Physicochemical, Mineralogical and Radiological Properties of Red Mud Samples as Secondary Raw Materials

The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)(3)) and they consists of particles of median particle size 2.1 mu m (sample A) and 2.5 mu m (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from U-238, Th-232, K-40 in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper

Recovery of critical and other raw materials from mining waste and landfills

The transition to a more circular economy is essential to develop a sustainable, low carbon, resource efficient, and competitive economy in the EU. In this context Critical Raw Materials (CRM) are defined as those which are of particularly great importance to the EU economy and at the same time there is a high risk of supply disruptions. First and foremost, improving the circular use of CRM is a key strategy in improving the security of supply and not surprisingly is an objective of various policy documents. This report delivers on action #39 of the Circular Economy Action Plan: "Sharing of best practice for the recovery of critical raw materials from mining waste and landfills". It builds on discussions held during two 2018 workshops and gathers together six examples of existing practices for the recovery of critical, precious, and other materials from extractive waste and landfills, highlighting technological innovation and contributions that have been made to a more comprehensive knowledge-base on raw materials. The report also provides various estimates of potential recovery of certain materials compared to their current demand. Lessons learnt from the practices include awareness that it is very unlikely that recovery processes can target one or just a few specific materials of great interest and disregard other elements or bulk matrixes. Especially in case of very low concentrations, most of the mineral resources and other bulk materials in which they are embedded must be valorised in order to increase economic viability and minimise waste disposal. As recovery processes can be very energy intensive, environmental and land use related aspects are also particularly relevant even though environmental gains may also occur and, moreover, land space can be liberated and reused for new purposes and services. Finally, availability of data and information on secondary materials as well as a harmonized legislative framework within the EU appear to be crucial for the large-scale deployment of recovery practices.JRC.D.3-Land Resource

Geopolymerisation behaviour of size fractioned fly ash

Fly ash is a fine powder residue resulted from combustion of pulverized coal in thermal power plants. Different size fractions of fly ash have different properties. Four size fractions (with characteristic particle diameter D-50 of 40.37, 23.64, 10.33 and 2.98 mu m respectively) collected from different fields of an electrostatic precipitator and representing the entire particle spectrum of fly ash has been selected for the study. These fractions have been characterized for their granulometry, chemistry, glass content and mineralogical phases. Geopolymerisation of size fractioned fly ash has been carried out at ambient (27 degrees C) and elevated (60 degrees C) temperature using isothermal conduction calorimetry (ICC) and the microstructure has been studied using X-ray diffractometry (XRD), scanning electron microscopy with X-ray microanalysis probe (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). Calorimetric studies showed that the heat flow curve during geopolymerisation has linear correlation with the glass content of fly ash. The compressive strength development at both ambient and elevated temperature was due to the combined effect of SiO2/Al2O3 ratio, particle size and glass content. SEM-EDS studies have shown more reaction product in finer fractions and unreacted particles in coarser fractions. Formation of more thermonatrite phase was due to poor reactivity of coarse size fraction resulting into free alkali which in presence of atmospheric carbon formed Na2CO3 center dot H2O. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

Influence of various mechanical preparation methods of LCD on the leachability of critical elements

As various electrical and electronic equipment pieces are frequently replaced due to technological development or changes, the recycling of the generating in huge amount e-wastes is of outstanding importance. The research in this field is inevitable in the spotlight of creating the circular economy. The recycling strategy is generally aiming at the recovery of materials like plastics and metals, as well as of valuable, even critical elements and compounds along with the satisfactory treatment of toxic ones. For this sake the mechanical treatment is combined with the chemical/bio/thermal techniques. Due to the numerous elements used for their manufacturing, LCD (Liquid Crystal Displays) display panels provide a wide range of valuable and critical, but also toxic elements. Thus, instead of disposal of waste LCD panels, the recovery of such elements can not only prevent possible environmental hazards but endorse the utilisation of secondary raw materials. It was proved that the mechanical pre-treatment is an important step, first of all, to recycle materials like plastics and common metals. Furthermore, the chemical mass transfer is governed by the concentration gradient, the area exposed and the retention time. Nevertheless, the presence of the “alien” components in the mass transfer can dramatically decrease the concentration gradient, the contact surface, as well as the diffusion rate. And finally, the lower the material flow to be submitted for the chemical processing, the lower the specific reagents requirement and, therefore the costs of the process (Bokányi, 2014). Thus, the mechanical removal of LCD polarizing film seems to be highly advisable; however is not easy, needs 200-250 °C high temperature as well. At the same time, the ITO (Indium-Tin-Oxide) surface layer at favourable conditions can be exposed for the diffusion even without removing polarizing foil. Therefore, one experimental series of our current research was focused on the comparison of acidic leaching of the stripped and ground LCD panel with and without the polarizing film. Another experimental series was devoted to the effect of fineness on the leachability of indium, tin and other elements. Thereafter, ground LCD was produced with different fineness in Retsch ZM 200 centrifugal mill. Based on the data obtained, important conclusions were draw

Control of geopolymer properties by grinding of land filled fly ash

This paper is focused on the investigation of a land filled Hungarian fly ash (Tiszaújváros dumpsite) as a main component of geopolymer. After determination of the fly ash properties such as particle size distribution, moisture content, real and bulk density and specific surface area, mechanical activation by fine grinding of the fly ash sample was performed in laboratory scale ball mill, vibratory mill and stirred media mill in order to improve its reactivity. Grinding kinetics was determined in each mill. The geopolymer cylindrical specimens were prepared and their uniaxial compressive strength was measured. The structure of the fly ash and the geopolymer was monitored by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD); furthermore, the morphology was examined using optical microscopy and Scanning Electron Microscopy (SEM). Finally, Isothermal Conduction Calorimetry (ICC) measurements were carried out in order to determine the reactivity of the mechanically activated fly ash samples. As a result of the investigation, the relationship between the grinding process, the ground material properties and the geopolymer characteristics was established. It was found that the strength of the specimen strongly depends on the grinding conditions, i.e. type of mill, residence time

Physicochemical, mineralogical and radiological properties of red mud samples as secondary raw materials

The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)3) and they consists of particles of median particle size 2.1 mm (sample A) and 2.5 mm (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from 238U, 232Th, 40K in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45012 and Grant no. III 45005