Role of sulfur atoms in the adsorption of antimony by greigite

In this work, greigite (Fe3S4) and magnetite (Fe3O4) is used as a carrier to study the role of sulfur (S) in the adsorption of antimony (Sb) by greigite. Results show that the synthesized Fe3S4 has stronger adsorption ability to Sb(III)/Sb(V) than its oxide counterpart Fe3O4. The Langmuir maximum adsorption capacities of Fe3S4 to Sb (III) and Sb(V) are 178.87 and 163.52 mg/g, respectively. Change in coordination mode caused by the substitution of S to O is the main reason for the enhancement in Sb(III)/Sb(V) adsorption ability. Sb(III)/Sb(V) adsorb on the Fe-Fe bridge site on (311) plane of Fe3O4, while Fe-S is adsorb at the top site on the (311) plane of Fe3S4; the latter has higher adsorption affinity to Sb than the former. The oxidative conducts of Fe3S4 are only elemental sulfur and lepidocrocite (gamma-FeOOH), and no sulfur-containing compounds are identified. This work is expected to provide new understanding to the role of anion in spinel materials.