Treatment of industrial wastewater using zeolitite and sepiolite, natural microporous materials

This work investigates the ability of natural microporous materials, such as a zeolite-rich tuff(zeolitite) and a modulated phyllosilicate (sepiolite), to remove heavy-metal ions from simulated inorganic polluted industrial wastewater. Fixed beds of sepiolite and zeolitite were percolated by a solution of Co2+, Cu2+, Zn2+, Cd2+, and Pb2+ (concentration of each cation, 2 x 10(-3) N; total concentration, 10(-2) N) and were regenerated with a 2 x 10(-3) N Na+ solution. The order of decreasing affinity was, for sepiolite: Cu2+ > Zn2+ > Cd2+ > Pb2+ congruent to Co2+, and, for zeolitite: Pb2+ much greater than Cd2+ > Cu2+ > Zn2+ > Co2+. After regeneration with Na+ solution, a fraction of the retained heavy metals was quickly released by the beds as follows: sepiolite, Co2+ congruent to Pb2+ > Cd2+ > Zn2+ > Cu2+; zeolitite, Cd2+ > Cu2+ congruent to Zn2+ > Co2+, Pb2+, XRD and DTA-TGA analyses examined structural changes in the natural and final materials.