Co-pyrolysis of wood chips and bentonite/kaolin: Influence of temperatures and minerals on characteristics and carbon sequestration potential of biochar

Biochars have been highlighted as a means of carbon sequestration, which is significant for achieving carbon neutrality. Mixtures of wood chips and either bentonite or kaolin were co-pyrolysed at temperatures of 350 °C and 550 °C, and the microstructural characteristics and the carbon sequestration potential of the resultant biochar were explored in the study. The addition of minerals promoted the formation of a stable carbon structure in biochar, especially the proportion of SiC bonds in the high-temperature mineral-composited biochar increased by 3.56-3.82 times compared with the original biochar. After bentonite or kaolin was added to wood chips pyrolysed at 550 °C, the carbon loss after H₂O₂ oxidation was reduced to no more than 19.2%, and the Recalcitrance Index (R₅₀) of biochar increased to no less than 0.89. The combined action of high temperature and minerals promoted the formation of highly aromatic structures of biochar (H:C < 0.4) and reduced the amount of dissolved organic carbon to 4.89 mg g^-1. Furthermore, minerals directly covered the surface of biochar, and the content of SiC bond increased, thus strengthening the chemical and thermal stability of biochar. However, the addition of minerals had no significant effect on the biological stability of biochar. The study indicates that the pre-pyrolysis mineral addition is an effective way to increase the carbon sequestration potential of biochar.

Mesoporous Biopolymer Architecture Enhanced the Adsorption and Selectivity of Aqueous Heavy-Metal Ions

Halloysite nanotubes (HNT) and ball-milled biochar (BC) incorporated biocompatible mesoporous adsorbents (HNT-BC@Alg) were synthesized for adsorption of aqueous heavy-metal ions. HNT-BC@Alg outperformed the BC, HNT, and BC@Alg in removing cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb). Mesoporous structure (∼7.19 to 7.56 nm) of HNT-BC@Alg was developed containing an abundance of functional groups induced from encapsulated BC and tubular HNT, which allowed heavy metals to infiltrate and interact with the adsorbents. Siloxane groups from HNT, oxygen-containing functional groups from BC, and hydroxyl and carboxyl groups from alginate polymer play a significant role in the adsorption of heavy-metal ions. The removal percentage of heavy metals was recorded as Pb (∼99.97 to 99.05%) > Cu (∼95.01 to 90.53%) > Cd (∼92.5 to 55.25%) > Ni (∼80.85 to 50.6%), even in the presence of 0.01/0.001 M of CaCl₂ and Na₂SO₄ as background electrolytes and charged organic molecule under an environmentally relevant concentration (200 μg/L). The maximum adsorption capacities of Ni, Cd, Cu, and Pb were calculated as 2.85 ± 0.08, 6.96 ± 0.31, 16.87 ± 1.50, and 26.49 ± 2.04 mg/g, respectively. HNT-BC@Alg has fast sorption kinetics and maximum adsorption capacity within a short contact time (∼2 h). Energy-dispersive X-ray spectroscopy (EDS) elemental mapping exhibited that adsorbed heavy metals co-distributed with Ca, Si, and Al. The reduction of surface area, pore volume, and pore area of HNT-BC@Alg (after sorption of heavy metals) confirms that mesoporous surface (2-18 nm) supports diffusion, infiltration, and interaction. However, a lower range of mesoporous diameter of the adsorbent is more suitable for the adsorption of heavy-metal ions. The adsorption isotherm and kinetics fitted well with the Langmuir isotherm and the pseudo-second-order kinetic models, demonstrating the monolayer formation of heavy-metal ions through both the physical sorption and chemical sorption, including pore filling, ion exchange, and electrostatic interaction.

Fabrication of highly and poorly oxidized silver oxide/silver/tin(IV) oxide nanocomposites and their comparative anti-pathogenic properties towards hazardous food pathogens

Herein, we report the fabrication of highly oxidized silver oxide/silver/tin(IV) oxide (HOSBTO or Ag³⁺-enriched AgO/Ag/SnO₂) nanocomposite under a robust oxidative environment created with the use of concentrated nitric acid. Tin(IV) hydroxide nanofluid is added to the reaction mixture as a stabilizer for the Ag³⁺-enriched silver oxide in the nanocomposite. The formation of Ag nanoparticles in this nanocomposite originates from the decomposition of silver oxides during calcination at 600 °C. For comparison, poorly oxidized silver oxide/silver/tin(IV) oxide (POSBTO with formula AgO/Ag/SnO₂) nanocomposite has also been prepared by following the same synthetic procedures, except for the use of concentrated nitric acid. Finally, we studied in detail the anti-pathogenic capabilities of both nanocomposites against four hazardous pathogens, including pathogenic fish bacterium (Stenotrophomonas maltophilia stain EP10), oomycete (Phytophthora cactorum strain P-25), and two different strains of pathogenic strawberry fungus, BRSP08 and BRSP09 (Collectotrichum siamense). The bioassays reveal that the as-prepared HOSBTO and POSBTO nanocomposites exhibit significant inhibitory activities against the tested pathogenic bacterium, oomycete, and fungus in a dose-dependent manner. However, the degree of dose-dependent effectiveness of the two nanocomposites against each pathogen largely varies.

Passivation by pyridine-induced PbI2 in methylammonium lead iodide perovskites

Defects at discontinuities of the perovskite lattice limit the performance of the perovskite solar cell (PSC). Lead iodide (PbI₂) and pyridine have been shown to passivate these defects. We treat methylammonium lead iodide (MAPbI₃) films with pyridine solutions to investigate the effects of the two passivators. By comparing confocal fluorescence microscopy (CFM) images at 405 nm excitation and then at 559 nm excitation we demonstrate the pyridine treatment passivates and forms PbI₂ crystallites which cause additional passivation.

Comparison of confocal fluorescence microscope (CFM) images at different excitation wavelengths show localized passivation effects by a pyridine treatment on a perovskite precursor, PbI₂.

Physical characteristics of capacitive carbons derived from the electrolytic reduction of alkali metal carbonate molten salts

Carbons have been synthesized through the reduction of molten carbonate systems under varied conditions. The mechanism and kinetics of carbon electrodeposition has been investigated. Carbon morphologies include amorphous, graphite-like, and spherical aggregate phases. Increased graphitic character is observed in carbons electrodeposited at more cathodic potentials, particularly at higher temperatures. Bonding has been investigated and oxygen functionalised sp² and sp³ structures have been identified. The level of functionalization decreases in carbons with reduced amorphous and increased graphitic character. Thermal decomposition of electrodepositied carbons has been investigated and zero order kinetics have been identified. A relationship has been identified between elevated oxygen functionalization and increased pseudo-capacitance, with carbons deposited at 0.15 A cm⁻² showing capacitances of 400 F g⁻¹ in 0.5 M H₂SO₄ at sweep rates of 10 mV s⁻¹.

Carbons have been synthesized through the reduction of molten carbonate systems under varied conditions.

Influence of red mud on mechanical and durability performance of self-compacting concrete

Red mud is a hazardous waste material produced during alkaline leaching of bauxite in the Bayer process. This study proposed the use of red mud to replace fly ash in self-compacting concrete (SCC) and the influences of red mud on fresh and hardened properties, and durability performances of SCC were studied. The fresh concrete results show that red mud had a slight negative impact on the fresh properties of SCC. The hardened concrete results show that the mechanical strength of concrete increased with increasing of red mud content. The half-cell potential test results indicated that red mud had a significant effect on restraining the corrosion process in SCC. Compared to the control sample, the red mud samples suffered less corrosion. Cracks associated with corrosion of reinforcement were observed in RMC0 and RMC100 samples after 28 day accelerated corrosion test. The ICP-MS results showed that there's no significant difference in metal elements among the solutions regardless the red mud content in concrete.The relative corrosion rate test results suggested that red mud can suppress the corrosion current. The SCC samples consisting 75% red mud performed the best resistance to corrosion according to the results of half-cell potentials and mass loss of rebar.

Thermal stability of biochar and its effects on cadmium sorption capacity

In this study, the thermal stability of a wood shaving biochar (WS, 650°C), a chicken litter biochar (CL, 550°C) and an activated carbon (AC, 1100°C) were evaluated by combustion at 375°C for 24h to remove the labile non-carbonized organic matter. Results showed that WS and CL biochars were not thermally stable and can lose most of the organic C during combustion. The combusted WS and CL biochars retained considerable amounts of negative charge and displayed higher sorption for Cd (from 5.46 to 68.9mg/g for WS and from 48.5 to 60.9mg/g for CL). The AC retained 76.5% of its original C and became more negatively chargely after combustion, but its sorption for Cd slightly decreased (from 18.5 to 14.9mg/g). This study indicated that after potential burning in wildfires (200-500°C), biochars could have higher sorption capacity for metals by remaining minerals.

Preparation and Binding Evaluation of Histamine-Imprinted Microspheres via Conventional Thermal and RAFT-Mediated Free-Radical Polymerization

Elevated histamine (HTM) levels are closely linked to food poisoning as well as to pathophysiological allergic diseases. In this study, HTM-imprinted, solution-processable microspheres were prepared via high-dilution conventional thermal polymerization (CTP) and controlled radical polymerization (CRP) using ethylene glycol dimethacrylate (80 or 90 wt %) and methacrylic acid at 60 °C in acetonitrile and evaluated as recognition materials for sensing applications. The polymers were selective to HTM in binding studies, cross-rebinding, and competitive binding assays against the HTM analogues histidine, imidazole, and tryptamine. The selective binding capacity was significantly higher with CTP-80 (on the basis of mass: 21.0 μmol/g and surface area: 8.08 × 10^-2 μmol/m²) than that with both CTP-90 (8.47 μmol/g, 4.49 × 10^-2 μmol/m²) and CRP-80 (9.00 μmol/g, 1.19 × 10^-2 μmol/m²).

Molecular structures driving pseudo-capacitance in hydrothermal nanostructured carbons

The incorporation of nitrogen into hydrothermal carbon with (NH₄)₂SO₄ is shown to have a significant influence on the chemical composition and surface characteristics of hydrothermal carbon.

Thermal expansion of manganese dioxide using high-temperaturein situX-ray diffraction

High-temperaturein situX-ray diffraction is used to determine the thermal expansion behaviour of manganese dioxide in air at temperatures between 298 and 673 K, the range accessible prior to material decomposition. Two manganese dioxide samples of different origins are investigated to observe the effect of synthesis conditions and resultant material properties on the thermal response. β-MnO2prepared by a chemical pathway is found to expand linearly over the temperature window with thermal expansion coefficients (in units of K−1) of αa= 9.3 (4) × 10−6, αc= 7.0 (2) × 10−6and β = 25.6 (8) × 10−6. Conversely, the thermal expansion of heat-treated electrolytic manganese dioxide is disjointed about 473 K in theadirection and for the overall unit-cell volume, and about 523 K in thecdirection. Coefficients are therefore given (in units of K−1) as αa= 23 (4) × 10−6(298–473 K), 10 (3) × 10−6(473–673 K); αc= 0.2 (9) × 10−6(298–523 K), 10 (1) × 10−6(523–673 K); and β = 49 (9) × 10−6(298–473 K), 26 (5) × 10−6(473–673 K).

Potassium accumulation between type I hair cells and calyx terminals in mouse crista

The mode of synaptic transmission in the vestibular periphery, between type I hair cells and their associated calyx terminal, has been the subject of much debate. The close and extensive apposition of pre- and post-synaptic elements has led some to suggest potassium (K(+)) accumulates in the intercellular space and even plays a role in synaptic transmission. During patch clamp recordings from isolated and embedded hair cells in a semi-intact preparation of the mouse cristae, we noted marked differences in whole-cell currents. Embedded type I hair cells show a prominent droop during steady-state activation as well as a dramatic collapse in tail currents. Responses to a depolarizing voltage step (-124 to +16 mV) in embedded, but not isolated, hair cells resulted in a >40 mV shift of the K(+) equilibrium potential and a rise in effective K(+) concentration (>50 mM) in the intercellular space. Together these data suggest K(+) accumulation in the intercellular space accounts for the different responses in isolated and embedded type I hair cells. To test this notion, we exposed the preparation to hyperosmotic solutions to enlarge the intercellular space. As predicted, the K(+) accumulation effects were reduced; however, a fit of our data with a classic diffusion model suggested K(+) permeability, rather than the intercellular space, had been altered by the hyperosmotic change. These results support the notion that under depolarizing conditions substantial K(+) accumulation occurs in the space between type I hair cells and calyx. The extent of K(+) accumulation during normal synaptic transmission, however, remains to be determined.

Surface characterization of heat-treated electrolytic manganese dioxide

In this work a titration technique was used to determine the amphoteric surface properties of a series of heat-treated electrolytic manganese dioxide (EMD) samples (up to 500 degrees C). The surface of each sample was found to consist of independent acidic and basic hydroxyl sites, which could be characterized by their respective equilibrium constants and site concentrations. It was found that the acidic sites could not be characterized by a single equilibrium constant, but rather by a distribution indicating the subtle differences between individual sites, while a single equilibrium constant adequately represented the basic sites. For EMD, K(a) varied between 0.1 and 6.3x10(-5), with a corresponding [MnOH((a)T)] value varying between 9.1 and 6.4x10(-6) mol m(-2) over the pH range considered. K(b) and [MnOH((b)T)] were found to be 1.81x10(-9) and 1.93x10(-5) mol m(-2), respectively. With heat treatment, K(a) increased, suggesting a strengthening of the MnO bond via the removal of defects such as Mn(3+) ions and cation vacancies. The fact that K(b) also increased was initially counterintuitive because it suggested that the MnO bond had been weakened by heat treatment. However, assuming that the acidic and basic hydroxyl groups are independent, the trends in K(b) could be rationalized in terms of oxygen ion coordination in the progressively heat-treated samples. The number of surface sites (N(s)) was determined crystallographically and from the sum [MnOH((a)T)] + [MnOH((b)T)]. The data from both methods were of the same order of magnitude but exhibited different trends due to certain inadequacies in both methods. However, the data trends did indicate that the crystal planes at the particle surface could be changing with heat treatment due to a decrease in the value of N(s) determined from the surface titrations. Electrochemical analysis of the samples in 9 M KOH indicated that their performance degraded considerably with heat treatment. In comparison with the surface titration data, it was concluded that proton insertion into the structure occurred only through basic surface sites, the decreasing number of which could limit performance.