(164e) Release of Gold Nanoparticles from Phytomined Biomass by Enzymatic Digestion

Gold nanoparticles are produced in some plants when soluble gold is present in the growth medium nutrients. Release and recovery of this gold by pyrolysis can sinter the particles, and enzymatic digestion is proposed as an alternative. Brassica juncea grown on soil containing low levels of gold, copper and silver (22?48 mg Au kg-1, 44?45 mg Cu kg-1 and 0?31 mg Ag kg-1 respectively) contained gold at weight concentrations circa 1000 ppm dry matter. 55-60 wt% of the dried plant matter was solubilised by enzymatic digestion, but 50-60% of the gold initially present was lost to solution during the digestion. XANES analysis shows that gold is present in the plant in approximately equal quantities in the metallic (Au0) and oxidized (Au+1) states. The gold lost during digestion is thought to be gold present in the plant in a soluble form (Au+1).