The Minerals of Beryllium and the Method to Extract it from Beryl
Existence in Nature
Beryllium is known to occur in ten different oxide minerals such as behoite (Be(OH)2) and the well-known chrysoberyl (under different light sources color-changing gemstone variety known as alexandrite) (BeAl2O4) (Figure 1 Left). Niveolanite (NaBe(CO3)(OH)·2H2O) is the only known carbonate. Four borates are known to include Be: berborite (Be2(BO3)(OH,F)·H2O), hambergite (Be2(BO3)(OH)), londonite ((Cs,K,Rb)Al4Be4(B,Be)12O28), and rhodizite ((K,Cs)Al4Be4(B,Be)12O28). A larger group of minerals is found in the phosphate class, such as beryllonite (NaBePO4), herderite (CaBePO4(F,OH)) (Figure 1 Right), tiptopite (K2(Na,Ca)2Li3Be6(PO4)6(OH)2·H2O), and zanazziite (Ca2Mg5Be4(PO4)6(OH)4·6H2O).
Extraction from Minerals
Beryllium is generally extracted from the mineral beryl (and bertrandite), which is either sintered using an extraction agent or melted into a soluble mixture. The sintering process comprises mixing beryl with sodium fluorosilicate, Na2(SiF6) and soda at 770C to form sodium tetrafluoroberyllate, Na2BeF4, aluminum oxide, Al2O3, and silicon dioxide, SiO2. Beryllium hydroxide, Be(OH)2, is precipitated from a solution of sodium tetrafluoroberyllate and sodium hydroxide, NaOH, in water.
Extraction of Be using the melt method comprises grinding beryl into a powder and heating it to 1650C. The melt is quickly cooled with water and then reheated to 250C-300C in concentrated sulfuric acid, mostly yielding beryllium sulfate, BeSO4·4H2O and aluminum sulfate, Al2(SO4)3. Aqueous ammonia is then used to eliminate the Al and S, leaving Be(OH)2. Be(OH)2 formed using either the sinter or melt method is then converted into BeF2 or BeCl2. To synthesize the fluoride, aqueous ammonium hydrogen fluoride is added to Be(OH)2 to produce a precipitate of ammonium tetrafluoroberyllate, (NH4)2BeF4, which is heated to 1000C to form BeF2. Next, heating the BeF2 to 900C in the presence of magnesium results in finely divided Be, and additional heating to 1300C produces the compact metal. Heating Be(OH)2 forms the oxide, which becomes beryllium chloride when combined with carbon and chlorine. Electrolysis of molten beryllium chloride is then employed to obtain the metal.
