Molecular Compounds: Choosing the
Right Materials and End-Life

• Most Canadians use and consume a large number of products
• We are now taking steps to live in a more sustainable way
• Ex: reusable containers and not plastic water bottles
(recycling)
• We must always think about the risks associated with the production of materials (risk-benefit analysis) which includes the raw materials and chemicals used in production, disposal, and effect on society and the environment

• Source of Molecular Compounds
• Many molecular compounds originate from living things (wood, crude oil, medicines from fungi and bacteria, foods for biofuels…etc)
• These natural resources can be renewable or nonrenewable depending on whether they can be regenerated in our lifetime (fungi=yes, crude oil=no)
• A petrochemical is a compound that is synthesized by chemically changing certain components of fossil fuels to create other substances (plastics, gasoline, paints, detergents, pesticides/herbicides, rubber…)
• To process petrochemicals takes a huge amount of energy and uses vast amounts of fossil fuels

• Consideration must be taken into account with the chemicals used when making new products as well as long term health/environmental effects and disposal
Plastic used for a pencil case can be either made from: a ) non-recyclable plastics (ending up lasting 1000’s of years in a landfill site and possibly polluting the water system) b) a biodegradable plastic, polylactide (PLA) that can be broken down by micro-organisms, oxygen and water and produced using corn and other starch rich foods. These types of products are not recyclable but are biodegradable. There are many products in the pharmaceutical, industrial and biomedical industries that use PLA c) an organically grown cotton which is a natural fibre produced by plants raised without pesticides or fertilizers. This cotton is a renewable resource. The pencil case will not be waterproof and may not be as durable as plastic
Which would you choose as a consumer? Be sure to educate yourself

• Disposal or “ end-of-life ” of materials in a product must be considered
• The chemical bonds that make plastic so durable also make most plastics resistant to any natural decomposition for years
• compostable means that the substance will decompose in a composting site within a set time frame
• plastic waste and its environmental effect is a serious concern
• plastic garbage is also accumulating at an alarming rate in our waterways (think the Great Pacific Garbage Patch…Google it, it’s gross)
• reusable products are the most friendly to our environment
• recyclable means it can be converted back into material that can be used in manufacturing new goods
• sadly, a lot of plastic cannot be recycled dues to additives such as dyes, softeners and ultraviolet inhibitors that make them unsuitable for recycling
• “upcycling” involves converting wastes into new products (sewing juice pouches to make a reusable bag)

A
• Combustion is a chemical reaction that results when a hydrocarbon (a fuel) is burned in oxygen gas and produces carbon dioxide and water and of course, energy
Ex: CH
4
+ 2O
2
 CO
2
+ 2H
2
O (+ energy)
• Complete combustion occurs when the oxygen supply is plentiful
• Complete combustion produces the cleanest (less sooty) and hottest flame
• Coal, propane and gasoline as common fuels
• Incomplete combustion also produces carbon monoxide which is a deadly gas

• Incomplete combustion occurs when oxygen supply is limited (operating a car), these flames are sooty, yellow and produce less heat
• Carbon dioxide is a greenhouse gas that contributes to global warming
• Most fuels are composed of organic compounds
(containing carbon)
• Many fuels also contain impurities like sulfur and heavy metals which if released into the atmosphere are also serious pollutants

• Releases only a portion of the energy available in the fuel and releases the most carbon monoxide and other gases (the most incomplete combustion occurs when car are idling cars, highway travelling cars burn fuel more efficiently)
• Soot particles from incomplete combustion are in inhalation hazard (many are toxic and penetrate deep into the lung tissue)
• Carbon monoxide during incomplete combustion is also a hazard. Carbon monoxide bonds to the red blood cell faster than oxygen and this is what causes suffocation and death
• Firefighters are dealing with hotter and more toxic domestic fires dues to the increased use of synthetic substances in the home (synthetic fibres, plastic). This is increasing the risk of certain types of cancers among these people
• Recent studies with forest fires are showing certain toxins
(alkaloids) being released from the wood

B
• Most metals are not found pure in nature but rather as minerals
• A mineral is a solid substance found in Earth, usually a crystalline ionic compound or a mixture of compounds.
• Sometimes a mineral is made up of a single element (gold, silver)
• Rock that contains enough of a valued resource that it can be mined for profit is called an ore
• Precious metals are highly desired metals like gold and silver
• Less valuable metals are called base metals (copper, zinc, nickel)
Ore:

Two Types of Mining
– Surface mining: when closer to the surface the ore is mined using a large open pit, large quantities of material are removed, returning the surface mine to its natural state after the mine closes is a huge environmental task
– Underground mines: miners drill shafts deep into the Earth to reach the ore

Metallurgy: extracting metals from ore and processing into useful form
• Involves chemical and physical reactions
• A huge quantity of ore must be processed to retrieve even a little metal (ex: copper ore can contain as little as 0.5% copper by mass)
• A metallurgist engineer must design a profitable process to separate and purify the metal from the ore

Impact of Mining on the Environment
• Huge source of income for Canada
• History of environmental concerns (pollution, environmental damage, toxic emissions, huge risk of water and land contamination) and human tragedy
• Today mining companies in Canada must fund detailed environmental assessment and strict plans for rehabilitating the land after the mine closes to the government before mining can begin, not all countries are as strict as Canada

C.
• Chemical waste dumps, tailing ponds, slag heaps are all places where water was deposited with no concern for human health or environmental safety
• Old abandoned factories, businesses, landfills, warehouses and military bases are also concerns for old chemical deposits
• Environment Canada reports there are tens of thousands of these sites in Canada
• Contaminated land contains hazardous substances in high enough levels to pose a threat to human or environment health
• These hazardous chemicals can interact with groundwater and soil
Tailing pond

Remediation : is the process of decontaminating land or water to be safely used again
• Not necessarily the same as total cleanup, depends on what the site is going to be used for (ex: playground vrs parking lot)
4 main remediation strategies
1. Do nothing and restrict land use in the area
2. Cover or encase the contaminated soil (ex: cap with concrete)
3. Excavate the entire site and replace the contaminated soil with clean soil, contaminated soil is dumped elsewhere in licensed land purchased for that purpose)
4. Treat and clean the soil and return the cleaned soil

Physical Treatment
• Flushing the soil with large volumes of fluid to flush out and collect the contaminants (using water, acids, bases, solvents or detergents) depends on the chemicals contaminating the soil
• Care must be taken that none of the flushing fluid escapes into the environment
Soil Washing Soil Treatment Plant with Flotation Cells

Chemical Remediation
Stabilization and Solidification:
• Uses chemical reactions to convert the contaminant into a safe form (ex: form a precipitate)
• Precipitate can be collected, mixed with a binding agent (like concrete) and buried in the ground
• Prevents dangerous chemicals from moving into the groundwater

Electrolysis
• Involves inserting electrodes (electrical conductors) into the ground and applying a voltage to remove toxic metal ions that are dissolved in groundwater
• Ground must be moist
• Positive metal ions attach to the negative electrode, metal build up and can be safely removed and even recycled

Chemical Oxidation
• Uses chemical reactions to convert the contaminant into a less hazardous substance
Bioremediation :
• Using living things to remove pollutants
• Certain plants and micro-organisms can consume or absorb toxins from the environment
• Most cost effective and less disruptive than chemical or physical methods, but may take longer
• The organism used depends on the site and the contaminant
• Some exist naturally in the ground, others are added to the site while others also need help getting started from us

Phytoremediation :
Using plants to remediate soil or water
• Plants are surprisingly effective at cleaning up a broad range of pollutants
• Plants use their root systems to draw up water and contaminants
• Some contaminants are decomposed with the plant, others have microorganism in the roots
• Some substances (like metals) cannot be degraded by the plant and accumulate in them
• Some plants have an unusually high ability to take in a trap metals
(sunflowers, geraniums)
• These plants can be harvested and the metals “mined” by burning and plant and getting the metal from the ashes
Marigold
Sunflowers for phytoremediation

• Today going “green” is good for industry
• Often involves changing a manufacturing process so it is less harmful to the environment, using less toxic materials, upgrading equipment, more efficient process
(less waste), using less energy
• Sometimes these changes are very expensive
• In the end however, the company makes more profit due to less waste, protects the environment, and becomes more competitive
• However it is consumers that must make the big changes: we must develop a less wasteful more sustainable approach to consumer product
Green chemistry Logos

• Why generate pollution if there is a greener
(less polluting) alternative?
• Environmental impact is minimal
• “benign by design”
STEP 1:
Use renewable resources as starting materials
• Ex: glucose can be used instead of benzene (a known carcinogen) in the production of certain plastics, however, using a food crop
(corn) to make glucose to make plastic takes this land and food away from people/livestock

STEP 2:
Use chemicals that have less environmental impact
• Ex: CFC’s used to be used to create and mold polystyrene (foam containers for fast food) but this gas eats away at ozone cause serious thinning of the ozone layer letting UV radiation get through. Now carbon dioxide is used which is safer, not flammable but does still contribute to greenhouse gases
12 Principles of Green Chemistry

STEP 3:
Use catalysts to increase reaction efficiency
• Catalysts make a chemical reaction occur faster without being consumed in the reaction
• Can be reused in the manufacturing process
• Can eliminate steps in the manufacturing process

STEP 4:
Use less energy
• Updating aging equipment
• Switching to more efficient furnaces that create more energy using less fuel
• Can change the process of manufacturing so less energy is used
STEP 5:
Waste not
• Recycle the material in industry that can be used again
(batteries)
• Avoid losing energy through heat loss, try to trap the heat in a “closed loop” system to use it again
• Closed loop systems can also gather hazardous substances to prevent them from being released into the environment