Infrared spectroscopy of NH4+-bearing and saturated clay minerals: A review of the study of layer charge

Infrared (IR) spectroscopy study of the layer charge of clay minerals demonstrates that the υ4 NH4+ band, assigned to the deformation vibrations of the NH4+ ion can be used to evaluate the charge characteristics of NH4+-bearing clay minerals. Total accessible charge, equivalent to cation exchange capacity (CEC), as well as tetrahedral and octahedral charge distribution in both dioctahedral and trioctahedral smectites are determined by quantifying the υ4 NH4+ band before and after lithium treatment. When using the KBr pressed pellets technique, the position and the shape of the υ4 NH4+ bands can distinguish exchangeable and fixed NH4+ in clay minerals.