Investigation of Waste Paper Cellulosic Fibers Utilization into Cement Based Building Materials

Recently, the utilization of renewable natural cellulosic materials, such as wood, plants, and waste paper in the preparation of building materials has attracted significant interest. This is due to their advantageous properties, low environmental impact and low cost. The objective of this paper is to investigate the influence of recycled cellulosic fibers (in the amount 0.5 wt % of the filler and binder weight) and superplasticizer (in the amount 0.5 wt % of the cement weight) on the resulting properties of cement composites (consistency of fresh mixture, density, thermal conductivity, and compressive and flexural strength) for hardening times of 1, 3, 7, 28, and 90 days. Plasticizer use improved the workability of fresh cement mixture. In comparison to the reference sample, the results revealed a decrease in density of 6.8% and in the thermal conductivity of composites with cellulosic fibers of 34%. The highest values of compressive (48.4 MPa) and flexural (up to 7 MPa) strength were achieved for hardened fiber cement specimens with plasticizer due to their significantly better dispersion of cement particles and improved bond strength between fibers and matrix

Monitorowanie zanieczyszczenia środowiska za pomocą cienkich elektrod metalowych przygotowanych przez fizyczne osadzanie z fazy gazowej

This work is focused on environmental pollution monitoring utilizing thin metal electrodes on glassy/ceramic substrates prepared by physical vapour deposition. Besides others, it is well known that environmental pollution on electrical insulation is one of the problems faced by distribution utilities and electricity transmission system. Due to this reason there is a need to deal with monitoring of environmental pollution as it strongly influences their capability to withstand the high-voltage stress without the breakdown. It is the aim of present work to propose new system for environmental pollution monitoring based on application of extra-thin metal electrodes. The influence of morphology and chemical composition of pollutants on the surface resistance and conductivity of selected insulators is also discussed.Artykuł dotyczy monitorowania zanieczyszczenia środowiska za pomocą cienkich elektrod metalowych na szklanych/ceramicznych podłożach przygotowanych przez fizyczne osadzanie z fazy gazowej. Widomym jest, że zanieczyszczenie środowiska odpadami izolacji elektrycznej jest jednym z problemów, przed którymi stoją firmy dystrybucyjne i system przesyłu energii elektrycznej. Z tego powodu istnieje potrzeba monitorowania zanieczyszczenia środowiska, ponieważ ma to duży wpływ niezawodność sieci wysokiego napięcia i jej awaryjność. Celem przedstawionych prac jest zaproponowanie nowego systemu monitorowania zanieczyszczenia środowiska w oparciu o zastosowanie bardzo cienkich elektrod metalowych. Omówiono także wpływ morfologii i składu chemicznego zanieczyszczeń na rezystancję powierzchniową i przewodnictwo wybranych izolatorów

Cement Materials Based on Cellulosic Fibers for Plasters

This paper presents physical and mechanical properties of cementitious composites/plasters containing cellulosic fibers in portion 2.0% and 5.0% of filler replacement after 28 days of hardening. Cellulosic fibers (Greencel) originated from bleached wood pulp and unbleached waste paper used in this experimental work were characterized from the point of view cellulose structure. Experimental investigations reveal that adding cellulosic fibers reduces composites density (up to 8.2 %) in comparison with composites without any fibers. Moreover, the presence of wood pulp and recycled fibers in composites cause higher values of water absorbability than sample without fibers. Also, the decrease in compressive strength values for tested fiber cement plasters was observed (14.1 - 18.0 MPa) in comparison to reference sample (26.6 MPa). But the identified compressive strength values are in accordance with European standard (5 MPa) for plasters

Rychlá hydrodehalogenace chlorovaných benzoových kyselin s použitím mechano-termicky připravené Raneyovy slitiny zahrnující rychlejší průběh hydrodehalogenačního procesu

The present study reports on the degradation of chlorinated benzoic acids (CBAs), commonly present in the environment as pollutants, by a hydrodehalogenation reaction utilizing the Raney Al-Ni alloy (50:50 wt% Al:Ni). The hydrodehalogenation reaction using the Raney Al-Ni alloy has already been proven as an efficient tool for fast and efficient degradation of halogenated persistent organic pollutants (POPs). Herein, the nano-structured Raney Al-Ni alloy was prepared by an alternative mechano-thermal approach starting from pure elements in a form of powders. The prepared alloy was characterized by X-ray diffractometry, scanning electron microscopy, particle size distribution, and active surface area analyses. The properties of the material were compared with a commercial sample of the same alloy prepared by the atomization process. The activity of the synthesized alloy was evaluated as removal efficiency and a rate of dehalogenation of three different CBAs - 2-chlorobenzoic acid, 2,6-dichlorobenzoic acid, and 2,3,6-trichlorobenzoic acid (trysben); used in the past as an herbicide. Dehalogenation of all three tested CBAs yielded benzoic acid as the only product and followed the first-order reaction kinetics. Compared to the commercially available alloy, enhanced kinetics of CBAs removal was achieved, owing to the solid-state properties of the mechano-thermally prepared alloy.Práce srovnává účinek komerční Al-Ni slitiny s materiálem připraveným mechanotermickou cestou z výchozích práškových kovů. Připravený materiál bych charakterizován s pomocí XRD, velikosti částic a specifického povrchu a otestován

Recovery of Chromium from Slags Leachates by Electrocoagulation and Solid Product Characterization

Slags produced in the steelmaking industry could be a source of chromium. Slags contain, depending on different types of slags, between 2 to 5 wt.% of Cr. Roasting of slag with NaOH, followed by subsequent leaching can produce leachates which can be efficiently processed using electrocoagulation (EC). This paper provides results from the EC process optimization for Cr(VI) solutions with initial concentration 1000 mg/L of Cr(VI). Influence of pH, current intensity and NaCl concentration on the efficiency of chromium recovery, energy consumption as well as solid product composition is discussed in detail. Optimum of pH = 6 was chosen for EC processing of Cr leachates as well as current intensities of 0.1–0.5 A because of the higher Cr/Fe ratio in solid product compared to higher current intensities. Results of EC processing of four real leachates of electric arc furnace carbon steel slag (EAFC), electric arc furnace stainless steel slag (EAFS), low carbon ferrochrome slag (LC FeCr) and high carbon ferrochrome slag (HC FeCr) were evaluated. Comparison of the results of four real leachate samples is presented. Obtained final solid product was identified as (Fe0.6 Cr0.4)2O3 and with up to 20% of Cr could be used as source of chromium in the ferrochrome production

Scalable synthesis of potential solar cell absorber Cu2SnS3 (CTS) from nanoprecursors

The present paper demonstrates an easy and scalable mechanochemical synthesis of ternary sulfide CuSnS (CTS) as a promising solar cell absorber. For the synthesis, pre-milled nanoparticles of CuS and SnS were used. The pure CTS phase was readily obtained after 60 min of milling in a laboratory planetary ball mill and 240 min in an industrial eccentric vibration industrial mill, respectively. The reaction progress of laboratory scale synthesis was studied by the quantitative Rietveld analysis. The reaction speed reaches its maximum at 4.6 min and the reaction is completed at approximately 60 min, according to the fitted data. The products of the syntheses were further characterized by X-ray powder diffractometry, Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–Vis spectroscopy. The results revealed formation of near-stoichiometric CTS nanoparticles with tetragonal I-42m symmetry. An average crystallites size of approximately 10–15 nm was determined for CTS phase. The SEM images support quintessential polydisperse character of the powders obtained by ball-milling approach. The materials seem to be suitable for photovoltaic applications with the band-gap energies of approximately 1.16–1.19 eV.This work was supported by the Slovak Research and Development Agency under the contract No. APVV-14-0103. The support of Slovak Grant Agency VEGA (projects 2/0044/18 and 2/0065/18) is also gratefully acknowledged

Vlastnosti sulfidu arsenitého (beta- As4S4) modifikovaného mechanickou aktivací

Arsenic sulphide beta-As4S4 has been modified by mechanical activation in a planetary ball mill. As a consequence, the solid-state properties and dissolution yield have been influenced. The following changes were observed: the increase of specific surface area, changes in the morphology (the formation of submicron particles), the occurrence of nanoparticles (21-31 nm), changes in crystal lattice parameters and changes in the Raman shift of particular vibrations. As a consequence of these changes, the dissolution rate of beta-As4S4 has been increased, which is a challenge for the application in cancer research.Sulfid arsenitý (beta-As4S4) byl modifikován mechanickou aktivací v planetárním kulovém mlýnu. Následkem tohoto procesu došlo k ovlivnění vlastností materiálu a jeho rozpouštěcího výtěžku. Byly pozorovány následující změny: nárůst specifického povrchu, změny morfologie (tvorba submikronových částic), přítomnost nanočástic (21-31 nm), změny parametrů krystalové mřížky a změny v Ramanovských posunech vibrací. Následkem těchto změn došlo k nárůstu rychlosti rozpouštění beta-As4S4, což je výzvou pro aplikace ve výzkumu rakoviny