes and other substances on gold bioleaching was investigated. Acinetobacter sp. had a higher gold leaching performance than two strains of Vibrio sp. because it grew well in nutrient broth (NB) medium containing potassium iodide (KI) and produced high levels of both laccase and triiodide (I3-). Under two-step condition of Acinetobacter sp. in NB medium containing KI 10.9 g·L−1 and 1% (w/v) alkali lignin had the highest efficiency in gold leaching. Plausible mechanisms of gold bioleaching involved in biogenic iodide-iodine lixiviant and laccase reaction mechanisms. Laccase produced by Acinetobacter sp. could directly oxidize insoluble gold to soluble gold and also increase iodide oxidation. Afterward, the gold can be oxidized completely in the biogenic iodide-iodine lixiviant to form gold (I) diiodide [AuI2]- or gold (III) tetraiodide [AuI4]-. Interestingly, it was found that silicate ore could act as an inducer of laccase production. Furthermore, alkali lignin addition could increase gold bioleaching due to it can be used as a substrate for laccase production. Therefore, the two-step condition of Acinetobacter sp. could be applied in gold leaching under mild alkaline pH conditions. The advantage of this technology was safer and more environmentally friendly than cyanidation as a conventional extraction.

Effects of Aronia polyphenols on the physico-chemical properties of whey, soy, and pea protein isolate dispersions

Bioactive compounds including polyphenols (PP) have been observed to naturally form non-covalent complexation interactions with proteins under mild pH and temperature conditions, affecting protein structures and functionality. Previously, addition of Aronia berry PP to liquid dispersions containing whey protein isolate (WPI) and sucrose was found to alter characteristics including viscosity, surface tension, and particle sizes, with changes being attributed to protein-PP interactions. In this study we aimed to investigate whether Aronia PP would interact with soy and pea protein isolates (SPI and PPI, respectively) to a similar extent as with WPI in liquid protein-sucrose-PP mixtures. We hypothesized that formulations containing PPI (comprised of larger proteins) and hydrolyzed SPI (containing more carboxyl groups) may exhibit increased viscosities and decreased aggregate sizes due to enhanced protein-PP interactions. Concentrated liquid dispersions of varied ratios of protein to sucrose contents, containing different protein isolates (WPI, SPI, and PPI), and varied Aronia PP concentrations were formulated, and physical properties were evaluated to elucidate the effects of PP addition. PP addition altered physical characteristics differently depending on the protein isolate used, with changes attributed to protein-PP interactions. SPI and PPI appeared to have higher propensities for PP interactions and exhibited more extensive shifts in physical properties than WPI formulations. These findings may be useful for practical applications such as formulating products containing fruit and proteins to obtain desirable sensory attributes.Graphical abstract

Advances in sustainable enzymatic scouring of cotton textiles: Evaluation of different post-treatments to improve fabric wettability

Raw cotton fabrics contain natural impurities (fats, waxes, pectins, and proteins), which impart hydrophobic nature and interfere with textile dyeing. Typically, these noncellulosic impurities are removed by alkaline scouring with hot aqueous sodium hydroxide. As a greener alternative with reduced environmental impact, enzymes can be used to improve cotton hydrophilicity and the quality of fabrics. Thus, this study aimed to establish a roadmap for bioscouring of knitted cotton fabrics using a commercial pectinase preparation under mild conditions of pH and temperature. Pectate lyase (1–10 g L−1) was applied for 30 min at 55 °C at optimum pH 8.5, evaluating different post-treatments with varying temperature and surfactant concentration. The treated samples were characterized in terms of weight loss, water absorption, pectin content, whiteness index, and FTIR spectra. A high level of cleaning was achieved, with an efficacy comparable to conventional alkaline scouring. It was possible to increase the wettability of the textile article with a reduction in fiber damage and in the consumption of energy, water, and chemicals. Low surfactant concentration (0.2 g L−1) and 70 °C washing temperature in the post-washing step were found sufficient to aid in the removal of waxes and fats from the cotton surface after bioscouring and were adequate to achieve high hydrophilicity at low weight loss, unlike other bioscouring studies that used temperatures equal or higher than 80 °C. Results clearly proved that the efficiency of bioscouring to achieve suitable wettability of knitted cotton fabrics depends essentially on an effective post-washing step and the selected conditions, which impact the sustainability and economic viability of the whole process.

Magnetic Graphene Oxide as a Carrier for Lipases Immobilization: An Approach for Hydrolysis of Olive Oil Emulsion

The use of lipases in industrials processes has increased due to its ability to catalyze total or partial hydrolysis reactions of fatty acids. However, due to the difficulty of isolation and purification of lipases, as well as its separation from the reaction medium, it becomes an expensive input. In this study, graphene oxide was used as carrier for enzymes. The magnetic properties of the carrier were obtained through decoration with magnetic iron oxide nanoparticles on graphene oxide surface.XRD was used to elucidate the structure and morphology of the compounds obtained. By measuring hydrolytic activity, it was possible to determine the optimum pH and temperature for three different types of immobilized lipases, being 37 °C and pH 8 (porcine pancreatic lipase), 50 °C and pH 6 (Candida rugosa lipase), and 40 °C and pH 9 (Aspergillus niger lipase). The enzymatic recovery test, during five minutes each, showed the immobilized porcine pancreatic lipase can be recycled six times without significant loss of catalytic activity. It was confirmed the efficiency of the magnetic graphene oxide as a carrier for different lipases allowing its use for transesterification process in mild temperature and pH conditions.

Encapsulant-bioactives interactions impact on physico-chemical properties of concentrated dispersions

Occasionally, bioactive ingredients desired for encapsulation (such as polyphenols) naturally interact with the structure-forming food components intended for their protection and delivery. Non-covalent protein-polyphenol conjugation interactions have been reported to occur naturally under mild pH and temperature conditions, causing changes to protein structures and consequent functionality. Highly concentrated liquid dispersions of varied solids contents, ratios of whey protein isolate (WPI) to sucrose contents, and Aronia berry polyphenols contents were formulated and analyzed to determine potential effects of protein-polyphenol conjugation in the system on the physical properties of dispersions. Dispersions were characterized by rheological measurements, flow testing, particle size analysis, centrifuge separation, and drop sizes produced, and microstructures were visualized with optical light microscopy. Addition of polyphenols was found to alter dispersions physical characteristics including increased viscosity and surface tension and reduced particle size of dispersions, with changes being attributed to conjugation interactions between proteins and polyphenols. • Aronia extract altered viscosity, surface tension, and particle size of dispersions. • Changes to dispersions were attributed to protein-polyphenol interactions. • Colored precipitates after centrifugation indicated protein-polyphenol conjugation. • Diameters of solid drops significantly increased upon addition of Aronia to feeds.

Understanding ozone generation in electrochemical cells at mild pHs

In this work, the production of ozone at mild pH conditions using a commercial electrochemical PEM cell CONDIAPURE Ⓡ is evaluated, at once a phenomenological model is proposed to understand the basis of the processes that occur inside the cell. At these pH conditions, the production of ozone can be explained from the oxidation of water, while the decomposition of ozone is found to be extremely important to explain the global experimental behavior observed. Not only is this decomposition a chemical but also an electrochemically assisted process which, in turn, can be related to the production of other oxidants in the cell which interact with ozone behaving as predators. The model formulated explains and satisfactorily reproduces the influence of the operation mode, the current intensity applied and presence and destruction of organics, with regression coefficients (r2) ranging from 0.88 to 0.99, helping to understand how the production of ozone should be promoted during electrochemical processes.

Performance study on adsorptive removal of acetaminophen from wastewater using silica microspheres: Kinetic and isotherm studies

Owing to the global industrialization, a new generation of pharmaceutical pollutants with high toxicity and persistency have been detected. In the present study, silica microspheres, a promising adsorbent has been employed to investigate the extent of removal of prevalent therapeutic acetaminophen, an emerging micropollutant, from wastewater in isolated batch experiments. The BET surface area of the adsorbent was 105.46 m2/g with a pore size of 15 nm. Characterization of adsorbent by scanning electron microscopy analysis revealed the microparticulate nature with a 15 ± 5 μm particle size. Optimization of reaction parameters for enhanced assimilative removal of pollutants was performed and the highest adsorption of 96.7% of acetaminophen with an adsorption capacity of 89.0 mg/g was observed upon contact time of only 30 min. Mild process conditions of pH 5.0, 20 ppm of acetaminophen, temperature of 303 K, and 100 ppm sorbent concentration further aided in the removal process. Obtained data were best corresponded with the Freundlich isotherm (n = 2.685), indicating highly favorable adsorption. Acetaminophen adsorption kinetics obeyed the pseudo second order and feasible energetic changes were yielded through the thermodynamic analysis. Silica microspheres recovery carried out through a single-step desorption process had a 99.14% retrieval ability.

Sustainable Aqueous Phase Separation membranes prepared through mild pH shift induced polyelectrolyte complexation of PSS and PEI

pH shift induced Aqueous phase separation (APS) is a novel and more sustainable water-based approach to create microfiltration, ultrafiltration, and nanofiltration membranes. APS allows for control over membrane pore size and structure in ways analogous to traditional non-solvent induced phase separation (NIPS). Unfortunately, existing APS approaches require extreme pH shifts (from pH 14 to pH 1) to obtain successful membranes, limiting their applicability for large scale production. Here we demonstrate that APS membranes, with tunable pore sizes ranging from ~80 nm to dense nanofiltration type, can be prepared using a mild pH shift (pH 12 to pH 4) based on the complexation of poly(styrene sulfonate) (PSS) and branched polyethyleneimine (PEI) in acetate buffer coagulation baths. The molecular weight of PEI, the concentration and the pH value of the buffer solution, and the concentration of glutaraldehyde cross-linking agent were systematically varied to control and optimize the membrane fabrication conditions. It was found that tight nanofiltration membranes having a molecular weight cut-off of ~200 g mol−1 and excellent salt (97% MgCl2) and micropollutant retentions (~96%) could be prepared alongside ultra/microfiltration type membranes with an average pore size of ~60 nm. These results indicate that APS membranes with tunable pore sizes can be prepared under mild pH conditions with excellent control over separation properties.

Selective electrochemical hydrogenation of furfural to 2-methylfuran over a single atom Cu catalyst under mild pH conditions

Furfural can be electrochemically hydrogenated to 2-methylfuran in mild conditions with high selectivity using a catalyst containing single atom copper active sites and oxophilic phosphorus dopants.

Activated biochar supported iron-copper oxide bimetallic catalyst for degradation of ciprofloxacin via photo-assisted electro-Fenton process: A mild pH condition

Iron-copper oxide impregnated NaOH-activated biochar (FeCu/ABC) was successfully fabricated through simple pyrolysis of activated biochar, followed by the impregnation method. The catalytic activity of the bimetallic catalyst was investigated for ciprofloxacin (CIP) degradation through a heterogeneous photo-electro-Fenton process at natural pH. The characterization analyses verified the structural suitability of as-synthesized FeCu/ABC to act as a catalyst for treating CIP. The effects of operating parameters such as Cu/Fe mass ratio, initial pH, catalyst dosage, electrical current and initial concentration of CIP were carefully studied. Complete removal of CIP concentrations of up to 45 mg/L was obtained after 2 h of reaction at Cu/Fe mass ratio of 1:1, pH 5.8, catalyst dosage of 1 g/L, and electrical current of 400 mA. CIP decay followed pseudo-first-order reaction kinetics. The synthesized heterogeneous catalyst exhibited a remarkable catalytic activity at natural pH (92 % mineralization of CIP after 8 h under the optimum conditions). The prepared catalyst possessed great stability and structural integrity for 5 consecutive runs. Furthermore, from a practical point of view, the catalyst exhibited an acceptable performance by oxidizing CIP dissolved in various water matrices such as tap water, river water, and a real sample of wastewater. The possible CIP degradation pathways were also proposed based on the identification of different oxidation by-products.

Efficient Electrochemical Conversion of CO2 to CO Using a Cathode with Porous Catalyst Layer under Mild pH Conditions

Electrochemical conversion of CO2 into fuels or chemical feedstocks is one of the most promising methods for solving the problems of both fossil fuel depletion and global warming. Herein, we report...

Engineered hybrid nanozyme catalyst cascade based on polysaccharide-enzyme-magnetic iron oxide nanostructures for potential application in cancer therapy

An array of new nanomaterials have been designed to mimic the catalyst characteristics of natural enzymes (termed "nanozymes"), which connects an essential bridge between nanotechnology and biomedical science. Thus, the research on nanozymes has increased dramatically and a new multidisciplinary field has emerged in recent years named nanozymology. Magnetic iron oxide nanoparticles (e.g., Fe2O3 and Fe3O4, MIONs) have revealed to perform an enzyme-like activity with pH-dependent behavior. These nanozymes can catalytically decompose H2O2 into products (e.g., H2O and O2) under mild pH conditions mimicking enzyme-like bioactivity. More importantly, under mildly acidic conditions, they can use H2O2 as the substrate for producing highly toxic reactive oxygen species (ROS) through the generation of hydroxyl radicals (OH), displaying peroxidase-like activity. Therefore, here we designed and developed a novel class of hybrid nanocatalysts based on the conjugation of GOx (natural enzyme) and MIONs (inorganic nanozyme) stabilized by a biocompatible polymer shell of carboxymethyl cellulose. They created supramolecular vesicle-like nanostructures that were tested for killing brain cancer cells (U-87 MG) in vitro, where they proved anticancer activity attributed to ferroptosis-induced cell death. These hybrid nanostructures performed as a cascade of integrated nanocatalysts: a) GOx worked as the starting catalyst, where the glucose in the medium generated H2O2; b) next, H2O2 was catalyzed by the downstream MION nanozymes (Fe3O4) via Fenton-like reactions releasing toxic species (ROS), which caused the cancer cell death. Remarkably, this nanozyme-induced cell death was more pronounced in brain cancer cells ascribed to the more acidic microenvironment than on healthy cells.

Self-assembly of pentapeptides into morphology-adaptable nanomedicines for enhanced combinatorial chemo-photodynamic therapy

The persistent morphology of conventional delivering systems limits their capability to further simultaneously optimize pharmokinetics and overcome the physiological delivering barriers. To address this challenge, here we report nanomedicines delivered by morphology-adaptable platforms for enhanced drug delivering and combinatorial chemo-photodynamic therapeutic efficacy. The nanomedicines were created by co-assembling a pentapeptide (AmpF) containing a 4-amino proline (Amp) with its two derivatives CPT-AmpF and IR820-AmpF, which are functionalized by drug camptothecin (CPT) and photosensitizer new indocyanine green IR820, respectively. The resulting nanomedicines formed superhelices and nanoparticles under neutral and mild acidic pH conditions. Cellular experiments revealed that the nanomedicines were up-taken by breast cancer cells via an endo-/lysosome-mediated mechanism, thus allowing the nanomedicines to undergo a reversible superhelice-nanoparticle morphological transition during the delivering pathway. Therefore, the superhelcial morphology of the nanomedicines prolonged blood circulation and tumor retention, whereas the transformed nanoparticles facilitated penetration and accumulation at tumor sites. Compared to the morphology-persistent counterparts, the improved delivering efficiency of the adaptable nanomedicines resulted in the enhanced combinatorial chemo-photodynamic therapy against breast tumors, thus potentially leading to a facile and versatile strategy for drug delivery and paving the way toward new-generation nanomedicines in the future.

Silver-organic coordination networks for magnetic solid-phase extraction of trihalomethanes from environmental water samples: experimental and theoretical calculation study

Trihalomethanes (THMs) are the primary toxic and carcinogenic byproducts during disinfection of drinking water. THMs have been frequently detected in water body and posed a huge threat to human health. Thus, analyzing the trace levels of THMs in an accurate and rapid method for water quality monitoring is important. In this paper, silver-based organic coordination networks (Ag-OCN) were fabricated with different diameters under mild pH condition. After modification with magnet, Fe3O4 @ Ag-OCN as extractant was applied to the magnetic solid-phase extraction of THMs from water samples. Gas chromatography-tandem mass spectrometry was used for sample quantification and detection. The magnetic extractant displayed good linearity in the range of 0.03–10 ug/L, low limits of detection (1.41–10.13 ng/L), and good reproducibility (relative standard deviations < 6.31%). Moreover, density-functional theory (DFT) calculation was also applied to investigate the possible interaction mechanism. Combining the experimental data with theoretical calculation, results showed that Fe3O4 @ Ag-OCN was a potential magnetic material for the enrichment and extraction of formed THMs at trace levels from water samples.

Structure and Bioactive Properties of Novel Textile Dyes Synthesised by Fungal Laccase.

Novel sustainable processes involving oxidative enzymatic catalysts are considered as an alternative for classical organic chemistry. The unique physicochemical and bioactive properties of novel bio-products can be obtained using fungal laccase as catalyst. Among them are textile biodyes synthesised during oxidation of substrates belonging to the amine and methoxy organic derivatives. The process of synthesis occurs in mild conditions of pH, temperature, and pressure, and without using harmful oxidants. The effect of fungal laccase activity on the substrates mixture transformation efficiency was analysed in terms of antimicrobial dye synthesis on a large scale. Three new phenazine dyes, obtained in the presence of laccase from Cerrena unicolor, were studied for their structure and properties. The phenazine core structure of the products was a result of tri-molecular transformation of aminomethoxybenzoic acid and aminonaphthalene sulfonic acid isomers. One of the compounds from the synthesised dye, namely 10-((2-carboxy-6-methoxyphenyl)amino)-11-methoxybenzo[a]phenazine-8-carboxylic acid, was able to inhibit the growth of Staphylococcus aureus. The high concentration of substrates (5 g/L) was efficiently transformed during 72 h in the mild conditions of pH 4 with the use of laccase with an activity of 200 U per g of the substrates mixture. The new bioactive dye exhibited excellent dyeing properties with concomitant antibacterial and antioxidative activity. The proposed enzyme-mediated synthesis represents an alternative eco-friendly route for the synthesis of novel antimicrobial compounds with high importance for the medical textile industry.

Removal of hard COD from biological effluent of coking wastewater using synchronized oxidation-adsorption technology: Performance, mechanism, and full-scale application

Efficient removal of the non-biodegradable organics from the biological effluent of industrial wastewater is becoming more and more important with the increasing demand for stringent discharge regulation. In this study, a synchronized oxidation-adsorption (SOA) technology was proposed for the removal of hardly biodegradable COD (hard COD) from the biological effluent of coking wastewater, and its performance was verified in a full-scale coking industrial park wastewater treatment plant (Q = 5,000 m3/d). The SOA was performed by coupling oxidation by hydroxyl radical (molar ratio of Fe2+ to H2O2 of 1:1 and pH = 5.0 ± 0.2) and adsorption by in-situ-formed nano hydrolyzed Fe3+ particles (nano-FeOOH). The nano hydrolyzed Fe3+ particles formed during the SOA exhibited a much higher specific surface area (22.83 m2/g) than the particles (10.87 m2/g) formed during the polyferric sulfate coagulation (PFSC). In comparison to PFSC, SOA performed better in terms of average COD removal (39% vs 18%) from the biological effluent. Wastewater fractionation result showed that SOA performed better in the removal of the hydrophobic acid matters, which was supported by the experiment using fulvic acid as the model organics. Mechanism studies using both biological effluent and fulvic acid solution showed that more carboxylic substances were adsorbed by the in-situ-formed nano-hydrolyzed Fe3+ particles formed by SOA than by PFSC, which was likely due to the generation of carboxylic substances by hydroxyl radical oxidation. In the full-scale, the COD was reduced from 118.5–198.0 mg/L in the PFSC-pretreated effluent to 61.5–104.0 mg/L through SOA treatment. The SOA treatment characterized with a mild pH condition (pH 5) and low molar ratio of Fe2+ to H2O2 (1:1) is particularly suitable for the polishing purpose to remove limited amount of organic pollutants from wastewater before discharge.