Hydroxide solutions of metals, metals are soluble at varying pH ranges, and can become insoluble as you raise the PH more towards basic (opposite of acid), these metal hydroxides are normally fluffy voluminous and often can be hard to settle, different metals forming hydroxides will precipitate out of solution at differing PH ranges, there are charts and graphs which show these ranges.
Some metals can redissolve as you raise the pH of the solution. Actually quite a few metals, like lead or even gold, with an excess of hydroxides or base, these metal hydroxides are called Amphoteric, some of the metals which are Amphoteric are chromium, gallium, copper, antimony, bismuth, indium, silicon, titanium, vanadium, Iron, cobalt, germanium, zirconium, silver, tin, gold, aluminum, lead, beryllium, zinc, magnesium.
Lead for example is an amphoteric metal, as we know lead (II) hydroxide forms a white precipitant Pb(OH)2 (s), but with an addition of excess hydroxide ions we can dissolve this lead hydroxide precipitant back into a colorless solution of tetra-hydroxo-lead (II) complex Pb(OH)4 (aq), and we can also precipitate it back out of solution with careful additions of acid or acidic solutions, and then the precipitant can dissolve again with more acid added. (Depending on the acid or acidic solution added, as we know lead chloride and lead sulfates are normally insoluble so the acid of these salts would not work in this description or example of the atmospheric metal of lead).
I have used caustic to remove memory chips from trimmed memory; this also helped to remove the green solder mask exposing the copper traces, which were on the outer layers of the memory sticks.
The very saturated strong hydroxide solution worked slowly even with the bucket heating in the sun.
I would then use my acid waste solutions (in varying states of treatment for disposal) to treat the hydroxide waste, and to use as wash-water for the procedure, from the almost clear waste salt water solutions getting very close to neutral pH, this waste salt water solution which only needed slight adjustment of raising pH, this helps to treat my acidic waste and the hydroxide waste at the same time, basically making your waste useful.
The waste salt-water can be used in washing and rinsing, the acidic chlorides can be used where you need the acidic solution and the chloride content (these waste acids can also be used in the metal displacement reactions we get from the reactivity series of metals).
Your hydroxide waste can treat your acidic waste...
I would also use old copper or iron acidic waste solutions where needed quite a bit of pH adjustment, to treat the hydroxide precipitants, or hydroxide waste solution.
The hydroxide solution from memory chips was dumped into another bucket. Keeping the chips and memory cards in the original bucket, pouring through a plastic strainer to catch any chips that got past the tool I was using to try and keep the circuit boards and chips in the original bucket as I dumped out the solution, these hydroxides were allowed to settle for several days the clear hydroxide solution was decanted and put into HDPE containers to use as hydroxide solution later (to depopulate more or to treat waste solutions with. likely mostly iron hydroxides as far as I could tell...), then I used waste chloride salt water solution to rinse the circuit boards and chips (this helped to bring them back towards neutral) before a clean water wash, the rinses chloride (waste salt water) helped to rinse off lead, solder mask and so on from the chips and circuit boards, this chloride rinse was then added to the second bucket with of the precipitant lead hydroxide and solder mask which helped in changing its pH closer to neutral, and help in forming lead chlorides which helped to settle the lead better (and making the lead chloride easier to separate later in boiling water), it still contained solder mask and a very slight bit of gold from the gold plating of the memory card copper traces and other metal hydroxides.
For more adjustments of pH for the hydroxide powders I use old copper II chloride or iron chloride waste solutions, giving me insoluble lead chloride, which when boiled in water (or the salt water chloride waste solutions), dissolves the lead, and this dissolved lead chloride can be separated to cooling jars, allowed to cool to give a more pure precipitant of lead chloride crystals which go to my lead collection jars (I keep my lead for later uses, these salts can be converted back to lead metal, lead oxides...).
The traces of gold plated on the memory circuit board traces was most likely not worth the trouble but I try to get the squeal from this pig, these and the other solder-mask were neutralized, washed well with water to try and remove soluble chlorides, then added to other material destined to be incinerated for traces of values.
The memory chips did seem to have quite a bit of iron from the legs of the chips I suspected, the hydroxide solution removed and saved seemed of high iron content, by using this relatively clear to rusty hydroxide I can treat my other acidic waste, destined as waste solutions.
The memory chips added to a bucket which waits for rainy season where I can use Pyrolysis on them (after forest fire season is over) speaking of that, there is a forest fire 8 miles from my home now, it has been so smoky here for the last eight days it has been hard to breath, the fire has been depositing ash on my vehicles and property, heck it my get to my chips before I can if the fire fighters can not get control of it.
I got most of the copper from the outer surfaces of the memory cards using some old copper II chloride solutions, but much of the copper seems to be on inner traces between layer of the fiberglass, even some nice layers of copper ground plane, between those layers of fiberglass.
The memory fingers were treated to get the gold that was my main goal anyway with this project,
If I was just going to depopulate the memory chips it is much easier just to cut them off the cards
.
http://www.google.com/search?gs_rn=23&gs_ri=psy-ab&pq=amphoteric&cp=17&gs_id=43&xhr=t&q=amphoteric+metals&bav=on.2,or.r_qf.&biw=1024&bih=614&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=Yiv7UY77DsTXigKusIDAAg#um=1&hl=en&tbm=isch&sa=1&q=metal+Hydroxide+precipitation+chart&oq=metal+Hydroxide+precipitation+chart&gs_l=img.3...2899.30488.0.31117.35.21.0.14.14.0.148.2247.9j12.21.0....0...1c.1.23.img..8.27.1704.4jfushMkJSI&bav=on.2,or.r_qf.&bvm=bv.50165853,d.cGE&fp=6aa267eef08cee78&biw=1024&bih=614
https://en.wikipedia.org/wiki/Amphoterism
http://www.google.com/#gs_rn=23&gs_ri=psy-ab&pq=amphoteric&cp=17&gs_id=43&xhr=t&q=Amphoteric+metals&es_nrs=true&pf=p&sclient=psy-ab&oq=Amphoteric+metals&gs_l=&pbx=1&bav=on.2,or.r_qf.&fp=6aa267eef08cee78&biw=1024&bih=614
