Strong Acidic Conditions Research Articles

Stable Ozonides plus Vitamin E Acetate (Ozoile) for Treatment of Genitourinary Syndrome.

Background and Objectives: Genitourinary syndrome, previously defined as vulvovaginal atrophy, manifests with signs and symptoms deriving from estrogen diminution in the female genitourinary tract. Stable ozonides are derivatives of artemisinin found to be stable against strong basic and acidic conditions. Vitamin E is an important antioxidant diminishing the output of reactive oxygen species in the oxidation of fats and the emanation of free radicals, reducing cellular injury and aging. The primary aim of the present study was to assess the positive effects of an ozonide plus a vitamin E acetate-based compound (Ozoile) on genitourinary syndrome symptom relief after a maximum of 20 days of treatment. Materials and Methods: The inclusion criteria for patients' enrollment were women of child-bearing age or in menopause reporting genitourinary syndrome's related symptoms, such as pain, burning, a bad smell, dyspareunia, dryness, itching, bleeding, and nervousness. The exclusion criteria were Sjogren's syndrome and patients administered retinoic acid, an agent that causes mucosal dryness. Participants completed a questionnaire before and after 20 days of treatment. Results: The incidence of pain decreased from 16.7% to 11.8% (p-value < 0.0001). In addition, the mean symptom intensity decreased from 2.10 to 0.87 (p-value < 0.0001). Dryness was the most frequent pre-treatment symptom and decreased from 85.5% to 53.8% (p-value < 0.0001) (mean: 2.21 vs. 0.90; p-value < 0.0001). Conclusions: Ozoile was effective in reducing most gynecologic symptoms related to genitourinary syndrome. However, further studies are needed to compare its effect with other standards of care.

Novel Imidazole‐based Hydrazonoyl Cyanides and Amidrazones Containing N(N,O)‐Heterocycles: Selective Synthesis, Reaction Mechanisms and Preliminary Anticancer Evaluation

AbstractTwo series of novel hybrid heterocyclic compounds that combine the imidazole ring with bioactive piperidine, morpholine or piperazine heterosystems, through a hydrazone unit, were easily obtained by two competitive pathways. Starting from 5‐amino‐4‐cyanoformimidoyl imidazoles and 1‐aminopiperidine, 4‐aminomorpholine or 1‐amino‐4‐methylpiperazine under mild acidic media led to the selective synthesis of 5‐aminoimidazole 4‐carboxamidrazones, whereas the corresponding 4‐hydrazonoyl cyanide derivatives were obtained under stronger acidic conditions. These highly functionalized imidazoles provide convenient synthetic precursors to a vast array of heterocycles with potential pharmaceutical applications. The reaction mechanisms were elucidated on the basis of experimental assays and in silico calculations. The compounds were screened against colorectal cancer HCT116‐p53 wt cell line, and significant IC50 values of 3.69 μM and 4.83 μM were obtained.

Hydrodynamics-engineered polyaniline nanofibers on graphene nanosheets for high-performance pH sensors

Real-time sweat monitoring in the human body using wearable sensors is promising for noninvasive and continuous healthcare applications. For reliable and accurate sweat analysis, further improvement in the response time and long-term stability of sensors is required. This paper reports an electrochemical pH sensor based on polyaniline/graphene (PANi-Gr) with rapid electron and ion transfer. The implementation of the Taylor–Couette flow approach allowed the efficient exfoliation of graphite into Gr nanosheets and the rapid polymerization of aniline monomers on the Gr surface, resulting in nanofiber PANi-deposited Gr nanocomposites. PANi-Gr had a large surface area and porous structure, which are favorable for rapid and stable electrochemical reactions. The screen-printed PANi-Gr-based pH sensor exhibited a Nernstian sensitivity of 61.91 mV/pH, rapid response time of <1 s, and long-term stability upon monitoring with minimal potential drift (0.04 mV h−1) under strong acidic and basic conditions. Furthermore, the on-body performance of the wearable pH sensor integrated with a wireless electronic device was analyzed via the noninvasive real-time monitoring of human sweat pH during stationary cycling. The developed sensor can be used in wearable real-time sweat monitoring devices for medical and healthcare applications.

Emulsions Stabilized with an Electrostatic Complex of Quaternized Cellulose Nanofiber and Octanoyl Gelatin and the Effect of pH Value on Their Stability

Oil/water (O/W) emulsions were prepared using the complex of quarternized cellulose nanofiber (QCNF) and octanoyl gelatin (OC−Gel) as an emulsifier, and the effect of pH value on their stability was investigated. OC−Gel was prepared through a condensation reaction, confirmed by 1H Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FT−IR) spectroscopy. It reduced air/water interfacial tension more effectively than unmodified gelatin. The complexation degree of OC−Gel and QCNF, measured by optical density, showed its maximum at a QCNF/OC−Gel mass ratio of 1/8 when the pH value of the medium was 7.4, and it increased in a saturated manner with increasing pH value. The signals of QCNF were found in the FT−IR and X−ray diffraction spectra of the complex, suggesting that the positively charged CNF were included in the OC−Gel−based complex. The complex formed a rough surface with smooth debris because the surface roughness of the complex aggregation reflected that of both QCNF and OC−Gel aggregation. QCNF could stabilize oil droplets to form a Pickering O/W emulsion. The complex of QCNF/OC−Gel was also a good emulsifier. QCNF and the complex were as potent as OC−Gel in emulsifying mineral oil in water. Most of the droplets fell within 5–25 µm, regardless of what the emulsifier was. The emulsion stabilized with OC−Gel increased in its oil droplet size more than two times in 20 days at all the pH vales tested (pH 3, 5, 7.4, 9), whereas the emulsion stabilized with QCNF remained almost constant in size during the same period regardless of the pH values. The droplet size of emulsion stabilized with the QCNF/OC−Gel complex did not change appreciably when the pH value was 5, 7.4, and 9. The complex seemed to act as a capsule wall and prevent the coalescence of the droplets. However, it increased dramatically due to the coalescence at pH 3, possibly because the complex could be dissolved under a strong acidic condition.

Commercial Nafion Membranes for Harvesting Osmotic Energy from Proton Gradients that Exceed the Commercial Goal of 5.0 W/m2.

Osmotic energy from proton gradients in industrial acidic wastewater can be harvested and converted to electricity through membranes, making it a renewable and sustainable power source. However, the currently designed membranes for harvesting proton gradient energy in acidic wastewater cannot simultaneously achieve excellent chemical/mechanical stability and high power density under a large-scale area and require high cost and complex operations. Here, we demonstrate that commercial Nafion membranes with high chemical/mechanical stability and proton transport selectivity can generate a power density of 5.1 W/m2 for harvesting osmotic energy from proton gradients under a test area of 0.2 mm2, which exceeds the commercial goal of 5.0 W/m2. Even under a test area of 12.5 mm2, a power density of 2.1 W/m2 can be achieved under a strong acid condition. In addition, the heat can greatly promote proton transport, and the power density is increased, i.e., 8.1 W/m2 at 333 K (5.1 W/m2 at 293 K) under a test area of 0.2 mm2. By matching membranes with ion selectivity, our work demonstrates the potential of Nafion membranes for harvesting proton gradient energy in acidic wastewater and provides an approach for large-scale conversion of osmotic energy.

Humic acid-based polyphenol-functionalized collagen fiber for efficient recognition capture of iodine vapor

Effective capture of radioactive iodine vapor is a crucial part of the spent fuel reprocessing process. In this study, humic acid (HA), which has excellent recognition capture of iodine vapor, is introduced as the active site construction center, functionalizing and modifying alkali-activated collagen fiber (ACF), to prepare the biomass composite functional materials (HA@ACF). The results demonstrate that HA@ACF exhibits exceptional recognition ability and a strong affinity for iodine vapor, with an adsorption capacity of 2811.8 mg/g (ACF is only 1068.6 mg/g). Simultaneously, under relative humidity of 27 % and strong acid conditions, the iodine vapor capture capacity of HA@ACF only decreased by 17.2 %, indicating that the material exhibits excellent iodine capture performance under complex conditions. The excellent adsorption performance is attributed to the synergistic effect of abundant −NHR, C = O, and phenolic hydroxyl active sites in HA@ACF, which recognize and induce iodine vapor, resulting in the capture of iodine molecules as I3-. Meanwhile, DFT calculations reveal the excellent adsorption energy (−0.51 eV) of iodine vapor on the phenolic hydroxyl groups on HA. Therefore, the HA@ACF biomass composite functional material can be an ideal candidate adsorbent for the efficient recognition capture of radioactive iodine vapor in airborne effluent.

Multistimuli‐Responsive Luminescent Porous Organic Polymers with Chiroptical Properties and Acid‐Induced Degradation

Comprehensive SummaryPorous organic polymers (POPs) have attracted great attention in past decades. Although diverse functional POPs have been developed, multistimuli‐responsive POPs with excellent aggregate‐state luminescence together with good chiroptical properties have rarely been reported. Herein, two pairs of Salen‐type enantiomeric POPs with multistimuli‐responsive luminescence and chiral features were designed and synthesized by facile polycondensation reactions between polyfunctional aggregation‐induced emission luminogen (AIEgen)‐containing salicylaldehyde derivatives and chiral diamines. With Salen units in polymer backbones as tetradentate ligands, a series of POP‐metal complexes were further prepared. The obtained POPs and metal complexes show good porosity, high thermal stability, and obvious circular dichroism signals. Moreover, benefiting from the coexistence of AIEgen and Salen units in polymer structures, these POPs exhibit excellent luminescence performance in aggregate states and tunable fluorescence behaviors in response to external stimuli of Zn2+ ion, mechanical forces, organic solvent, and acids. Due to the dynamic feature of Schiff base C=N bonds, the present POPs can efficiently undergo hydrolysis reactions under strong acidic conditions to reproduce the AIEgen‐ containing monomers, and such an acid‐induced degradation process can be directly visualized and dynamically monitored via fluorescence variation. These properties collectively make the POPs candidate materials for applications in heterogeneous asymmetric catalysis, fluorescence sensing, biomedicine, etc.

Cage-like octa(aminopropyl) silsesquioxane functionalized Ti3C2Tx for selective adsorption of Pb (II) ions by synergistic effect of coordination and oxidation

Transition metal carbides or nitride (MXene) have attracted wide attention due to their unique properties and promising applications in batteries, sensors, and catalysis. Due to its good hydrophilicity and abundant groups, it is also favored in environmental remediation. In this work, a cage-like octa(aminopropyl) silsesquioxane (POSS-NH2) was chosen as the modifier to decorate the Ti3C2Tx and an amino-rich lamellar material, Ti3C2Tx/POSS-NH2, was prepared successfully via a dehydration condensation reaction. Ti3C2Tx/POSS-NH2 shows excellent adsorption capability toward Pb (II) ions within a wide pH range with an optimal adsorption capacity of 552.31 mg·g–1 at the pH value of 6. Even at strong acidic conditions (pH=2), the value is still as high as 283.65 mg·g–1. The Ti3C2Tx/POSS-NH2 also shows preferential selectivity for lead ions in lead-containing wastewaters containing Cu (II), Zn (II), Fe (II) and Mg (II) ions. The kinetics, isotherm, and thermodynamic analyses were also studied. It is found that the adsorption process is an endothermic one and complies with the Langmuir isothermal adsorption model. The experimental data of Pb (II） ions adsorption by Ti3C2Tx/POSS-NH2 can be well simulated with the pseudo-second-order kinetic model. XPS and FTIR results showed that the Pb (II) ions were captured by a synergistic effect of coordination of -NH2 on the Ti3C2Tx/POSS-NH2 surface and the oxidation of oxygenated moieties in the layered structure of Ti3C2Tx. The excellent properties of Ti3C2Tx/POSS-NH2 allow it to occupy an important position in the treatment of lead-containing wastewater.

Squaric esters as peptide stapling reagents

We report that squaric esters can serve as bifunctional reagents for selective peptide stapling reactions. Formation of the squaric amide staple occurs under mild conditions with amine-containing side chains. We show that short resin-bound peptides are readily stapled on solid phase and that stapling can occur at various relative positions along the peptide and with various amine tether lengths (e.g. Lysine, ornithine, etc). The squaric amide staples are stable to strong acid conditions used to cleave the stapled peptide from the resin and the stapled peptides show an increase in helicity as analyzed through circular dichroism.

Turning harmful Mn2+ to treasure: In-situ formed ε-MnO2 for removing heavy metals from acid mine drainage

Acid mine drainage (AMD) contains high concentrations of heavy metals, causing serious environmental pollution. Current neutralization techniques fail to recover and utilize valuable heavy metals, and generate large quantities of hazardous sludge. Manganese (Mn) is generally present at high levels in AMD. Therefore, this paper proposed a technology to recover Mn from AMD, by adding KMnO4 to converting Mn into ε-MnO2. Ultra-Violet C (UVC) was used to photolyze the residual KMnO4. The study then evaluated the processes and mechanisms involved in the technology. The photolysis of KMnO4 in strong acidic conditions was determined, and new mechanisms were proposed. MnO2 produced by the photolysis process was formed through the reaction between Mn(III) and KMnO4. In the absence of KMnO4, Mn(III) underwent further photolysis and was reduced to Mn2+. The maximum adsorption capacities of in-situ formed ε-MnO2 for Pb2+, Cd2+, and Fe3+ were 449.80, 122.05, and 779.88 mg/g, respectively. Higher Mn-OH levels and MnO2 regeneration were crucial in improving adsorption performance. Proton exchange and inner-circle complexation were the main pathways for Pb2+ and Cd2+ adsorption by in-situ formed ε-MnO2. A phase transformation occurred when a substantial amount of Fe3+ was adsorbed, leading to the gradual transformation to MnFe binary oxides. When applying in-situ formed ε-MnO2 technology for actual AMD treatment, 98.62 % of Mn in AMD was recovered within 24 h in the presence of ε-MnO2 for possible further reuse in industries, with a final recovery of 0.76 kg/m3. Further, this technique removed other heavy metals and reduced the sludge volume by 20.99 % when used as a pre-treatment step for neutralization. These results demonstrated the broad potential of this treatment technology.

Chemical resistance and corrosion mechanism of aluminophosphate-based low temperature enamel (LTE) in H2SO4 and NaOH solutions

Enamel coatings, showing advantages in material durability, aesthetics, hardness, corrosion resistance, and high-temperature tolerance, are widely used for corrosion protection of metallic substrate. Recently, a new type of aluminophosphate-based low temperature enamel (LTE) coating was developed to avoid the strength degradation of steel substrate, which was also applicable to relatively low-melting metal and was more environmentally friendly with reduced energy consumption. LTE coating might suffer the corrosion of acids or alkalis in some special cases like kitchen utensils, petroleum pipelines, and reinforcing bars. In this study, the chemical corrosion behavior of aluminophosphate-based LTE was investigated in H2SO4 and NaOH solutions with varying pHs of 1∼13. Results indicated that after 30 days of immersion, LTE survived at pHs 3–10, but severely deteriorated at pHs 1, 2, 12, and 13, with the corroded layer presenting a loose structure, completely losing mechanical strength, and even peeling off. For pH 11, the color changed slightly whereas the mass loss was negligible. Specially, LTE suffered selective corrosion in strong acid and alkali conditions, that is, H2SO4 corroded the Ca-compounds (Ca5(PO4)3F and CaF2) phases to generate CaSO4·2H2O and H3PO4, whereas NaOH corroded the LTE matrix (AlPO4) to generate soluble Na3PO4 and NaAlO2. The findings of this study confirmed the acid and alkali tolerance range of LTE and clarified the corrosion mechanism of LTE under both acid and alkaline environments, which guides the further composition design and application of LTE coatings.

Homogeneous oxidation of EE2 by ozone: Influencing factors, degradation pathway, and toxicity assessment

17α-Ethinylestradiol(EE2) is a common hormone drug that plays an essential role in endocrine and reproductive health. However, estrogens are degraded only to a limited extent by humans and livestock themselves, and most of them are excreted in undegraded or partially degraded form from human and livestock feces and urine into water bodies, posing a austere ecological risk. Of the known degradation processes in wastewater treatment plants, ozone-induced advanced oxidation shows tremendous potential. At the same time, the limitations of the test methodology makes it extremely difficult to do an in-depth investigation of the degradation mechanism. In this study, the influencing factors, including ozone dose, initial concentration, and pH were investigated. The degradation pathways of EE2 were analyzed by combing with quantum chemical calculations and high performance liquid chromatography coupled with quadrupole-time of flight tandem mass spectrometry (HPLC-Q-TOF-MS). Toxicity Estimation Software Tool (T.E.S.T) evaluated EE2 and its degradation intermediates for a variety of toxicities. And the results showed that reactions such as oxidative hydroxylation of the benzene ring and oxidative ring opening of the aliphatic ring mainly occurred during the degradation of estrogens, and the reaction was initially fast. The degradation effect is lower under neutral conditions, and the acidity and alkalinity of the solution are reduced with the reaction process under strong acid and alkaline conditions. The products of the experimental reactions reflect the active site, e.g., product P1 reflects C(5) as the site of easy reaction, which is consistent with previous theoretical predictions, suggesting that theoretical studies can provide complementary information on oxidation. The toxicity of intermediates obtained from partial ozone degradation improved compared to EE2, and the mutagenicity of EE2 was elevated greatly. However, single ozonation significantly diminished the developmental toxicity and bioaccumulation factor for a large proportion of intermediates. This work may contribute to the theoretical foundation for the practical application of ozone oxidation of environmental estrogens.

A novel wholly-Tröger's Base-based polyamide nanofiltration membrane constructed for the separation application in strong acidic condition via acid-induced segregation

In this study, a new kind of wholly-Tröger's base-based polyamide (wTB-PA) thin film composite (TFC) nanofiltration (NF) membrane was successfully fabricated for the separation application in strong acidic condition via the acid-induced segregation (AIS) effect. Firstly, the self-synthesized Tröger's base diamine monomer — 2,8-diamino-4,10-dimethyl-6H,12H-5,11-methanodibenzo [1,5]-diazocine (TBDA) was added in the polyethersulfone (PES) casting solution to prepare the TBDA-based PES substrate by synchronously coupling the non-solvent-induced phase transformation (NIPs) and AIS, and then the TBDA molecules on the PES substrate surface further reacted with trimesoyl chloride (TMC) via interfacial polymerization (IP) to obtain the wTB-PA TFC NF membranes. Meanwhile, the acid-induced segregation effect of on the microstructure and separation performance of the wTB-PA TFC NF membrane were systematically investigated. As compared with the conventional poly(piperazine amide) NF membrane (MPIP-TMC), the wTB-PA NF membranes exhibited thinner, smoother but more hydrophobic surface as well as lower isoelectric point, and especially showed much higher tolerance to 20 wt% H2SO4 after soaking 63 days and favorable dye rejection (～99.9 %). Thereinto, the acid segregation agent of citric acid monohydrate (CA) endowed the wTB-PA TFC NF membrane with relatively optimal acid resistance and SO42−/Cl− separation selectivity (about 11.8) than glacial acetic acid (AC), nitric acid (HNO3) and hydrochloric acid (HCl). Moreover, this wTB-PA NF membrane based on CA-induced segregation had higher recovery of the positively charged dye of methyl orange (MO) (＞98.0 %) in acidic condition. Therefore, the wTB-PA TFC NF membranes have great potential for the separation application in the strong acidic condition in the future.

Preparation and properties of oxidized multi-walled carbon nanotube superhydrophobic composites modified by bio-fatty acids

In this paper, a preparation method of superhydrophobic composites of oxidized multi-walled carbon nanotubes modified by stearic acid (SA) is proposed. Hydroxylated multi-walled carbon nanotubes (HMWCNTs) were obtained by oxidizing multi-walled carbon nanotubes with potassium dichromate to give them hydroxyl groups on the surface. Subsequently, the carboxyl group in the SA molecule was esterified with the hydroxyl group on the HMWCNTs. SA molecules were grafted onto the surface of multi-walled carbon nanotubes. SA modified oxidized multi-walled carbon nanotubes (SMWCNT) superhydrophobic composites were obtained. The results show that the water contact angle (WCA) of superhydrophobic composites can reach up to 174°. At the same time, the modified nanocomposites have good anti-icing and corrosion resistance. After low temperature delayed freezing test, the freezing extension time of the nanocomposite film is 30 times that of the smooth surface. Under strong acid and alkali conditions, the superhydrophobic nanocomposites still maintain good superhydrophobicity. The nanocomposites may have potential applications in the preparation of large-scale superhydrophobic coatings.

Preparation of multifunctional cellulose macromolecule blended fabrics through internal and external synergy by N1, N6-bis (ethylene oxide-2-ylmethyl) hexane-1,6-diamine

With the diversification of people's demand for textile functions, the preparation of multifunctional fabrics is still a current research hotspot. In this study, the water-soluble epoxy compound N1, N6-bis(oxiran-2-ylmethyl) hexane-1,6-diamine (EH) was introduced into cellulose macromolecule blended fabrics (cotton/modal) by two-phase vaporization technique, resulting in excellent wrinkle, hydrophobicity, and certain UV protection effects. It could be observed by electron microscopy that EH formed a polymer film on the fiber surface. In addition, the results of EDS scans and fiber swelling rate tests showed that EH was uniformly distributed and formed a cross-linked structure in the amorphous zones inside the fibers. Compared with the control fabrics, the wrinkle recovery angle of the EH-treated fabric was increased by 39.7 %. The fabrics could reach a contact angle of 136.9°, providing excellent hydrophobic effect. In addition, the fabrics achieved certain UV protection effects (UPF of 50+). The EH-treated fabrics were less stabilized in strong acid and alkali conditions, but exhibited greater durability in other environments. In summary, the internal and external synergistic effects of EH in forming polymer films on the fibers surface and internal cross-linking structures provided a cleaner, simple, and feasible method for the preparation of multifunctional cellulose macromolecule fibers textiles.

Conductive polymer protection strategy to promote electrochemical nitrate reduction to ammonia in highly acidic condition over Cu-based catalyst

Electrochemical nitrate reduction (NO3-RR) is a promising way to produce ammonia by alternating Haber-Bosch process. As one promising catalyst, copper suffers from low activity and instability in acidic electrolyte that hinders practical applications. Herein, we report a conductive polymer protection strategy by decorating polypyrrole on Cu nanoparticles (Cu-PPy), achieving high NO3-RR efficiency under strong acidic conditions. In 0.5 M H2SO4, Cu-PPy exhibits high NH3 yield rate of 0.55 mmol h−1 cm−2 with NH3 selectivity of 99.99 % and FE of 96.0 % at high NO3– conversion. Experimental and theoretical results reveal that PPy plays a pluripotent role for the enhanced NO3-RR, consisting of protecting Cu from corrosion in highly acidic electrolyte, promoting the adsorption of NO3– and NO2– in local environment, stabilizing Cu in intermediate valence state, and accelerating the electron transfer rate. Furthermore, a co-production system of NH3 and adipic acid is constructed and achieves high combined electron efficiency.

Direct Capturing and Regulating Key Intermediates for High-Efficiency Oxygen Evolution Reactions.

Developing efficient oxygen evolution reaction (OER) electrocatalysts can greatly advance the commercialization of proton exchange membrane (PEM) water electrolysis. However, the unclear and disputed reaction mechanism and structure-activity relationship of OER pose significant obstacles. Herein, the active site and intermediate for OER on AuIr nanoalloys are simultaneously identified and correlated with the activity, through the integration of in situ shell-isolated nanoparticle-enhanced Raman spectroscopy and X-ray absorption spectroscopy. The AuIr nanoalloys display excellent OER performance with an overpotential of only 246mV to achieve 10mA cm-2 and long-term stability under strong acidic conditions. Direct spectroscopic evidence demonstrates that *OO adsorbed on IrOx sites is the key intermediate for OER, and it is generated through the O-O coupling of adsorbed oxygen species directly from water, providing clear support for the adsorbate evolution mechanism. Moreover, the Raman information of the *OO intermediate can serve as a universal "in situ descriptor" that can be obtained both experimentally and theoretically to accelerate the catalyst design. It unveils that weakening the interactions of *OO on the catalysts and facilitating its desorption would boost the OER performance. This work deepens the mechanistic understandings on OER and provides insightful guidance for the design of more efficient OER catalysts.

Fabrication of ammonia and acetic acid-responsive intelligent films based on grape skin anthocyanin via adjusting the pH of film-forming solution

pH-responsive intelligent films for food freshness monitoring have attracted great attentions recently. In this study, several intelligent films based on chitosan (CS), polyvinyl alcohol (PVA), and grape skin anthocyanin (GSA) were prepared, and the effect of film-forming solution pH on the properties of intelligent films was investigated. The results of SEM, FTIR, XRD and TGA displayed that the hydrogen bond between CS and GSA was strong at strong acidic conditions (2.0–2.5), and it weakened at weak acidic conditions (3.0–4.5). Meanwhile, the hydrogen bond between PVA and GSA was negligible under strong acidic conditions, and it appeared under weak acidic conditions. Consequently, the films fabricated under weak acidic conditions displayed lower water solubility, lower water vapor permeability, and higher elongation at break. The tensile strength of films increased firstly and subsequently decreased with pH increasing, reaching a maximum value of 31.44 MPa at pH 3.5. Additionally, the films prepared at pH 2.5 and 4.0 showed the best color responsiveness to ammonia and acetic acid, respectively. Overall, the intelligent films prepared under variant pH have the potential to realize the goal of monitoring the freshness of different types of food, thereby expanding the application subject of anthocyanins-based intelligent films.

Ultrahigh dark and light-improved chloride removal performance of magnetite bismuth oxide thin flakes with low crystallinity

The high concentration of chloride (Cl-) ions in wastewater poses environmental risks. The bismuth oxide (Bi2O3)-based Cl- removal method has gained significant attention due to its high selectivity towards Cl- ions. However, it still faces challenges related to strong acid condition and excessive dosage. Herein, the mixed-ferrites (M-Fe3O4) nanoparticles with broadband absorption property were combined with Bi2O3 to form to the magnetite Bi2O3 (FBO) composites. Due to the space separation of M-Fe3O4 nanoparticles in the thin Bi2O3 flakes, FBO had a loose structure, and its sample after 100 °C treatment (FBO-100) possessed weak crystallinity and the largest specific surface area, which enabled it to possess the highest Cl- removal efficiency of 98.4% at pH = 1 in the dark. Under UV-Vis-NIR irradiation, the Cl- removal efficiencies of FBO-100 at pH = 2, 3, and 5 increased from 71.4%, 56.3%, and 54.5% to 84.6%, 65.5%, and 58.0%, respectively. During the light-irradiated Cl- removal process, the heterostructures of Bi2O3/M-Fe3O4, Bi2O3/BiOCl/M-Fe3O4, and BiOCl/M-Fe3O4 were successively built, and the oxidative photocorrosion of Bi2O3 caused by holes played the predominant role in improving the Cl- removal efficiency, compared with the •OH, Cl•, and O2•− radicals. FBO-100 had stable cyclic Cl- removal performance and high safety, which is expected to be of a good application prospect for Cl- removal.

Z-scheme heterojunction Bi2WO6/NH2-MIL-53(Fe) photocatalyst: Simultaneous efficient photo-Fenton degradation of SMX and photocatalytic reduction of Cr(VI)

The aim of this study was to develop a Z-scheme heterojunction Bi2WO6/NH2-MIL-53(Fe) photo-Fenton catalyst with enhanced electron-hole separation using an in situ growth method. Bi2WO6/NH2-MIL-53(Fe) promotes Fe(II)/Fe(III) cycling under visible light and trace H2O2 (5 μL) conditions, photo-Fenton degraded 82% of SMX within 60 min, 6.3 times that of pure Bi2WO6. It was also able to reduce Cr(VI) (20 mg/L) up to 97% efficiency under strong acidic conditions, which was 2.4 times that of Bi2WO6. In addition, Bi2WO6/NH2-MIL-53(Fe) has good stability and reusability, capable of degrading 75% of SMX and reducing 87% of Cr(VI) even after four cycles of testing. The mechanism of action of this catalyst was investigated by free radical trapping experiments, and the formation of Z-scheme heterojunction was demonstrated. In conclusion, Bi2WO6/NH2-MIL-53(Fe) is a promising photo-Fenton catalyst, which not only efficiently degrades antibiotics, but also exhibits excellent photocatalytic performance against Cr(VI) under strong acid conditions, providing a new idea for the treatment of complex pollutants.