Removal of heavy metals from waste waters by vermiculites

The sorbent behaviour of (natural and exfoliated) vermiculite minerals was studied with respect to metal cations (Ni, Cu, Cd) commonly present in waste waters of the metal finishing industry. The Langmuir model was found to describe the sorption processes well, showing the maximum sorption capacities of natural vermiculite to be high enough (b(Cu) = 26.0 mg g(-1); b(Cd) = 23.5 mg g(-1); b(Ni) = 19.3 mg g(-1)) for its use in metal waste water purification systems to be feasible. The column studies performed with this mineral show that a large volume of metal solutions with similar concentrations to those usually present in waste waters can be purified down to the legal limit of waste. These positive results are ratified when real waste waters are used at lab-scale as well as at semi-industrial scale, validating the use of this mineral as a cost-effective treatment to purify such waste waters.