Properties of the solid thermolysis products of brown coal impregnated with an alkali

The mechanism of formation of a porous active carbon framework is considered, and the properties of the solid thermolysis products of brown coal (Aleksandriisk deposit, Ukraine) with potassium hydroxide are studied. The yields of the solid thermolysis products (Y _STP, %) and potassium humates, the rate of the interaction of the solid thermolysis products with KOH at 700–900°C, the specific surface areas (S _BET, m²/g), the adsorption capacities for methylene blue (A _MB, mg/g) and iodine (A _I, mg/g), and the specific activities of surface areas A _MB ^′ = A _MB/S _BET and A _I ^′ = A _I/S _BET (mg/m²) are determined under variation of the KOH/coal ratio (R _KOH < 18 mol/kg) and temperature (110–900°C).     

Adsorbents from lignin and washed-off petroleum waste

The properties of active carbons, products of the steam activation (400–900°C) of mixtures of washed-off petroleum waste and lignin, were studied. The dependences of the yield, the specific surface area, and adsorption activity with respect to iodine (A _I) and methylene blue (A _MB) on the activation temperature (400–900°C), as well as the characteristics of the pore systems and the parameters of active-carbon supermolecular structure, were obtained. As compared with the properties of active carbon from lignin, the activation of the mixture leads to the formation of active carbon with lower yields, a higher specific surface area, and a substantially (by a factor of 3) increased proportion of mesoporosity. The adsorption properties of active carbons from lignin and its mixture with washed-off petroleum waste are close (A _I = 950?1000 mg/g and (A _MB = 200?220 mg/g).     

IR Spectroscopy in Rank and Group Assignment of Coal

The possibility of express determination of the characteristics V _IR ^daf , R_{o, IR}, y_IR, ΣLC_IR, and A _IR ^d used in the ranking of coal on the basis of IR spectroscopy is assessed for a specific example: Kuznetsk coals of different maceral composition and metamorphic development. The IR characteristics are compared with values obtained by standard methods (V^daf, R_{o, r, y}, ΣLC, and A^d).     

Production and Use of Lignite-Based Coke Briquets with High Hot Strength

A production technology has been developed for strong briquets (with high CSR and M₂₅) based on coke derived from Kansko-Achinsk lignite. A mixture consisting of lignite coke and binder (Zh and KZh coal) is crushed (to particle size less than 0.2 mm) and mixed with strengthening additive. This blend (57.7% lignite coke + 19.2% binder + 23.1% additive) is shaped into briquets, which are roasted at 1000°C and cooled in the absence of air. For the briquets, CSR = 58.8% and M₂₅ = 97.4%. The strength in drop tests is 99.1%, and the wear resistance is 99.2%. Technical analysis of the briquets shows that W = 1–2%, A^d = 8–10%, V^daf = 3–7%, S^d = 0.2–0.4%, P^d = 0.014%, and C_fix = 85–88%. The briquets are characterized by distinctive physicochemical properties, such as high activity with respect to CO₂ (\(K_{CO_2}\) = 4.6 cm³/g s; CRI = 66.1%). Its electrical resistivity ρ = 8 Ω cm for the 3–6 mm size class; and its developed porosity is 50–56%. Applications of the briquets are outlined.     

Assessing the technological value of coal in coking

Coking coal of the same rank from different countries and fields may be distinguished in terms of use value by rating on the basis of seven technological and petrographic characteristics that determine the coke yield and properties: the ash content A^d; the total sulfur content S_t^d; the yield of volatiles V^daf; the plastic-layer thickness y; the vitrinite reflection coefficient R_o; the content of vitrinite-group macerals Vt; and the basicity index B_b. A range of values and a rating (on a scale from 1 to 10) are established for each of these parameters. Each rating corresponds to a particular score (from 0.1 to 1.0). Ranges of A^d, S_t^d, Vt, and B_b are established for the whole metamorphic series, while ranges of V^daf, y, and R_o are established for individual ranks and groups of ranks. Altogether, 105 coking coals from Ukraine, Russia, the United States, Australia, and Canada that are used at Ukrainian coke plants are investigated. The range of rating scores and their mean values are determined for individual coal ranks and groups. As an example, three bituminous coals from Ukraine, the United States, and Australia are compared by the proposed method. This method permits objective assessment of the technological value of coal within a single rank and the selection of the best purchase option.     

Synthesis of polyamine-grafted chitosan and its adsorption behavior

The development of new environment-friendly and efficient adsorbents has attracted a great interest in recent years. In this study, ethylene diamine-grafted chitosan copolymer (CS–MAA–EN) and triethylene tetramine-grafted chitosan copolymer (CS–MAA–TN) were synthesized to remove heavy metal ions from water. The influence of pH, adsorbents dosage and initial metal concentration were investigated to study the adsorbing effect of CS–MAA–EN and CS–MAA–TN for the removal of Cu²⁺ from aqueous solutions. The equilibrium adsorption capacities of CS–MAA–EN and CS–MAA–TN were 85.91 and 102.67 mg/g, respectively. The adsorption process was fitted better by the Langmuir isotherm model (R ² = 0.9993, 0.9991) than the Freundlich isotherm model (R ² = 0.8781, 0.8775). The adsorption kinetics confirmed that the adsorption mechanism could be better described by the pseudo-second-order equation. Two adsorbents showed excellent desorption efficiency (D _e) and reuse ratio (R _u). D _e and R _u of CS–MAA–EN were evaluated as 95.2 and 89.35 %, respectively, and those values of CS–MAA–TN were 92.73 and 83.25 %. The competitive adsorption results of the two adsorbents indicated that the rate sequence was Fe³⁺ > Cu²⁺ > Cr⁶⁺ > Ni²⁺ > Zn²⁺.     

Determining the petrographic inhomogeneity of mixed-rank coal

It is shown that the inhomogeneity of coal mixtures (enrichment-plant concentrates) differing in vitrinite reflection coefficient and the content of clinkering components (i.e., in the deviation of these parameters S _R and S _CC ) may only be objectively estimated on the basis of refractogram and petrographic analysis of bed samples of the coal from the mines that supply the enrichment plant. A method and corresponding program for calculating S _R and S _CC is proposed. This program permits correct determination of the petrographic inhomogeneity of coal batch, which is important in evaluating the influence of this factor on coal quality.     

Relations between the reflection coefficients of the basic groups of macerals: A review

Quantitative relations are found between the structural and chemical characteristics of macerals of the basic coal groups (vitrinite Vt, inertinite I, liptinite L), on the one hand, and their reflection coefficients R _r and the corresponding dispersions σ _R , on the other. For coal of a particular metamorphic stage, the reflection coefficient declines in the series I > Vt > L, on account of the reduction in aromatic chemical structure and in the degree of condensation of the aromatic blocks. In the metamorphic series, the reflection coefficients of the macerals rise; the values for Vt and L at intermediate stages converge. The dispersion of the reflection coefficients (and hence the reflectograms) is due to the spread in characteristics of the chemical structure of the coal’s organic content, as confirmed by calculations for the vitrinite of D, G, Zh, and K coal.     

Properties of Kuznets Basin gas coal

Six samples of G coal characterized by different vitrinite reflection coefficient (R _o,r = 0.64–0.74%) are investigated. With increase in R _o,r , the plastic-layer thickness y increases from 7 to 17 mm, the free-swelling index SI from 0.5 to 3.5, and the Roga index RI from 1 to 21. The temperature range of plasticity expands from 34 to 94°C. The results clarify the difference in clinkering properties of the gas coal.     

Influence of activation on the pore structure of adsorbents obtained from coal–alkali mixtures

The activation of carbon sorbents in CO₂ is investigated. The sorbents are produced by the thermolysis of naturally oxidized SS coal steeped in potassium hydroxide, with an alkali/coal ratio R _KOH = 0.01 and 0.05 g/g. The influence of CO₂ activation on the texture of the sorbents obtained is established. After 10-min activation, the increase in specific surface area of the sorbents is a maximum (about 100%). Longer activation increases the loss of material. The pore volume formed on activation is proportional to the proportion of carbon-bearing material removed. The volume of adsorbing pores formed in the sorbents is greatest when the loss of material is 25–35%.     

Rapid Quality Assessment of Coal

No satisfactory methods are available for rapid and reliable prediction of one or more coal characteristics. The ignition temperature t_ig of coal, determined in assessing the oxidation of coal in accordance with Ukrainian State Standard DSTU 7611:2014, may be regarded as a useful predictor of coal quality. Research shows that t_ig depends on the composition and ordering of the coal’s organic mass. Mathematical and graphical means of predicting the V ^daf and R_o values of coal are developed.     

Magnetic Field-Induced Splitting of Optical Spectra in Silicon Nanotubes: Tight Binding Calculations

The splitting of band structure and absorption spectra, for silicon nanotubes (SiNTs) under axial magnetic field, are studied using the tight binding approximation. It is found that band splitting is approximately proportional to the magnitude of magnetic field as \(\frac {\Delta E}{E_{g}}=\nu _{ii} \frac {\Phi }{{\Phi }_{0}}\) where ν _{i i} is the splitting rate. For Si g-NTs, we calculated the splitting rate of the two first bands nearest to the Fermi level in the Γ point and found that it can be fitted with a two degree polynomial as \(\nu _{ii}={\sum }_{j=0}^{2}{a^{i}_{j}}x^{j}\) where \(x=\frac {1}{n^{2}}\) and for sufficiently large diameter Si g-NTs, the ν _{i i} can be fitted by a linear function. For semiconductor Si h-NTs the ν ₁₁ = 6 but ν ₂₂ and ν ₃₃ show radial dependence. Also we found that applying magnetic field leads to splitting for all peaks in the low energy ranges for all zigzag Si h-NTs and Si g-NTs. The first peak of group (I) of Si g-NTs does not show any splitting in the magnetic field and for all metallic Si h-NTs, the magnetic field leads to creating a peak in the energy range less than 0.2 eV where this peak arises from energy gap created around Fermi energy.     

Medium optimization for high yield production of extracellular human interferon-<Emphasis Type="Italic">γ</Emphasis> from <Emphasis Type="Italic">Pichia pastoris</Emphasis>: A statistical optimization and neural network-based approach

Medium development for high level expression of human interferon gamma (hIFN-γ) from Pichia pastoris (GS115) was performed with the aid of statistical and nonlinear modeling techniques. In the initial screening, gluconate and glycine were found to be key carbon and nitrogen sources, showing significant effect on production of hIFN-γ. Plackett-Burman screening revealed that medium components., gluconate, glycine, KH₂PO₄ and histidine, have a considerable impact on hIFN-γ production. Optimization was further proceeded with Box-Behnken design followed by artificial neural network linked genetic algorithm (ANN-GA). The maximum production of hIFN-γ was found to be 28.48mg/L using Box-Behnken optimization (R²=0.98), whereas the ANN-GA based optimization had displayed a better production rate of 30.99mg/L (R²=0.98), with optimal concentration of gluconate=50 g/L, glycine=10.185 g/L, KH₂PO₄=35.912 g/L and histidine 0.264 g/L. The validation was carried out in batch bioreactor and unstructured kinetic models were adapted. The Luedeking-Piret (L-P) model showed production of hIFN-γ was mixed growth associated with the maximum production rate of 40mg/L of hIFN-γ production.     

Crystallinity of large single crystals of FAU-type zeolites with a wide range of Si/Al ratios

Large colorless single crystals of FAU-type zeolites were synthesized from gels with the composition xSiO₂ : 2.0NaAlO₂ : 7.5NaOH : 454H₂O : 5.0TEA, where x = 2.0–6.0. FAU-type zeolite with Si/Al = 1.26(4) was nearly pure and the maximum size of the single crystals was ca. 150 μm. In case of FAU-type zeolites with Si/Al = 1.54(5), the maximum size of single crystals was ca. 200 μm and the ratio of FAU/impurity was 0.07. The framework Si/Al ratio of the as-synthesized FAU-type zeolite tended to increase with the Si/Al ratio of gel composition. All of the large single crystals had good crystallinities for single-crystal X-ray diffraction, leading to enough numbers of significant reflections which have strong intensity. The structure of a single crystal of dehydrated zeolite Na-X (Si/Al = 1.41(4)) with composition |Na₈₀|[Si₁₁₂Al₈₀O₃₈₄]-FAU per unit cell was determined by X-ray diffraction methods in the cubic space group \( Fd \bar{3} m; \) a = 24.9434(6) Å at 294 K. The structure was refined by using all intensities to the final error indices (using only the 771 reflections for which F _o > 4σ(F _o)), R ₁ = 0.048 (based on F) and R ₂ = 0.188 (based on F ²). In the crystallographic studies, the Si/Al ratio of the synthetic FAU-type zeolite is 1.41(4) which is quite consistent with the SEM–EDS analysis.     

Synthesis and swelling behavior of metal-chelating superabsorbent hydrogels based on sodium alginate-<Emphasis Type="Italic">g</Emphasis>-poly(AMPS-<Emphasis Type="Italic">co</Emphasis>-AA-<Emphasis Type="Italic">co</Emphasis>-AM) obtained under microwave irradiation

A metal-chelating superabsorbent hydrogel based on poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid-co-acrylamide) grafted onto sodium alginate backbone, NaAlg-g-poly(AMPS-co-AA-co-AM) is prepared under microwave irradiation. The Taguchi method is used for the optimization of synthetic parameters of the hydrogel based on water absorbency. The Taguchi L₉ (3⁴) orthogonal array is chosen for experimental design. Mass concentrations of crosslinker MBA \(C_{\text{MBA}}\) initiator KPS \(C_{\text{KPS}}\), sodium alginate \(C_{\text{NaAlg}}\) and mass ratio of monomers \(C_{\text{AM/AA/AMPS}}\) are chosen as four factors. The analysis of variance of the test results indicates the following optimal conditions: 0.8 g L^?1 of MBA, 0.9 g L^?1 of KPS, 8 g L^?1 of NaAlg and \(R_{\text{AM/AA/AMPS}}\) equals to 1:1.1:1.1. The maximum water absorbency of the optimized final hydrogel is found to be 822 g g^?1. The relative thermal stability of the optimized hydrogel in comparison with sodium alginate is demonstrated via thermogravimetric analysis. The prepared hydrogel is characterized by FTIR spectroscopy and scanning electron microscopy. The influence of the environmental parameters on water absorbency such as the pH and the ionic force is also investigated. The optimized hydrogel is used as adsorbent for hazardous heavy metal ions Pb(II), Cd(II), Ni(II) and Cu(II) and their competitive adsorption is also discussed. Isotherm of adsorption and effect of pH, adsorption dosage and recyclability are investigated. The results show that the maximum adsorption capacities of lead and cadmium ions on the hydrogel are 628.93 and 456.62 mg g^?1, respectively. The adsorption is well described by Langmuir isotherm model. The hydrogel is also utilized for the loading of potassium nitrate as an active agrochemical agent and the release of this active agent has also been investigated.     

Structure of a biologically active binuclear palladium complex in the compound (bis[(μ<Subscript>2</Subscript>-2-chloroethylammonium)(1,10-phenanthroline)-palladium(I)]) · tetranitrates · hydrate

The structure of a biologically active palladium complex [(1,10-phenanthroline)Pd(μ₂-2-chloroethylammoniu)] ₂ ⁴⁺ · 4NO ₃ ^? · H₂O has been determined from the diffractometric data. The compound crystallizes in the triclinic crystal system, space group of symmetry P \(\bar 1\), with the unit cell parameters a = 12.8352(8) Å, b = 14.4040(8) Å, c = 12.1668(9) Å, α = 116.16(1)°, β = 115.72(1)°, γ = 91.09(1)°, V = 1756.3 ų, Z = 2, and ρ = 1.892 g/cm³. The final reliability factor is R ₁ = 0.0351 for 7357 nonequivalent reflections with I ≥ 2σ(I), wR ₂ = 0.0970, and S = 1.044. The asymmetric part of the unit cell contains one positively charged binuclear palladium complex, four NO ₃ ^?1 anions, and one water molecule. The nanocomplexes are involved in the stacking π-π interaction by pairs: each complex forms a stacking with only one adjacent complex. The interaction between layers and inside each layer occurs through the van der Waals interactions and a three-dimensional system of hydrogen bonds, which are formed by the N ₃ ⁺ groups and water molecules.     

Production of high-carbon ferrochrome from dry-quenched semicoke

The quenching of semicoke by saturated steam (heating-gas temperature 550°C) is described. The working-moisture content W^r in the semicoke is 3.0–6.7% for the new quenching method. As a reducing agent, semicoke has good characteristics: relatively low ash content (A^d = 7.1%), low sulfur content (S^d = 0.13%) and phosphorus content (P^d = 0.029%), and high reactivity (\({K_{C{O_2}}}\) = 4.0 cm³/g s) and electrical resistivity (ρ > 1.9 × 10⁶ Ω cm). In tests, dry-quenched semicoke performs well in the production of high-carbon ferrochrome: decreased power consumption; increased furnace productivity; decreased consumption of chromium ore; and decreased sulfur content in the ferrochrome when Karaganda coal is completely reduced by the semicoke. The optimal semicoke content in the batch is up to 50 kg.     

Head-to-tail cyclization of a heptapeptide eliminates its cytotoxicity and significantly increases its inhibition effect on amyloid <Emphasis Type="Italic">β</Emphasis>-protein fibrillation and cytotoxicity

Amyloid-β (Aβ) protein aggregation is the main hallmark of Alzheimer’s disease (AD). Inhibition of Aβ fibrillation is thus a promising therapeutic approach to the prevention and treatment of AD. Recently, we designed a heptapeptide inhibitor, LVFFARK (LK7). LK7 shows a promising inhibitory capability on Aβ fibrillation, but is prone to self-assembling and displays high cytotoxicity, which would hinder its practical application. Herein, we modified LK7 by a head-to-tail cyclization and obtained a cyclic LK7 (cLK7). cLK7 exhibits a different self-assembly behavior from LK7, and has higher stability against proteolysis than LK7 and little cytotoxicity to SHSY5Y cells. Thermodynamic analysis revealed that both LK7 and cLK7 could bind to Aβ₄₀ by electrostatic interactions, hydrogen bonding and hydrophobic interactions, but the binding affinity of cLK7 for Aβ₄₀ (K_D = 4.96 μmol/L) is six times higher than that of LK7 (K_D = 32.2 μmol/L). The strong binding enables cLK7 to stabilize the secondary structure of Aβ₄₀ and potently inhibit its nucleation, fibrillation and cytotoxicity at extensive concentration range, whereas LK7 could only moderately inhibit Aβ40 fibrillation and cytotoxicity at low concentrations. The findings indicate that the peptide cyclization is a promising approach to enhance the performance of peptide-based amyloid inhibitors.

Open image in new window

     

Predicting the classification characteristics of coal. Part 2. Maximum moisture content

Analysis of 63 samples of coal concentrates (from Ukraine, Russia, the United States, Canada, Australia, and Poland) currently employed at Ukrainian coke plants indicates that the prediction of the maximum moisture content of coal may expediently be based on R _o and Q _s ^daf , determined, respectively, in plant laboratories and in power-station laboratories. The maximum moisture content of metamorphically distinct coals does not depend on their ash content (in the range 3.7–35.3%) nor on the chemical composition of the ash, expressed by the basicity index B _b (in the range 1.24–27.18) and the base/acid ratio I _b (in the range 0.198–1.832). Although the oxidation of coal also increases the maximum moisture content, this change is less than the error in its determination (0.5%). The oxidation of practically 30% of the coal’s organic mass increases the maximum moisture content by no more than 0.4%     

Ultrasonic velocity measurements in isobutyric acid - water binary mixtures over the temperature range from 300.15 to 313.15 K

We measured the ultrasonic velocity, U, density, ρ, and viscosity, η in Isobutyric acid - water binary liquid mixtures over the entire composition range at temperatures ranging from 300.15 to 313.15 K under atmospheric pressure. The experimental data values were analyzed to determine, various acoustical parameters: adiabatic compressibility, β, acoustic impedance, Z, free length, L_f, free volume, V_f, molar volume, V_m, relaxation time, τ, absorption coefficient, α/f², internal pressure, π_i, Gibb’s free energy, ΔG, cohesive energy, CE, Wada’s constant, W, Rao’s constant, R_m and relative association, R_A. The variation of these parameters versus the mixture composition was explained on the basis of the intermolecular interactions between the components of the mixture.