Recycling Solutions - Thanatia: The Destiny of the Earth's Mineral Resources - page 439

key. But collection not only entails additional transport mapping and costs but in
many ways a complete re-design of company strategy in order to facilitate e cient
recuperation of a product after its useful life has ended. Changes would need to
occur throughout the entire lifecycle - from product manufacture and distribution,
to marketing and re-integration into the system.
Second, sorting. It is not enough to collect in order to re-use or recycle. One
must go on to sort. Sorting, is a highly negentropic operation, which as with any
mechanical process, requires small amounts of energy, especially if done intelligently
as this saves a substantial quantity downstream.
Third, disassembly or dismantling. Both processes are mechanical with not
much energy input per unit weight of product. Disassembly does not destroy the
original product but detaches its components for their eventual fixing or partial
recovery. Dismantling, meanwhile, which does not distinguish between the func-
tional integrity of given devices is preferred if the purpose is purely a question of
component separation with no regard for their reuse.
Fourth, a finer mechanical separation like shredding that liberates in higher
or minor grade the different constituents. For instance, bolted and riveted joints
present good liberating e ciencies, especially when the materials considered are
brittle. Coatings and paints, in contrast, present a very low degree of liberation.
Glued and welded joints, as well as layers and inserts meanwhile, show intermediate
or variable e ciencies. The physical separation sequence may end in a conven-
tional grinding process, whose energy consumption increases exponentially as size
decreases. The final particle size depends on the number of metals to be recovered
and the yield e ciency to be achieved, with special attention paid to the minor
metals.
Fifth, pre-processing in parallel to beneficiation. To obtain fractions rich in
desired components, this kind of separation takes advantage of the differences in
each constituent material's density, magnetic or electric properties. A good physical
separation avoids impurities downstream and determines the quality of recycling,
albeit at the cost of a greater energy consumption.
Sixth, metallurgical processing. This step takes advantage of the already proven
metallurgical methods to extract metals from primary resources (see Chap. 8). As
in conventional metallurgy, the large scale integrated smelter-refinery plants of the
recyclate follow the metallurgical route of Cu, Pb or Ni. High temperatures allow
for the separation of metals into different phases: solid slag, melting phase and flue
gases. The melt predominately contains the principal metal, which later undergoes
electrolytic refining. The elements Cd;Hg;Zn;Se and other volatilised metals es-
cape as gases and may further be recovered from water slurries, or at least trapped.
Glass, ceramics and other oxidised metals are transferred to the slag. This slag may
contain low concentrations of Si, Ti, Ta, Nb, Be, Li and REE with uncertain rates
of economic recovery.