MECHANISM OF REDUCTIVE STRIPPING-PRECIPITATION OF ULTRAFINE AU PARTICLES FROM AU(III)-LOADED MIBK

Experimental studies were conducted to elucidate a possible mechanism for the reductive stripping-precipitation of ultrafine particulates of Au from Au(III)-loaded MIBK. The principal findings are as follows: ( 1) Under the irradiation of day light, the yellow color of Au (III)-lo aded MIBK fades gradually at the same time, the equilibrium potential shifts towards the noble direction, suggesting the decomposition of (H +MIBKAuCl4-)o into (H+ MIBKAuCl2(OH)2-)o or (H+MIBKAuCl2-)o via a phot ochemical route. (2) Water acts as a reductant of Au(III)-loaded MIBK under the catalytic action of a small amount of a suitable reducing ag ent to precipitate ultrafine particulates of Au. (3) The role of H+ or Cl- on the reductive stripping-precipitation reactions was also studi ed. The rate of reductive stripping-precipitation of Au increases with the increase in temperature under the presence of NaCl, exhibiting an activation energy of 43.7 kJ.mol-1.