Surface properties of the mixed oxides of iron and silica

Amorphous synthetic mixed oxides of iron and silicon of varying composition (1.5 M SiO2:0.5 M Fe(OH)3, 0.5 M SiO2:0.5 M Fe(OH)3, 0.5 M SiO2:1.5 M Fe(OH)3) were prepared by sequential precipitation and their surface properties were explored. The Fourior transform infrared (FTIR), X-ray differactometry (XRD), Electron scanning microscopy (SEM), Electron probe micro-analysis (EPM) and Surface area measurement were used to characterize the synthetic mixed oxides. The point of zero charge (PZC) was determined by the salt addition and fast titration techniques. In the present investigation, the focus was on the surface charge, surface dissociation constants and PZC determination from the potentiometric titration data in the temperature range 293–323 K. During this study two common intersection points (CIPs) and two PZCs were observed for the mixed oxides, one corresponding to SiO2 and other to Fe(OH)3.