Arc atomic emission analysis of the feedstock for production of metallurgical alumina

The analytical capabilities of the arc atomic emission analysis for determination the impurities in kaolin clays, the feedstock for producing metallurgical alumina, were studied. The analytical lines of the elements that are most free of interferences are selected. The conditions of the analysis and parameters of the spectrometer are determined: current strength, exposure, interelectrode distance, types and parameters of electrodes, weight of the sample. The detection limits and limits of determination of the following elements are specified: Ca, Cr, Cu, Ga, Mg, Mn, Mo, Nb, Ni, Pb, Sc, Ti, V, Y, Zn, Zr, La. The limits of determination are n x 10–5 – n x 10–6 wt.%. A comparative analysis of the samples of kaolin clays previously analyzed by another method in the framework of inter-method comparative tests is carried out. It is shown that there are no significant discrepancies between the results obtained by both two methods.

CHANGES IN ADHESION FORCES OF MONTMORILLONITE AND KAOLIN CLAYS AT STRESS PRESSURES

For the formation of the technological properties of clays, various methods of their processing have been developed: thermal, chemical, ultraviolet, mechanical, etc. However, the issues of changing the energy properties of the surface of clay particles, previously compacted by stress pressure, are not fully understood. Therefore, the aim of the work is to study the patterns of change in adhesion forces on the surface of particles of montmorillonite and kaolin clays treated with stress pressure up to 800 MPa and a shift of 90°. The adhesion forces of clay samples subjected to stress pressure and shear were studied using an NT-MDT NTEGRA Prima atomic force microscope (Russia). It was experimentally proved that during the machining of kaolin and montmorillonite clays by stress pressure and shear changes in adhesion forces are multidirectional in nature. In kaolin clay, as the pressure increases, the adhesion force increases. In montmorillonite, an increase in pressure up to 150 MPa leads to an increase in the adhesive interaction, a further increase to 800 MPa leads to its decrease. It was revealed that during the processing of clays by stress pressure and shear, the processes of crushing, aggregation and deformation of particles occur in them, leading to a change in the defectiveness of the crystal lattice and the surface of the particles. Such transformations create changes in the energy potential of clay particles, which in turn changes the sorption and adhesive properties of clays. At the same time, in the studied soils the formation of the energy potential on the surface of particles takes place in different ways: in kaolin clays, the main factor is the crushing process, and in montmorillonite — aggregation.

Study of Ceramic Membrane from Naturally Occurring-Kaolin Clays for Microfiltration Applications

The focus of this work is to assess the quality of porous membranes prepared from naturally occurring kaolin clays and to evaluate the performance of tubular ceramic membranes treating integrated raw effluents from seafood industry. This material has been chosen due to its natural abundance, its non-toxicity, low cost and its valuable properties. The preparation and characterization of porous tubular ceramic membranes, using kaolin powder with and without corn starch as poreforming agent, were reported. SEM photographs indicated that the membrane surface was homogeneous. The effects of material compositions, additives and the relatively lower sintering temperature, ranging from 1100° to 1250°C, on porosity, average pore size, pore-size distribution and mechanical strength of membranes have been investigated. A correlation between microstructure and mechanical properties of membranes has been discussed. The performance of the novel ceramic membranes thus obtained was determined by evaluating both the water permeability and rejection. The obtained membrane was used to treat cuttlefish effluents generated from the conditioning seawater product industry which consumes a great amount of water. Cross-flow microfiltration was performed then, in order to reduce the turbidity and chemical oxygen demand (COD).