CHEMISTRY & SOCIETY

1. CHEMISTRY & SOCIETY RECYCLING Dr. Victor Vilchiz Fall 2011

2. Bauxite • It is so abundant that we probably can go on using new cans from the point of view running out of Al. • But is the abundance of Bauxite the only important factor? • NO • How much energy goes into making a new can?

3. Making a can • The bauxite is mixed with other chemicals and must be heated to 1000C. • Is it cheaper, energy wise to recycle the can we just used? • To make 1 metric ton (1000kg) of aluminum from bauxite we used energy equivalent to 120,000 kg of coal.

4. Making a can • That is about ¼ of a million pounds of coal • We use about 110 billion cans a year • We recycle about 60 million cans a year (~60%) • We only used 10% of the energy if we recycle. • While we may not run out of bauxite to make new cans we may run out of coal to process the bauxite.

5. Making a can • How is a soda can made anyways? • It is mostly aluminum but there are other materials needed as well. • The can is made out of an alloy of Mg, Mn, Fe, Si, and Cu. The lid which is a bit harder contains slightly more Mg. • Now, I am sure you do not want your soda tasking like aluminum so a coating of plastic is applied to the inside. • We must know what kind of soda we are about to buy so some paint is used in the outside.

6. Recycling the can • Before melting the can it must be dry. If liquid water comes into contact with molten Aluminum an explosion can occur. • The paint must be removed in a furnace. • The can is melted; due to the higher content of Mg on the can’s lid the resulting molten alloy is not suitable for new cans.

7. Recycling the can • On the same token because the can contains less Mg than the lid the molten alloy is not suitable for lids. • Add Mg to make it suitable for lids or • Add Aluminum to make it suitable for cans. • Alloy: A physical homogeneous blend of metals with different properties than the initial components.

8. Recycling Metals • It is possible to recycle metals even when they are “lost” in solution. • Silver, Gold, etc (precious metals) are recovered making use of the reactivity metal series through RedOx reactions. • Reactivity Series: a list that ranks how “reactive metals are in solution”

9. Reactivity Series • A metal that is more reactive than another will “push” the less reactive metal out of solution. • For example, Copper is more reactive than silver; therefore, a copper wire put into a solution containing silver ions will push the silver out. Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)

10. RedOx Reactions • RedOx reactions are arguably the most important type of reactions there are. • They are responsible for transforming breathable oxygen to usable oxygen. • They are responsible for most cellular reactions. • They are responsible for the ATP-ADP cycle.

11. RedOx Reactions • A RedOx reaction is broken down into two parts • REDuction Reaction: A reaction in which electrons are gained. • Ag+(aq) + e- Ag(s) • OXidation Reaction: A reaction in which electrons are lost. • Cu(s) Cu2+(aq) + 2e-

12. RedOx reactions • We cannot have one without the other since the electrons gained in the reduction reaction must had to have come from somewhere (oxidation reaction).

13. Plastics • Plastics is just the common name for a group of chemicals. • The general common name of plastics is POLYMERS. • A polymer is a long chain of MONOMER units. • They are separated (recycling) by a number.

14. Plastics/Polymers • Polymers are made mainly through two different processes. • Condensation Polymerization • Produces Water and usually small(er) chains • Produces “pure” polymers (no impurities) • Radical Polymerization • Requires Initiator and Quencher (impurities) • Can create large(r) chains • Can create “living” polymers

15. Plastic Recycling • The number inside the triangle determines which type of plastic you have. Not all plastics are recycled everywhere. Some processes are more expensive than others.

16. Uses of Recycled Plastic • Used to make: • Rugs • Sleeping Bag Fillings • Clothing (jackets) • Packing (Styrofoam beans) • Bottles

17. Recycling Plastic • What the numbers mean… • #1 PETE (PolyEthylene TEraphthalate) • Soda bottles, food trays… they become rug carpets • #2 HDPE (High Density PolyEthylene) • Milk & Water Jugs… they become new containers or “lumber” • #3 Vinyl but mainly PVC (PolyVinyl Chloride) • Plumbing Pipe… it can be recycled but not enough discarded to make it worth it to do so.

18. Recycling Plastic • What the numbers mean… • #4 LDPE (Low Density PolyEthylene) • Plastic Bags… become new bags or “lumber” BUT most cities won’t collect them since they are too light… you can take them to businesses that collect them for sell to recycling centers. • #5 PP (PolyPropylene) • “though” containers like yougurt, butter tubs… Not enough produced to make it worth recycling. • #6 PS (Polystyrene) • It cannot be recycled for savings… but broken down (physically) for packaging. • #7 Other • Not recycled as it is a blend of many polymers.

19. State of Recycling • Paper of Plastic? • This decision should depend on many things not only in if you are environmentally conscious. • The biggest contributor to landfills is paper. • Not all cities recycle plastic (Chesterfield county does not recycle plastic bags)

20. State of Recycling • The aluminum recycling industry is thriving and will continue to do so until other recycling processes catch on with the public. • Plastic Recycling is a relatively new industry and many cities still need to develop programs to recycle a larger number of plastic types.

21. Green Chemistry • Green Chemistry is a philosophy that is in tune with environmental efforts to reduce the amount of waste we produce. • It is based in an “Atom Economy” • We must used as many atoms from the initial chemicals as possible. • It is based on Six guidelines

22. Green Chemistry Guidelines • Prevention is better than cleanup • And it is also cheaper. • Maximizing the atom economy. • Use as much as possible and you may profit more. • Use safer chemicals in the production process. • Less likely to create a problem.

23. Green Chemistry Guidelines • Use non hazardous solvents • If an accident happens it does not harm the environment • Reduce use of energy • Pay attention at secondary resources • Biodegradable Products • If a product will cease to serve its purpose make sure it will be absorb by the earth quickly.