Raman Spectroscopic Characteristics of Zeolite Group Minerals

Abstract

In this work, Raman spectroscopic experiments are conducted on zeolites, including a total of 33 varieties and seven groups with different secondary structural frameworks, for which characteristic vibration modes are studied. Most of the zeolites show prominent Raman peaks in the spectral range between 200–1200 cm−1. Different groups of zeolites can be recognized by differences in the wavenumbers of the T-O-T (T = Si and Al, O = oxygen) modes in the range 379–538 cm−1, the M-O (M = metal,) modes in the range 250–360 cm−1 and the T-O bending modes in the range 530–575 cm−1. All zeolites show characteristic Raman peaks in the range 379–529 cm−1, except for natrolite group (fibrous) zeolites, which are characterized by T-O-T modes in the 433–447 cm−1 range and T-O bending modes in the 528–538 cm−1 range. The analcime group (with singly connected four-ring chains) zeolites show T-O-T modes in the 379–392 cm−1 and 475–497 cm−1 ranges. The gismondine group (with doubly connected four-ring chains) zeolites have T-O-T modes in the 391–432 cm−1 and 463–497 cm−1 ranges. The chabazite group (with a six-cyclic ring) zeolites are characterized by M-O modes in the 320–340 cm−1 range and T-O-T modes in the 477–509 cm−1 range. The Raman modes of mordenite group zeolites (397–410 cm−1 and 470–529 cm−1) overlap with those of heulandite group zeolites (402–416 cm−1 and 480–500 cm−1). Moreover, the mordenite group has a characteristic peak in the 502–529 cm−1 range, and an additional peak in the 800–965 cm−1 range. Another recognizable peak for the heulandite group is in the 612–620 cm−1 range. The unknown zeolites (cowlesite) have unique characteristic peaks at 534 cm−1, which can aid in the verification of their identity.