Determination of the structural and mechanical properties of bauxite red mud of Ngaoundal as a precursor for ceramic production

Abstract

Globally, over 150 million tons of red mud are produced annually. Unfortunately, it is estimated that only about 2-4.5 tons are used annually in some way (Cement-500, 000 to 1,500,000 tons; Raw material/additive in iron and steel production-200,000-1,500,000 tons; Roads/landfill capping/soil amelioration-200,000-500,000 tons; Construction materials (bricks (tiles, ceramics, etc.) -100,000-300,000 tons; other (refractory, adsorbent, acid mine drainage, catalyst, etc.) -300,000 tons). This means over 145 million tons are being dumped in different parts of the world with the risk of causing another disaster like the Ajka, Hungary red mud spill that killed ten people, injured 200, and eliminated all aquatic life in a 71 km stretch. But because it contains compounds of Na, CA, Si and K, it can act as fluxing agent and so  could be of particular importance for use in the production of bricks, roofing tiles, rustic floor and wall tiles. This present research therefore investigated the characteristics of bauxite red mud from Ngaoundal in Cameroon for the manufacture of ceramic products. Such studies are vry canty in literature. Red mud was produced in laboratory by adapting the Bayer process. It was then characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA), Infra-Red (IR), particle size (PS) and Raman analyses (RA). Results of red mud analysis show that major oxides were Fe₂O₃ (37.21%), Al₂O₃ (19, 6 %), SiO₂ (7.68%), TiO₂ (1.07%), Na₂O (4.71%),and CaO (2.75%). The high amount of Na2O + K2O (4.77%) and CaO+ MgO (2.83%), oxides which  act as fluxes can easily facilitate the liquid phase formation during the firing stage of the ceramic. The XRD and Raman showed the presence oof hematite Fe₂O₃, calcite CaCO₃, gibbsite Al(OH)₃, anatase TiO₂; Quartz SiO₂ Diaspore AlOOH, Goethite FeOOH, which on heating decompose and  increase the quantity of metal oxides fluxes. Particle size analysis showed that 90% of particles in red mud have diameter below 90 microns, a good property for  homogenisation during ceramic production. Physical and mechanical properties of fired red mud (800, 900 and 1000^oC) such as: linear shrinkage, water absorption and apparent porosity; bulk Ddensity and  fexural strength were determined using ASTM-C326, ASTM-C373 and  ASTM-C 674 standards. Obtained results showed that all these properties increases with temperature. Results show that red can  effectively be used as a cheap precursor for ceramic materials production.