Reusing electrolytic capacitors?
You can always re-use components like electrolytic capacitors but there are some considerations to take into account.

It is always ok to use a capacitor rated at a higher voltage than the voltage in the applied circuit. I.E. When typically a 16V or 25V rated capacitor may be specified for a 12V application reuse of a 35V rated capacitor is fine whilst a 10V rated capacitor is not.
The leads on re-used capacitors are typically very short and are only really usable in applications where you have an actual circuit board that has holes spaced properly for the particular capacitor that wants to be re-used.
Disassembly of electrolytic capacitors from old circuit boards where the leads were bent over on the solder side can be problematic in that it takes a lot of extra heat in desoldering and undue stress on the leads going into the body of the capacitor. Both issues can create permanent degradation and damage to the component.
Depending upon application re-used capacitors can be a great deal to keep cost down. However it is never wise to use re-used components in equipment that you intend to sell as new when the complete provenance of components is not known.