الفهرس 
LITERATURE SURVEYOnly 14 pages are availabe for public view
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Abstract
The present research studied the leaching of the serpentine rock with hydrochloric acid to obtain magnesium chloride hexahydrate crystals. After the reaction of serpentine, the slurry mixture was filtered and washed. The serpentinite mineral sample was obtained from the Fawakhir area (Wadi Attala, WAS) in Egypt’s Eastern Desert. The major mineral in the sample was antigorite [Mg3Si2O5(OH)4].
The serpentinite mineral is characterized by high contents of
MgO and SiO2 and relatively low contents of Fe2O3 and CaO. The contents of MgO, SiO2, Fe2O3, and CaO are about 35.8%, 36.8%,
7.6%, and 3.8%, respectively.
The reaction of serpentine rock was studied using Hydrochloric acid as a leaching agent to dissolve Mg2+ ions as magnesium chloride to obtain magnesium chloride hexahydrate. Parallelly, silica was precipitated.
The leaching of serpentine rock was studied using two
techniques: applying one variable at a time and applying the experimental statistical design. The effect of different operating parameters, such as reaction temperature, reaction time, and stoichiometry, on magnesium oxide recovery, is studied.
The optimum results of leaching applying one variable at a time
gave a slightly higher MgO recovery of 97.6% than the leaching
Summary and conclusions
applying the experimental statistical design, which showed 96.9% MgO recovery 96.9%.
The optimum leaching conditions for Egyptian serpentine ore to obtain 97.6% MgO recovery were 100% ‐75 µm particle size,
95 °C reaction temperature, 3 hours reaction time, 1:5 solid: liquid
ratio in g/mL, and 5M HCl concentration.
In addition, the dissolution kinetics of serpentine rock with hydrochloric acid was studied in detail. The main results reveal that the obtained activation energy and the solid‐liquid reaction model were crucial to the dissolution kinetics of serpentine ore. The results of the kinetic study show that product layer diffusion may be the best method for regulating the rate of serpentine dissolution in HCl with an activation energy of about 44.4 kJ.mol‐1. The liquid/solid ratio of 5:1 ml/g was applied for the experimental statistical design technique. The mathematical model was generated. The results are presented as a 3‐D cube and showed that at high parameter levels (4 hours reaction time, 95 ºc reaction temperature, and 1.6 HCl: MgO stoichiometry, the achieved magnesium oxide recovery was about 96.5%. On the other hand, the recovery of magnesium oxide was 67.1% at low parameter levels (2 hours reaction time, 65ºc reaction temperature, and 1.4
HCl: MgO stoichiometry).
Then after leaching, filtration of the slurry to separate the
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magnesium chloride pregnant solution from the precipitated silica and unreacted residues using a vacuum filtration technique. The achieved filtration rate of magnesium chloride solution is 36 mL/min under a pressure difference of 550 cm3.Hg.
After separation, the pregnant solution of magnesium chloride was
purified from calcium and iron ions. These impurities reacted with hydrochloric acid spontaneously during the serpentine reaction. The stoichiometric amount of sulfuric acid was added to the solution to precipitate calcium ions as calcium sulfate dihydrate. Then, after filtration and for ferric ions precipitation, an ammonia solution was added till raising the pH to 5.5–6.0 to ensure the precipitation of ferric ions and precipitation of Al3+, Fe2+, Ni2+, Co3+, and Cr3+ ions as well in the hydroxide forms. Then the purified pregnant solution was evaporated to obtain MgCl2.6H2O crystals.
Material balance, MgO and SiO2 mass balances of Egyptian Serpentine rock, including leaching with hydrochloric acid, filtration & washing as well as purification, were calculated. Consumption and production pattern for producing 1 Ton MgCl2.6H2O crystals was calculated. The results show that for the production of 1 Ton MgCl2.6H2O, 0.57 Ton from Serpentine rock,
1.56 Ton from 37% Hydrochloric acid, 30 Kg of 98% Sulfuric acid,
278 Kg of 28% Ammonia solution and 2.26 Cubic meter of Distilled water were consumed.