Nickel-Cadmium Battery

Nickel:

Nickel is a hard, silver white metal and can be found in two different geological environments.  Nickel ores can be found as a sulphide ore where the sulphide nickel mineral, pentlandite (Fe, Ni)9S8 is found with pyrrhotite  (FenSn+1), pyrite (FeS), and chalcopyrite (CuFeS2) in lodes in mafic and ultramafic igneous rocks. The major lateritic nickel mineral is garnierite ((Ni, Mg)SiO3.nH2O) and nickeliferous limonite (nickel mixed with hydrated iron oxide). The nickel grade of sulphide ore typically ranges from 1-4 % nickel, and that of lateritic ore from 1-2 % nickel. To produce this metal, the ore is heated in a blast furnace.  The sulfur is then replaced with oxygen.  Next, the oxides are treated with an acid that reacts with the iron and not the nickel.

Workers working in the powder metallurgy industry are exposed to metallic nickel.  However, workers that use nickel in high temperature metallurgical processes are exposed to metallic and oxidic forms of nickel.  In battery-manufacturing processes emit metallic nickel, oxidic nickel, and nickel hydroxide.  When grinding and polishing nickel-containing alloys, the workers are generally exposed to metallic nickel.  Typically, nickel species in these industries are in the physical form of particulates or fumes.  However, in electroplating processes, emissions of aerosols of soluble nickel sulfate or chloride result, depending on the nickel form used in electrolytes. Typically, nickel species in these industries are in the physical form of particulates or fumes.  However, in electroplating processes, emissions of aerosols of soluble nickel sulfate or chloride result, depending on the nickel form used in electrolytes.

Fig. 3- Nickel

 

 Potassium Hydroxide (The Electrolyte): 

2 K  +  2 H2O --> 2 KOH   +   H2

To form potassium hydroxide, potassium reacts violently with water.  A liberating hydrogen also forms.  The heat involved in the reaction must be sufficient to ignite the hydrogen liberated.

 

Potassium is usually widely distributed in nature, being the seventh most abundant element. Ocean water contains about 0.07% of potassium chloride. This water needs to be evaporated in order for the potassium salts to start to crystallize. Potassium can also be found in many volcanic rocks, by which disintegration and retain it in the soils, allowing plants to use it. The main potassium ores are: sylvite (KCL), the carnalite (KCl.MgCL2 6 H2O), the langbeinite (K2SO4. 2MgSO4), and the polyhalite (K2SO4.2CaSO4.2H2O).

However, because of its high reactivity, potassium is not found naturally in its elemental state. Furthermore, potassium compounds do not occur in workable deposits and are not found concentrated in one location. Potassium metal is prepared by heating potassium carbonate with charcoal as shown in the following reaction:

2C + KCO3--> 2K + 3CO2

                      

Pottasium metal is a soft silvery-white lustrous metal, which can be easily cut with a knife.  It is also highly reactive, tarnishing readily in air due to the formation of a layer of potassium oxide on the surface of the metal.

4 K   +   O2 -->   2 K2O      

            Potassium hydroxide is a highly corrosive alkaline solution that has to be handled with caution.  If any is exposed to skin or clothing, water should be used to rinse it out.  Vinegar, lemon juice, and boric acid could also be used. 

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