Removal of Mercury from Aqueous Streams of Fossil Fuel Power Plants Using Novel Functionalized Nanoporous Sorbents

Abstract

A new class of hybrid nanoporous materials has been developed at the Pacific Northwest National Laboratory for removing toxic heavy metals such as mercury from aqueous and nonaqueous waste streams. These novel materials consist of functional molecules capable of selectively binding mercury (thiol groups) covalently bound (as densely populated monolayers) to the synthetic nanoporous substrates. Tests indicated that this sorbent (Self-Assembled Monolayers on Mesoporous Silica—SAMMS) can achieve mercury loading as high as ∼635 mg/g. The high affinity for Hg adsorption by this material was reflected by Kd values as high as 3.5 × 108 ml/g. Data indicated that SAMMS can adsorb both inorganic and organic forms of mercury. Experimental data indicated that mercury adsorption performance of SAMMS was not significantly affected by pH, ionic strength, presence of other cations (Na, Ca, Cd, Cu, Fe, Ni, Pb, and Zn), and complexing anions (Cl, CN, CO3, SO4, and PO4) in solution. Adsorption kinetics studies indicated that SAMMS adsorbed mercury very rapidly (about 99.9% adsorption occurring within first five minutes). Tests conducted using samples of different aqueous and non-aqueous waste streams have confirmed the exemplary performance characteristics of SAMMS sorbents. Preliminary cost estimates indicated that using SAMMS would result in significant savings in mercury remediation costs as compared to the use of conventional adsorbents such as ion exchange resin and activated carbon.