F. Andreola

The role of sodium hexametaphosphate in the dissolution process of kaolinite and kaolin

Suspensions of kaolinite and ceramic grade kaolin in sodium hexametaphosphate solutions at different concentrations were prepared and kept at constant temperature for 4 h: the solutions obtained after centrifugation and filtration were analysed using a ICP technique to determine the concentration of significant cations. The results allowed to stress the role of NaHMP in the dissolution process of kaolinite and ceramic grade kaolin. The role of accessory minerals in ceramic grade kaolin dissolution was discussed in the light of the obtained data.

Management of agricultural biomass wastes: preliminary study on characterization and valorisation in clay matrix bricks.

In this work the feasibility of using woody agricultural biomass wastes as grapes and cherries seeds, sawdust, as pore forming agent, and sugar cane ash, as silica precursor, in bricks, were reported. Sawdust and grapes and cherries seeds, thanks to their organic substances content, during their combustion, bring an energetic support in the bricks firing phase and act as pore forming agent. Usually the addition of this kind of waste is limited to 10wt.% in order to reach an equilibrium between positive (weight and shrinkage decrease and porosity increase) and negative (increase of water absorption and mechanical resistance decrease) effects. The results show that grapes and cherries seeds, added in a percentage of 5wt.% to a brick formulation, have better influence with respect to the sawdust, maintaining the mechanical properties of the fired brick (950°C), showing modulus of rupture around 21-23MPa with a weight reduction of 3-10% (respect to the standard one). Regarding the sugar cane ash, the addition of 5wt.% improves the mechanical properties (modulus of rupture around 27MPa) and no weight decrease is observed. These results confirmed the role played by this kind of agricultural waste, which thanks to its high silica content (61wt.%) is capable to demonstrate a filler and plasticity reducing effect on the brick bodies. Tests carried out highlighted that the addition of these by-products (5wt.%) do not change negatively the main technological properties measured (water absorption, linear shrinkage, flexural resistance, etc.) and permit to hypothesize their use to obtain bricks with both insulating and higher mechanical properties using a pore agent forming or silica carrier alternative raw materials, respectively.

Utilisation of municipal incinerator grate slag for manufacturing porcelainized stoneware tiles manufacturing

Porcelainized stoneware tiles containing up to 20 wt.% of municipal incinerator grate slag have been fabricated by cold uniaxial pressing and conventional fast firing cycles. The sinterability of these samples was investigated from density and shrinkage measurements together with mechanical (Vickers microhardness and Youngs modulus) and esthetical (spot resistance and colour parameters analysis) properties. The comparison with the porcelainized stoneware tiles containing no waste suggest a good compatibility between the ceramic body and the waste that does not significantly change the properties of the final products and the conditions of the firing cycle. Nevertheless, the porosity increase, proportional to the waste content, causes a decrease in density, shrinkage, spot resistance and whiteness.

Cathode ray tube glass recycling: an example of clean technology.

In this study the use of ‘cleaned’ end of life (EOL) cathode ray tube (CRT) glass as a raw material in ceramic glazes is described. At present, the recycling and industrial utilization of CRT, a glass material from TV and computer sets, is a subject of intense research with particular regard to the so-called open-loop recycling, namely cycles different from that of the origin. However, the use of CRT glass as a secondary raw material is strictly related to the demand of high-quality raw material. The good preliminary results reached by introducing clean TV and PC monitor panel and cone glass into ceramic glaze formulations pushed research toward the setting-up of a base glaze that is exploitable for the production of pigmented, silk-screened and flame-hardened glazes (products used industrially for coating floor tiles). The aesthetic and chemical characterization of the tiles glazed by this product showed an extremely similar behaviour to originals that did not contain CRT glass. The good technical results achieved have been supported by the life cycle assessment analysis, which has demonstrated a reduction of the environmental impact of the CRT glass-containing ceramic glaze with respect to the standard one.

Synthesis of chromium containing pigments from chromium galvanic sludges

In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium(III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to color ceramic material. Two different pigments pink CaCr(0.04)Sn(0.97)SiO(5) and green Ca(3)Cr(2)(SiO(4))(3) were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furthermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr(2)O(3). The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr-Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr(2)O(3).

The possibility to recycle solid residues of the municipal waste incineration into a ceramic tile body

The feasibility of utilising solid residues of the municipal wastes incineration such as grate (bottom) ash and electrofilter and sleeve filter fly ash, in combination with a porcelain stoneware body, in the preparation of tiles has been investigated. While the chemical, mineralogical, thermal and rheological characterisation of the waste raw materials carries out some problems arising by using fly ash, these seem to be overcome with the bottom ash. The introduction of up to 20 wt% of this powder into the ceramic body does not substantially change the mineralogical and thermal behaviour of the product.

Use of Incinerator Bottom Ash for Frit Production

Summary This article presents the results of an experimental activity aimed at investigating the technical feasibility and the environmental performance of using municipal solid waste incineration bottom ash to produce glass frit for ceramic glaze (glaze frit). The process includes an industrial pretreatment of bottom ash that renders the material suitable for use in glaze frit production and allows recovery of aluminum and iron. The environmental performance of this treatment option is assessed with the life cycle assessment (LCA) methodology. The goal of the LCA study is to assess and compare the environmental impacts of two scenarios of end of life of bottom ash from municipal solid waste incineration (MSWI): landfill disposal (conventional scenario) and bottom ash recovery for glaze frit production (innovative scenario). The main results of the laboratory tests, industrial simulations, and LCA study are presented and discussed, and the environmental advantages of recycling versus landfill disposal are highlighted.

New fired bricks based on municipal solid waste incinerator bottom ash

The main objective of this work was to study the sintering process and technological properties of new fired bricks based on high amount of post-treated municipal solid waste incinerator bottom ash and refractory clay. In addition, the effect of the minor addition of flux (Na2CO3) or reinforce (corundum) was also highlighted. Several methods were used to study the effect of compositions variations on the sintering process, structure and the mechanical characteristics of the test briquettes. Differential thermal analysis (TG/DTA) and dilatometry techniques were applied to study the thermal behaviour while scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and high-temperature X-ray diffraction were used to elucidate the structure and the phase composition. The mechanical characteristics were estimated by micro-indentation, strength and various physical tests (porosity, linear shrinkage and water absorption, etc). The results highlight the possibility to use very high amount of municipal solid waste incinerator bottom ashes in the production of new fired bricks with good performances at all levels. It is also shown that the addition of additives managed the final properties, affecting the crystal phase formation, porosity and greatly the strength of the samples.

Production of Cement Blocks and New Ceramic Materials with High Content of Glass Waste

Virgin raw materials can be partially replaced by glass waste in order to reduce the environmental impact being its recycling a significant problem for municipalities worldwide. In Italy in 2013, approximately 1,600,000 tons of container glass have been collected but it was not possible to recycle all of them in the glass melting process.This work is focused on the valorization of glass waste as raw material in new cement and ceramic products, to convert it from an environmental and economic burden to a profitable, added-value resource in the formulation of new mixes. Several parameters, such as grinding, forming, firing, etc. have been studied.It has been optimized the grinding and the reclaiming step of waste to obtain an alternative raw material for hot and cold consolidation processes. Chemical, physical and mechanical properties of products were carried out. The results show new real possibilities to use high amounts of glass waste as an alternative raw material in products consolidated either by hot or cold techniques, reducing the management problems of the glass waste.

Physical-chemical Characterization OfA Galvanic Sludge And Its InertizationBy Vitrification Using Container Glass

Several industrial processes produce large amounts of heavy metals-rich wastes, which could be considered as “trash-can raw materials”. The incorporation in ceramic systems can be regarded as a key process to permanently incorporate hazardous heavy metals in stable matrixes. In particular the aim of this work is to prepare and evaluate environmental risk assessment of coloured glass and glass-ceramic with the addition of chromium(III) galvanic sludge having a high content of Cr2O3 (15.91 wt%). Trivalent chromium compounds generally have low toxicity while hexavalent chromium is recognized by the International Agency for Research on Cancer and by the US Toxicology Program as a pulmonary carcinogen. The sludge has been characterized by ICP –AES chemical analysis, powder XRD diffraction, DTA, SEM, leaching test after different thermal treatments ranging from 400°C to 1200°C. Batch compositions were prepared by mixing this sludge with glass containers. The glass container composition is rich in SiO2 (69.89 wt%), Na2O (12.32 wt%) and CaO (11.03 wt%), while the sludge has a high amount of CaO (42.90 wt%) and Cr2O3 (15.91 wt%). The vitrification was carried out at 1450°C in an electrical melting furnace for 2 h followed by quenching in water or on graphite mould. Chromium incorporation mechanisms, vitrification processability, effect of initial Cr oxidation state, and product performance were investigated. In particular toxic characterization by leaching procedure and chemical durability studies of the glasses and glass-ceramics were used to evaluate the leaching of heavy metals (in particular of Cr). The results indicate that all the glasses obtained were inert and the heavy metals were immobilized.