Valentin Ivanovski

Efficient multistep arsenate removal onto magnetite modified fly ash

The modification of the fly ash (FA) by magnetite (M) was performed to obtain FAM adsorbent with improved adsorption efficiency for arsenate removal from water. The novel low cost adsorbents are characterized by liquid nitrogen porosimetry (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MB) and Fourier transform infrared (FTIR) spectroscopy. The optimal conditions and key factors influencing the adsorbent synthesis are assessed using the response surface method (RSM). The adsorption experiment was carried out in a batch system by varying the contact time, temperature, pH, and mass of the adsorbent. The adsorption capacity of the FAM adsorbent for As(V), calculated by Langmuir model, was 19.14 mg g-1. The thermodynamic parameters showed spontaneity of adsorption with low endothermic character. The kinetic data followed the pseudo-second-order kinetic model (PSO), and Weber-Morris model indicated intra-particle diffusion as rate limiting step. Alternative to low desorption capability of the FAM was found by five consecutive adsorption/magnetite precipitation processes which gave exhausted layered adsorbent with 65.78 mg g-1 capacity. This research also has shed light on the mechanism of As(V)-ion adsorption, presenting a promising solution for the valorization of a widely abundant industrial waste.

Study of Nanodimensional Spinel Ni 0.5 Zn 0.5 Fe 2 O 4 Ferrite Prepared by Mechanochemical Synthesis

The nanodimensional Ni0.5Zn0.5Fe2O4 ferrites were prepared from mixture of NiO/ZnO/α-Fe2O3 and Ni(OH)2/Zn(OH)2/Fe(OH)3 powders by (soft) mechanochemical synthesis after 5 and 10 h of milling time. The XRD of the sample obtained after 10 h milling time shows single phase cubic spinel structure. TEM analysis revealed that all samples are composed of more or less agglomerated nanosize particles. The average size of nano crystallites is ~20 nm. The degree of the cation inversion of NZF is estimated for spinel fraction in all samples by Rietveld analysis. In the Raman spectra are observed all of first-order active modes. In the spectra of the single phase “hydroxide” samples it is visible that the energy position and intensity of modes is dependent on the composition and cation distribution. It was shown that the modes in Raman spectra of nickel-zinc ferrite that originate from vibrating of different cations could be clearly distinguished. From the ratio of intensities of the A 1g-type Raman modes, it is possible to estimate the inversion of cations. The Mossbauer spectra were fitted by several subspectra and according to known subspectral areas of both iron sites the degree of inversion was calculated, also. The cation inversion is λ = 0.36(3) for ferrite sample obtained from the mixture of appropriate hydroxide for 10 h milling.

Mineral characterization of soil type ranker formed on serpentines occurring in southern Belgrade environs Bubanj Potok

The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission 57Fe Mossbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite) particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite) and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite), pyroxene (enstatite/ferrosilite, diopside/hedenbergite), and serpentine (antigorite/lizardite/chrysotile) were identified.

Mössbauer Spectroscopic Analysis of Nd2Fe14B/α-Fe Hard Magnetic Nanocomposites

Among novel magnetic intermetallics based on rare earth-transition compounds, the Nd2Fe14B/α-Fe isotropic nanocomposites have been obtained by recrystallization from an amorphous phase, prepared by melt spinning. For variable 5 wt.% Fe and 10 wt.% Fe contents we recorded transmission 57Fe Mössbauer spectra at the room temperature, hardened of the α-Fe phase by exchange interactions. The spectra have been analyzed in terms of ten Zeeman sextets and one paramagnetic doublet related to the Nd1.1Fe4B4 phase. One sextet corresponds to the α-Fe phase, whereas others are attributed to six non-equivalent Fe sites in the Nd2Fe14B structure, namely 16k1, 16k2, 8j1, 8j2, 4c, and 4e. The three remaining sextets belong to the Fe3B structure with three inequivalent Fe sites FeI(8g), FeII(8g) and FeIII(8g). All relevant parameters for both nanocomposites: the magnetic hyperfine field, the isomer shift and the quadrupole splitting are determined for each of these sites.