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Green Criteria for Metals Removal

  1. Large molar /weight excesses of reagents should be avoided if possible.
  2. The green hierarchy for metals
    1. Simple inorganic reagents/extraction solutions
    2. Organic reagents like amines, sulfides
    3. Activated carbons
    4. Organophosphines
    5. Functionalised scavenger resins/polymers
  3. Techniques that require large volumes of solvent(s) should be avoided. When choosing solid scavengers, excessive absorption of the product should be avoided if possible.
  4. For precious metals, the recovery methodology should generate a waste suitable for recycling and recovering the metal.
  5. Generation of large volumes of liquid waste containing very dilute concentration of precious metals should be avoided.
  6. Oxidative methods should use low impact oxidants like air, hydrogen peroxide, bleach etc.