Sepiolite as an efficient adsorbent for ethylene gas

The ability of Na⁺-, Li⁺-, K⁺-, Ca²⁺- and Mg²⁺-exchanged sepiolites and acid-activated sepiolites to remove ethylene from storage environments was examined. The sepiolite from Sivrihisar deposit, Turkey, was treated with 1.0 M NaNO₃, LiNO₃, KNO₃, Ca(NO₃)₂, Mg(NO₃)₂, HNO₃ and H₂SO₄ solutions at 90°C for 4 h. The mineralogical, chemical and textural properties of the materials were examined using X-ray diffraction, X-ray fluorescence, cation-exchange capacity and nitrogen gas adsorption analyses. The main mineral phase present in the materials was sepiolite, with minor dolomite, and traces of quartz and feldspar minerals and amorphous matter. Adsorption isotherms of ethylene at 273 K were measured on sepiolite samples over a pressure range of 0-100 kPa. As a result of partial blockage of the sepiolite channels, the ethylene adsorption capacity on cation-exchanged sepiolite forms (0.376-0.907 mmol g^-1) was less than that of acid-activated sepiolite forms (1.279 and 1.308 mmol g^-1). The ethylene adsorption capacities of the sepiolite samples were compared with those of other clay-based materials (0.167-1.817 mmol g^-1) reported in previous studies of ethylene removal.