Laboratory and Numerical Study into Retention of the Heavy Metal Pollutant Lead by Nanoclay Cloisite Na+

In spite of the numerous studies published on soil-pollutant interaction in recent years, no considerable research has been conducted on the interaction between heavy metal pollutants and nanoclays. Lead is a common heavy metal pollutant in geotechnical and environmental projects. Moreover, although researchers have introduced equations for retention of metal pollutants in soils, no research has been conducted on heavy metal retention capability of nanoclays and the effect of carbonate on equations related to retention capability. Therefore, this study intended to examine the geotechnical-environmental behavior of nanoclays and carbonate-modified nanoclays in terms of capability to adsorb the heavy metal pollutant lead and to propose equations for pollutant retention by nanoclays. To achieve this objective a series of environmental and geotechnical experiments were conducted to analyze the mechanism of retaining the heavy metal pollutant lead by examining pH variations, capability of pollutant retention, and through evaluating X-ray diffraction (XRD). Moreover, a series of linear and non-linear equations was used to study the capability of nanoclay Cloisite Na+ in retaining the heavy metal pollutant lead at various ambient pH values and different carbonate contents of the specimens.
Findings: Results showed that carbonate content was an effective factor in pollutant retention and had to be included in the numerical equations. Inclusion of the pH variation parameter in the equations increased the correlation coefficient in the proposed equations.
Discussion and Counclusion: The proposed numerical equations can be a proper substitute for laboratory methods, and also can be used in designing landfill sites