The particular type of plastic will determine the type of recycling needed. As will the product source.
Most plastics require regrinding or repolymerization, and that takes substantial investment.
Most gold reclamation takes place from either slag piles or from computer circuit boards, and each can create more pollution than it saves. A chemical bath is necessary for gold reclamation from circuit boards and disposal of the spent chemical is a precondition to environmentally sound reclaiming of gold in this fashion. Similarly with silver, whose most common form of reclamation is from photographic film and chemicals used for photo developing and printing. In the case of silver, good manuals are available from photographic trade associations and from Eastman Kodak in Rochester, NY or from Agfa from its manufacturer in Germany. But this literature is huge given the numerous types of plastics and waste streams from which they emanate.