ABSTRACT
In the present work, the development of geopolymeric materials with Na or K based on industrial kaolin samples, with variable kaolinite content and alkaline silicates, is studied. XRF, XRD, FTIR and SEM-EDS have been used as characterization techniques. Three ceramic kaolin samples, two from Algeria and one from Charente (France), have been considered. In particular, chemical and mineralogical characterization revealed elements distinct of Si and Al, and the content of pure kaolinite and secondary minerals. Metakaolinite was obtained by grinding and sieving raw kaolin at 80 µm and then by thermal activation at 750 °C for 1 h. This metakaolinite has been used as a base raw material to obtain geopolymers, using for this purpose different formulations of alkaline silicates with NaOH or KOH and variable Si/K molar ratios. The formation of geopolymeric materials by hydroxylation and polycondensation characterized with different Si/Al molar ratios, depending on the original metakaolinite content, has been demonstrated. Sodium carbonates have been detected by XRD and FTIR, and confirmed by SEM-EDS, in two of these geopolymer materials being products of NaOH carbonation.
ABSTRACT
The aim of this study was to recycle dredged sediments as an alternative raw material in the production of ceramic tiles. The effect of the substitution of kaolin by raw sediment (HDS) and calcined sediment (HDSC) in the mixture of the ceramic tile samples sintered at 1100 and 1200 °C was studied. The samples were prepared with different proportions of HDS and HDSC (0, 10, 20 and 30 wt.%) substituting kaolin. The mineralogical analysis of the samples shows that mullite phase disappears in the samples incorporating raw sediments (HDS) and fired sediments (HDSC) leading to the formation of new crystalline phases such as anorthite and diopside.Moreover, ceramic tile samples with 20 wt.% of calcined sediment improve its densification and hence the compressive strength (171 MPa) and thermal conductivity (0.555 W/mK). An evaluation of the leaching was carried out in the ceramic samples, finding that the concentrations of heavy metals in the leachate were within the safety limit established by the USEPA. The heavy metals were immobilised in the ceramic matrix. Therefore, the results showed that dredged sediment (HDS) and calcined sediment (HDSC) could be used as substituent of kaolin to produce eco-friendly ceramic building materials as floor tile ceramics.
Subject(s)
Kaolin , Metals, Heavy , Ceramics/chemistry , Construction Materials , Kaolin/chemistry , RecyclingABSTRACT
The extraction of gold ore generates rejects called gold mining reject (GMR). This reject is considered a major environmental problem for the mining industry. In Amesmessa mine (Hoggar, Algeria), where mining have been carried out for over 15 years, about 2 million tons of mill tailings has been accumulated each year. The aim of this work is to study the reuse of GMR as raw material in ceramic field and its effect on microstructure, color, and mechanical and chemical properties. During investigation, the results show that GMR is mainly composed of quartz, hematite, pyrite, and dolomite. During sintering, mullite, quartz, anatase, and rutile were the mineralogical phases which composed the ceramic samples. As the temperature rises at 1200 °C, peaks of mullite increased, beside rutile and quartz phases. When 30 wt% of the reject was added, the crystalline phases as quartz and mullite diminished, giving rise to the glassy phase formation that is promoted by metal oxides playing a role as fluxing agents. Elastic property as Young's modulus of the samples increased from 09.35 to 15.93 GPa and from 19.66 to 60.94 GPa at 1100 °C and 1200 °C respectively. The environmental study of the incorporation of GMR in ceramic matrix, rich in heavy metals (Fe, Zn, Ni), was evaluated by leaching tests of the fired products. The results indicated a successful immobilization of the heavy metals. These results suggested the use of gold mining reject in the ceramic field, as a substituent of feldspar, and might be an alternative and reliable method for the disposal of this reject.
