Next, the selectivity of poly-1 and poly-2 in gold sorption was assessed using leach solutions containing multiple metal salts derived from gold, aluminum, iron, copper, zinc, and tin (all prepared at 100 ppm). Silver was also included in this leach solution, but precipitated on the addition of the TCCA and NaBr, which was expected due to the low solubility of silver halides. For this reason, the sorption of silver using the polysulfides was not assessed further. However, the selectivity of both poly-1 and poly-2 for gold was exquisite: both sorbents removed >95% of the gold from solutions and the concentration of all other metals did not change (Fig ). In these sorption experiments, 200 mg of either sorbent was added to 4.0 mL of the leach solution and equilibrated with mixing for 20 hours. This selectivity motivated application of this gold sorption method to complex leach solutions derived from electronic waste, mixed metal waste, and ore concentrates. Gold recovery from poly-1-Au and poly-2-Au. After leaching and gold sorption, the gold must be separated from the polymer and purified. A simple and direct method is pyrolysis. For example, poly-1-Au could be heated in a crucible in a 1200 ºC furnace to pyrolyze the polymer with concomitant reduction of the gold. The gold remains in the crucible for recovery. This method is robust and simple, but requires precautions to contain emissions, as sulfur dioxide and other sulfur-containing products will be produced. One simple measure for scrubbing is to use a wet scrubber made from TCCA, which converts the sulfurcontaining off gases to sulfate (Fig. ). In this way, the leaching solution can be used for leaching and scrubbing. Despite these measures, it is still undesirable to destroy the polymer sorbent. For this reason, poly-2 was developed so that it can be depolymerized, converted back into monomer, and separated from the gold. In extending this process to poly-2-Au, the gold could be readily separated in excellent recovery (98%) while monomer 2 was regenerated and isolated in 61% yield (Fig. ). It should be noted that the yields of the monomer recovery from poly-2-Au are lower than the depolymerization of poly-2, because poly-2 is partially degraded when it quenches the leach solution.