Recycling
The chemistry of recycling involves the treatment of commercial products to remove and isolate components for reuse in other products. The materials most commonly recycled are paper products, metals, glass, and plastics.
Nearly one third of all newspapers, as well as very large quantities of magazines and corrugated cardboard, are recycled. Newsprint consists principally of cellulose fibers, binders, and other additives to improve the appearance and feel of the paper and inks. The objective of paper recycling processes is to recover the cellulose fiber and to eliminate or greatly disperse the ink. This is accomplished either by a series of washing and filtration steps or by pressure-steaming the paper.
Nearly half of the metal produced in the United States is recycled metal scrap, the majority of which is from automobiles. Recycling iron scrap saves nearly 0.75 of the energy required for steel production with a concomitant reduction in air and water pollution. Recycling aluminum requires nearly 20 times less energy than producing aluminum from bauxite. Recycling also eliminates the need to mine the bauxite, reducing environmental consequences.
Glass is usually separated by color, cleaned, and crushed into particles suitable for melting (cullet). The amount of energy and overall cost reduction from glass recycling is not as great as for metals or paper, but recycling of glass does reduce the amount of landfill space communities require.
Plastics are sorted by their molecular structure and reused accordingly.Polyethylene terephthalate (PET) products, such as soft drink bottles, are either cut into chips and used directly, for example to make carpets, or depolymerized to the monomer and reused as starting material for making products such as soda bottles. High density polyethylene products, such as milk containers, are cut into small pieces and remelted to make detergent bottles. Polycarbonate water bottles are used to make automobile bumpers.Polystyrene products are melted and converted to foam insulation. Mixed plastics products as made into products such as wood substitutes. In any application where the plastic need only be cut and remelted, there is considerable savings of process costs and environmental benefits. Plastics are organic polymers derived from petroleum. The monomers of which most plastics are made must be synthesized and, subsequently, polymerized. There is likely to be an increased emphasis on plastics recycling as more products are made of plastic and space for landfills becomes scarce.
Recycling is a major industry, involving the reuse of substantial quantities of paper, plastics, metals, and glass. The benefits of recycling include conservation of natural resources, energy savings, and reduction of the need for waste disposal.
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