AN ANION ADSORBENT OF THE ANTI-HOFMEISTER TYPE BASED ON COBALT(III)-LOADED CHELATING RESINS CONTAINING 1,4,8,11-TETRAAZACYCLOTETRADECANE-5,7-DIONE

An anion adsorbent was developed based on a cobalt(III)-loaded chelating resin containing 1,4,8,11-tetraazacyclotetradecane-5,7-dione. Batchwise adsorption study has revealed that the adsorbent exhibits an anti-Hofmeister anion selectivity sequence (OH->SCN->NO2-) and that it takes up thiocyanate preferentially in the presence of excess perchlorate as well. Column-mode study has also clarified that the adsorbent takes up thiocyanate preferentially even in the presence of tenfold excess perchlorate. The adsorbed thiocyanate is rapidly and quantitatively eluted with 0.2 M sodium hydroxide, unlike to the case of a conventional anion exchange resin (Bio-Rad AG 1-X4) column. In addition, the adsorbent was able to be regenerated with hydrochloric acid solution for repeated use. During repeated use of the adsorbent for a half year, no loss of the loaded cobalt(III) was observed.