Jiří Másilko

The Characterization of Fixation of Ba, Pb, and Cu in Alkali-Activated Fly Ash/Blast Furnace Slag Matrix

The fixation of heavy metals (Ba, Cu, Pb) in an alkali-activated matrix was investigated. The matrix consisted of fly ash and blast furnace slag (BFS). The mixture of NaOH and Na-silicate was used as alkaline activator. Three analytical techniques were used to describe the fixation of heavy metals—X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD). All heavy metals formed insoluble salts after alkaline activation. Ba was fixed as BaSO4, and only this product was crystalline. EDS mapping showed that Ba was cumulated in some regions and formed clusters. Pb was present in the form of Pb(OH)2 and was dispersed throughout the matrix on the edges of BFS grains. Cu was fixed as Cu(OH)2 and also was cumulated in some regions and formed clusters. Cu was present in two different chemical states; apart from Cu(OH)2, a Cu–O bond was also identified.

Effect of Na3PO4 on the Hydration Process of Alkali-Activated Blast Furnace Slag

In recent years, the utilization of different non-traditional cements and composites has been increasing. Alkali-activated cementitious materials, especially those based on the alkali activation of blast furnace slag, have considerable potential for utilization in the building industry. However, alkali-slag cements exhibit very rapid setting times, which are too short in some circumstances, and these materials cannot be used for some applications. Therefore, it is necessary to find a suitable retarding admixture. It was shown that the sodium phosphate additive has a strong effect on the heat evolution during alkali activation and effectively retards the hydration reaction of alkali-activated blast furnace slag. The aim of the work is the suggestion of a reaction mechanism of retardation mainly based on Raman and X‑ray photoelectron spectroscopy.

Mechanisms of Macro-Pores Origin in the MDF Composites Fabrication

Paper deals with the description of the MDF composite microstructure and the possible emergence of macro-pores. MDF composites show enhanced mechanical properties, especially flexural strength. Where, the flexural strength can be associated with the elimination of critical cracks in the material. One of the steps of production of MDF composites is high-shear mixing, that just helps to achieve defect-free structure. The primary aim of this work is to specifically describe the origin of the macro-pores in the structure of MDF composites. The secondary one is to find appropriate setup for high-shear mixing equipment in order to eliminate main macro-pores (shear speed, distance between the rollers etc.).

Cement Kiln By-Pass Dust: An Effective Alkaline Activator for Pozzolanic Materials

Cement kiln by-pass dust (CKD) is a fine-grained by-product of Portland clinker manufacturing. Its chemical composition is not suitable for returning back into feedstock and, therefore, it has to be discharged. Such an increasing waste production contributes to the high environmental impact of the cement industry. A possible solution for the ecological processing of CKD is its incorporation into alkali-activated blast furnace slag binders. Thanks to high alkaline content, CKD serves as an effective accelerator for latent hydraulic substances which positively affect their mechanical properties. It was found out that CKD in combination with sodium carbonate creates sodium hydroxide in situ which together with sodium water glass content increases the dissolution of blast furnace slag particles and subsequently binder phase formation resulting in better flexural and compressive strength development compared to the sample without it. At the same time, the addition of CKD compensates the autogenous shrinkage of alkali-activated materials reducing the risk of material cracking. On the other hand, this type of inorganic admixture accelerates the hydration process causing rapid loss of workability.

Immobilization of Sr2+, Bi3+ and Zn2+ in Alkali-Activated Materials Based on Blast Furnace Slag and Fly Ash

It is well known, that alkali-activated materials (AAMs) are suitable for immobilization of heavy metals and other hazardous materials. This study is focused on the characterization of inhibition of three metals – Sr2+, Bi3+ and Zn2+ in alkali-activated matrices. Two type of matrices were prepared – alkali-activated blast furnace slag (BFS) and alkali-activated fly ash (FA). Sodium water glass was used as alkaline activator. The ability of these matrices to fix the metals were proved by leaching tests. Compressive strength was measured to characterize mechanical properties of the matrices. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to examine distribution and chemical state of metals within the matrices. The observed metals mainly formed the insoluble compounds after alkali activation.

Facile synthesis and rheological characterization of nanocomposite hyaluronan-organoclay hydrogels

We report a facile methodology for the synthesis of inorganic-organic hydrogels based on integrative assembly of aminopropyl magnesium phyllosilicate (aminoclay) and sodium salt of hyaluronic acid. The viscoelastic materials produced by electrostatic interactions and crosslinking of hyaluronan in the presence of exfoliated synthetic organoclay results in the formation of gel-like behavior retaining a high amount of water. This was confirmed by a rheological study revealing significant dominance of the elastic response over the entire deformation frequency range used. The mechanical strength of the aminoclay-hyaluronan hydrogels was found to be higher than that for related materials based on poly(vinylpyrrolidone)-aminoclay hydrogels.

Influence of Pb Dosage on Immobilization Characteristics of Different Types of Alkali-Activated Mixtures and Mortars

Alkali-activated matrices are suitable materials for the immobilization of hazardous materials such as heavy metals. This paper is focused on the comparison of immobilization characteristics of various inorganic composite materials based on blast furnace slag and on the influence of various dosages of the heavy metal Pb on the mechanical properties and fixation ability of prepared matrices. Blast furnace slag (BFS), fly ash, and standard sand were used as raw materials, and sodium water glass was used as an alkaline activator. Pb(NO3)2 served as a source of heavy metal and was added in various dosages in solid state or as aqueous solution. The immobilization characteristics were determined by leaching tests, and the content of Pb in the eluate was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). The microstructure of matrices and distribution of Pb within the matrix were determined by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Increasing the dosage of the heavy metal had negative impacts on the mechanical properties of prepared matrices. The leaching tests confirmed the ability of alkali-activated materials to immobilize heavy metals. With increasing addition of Pb, its content in eluates increased.

TiO2 Surface Coating of Mn-Zn Dopped Ferrites Study

This study deals with TiO2 coating of powder Mn-Zn ferrite in order to recieve photocatalytic layer on the top of these particles, forming core-shell catalyst. Powder catalysts are of great advance over the world due to the high surface area, considering the kinetics proceeds through heterogenous phase boundary catalysis. However their withdrawal from cleaning systems often requires energetically and economically demanding processes such as filtration and ultrafiltration. Since the ferrite is magnetic, the advantage of such formed core-shell photocatalyst is easibility of removing from photocatalytic decomposition system using external magnetic field. In this study the surface coating is performed, using Ti alkoxides mixtures with nanosized TiO2 particles and C and Au coating to form film layer of TiO2 on the surface of ferrite. XRD, SEM – EDS analyses are employed to study surface coating.

Application of Sol-Gel Method to Investigate the Influence of P2O5 on the Course of Reactions in CaO-SiO2 System

The effect of P2O5 addition on the calcium silicate phase equilibrium during the sol-gel synthesis of dicalcium silicate was investigated using Scanning electron microscope and X-ray diffraction. It is established that phosphorous oxide can form solid solution with dicalcium silicate, but its causes the formation of phosphatic calcium silicate phases such as Ca14.92 (PO4)2.35(SiO4)5.65 and 5CaO.SiO2.P2O5 also. Local analysis has demonstrated the presence of calcium phosphate epicenters containing silicon oxide and calcium silicate zones with minimum content of phosphorous oxide and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of calcium silicate and calcium phosphate is due to the affinity between acid oxides (SiO2, P2O5) and basic one (CaO) during sol-gel process. Then, the formation of various phosphatic calcium silicates result from the diffusion of P2O5 towards calcium silicate and that of SiO2 towards calcium phosphate.

Synthesis of Layered Calcium Cobaltites Intended for Thermolectric Application

Layered misfit cobaltites exhibit adequate combination of electrical and thermal properties under the high temperatures. Cobaltites are due to these properties and appropriate costs optimal candidates for thermoelectric industrial applications [1]. Calcium cobaltites were prepared via conventional and less conventional synthesizing methods. Wet citric and glycine/nitrate combustion syntheses were compared with conventional solid state reaction. Prepared powders were studied in terms of phase and chemical composition, morphology, size of particles/agglomerates and thermoelectric properties. Particle size of prepared powders was varied from nano to micro size with different level of agglomeration. The lowest values of particle size (~ 160 nm) with low agglomeration were obtained with the citric combustion method. The influence of the preparation method on the properties of final bulk product was evaluated within this work.