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%.
Ten-cycle bench-scale study of simplified clay-hydrogen chloride process for alumina production
From abstract: This U.S. Bureau of Mines (USBM) research simplified an earlier hydrogen chloride (HCl) leachsparge process developed by the USBM to recover reduction-grade alumina from domestic kaolin clay. Improvements were made by decreasing the initial leaching acid concentration from 25 to 20 pct, decreasing the leaching time from 1 to 2 h to 15 to 30 min, eliminating the solvent extraction step for Fe removal, and eliminating the step to recover the Al content of the bleedstream circuit. A 10-cycle 
bench-scale experiment of the simplified process showed that the ferric chloride (FeC 3) concentration built up to 9.3 g/L in the recycle stream. This did not interfere with any of the unit operations or final alumina product purity because Fe forms stable soluble chloride complexes when sparged with HC and is easily washed from the large aluminum chloride hexahydrate (ACH) crystals. The reduced leaching time and acid concentration did not decrease Al extraction.
Extracting iron from aluminum sulfate solution
Abstract A solvent extraction process using Primene JMT (Rohm & Haas Company) as the extractant was investigated in this study in order to remove iron(III) (3–4 g/L) from an aluminum sulfate solution. The iron-loaded amine solution was regenerated by first stripping with 3.0 M NaOH solution, followed by neutralization with 1.5 M H 2 SO 4 solution. To improved its extractability of iron, the amine solution was contacted again with a weak NaOH (0.275 M solution to adjust its pH value to between 6 and 7. A subsequent continuous experiment showed that the iron(III) concentration in the acid solution can be decreased from 3.18 to 0.0124 g/L, i.e. a 99.6% reduction, in a four stage counter-current extraction operation using the proposed regeneration procedure.