Acidic Environment Research Articles

In‐Silico Nanomedical Exploration of Mefloquine Drug Transport Using Pegylated Graphene Oxide Nanocarrier

AbstractThis study investigates the in‐silico transport of mefloquine (MQ) by using graphene oxide (GO) and polyethylene glycol (PEG)‐functionalized GO nanocarriers. Density functional theory (DFT) calculations are performed to explore the molecular interactions, electronic properties, thermodynamics, and release kinetics of MQ‐GO and MQ‐GO/PEG complexes across different phases and environmental conditions. Results indicate a strong affinity between MQ and both types of nanocarriers, with the adsorption energies ranging from −59.14 to −143.16 kcal mol−1, particularly in acidic environments. This suggests a potential for targeted drug delivery in acidic tumor micro‐environments. The incorporation of PEG, enhances stability and compatibility across phases, with chi interaction parameters of between 1.36 and 28.47, and the energy of mixture values, ranging from 0.80 to 16.86 kcal mol−1. The release time of MQ from the nanocarriers, varies significantly, depending on the adsorption energy, and ranges from 2.03 × 1030 to 6.98 × 1091 milliseconds across different phases, highlighting the need for further optimization of the drug delivery systems. The findings of this study provide valuable insights into the design and development of novel nanomedicines, based on MQ and GO nanocarriers, with implications for malaria treatments.

Profiling the dynamic adaptations of CAZyme-Producing microorganisms in the gastrointestinal tract of South African goats

The gastrointestinal tract of goats serves as a habitat for anaerobic microbial populations that work together to break down complex plant material, including lignocellulose. This study explored the microbial diversity and metabolic profiles across different gastrointestinal tract compartments. Significant diversity differences among the compartments were observed (ANOSIM p < 0.006), with the abomasum showing a distinct species composition and a decreased alpha diversity (Mann-Whitney/Kruskal-Wallis test p = 0.00096), possibly due to its acidic environment. Dominant microbial phyla included Proteobacteria, Bacteroidetes, and Firmicutes, with Proteobacteria being the most prevalent in the abomasum (50.06 %). Genera like Proteus and Bacteroides were particularly prominent in the rumen and reticulum, highlighting their significant role in feed degradation and fermentation processes. Over 65 % of genes at Kyoto Encyclopedia of Genes and Genomes level 1 were involved in metabolism with significant xenobiotic biodegradation in the abomasum. The dbCAN2 search identified Glycoside Hydrolases as the most prevalent CAZyme class (79 %), followed by Glycosyltransferases, Polysaccharide Lyases, and Carbohydrate Esterases, with Carbohydrate-Binding Modules and Auxiliary Activities accounting for 1 % of the hits. Higher CAZyme abundance was observed in the reticulum and omasum compartments, possibly due to MAGs diversity. In conclusion, the gastrointestinal tract of South African goats harbors diverse CAZyme classes, with Glycoside Hydrolases predominating. Interestingly, higher CAZyme abundance in specific compartments suggested compartmentalized microbial activity, reflecting adaptation to dietary substrates.

Singlet oxygen dominant-activation by hollow structural cobalt-based MOF/peroxymonosulfate system for micropollutant removal

Despite the keen interest in potentially using the metal-organic framework (MOF) in advanced oxidation processes (AOPs), their application for environmental abatement and the corresponding degradation mechanisms have remained largely elusive. This study explores the use of cobalt-based MOF (CoMOF) for peroxymonosulfate (PMS) activation to remove tetracycline (TC) from water resources. Under optimal conditions, the given catalytic system could achieve a TC removal of 83.3%. Radical quenching tests and EPR analysis revealed that SO4•–, HO•, •O2−, and 1O2 could participate in the catalytic degradation, but the discernible removal mechanism was mainly ascribed to the nonradical pathway induced by 1O2. At only 5 mg/L of CoMOF, the performance of the catalytic system was superior to that of PMS alone for different types of micropollutants. The CoMOF/PMS system could also reliably deal with typical anions in water, such as Cl−, SO42−, HCO3−, and PO43−. The MOF catalyst could last for four cycles with a minor decrease in reactivity of ∼30%. However, the removal performance decreased markedly when aromatic natural organic matter (NOM) were present in the water bodies, and the effectiveness was lower in alkaline or acidic environments. Our work offers insights into the catalytic degradation of CoMOF/PMS applied in contaminated water remediation and serves as a baseline for fabricating an efficient MOF with enhanced catalytic performance and stability.

Fiber Optics Analysis of Floating Hollow Microspheres for a Poorly Water-Soluble Drug

This study investigates the development and evaluation of floating hollow microspheres for the delivery of omeprazole, a poorly water-soluble drug. The research aims to enhance omeprazole's bioavailability by addressing its low solubility and susceptibility to degradation in an acidic gastric environment. Hollow ethyl cellulose microspheres encapsulating omeprazole were prepared using the solvent evaporation technique. The microspheres displayed 91.3% buoyancy and 82.41% drug entrapment efficiency, with sustained drug release in simulated gastric fluid over 12 hours. Characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used. XRD analysis indicated that the encapsulated drug was in an amorphous state, improving dissolution rates and bioavailability. FTIR confirmed successful drug encapsulation, and SEM revealed the morphology and porous structure of the microspheres. The results highlighting the potential of floating hollow microspheres to enhance the oral bioavailability of poorly water-soluble drugs. Recommendations include refining the formulation process and exploring microfluidic technology for generating uniform microspheres with high drug loading. The study provides valuable insights for the development of advanced drug delivery systems.

Experimental and theoretical assessment of bioinspired next-generation intercalated graphene oxide-based ceramic membranes for oil-in-water emulsion separation

2D graphene oxide (GO) membranes are gaining prominence for water reclamation from oily wastewater. Unresolved challenges include low membrane permeance from tight sheets and fouling during separation. In this work, a bioinspired Arabic gum (AG) was used as an intercalated agent with the help of glutaraldehyde to improve the GO membranes’ permeation and fouling resistance. The 2D-laminated separating layer is crafted through a self-assembling innovative approach utilizing pressurized dead-end assembly. The Arabic gum intercalated graphene oxide-modified ceramic membrane (AGIGO-CM) appeared superhydrophilic and underwater (UW) superoleophobic with a UW oil contact angle (UWOCA) of 156.1 ± 1.2°. The membrane prepared with 1 mg of AGIGO (AGIGO-1-CM) offers a flux of 17 times higher than pristine graphene oxide (p-GO) while maintaining a separation efficiency of >99% during the separation of the oil-in-water emulsions. Molecular dynamics (MD) simulations showed AG intercalation expanding the interlayer distance by up to 20 Å, with AGIGO having a higher fractional free volume (FFV) of 0.986 compared to p-GO’s 0.599. AGIGO-CM displayed lower interfacial formation energy (EIFE) of −1865.2 kcal/mol versus −765.5 kcal/mol for p-GO, indicating easier separation. It is further supported by the substantial interfacial thickness of 148 Å for AGIGO-CM compared to 53.0 Å for the p-GO membranes. AGIGO-CM showed minimal fouling, retaining >99% separation efficiency for 6 h. Compared to p-GO-CM, AGIGO-CM flux decreased by only 17.84% versus 44.72%. AGIGO-CM exhibited stability even in acidic and basic environments, showcasing its potential for high performance.

Synergistic effect of physics and chemistry on material removal of fused quartz in nanoparticle jet polishing

Fused quartz exhibits excellent optical and mechanical properties. Achieving ultra-smooth polishing of fused quartz is of great significance. Nanoparticle jet polishing (NJP) utilizes the synergistic effects of physics and chemistry to achieve damage-free atomic-level material removal. However, the influence of the process parameters on the interaction between the polishing particle and the workpiece remains unclear. This study experimentally and theoretically explored the effects of the slurry concentration, temperature, and pH on material removal. A high volume fraction of polishing slurry leads to poor fluidity of the polishing slurry and poor wettability on fused quartz, which slows down the growth rate of material removal rate. The polishing environment temperature regulates the material removal rate by altering the Ce3+ content in the polishing slurry. The pH influences the material removal process by affecting the Ce3+ content and the adsorption state between the particles and the workpiece. Alkaline conditions are conducive to forming stable ≡Ce-O-Si ≡ chemical bond to improve the material removal rate. Conversely, the electrostatic force between particle and workpiece in strongly acidic and alkaline environment hinders chemical adsorption. This study contributes to the understanding of the material removal process in NJP, providing a theoretical basis for optimizing the polishing process and improving the material removal rate.

The development of environmentally friendly Pr/W Co-doped Bi2MoO6 green pigment with high near-infrared reflectivity

In this article, a green pigment Bi1.95-xPrxW0.05MoO6+δ (x = 0.1–0.5) co-doped with Pr and W was developed using high temperature solid-phase synthesis method. The microstructure, color performance, and optical characteristics of the novel pigment was analyzed using x-ray diffraction instrument (XRD), field-emission scanning electron microscopy (FESEM), L∗ a∗ b∗ color date, and ultraviolet–visible–near infrared light spectrophotometer. The results indicate that all the samples possess a monoclinic structure, characterized by the space group P21/c(14). Compared to Bi2-xPrxMoO6+δ doped solely with Pr6O11, the Pr/W co-doped Bi2MoO6 pigment demonstrates superior green coloration. The solar reflectance in the near-infrared region of all pigment samples exceeds 80 %, highest value reaches 92.82 %. In thermal insulation tests, the temperature difference between the Bi1.95-xPrxW0.05MoO6+δ pigment coating and a blank galvanized sheet reaches up to 10.3 °C after 60 min under infrared lamp irradiation. The color difference ΔE∗ of the pigment powder after immersion in acid and alkali solution and high-temperature calcination are less than 5, indicating good chemical stabilities in acidic, alkaline and high-temperature environments. To our knowledge, Bi1.95-xPrxW0.05MoO6+δ has the highest reflectivity among green pigments without toxic metals.

Influence of pH value on erosive wear of 3D-printed polylactic acid for multiphase flow

Abstract Slurry erosion presents a critical challenge in hydrocarbon and cement processing industries, as well as in abrasive water jet cutting systems, leading to diminished operational efficiency and elevated maintenance costs. This study investigates the erosive wear behavior of Poly-Lactic Acid (PLA) fabricated with varying infill microtextures—zigzag, concentric, and grid—under diverse pH conditions (2.73, 7.75, and 10.15) using garnet particles as the erodent. The results demonstrate that optimal operational conditions for PLA are achieved with a grid microtexture, a pH of 7.75, and a 325 μm erodent size. Conversely, the most severe wear occurs under a pH of 10.15, a 600 μm erodent size, and a zigzag microtexture. The grid microtexture is the most effective in minimizing erosion, while the zigzag pattern shows a 16.68% increase in wear when compared to the grid microtexture. Additionally, a shift from a slightly basic to a highly acidic environment increases wear by 1%, whereas a transition to a highly basic environment leads to a 32.6% increase in erosion within the grid microtexture. The study highlights the significant contributions of infill microtexture (64%), erodent size (23.7%), and pH value (11%) to the overall erosion rate.

Facile fabrication of robust, multi-functional and superhydrophobic coatings with corrosion resistance and anti-icing performance

In this paper, a series of superhydrophobic coatings with varying n-SiO2 content were prepared using a simple one-step spray method. The coatings were characterized with SEM, XPS, electrochemical workstation, AFM, etc. The influence of n-SiO2 content on the micro-nanostructure of the coatings was investigated, as well as the elemental composition, the wettability, mechanical stability, chemical stability, and anti-icing performance. The results showed that as the n-SiO2 content increased, the wettability and anti-icing time of the coatings initially increased and then decreased. The optimal performance was achieved at an n-SiO2 content of 4.16 wt%, with a contact angle of 162.62°, a sliding angle of 4.17°, and an anti-icing time of 1095 s. Mechanical stability was improved with increasing n-SiO2 content, and the coatings lasted for 40 sandpaper abrasion cycles, 55 tape peeling cycles, and 31 icing/deicing cycles at 4.88 wt% of n-SiO2. The coatings demonstrated good chemical stability in neutral and acidic environments but failed in strongly alkaline conditions. Electrochemical tests revealed that the superhydrophobic coatings provided excellent protection, with the corrosion inhibition efficiency (η) of Q235 carbon steel reaching 99.99 % after coating compared to uncoated Q235 carbon steel.

Hurdle Concept and the Role of Lactic Acid Bacteria

The hurdle idea is a food preservation technique that includes building up a number of barriers to prevent microbes from growing and prolong the shelf life of perishable goods. The idea of using lactic acid bacteria (LAB), which are essential for food preservation, is one that is significant. Through a variety of processes, including fermentation, competitive exclusion, metabolite generation, biofilm formation, nutritional competition, and metabolic activity, LAB support the hurdle concept. Lactic acid bacteria (LAB) ferment glucose to produce lactic acid, which results in an acidic environment that prevents infections and spoiling germs from growing.

Study on hydration and heavy metal leaching of washed MSWI FA as a green cementitious material

Despite municipal solid waste incineration fly ash (MSWI FA) being classified as hazardous waste, there is a consensus on its significant potential for resource utilization. The high content of soluble chlorides in MSWI FA not only limits its co-disposal in cement kilns but also hinders its application in the field of construction materials. The research aimed to investigate the viability of MSWI FA as a binding material in the construction engineering field. Through examining the impact of liquid/solid ratio and pH levels on the chemical composition of MSWI FA during the washing procedure, the study delved into the mechanisms affecting hydration and the characteristics of heavy metal contamination before and after washing pretreatment. The results indicate the feasibility of developing MSWI FA into construction engineering materials. The liquid/solid ratio is a significant factor affecting the removal of chlorides, with an optimal ratio of 30. pH plays a crucial role in the mineral composition during the water-washing process of MSWI FA. An acidic environment can remove a higher proportion of chlorides, while an alkaline environment can form more calcium salts. The compressive strength of pure MSWI FA at 28 days is 3.92 MPa, which can be increased by 0.99 MPa after washing. The washed MSWI FA not only exhibits heightened reactivity but also demonstrates reduced leaching concentrations of heavy metals, and its leaching toxicity was much lower than the safe landfill threshold. Therefore, MSWI FA, after washing, is a very promising alternative material for construction engineering.

Two-dimensional MoSTe/MSi2N4 (M = Mo, W) van der Waals heterojunctions for photocatalytic water-splitting: A first-principles study

Direct Z-scheme heterojunction is a promising candidate for photocatalysts because it effectively separates the photogenerated electrons-hole pairs with strong redox capacity. In this paper, the MoSTe-MSi2N4 (M = Mo, W) heterostructures are constructed, and their stability, electronic structures and photocatalytic performance are investigated. The results demonstrate that the absorption properties of heterojunctions are significantly better than that of monolayers in both visible and ultraviolet light regions. Expressly, heterojunctions have the direct Z-scheme charge transfer mechanism when S surface of MoSTe contacted with MSi2N4 (namely S-M). Further calculation find that the S-M heterojunctions can perform stable photocatalytic water splitting in both acidic and neutral environments, and have better hydrogen evolution reaction. These theoretical predictions suggest that the MoSTe-MSi2N4 heterostructures are high-performance photocatalysts for the preparation of hydrogen gas.

Performance and microstructure of red-mud-blended concrete under different aqueous environments

The effects of aqueous environments on the performances of red-mud-blended concretes (RMCs) were evaluated by measuring their compressive strength, water absorption, and porosity. The pH value, electrical conductivity, and heavy metal concentrations of the immersion solutions were measured to determine the effects of RMCs on the aqueous solutions. The hydration products and microstructures of RMCs were analyzed to determine the effect mechanisms. The results showed that the addition of red mud to concretes increases the apparent porosity and water absorption and decreases the compressive strength. Acidic environments exhibited the most significant effect on the performances of RMCs. In a neutral environment, C–S–H gel generation and a high Si/Ca ratio resulted in enhanced corrosion resistance for the RMC with 35 % red mud, and its compressive strength decreased by 15.07 % after 28 d of immersion. The pH value and electrical conductivity showed a rapid increase, indicating the leaching of soluble alkalis and a large number of ions during soaking. The electrical conductivity showed a rapid increase with the immersion time within 60 d, indicating the leaching out of a large number of ions. The heavy metal concentration and pH value were within the range specified by Chinese standard (DZ/T 0290–2015), which provides many references for evaluating the interaction between RMCs and the aqueous environment.

Direct Z-scheme ZrS2/InP heterostructure as an efficient photocatalyst for overall water-splitting under acidic, alkaline and neutral environments

Photocatalytic water-splitting for hydrogen production by building heterostructure is an efficient approach to resolve the current environmental pollution problem. Here, the ZrS2/InP heterostructure with a direct Z-scheme have been constructed, and the first-principles calculations with Heyd-Scuseria-Ernzerhof (HSE06) hybrid function and density functional dispersion correction (DFT-D3) have been used to study their structural stabilities, electronic properties, photocatalytic mechanisms and optical features. The findings reveal that the ZrS2/InP heterostructure is a direct bandgap semiconductor having a type-II energy band alignment, where electrons mobilize from InP to ZrS2 monolayer at the interface of the heterostructure, leading to the creation of a build-in electric field pointing from InP to ZrS2. The ZrS2/InP heterostructure is competent for photocatalytic water-splitting owing to its advantageous band edge positions. In addition, the ZrS2/InP heterostructure possesses superior visible light absorption properties than the two monolayers structures, with a solar-to-hydrogen (STH) efficiency of 7.11 % and useable in acidic, alkaline and neutral environments. These excellent properties enable ZrS2/InP heterostructure to be an efficient photocatalyst for overall water-splitting. This effort not only proves the possibility of applying heterostructure in photocatalytic water-splitting but also has important implications for designing efficient direct Z-scheme photocatalysts.

Utilization of formic acid by extremely thermoacidophilic archaea species.

The exploration of novel hosts with the ability to assimilate formic acid, a C1 substrate that can be produced from renewable electrons and CO2, is of great relevance for developing novel and sustainable biomanufacturing platforms. Formatotrophs can use formic acid or formate as a carbon and/or reducing power source. Formatotrophy has typically been studied in neutrophilic microorganisms because formic acid toxicity increases in acidic environments below the pKa of 3.75 (25°C). Because of this toxicity challenge, utilization of formic acid as either a carbon or energy source has been largely unexplored in thermoacidophiles, species that possess the ability to produce a variety of metabolites and enzymes of high biotechnological relevance. Here we investigate the capacity of several thermoacidophilic archaea species from the Sulfolobales order to tolerate and metabolize formic acid. Metallosphaera prunae, Sulfolobus metallicus and Sulfolobus acidocaldarium were found to metabolize and grow with 1-2 mM of formic acid in batch cultivations. Formic acid was co-utilized by this species alongside physiological electron donors, including ferrous iron. To enhance formic acid utilization while maintaining aqueous concentrations below the toxicity threshold, we developed a bioreactor culturing method based on a sequential formic acid feeding strategy. By dosing small amounts of formic acid sequentially and feeding H2 as co-substrate, M. prunae could utilize a total of 16.3 mM of formic acid and grow to higher cell densities than when H2 was supplied as a sole electron donor. These results demonstrate the viability of culturing thermoacidophilic species with formic acid as an auxiliary substrate in bioreactors to obtain higher cell densities than those yielded by conventional autotrophic conditions. Our work underscores the significance of formic acid metabolism in extreme habitats and holds promise for biotechnological applications in the realm of sustainable energy production and environmental remediation.

PH-Sensitive Fluorescent Probe in Nanogel Particles as Theragnostic Agent for Imaging and Elimination of Latent Bacterial Cells Residing Inside Macrophages.

Rhodamine 6G (R6G) and 4-nitro-2,1,3-benzoxadiazole (NBD) linked through a spacer molecule spermidine (spd), R6G-spd-NBD, produces a fluorescent probe with pH-sensitive FRET (Förster (fluorescence) resonance energy transfer) effect that can be useful in a variety of diagnostic applications. Specifically, cancer cells can be spotted due to a local decrease in pH (Warburg effect). In this research, we applied this approach to intracellular infectious diseases-namely, leishmaniasis, brucellosis, and tuberculosis, difficult to treat because of their localization inside macrophages. R6G-spd-NBD offers an opportunity to detect such bacteria and potentially deliver therapeutic targets to treat them. The nanogel formulation of the R6G-spd-NBD probe (nanoparticles based on chitosan or heparin grafted with lipoic acid residues, Chit-LA and Hep-LA) was obtained to improve the pH sensitivity in the desired pH range (5.5-7.5), providing selective visualization and targeting of bacterial cells, thereby enhancing the capabilities of CLSM (confocal laser scanning microscopy) imaging. According to AFM (atomic force microscopy) data, nanogel particles containing R6G-spd-NBD of compact structure and spherical shape are formed, with a diameter of 70-100 nm. The nanogel formulation of the R6G-spd-NBD further improves absorption and penetration into bacteria, including those located inside macrophages. Due to the negative charge of the bacteria surface, the absorption of positively charged R6G-spd-NBD, and even more so in the chitosan derivatives' nanogel particles, is pronounced. Additionally, with a pH-sensitive R6G-spd-NBD fluorescent probe, the macrophages' lysosomes can be easily distinguished due to their acidic pH environment. CLSM was used to visualize samples of macrophage cells containing absorbed bacteria. The created nanoparticles showed a significant selectivity to model E. coli vs. Lactobacillus bacterial cells, and the R6G-spd-NBD agent, being a mild bactericide, cleared over 50% E.coli in conditions where Lactobacillus remained almost unaffected. Taken together, our data indicate that R6G-spd-NBD, as well as similar compounds, can have value not only for diagnostic, but also for theranostic applications.

Selective recovery of manganese from spent ternary lithium-ion batteries for efficient catalytic oxidation of VOCs: Unveiling the mechanism of activity Enhancement in recycled catalysts

With the widespread application of ternary lithium-ion batteries (TLBs) in various fields, the disposal of spent TLBs has become a globally recognized issue. This study proposes a novel method for reutilizing metal resources from TLBs. Through selective oxidation, manganese in a leaching solution of TLBs was converted into MnO2 with α, γ, and δ crystal phases (referred to as T-MnO2) for catalytic oxidation of volatile organic compounds (VOCs), while efficiently separating manganese from high-value metals such as nickel, cobalt, and lithium, achieving a manganese recovery rate of 99.99%. Compared to similar MnO2 prepared from pure materials, T-MnO2 exhibited superior degradation performance for toluene and chlorobenzene, with T90 decreasing by around 30 °C. The acidic synthesis environment provided by the leaching solution and the doping of trace metals altered the physicochemical properties of T-MnO2, such as increased specific surface area, elevated surface manganese valence, and improved redox performance and oxygen vacancy properties, enhancing its catalytic oxidation capacity. Furthermore, the degradation pathway of toluene on T-γ-MnO2 was inferred using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) and in-situ DRIFTs. This study provides a novel approach for recycling spent TLBs and treating VOCs catalytically.

A Facile and Rapid Immobilization Method of Titanium Dioxide-Alginate Composite for The Photocatalytic Removal of Reactive Black-5

A facile and rapid approach to immobilize nano-sized titanium dioxide (TiO2) using a renewable biopolymer (i.e. alginate) has been successfully demonstrated. TiO2 exhibits a positively charged surface in acidic environment due to the presence of hydroxyl groups. Meanwhile, alginate polymer is negatively charged at any pH due to the presence of carboxylic group in the polymer chain. The negatively charged alginate polymer and positively charged TiO2 formed composite instantaneously when the alginate polymer was introduced into the TiO2 nanoparticles suspension. The TiO2-alginate (TiO2-A) composite photocatalyst was characterized using thermogravimetric analysis (TGA), field emission-scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray (EDX) analysis and Fourier Transform Infrared (FTIR). Thermogravimetric analysis indicated that incorporating TiO2 into sodium alginate increases its decomposition temperature due to the stability of TiO2 at elevated temperatures, with the TiO2 content estimated in the composite being 55.6%, lower than the theoretical calculation of 62.8%. FTIR analysis revealed a shift in the peak of the carboxylic group of sodium alginate, suggesting composite formation through electrostatic interactions with TiO2 nanoparticles, while FESEM analysis showed that the TiO2-A composite surface exhibited more pores compared to protonated alginate. The TiO2-A composite was able to remove 90% of the Reactive Black 5 (RB5) in less than 200 min under Ultra-violet (UV) illumination. The optimal pH to remove RB5 was found to be pH 2 due strong electrostatic attraction of negatively charged RB5 on the positive surface of TiO2 nanoparticles. The photocatalyst can be recovered by simple separation method, i.e. gravitational settling, and reused for 10 consecutive cycles with efficiency greater than 90% consistently. The TiO2-A composite is a promising immobilized photocatalyst for practical application in wastewater treatment. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Competing Kinetic Consequences of CO2 on the Oxidative Degradation of Branched Poly(ethylenimine).

Amine-functionalized porous solid materials are effective sorbents for direct air capture (DAC) of CO2. However, they are prone to oxidative degradation in service, increasing the materials cost for widespread implementation. While the identification of oxidation products has given insights into degradation pathways, the roles of some species, like CO2 itself, remain unresolved, with conflicting information in the literature. Here, we investigate the impact of CO2 on the oxidative degradation of poly(ethylenimine)-alumina (PEI/Al2O3) sorbents under conditions encompassing a wide range of CO2-air mixture compositions and temperatures relevant to DAC conditions, thereby reconciling the conflicting data in the literature. Degradation profiles characterized by thermogravimetric analysis, in situ ATR-FTIR, and CO2 capacity measurements reveal nonmonotonic effects of CO2 concentrations and temperatures on oxidation kinetics. Specifically, 0.04% CO2 accelerates PEI/Al2O3 oxidation more at low temperatures (<90 °C) compared to 1% and 5% CO2, but this trend reverses at high temperatures (>90 °C). First-principles metadynamics, machine learning accelerated molecular dynamics simulations, and 1H relaxometry experiments show that chemisorbed CO2 acid-catalyzes critical oxidation reactions, while extensive CO2 uptake reduces PEI branch mobility, slowing radical propagation. These contrasting kinetic effects of CO2 explain the complex degradation profiles observed in this work and in prior literature. Collectively, this work highlights the importance of considering atmospheric components in the design of DAC sorbents and processes. Additionally, it identifies the unconstrained branch mobility and local acid environment as two of the major culprits in the oxidation of amine-based sorbents, suggesting potential strategies to mitigate sorbent degradation.

Green chemistry approach to corrosion prevention: Saccocalyx satureioides as an effective inhibitor for C45 steel in acidic medium (HCl)

Carbon steel's corrosion in harsh, acidic environments presents significant challenges to industrial use. While traditional inhibitors are effective, they often raise environmental and sustainability concerns. This study explores the potential of Saccocalyx satureioides extract (S. Satureioides) as an environmentally Eco-friendly corrosion inhibitor for protecting carbon steel 45 in a highly corrosive 0.5 M HCl solution. The organic components of the sample were identified using phytochemical screening, LC-MS analysis, and ATR-FTIR spectroscopy. The main compounds detected were coumaric acid (68.10%), 4-methoxybenzoic acid (15.15%), and kaempferol (11.36%). Weight loss measurements demonstrated that the S. Satureioides extract had a highly effective anti-corrosion capability, achieving an inhibitory efficiency of around 96.93% at a concentration of 3 g.L-1 at a temperature of 25°C after 360 hours of immersion. This significantly reduced the corrosion rate from 0.1721 mg.cm−2.h−1 to 0.0053 mg.cm−2.h−1. The adsorption isotherms indicated that the adsorption of S. Satureioides molecules onto the steel surface followed the Langmuir model, exhibiting a high correlation coefficient of 0.9958. The negative value of the adsorption free energy ( = -17.162 kJ mol-1) indicates that the physisorption interactions occurred spontaneously. The SEM/EDX analysis revealed that the steel surface exhibited reduced damage due to the inhibitor's protective coating formation. This research not only significantly contributes to corrosion science filed but also provides crucial support for global efforts to promote sustainable industrial practices, with potential applications in various industries worldwide.