C14 Flashcards
What is water distillation?
A seperation technique which involves a solution (salt water) being heated so that the solvent evaporates before being cooled to form a pure liquid (water).
What is desalination?
The process by which salt is removed from seawater in order to make drinking water
What are the 2 main methods of desalination?
Reverse osmosis and distillation
What is another word for distillation?
Thermal desalination
Why is desalination most commonly used in the Middle East?
- many of the countries are quite wealthy
- rainfall is low
- many of the countries have coastlines
What is reverse osmosis?
Reverse Osmosis is a method that is used to remove a large quantity of contaminants from water by pushing the water under pressure through a semi-permeable membrane.
Advantages of thermal desalination
- improves water quality
- kills harmful microbes in the water
- removes all impurities
Disadvantages of distillation
- heating uses a lot of energy
- energy may come from non-renewable sources
- expensive
Advantages of reverse osmosis
- no heating involved
- less energy required
Disadvantages of reverse osmosis
- need to pressurise water
- corrosion of pumps due to salty water
What are the 4 steps involved in treating waste water?
Screening, Primary Treatment, Secondary Treatment, Final Treatment
What is screening?
The waste water is passed through a metal grid which removes large objects such as branches
What is primary treatment?
Solids are allowed to settle out from the mixture, where large paddles push it to the centre to be piped off for further treatment
What happens during primary treatment?
Solids are allowed to settle out from the mixture, where large paddles push it to the centre to be piped off for further treatment
What happens during secondary treatment?
Bacteria are released in the liquid where they aerobically break down harmful micro-organisms and any other organic material. Air is bubbled through the liquid.
What happens during final treatment?
The bacteria are allowed to settle and are recycled or disposed with the solids
In waste water treatment, what happens to the solids (sludge)?
It is anaerobically digested by bacteria and then used as fertiliser/fuel or sent to landfill
What are the 2 main methods used to obtain copper from its ore?
- Smelting
- Sulfuric acid used to produce coper sulfate before extracting copper metal
What process is used to purify the impure copper extracted by smelting?
Electrolysis
How can copper be extracted from copper sulfate solution?
By adding iron which will displace copper from the solution
What is malachite?
A type of copper ore
What method is used 80% of the time to extract copper from malachite?
Smelting
Why is smelting bad?
Requires a lot of energy and emits Co2 and So4
What is phytomining?
Where plants are grown on low-grade copper ore which absorb copper ions. They are burnt; and the ash is reacted with sulphuric acid to form a leachate of copper sulphate, from which copper is obtained by displacement or electrolysis
What is bioleaching?
Where bacteria feed on low grade copper ore and produce a solution of copper ions called the leachate. Copper can be obtained from this by displacement or electrolysis
Why can copper be ocassionally found native?
Copper is an unreactive metal – it reacts only slowly with the atmosphere.
Why are methods like phytomining becoming increasingly popular?
It is potentially the least harmful method because it uses naturally occurring organisms and preserves the environment in a more natural state.
What is a life cycle assessment?
A method to analyse the environmental impact and the water and energy usage of a product over its lifetime
What are the 5 stages in an LCA?
RAW MATERIAL - manufacturing - USE/REUSE - maintenance - recycle
Why is recycling aluminium important?
It saves 95% of energy compared to producing it
Why might LCA’s be totally objective?
Assigning the numerical values of environmental aspects is subjective as it requires judgements such as the effect of pollutants.
Why are LCA’s carried out on new products?
LCA is carried out on new products to assess the environmental impact of the products, process or services and if it is sustainable.
What do LCA’s not take into account when comparing products?
Differences in cost or performance
What is the aim of “reduce, reuse and recycle” campaigns?
- to reduce our use of energy
- to limit the waste we produce
- to limit the use of finite resources
Why is recycling copper more difficult than other metals?
It is usually an alloy and therefore purification is required
Why is recycling iron + steel important?
Because no fossil fuels need to be burned and 50% less energy is used compared to production.
What consumes most of the energy in the production of steel from iron ore?
Burning fossil fuels such as natural gas to heat the air entering a blast furnace
What do we call products that don’t affect the atmospheric carbon dioxide concentration?
Carbon-neutral
What toxic gas is produced when sulfur is burned?
Sulfur dioxide
Which source of potable water is the most expensive to treat?
Sea/salt water
Which source of potable water is the easiest to treat?
Fresh water
3 sources that potable water can be obtained from
- fresh water
- seawater
- waste water
Main sources of waste water
- Domestic
- Industrial
- Agriculture
Which product of sewage sedimentation is anaerobically digested by bacteria?
sludge
If materials are not reused or recycled, where do they accumulate?
If materials are not reused or recycled, where do they accumulate?
What are the steps involved in recycling glass?
- sort
- crush
- melt
- reshape
What stages are involved in the processing of glass for it to be converted into other glass products?
- the colour is sorted by colour and chemical
- glass crushed in small pieces
- glass melted
- reshaped in new product
Disadvatanges of bioleaching
- Slow
Why are copper-rich ores in short supply?
Due to historical overexploitation
What sources can copper be extracted from?
- copper rich ores
- low grade ores
- contaminated land
What do we call LCAs that choose to ignore certain environmental impacts of a product?
Selective LCA
Give an example of a factor that is not used to sort glass products for recycling?
Size
Suggest why fluorine is added to drinking water
- Improves dental health
- Prevents tooth decay
Why can’t we release our waste water directly into the environment?
Waste water can contain toxic chemicals, harmful microorganisms and other organic matter. All these things can cause pollutionand affect plants and animals, including humans.
What % of the Earth’s water is freshwater?
3%
What name is given to resources which may run out one day if not managed carefully?
Finite resources
Examples of finite resources
- Metals
- Plastics
- Coal
What is a finite resource?
Finite resources are those that are being used up at a faster rate than they can be replaecd
What is sustainable development?
Development that meets the needs of current generations without comprimising the ability of future generations to meet their own needs
What is an alternative synthetic product to wool?
Acrylic fibre / polypropene
What is an alternative synthetic product to silk?
nylon
What is an alternative synthetic product to wood?
PVC, MDF
What is an alternative synthetic product to cotton?
Polyester
What is order of magnitude?
An order of magnitude is a division or multiplication by 10
Why should estimations calculated be expressed as order of magnitudes?
- There are uncertainties involved in the calculations
- Predictions do not take into account recycling of resources
What is potable water?
Water is not necessarily pure, but safe to drink
What 3 sterlising agents are used to clean water?
- UV light
- Ozone (O3)
- Chlorine
