Extraction of Heavy Metals by Mercaptans Attached to Silica Gel by a Corkscrew Mechanism

Saturated, straight chain mercaptans were attached to silica gel and used as coordinating agents for removal of cadmium(II), copper(II), lead(II), and nickel(II) ions from standard solutions. It is believed that the mercaptans become wedged in the silica pores, but are available for reaction. Four thiols were used, viz., 1-hexanethiol, 1-dodecanethiol, 1-hexadecanethiol, and 1-octadecanethiol. Standard solutions of metals (1.57 mM) were stirred with the supported mercaptans for two hours, and at 25 degrees C, and the sample supernatants were analyzed using atomic absorption spectrometry. At pH = 8, the percent removal was 99 (Cd), 91.5 (Cu), 80.8 (Pb), and 97 (Ni). It was possible to acidify the metal-containing solids, and regenerate the supported chelating agents.