Fast and Clean Synthesis of Nylon-6/Synthetic Saponite Nanocomposites

Nylon/saponite nanocomposites were synthesized and characterized. The nanocomposites were prepared by means of a fast, efficient, low cost, and environmentally friendly method. All of the tested preparations resulted in the pre-designed nanocomposites. To this end, delaminated saponites were directly synthesized to be used as a filler in a polymer matrix formed by nylon-6 by the in situ intercalation polymerisation of an ε-caprolactam monomer without the use of surfactants or other organic reagents to organophilise the clay, thus avoiding the drawbacks of contamination. The efficiency of the preparation method increased, and significant savings were achieved in terms of both energy reaction time, savings of 60% and 70%, respectively, by using microwave radiation as an energy source during the synthesis of the nanocomposites. In addition, given that the method that was followed avoids the use of contaminating organophilic agents, it is important to highlight the savings in reagents and the fact that there was zero environmental contamination.

Sulfint – the Czech gas desulfurization technology

The article describes one of the gas desulphurisation technologies which has been developed in the Czech Republic. The technology uses washing solution of organic complexes of various metals to remove H2S from gases. H2S removal is realized by its reaction with complexes of suitable metals with organic reagents. This leads to the H2S oxidation to elemental sulfur and the reduction of the metal protected by the organic complex to a lower oxidation state, which is also bound in the organic complex. Regeneration of the washing solution is performed by oxidation of the reduced form of the complex using oxygen from the air. Complexes of iron with ethylenediaminetetraacetic acid, nitrile triacetic acid or diethylenetriaminopentaacetic acid are used for the preparation of washing solutions. The reaction of the ferric complex of ethylenediaminetetraacetic acid with H2S is accompanied by a change in the color of the washing solution from a deep red color (like red wine) to a light brown color (like coffee with milk) of the ferrous complex of ethylenediaminetetraacetic acid. When this complex is completely depleted, it begins to decompose to black ferrous sulfide by further contact with H2S. This reaction is irreversible. The ferrous complex of ethylenediaminetetraacetic acid can be regenerated by reaction with oxygen, which also takes place at normal or elevated temperatures. The rate of this reaction is much slower compared to the reaction of H2S with the ferric complex. The process was discovered and intensively researched at the Institute for Fuel Research in Prague and later also at the University of Chemistry and Technology Prague. The first pilot plant tests took place with the desulfurization of coke oven gas at the Coking Plant Vítězný únor in Ostrava, where the first operating facility working with the given technology was later built. Another operating facility working with this technology was put into operation at the Antonín Zápotocký High pressure gasification plant in Ústí nad Labem and was used for desulphurization of expansion gases from pressure purification of waste gas of the Rectisol system. The technology was named Sulfint. Both facilities operated successfully until the end of operation of the town-gas supply system in the Czech Republic in the mid-1990s.

STUDY OF SORPTION OF RHENIUM IONS ON SOLID EXTRAGENTS

In this work, the aim is to study the possibility of extracting rhenium from sulfuric acid solutions by sorption of impregnated sorbents based on polystyrene-divinylbenzene (MN202) and an organic reagent MAB (2-amino-1-methylbenzimidazole).New sorbent based on MN202 (Purolite) impregnated with organic reagents have been obtained and investigated. The sorbent characteristics determined using SEM, XRD and FTIR methods. The optimal conditions for the sorption of rhenium (VII) ions for the "element-sorbent" systems have been established. Under static conditions, the sorption of rhenium on impregnated sorbents in a sulfuric acid solution was studied in the periodic system with respect to the contact time, sulfuric acid concentration, the ratio of the solid phase to liquid, and the initial concentration of rhenium. For the first time, the kinetics of sorption of rhenium (VII) ions with the obtained solid extractants has been studied. The kinetic parameters of the chemical reaction on the surface of the impregnate have been determined. Based on the processing of the integral kinetic curves of sorption, it was found that the sorption process proceeds in accordance with second-order models.

Lightweight, Flexible and Hydrophobic Cotton Fiber/Silica Aerogel Composite by Freeze-Drying for Organic Solvent/Water Separation and Thermal Insulation

Natural cotton fiber used for reinforcement is low-cost, environmentally friendly, good flexibility and easy to obtain. In this study, a new cotton fiber/silica aerogel composite was developed by sol–gel method via freezedrying. The obtained composite has excellent flexibility and can be restored to its original state after bending for 180° without obvious cracks. After 20 cycles continuous compression, the total unrecoverable strain loss is only 20% under strain of 60%. The composite also shows very prominent hydrophobicity, and the contact angle with water reaches 145 degrees. It has strong adsorption capacity for organic reagents and oil, with adsorption ratios of 500% and 600%, respectively. In addition, the composite has a low thermal conductivity of 0.038 W/(m·K) at room temperature. The obtained composite exhibits considerable promise in oil-water separation and thermal insulation.

Discovery of a Novel Antibacterial Protein CB6-C to Target Methicillin-Resistant Staphylococcus Aureus

Given the serious threat of multidrug-resistant bacterial pathogens to global healthcare, there is an urgent need to find effective antibacterial compounds to treat drug-resistant bacterial infections. In our previous studies, Bacillus velezensis CB6 with broad-spectrum antibacterial activity was obtained from the soil of Changbaishan, China. In this study, with MRSA as an indicator bacterium, an antibacterial protein was purified by ammonium sulfate precipitation, a Sephadex G-75 column, a QAE-Sephadex A 25 column and RP-HPLC, which demonstrated a molecular weight of 31405.48 Da by SDS-PAGE. LC-MS/MS analysis indicated that the compound was an antibacterial protein CB6-C, which had 88.5% homology with chitosanase Csn produced by Bacillus subtilis 168. An antibacterial protein CB6-C showed an effective antimicrobial activity against gram-positive bacteria (in particular, the MIC for MRSA was 16 μg/mL), low toxicity, thermostability, stability in different organic reagents and pH values, and an additive effect with conventionally used antibiotics. Mechanistic studies showed that an antibacterial protein CB6-C exerted anti-MRSA activity through destruction of lipoteichoic acid (LTA) on the cell wall. In addition, an antibacterial protein CB6-C was efficient in preventing MRSA infections in In Vivo models. In conclusion, this protein CB6-C is a newly discovered antibacterial protein and has the potential to become an effective antibacterial agent due to its high therapeutic index, safety, nontoxicity and great stability.

SORPTION OF BISMUTON (III) IONS FROM AQUEOUS SOLUTIONS BY SILICAS MODIFIED BY ORGANIC REAGENTS

In current paper, adsorbents based on silica L 40/100 modified with 4-(2-pyridylazo)resorcinol, 1-(2-pyrylazo)naphthol‑2, pyrocatechol violet and sodium N, N‑diethyldithiocarbamate were obtained. Adsorbents were modified by non-covalent immobilization of organic analytical reagents on the silica surface. It is noted that the preparation of such adsorbents is fast and easy to manufacture. The conditions of Bismuth (III) adsorption from dilute aqueous solutions by the proposed adsorbents are studied and optimized. The optimal values of the medium acidity for the effective Bismuth (III) preconcentration by the proposed adsorbents based on silica modified with organic analytical reagents have been established. It is shown that the use of modified silicas allows efficient (95–98%) removal of Bismuth (III) from dilute aqueous solutions. Under optimal adsorption conditions, the capacity of modified adsorbents is determined. It is established that the modification of silica leads to a significant (2–3 times) increase in the capacity of the obtained sorbents by Bismuth (III) in comparison with the unmodified silica, which is associated with the processes of complexation on the surface. The desorption of Bismuth (III) from the surface of unmodified and modified silicas by solutions of mineral acids has been studied. It is shown that Bi(III) is quantitatively desorbed from the surface of unmodified silicas by solutions of sulfuric and nitric acids, and in the case of modified silicas the degree of desorption is small and does not exceed 35%. The data obtained can then be used to develop a test system for determination of Bismuth (III) via corresponding colorimetric scales or for quantitative solid phase extraction and adsorption-spectroscopic quantification of Bismuth (III) in some real samples.

Understanding the effects of different residual lignin fractions in acid-pretreated bamboo residues on its enzymatic digestibility

Background During the dilute acid pretreatment process, the resulting pseudo-lignin and lignin droplets deposited on the surface of lignocellulose and inhibit the enzymatic digestibility of cellulose in lignocellulose. However, how these lignins interact with cellulase enzymes and then affect enzymatic hydrolysis is still unknown. In this work, different fractions of surface lignin (SL) obtained from dilute acid-pretreated bamboo residues (DAP-BR) were extracted by various organic reagents and the residual lignin in extracted DAP-BR was obtained by the milled wood lignin (MWL) method. All of the lignin fractions obtained from DAP-BR were used to investigate the mechanism for interaction between lignin and cellulase using surface plasmon resonance (SPR) technology to understand how they affect enzymatic hydrolysis Results The results showed that removing surface lignin significantly decreased the yield for enzymatic hydrolysis DAP-BR from 36.5% to 18.6%. The addition of MWL samples to Avicel inhibited its enzymatic hydrolysis, while different SL samples showed slight increases in enzymatic digestibility. Due to the higher molecular weight and hydrophobicity of MWL samples versus SL samples, a stronger affinity for MWL (KD = 6.8–24.7 nM) was found versus that of SL (KD = 39.4–52.6 nM) by SPR analysis. The affinity constants of all tested lignins exhibited good correlations (r > 0.6) with the effects on enzymatic digestibility of extracted DAP-BR and Avicel. Conclusions This work revealed that the surface lignin on DAP-BR is necessary for maintaining enzyme digestibility levels, and its removal has a negative impact on substrate digestibility.