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Chapter 07

    Occurrence, Extraction and Isolation of Lithium, Beryllium and Fluorine

Beryllium

History :

Beryllium is not found in nature in free form. It was discovered by Vauquelin in the year 1797 and named as Glucinum due to sweet taste of its salt. Since the source of discovery of Be is beryl hence it is named as beryllium.

Occurraence:

 Beryllium is one of the loss familiar element constituting about 6 x 10 percent of earth crust. It is never found in native. It is found in small quantities as minerals. Most of which are complex- silicates. Some of the important minerals of this elements are:

 

Although bromellite, phenacite and bertrandite are quite rich in their beryllium contents but they are rare and hence they are unimportant from the commercial point of view. The chief source of beryllium is beryl Be3AI2 Sl6O18. About 10,000 tones of beryl are mined annually. mainly in the USA (70%), the USSA (20) and Brazil (7%), In India it is widely distributed in Bihar, Orissa, Tamil-nadu at Nellore and Rajasthan at Almer-Marwara

Extraction of beryllium from beryl ore :   The extraction of barvillurn from beryl ore is generally done by using the following methods:

  • German Method
  • American Method
  • Alkali-fusion method
  • Conversion of beryl into sodium tetrahydro beryllate, Na, BeF, and then electrolysis of Na BeF4 to get beryllium metal.
  • Conversion of beryl into Be and then electrolytic reduction of Beo into beryllium metal
  • German method : Finely powdered beryl ore is fused with Na Sif for several hours at 850 °C. So that beryl ore is converted into Na2 BeF4, a complex salt which is extracted with water. Impurities of iron are precipitated by bubbling alr through solution and removed by filtration. To the filtrate KOH is added to precipitate Be(OH)2 with some CaF2. Now the precipitate is treated with HF. Calcium fluoride which remains Insoluble is filtered off. The filtrate is evaporated which yields crystals of beryllium oxyfluoride (5BeF2.Beo).
  • American method :

    In this process the finely powdered beryl ore is chlorinated at 500 °C for several hours, Iron, aluminum and other impurities form volatile chlorides and are removed. The temperature is then raised to about 900 °C so that BoCl2 which is volatile at this temperature condenses into the condenser. The residue left mostly contains silica. The beryllium chloride produced is then electrolyzed by fusing it with a mixture of beryllium chloride and sodium chloride.

  • Alkali fusion method : The finely powdered beryl ore is loused with twice of its weight of KOH or K2CO2. The melt is cooled and further ground to fine powder. Now the powder is covered with water and then treated with an excess of H2SO4. It is then heated. Heating is continued with stirring till a fine white powder is obtained. The residue is then dissolved is water and filtered to remove SiO2.The filtrate contains sulphates of beryllium, aluminum and potassium. It is carefully concentrated so that aluminum crystalizes out as potash alum K2SO4 Al2(SO4)3 24H2O. The mother liquor contains BeSO4 and traces of K2SO4, and Al(S04)3 and some other impurities. From this BeSO, is separated by any one of the following methods.
    • Methylamine or ethylamino is added to the solution containing BeSO4, so that only Be(OH)2 is precipitated. This is filtered, dried and ignited to get beryllium oxide.
    • Acetic acid is added to the solution and the whole solution is digested so that basic beryllium acetate is formed. The solution is shaken with chloroform so that basic beryllium acetate passes out into chloroform but acetates of iron and aluminum remain in the aqueous layer. The chloroform layer is separated and evaporated. Now the solid basic beryllium acetate is ignited to get beryllium oxide.

    Preparation of the Metal:

    Two different methods are used for this purpose.

    Stock and Goldschmidt’s Electrolytic method : In this method, beryllium fluoride is dissolved in a fused mixture of sodium and barium fluorides. The resulting complex salt Na BaBeFg is then made to electrolyze at 1400 °C in a graphite crucible, which acts as the anode. The cathode is generally a water cooled rotating Iron tube on which tough rods of beryllium are formed. When the temperature reaches to about 700 °C, beryllium oxyfluoride and sodium fluoride are added into the electrolyte so as to raise the

  • fusion point and thereby keep the liquid from volatilizing. The temperature is now raised to M1300-1400 °C. Beryllium is deposited at the rotating cathode and is of 99.8 % purity. A matured of beryllium chloride and sodium chloride is also used for electrolysis. This mixture is taken in a ferro chrome vessel and is kept at B20 °C. The electrolysis is done using nickel cathode and graphite
    • anode in an atmosphere of argon.

    (ii) Reduction of the oxide method :

    This method is used by the Brush Beryllium Company. It involves the reduction of beryllium oxide by carbon. Beryllium oxide is powdered and mixed with powdered coke (copper or any other alloying metal can be added in order to get the alloy of beryllium). This mixture is introduced into an electric arc fumace. The lower part of the furnace is made of carbon, and serves as the receptacle of the charge and also as one of the electrodes. The other electrodes are made to suspend from the top and can be raised or lowered, so as to strike an arc Inside the furnace. The charge is introduced through the door on the right side. Carbon monoxide leaves through the exist on the left. The metal formed is drawn out through the tapping hole at the base of the furnace.

[D] Conversion of beryl into sodium tetra hydro beryllate, Na, BeF4 and then electrolysis of Na2BeF4 to get beryllium metal.

1) Conversion of beryl into Na BeF4:

The Inely powdered ore is taken and mixed with Nagsi Fe along with small amount of NaF. Then the whole mass is fused at the temperature 850-900 °C. After fusion the Be and Al present are converted into soluble Na,BeF, and insoluble sodium-aluminum hexafluoride NagAIF, respectively and SIO2 is obtained as residue. The fused mass which consists of Na, BeF. NagAIF and SiO2 is digested with water and filter. NaF is also used to react with SiF to form a complex, Na, SiFe which is further utilized as a fusion micture for beryl ore.

The filtrate contains Na BeF, and the residue contains SiO, and Na Alfe. Now evaporate the solution upto dryness to get solid Na BeF4

(11) Electrolysis of Na, BeF:

After evaporating the solution of Na. BeF to dryness, the residue (Na BF4 ) obtained is mixed with NaF and BaF, to increases its conductivity and decrease the volatility of loused mass at high temperature. Now whole mixture is fused at 1400’C. and put in a electrolytic pot made up of graphite and acts as anode There is a water cooled iron pipe dipped in molten mass which acts as a cathode. Be Is deposited on cathode. At a definite interval of time NaF and BaF2 is mixed to maintain the concentration of Be content in the fused electrolyte.

(E) Conversion of beryl into BeO and then electrolytic reduction of Be Into beryllium metal.

1- Conversion of Beryl into Beo: The finely powdered ore is fused with K Co, at 1500 °C in an electric furnace. The fused mass is evaporated with H.SO, and then digested with water and filtered. 1- Conversion of Beryl into Beo: The finely powdered ore is fused with K Co, at 1500 °C in an electric furnace. The fused mass is evaporated with H2SO4, and then digested with water and filtered. The filtrate consists of a mixture of BeSO4. Al2(SO4)3 and K2SO4 and insoluble residue contains silica. 

Now the filtrate containing sulphates of Be, Al and K is concentrated so that K SO Al2(SO4)3 and water obtained as alum. BeSO4, and some of Al2(SO4) remains The solution containing Al2(SO4)2 and BeSo4, is treated with hof and concentrate (NH4)2C02 solution to precipitate Al as Al(OH)3, and BeSO4. Is converted to soluble busic beryllium carbonate, Be(OH)2 BeCO3 .

Now solution is evaporated and then ignited to get Beo.

2- Electrolytic reduction of BeO to Be:

A mixture of powdered coke and Beo is prepared and put to arc-furnace and alternating current is passed. The furnace consists of a big carbon crucible provided with a tapping hole and surrounded with firo bricks as shown in figure 7.07 The crucible of carbon acts as one of the electrode. The other carbon electrode dips in tho charge mass and is held in vertical position. Now the electric arc is generated between the two electrodes so that Be is reduced to Be. It is obtained in molten state and separated through the tapping hole and CO flows from the side tube as shown in figure.

Physical Properties :

Beryllium is a silvery white metal of malleable character. It is least electropositive in its group. It has high melting and boiling points. Due to high value of specific heat it Fire Belick accounts for a non metallic character.

Chemical properties :

1. Action of air :

Beryllium oxidizes in presence of moist air. A protective layer of oxide Is formed when heated & Tapping nole to redness in presence of Or. It also forms Beo when bumt in air.

2. Action of water :

It does not react with water even with steam like Mg.

3. Combination with other elements :

It does not react with halogens but with halogen acids forming halides. However the reaction with lz is difficult.

4. Reaction with N2 and C:

Be forms nitride, BezN2 and carbide, Bez when it reacts with Ny and carbon respectively, at a temperature above 700 °C.

5. Action of acids :

It easily reacts with HCl or H SO, and evolves He gas. Be + H2SO4 — BeSO4 + H21 It is passive towards cold conc. HNO3 but produces NO, with hot acid.

6. Action with alkalis :

It reacts with alkalies to form its hydroxides and liberates H2 gas. An excess amount of alkalies forms berrylates.

  1. Beryllium also forms compounds like halides, nitrates, hydroxides, sulphates, carbonates and carbide etc which are hydrolyzed with H2O.

    Use:

    1. it is used in making alloys. Be-bronze contains 2.25 to 2.50″ Be. Be is hard just like steel and therefore used for making slip rings and springs for motors.
    2. It is also used for making X-rays window due to its high transparency.
    3. It is used as structural material in space technology. I is also used as moderator reflector af neutrons in nuclear reactors.
    4. It is also used in making computer parts and as a solid fuel in a propellant rockel.
    5. Be is used in gas mantles along with Be(NO) Fluorine.

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