Let us go to the old time analytical chemistry where we really ran the pH up to get a lot of "stuff" drop out, including many metals.  This is still used as the lime/soda ash softening for large water softening in cities.  For the metal precipitation you may  need to goo well over 10.5, the point where we see free OH radicals forming.   You may well go to a 12 pH, but why spend the money when you may not need the excess to get the job done.  After the pH rise, a pH lowering (a a pH reversal)  to get the pH back down.   The information is not complete.  Metals industry?  If you are trying to separate precious metals, the pH reversal procedure will get most gold, silver, copper and nickel out - just not the final push to get the low levels to avoid some of the discharge requirements.  For the final push I have developed a material to get the final metals precipitated for recovery, and sale.  Most of our customers use it to do the final precipitation for nickel.

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Let us go to the old time analytical chemistry where we really ran the pH up to get a lot of "stuff" drop out, including many metals.  This is still used as the lime/soda ash softening for large water softening in cities.  For the metal precipitation you may  need to goo well over 10.5, the point where we see free OH radicals forming.   You may well go to a 12 pH, but why spend the money when you may not need the excess to get the job done.  After the pH rise, a pH lowering (a a pH reversal)  to get the pH back down.   The information is not complete.  Metals industry?  If you are trying to separate precious metals, the pH reversal procedure will get most gold, silver, copper and nickel out - just not the final push to get the low levels to avoid some of the discharge requirements.  For the final push I have developed a material to get the final metals precipitated for recovery, and sale.  Most of our customers use it to do the final precipitation for nickel.