Lead Acid Battery – Recycling:

Introduction:

Lead is one of the most recycled non-ferrous metal in the world. Used lead acid batteries accounts for

63% of world demand for lead. Lead is a rare metal. It is not found abundant in nature. Even the ores

containing 3% lead are being utilized.

Lead is a poisonous metal and is a cumulative poison. Increased exposure will result with neurological

disorders. Recycling helps to protect the environment. But at the same time the re-cycling process itself

is dangerous to workers. Norway has no Lead-recycling units, all they do is to collect the used batteries

and export them to other countries for re-cycling. The annual demand (as on 2008) for lead is around

8.7 million tpa. Around 3.9 million tpa of lead is produced from mining. The following are the recycling

plants in the world.

Asia – 53 plants – 425,000 tpa

America – 67 plants – 1,500,000 tpa

Europe – 46 plants – 1,150,000 tpa

Africa – 17 plants – 67,000 tpa

The above list is not including the recycling plants of capacity less than 1000 tpa.

The process of Recycling:

It mainly consists of three steps : 1. Wrecking 2. Smelting 3. Refining.

The wrecking section consists of spike crusher, acid separator, plastics separator, neutralization tank,

thickener and storage for lead fraction.

The smelting section may use rotary reverberatory furnace, or stationary furnace or blast furnace. Here

materials like soda, carbon, Iron, calcium oxide etc are added to reduce lead oxide, lead sulphate into

mineral lead. Other plastic contaminants, rubber, paper etc will be burned out.

Refining is the process of re-melting the smelted lead, alloying and refining by removal of antimony,

copper, arsenic etc. Refining process is carried out batch wise depending on the need in pot and kettle

furnaces.

There are other methods to smelt the whole batteries to avoid other operations like battery crushing,

separation of non-lead components and storage of crushed materials.

The youtube video about the recycling process is available here:

http://www.youtube.com/watch?feature=player_detailpage&v=-HH-YrA8v_M#t=0s

Recyclable and non recyclable uses of lead.

Lead used in batteries, roofings, pipes, cable sheaths, radiation shielding etc can be recycled.

Lead used in gasoline additives, glass, paints, plastic stabilizers, solders, ceramics etc cannot be re-

cycled. Non –recycling uses of lead is banned in many countries.

Composition of Lead acid battery:

Metallic lead 17%

Lead oxide and lead sulphate 50%

Plastic 5%

Acid 24%

Residuals 4%

Apart from this there are chemical additives such as cadmium, antimony, arsenic, tin and copper in small

amounts to increase the hardness. Cadmium is not used as additive in Europe as it will produce toxic

volatiles during smelting.

Compounds of Lead: out of many compounds of lead, lead oxide especially lead sub oxide (LSD) or grey

oxide is the most extensively used compound in battery manufacturing. Other compounds find less uses

or their uses are restricted/banned due to the poisonous nature of lead.

Lead oxide: Lead monoxide ( PbO ) or Litharge or yellow lead oxide

Lead dioxide ( PbO2) or brown lead oxide

Tri lead tetroxide ( Pb3O4) or Red lead oxide

Lead sub oxide (2PbO.Pb.H2O) or Grey lead oxide

Grey Lead Oxide ( Lead sub oxide) is used on an extensive scale for preparation of plates in Lead Acid

Batteries which requires production to strict specifications .Refined Lead (99.97% purity) ingots are the

required input for LSO manufacturing plant, which uses the ball mill process. It comprises of a small

Lead Melting Furnace, operating in line with a hemispherical ball-casting machine, which feeds the balls

to the ball mill .In the ball mill, Lead is converted to Lead Sub Oxide in an exothermic process, in

conditions of a maintained temperature range of 135-145 degrees centigrade and constant airflow. The

Grey Oxide is harvested through a high efficiency cyclone, bag-house filtration unit and induction draft

fan arrangement. It is in a grey powder form.

Red Lead (Tri lead tetroxide) is also used to a certain extent in the ceramics and glass, paints and

pigments and explosives industries.

Lead di oxide ( brown Lead ) is used extensively in lead acid batteries.

Litharge (Lead monoxide), an important intermediate, is used in a variety of industries like ceramics

and glass, lubricants and greases, insecticides, inorganic pigments, petroleum refining, rubber and PVC.

Other compounds of Lead

Lead azide – Pb(N3)2

Lead bromate - Pb(BrO3)2.H2O

Lead Chloride - PbCl2

Lead Nitrate - Pb(NO3)2

Tetra ethyl Lead (TEL) – Pb(C2H5)4

Lead Arsenate – Pb3(AsO4)2

Lead carbonate – PbCO3

Lead chromate – PbCrO4

Lead silicate – PbSiO3

Lead azide is an explosive. It is prepared by synthesis between sodium azide and lead nitrate. Another

method is the action of lead acetate on sodium azide. It is used in detonators to initiate secondary

explosive.

Lead bromate when mixed with lead acetate it detonates.

Lead acetate is a colorless powder with sweetening taste. It is produced by treating lead oxide with

acetic acid. It is used as a reagent to produce other lead compounds. It is used in men’s hair coloring

products.

Lead chromate is an yellow solid insoluble in water prepared by the action of sodium chromate on lead

nitrate. It is used in paints under the name “chrome yellow”

Lead nitrate is a colorless white powder prepared by dissolving elemental lead or lead oxide in

concentrated nitric acid. Unlike other lead compounds lead nitrate is soluble in water. Its main use as a

raw material or reagent for the production of other lead compounds especially chrome yellow. It is used

in the gold extraction process to increase the leaching speed.

Lead chloride is colorless white powder prepared by the action of sodium chloride on an aqueous

solution of lead nitrate. It is one of the most important lead based reagents.

Tetraethyllead (TEL) is prepared by the action of ethyl chloride on sodium-lead alloy. It was used as

gasoline additive as anti-knocking agent.

Lead arsenate (LA) is prepared by the action of lead nitrate on arsenic acid or sodium arsenate.It was

used as an insecticide and fungicide.

Lead carbonate or white lead is a white crystalline solid insoluble in water prepared by the action of

carbon-di-oxide on lead acetate. It was used as a white pigment in paints. For centuries it was used in

cosmetics. It is used in construction as an additive in variety of cements and putty.

Lead silicate - toxic white crystals used in ceramic, paints,enamels and fire proof fabrics.