Physicochemical characterization of encapsulated sulfides in zeolite 4A

Sulfides encapsulated in zeolite 4A have been known to be stabilized by protection of the inorganic framework in spite of the possibility that they could be decomposed and eventually released into environment. This study focused on their release properties along with identification of the chemical species and location. At an optimized treatment condition, zeolite 4A encapsulated sulfides to be the total sulfur content up to a weight % of 10.61. Major encapsulated sulfides were identified to be S₆²⁻ in α-cage and S₃^•− in β-cage, respectively. Extraction with deionized water revealed that 77% of the encapsulated sulfides was rapidly released within 3 days while the rest was gradually and completely released within 3 weeks. It was suggested in zeolite 4A that S₆²⁻ in α-cage was released rapidly whereas S₃^•− in β-cage slowly. This release behavior of encapsulated sulfides provides a new strategy to explore their potentials for advanced applications.