Separation of Complexed Mercury from Aqueous Wastes Using Self-Assembled Mercaptan on Mesoporous Silica

Separation of Hg(II) from potassium iodide/sulfate wastes was studied using a novel mesoporous silica material containing self-assembled mercaptan groups. The adsorbent, consisting of self-assembled mercaptan on mesoporous silica (SAMMS) developed at Pacific Northwest National Laboratory (PNNL), was characterized as to its specificity, adsorption capacity, and kinetics for separation of mercury from potassium iodide/sulfate solutions. Aqueous speciation calculations indicated that a major fraction (92–99%) of dissolved mercury in the potassium iodide/sulfate wastes solutions existed as HgI2− 4species. The adsorption data showed that the mercury adsorption capacity of SAMMS material increased with decreasing iodide concentrations. The magnitude of calculated free energy of adsorption indicated that mercury adsorption on this adsorbent is typical of soft acid–soft base interactions. High specificity for anionic complexes of Hg(II) by the SAMMS material was confirmed by distribution coefficient measurements....