HCl Aqueous Solution Research Articles

Peach gum-based polyimine networks with water resistant, high strength and recycling performances

The preparation of the polyimine (PI) networks from renewable feedstocks has attracted increasing attention due to the degradability and self-healing capabilities of PI networks, which contribute to sustainable development. However, most of bio-based PI networks possess poor environmental stability and mechanical strength. Herein, natural peach gum w·as employed to construct water-resistant bio-based PI networks with high performances, by the curing reaction of Schiff base between 4-aminobenzoic acid grafted peach gum polysaccharide and vanillin-derived difunctionalized aldehyde. The resultant polyimine networks (PGBV) exhibit high tensile strength and high Young's modulus, due to their unique network structures. Moreover, PGBV-100 demonstrates excellent hydrophobicity, welding, self-healing and reprocessing abilities. Furthermore, PGBV-100 can completely degrade in an aqueous solution of HCl (0.1 M), enabling closed-loop recycling. In this work, a research strategy for constructing bio-based PI networks with high performances is presented and the resultant PGBV networks show promising potential application as materials for transportation and building materials.

Depolymerization and Etching of Poly(lactic acid) via TiCl4 Vapor Phase Infiltration.

This study investigates the use of TiCl4 vapor phase infiltration (VPI) to cleave ester groups in the main chain of a polymer and drive depolymerization and film etching. Prior investigations have demonstrated that the infiltration of TiCl4 into PMMA results in dealkylation of its ester bond, cleaving its side groups. This study investigates the VPI of TiCl4 into poly(lactic acid), which is a prototypical polymer with an ester group in its main chain. Utilizing in situ quartz crystal microbalance (QCM) measurements and spectroscopic ellipsometry, PLA is observed to depolymerize readily at 135 °C with extended TiCl4 precursor exposure, resulting in significant thickness and mass reduction, whereas at 90 °C, depolymerization is significantly slower and etching is negligible. Utilizing Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and a residual gas analyzer (RGA), dealkylation is shown to be the primary depolymerization mechanism. FTIR and XPS analyses reveal the consumption of carbonyl and methoxy groups and the emergence of hydroxyl, chlorine, and titanium moieties. In situ RGA measurements provide further insights into the byproducts formed during the TiCl4 and water exposure steps, indicating that the depolymerized components undergo further breakdown into other substances. Residuals left after 135 °C TiCl4 VPI are easily removed with a 0.1 M HCl aqueous solution. These findings highlight the expanding functionality of VPI, revealing its capability as both an additive and subtractive process and suggesting its broader applications.

Development of Alginate Hydrogels Incorporating Essential Oils Loaded in Chitosan Nanoparticles for Biomedical Applications.

A hybrid alginate hydrogel-chitosan nanoparticle system suitable for biomedical applications was prepared. Chitosan (CS) was used as a matrix for the encapsulation of lavender (Lavandula angustifolia) essential oil (LEO) and Mentha (Mentha arvensis) essential oil (MEO). An aqueous solution of an acidic Natural Deep Eutectic Solvent (NADES), namely choline chloride/ascorbic acid in a 2:1 molar ratio, was used to achieve the acidic environment for the dissolution of chitosan and also played the role of the ionic gelator for the preparation of the chitosan nanoparticles (CS-NPs). The hydrodynamic diameter of the CS-MEO NPs was 130.7 nm, and the size of the CS-LEO NPs was 143.4 nm (as determined using Nanoparticle Tracking Analysis). The CS-NPs were incorporated into alginate hydrogels crosslinked with CaCl2. The hydrogels showed significant water retention capacity (>80%) even after the swollen sample was kept in the aqueous HCl solution (pH 1.2) for 4 h, indicating a good stability of the network. The hydrogels were tested (a) for their ability to absorb dietary lipids and (b) for their antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens. The antimicrobial activity of the hybrid hydrogels was comparable to that of the widely used food preservative sodium benzoate 5% w/v.

Electrochemical and theoretical evaluation of loratadine as corrosion inhibitor for X65 steel in 1M HCl aqueous solution

Currently oil industry infrastructure, mainly fabricated in carbon steel alloys, is exposed to aggressive environments due to the use of acid solutions during cleaning and maintenance operations, the search for eco friendly, economic and efficient protection alternatives is an active field of research in corrosion science. In this work the use of loratadine (C22H23ClN2O2) as corrosion inhibitor for X65 steel in acidic media at room temperature is studied by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Surface analysis was carried out using scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). Theoretical calculations (density functional theory, DFT) were used to elucidate the interaction between loratadine and an iron cluster model. Inhibitor efficiency increases with concentration reaching a maximum value of 93.69% according to PDP and 85.21% according to EIS. Thermodynamic analysis revealed that free energy of adsorption (ΔGads) corresponds to a mixed adsorption process. Furthermore, the seven membered ring, pyridine and chlorophenyl groups were determined as the preferential active sites. Additionally, electrostatic interactions due to the transference from metal atoms to the organic molecules explains the physical interaction.

ЕЛЕКТРОХІМІЧНІ ПАРАМЕТАРИ МОДИФІКОВАНОГО АМОРФНОГО СПЛАВУ У ВОДНИХ РОЗЧИНАХ РІЗНОЇ ПРИРОДИ

Amorphous metal alloys (AMА) have high corrosion resistance, which can be significantly higher than that of stainless steels. Since ferromagnetic amorphous Fe-based alloys are widely used as soft magnetic materials, their operation is associated with the use of external magnetic fields. Such external influences can change, in particular, the corrosion resistance of amorphous materials. In addition to permanent, amorphous materials can be under the influence of variable magnetic fields. Preliminary exposure in magnetic fields, in particular, alternating ones, can be used to modify AMА. In this regard, electrochemical studies of AMА Fe80Si6B14 in various aggressive environments are appropriate. The search for optimal modes of modification to achieve the given physicochemical properties of the samples makes it possible to change their corrosion resistance. The features of the corrosion resistance of the ribbon amorphous alloy Fe80Si6B14, obtained by the method of ultra-fast cooling of the melt, were studied, for which the contact and external surfaces, which have different elemental composition and properties, are distinguished. Electrochemical studies of AMА electrodes in 0.5 M aqueous solutions of NaCl, НCl and NaОН were carried out by the method of chronopotentiometry and cyclic voltammetry using the Jaissle Potentiostat-Halvanostat IPM 88 PC-R potentiostat. The modification of samples of Fe80Si6B14 strip amorphous alloy was carried out by keeping them in an alternating magnetic field (frequency 50 Hz) for 0.5–3.0 hours. The corrosion resistance of the Fe80Si6B14 strip amorphous alloy modified by an alternating magnetic field in 0.5 M aqueous solutions of NaCl, NaOH and HCl was investigated by various electrochemical methods. It is shown that the corrosion resistance of the tape significantly depends on the duration of the modification and the nature of the aggressive environment. Higher corrosion resistance of Fe80Si6B14 samples modified by a variable magnetic field in 0.5 M aqueous HCl solution was established. The ribbon amorphous Fe80Si6B14 alloy shows exceptional durability to long-term modification in an alternating magnetic field with the subsequent stay of the samples in 0.5 M aqueous solutions of NaOH and HCl.

Exploring the Corrosion Potential of Three Bio-Based Furan Derivatives on Mild Steel in Aqueous HCl Solution: An Experimental Inquiry Enhanced by Theoretical Analysis.

This research deals with the corrosion inhibition of mild steel in a highly corrosive aqueous HCl medium with a concentration of 0.5 M, using three different corrosion inhibitors: furan-2-carboxylic acid (1), furan-2,5-dicarboxylic acid (2), and furan-2,5-diyldimethanol (3). Various electrochemical tests, such as potentiodynamic polarization (PP or Tafel curve) and electrochemical impedance spectroscopy, were systematically performed. The experimental results underscore the remarkable corrosion mitigating properties of inhibitors 1-3 on mild steel, showing inhibition efficiencies of 97.6, 99.5, and 95.8%, respectively, at a concentration of 5 × 10-3 M and temperature T = 298 K. Notably, the inhibition efficiency of each inhibitor 1-3 shows a positive correlation with its concentration. In addition, consistent results from all electrochemical methods confirm that 1-3 act as mixed inhibitors. These findings remain robust across different experimental techniques, ensuring the reliability and comprehensiveness of the results. Theoretically, the inhibitors were optimized using the Density Functional Theory/B3LYP/6-311++G(d,p) method in gas and aqueous phase to evaluate their reactivity and stability. Among them, compound 2 stands out for its enhanced reactivity and stability, highlighted by optimal EHOMO and ELUMO values. Negative electrostatic potential mapping suggests potential reaction centers, while Fukui functions reveal localized sites of reactivity, supported by a favorable electronic distribution and specific interactions with metal surfaces. Reduced density gradient analysis also confirms the suitability of this compound for noncovalent interactions, in agreement with experimental data.These theoretical results are in good agreement with experimental data, confirming the excellent performance of compound 2 as a corrosion inhibitor.

Evaluation of fouling phenomena and cation-exchange membrane cleaning in Donnan dialysis for separation of ammonium from fermented solutions rich in volatile fatty acids

Polyhydroxyalkanoates (PHA) are promising biobased and biodegradable alternatives to the petroleum-based plastics. For their production, controlling cell growth is crucial and can be achieved by limiting nutrients, such as ammonium. The use of Donnan dialysis (DD) has been considered for this purpose. However, the effects of long–term DD fermentative operations need to be evaluated since fouling and sorption phenomena can affect the process performance. In this study, DD operations were performed over 10 consecutive batches to separate ammonium from a real fermented stream derived from an acidogenic fermentation process using cation-exchange membranes with distinct properties (a homogenous Fumasep FKS–PET-130 and a heterogenous Ralex CMH-PES) and NaCl or HCl aqueous receiver solutions. A cleaning procedure with acidic and alkaline solutions was proposed for the Ralex. It was verified that sorption and fouling phenomena occurred on/inside both membranes using a NaCl solution as receiver. This occurred more intensely with the Ralex, thus reducing the ammonium percent extraction from 55% (first batch) to approximately 40% in the subsequent batches. On the other hand, Fumasep exhibited higher percent extractions, and its values remained constant at around 65% along the batches when only rinsed with distilled water. The proposed cleaning procedure for Ralex effectively regenerated this membrane and increased the subsequent ammonium percent extractions. However, the acidic and/or alkaline solutions formed cavities on/in the membrane. The use of a HCl solution as receiver led to a lower reduction in the percent extraction throughout the batches when compared to NaCl, but the acidic receiver solution also damaged the membrane. It is suggested the use of the Fumasep membrane for the application evaluated herein or that a milder cleaning procedure is developed and applied for the Ralex membrane.

Photocatalytic Acetylene Hydrochlorination by Pairing Proton Reduction and Chlorine Oxidation over g-C3N4/BiOCl Catalysts.

Acetylene hydrochlorination is a vital industrial process for the manufacture of vinyl chloride monomer (VCM). Current thermocatalytic acetylene hydrochlorination requires toxic mercury-based or costly noble metal-based catalysts, high temperatures (≥180 °C) and excessive gaseous HCl. Here, we report a room-temperature photocatalytic acetylene hydrochlorination strategy involving concurrent coupling of electron-driven proton reduction (*H) and hole-driven chloride oxidation (*Cl) on photocatalyst surfaces. Under simulated solar light illumination, the developed noble-metal-free g-C3N4/BiOCl photocatalysts show a considerably high VCM production rate of 1198.6 μmol g-1 h-1 and a high VCM selectivity of 95% in a 0.1 M HCl aqueous solution. Even in chloride-rich natural seawater and acidified natural seawater, the VCM production rates of g-C3N4/BiOCl photocatalysts are up to 170.3 μmol g-1 h-1 with a VCM selectivity of 80.4% and 1247.7 μmol g-1 h-1 with a VCM selectivity of 94.7%, respectively. Moreover, with sunlight irradiation and acidified natural seawater, the g-C3N4/BiOCl photocatalysts in a large-scale photosystem retain outstanding acetylene hydrochlorination performance over 10 days of operation. The radical scavenging, in situ photochemical Fourier transform infrared spectroscopy, theoretical simulations, and control experiments reveal that active *Cl and *H play key roles in photocatalytic acetylene hydrochlorination via a possible reaction pathway of C2H2 → *C2H2 → *C2H2Cl → *C2H3Cl → C2H3Cl. With respect to sustainability and low cost, this photocatalytic acetylene hydrochlorination offers excellent advantages over conventional thermocatalytic hydrochlorination technologies.

Complexation of ThoriumIV with Fluorinated Heterocyclic β‐Diketones in Aqueous Hydrochloric Solutions

AbstractThe interaction of Thorium(IV) with a group of non‐symmetric CF3‐diketones has been studied by means of electronic absorption spectroscopy in HCl aqueous solutions at I=0.5 M (NaCl) and T=298 K. Six heterocyclic dicarbonyl ligands (2‐thenoyl‐trifluoroacetone, 2‐furoyl‐trifluoroacetone, 2‐selenophen‐trifluoroacetone, 2‐tellurophen‐trifluoroacetone, phenyl‐trifluoroacetone, and 2‐naphthyl‐trifluoroacetone) demonstrate the chelation activity toward ThIV in the acidic pH range. Obtained values of the “true” stability constants lie in the range 6.2–6.8 logarithmic units, respectively. A significant (10–15 nm) bathochromic shift between the maximum absorption wavelength of lanthanide and actinide monocomplexes has been detected. Observed spectral shift increases with the atomic number of substituted chalcogen atoms in the heterocyclic ring of the corresponding ligand: 10 nm for furan, 11 nm for thiophen, 14 nm for selenophen, and 15 nm for tellurophene rings. The complexation with Thorium occurs in an acidic media, where studied ligands do not interact with transition and rare earth metals. Spectral and pH shifts make studied ligands useful reagents for the detection and analytical determination of Thorium in the mixture with other metals without prior separation. Quantum‐chemical simulations (DFT and TD‐DFT) demonstrate that the nine‐ and deco‐coordinated structures of ThoriumIV complexes reproduce experimental values within reasonable errors.

Synthesis of Oxadihydrophenanthroquinolizidinones by Photoinduced Rearrangement of 3‐Biphenyl‐1‐hydroxypropyl‐pyridin‐2(1H)‐ones

Synthesis of Oxadihydrophenanthroquinolizidinones by Photoinduced Rearrangement of 3‐Biphenyl‐1‐hydroxypropyl‐pyridin‐2(1H)‐ones

Eco-friendly corrosion inhibition of steel in acid pickling using Prunus domestica Seeds and Okra stems extracts

The corrosion inhibition process during acid pickling in petroleum industries often employs toxic chemicals, facing stringent environmental regulations. This study explores a sustainable alternative by investigating the inhibitory effects of eco-friendly food waste extracts, namely Prunus domestica seeds (P.S) and Okra stems (O.St), on B7 grade steel corrosion in 1.0 M HCl aqueous solution, simulating an acid pickling environment. The corrosion inhibition efficiency was estimated via both electrochemical methods, including electrochemical impedance spectroscopy and potentiodynamic polarization techniques, and chemical methods, such as weight loss measurements. Fourier transform infrared spectroscopy (FTIR) and Gas chromatography-mass spectrometry (GC-MS) elucidated the extracts' main functional groups and potential chemical constituents. Remarkably, both extracts exhibited a maximum inhibitory efficiency of up to 80 %. Adsorption isotherms were employed to analyze the inhibition mechanisms, including Langmuir and Flory–Huggins models, alongside the Kinetic-thermodynamic model. Activation parameters have been obtained using Arrhenius and transition state equations. The synthesis of the activated complex is characterized as an endothermic process, as evidenced by the positive values of enthalpy of activation (ΔH*). Conversely, negative entropy of activation (ΔS*) values indicate that the activated complex signifies a process of association rather than separation. Quantum chemical calculations identified potential active inhibitor compounds within the extracts. The quantum parameters, including ionization potential, electronegativity, softness, and hardness of the chemical constituents of the extracts, were calculated using DFT with the B3LYP/6–31 G(+) method. This study underscores the innovative approach of utilizing waste food extracts as corrosion inhibitors, addressing environmental concerns while offering practical implications for industrial applications.

Electron Diffraction Tomography on Two-Phase Nanolamellae of Topochemically Synthesized Cu(Sb2S3)Cl.

The dark red semiconductor Cu(Sb2S3)Cl was obtained by leaching the layered precursor Cu(Sb2S3)[AlCl4] in a 0.1 M aqueous HCl solution. The selective extraction of AlCl3 yielded a mica-like lamellar product of poor crystallinity. Misalignment of lamellae down to the nanoscale prevented structure determination by conventional single-crystal X-ray diffraction, but a combination of transmission electron microscopy, selected area electron diffraction, and selected area electron precession diffraction tomography on a nanoscale spot with largely ordered crystalline lamellae revealed the crystal structures of two intergrown modifications. Orthorhombic o-Cu(Sb2S3)Cl and monoclinic m-Cu(Sb2S3)Cl have similar layers to the precursor and differ only in the stacking of the layers. These consist of uncharged Sb2S3 strands, whose sulfide ions, together with chloride ions, coordinate the copper(I) cations. Only one chloride ion remained from the [AlCl4]- group. DFT calculations confirm the structure solution for the orthorhombic form and suggest that the monoclinic structure is metastable against transformation to o-Cu(Sb2S3)Cl.

Desorption of rare earth elements biosorbed on Euglena mutabilis suspensions and biofilms

AbstractIncreasing demand for rare earth elements (REEs) has stimulated research on novel recovery methods from sources like industrial effluents. Our recent study demonstrated that algal biofilms are good candidates for the adsorption of REEs and that the extracellular polymeric substances (EPS) within the biofilm were a key accumulator of REEs. In this work, we measured the desorption kinetics, extents, and selectivity of REEs from the algae Euglena mutabilis in suspensions and biofilms using aqueous solutions of HCl at pH between 1.5 and 4, and Na2EDTA at pH 5. We examined the potential for reusing suspended and biofilm biomass for repeated adsorption–desorption cycles. The desorption kinetics were similar for suspensions and biofilms, with equilibrium being reached within 20 min. The extent of desorption was higher in biofilms with 86% and 95% desorption, compared to suspensions which had 72% and 74% desorption using HCl and Na2EDTA, respectively. We postulate that the difference between suspensions and biofilms is attributed to the binding sites in the EPS matrix of the biofilm being more readily protonated than those at the algal cell wall surface. Heavy REEs were found to preferentially desorb at pH 4 over lighter REEs. After 3 repeated adsorption–desorption cycles, the adsorption capacity of biofilms increased by 280% and 80% using HCl and Na2EDTA, respectively, compared to an 80% decrease in biosorption capacity for the suspension. The increase in biofilm biosorption capacity was attributed to the simultaneous desorption of divalent cations alongside REEs from the EPS increasing the number of available binding sites.

Drug Crystal Precipitation in Biorelevant Bicarbonate Buffer: A Well-Controlled Comparative Study with Phosphate Buffer.

The purpose of the present study was to clarify whether the precipitation profile of a drug in bicarbonate buffer (BCB) may differ from that in phosphate buffer (PPB) by a well-controlled comparative study. The precipitation profiles of structurally diverse poorly soluble drugs in BCB and PPB were evaluated by a pH-shift precipitation test or a solvent-shift precipitation test (seven weak acid drugs (pKa: 4.2 to 7.5), six weak base drugs (pKa: 4.8 to 8.4), one unionizable drug, and one zwitterionic drug). To focus on crystal precipitation processes, each ionizable drug was first completely dissolved in an HCl (pH 3.0) or NaOH (pH 11.0) aqueous solution (450 mL, 50 rpm, 37 °C). A 10-fold concentrated buffer solution (50 mL) was then added to shift the pH value to 6.5 to initiate precipitation (final volume: 500 mL, buffer capacity (β): 4.4 mM/ΔpH (BCB: 10 mM or PPB: 8 mM), ionic strength (I): 0.14 M (adjusted by NaCl)). The pH, β, and I values were set to be relevant to the physiology of the small intestine. For an unionizable drug, a solvent-shift method was used (1/100 dilution). To maintain the pH value of BCB, a floating lid was used to avoid the loss of CO2. The floating lid was applied also to PPB to precisely align the experimental conditions between BCB and PPB. The solid form of the precipitants was identified by powder X-ray diffraction and differential scanning microscopy. The precipitation of weak acids (pKa ≤ 5.1) and weak bases (pKa ≥ 7.3) was found to be slower in BCB than in PPB. In contrast, the precipitation profiles in BCB and PPB were similar for less ionizable or nonionizable drugs at pH 6.5. The final pH values of the bulk phase were pH 6.5 ± 0.1 after the precipitation tests in all cases. All precipitates were in their respective free forms. The precipitation of ionizable weak acids and bases was slower in BCB than in PPB. The surface pH of precipitating particles may have differed between BCB and PPB due to the slow hydration process of CO2 specific to BCB. Since BCB is a physiological buffer in the small intestine, it should be considered as an option for precipitation studies of ionizable weak acids and bases.

Isoindigo derivatives as some potential corrosion inhibitors for mild steel in hydrochloric acid solution: Synthesis, experimental and theoretical studies

This investigation synthesized two isoindigo derivatives (IIDBr-NBr and IIDBr-MBr). These derivatives were then applied as green corrosion inhibitors for mild steel in a 1 mol L−1 HCl aqueous solution. The study investigated the corrosion inhibition performance of IIDBr-NBr and IIDBr-MBr through electrochemical and weight loss (WL) measurements, as well as surface analysis (SEM, AFM and XPS). The results showed that both IIDBr-NBr and IIDBr-MBr exhibited excellent corrosion inhibition performance (inhibition efficiency of 96.27 % for IIDBr-NBr and 96.46 % for IIDBr-MBr). Quantum chemical calculations based on density functional theory (DFT) and molecular dynamics (MD) were used to reveal the adsorption mechanisms of IIDBr-NBr and IIDBr-MBr at the steel/solution interface.

The surface effect of chlorinated mesoscopic TiO2 in printable carbon-based perovskite solar cells

Printable HTM-free (HTM = hole-transporting material) mesoporous carbon-based perovskite solar cells (C-PSCs) are one of the most promising technologies. In this study, a high-quality chlorinated mesoscopic TiO2 (m-TiO2) film was obtained by hydrochloric acid (HCl) wet chemical process and applied in C-PSCs based on TiO2/ZrO2/(5-AVA)x(MA)1-xPbI3/C structures. Experimental results show that the PCE of chlorinated m-TiO2 C-PSCs greatly improved. Based on (5-AVA)x(MA)1-xPbI3, C-PSCs with TiO2 ETL treated with HCl aqueous solution achieved an average photovoltaic conversion efficiency of 9.36 %, which is an increase of 7.96 % in comparison with the efficiency of the device using unmodified TiO2 ETL, while the Voc and the Jsc were increased by 3.63 % and 2.63 %, respectively. In a 30-day aging test, C-PSCs based on (5-AVA)x(MA)1-xPbI3 and TiO2-HCl 1 exhibited excellent stability under ambient air conditions.

Transference Number of H+ in Infinitely Diluted Aqueous HCl Solutions: A Physical Chemistry Experiment for Senior Undergraduates

Transference Number of H⁺ in Infinitely Diluted Aqueous HCl Solutions: A Physical Chemistry Experiment for Senior Undergraduates

Accelerated corrosion of low carbon steel by oscillatory acidic streams generated with a bio-inspired claw device.

A mechanical device inspired by the pistol shrimp snapper claw was developed. This technology features a claw characterized by a periodic opening/closing motion, at a controlled frequency, capable of producing oscillating flows at transitional Reynolds numbers. An innovative method was also proposed for determining the corrosion rate of carbon steel samples under oscillating acidic streams (aqueous solution of HCl). By employing very-thin carbon steel specimens (25 μm thickness), with one side coated with Zn and not exposed to the stream, it became possible to electrochemically sense the Zn surface once the steel sample was perforated, thus providing the average dissolution rate into the most relevant pit on the steel surface. Furthermore, a laser light positioned beneath the metallic sample, along with a camera programmed to periodically capture images of the steel surface, facilitated the accurate counting of the number of newly formed pits. The system consisting of the thin steel sample and the Zn coating can be seen as a type of corrosion sensor. Furthermore, the proposed laser illumination method allows corroborating the electrochemical detection of pits and also establishing their location. The techniques crafted in this study pave the way for developing alternative corrosion sensors that boast appealing attributes: affordability, compactness, and acceptable accuracy to detect in time and space localized damage.

Anodic alumina/carbon composite films: extraction and characterization of the carbon-containing component

Alumina/carbon composites are modern nanomaterials used as adsorbents, catalysts, catalyst supports, supercapacitors, and electrode materials for fuel cells. Among other methods, aluminum anodizing is fairly fast and inexpensive for producing anodic alumina/carbon composites with controllable properties. In the present study, the morphology and composition of carbon-enriched anodic alumina films were obtained during aluminum anodic oxidation in formic acid with ammonium heptamolybdate (C content is ca. 5.0 mass%) or oxalic acid (C content 3.4 mass%) additives. The anodic alumina films have a wide blue fluorescence (FL) in the 400–650 nm wavelength range with a maximum at ca. 490 nm. The FL decay is nonexponential and has an average lifetime of 1.54 and 1.59 ns for ammonium heptamolybdate and oxalic acid additives, respectively. As samples obtained in sulfuric acid (i.e. without carbon) do not possess detectable FL in the 400–650 nm wavelength range, it was concluded that carbon-containing inclusions are responsible for the FL properties of the films. The initial samples were dissolved in the hot aqueous HCl solution and then dialyzed to extract the carbon-containing component. It was shown that the solutions contain nanoparticles of amorphous carbon with a 20–25 nm diameter. Carbon nanoparticles also exhibit an excitation-dependent emission behavior at 280–450 nm excitation wavelengths with average lifetimes of 7.25–8.04 ns, depending on the composition of the initial film. Carbon nanoparticle FL is caused by the core of carbon nanoparticles (CNPs) and various emission centers on their surface, such as carbonyl, carboxyl, and hydroxyl groups. As CNPs could be exceptional candidates for detection technologies, the biocompatibility assays were performed with living COS-7 mammalian cells, showing a minimal negative impact on the living cells.

Enhancing waste hemp hurd-derived anodes for sodium-ion batteries through hydrochloric acid-mediated hydrothermal pretreatment

Waste hemp hurd (WHH) was used as a sustainable feedstock for producing hard carbon-based anodes for sodium-ion batteries (SIBs). Two easily scalable production pathways were tested and compared: (1) pyrolysis (at 500 °C) and subsequent annealing at 800, 1000 or 1200 °C, and (2) hydrothermal pretreatment (at 180 °C) and subsequent annealing at the above-mentioned highest temperatures. Results indicated that when a HCl (2 mol m−3) aqueous solution was used as hydrothermal medium, the textural, structural and surface chemistry features linked to the electrochemical performance of the resulting hard carbons improved. The WHH-derived electrode produced via HCl-mediated hydrothermal pretreatment and subsequent annealing at 1000 °C showed an exceptional electrochemical performance in terms of specific capacity (535 mA h g−1 at 30 mA g−1) and rate capability (372, 156, 115, and 83 mA h g−1 at 0.1, 0.5, 1, and 2 A g−1, respectively) when an ester-based electrolyte was used (NaTFSI in EC/DMC). Using an ether-based electrolyte (NaPF6 in diglyme) improved both the ICE (from 69% to 78%) and cycling stability (85% of capacity retention after 300 cycles at 1 A g−1; 91% when current rate returned to 0.1 A g−1). In summary, relatively low-cost WHH-derived carbons are able to deliver an exceptional performance, much better than that reported so far for other biomass-derived carbons, and even close to that exhibited by more expensive and complex composite and hybrid materials.