Heavy metal adsorption on iron oxide and iron oxide-coated silica ...

40morphology. Samples were fixed on the aluminum sample holder with double-stickconductive carbon substrate.4.5.5 Surface Area, Porosity, and Pore Size DistributionSurface area (BET method) was measured with a NOVA 3000 series unit as well as bythe Gas Technology Institute (GTI, 2002). Porosity (mercury porosimetry) and pore sizedistribution (mercury porosimetry) analyses were performed by GTI (2002).4.5.6 Fourier Transform Infrared Spectroscopy (FTIR)To study the interfacial bonding mechanism between goethite and silica, Fouriertransform infrared (FTIR) spectra were obtained on an ATI Mattson Research Series 1FTIR Spectrometer. Goethite, silica, and goethite-coated silica samples were dispersedhomogeneously in KBr matrices and pressed into discs. Five hundred scans of resolution4 cm-1 were averaged to improve signal to noise ratio. The instrument was continuallypurged with dry air. Spectra were obtained over the range of 400-4000 cm -1 .4.5.7 Surface Charge DistributionSurface charge distribution varies depending on the degree of hydration, contamination ofthe surface by other ions, and method of determination. The point of zero charge (pHpzc)of a system of any complexity is the condition of no net charge on the surface (Parks,1967; Westall et al. 1976); others may prefer to designate this the common intersectionpoint, pHcip, for mixed systems. The PZC can be measured from a wide variety ofexperiments in which pH is a master variable (Parks, 1967). Methods used to determine