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Chemistry Unit 10 - Using Resources - Coggle Diagram

- - - - Human waste - contains harmful bacteria and high levels of nitrogen compounds which can harm aquatic ecosystems.
      - Industrial waste - may contain harmful chemicals such as toxic metal compounds.
      - Agricultural waste - may contain fertilisers or pesticides which can disrupt sensitive ecosystems.
      - Sewage treatment contains the following steps:
        
        1) Screening and grit removal to remove large particles.
        
        2) Sedimentation - allows tiny particles to settle out from still water, which produces sewage sludge and effluent (the liquid which remains on top)
        
        3) The sewage sludge is digested anaerobically by specific bacteria.
        
        4) the effluent is treated with aerobic bacteria to reduce the volume of solid waste.
- - - - 1) Raw materials. All the raw materials we need come from the Earth's crust, atmosphere or oceans, or are due to living organisms. Obtaining the materials have impacts on the environment including:
        
        using up limited resources such as ores and crude oil
        
        damaging habitats through quarrying, mining, or felling trees
      - 2) Manufacture. The manufacturing of a product has an impact on the environment including:
        
        using up the land for factories
        
        the use of machines and people
      - 3) Use. The impact of a product on the environment during its use depends on the type of product. For example, a wooden chair has very little impact, unless it needs cleaning or repair. On the other hand, using a car will have a significant impact.
      - 4) Disposal. The disposal of old products has an impact on the environment, including:
        
        using up land for landfill sites
        
        whether any or all of the product can be recycled or reused
    - - Comparative LCAs can be used to evaluate which of two alternative products will have a lower negative impact on the environment.
    - - It is sometimes easy to work out accurate numerical values for parts of a LCA. For example, we can measure the amount of energy needed to manufacture a product, or the amount of carbon dioxide produced by transporting raw materials. However, some parts of a LCA require judgements, such as the effect of pollutants. This means that completing a LCA is not a totally objective process, and different people might come up with different judgements.
        It is important to consider who has completed the LCA and whether they have any bias. For example, if the LCA is completed by the company which is making and selling a product, they might only include some parts of the genuine environmental impact.
  - - - fewer quarries and mines are needed to extract finite reserves of metal ores
        
        less crude oil needs to be extracted from the crust as raw material for making plastics
        
        less energy is needed for recycling compared to making a new product from natural resources, so the emission of greenhouse gases are reduced.
        
        the amount of waste that is disposed of in landfill is reduced.
    - - the collection and transport of used items needs organization, workers, vehicles and fuel
        
        it can be difficult to sort different metals from one another
        
        the sorted metals may need to be transported to where it can be turned into ingots. The amount of sorting required depends on the purity of the mixture of metals/materials, and also on how pure you need the final recycled metal to be.
  - - - Plants absorb mineral ions through their roots. Phytomining makes use of this:
        
        plants are grown on a low-grade ore
        
        the plants absorb metal ions through their roots and concentrate these ions in their cells
        
        the plants are harvested and burnt
        
        the ash left behind contains metal compounds
      - Phytomining is slow but it:
        
        reduces the need to obtain new ore by mining
        
        conserves limited supplies of high grade ores
        
        reduces the amount of rock waste that must be disposed of after traditional mining
    - - Certain bacteria can break down low-grade ores to produce an acidic solution containing copper ions. The solution is called a leachate and the process is called bioleaching.
        Bioleaching does not need high temperatures but it produces toxic substances, including sulfuric acid, which damage the environment.
      - Processing the metal compounds
        
        Iron is more reactive than copper. It can displace copper from the leachate. For example:
        iron + copper sulfate → iron(II) sulfate + copper
        Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
        Since iron is cheaper than copper, the use of scrap iron is a cost-effective way to produce copper from the leachate.
        Alternatively, the copper compounds can be dissolved and the solution electrolysed to produce copper metal.
- - - - Electroplating
        
        Involves using electrolysis to put a thin metal on the object.
        
        The cathode is the iron or steel object.
        
        The anode is the plating metal.
        
        The electrolyte contains ions of the planting metal.
      - Removing substances that cause rusting
        
        Remove substances that cause rusting. Store metal in atmosphere of unreactive nitrogen or argon. You can also store metal in a desiccant which is a substance that absorbs water vapor so it keeps the metal dry.
      - Physical barriers to oxygen and water
        
        You can use physical barriers to oxygen and water. These include painting, oiling and greasing and coating metal with plastic
      - Galvanizing
        
        When iron is coated in zinc, the process is called galvanisation. The zinc layer stops oxygen and water reaching the iron. Zinc is more reactive than iron, so it also acts as a sacrificial metal. This protection works, even if the zinc layer is scratched.