Ba and Co Removal from Water by Elution Through Fixed Beds of Phillipsite- and/or Chabazite-Rich Tuffs

Abstract

The possibility of using phillipsite- and chabazite-rich tuffs as cation exchangers in the process of barium and cobalt removal from wastewaters was evaluated. Accordingly, fixed beds of phillipsite-rich Neapolitan yellow tuff grains and of chabazite-rich Orvieto-Bagnoregio ignimbrite grains were prepared. After exchanging them in Na+ form, the relevant breakthrough curves were determined at room temperature, using 100 mg/L solutions for each cation. Some characteristic dynamic parameters were calculated from these curves, such as length of mass transfer zone, ion exchange capacity in dynamic conditions, dynamic selectivity and efficiency of the process, obtaining information on the conditions under which the process should be carried out. The data collected evidenced the good selectivity of both Na-exchanged zeolites for Ba and the poor selectivity for Co, confirming the results previously obtained in equilibrium conditions. The difficulty of eluting barium from the tuff beds during regeneration suggested a profitable employment of Italian phillipsite- and/or chabazite-rich tuffs in discontinuous processes, which are especially useful in the treatment of nuclear power plant wastes, in which the zeolitic sludge generated from Ba removal is usually stabilized–solidified in a cement matrix.