Iron from Used Toner Cartridges

Students and teachers all do a lot of printing and photocopying.
If your laser printer or photocopier is like ours, it probably has a sign on it that says you should contact admin when it needs a new toner cartridge.

Have you ever wondered what is inside the "toner cartridge"?
The black "ink", the toner, is  actually a mixture of solid carbon and solid iron oxide. A polymer is included to improve the flow. The particles making up the mixture are very small, around 10 micrometers. In general, the smaller the particle size, the better the resolution of the final print.
These small toner particles carry a positive charge which enables them to be deposited electrostatically on a negatively-charged image. Once deposited on the paper, the paper is electrically discharged then heated so that toner particles melt and bind to the fibers of the paper.

So what happens to all the old, used toner cartridges?
It is estimated that about half of all toner cartridges sold each year end up in landfill.
The rest are collected and recycled.
Your "empty" toner cartridge probably contains about 8% of the original mix of carbon, iron oxide and polymer. Generally this left-over toner will have to be cleaned out before the cartridge can be re-filled.

New research has suggested that this left-over toner could be transformed directly into iron. Iron is the main component of steel, one of the most widely used metals in the world.
The researchers heated toner mixture in a furnace to 1550^oC, at which temperature iron oxide is reduced to metallic iron by the carbon:

iron oxide + carbon → iron + carbon dioxide

 The reported yield of iron from toner powder was 98%.

Reference:

Vaibhav Gaikwad, Uttam Kumar, Farshid Pahlevani, Alvin Piadasa, Veena Sahajwalla. Thermal Transformation of Waste Toner Powder into a Value-Added Ferrous Resource. ACS Sustainable Chemistry & Engineering, 2017; DOI: 10.1021/acssuschemeng.7b02875

Suggested Further Reading:
 Percent by Mass (% by mass)
Naming Ionic Compounds
Formula for Ionic Compounds
Name and Formula of Covalent Compounds
Balancing Chemical Equations
Oxidation and Reduction
Oxidation States (oxidation numbers)

Metal Extraction Concepts

Carbon Reduction Method for Extracting Metals from their Ores
Activity Series of Metals

Suggested Study Questions:

1. Convert 10 micrometers to a diameter in:
   • metres
   • nanometres
   • millimetres
   • centimetres
2. Write the chemical formula for each of the following substances:
   • iron(II) oxide
   • iron(III) oxide
   • carbon dioxide
   • carbon monoxide
3. Write a word equation for the reduction of each of the following iron oxides using carbon:
   • iron(II) oxide
   • iron(III) oxide
4. Write a balanced chemical equation for the reduction of each of the following iron oxides using carbon:
   • iron(II) oxide
   • iron(III) oxide
5. Give the oxidation state (oxidation number) for iron in each of the following:
   • metallic iron
   • iron(II) oxide
   • iron(III) oxide
6. Refer to the balanced chemical equations in question 4. In each equation, identify the
   • oxidant (oxidising agent)
   • reductant (reducing agent)
7. Is the reaction between iron oxide and carbon in the furnace an example of a redox reaction? Justify your answer.
8. About 40% by mass of the toner cartridge powder is iron oxide. A toner cartridge contains 80 g of toner, what is the mass of iron oxide in the toner cartridge?
9. At the end of its useful life, a tone cartridge still contains 8% of the original toner. What mass of toner is present in a the toner cartridge at the end of its useful life?
10. At the end of the toner cartridge's useful life, what mass of iron oxide is present in the cartridge?
11. Assuming the chemical formula for the iron oxide in the cartridge is Fe₃O₄, what is the maximum amount of iron in grams that could be obtained from an "empty" toner cartridge?
12. 350 million "empty" toner cartridges go to landfill each year in the world. If all the available iron could be recovered from each cartridge, what mass of iron would be recovered?

Nanoparticles to Remove Coral Bleaching Oxybenzone

Sunblocks contain a number of different compounds including oxybenzone which acts as a UV filter. The skeletal structural formula of oxybenzone is shown below:

Oxybenzone is soluble in water.
Before you go snorkeling in the Great Barrier Reef to be amazed by the beautiful corals, fascinating fish and other exciting wonders, you smother yourself in sunblock. When you step into the water, the oxybenzone starts to dissolve. Unfortunately, oxybenzone contributes to coral bleaching, the killing off of the tiny, colourful zooxanthellae marine algae that live inside corals. The result is that the coral loses its colour and appears white, as if it has been bleached.

Researchers have found a way to soak up the oxybenzone from the seawater using magnetite nanoparticles.

Magnetite, Fe₃O₄ , is a mineral made up of iron(II) and iron(III) oxides and is one of the main iron ores, that is, magnetite is mined in order to produce iron. Magnetite is ferromagnetic, that is, it is attracted to a magnet. It is the most magnetic naturally occurring mineral on Earth. If you could get the oxybenzone in the seawater to attach to magnetite nanoparticles then you could pull the oxybenzone out of the water using a magnet.

First, the researchers coated the magnetite nanoparticles with sodium oleate. The skeletal structural formula of sodium oleate is shown below:

Next, they oxidised the oleate coating to increase the number of hydroxyl (OH) functional groups:

Since oxybenzone can interact with other molecules via hydrogen bonds, magnetite nanoparticles  covered in a coating rich with hydroxyl functional groups increases the interactions between oxybenzone and the nanoparticles. Once the oxybenzone has hydrogen bonded to the nanoparticle coating, a magnet can be used to extract the particles from water.

Does it work?
One brave researcher applied sunblock, stepped into the ocean, waited 10 minutes, then collected a sample of the surrounding seawater. Back at the lab, chromatography was used to determine the concentration of oxybenzone in the water, 1.3 ppm. This is a disturbing result since it is known that the concentration needed to bleach coral is measured in parts per billion.
Next, the researchers prepared seawater samples. Some had no magnetite nanoparticles added, others had the nanoparticles added. Then they added 30 ppm oxybenzone to  all the samples. The concentration of oxybenzone in the samples with no nanoparticles did not change in an hour. In the samples that contained the nanoparticles, 95% of the  oxybenzone  was removed within the hour.

Reference
American Chemical Society. "Sopping up sunblock from oceans to save coral reefs." ScienceDaily. ScienceDaily, 21 August 2017.

Further Reading
Solutions Concepts
Water as a Solvent
Transition Metals (magnetism)
Fatty Acids
Carboxylic Acids
Nanoparticles and Nanotechnology
Parts per Million (ppm)
Chromatography
Experimental Design
Variables
2-Dimensional Structural Formula
Skeletal Structural Formula
Molecular Formula

Suggested Study Questions

1. For a molecule of oxybenzone:
• draw the 2-dimensional structural formula
• give the molecular formula
2. On the 2-dimensional structural formula of oxybenzone identify and name each functional group present.
3. Use diagrams to explain why oxybenzone is soluble in water.
4. Draw the 2-dimensional structural formula for oleic acid.
5. On your structural formula of oleic acid, identify and name the functional group(s).
6. Suggest a method by which you could change oleic acid into sodium oleate in the laboratory.
7. Suggest a method by which you could oxidise sodium oleate in the laboratory.
8. Explain the term "nanoparticle".
9. Why do you think the researchers chose nanoparticles of magnetite rather than bulk magnetite for this research?
10. Consider the description of the experiment used to determine the effectiveness of the magnetite nanoparticles in removing oxybenzone from seawater:
• What was the hypothesis being tested?
• What was the aim of the experiment?
• What variables need to be considered in this experiment?
• What is the independent variable in the experiment?
• What is the dependent variable in the experiment?
• Which variables are constant variables in the experiment?
• Why did the experimenters add nanoparticles to some samples but not to others?
• Write out a suitable method for this experiment.

Nano-zinc oxide and the Environment

Increasingly, we are making use of nanoparticles because of their unique properties compared to the same substance in bulk material. Many cosmetics, including sunscreens and sunblocks, now contain nanoparticles. When you go swimming or wash, these nanoparticles are washed off. Depending on where the nanoparticles are washed off, the waste water may directly enter a natural water system such as a river or ocean, it may end up in sewerage sludge, and it may eventually end up on land. What scientists do not know is just how many nanoparticles are entering the earth, air and water.

It is estimated that carbon nanotubes, which form part of a composite material in objects such as bicycle frames and tennis rackets, can take 10 years to breakdown and be released into the environment. On the other hand, about half of the cosmetic nanoparticles enter our waste water within one year.

Europe currently produces about 39,000 tons of nano-titanium dioxide per year, and it is estimated that the concentration of these nanoparticles in effected areas is now 61 micrograms per kilogram of ground. For humans, the maximum "safe" levels for exposure to these nanoparticles is set at:

• 2,500 mg/kg/day for oral exposure
• 2.4 mg/m³ for inhalation

While small amounts of zinc oxide are beneficial to plant growth, larger amounts can impair seed germination. Plants take up the free zinc ions in aqueous solution rather than the zinc oxide particles. This zinc becomes incorporated into the plants we eat. Zinc is an essential element in the human diet. The recommended dietary allowance of zinc for men is 11 mg/day, and for women is 8 mg/day. There are concerns that the increasing level of zinc in  plants may lead to accumulation of zinc in humans which will be detrimental to our health. Ingesting more than about 100 mg of zinc per day may lead to chronic toxicity.

Research into the environmental impact of nanoparticles, and their impact on plant and animal health, will continue for a long time.

Reference:
https://www.sciencedaily.com/releases/2016/05/160512084646.htm

Further reading
Nanotechnology: http://www.ausetute.com.au/nanotech.html
Graphene and Fullerenes: http://www.ausetute.com.au/graphene.html
Solutions Concepts: http://www.ausetute.com.au/solutions.html
Weight percent (w/w): http://www.ausetute.com.au/weightpc.html
Parts per MIllion (ppm): http://www.ausetute.com.au/partspm.html

Suggested Study Questions:

1. What is meant by the term "nanoparticle"?
2. If a nanoparticle of zinc oxide has a diameter of 20 nm, what is its diameter in:
   • metres
   • centimetres
   • millimetres
   • micrometres
3. Give an example of one property of bulk zinc oxide that is different to nanoparticles of zinc oxide.
4. Explain why zinc oxide nanoparticles are used in sunscreens.
5. What is a carbon nanotube?
6. Why are carbon nanotubes used in the production of bicycle frames?
7. Why are concentrations of titanium dioxide nanoparticles in soil given in units of micorgrams per kilogram of soil rather than in moles per litre?
8. Convert the following concentrations into parts per million (ppm)
   • 2,500 mg kg^-1
   • 2.4 mg m^-3
9. Using the recommended dietary allowance figures in the article, determine the mass in grams of zinc allowed for a:
   • 58 kg woman each day
   • 79 kg man each day
10. A typical vitamin pill contains 25 mg of zinc. By consuming 1 tablet per day, will the man or woman above exceed the recommended daily allowance of zinc?
11. 6 raw oysters contain 32 mg of zinc. How many oysters can the man and woman above eat before exceeding the recommended dietary allowance of zinc?
12. 85 g of cooked beef contains 7 mg of zinc. What mass of beef can the man and woman above ingest before exceeding the recommended dietary allowance of zinc.
13. 28 g of dry roasted cashews contain 1.6 mg of zinc. What mass of zinc, in grams, is present in 750 g bag of cashews?
14. 1/2 cup of cooked red kidney beans contain 0.9 mg of zinc. How many cups of red kidney beans would our man and woman above need to consume in order to achieve their recomended dietary allowance of zinc?
15. Do you think you should take a daily vitamin pill containing zinc? Justify your answer.

Coral Reef Dissolution

Coral reefs dominate much of the world's tropical coastline, covering about 15% of the seabed shallower than 30 metres.

The largest coral reef in the world is the Great Barrier Reef off the north-east coast of Australia.

What impact will increasing amounts of atmospheric carbon dioxide have on our coral reefs?

Find out in this edition of AUS-e-NEWS!

If you haven't received your copy of AUS-e-NEWS, or if you would like to subscribe to our free quarterly newsletter, AUS-e-NEWS, the email us at

 

DOSS and Oil Spills

The molecular formula for dioctyl sodium sulfosuccinate, DOSS, is shown on the right. This is the anionic detergent molecule that was used to disperse the oil from the Deepwater Horizon spill in the Gulf of Mexico in 2010. When applied to an oil spill, DOSS decreases the size of oil droplete and prevents large oil slicks from forming.
BP applied about 1.84 million gallons of DOSS to the 210 million gallons of oil that is estimated to have gushed out of the oil well.
At the time it was believed that DOSS degraded rapidly in the environment so that it would not harm the marine environment.

Recent studies, however,  have shown that DOSS persists in the environment for much longer than was previously thought. Four years after the Gulf oil spill, DOSS remains present in deep-sea sediments and corals and in sand patties on Gulf beaches. mean for marine life or for the people who frequent the beaches? Scientists do not yet know what this might mean for marine life or for the people who frequent the beaches so some Gulf beaches have signs to warn people not to touch the sand patties.

Reference:
Helen K. White, Shelby L. Lyons, Sarah J. Harrison, David M. Findley, Yina Liu, Elizabeth B. Kujawinski. Long-Term Persistence of Dispersants following the Deepwater Horizon Oil Spill. Environmental Science & Technology Letters, 2014; 1 (7): 295 DOI: 10.1021/ez500168r

Further Reading:
http://www.ausetute.com.au/members/detergent.html (detergent tutorial for members)
http://www.ausetute.com.au/members/soaps.html (soaps tutorial for members)
http://www.ausetute.com.au/members/molecularformula.html (molecular formula tutorial for members)
http://www.ausetute.com.au/members/structural2D.html  (2-dimensional structural formula tutorial for members)
http://www.ausetute.com.au/members/condensedsf.html (Condensed structural formula tutorial for members)
http://www.ausetute.com.au/members/skeletal.html (Skeletal formula tutorial for members) 

Suggested Study Questions:

1.  Explain why dioctyl sodium sulfosuccinate, DOSS, is an anionic detergent molecule.
2. Give the name for the type of formula shown for dioctyl sodium sulfosuccinate, DOSS, in the article
3. Identify the functional groups found on a dioctyl sodium sulfosuccinate, DOSS, molecule.
4. Identify areas of the dioctyl sodium sulfosuccinate, DOSS, molecule that are:
   • hydrophilic
   • hydrophobic
5. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in water.
6. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in oil.
7. Explain how dioctyl sodium sulfosuccinate, DOSS, molecules might help break an oil spoil up into smaller oil droplets.
8. Write a complete 2-dimensional structural formula for dioctyl sodium sulfosuccinate, DOSS.
9. Write a condensed structural formula for dioctyl sodium sulfosuccinate, DOSS.
10. Write the molecular formula for dioctyl sodium sulfosuccinate, DOSS.

Cyclodextrin

Researchers at Temple University's Water and Environmental Technology (WET) Center have been investigating the use of cyclodextrins in the treatment of waste water.
Cyclodextrins are made up of sugar molecules, bonded together to form a ring. An example of the structure of a cyclodextrin, alpha-cyclodextrin which is a 6-membered sugar ring, is shown below:

Cyclodextrins can be used in water treatment because they can bond to substances such as toxic organic compounds or heavy metals and hold them inside the ring structure. Owing to the many polar OH functional groups, cyclodextrins are water soluble, but the researchers have produced insoluble materials by coating a thin layer of cyclodextrin on sand, glass, silica and filter paper. Doing this allows the absorbent material to be collected, washed and re-used.

Reference:
Temple University (2013, September 24). New adsorbent is more effective and environmentally friendly for treating wastewater. ScienceDaily. Retrieved September 30, 2013, from http://www.sciencedaily.com­ /releases/2013/09/130924174152.htm

Further Reading
Carbohydrates: http://ausetute.com.au/members/sugars.html 
Functional Groups: http://ausetute.com.au/fungroup.html
Solubility: http://ausetute.com.au/intermof.html

Zeolites: http://ausetute.com.au/members/zeolites.html
Polymers: http://ausetute.com.au/members/polymers.html 

Suggested Study Questions:

1. What does the "cyclo" part of the name in cyclodextrin refer to?
2. Use the structure above to determine the molecular formula for alpha-cyclodextrin.
3. Use the molecular formula to determine the empirical formula for alpha-cyclodextrin.
4. Calculate the percentage composition of alpha-cyclodextrin.
5. Draw the structure of alpha-cyclodextrin and locate and identify the functional groups.
6. Use a diagram to explain how alpha-cyclodextrin dissolves in water.
7. Use a diagram to explain how alpha-cyclodextrin could be used to remove lead ions from water.
8. Draw the structure of alpha-cyclodextrin an clearly identify all 6 of the sugar molecules making up the structure. 
9. Activated carbon is commonly used to remove contaminants from water. What benefits do you think there might be in using cyclodextrin-derived absorbant materials instead of activated carbon? 

Concentration of Calcium Ions in Hard Water

AUS-e-TUTE has just added new complexometric titration resources for the determination of calcium ions in hard water.
Members should log-in to see the new tutorial, game, test and drill.

New Titration Resources

AUS-e-TUTE has just added new Complexometric Titration resources for the determination of calcium and magnesium ions in hard water.
Members can log-in to use the new tutorial, game, test and drill.

ausetute.com.au

Sulfur Cycle

Sulfur, an element found in proteins, is cycled through the Earth's atmosphere, oceans and land, and, as it does, it undergoes chemical changes.
Most of the sulfur found on Earth is found in seawater and in rocks, in particular sedimentary rocks like shales containing pyrite (iron(II) sulfide or iron disulfide) and  in evaporite rocks containing anhydrite (anhydrous calcium sulfate), baryte (barium sulfate) and gypsum (hydrated calcium sulfate). The amount of mobile sulfur is continuously increasing due its release during volcanic activity. Human activities such as the burning of fossil fuels including coal and natural gas are also increasing the amount of mobile sulfur on Earth because fossil fuels contain sulfur as an impurity.

The sulfur cycle can be represented by the following 4 steps:

1. The incorporation of sulfur from organic (carbon) compounds like proteins, into elemental sulfur and inorganic compounds such as hydrogen sulfide, and the sulfide minerals such as pyrite (iron pyrite or fool's gold).
2. Oxidation of hydrogen sulfide, elemental sulfur and inorganic sulfides into sulfate ions.
3. Reduction of sulfate ions to sulfide ions.
4. Incorporation of the sulfur from sulfide ions into organic compounds (including organic compounds that contain metal atoms), such as proteins.

The oxidation of sulfur (step 2 in the cycle above) plays a part in removing oxygen from the atmosphere by incorporating oxygen into sulfate ions. Scientists have thought for a long time that the contribution of the sulfur cycle in removing atmospheric oxygen  is not nearly as important as the role of the carbon cycle in removing atmospheric oxygen. New research is suggesting that the weathering of pyrite and its burial may be more important than originally thought in regards to regulating oxygen.

Reference:
Halevy, S. E. Peters, W. W. Fischer. Sulfate Burial Constraints on the Phanerozoic Sulfur Cycle. Science, 2012; 337 (6092): 331 DOI: 10.1126/science.1220224

Further Reading:
Writing Ionic Formulae
Naming and Writing Formulae for Covalent Compounds
Oxidation Number (oxidation state)
Writing Precipitation Reaction Equations
Balancing Molecular Equations
Oxidation and Reduction Concepts
Carbon Cycle

Suggested Study Questions:

1. Write the chemical formula for each of the following:
   • elemental sulfur
   • hydrogen sulfide
   • iron(II) sulfide (iron disulfide)
   • calcium sulfate
   • barium sulfate
   • sulfate ion
   • sulfide ion
2. Give the oxidation number (oxidation state) for sulfur in each of the following:
   • S₈
   • H₂S
   • CaSO₄
   • BaSO₄
   • CaSO₄.2H₂O
3. Seawater is an aqueous solution which contains ions such as, barium, calcium, and sulfate. As seawater evaporates, calcium sulfate and barium sulfate precipitate out of the solution. Write a balanced molecular equation for:
   • precipitation of barium sulfate from seawater
   • precipitation of calcium sulfate from seawater
4. Write balanced chemical equations for each of the following:
   • combustion of carbon in coal to form carbon dioxide
   • combustion of sulfur in coal to form sulfur dioxide
   • combustion of methane (natural gas) to form carbon dioxide
5. Consider this equation for the oxidation of elemental sulfur :
   2S + 2H₂O + 3O₂ → 2H₂SO₄
   • Determine the oxidation number (oxidation state) of sulfur in elemental sulfur and in H₂SO₄
   • Use this information to explain why this equation can be said to represent an oxidation of sulfur.
   • Identify a species that is being reduced. Explain why this species can be said to be undergoing reduction.
   • Explain why it is appropriate to refer to the equation above as a redox (oxidation-reduction) reaction
   • For the reaction given above give the formula for the oxidant (oxidizing agent) and for the reductant (reducing agent).

Amine Scrubbing

Fossil fuel-burning power plants, in particular coal-burning power plants, are a major source of a carbon dioxide, a greenhouse gas. When power plants begin capturing their carbon emissions to reduce greenhouse gases it will be an expensive undertaking. Current technologies use about one-third of the energy generated by power plants to capture greenhouse gas emissions, this is referred to as parasitic energy.

Although no commercial power plants currently capture carbon dioxide on a large scale, a few small-scale and pilot plants do. One commonly used process is known as amine scrubbing in which gas emissions are funneled through an amine bath, which absorbs carbon dioxide from the flue gases. Typical amine baths in use are:

• 32 % by mass aqueous 2-aminoethanol (NH₂-CH₂-CH₂OH) solution
• 25% by mas aqueous 2,2'-Iminodiethanol (HN(CH₂CH₂OH)₂) solution
• 40% by mass bis(2-hydroxyethyl)methylamine (CH₃N (C₂H₄OH)₂₎ solution
• 50% by mass 2-(2-Aminoethoxy)ethanol solution
  

 The amines are then boiled to release the CO₂. Additional energy is required to compress the carbon dioxide so that it can be pumped underground.
The energy needed for this process decreases the amount that can go into making electricity. Calculations show that for a coal-fired power plant, that could amount to approximately 30% of total energy generated.

A group of  scientists from UC Berkeley and EPRI have developed a computer model to calculate energy energy costs of carbon dioxide capture, release and compression, for any material including the amine baths above as well as zeolites (porous materials made of silicon dioxide) and MOFs (metal oxide frameworks).

Reference
Li-Chiang Lin, Adam H. Berger, Richard L. Martin, Jihan Kim, Joseph A. Swisher, Kuldeep Jariwala, Chris H. Rycroft, Abhoyjit S. Bhown, Michael W. Deem, Maciej Haranczyk, Berend Smit. In silico screening of carbon-capture materials. Nature Materials, 2012; DOI: 10.1038/nmat3336

Further Reading:
Greenhouse Gases and the Greenhouse Effect
Combustion of Hydrocarbons
Amines

Percent By Mass (weight) Concentration 
Zeolites


Suggested Study Questions:

1.  Give the name and formula of the four main naturally occurring greenhouse gases.
2. Give the name and formula of four human-induced greenhouse gases.
3. Write a chemical equation for the complete combustion of coal.
4. Anthracite is a type of coal that is made up of about 95% carbon. The combustion of 1g of coal releases about 1000 kJ of energy. Calculate the heat of combustion of anthracite in kJ/mol
5. Write the molecular formula for each of the 4 amines used in amine scrubbing baths.
6. On the structural formula for each of the amines used in amine scrubbers:
   • circle amino groups in blue
   • circle hydroxyl groups in red
7. For a 32% by mass aqueous 2-aminoethanol solution, calculate the mass of  2-aminoethanol present in
   • 1 kg of solution
   • 100 g of solution
   • 1 tonne of solution
   • 2500 mg of solution
8. What is the concentration in mol/L of the1 kg of  a 32% by mass aqueous 2-aminoethanol solution?

 

Light Bulb Elements

The traditional incandescent light bulb, currently being phased out in many countries because it is considered to be energy inefficient, is really nothing but a glass ball containing a thin filament of tungsten, a metal with a high melting point, in an inert gas such as argon. As electricity passes through the tungsten, the metal heats up and glows bright white. The argon gas prevents the tungsten coming into contact with oxygen and burning.

The compact fluorescent lamp, also known as CFL's or energy saving lights, are commonly being used to replace incandescent light bulbs because they are more energy efficient. Any fluorescent lamp is just a gas discharge tube that uses electricity to excite mercury vapour. CFL's contain between 1mg and 5mg mercury per bulb. Now, while this may not sound like much, it has been estimated that if all of the 270 million CFLs sold in the USA on 2007 were sent to landfills, this would represent about 0.13tonnes, or 0.1%, of all US mercury emissions. Mercury is a toxic metal, and, when disposed of in landfills and waste incinerators, can contribute to air and water pollution.

Light-Emitting Diodes (LEDs) are also considered strong candidates to replace energy inefficient incandescent light bulbs. LEDs consist of a semiconductor chip doped with impurities so that current flows easily in one direction but not in the reverse direction. Light is emitted when an electron falls to a lower energy level while traveling along the semiconductor. The colour of light emitted by an LED is determined by the compound the semiconductor is made of, eg, red though to yellow light is achieved using gallium arsenide phosphide, aluminium gallium indium phosphide, or, gallium (III) phosphide. However, LEDs also contain potentially hazardous substances such as lead and arsenic which are linked to several diseases such as cancers, kidney disease, skin rashes and hypertension.
University of California Irvine's Department of Population Health & Disease Prevention scientists have discovered that low-intensity red LEDs contain up to 8 times the legal amount of lead allowed in California as well as significant levels of arsenic, and that white LEDs, while containing the least amount of lead, contain high levels of nickel.

Reference
Seong-Rin Lim, Daniel Kang, Oladele A. Ogunseitan, Julie M. Schoenung. Potential Environmental Impacts of Light-Emitting Diodes (LEDs): Metallic Resources, Toxicity, and Hazardous Waste Classification. Environmental Science & Technology, 2011; 45 (1): 320 DOI: 10.1021/es101052q

Further Reading
Elements and Compounds
Metals and Non-metals
Definitions of a Mole
Ideal Gas Law
Parts per Million Concentration
Greenhouse Effect

Study Questions

1. Locate each of the elements listed below in the Periodic Table. Provide the symbol for each element.
• tungsten
• argon
• oxygen
• mercury
• lead
• arsenic
• nickel
• gallium
• phosphorus
• aluminium
• indium


2. Draw up a table using the headings metal, non-metal, and semi-metal, and place each of the elements above in the relevant column.
3. What does a Chemist mean when they refer to an inert gas?
4. Estimate the volume of an incandescent light bulb.
   • If the light bulb contains argon gas at 0.1kPa pressure, how many moles of argon are present?
   • Convert the moles of argon gas to a mass of argon gas.
5. Assume a compact fluorescent lamp contains 5mg mercury vapour at 0.3% atmospheric pressure and 25^oC.
   • How many moles of mercury does the compact fluorescent lamp contain?
   • Calculate the volume of the compact fluorescent lamp.
   • What is the concentration of mercury vapour in the CFL in parts per million?
6. There are many different ways to produce electricity; coal-fired power stations, power from uranium fission or from hydroelectricity schemes. For each of these types, discuss the impact on greenhouse gas emissions of replacing incandescent light bulbs with CFLs or LEDs.
7. If a person were to drop and break a compact fluorescent lamp at home, describe the steps that should be taken to safely clean up, and dispose of, the mess.
   
   
   

Carbon Dioxide and Climate Change

Scientists at Utrecht University, working with colleagues at the NIOZ Royal Netherlands Institute for Sea Research and the University of Southampton have been studying one of the hottest episodes of Earth's climate history, the Middle Eocene Climatic Optimum (MECO), which occurred around 40 million years ago in order to understand the relationship between Earth's climate and atmospheric carbon dioxide.

Algae use photosynthesis to harvest the energy of the sun, converting carbon dioxide and water into the organic molecules required for growth. Different isotopes of carbon are incorporated into these molecules depending on the environmental conditions under which algae grow. Ancient climate can therefore be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.

Using fossilised algae preserved in sediment cores extracted from the seafloor near Tasmania, Australia, by the Ocean Drilling Program, the scientists refined their estimates of carbon dioxide levels using information on the past marine ecosystem derived from studying changes in the abundance of different groups of fossil plankton.

Their analyses indicate that MECO carbon dioxide levels must have at least doubled over a period of around 400,000 years. In conjunction with these findings, analyses using two independent molecular proxies for sea surface temperature show that the climate warmed by between 4 and 6^oC over the same period, suggesting that increased amounts of carbon dioxide in the atmosphere played a major role in global warming during the MECO.

The rapid increase in atmospheric carbon dioxide levels around 40 million years ago approximately coincides with the rise of the Himalayas and may be related to the disappearance of an ocean between India and Asia as a result of plate tectonics, the large scale movements of the Earth's rocky shell (lithosphere).

References:

1. P. K. Bijl, A. J. P. Houben, S. Schouten, S. M. Bohaty, A. Sluijs, G.-J. Reichart, J. S. Sinninghe Damste, H. Brinkhuis. Transient Middle Eocene Atmospheric CO2 and Temperature Variations. Science, 2010; 330 (6005): 819 DOI: 10.1126/science.1193654
2. P. N. Pearson. Increased Atmospheric CO2 During the Middle Eocene. Science, 2010; 330 (6005): 763 DOI: 10.1126/science.1197894

Further Reading
http://www.ausetute.com.au/greenhouse.html
http://www.ausetute.com.au/ccycle.html
http://www.ausetute.com.au/carbon14.html
http://www.ausetute.com.au/isotopes.html

Study Questions

1. Write a chemical equation showing the conversion of atmospheric carbon dioxide into glucose by photosynthesis.
2. Explain what is meant by the term isotope.
3. Give the names and symbols of the three naturally occurring isotopes of carbon.
4. Which isotope of carbon is the most abundant?
5. Which isotopes of carbon are stable?
6. Which isotopes of carbon are unstable (radioactive)?
7. Write a nuclear decay equation for the unstable carbon isotope(s).
8. Explain how ancient climate can be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.

Carbon Capture and Storage (CCS)

Combustion of fossil fuels, such as coal, fuel oil, or natural gas, liberates large quantities of carbon dioxide, a gas that significantly affects global climate. A key technology that would reduce emissions and lead to more environmentally friendly power plants is the capture and storage of carbon dioxide from flue gases of power plants (carbon capture and storage (CCS)). CCS might be able to reduce CO₂ emissions resulting from the employment of fossil fuels for power generation and other uses in industry to near zero and thereby contribute to reducing greenhouse-gas emissions.
The Technische Universität Darmstadt has dedicated a pilot plant for capturing carbon dioxide contained in flue gases of power plants using two new methods:

• carbonate looping
• chemical looping

Carbonate looping involves utilizing naturally occurring limestone to initially bind CO₂ from the stream of flue gases transiting power plants' stacks in a first-stage reactor. The resultant pure CO₂ is re-liberated in a second reactor and can then be stored. The advantage of the carbonate-looping method is that even existing power plants can be retrofitted with this new method.

Chemical looping allows CO₂ to be captured with hardly any loss of energy efficiency. Under this method, a dual-stage, flameless, combustion yields a stream of exhaust gases containing only CO₂ and water vapor. The CO₂ can then be captured and stored.

Reference
Technische Universität Darmstadt (2010, November 7). On the way to CO₂-free power plants. ScienceDaily. Retrieved November 8, 2010, from http://www.sciencedaily.com­ /releases/2010/11/101103082306.htm

Further Reading
http://www.ausetute.com.au/combusta.html
http://www.ausetute.com.au/idealgas.html
http://www.ausetute.com.au/heatcomb.html
http://www.ausetute.com.au/greenhouse.html
http://www.ausetute.com.au/ccycle.html

Study Questions

1. Explain what is meant by the term fossil fuel.
2. Write a balanced chemical equation to represent the complete combustion of coal.
3. Write a balanced chemical equation to represent the complete combustion of natural gas.
4. If you burnt 1kg of coal and 1kg of natural gas, which reaction would produce the greatest amount of carbon dioxide?
5. If you burnt 1000cm³ of solid coal, and 1000cm³ of gaseous methane, which reaction would produce the greatest amount of gaseous carbon dioxide?
6. The heat of combustion of methane is 890 kJ/mol. Is energy released or absorbed during this reaction?
7. When coal burns it releases energy, about 250 kJ/mol. At 25^oC and 1 atmosphere pressure, is methane or coal the better fuel?
8. What benefits are there in storing the carbon dioxide emitted during power generation?
9. What disadvantages are there in storing carbon dioxide emitted during power generation?
10. What impact could the storage of this carbon dioxide have on the natural carbon cycle?
    

Dioxins in Sydney Harbour

Data collected by the NSW Department of Environment, Climate Change and Water (Australia) in 2008 shows that large tracts of sediments in Sydney Harbour are more contaminated with dioxins than Tokyo Bay or New York Harbour, and are among the most contaminated in the world.
In the remediation area in Homebush Bay, the location of the 2000 Sydney Olympic Games, the dioxin levels were 610 picograms per gram of sediment compared with 2.3 for a "clean" environment. These high levels of dioxins in areas where fish feed means the warning not to eat fish caught west of the Sydney Harbour Bridge, and to eat only 150 grams a month of fish caught east of the bridge, will most likely have to remain in place for decades.

The source of the contamination is the former Union Carbide site where dioxins were used in the manufacture of the now-banned pesticide 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) and the defoliant Agent Orange which was used during the Vietnam War.

Dibenzo-p-dioxin is made up of two benzene rings joined by two oxygen bridges, so it is an aromatic diether.
The name dioxin actually refers to the central dioxygenated ring. So, if other elements are substituted for the hydrogen atoms in the molecule, they too would be referred to as dioxins. This means there are many different compounds that can be referred to as dioxins!

In common use, the term dioxins usually refers to polychlorinated dibenzodioxins (PCCDs) which are a group of chlorinated dibenzo-p-dioxin molecules. In PCCDs the chlorine atoms can attach on 8 different places on the dibenzo-p-dioxin molecule (shown as 1,2,3,4 and 6,7,8,9 on the structure above). The toxicity of PCDDs depends on the number and positions of the chlorine atoms. The most toxic dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin, and is well known as the contaminant of Agent Orange.


Dioxins are known to build up in the human body over time, mostly in fatty tissues.
Exposure to high levels of dioxins causes a severe form of persistent acne known as chloracne and leads to an increased risk of tumours.
Exposure to low levels of dioxins results in an elevated risk of sarcoma, a type of skin cancer.

Reference:
http://www.smh.com.au/environment/water-issues/the-poison-that-got-away-20101029-177i0.html?autostart=1

Further reading
http://www.ausetute.com.au/massconv.html
http://www.ausetute.com.au/partspm.html
http://www.ausetute.com.au/namctut1.html
http://www.ausetute.com.au/namhaloa.html
http://www.ausetute.com.au/mmcalcul.html
http://www.ausetute.com.au/percentc.html
http://www.ausetute.com.au/namisane.html

Study Questions

1. Convert 610 picograms per gram to
• micrograms per gram
• nanograms per gram
• micrograms per milligram
• milligrams per kilogram
• parts per million
• parts per billion
2. Write the molecular formula for each of the following:
   • dibenzo-p-dioxin
   • 2,3,7,8-tetrachlorodibenzo-p-dioxin
3. Calculate the percentage composition of dibenzo-p-dioxin.
4. Calculate the mass of chlorine present in 610 picograms of 2,3,7,8-tetrachlorodibenzo-p-dioxin.
5. Indicate the location of ether functional groups on a molecule of dibenzo-p-dioxin.
6. Give the structural formula of as many different structural isomers of 2,3,7,8-tetrachlorodibenzo-p-dioxin as possible.
7. Name each of the molecules you have drawn in question 6.
   

Nanoparticles in Sunscreens

Titanium dioxide and zinc oxide are currently used for sunscreens because they absorb and scatter light. University of Tennessee, Knoxville, scientists have found that nanoparticles found in ivy may protect skin from UV radiation at least four times better.

A yellowish material is secreted by the ivy to aid it in clinging to surfaces. Nanoparticles within this material create the ability for the vine leaves to hold almost 2 million more times than its weight as well as provide the ability to absorb and disperse light due to their large surface-to-volume ratio. Sunscreens made with ivy nanoparticles would probably not need to be re-applied after swimming because the nanoparticles are more adhesive, and, while metal-based sunscreens give the skin a white tinge, the ivy nanoparticles are virtually invisible.

The study indicates that ivy nanoparticles are less toxic to mammalian cells than small-scale metal oxides, have a limited potential to penetrate through human skin, and are easily biodegradable.

Reference:
University of Tennessee at Knoxville (2010, July 19). Nanoparticles in English ivy may hold the key to making sunscreen safer and more effective. ScienceDaily. Retrieved July 22, 2010, from http://www.sciencedaily.com­ /releases/2010/07/100719162955.htm

Study Questions

1. Write the formula for titanium dioxide and for zinc oxide.
2. Give the oxidation state (number) for titanium and zinc in the compounds above.
3. What is a nanoparticle?
4. Explain the term surface-to-volume ratio.
5. Why do nanoparticles have a large surface-to-volume ratio?
6. How is the scattering of light affected by differences in surface-to-volume ratio?
7. Why are titanium dioxide and zinc oxide the preferred metal oxides for use in sunscreens?
   

New Membrane for Desalination

Reverse-osmosis desalination uses high pressure to force polluted water through the pores of a membrane. Water molecules pass through the pores of the membrane, but mineral salt ions, bacteria and other impurities do not. Over time, the pores become clogged and the membrane damaged, requiring expensive cleanup and membrane replacement.

UCLA scientists have produced a new membrane which could increase membrane life and reduce desalination plant operational costs. The new membrane is synthesized in a three step process:

1. synthesis of a polyamide thin-film composite
2. activation of the polyamide surface with atmospheric pressure plasma to create active sites on the surface
3. initiation of a graft polymerization reaction on the activation sites using a monomer solution to create a polymer "brush layer"

The polymer chains of the brush layer, which are chemically anchored to the polyamide surface, are in constant motion, much like seaweed that is in constant motion but anchored to the sea floor. This motion makes it difficult for bacteria and other colloidal matter to anchor to the surface of the membrane increasing the life expectancy of the membrane.

References:

1. Nancy H. Lin, Myung-man Kim, Gregory T. Lewis, Yoram Cohen. Polymer surface nano-structuring of reverse osmosis membranes for fouling resistance and improved flux performance. Journal of Materials Chemistry, 2010; DOI: 10.1039/b926918e
2. Myung-man Kim, Nancy H. Lin, Gregory T. Lewis, Yoram Cohen. Surface nano-structuring of reverse osmosis membranes via atmospheric pressure plasma-induced graft polymerization for reduction of mineral scaling propensity. Journal of Membrane Science, 2010; DOI: 10.1016/j.memsci.2010.02.053

Study Questions:

1. What is osmosis?
2. Name some mineral salt ions you would expect to find in seawater.
3. What is a monomer?
4. What is a polymer?
5. What is meant by the term polymerization?
6. Describe a polyamide.
7. Draw a table listing some polymers, their respective monomers, and the properties and uses of the polymers
   

Killer Seaweed in Coral Reefs

Studies have shown that several species of seaweed common in both the Pacific and Caribbean Oceans can kill corals upon contact using chemical means.

The study used racks of transplanted coral placed next to different types of common seaweed as well as plastic plants to simulate the effects of shading and mechanical damage. For comparison, other coral racks had neither seaweed not plastic plants near them. In as little as two days the corals in direct contact with the some seaweeds bleached and died.

Chemicals were extracted from the seaweeds causing death. These chemicals were applied to the corals in a gel matrix. As a control, the gel without the chemicals was added to a different group of corals. The results confirmed that these chemicals were responsible for the death of corals in contact with the killer seaweeds.

Overfishing of herbivorous fishes has resulted in more seaweeds being present amongst corals, and some of these seaweeds are responsible for the death of coral. The less coral there is, the fewer fish will be recruited into the area to feed, so the number of seaweeds increase, more coral dies.

Reference:
Douglas B. Rasher, Mark E. Hay. Chemically rich seaweeds poison corals when not controlled by herbivores. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.0912095107

Fluorinated Compounds Block Radiation

NASA and Purdue University researchers have released a new study that could be used by Industrial Chemists to develop alternatives with less global warming potential than materials now in common use. The study looked at fluorine containing compounds such as hydrofluorocarbons, perfluorocarbons, hydrofluoroethers, hydrofluoroolefins and sulfur and nitrogen fluorides.

Fluorinated compounds are more efficient at blocking radiation in the atmospheric window, the frequency range in the infrared region of the electromagnetic spectrum through which radiation from Earth is released into space which helps cool the planet. When radiation is blocked instead of being released a greenhouse effect results, warming the planet.

The number and placement of fluorine atoms in a molecule's structure is instrumental in determining its ability to block radiation. Fluorine atoms are very electronegative and form highly polar bonds with carbon and sulfur. Fluorine atoms tend to change the bond polarity of molecules, modifying the bonds holding the atoms in the structure, which, in turn, effects how a molecule absorbs infrared radiation.

Fluorinated compounds also persist longer in the atmosphere than carbon dioxide and other major global warming agents. Even if fluorinated compounds are emitted in lower quantities they might have a cumulative effect and some don't break down for thousands of years.

Partha P. Bera, Joseph S. Francisco, Timothy J. Lee. Design strategies to minimize the radiative efficiency of global warming molecules. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.0913590107

Molybdenum-oxo Complex to Split Water

Hydrogen gas, when used as a fuel, emits only water vapor as a product, making it potentially the 'cleanest' fuel around. Unfortunately, hydrogen gas has to produced and most of this comes from natural gas which is a fossil fuel. While the technique to produce hydrogen from natural gas is not expensive, it does add enormous quantities of carbon emissions to the atmosphere.

Hydrogen gas can be produced through the electrolysis of water, a cleaner and more sustainable method of producing hydrogen if the electricity required is generated via renewable technology such as solar or wind, but it requires a water-splitting catalyst.

Plants use enzymes, hydrogenases, during photosynthesis to split water, but these enzymes are highly unstable and de-activate when removed from their native environment.

Metal catalysts such as platinum are commercially available to split water, but these do tend to be expensive.

Scientists in the USA have found a molybdenum-oxo complex that acts as a catalyst for spiltting water without the use of additional acids or organic co-solvents. The new catalyst generates hydrogen from neutral buffered water or even sea water with a turnover frequency of ~2.4moles of hydrogen per mole of catalyst per second.

Hemamala I. Karunadasa, Christopher J. Chang, Jeffrey R. Long. A molecular molybdenum-oxo catalyst for generating hydrogen from water. Nature, 2010; 464 (7293): 1329 DOI: 10.1038/nature08969