Slavomír Hredzák

Removal of cadmium, zinc, copper and lead by red mud, an iron oxides containing hydrometallurgical waste

Abstract Red mud, a residue of the alumina production industry which is actually a solid waste, has been studied as a potential sorbent for the removal of toxic bivalent cations (i.e. Cd, Zn, Cu and Pb) from aqueous solutions in the presence of 0.01 M NaNO3. The experimental data were modeled with Langmuir and Freundlich isotherms and fitted quite well. The relatively high uptake indicated that red mud can adsorb considerable amounts of cadmium and zinc from near-neutral aqueous solutions (maximum uptake capacity for cadmium: 68 mg-g1 at pH 6 and ca. 133 mg-g1 for zinc at pH 7). A significant uptake was also observed for copper and lead at pH 6 and 7 respectively which was attributed to precipitation of the respective insoluble hydroxides. TCLP leaching tests before and after the metal removal have shown that read mud is an environmentally compatible material that could be used for the wastewater treatment. Regeneration possibilities have also been observed.

Utilization of Ferromagnetic Fluids in Mineral Processing and Water Treatment

The paper is devoted to the utilization of ferrofluid as a separating medium and modifying agent affecting the magnetic properties of solid and liquid materials. The separation tests in a MHS separator have been carried out under laboratory condition. The selectivity of ferrofluids adsorption to the surface of some materials can be used for enhancing the magnetic susceptibility and influencing the efficiency of separation process. The enhancement of magnetic susceptibility of oil products up to a level sufficient for their magnetic extraction from water is possible by admixing of a definite amount of kerosene-based ferrofluid, which is non-miscible with water. The results point to the fact that the MHS method is suitable for the separation of non-magnetic materials according to their density and the modification of magnetic properties of materials by ferrofluid enhancing their magnetic separability.

Treatment of Red Mud From Alumina Production by High–Intensity Magnetic Separation

The paper gives attention to the possibilities of magnetic separation of red mud. The red mud can be characterised as an insoluble residue originated during the bayer method application in bauxite processing. Sample of red mud was obtained by leaching of bauxite from the Fria deposit (Guinea). The wet method of high–intensity magnetic separation was applied to the treatment. The magnetic product with the Fe content of 47% and recovery of 85% was obtained under magnetic field induction of 0.06 Tesla. The best results of magnetic separation were achieved by treating the size fraction–125 μm

Chemical, mineralogical and morphological characterisation of basic oxygen furnace dust

Abstract The occurrence and recovery of metallurgical wastes from steelmaking and ironmaking processes is nowadays a great problem, mainly because of their large amount and environmental pollution caused by heavy metals. Elements, such as Fe and Zn, which are important to the industries, are the main ones in basic oxygen furnace (BOF) dust. Because of their presence, it becomes very important to know how these elements are combined before studying new technologies for their processing. The aim of this work was to carry out chemical, physical, structural and morphological characterisation of the BOF dust. The investigation was carried out by using granulometric analysis, chemical analysis, SEM, EDAX, XRD and Mössbauer spectroscopy. These findings deepened our understanding of zinc speciation present in zinc-containing steelmaking wastes.

Application of Microwave Energy at Treatment of Asbestos Cement (Eternit)

Asbestos is the common name applied to a group of natural, fibrous silicate minerals, which were once one of the most popular raw materials to be used in building materials. Asbestos was mainly used for the production of assortment asbestos cement products. Today it is generally known that asbestos belongs to the group of hazardous materials and shows carcinogenic activity. It is therefore advisable to attempt to dispose of asbestos minerals in asbestos-containing materials and to convert them into a harmless material. One of methods may be microwave thermal decomposition of asbestos minerals. The research was used for old etemit roof ceiling. X-ray analysis indicated the presence of undesirable chrysotile. Its thermal destruction was carried out in a microwave oven in the power of 2500 W. In case the heating time was 15 min, X-ray analysis was confirmed chrysotile change into harmless minerals. Thermal analysis was used for characterization and the thermal behaviour of the asbestos cement sample.

Application of Fe-Nanoscale Materials Useful in the Removal of Arsenic from Waters

Two iron minerals (akaganeite and magnetite) were synthesized according to standard procedures and nanosized particles were obtained. The minerals were tested for their ability to remove As from water streams at pH value 3.5, with and without electrolyte (0.1 M conc.). Their capacities were calculated to 50 and 30 mg As/g of solid for akaganeite and magnetite, respectively. The sorption isotherms were modeled with Freundlich and Langmuir equations and good agreement was observed. Zeta potential studies have shown that both minerals sorbed As specifically, probably due to chemical forces between As oxyanions and surface Fe.

SYNTHESIS AND CHARACTERIZATION OF IRON NANOSTRUCTURES INSIDE POROUS ZEOLITES AND THEIR APPLICATIONS IN WATER TREATMENT TECHNOLOGIES

Abstract. A new sorbent with magnetic properties and anion removal ability has been produced by incorporating iron oxide based nanoparticles into the pores of zeolite crystals. The sorbent has been tested for the removal of arsenic (V) species from model aqueous solutions in batch–type equilibrium expe-riments. Good sorption was observed with maximum capacity of 73.32 mg of As per g of sorbent at pH 3.5. Keywords: arsenic; iron oxides; nanoparticles; magnetically modified zeolite; sorption Nanotechnology is developing fast, with much impact on a wide variety of technological areas. Inclusion of guests into a well-organized host matrix is a powerful method to form new nano-sized materials. Nanoporous and micropo-rous crystals, such as molecular sieves (zeolites) are ideal hosts for accommo-dation of organic and inorganic molecules, polymer chains, etc., because of their uniform pore size and their ability to adsorb molecular species. It is well known that zeolites possess a negatively charged surface and are therefore good sorbents of cations. The modification of their surface can create localized functional groups with a good affinity to inorganic anions too.

The Application of Heterogeneous PolarisableFluids in Mineral Processing

The paper deals with the application of ferrofluids in mineral processing. The efficiency of primary and secondary raw material separation by the magnetohydrostatic method is dependent on convenient distribution and on the stabilisation of density of the ferrofluid. To determine this density, the effective dynamometric method based on measurement of the buoyant force was constructed. A density controller has been developed for stabilisation and control of the density. Influence of some factors on the separation process, as well as the results of magnetohydrostatic separation are described.