Homebrew PCBs

Stefan Trethan wrote:
>>NaHCO3  - baking soda
>>NaCL-  from HCL and NaHCO3 reaction
>>Cu - copper
>>
>>
>>and drop off at your local hazardous waste facility.
>>
>>
>>Is my chemistry correct ?
>>
> 
> 
> you probably have no metallic copper, more like CuCl2 and CuCl....
> 
> the acid is definitely no problem, neutralize with anything...
> 
> The H2O2 degrades to pure water, the oxygen goes in the air in a matter of 
> hours/days.
> 
> As we have established before the copper compounds are the problem, 
> possibly killing
> the bacteria in the wastewater plant.
> 
> 
> Best idea in my opinion is neutralize, and then let evaporate without 
> danger.
> 
> Can lime be used for neutralizing it?
> slaked lime like you use for construction i mean.....
> 
> ST

Yep, I've used slaked lime a few times. its mostly calcium hydroxide 
Ca(OH)2. You get CaCl2 which is soluble. Builders lime is 1/1000th cost of 
bicarbonate soda from a food store.

If you want to remove copper then easiest approach is throw in some scrap 
iron and/or aluminum while the etchant is still slightly acidic. The copper 
precipitates as copper metal and aluminium/iron goes into solution.
After about 1 week the solution will be crystal clear with brown copper 
sludge on the bottom. Syphon out most of the liquid being careful not to 
disturb the sediment, neutralize the remaining sludge and leave few days to 
dry to a dark crust. Works well with spent ammonium persulfate etchant and 
CuCl. But I havn't tried treating FeCl3 etchant this way.

Adam