Optimization of raw hide curing using two-component counter-current diffusion model

Ošetření koncentrovaným roztokem solanky (chlorid sodný) je běžná metoda konzervace surových kůží. Sodné a chloridové ionty difundují ve směru do vnitřního objemu kůže, což iniciuje protiproudý transport vody směrem k povrchu. Výsledkem dvousložkové protiproudé difúze je rostoucí koncentrace soli a klesající obsah vody ve vnitřním objemu solené kůže. Pro optimalizaci konzervačního procesu je nezbytné zjistit časovou závislost koncentrace solanky směrem od povrchu do vnitřního objemu, to znamená nestacionární koncentrační pole ve vnitřním objemu konzervované kůže. Pro tyto účely byl navržen matematicko-fyzikální model difúze NaCl v kůži. Bylo provedeno numerické řešení tohoto modelu ? toto řešení zahrnuje koncentrační pole chloridu sodného a vody během konzervačního procesu. Byly experimentálně stanoveny příslušné efektivní difúzní koeficienty a jejich závislost na koncentraci soli. Výsledkem matematické simulace a matematického zhodnocení experimentálních dat byl odhad optimálního času pro solení v daných okrajových podmínkách, a dostatečné koncentrace soli ve vnitřním objemu solené kůže.Curing with concentrated brine solution (sodium chloride) is a common method for raw hide preservation. Sodium and chloride ions diffuse towards the raw hide inner volume, which initiates the counter-current transport of water from the raw hide inner volume. The result of the two-component counter-current diffusion is increasing salt content and decreasing water content in the raw hide inner volume. For optimization of the curing process it is necessary to determine the time dependence of the brine concentration from the hide surface towards its center, it means the non-stationary concentration field in the inner volume of the hide. For this reason we have proposed a mathematical-physical model for NaCl diffusion in the hide. We have also carried out the numerical solution of the modelthe solution comprises the concentration fields of sodium chloride and water during the curing process. The respective effective diffusion coefficients and their dependence on brine concentration have been determined experimentally. The result of the mathematical simulation and mathematical evaluation of the experimental data was estimation of the optimal time for raw hide curing at the given boundary conditions, and a sufficient brine concentration in the inner volume of the hide

Investigation into mechanical, surface and adhesive properties of date palm wood-polyolefin micro composites

Wood-plastic composites are composite materials made of wood fibre or other lignocellulosic materials and thermoplastic(s). Date palms are one of the potential replacements of insufficient timber sources in the Middle East and the Horn of Africa countries. Low density polyethylene (LDPE) was blended with date palm wood (DPW) (Phoenix dactylifera) powder to prepare composites with the concentrations of filler ranging from 10 to 70 wt. %. The Young´s modulus of the composites significantly increased with an increase in the filler content in the entire concentration range. The maximum value of 1933 MPa for the composite filled with 70 wt.% of the filler is approximately 13 times higher than that for the neat LDPE. The incorporation of DPW into the LDPE matrix led to a significant increase in the polarity of composites and to an increase in their adhesion to polar substrates.This contribution was supported by Ministry of Education of the Slovak Republic and Slovak Academy of Sciences, project VEGA, Grant No. 1/0570/17. This research was supported by the Slovak Research and Development Agency under the contracts No. APVV-16-0177, APVV-17-0583 and APVV-18-0378.Scopu

Investigation of Magnetic Anisotropy and Barkhausen Noise Asymmetry Resulting from Uniaxial Plastic Deformation of Steel S235

This study investigates alterations in magnetic anisotropy and the marked asymmetry in Barkhausen noise (MBN) signals after the uniaxial plastic straining of steel S235 obtained from a shipyard and used as standard structural steel in shipbuilding. It was found that the initial easy axis of magnetisation in the direction of previous rolling, and also in the direction of loading, becomes the hard axis of magnetisation as soon as the plastic strain attains the critical threshold. This behaviour is due to the preferential matrix orientation and the corresponding realignment of the magneto-crystalline anisotropy. Apart from the angular dependence of MBN, the asymmetry in the consecutive MBN bursts at the lower plastic strains is also analysed and explained as a result of magnetic coupling between the grains plastically strained and those unaffected by the tensile test. It was found that, by increasing the degree of plastic strain, the marked asymmetry in MBN tends to vanish. Moreover, the asymmetry in MBN bursts occurs in the direction of uniaxial tension and disappears in the perpendicular direction. Besides the MBN technique, XRD and EBSD techniques were also employed in order to provide a deeper insight into the investigated aspects

Antibacterial polyvinylchloride pre-treated by barrier plasma

A multistep physicochemical approach making use of plasma technology combined with wet chemistry has fueled considerable interest in delivery of surface-active antiadherence materials. In the first step of the approach, concerning an inherent lack of befitting functional groups on pristine substrate, plasma treatment at low temperature and atmospheric pressure has been substantiated to be productive in yielding reactive entities on the surface [1, 5]. The highlights the functionality of the adopted multistep physicochemical approach to bind polysaccharide species onto the medical-grade PVC surface. DCSBD plasma is capable of raising roughness, surface free energy, and introducing oxygen-containing functionalities anchored onto the surface. A structured poly(acrylic acid) brush of high graft density is synthesized using surface-initiated approach to further improve hydrophilicity and develop a stable brush-like assembly to yield a platform for biomolecular binding. In vitro bacterial adhesion and biofilm formation assays indicate incapability of single chitosan layer in hindering the adhesion of Staphylococcus aureus bacterial strain. Chitosan could retard Escherichia coli adhesion and plasma treated and graft copolymerized samples are found effective to diminish the adherence degree of Escherichia Coli. © 2014 by Nova Science Publishers, Inc. All rights reserved

Autochthonous microbiota in arsenic-bearing technosols from Zemianske Kostolany (Slovakia) and its potential for bioleaching and biovolatilization of arsenic

Studied technosols represent a unique system of a 50-year-old environmental burden after dam failure of coal-ash pond. The released ashes rich in arsenic with a thickness of 1–2 m were covered by a 40-cm thick layer of soil. Long-term exposure and selection pressure of elevated concentrations of arsenic (a range of 93–634 μg/g) induced the formation of the specific adapted autochthonous microorganisms. The phylum Proteobacteria was identified as a dominant phylum in the soils and represented only by one class—Gammaproteobacteria with six species. The species of phylum Firmicutes, Bacteroidetes and Actinobacteria were also identified. Thirty-three species of identified autochthonous microscopic fungi belong to 18 genera with the most abundant Mortierella alpina (Zygomycota). The most frequent identified mycobiota belongs to genera Penicillium, Aspergillus, Trichoderma and Alternaria. The isolates of Alternaria triticina, Bionectria ochroleuca, Chrysosporium queenslandicum, Exophiala psychrophila, Metarhizium robertsii, Trichoderma rossicum and Phlebia acerina were identified for the first time in Slovakia. Despite the stimulation of autochthonous community by nutrient medium and augmentation by native species, As leachability was relatively low—on average 5.63 wt.%, 9.23 wt.% and 17.04 wt.% of the total As for inoculated Pseudomonas chlororaphis ZK-1, Pseudomonas putida ZK-5 and Aspergillus niger, respectively. The highest As leachability was achieved through biostimulation of autochthonous microbiota using liquid SAB medium (34.73 wt.% of total As content). Additionally, microbial activity was efficient in the biovolatilization of As from soils (∼70 wt.% of the total As volatilized). It appears that bioremediation using microorganisms represents one of the possible ways of As removal from soils containing coal-combustion ashes with elevated concentrations of As.Web of Science2279art. no. 33

Mineralogy of neutral mine drainage in the tailings of siderite-Cu ores in Eastern Slovakia

This work presents the results of investigation of the primary minerals and their weathering products of two tailing ponds near the villages of Rudňany and Slovinky in eastern Slovakia. The tailings are near-neutral or slightly alkaline (pH = 7.2–8.8) because the acidity generated by the decomposition of the sulfides is efficiently neutralized by the abundant carbonate minerals. The most frequent primary gangue minerals are siderite, quartz, barite, and muscovite. The prevailing primary sulfide minerals in both tailing ponds are pyrite and chalcopyrite; less common are tetrahedrite and arsenopyrite. The most frequent secondary and tertiary (i.e., formed in the tailings, not in the oxidation zone of the deposits) minerals at both localities are iron oxides, either goethite or poorly crystalline hydrous ferric oxide. Other minerals (cuprite, malachite, delafossite; identified by X-ray microdiffraction or Raman spectroscopy) are minor or rare and occur only in Slovinky. The iron oxide minerals are enriched in a suite of elements, including Cu, Si, Ca, Zn, As, Mg, and Mn. The transformations of the poorly crystalline hydrous ferric oxide to goethite and maturation of goethite is controlled by both high-valence tetrahedral cations (Si, As, P) and lower-valence octahedral cations (Cu), as shown by the measurements of the size of coherently diffracting domains in goethite and the chemical composition of goethite. The iron oxide minerals, by virtue of their adsorption capacity, prevent separate minerals of many metals and metalloids (Cu, Ca, As, Sb) from nucleating and growing, and therefore control the entire neutral mine drainage (NMD) system. Geochemical modeling of the discharged waters shows that all common Cu and ferric arsenate minerals are strongly undersaturated, confirming the central role of iron oxide phases in the NMD system.Web of Science52579877

Innovative in situ remediation of mine waters using a layered double hydroxide-biochar composite

International audienceThe current demand for alternative water sources requires the incorporation of low-cost composites in remediation technologies; these represent a sustainable alternative to more expensive, commercially used adsorbents. The main objective of this comprehensive field-scale study was to incorporate the layered double hydroxides (LDHs) into the hybrid biochar-based composites and apply an innovative material to remediate As/Sb-rich mine waters. The presence of hydrous Fe oxides (HFOs) within the composite enhanced the total adsorption efficiency of the composite for As(V) and Sb(V). The kinetic data fitted to a pseudo-second order model. Equilibrium experiments confirmed that the composite had a stronger interaction with As(V) than with Sb(V). The efficient removal of As(V) from mine water was achieved in both batch and continuous flow column systems, reaching up to 98% and 80%, respectively. Sb(V) showed different behavior to As(V) during mine water treatment, reaching adsorption efficiencies of up to 39% and 26% in batch and column experiments, respectively. The migration of Sb(V) in mine water was mostly attributed to its dispersion before it was able to show affinity to the composite. In general, the proposed column technology is suitable for the field remediation of small volumes of contaminated water, and thus has significant commercial potential