Aminoacid as a factor controlling distribution of heavy metals in soils and groundwater

The aim of this work is to evaluate the stability of the smectite-aminoacid-Cu2+ system in order to predict the capacity of these minerals to adsorb and to retain pollutants as heavy metals and organics. Two smectites with different crystal chemistry were previously treated with Cu2+ solution in order to obtain Cu2+-exchanged smectite. Afterwards, each natural and Cu2+-treated smectite was suspended and stirred overnight, in 100 ml of 0.2M cysteine or glycine aqueous solutions. The results indicate that: i) glycine and cysteine can be sorbed by natural anti Cu2+-exchanged smectites; ii) the aminoacid content depends on clay mineral chemistry and from the aminoacid type; iii) when treated with acidified distilled water (pH = 5), natural and Cu2+-smectites release glycine almost completely while strongly retain cysteine; iv) the thermal and the X-ray diffraction analyses confirm that cysteine is strongly retained by Cu2+-exchanged samples.