Electrochemical impedance spectroscopy for in situ monitoring of early zeolite formation

Zeolites are crystalline materials with internal pore structures finding widespread application from everyday products like laundry detergents to large scale catalytic and adsorption processes. Up to today however, zeolite formation is not fully understood. Especially the early stages of zeolite formation remain elusive. Although electrochemical impedance spectroscopy (EIS) has already proven to be a versatile tool for characterization of ionic solutions, it has, to the current knowledge of the authors, never been used before for in situ monitoring of zeolite growth. The linear relation between the measured impedance and Si/OH ratio of clear solutions shows that all added silica in taken out of solution and involved in the formation of nano-aggregates. Electrochemical impedance spectroscopy data for clear solutions has been proven to be complementary with ex situ dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) data and moreover allows for quantitative monitoring of nano-aggregate formation, especially in the crucial early steps where traditional methods fail.