CHEMISTRY & SOCIETY

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

2. The price of technology • Recall from the first 2 weeks of the course we discussed the costs of a comfortable life. • Lets think about cell phones… • How many have cell phones? • Most likely your cell phone is powered by a Li-Cd battery. How long will it last? • 2 Yrs? • Then what?

3. Batteries and Waste • At least this one you can recharge but eventually it will join the Energizer, Ever-Ready, Duracell…. • IN THE TRASH • Cd is not an environmentally friendly metal • How much waste do you think you produce in one day? • Wrappers, left-overs, smog, plastic bags, light bulbs, batteries, paper, dirty water… • 4 lbs a day per person  1 billion lbs of trash A DAY

4. What happens to trash? • It does not disappear once it is picked up. • Depending on where you live it may: • Buried • Burned • Thrown in the ocean (illegal now) • Sending it into space has been considered • RECYCLE

5. Type of Systems • There are three different types of systems. • Open System: one where both mass and energy are free go in and out. • Closed System: one where energy is allowed in and out but mass is not. • Isolated System: one where neither mass nor energy can go in or out.

6. Nature’s Recycling • Mother Nature has organized the biggest recycling programs. • It recycles water, carbon matter, and oxygen (the 3 most important ones). • We humans have impacted these recycling processes as we will see later in this lecture.

7. The Earth • In our planet we have energy coming in from the sun and energy going out. There is usually no mass going out (unless we send the space shuttle to space). And unless we have a meteor coming into our atmosphere there is no mass coming in. • The planet earth is a Closed System.

8. Energy from the sun • What does the energy from the sun do for us? • Ever notice when you feel like you are coming down with something during the day you feel ok but at night you feel sick again? • Like plants you are sucking up energy from the sun • Provides energy for plants

9. Carbon Cycle • Energy from the sun is absorbed by plants. • Fruit or vegetables grow. • We eat fruit/vegetable. • We produce waste. • Goes to landfill. • Organic matter goes into the soil. • Organic Matter is used by plants again.

10. Water Cycle • The sun provides the energy required to evaporate water form large bodies of water (seas, lakes, and streams). • Evaporated water forms clouds. • It rains • Water go into reservoirs or underground • Perspiration of the soil • Evaporation…

11. Oxygen and CO2 Cycles • Along with the CO2 cycle they are the basis of life on earth. • During respiration Oxygen is consumed and CO2 is produced • During Photosynthesis CO2 is consumed and Oxygen is produced.

12. Chemical Reactions • Both the Oxygen and Carbon Cycle are intertwined through 2 chemical reactions. • Respiration • Inhale = Oxygen • Exhale= Carbon Dioxide • Photosynthesis • Input = Carbon Dioxide • Output = Oxygen

13. Chemical Reactions • There are two misconceptions about chemical reactions: • A chemical reaction represents what actually happens. • Writing chemical reactions is like looking at the ingredients for a meal and the final product. • They do not provide any idea as to the intermediate steps.

14. Chemical Reaction • There are two misconceptions about chemical reactions: • Chemical reactions go to completion • Unlike cooking where everything that goes into the pot is cooked, in a chemical reaction not all the starting materials are used by the time we are done. • Even when you start with the exact amount of what you need, there will be left-overs.

15. Chemical Reactions • Misconception #1 • If you want to know everything that happens • You need to know the Mechanism • Series of Elementary (single events) Reactions • Misconception #2 • Want to know how much of a reaction occcurs? • You need to study the Thermodynamics of the Rxn • Tells you about the equilibrium of the reaction

16. Human Intervention • We have interfere with many of nature’s processes. • We have cut down trees, this reduces the amount of O2 produce and the amount of CO2 removed. • We continue to use many non-replenishable resources. • It is time we try to slow down our damage and if possible reverse it.

17. Recycling • Just because we recycle it does not mean we are mending what we have damaged. • But it certainly mitigates the damage we do everyday. • We can recycle just about everything… lets concentrated on Aluminum.

18. Aluminum cans • Cans are made of Al, Mn, Fe, Mg, Si, Cu. • The aluminum used in new cans comes from Bauxite, Al2O3. • Aluminum is the third most abundant element on the earth’s crust. • The two most abundant are Si, and O in the form or SiO2, SAND.

19. Aluminum Ores Ruby Al2O3 +Cr Bauxite & a Penny Al(OH)3 Bauxite Shell Rock Core

20. 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?

21. 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.

22. 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.

23. 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.

24. 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.

25. 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.

26. 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”

27. 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)

28. 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.

29. 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-

30. 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).

31. 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.

32. 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

33. 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.

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

35. 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.

36. 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.

37. 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)

38. 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.

39. 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

40. 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.

41. 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.