When treating wastewaters with two or more common metals with different optimal pH levels for precipitation, which approach should be used?

When treating wastewaters with two or more common metals with different optimal pH levels for precipitation, which approach should be used?

• A. Precipitation of lowest optimal pH metal followed by next higher pH metal
• B. Simultaneous precipitation of all metals at the highest pH
• C. Precipitate the metal with the highest pH first
• D. Precipitate metals in order of increasing atomic number

Answer: (A)