Using Resources

• Potable water is water that is safe to drink
• Finite resources have a limited supply and will eventually run out
• Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials
• Potable water is not ‘pure’ because it contains dissolved substances, athough to be safe it must have sufficiently low levels of dissolved salts and microbes
• Potable water using fresh water:

  • an appropriate source of fresh water is selected (rain provides water with low levels of dissolved substances and this collects in the ground/rivers/lakes)
  • the water is passed through filter beds to remove different sized insoluble solids the water is then sterilised, to kill microbes (sterilising agents include: ozone, UV light or chlorine
• Potable water using sea water:

  • can be done by distillation
  • OR can be done using processes with membranes (e.g. reverse osmosis)
  • BOTH are very expensive
• How quality water is produced:

  • Water is passed through a mesh screen to remove large bits e.g twigs or grit
  • Chemicals are added to make solids and microbes stick together to form sediment and sink
  • There is then anaerobic digestion of sewage sludge
  • The water is then sterilised with chlorine to kill any microbes left.
• it is relatively cheaper and easier to obtain potable water from groundwater and wastewater than salt water, although seawater is a plentiful raw material, so is good for countries with little fresh water
• ways of extracting copper from low-grade ores include phytomining, and bioleaching
• Phytomining uses plants to absorb metal compounds. Plants are harvested and then burned to produce ash that contains metal compounds
• Bioleaching uses bacteria to produce leachate solutions that contain metal compounds
• copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis
• life cycle assessments are carried out to assess the environmental impact of products in stages
• stages of LCA:

  • extracting and processing raw materials
  • manufacturing and packaging
  • use and operation during its lifetime
  • Disposal at the end of its useful life, including transport and distribution at each stage
• Reduction in use, reuse and recycling of materials by end users reduces the use of limited resources, use of energy sources, waste and environmental impacts
• Some products, such as glass bottles, can be reused
• Metals can be recycled by melting and recasting or reforming into different products
• the haber process is used to manufacture ammonia. the raw materials are nitrogen and hydrogen. nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources
• During the Haber Process the purified gases are passed over a catalyst of iron at a high temperature of about 450'C and a high pressure of 200 atm. Some hydrogen and nitrogen cools to form ammonia.
• Haber process: On cooling, the ammonia liquefies and is removed. The remaining nitrogen and hydrogen are removed.
• The haber process is in dynamic equilibrium. The forward and backward reactions keep going once equilibrium is reached.
• Chemical equation for haber process:

  A) N

  B) 3

  C) 3

  
• Haber Process: there are less moles of gas on the product side, meaning that the pressure should be increases to move the equilibrium to the right so more ammonia is produced.
• Haber process: The forwards reaction is exothermic, so a low temperature would favour the forwards reaction meaning more ammonia would be produced.
• The actual conditions used in the haber process are not too low temperature and not too high pressure because low temperature leads to a reaction rate that is too slow and a very high pressure requires too much energy.~
• Compounds of nitrogen, phosphorus and potassium are used as fertilisers to improve agricultural productivity
• Industrial production of NPK can be achieved using a variety of raw materials in several integrated processes
• NPK fertilisers are formulations of various salts containing appropriate percentages of the elements
• ammonia can be used to manufacture ammonium salts and nitric acid
• potassium chloride, potassium sulphate and phosphate rock are obtained by mining, but phosphate rock cannot be used directly as a fertiliser
• phosphate rock is treated with nitric acid or sulphuric acid to produce soluble salts that can be used as NPK fertilisers
• Phosphate rocks are a source of potassium chloride and sulphate which provides potassium
• Since phosphate rock is insoluble in water, it is generally reacted with acid to create useful water-soluble compounds.
• Reacting phosphate rock with nitric acid yields phosphoric acid and calcium nitrate. The phosphoric acid is neutralised with ammonia, producing ammonium phosphate.
• Reacting phosphate rock with sulphuric acid produces a mixture of calcium phosphate and calcium sulphate known as single superphosphate.
• Reacting phosphate rock with phosphoric acid results in calcium phosphate, refered to as triple superphosphate
• composites are made from one material embedded into another. Fibres or fragments of the material (called reinforcements) are surrounded by matrix acting as a binder
• Wood is made from cellulose fibres and lignin
• Fibreglass is made from fibres of glass embedded in plastic
• Carbon fibre is made from polymer matrix with long chains of carbon nanotubes