V3+, Cr3+ and Mn2+ uptake by sepiolite and sedimentary zeolites.

The aim of this study was to investigate the potential usefulness of minerals in industrial waste-water treatment. Fixed beds, one of a zeolite-rich rock (zeolitite) and the other of a phyllosilicate (sepiolite), were treated with a soln. of heavy-metal cations (V3+, Cr3+, Mn2+) in equal concns. of 3.33×10-3 N. To ascertain the different rates heavy metal uptake and subsequent release, the beds were eluted with a Na+ soln. (3.33 × 10-3 N) and the cations (V3+, Cr3+, Mn2+, Na+, Mg2+, K+, Ca2+) in soln. measured. At first, the heavy-metal cation level in the effluent was consistently low for both beds; thereafter, it was obsd. that: (i) the ability of sepiolite to retain V3+ and Cr3+ is greater than that of zeolitite, whereas zeolitite reveals greater affinity for Mn2+; (ii) the max. heavy metal release occurs in the initial stage and slows down as the amt. of influent soln. increases; (iii) the residue of heavy metals in the beds after elution does not significantly affect the mineral structure.