469103 Removal of Toxic Heavy Metal Cations from Simulated FGD Wastewater Using Functionalized Silica
The silica support was grafted with 3-mercaptopropyltrimethoxysilane and 2-mercaptobenzothiazole. Thermogravimetric Analysis (TGA) and Potentiometric Mass Titrations (PMT) were performed on functionalized silica to determine surface loadings and the point of zero charge (PZC), respectively. The removal of Hg2+ at high concentration (10,000 µg/L) in different matrices was investigated. The effect of FGD matrix ions (Ca2+, Mg2+, Na+, SO42-, Cl-, NO3-) on removal efficiency of Hg2+ is also reported. Simultaneous removal of Hg2+ along with the several other heavy metal cations has been reported at concentrations relevant for the FGD wastewater (500 µg/L each of Cu2+, Cd2+, Hg2+, Tl+, Pb2+, Ni2+, Zn2+). 99% of Hg2+ was captured using these adsorbents for both concentration ranges. The adsorbents were able to selectively capture other heavy metal cations at low concentrations as well. The concentrations of heavy metal ions were determined using the Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS). Preliminary regeneration studies of spent adsorbents were performed using dilute HCl indicating limited regeneration and suggesting their disposal without regeneration.
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