Recently, several researches on red mud have been made from the point of view of recycling. It is one of the effective uses of red mud to recover such various elements as zirconium and titanium contained and to synthesize zeolites from the supernatant solution. In this study, the leaching of valuable components from red mud was in-vestigated using sulfuric acid as a function of leaching time, acid concentrations, and leaching temperatures. The results obtained are as follows; (1) The extraction of Na, Al, and Si amounts in equilibrium to 100, 70, and 65 percentages after ten minutes since the sodalite in red mud is very leachable. (2) Leaching of Fe and Ti in red mud is much affected by leaching temperatures, whereas leaching of Ca is little affected by leaching conditions. The extraction of Ca amounts to 20 percentages. (3) The leaching residue leached at 60°C for 64 hours using 1.8 mol/l of sulfuric acid contains TiO₂ 33.32 and ZrO₂ 2.45 percentages. TiO₂ and ZrO₂ in it are concentrated as compared with the original red mud. (4) The rate of process will be controlled by the surface reaction in the leaching process of Fe, Al, Ti, and Ca using sulfuric acid.

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It is very interesting to estimate the behavior of the multistage countercurrent extraction operation under various conditions, such as extraction or stripping stages and phase ratios by a digital computer. A simulation for the continuous multistage countercurrent extraction process of MgCl₂ from sea water has been carried out by using the batch extraction and stripping data. Extraction and stripping isotherms are represented as a simple mathematical function, which is incorporated into a computer program.
The simulation by expressing extraction and stripping isotherms as a mathematical function and taking the function in a computer program is considered to be an excellent method to estimate the extraction and stripping behavior in each stage in a steady state. It is recognized that the mixed ionic extractant comprising of Priment JMT and Versatic Acid 911 is superior to that of Aliquat 336 and Versatic Acid 911 in the recovery of MgCl₂ from sea water. Three stage extraction with the phase ratio (O/A) of 5 and 8 stage stripping with the phase ratio (O/A) of 20 can give 95% recovery of MgCl₂ and 3 times concentration in the use of a Priment JMT-Versatic Acid 911 system.

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