Extraction of Alumina from Local Clays by Hydrochloric Acid Process@@@إنتاج الألومينا من الطفلة الوطنية بالمعالجة بحامض الأيدروكلوريك
A bench work study was carried out to investigate the use of kaolinitic clay containing 29.4% Al2O3 extremely abundant in Saudi Arabia for the production of pure alumina by calcination at 700 o C for 1h (recommended by previous investigators) then leached by hydrochloric acid. The effects of leaching temperature (25 o C to boiling temperature), period of activation (10-150 minutes), acid concentration (1M – 6M), particle size (–8 to –200 standard Tyler screen mesh), acid to clay weight ratio (4:1 to 15 : 1ml acid/gm clay) on alumina extraction were investigated. The recommended leaching conditions are: 6 molar for acid concentration at boiling conditions under reflux, one hour for leaching time, –100 mesh standard Tyler screens for particle size of calcined clay and 10 ml acid/gm clay for acid to clay weight ratio. Leaching this local clay sample under these conditions resulted in 32% alumina extraction. Local kaolinitic clay were calcined at temperatures varying between 400 o C and 800 o C at different calcination periods (5 to 120 minutes). The calcined clay was then leached with 3M HCl acid under the above-recommended leaching conditions. The optimum calcination conditions were 600 o C and 1 hour for calcination temperature and time period, respectively. The corresponding alumina extraction from local clay sample is about 63%.
EXTRACTION OF ALUMINA FROM IRAQI COLORED KAOLIN BY LIME-SINTER PROCESS
In this work lime -sinter method was investigated to recover alumina from Iraqi colored kaolinitic claystone. The claystone was intimately mixed with limestone and the mixture was sintered. The annealed sintered material dusts to a fine powder which required no grinding. This material was leached with sodium carbonate solution, and an alumina extract (sodium aluminate solution) was obtained. By bubbling carbon dioxide gas into this extract solution, gibbsite [Al(OH)3] precipitated and on calcinations at 1350 °C ,alumina in the form of alpha  (α – Al2O3) of high purity (98%) can be obtained. In the course of this investigation, the effect of sintering temperature and time, concentration of sodium carbonate solution, leaching time and sintered powder to sodium carbonate solution ratio were studied. About 85% of the alumina in the claystone was extracted at the optimum conditions. The alumina obtained in this method assaying 98% Al2O3, 1.45% SiO2, 0.04% Fe2O3, and 0.13% CaO and, 0.15% Na2O.
Refractory aspects of Egyptian alum-waste material
Abstract The material studied was Egyptian alum-waste, which consists mainly of SiO 2 and Al 2 O 3 . Mixes were made with appropriate additions of magnesia to bind SiO 2 as forsterite (2MgO·SiO 2 ) and Al 2 O 3 as spinel (MgO·Al 2 O 3 ), in an attempt to asses their suitability as a refractory forsterite material. The formation of spinel in these materials helped in the improvement of the quality of the prepared forsterite bodies. The phase reactions that may occur during the firing at 1550 °C of the prepared mixes, which belong to the five component system CaO–MgO–SiO 2 –R 2 O 3 were investigated. The mineral composition of the resulting forsterite bodies were determined theoretically by calculations from their thermal equilibrium data and experimentally by means of X-ray analysis and scanning electron microscopy. The technological properties of the resulting refractory bodies were determined and correlated with their mineral composition. Such properties were found to compare favourably with those of the parallel imported types.