Removal of heavy metal ions from wastewaters using natural clays

A bentonite sample from the Petresti deposit, Cluj County (Romania), was used to remove heavy-metal ions (Cd2+, Pb2+, Cr3+) from wastewaters. A representative sample of bentonite (P) was characterized using the Brunauer-Emmett-Teller (BET) method, wet chemical analyses, X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The bentonite deposit from Petresti is present at the contact between Upper Jurassic limestones and basaltic andesites with subordinate basalt bodies. These rocks are composed of clay minerals (mainly smectite), with opal, quartz.. feldspar and mica/illite as minor phases. The bentonite sample was used in powdered form (d < 0.2 mm) without any chemical treatment. The influence of the working regime, static and dynamic, oil the process efficiency was Studied using monocomponent synthetic wastewaters containing Cd, Pb and Cr ions. The bentonite sample proved to be efficient for the removal of these heavy-metal ions: removal efficiencies up to 100% (lead removal) were achieved.