Using resources

Ceramics, composites and polymers

  • Different materials have different properties, which make them useful for different things

  • Ceramics are hard, brittle, heat-resistant and corrosion-resistant materials

    • They are made by shaping and then firing a non-metallic material (like clay) at high temperatures

    • Mainly glass or clay ceramics (brick, china and porcelain)

    • Clay ceramics are made by shaping wet clay and heating to a high temperature in a furnace so it hardens

      • It has a high compressive strength - why it is used for building

    • Glass ceramics are mainly soda-lime glass

      • Made by melting a mixture of sand (silicon dioxide), sodium carbonate and limestone

      • The molten liquid is cooled, so it solidifies

      • Borosilicate glass is made by heating sand with boron trioxide - has a much higher melting point than soda-lime

      • Glass is transparent, strong and a good thermal insulator so is good for in windows

  • Composites are materials that consist of two or more materials with different properties, that have been combined to produce a more desirable material

    • Most have two components - one for reinforcement, like long solid fibres, and a matrix, which binds it together (starts soft and hardens)

  • Polymers are large molecules of high Mr, made by linking together lots of monomers

    • Properties depend on the original monomers and the conditions of the chemical reaction

    • Generally they are flexible, easily shared and good for electrical and thermal insulators

    • Poly(ethene) is a common polymer, and is has two main forms

      • Low-density poly(ethene) and high-density poly(ethene)

    • LDPE is made in moderate temperatures, high pressures and with a catalyst

      • It is more flexible but weaker

      • It is used in carrier bags, etc.

    • HDPE is made in low temperatures and pressures, with a catalyst

      • It is more rigid but stronger

      • It is used for drain pipes, etc.

    • Thermosoftening polymers are made by lots of polymer chains held together by weak intermolecular forces

      • These weak bonds break easily when heated, causing the polymer to break so it can be remoulded and cooled so it hardens again

    • Thermosetting polymers are made from lots of polymer chains held together by strong covalent bonds

      • Lots of energy is needed to break them, so they don’t soften when heated - are hard, rigid and strong

Corrosion

  • Corrosion is the process by which metals are slowly broken down by reacting with substances in their environment

  • Iron + oxygen + water → hydrated iron oxide (rust)

    • Fe → Fe3+ + 3e- (oxidised)

    • O2 + 4e- → 2O2- (reduced)

  • Conditions required for rust are oxygen and water

  • Only the surface metal corrodes

    • Layers can break away and completely break down with iron and rust

    • For aluminium, only surface atoms are affected - protected layer is formed

  • Prevention from rusting

    • Barriers - prevents oxygen and water from being in contact

      • Paint, oil/grease, electroplating (using electrolysis to cover the iron in a thin layer of another metal)

    • Sacrificial - adding a more reactive metal to the iron, like zinc or aluminium

      • If the object is exposed to oxygen, the more reactive metal will be oxidises instead

    • Galvanising - both barrier and sacrificial

      • A layer of zinc is added to protect, but if scratched the oxygen won’t reactive with the iron as the zinc is much more reactive

Sustainable development - recycle and reuse

  • Sustainable development is an approach to human and economic development that meets the needs of current generations without damaging future generations

    • It shouldn’t damage the environment, use up limited resources or add to global warming

  • We can use renewable resources

    • Wood instead of plastic (from crude oils) as it is more sustainable

    • We have to take the energy required for the manufacturing process into account, like if it uses fossil fuels

  • Ways to reduce the environmental impact of manufacturing:

    • More efficient processes - tiny amounts of oil needed

      • Catalysts

      • Optimum pressures and temperatures

  • After a product has been used, it is best to reuse or recycle it

    • Reuse - either for the same purpose or different

    • Recycle - if the products are too damaged, parts or elements can be separates, crushed/melted and made into new products of similar or different types

      • Fewer quarries and mines are needed

      • Less crude oil used, so land fill is reduced

      • Less energy is required than making new

Life cycle assessments (LCA’s)

  • LCA’s analyse the different stages in a products life cycle, and assess its environmental impacts

    • Extracting and processing raw materials

    • Manufacturing and packaging

    • Using the product

    • Disposal

  • Extracting and processing

    • Can directly damage local environment, through mines or deforestation

    • Indirectly damage the environment through huge amounts of energy being used, and pollutants being released (global warming)

  • Manufacturing and packaging

    • Energy use

    • Pollution - carbon monoxide or hydrogen chloride

    • Waste products - usually useless

  • Impact of using product

    • Damage it does during its lifetime

      • Pollutants from a car, fertiliser run-off

    • Length it is used for

      • Re-useable vs single use

  • Disposal

    • Land fill - takes up space, chemical damage

    • Burn waste - releases pollutants to atmosphere

    • Energy required for transport to these places

  • Limitations of LCA’s

    • Difficult to quantify exact amounts

    • Difficult to assess harm of each step and their comparisons

    • Can be manipulated to support a campaign

Potable water

  • Potable water is water that is safe to drink

    • Not necessarily pure (only H2O)

  • Criteria required for water to be potable

    • Levels of dissolved substances need to be fairly low

    • pH has to be between 6.5 and 8.5

    • There can’t be any microorganisms (bacteria or fungi)

  • Fresh water - only has a small amount of dissolved substances

    • For example, rain

    • Surface water - lakes, rivers, reservoirs (exposed at surface)

    • Ground water - aquifers (permeable rock that traps water in ground)

    • Surface water is easy to access and is frequently replaced, however it can dry up if hot, so ground water is relied on

  • Fresh water needs to be treated

    • Filter through a wire mess (removes large bits)

    • Pass through a bed of sand and gravel - filters small bits out

    • Sterilise it - bubble chlorine gas through, UV light or exposure to ozone

  • Some countries have little rain, so rely on desalination (extraction from sea water)

    • Desalination is done through distillation or reverse osmosis

      • Both are expensive as they require lots of energy - not practical in large amounts

      • Distillation - boil and collect water vapour to get pure distilled water

      • Reverse osmosis - salt water is passed through a membrane, which removes salt and ions to get pure distilled water

Waste water treatment

  • Sources of waste water:

    • Domestic - household waste (sinks, toilets, showers)

      • goes to sewers and then sewage treatment plants

    • Agricultural systems - nutrient run-off and animal waste

    • Industrial - from factories with chemicals

  • All waste water has to be treated

    • Domestic and agricultural - organic matter and harmful microbes have to be removed, as they could pollute fresh water (health risk)

    • Industrial - contain chemicals, so needs extra treatment

  • Sewer treatment

    • Screening - removing large objects

    • Sedimentation - the sewage is left in a settlement tank so that solids settle to form sludge and effluent

    • Effluent is separated and biological breakdown by microorganisms occurs to remove organic matter

      • Sludge occurs in anaerobic conditions - sealed so anaerobic digestion happens

        • Methane is produced, which can be trapped and burned as fuel

        • Waste can be used as a fertiliser

      • Effluent occurs in aerobic conditions

        • Air is pumped in - oxygen is supplied

        • Breaks down by aerobic digestion

        • Water is now safe to be released back into the environment

  • For toxic substances, additional stages have to occur

    • Adding chemicals to precipitate out metals

    • UV radiation

  • Sewage treatment is easier than desalination, though fresh water is best

The Haber process

  • The Haber process is the industrial production of ammonia from nitrogen and hydrogen

  • N2 + 3H2 ⇌ 2NH3 (and heat)

    • An iron catalyst, 450⋅\cdotc and 200 atm

    • The ammonia produced is used for nitrogen based fertilisers, to grow all food needed

  • Nitrogen is easy to acquire - from air

  • Hydrogen is harder as it has to be hade from hydrocarbons (like methane)

  • It is an exothermic reaction, and is a reversible reaction

  • Nitrogen and hydrogen enter and are compressed

    • They pass through the reaction vessel (450 degrees and 200 atm), where they react together to form ammonia

    • Not all hydrogen and nitrogen reacts - reversible reaction

    • The spare nitrogen and hydrogen and produced ammonia enter the cooling tank, where ammonia condenses as it has a lower boiling point

    • The nitrogen and hydrogen cycles back around, and the process repeats

    • The process produces liquid ammonia 🙂

  • Why 450 degrees?

    • As it is an exothermic reaction, we need a low temperature so the forward reaction is favoured

      • For a higher % yield

    • For a higher rate of reaction, we need a high temperature - energy for more frequent particle collisions (reach activation energy easier)

    • 450 degrees is used as a compromise - lower yield, but higher rate of reaction

      • Any higher would be too costly

  • Why 200 atm?

    • For a high % yield, we want a high pressure so the reaction favours the right

      • Less molecules on right side

    • High pressure also means high rate of reaction

    • High pressure is expensive, and can be dangerous if it goes wrong

    • 200 atmospheres balances it out

NPK fertilisers

  • A fertiliser is a substance that is applied to soil in order to supply plants with nutrients

  • In the past, fertilisers were usually made from animal waste (cow manure) but now they are usually formulated fertilisers (made in factories)

  • A formulation is a mixture that has been designed as a useful product

    • If we make fertilisers by combining chemicals in a specific ration it would be a formulated fertiliser

  • Formulated fertilisers contain nitrogen, phosphorus and potassium

    • NPK - main elements plants need from the soil

    • NPK fertilisers are formulations of various salts containing appropriate ratios of the elements

  • Nitrogen fertilisers

    • Important for plants to make amino acids and hence proteins (essential for growth)

    • Main source is ammonia, made in the Haber process

    • Ammonia can make nitric acid (O2 + H2O + NH3 react) and ammonia salts (reacts with acids)

  • Phosphorus fertilisers

    • Can be mined as phosphate rock

    • Phosphate salts in the rock are insoluble, so can’t be used

    • We react the rock with acids to produce a soluble salt

      • Nitric acid and rock produces phosphoric acid and calcium nitrate

      • Sulfuric acid reaction produces calcium sulfate and calcium phosphate (singe superphosphate)

      • Phosphoric acid and rock produces calcium phosphate (triple superphosphate)

  • Potassium fertiliser

    • Potassium chloride and sulfate can both be mined from the ground and used directly in fertilisers

DONE!!!