سهیلا سادات هاشمی

The aim of this study was to investigate the zinc (Zn) adsorption by vermiculite clay of Golgohar mine and sepiolite of Fariman mine and to investigate their structural and mechanical changes. Four samples included (vermiculite clay, sandy soil + 2% vermiculite clay, sepiolite clay and sandy soil + 2% sepiolite clay) were treated with Zn(NO3)2 solutions with five concentrations (0.0001, 0.0005, 0.005, 0.01 and 0.05 M) for adsorption isotherm analysis and incubated for one and three months. After incubation experiments, X-ray diffraction peaks and scanning electron microscop (SEM) images were provided for samples. Results indicated that with increasing Zn concentrations and incubation time, the amount of Zn adsorption in clays increased. The vermiculite clay had more effect on Zn adsorption at higher Zn concentrations than sepiolite clay due to higher cation exchange capacity. Also, the decrease in the intensity of the X-ray peaks indicates that the interlayer of the clay plates are spaced apart and as a result, the structures have changed during the absorption of Zn. Based on result of SEM images, sepiolite structure has been transformed from acicular to a cluster form. In addition, with increasing in the contaminant concentration, the cohesion value was increased and led to an increase of shear strength. It is recommended that vermiculite clay of Golgohar mine be used as a safe natural adsorbent of Zn metal in the environment due to its higher adsorption value and soil shear strength.