The ability of humic acids to complex metal ions is well established; however, the chemistry of lead dissolution and structure of the organometallic compound is not well understood. To better understand these problems, experiments were undertaken reacting the common smelter byproducts pbso1, pbco3, and pbo with humic acid as a function of time, ph, and humic acid concentration. Examinations were made of the structure and mechanisms of complexing through the use of model humic acid functional group compounds and infrared spectroscopy. Low-ph conditions and increased humic acid concentrations have been shown to favor pbo, and pbco3 complexing. Lead sulfate complexation was favored by increased ph and humic acid concentration. At low ph values the particulate lead compounds adsorbed humic acid, inhibiting lead dissolution. Active sites of complexation found through infrared analysis were at carboxyl, phenol, phenyl and aliphatic groups, along with formation of metalocyclohexanes and pentanes. Model functional group analysis proved inconclusive for characterization of active complexing sites.
Proc. Western Reg. Symp. on Mining & Mineral Processing Wastes, Berkeley; SME, 1990, PP. 61-67