The sulfides can be stabilized in zeolite 4A by protection of inorganic framework. Nevertheless, their stability has not been evaluated with respect to chemical species and locations in zeolite 4A. Due to this reason, we conducted the physicochemical ...
The sulfides can be stabilized in zeolite 4A by protection of inorganic framework. Nevertheless, their stability has not been evaluated with respect to chemical species and locations in zeolite 4A. Due to this reason, we conducted the physicochemical characterization of encapsulated sulfides in zeolite 4A. As a result, the chemical species of encapsulated sulfides were assigned to be S<SUB>6</SUB><SUP>2-</SUP> and S₃<SUP>-</SUP> in α- and β-cage respectively. The sulfides were released by exposure to water and oxygen molecules. Their Raman spectra revealed that S<SUB>6</SUB><SUP>2-</SUP> was released rapidly and S₃<SUP>-</SUP> was released slowly. Eventually, all of encapsulated sulfides completely released regardless of their chemical species and locations in zeolite 4A. This study described that the release behavior of encapsulated sulfides was different with respect to their chemical species and locations in zeolite 4A. These properties suggest new perspectives to be applied to removal of heavy metals.