Recycling of used lead acid batteries
Practical Action
energy intensive than producing new lead from ore (the production of recycled lead requires
35-40% of the energy needed to produce lead from ore.) Recycling also reduces dispersal of
lead in the environment and conserves mineral resources for the future when done in a proper
way (Thornton, 2001).
However recycling of used lead acid batteries according international guidelines is not a
simple process which can be done in small scale enterprises. Certain measures need to be
taken to prevent negative impact to people and environment. The processes involved in
recycling of used lead acid batteries will be summarised below following the descriptions in
the technical guidelines for the Environmentally Sound Management of Waste Lead-acid
Batteries (UNEP, 2003, http://www.basel.int/meetings/sbc/workdoc/techdocs.html).
Collection
Used acid lead batteries must be collected, transported and stored with proper care, in order
to avoid adverse health effects and environmental contamination. Special measures need to
be taken at collection points and batteries should NEVER be drained at collection points as
no guarantee can be given for safe treatment of the sulphuric acid with all hazards involved
with the drainage to health and environment.
The recycling technology
The recycling process can be divided into three major processes:
1. Battery breaking
2. Lead reduction
3. Lead refining.
Battery breaking
Batteries must always be drained before they enter the recycling process. They should only be
drained to a purpose built effluent treatment plant so that the acid can be treated and
neutralised. Next the batteries are broken in a hammer mill or another type of crushing
machine. Manual battery breaking should be avoided due to the health and safety risks
associated with this practice.
The pieces from the breaking process are placed in a tank, where the dissimilar densities of
the materials cause some to sink (lead), some to float (hard rubber and plastic) and liquids to
go into solution (battery acid). From here, the materials are separated and treated
individually.
The plastic is cleaned and transported to a plastic recycler. The acid is neutralized.
Lead Reduction
The battery scrap obtained from the breaking process is a mixture of several substances:
metallic lead, lead oxide, lead sulphate and other metals such as calcium, copper, antimony,
arsenic, tin and sometimes silver. In order to isolate the metallic lead from this mixture, these
materials are charged into a furnace together with appropriate fluxes & reductants, drosses,
returning slags and process dusts for smelting. Off-gases from the smelting furnace are
filtered and the dust collected is returned to the furnace. The metal tapped from the kiln is
transferred to refining kettles and processed to produce commercial quality lead.
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