Investigation of Nickel Retention Kinetics of Selected Calcareous Soils of Southern Iran

ABSTRACT:A laboratory experiment was conducted to investigate time-dependent kinetics of Ni retention in ten calcareous soils of southern Iran using mathematical models. Soil samples were equilibrated with 800 mg L-1 Ni solutions for seven periods of 1, 5, 30, 120, 240, 450, and 840 min and Ni concentration was determined in the filtrates using an atomic absorption spectrophotometer. Ni adsorption data were fitted to six commonly used kinetic models.The power function, first order, and second order equations were the best fitted models describing the patterns of Ni adsorption on the calcareous soils as evidenced by relatively high values of R2 and low values of SE. However, the Elovich and parabolic diffusion models were not well fitted to the Ni adsorption data due to their high values of SE.Significant correlation coefficients were found between the amounts of Ni adsorbed at most shaking periods. However, the amounts of Ni adsorbed at 1 min were not shown significant correlation with the value of Ni adsorbed at the other periods.The amount of Ni retained at the first shaking period (1 min) was significantly correlated with OM, pH, and clay contents of the studied soils. The amounts of Ni retained at 450, 840, and 1440 min shaking periods were correlated with silt and clay contents of the studied soils. Significant positive correlations were observed among the amounts of Ni retained onto most of the soils studied, demonstrated that the studied soils followed relatively similar pattern in their Ni adsorption characteristics. Although, the studied soils showed considerable differences from the view of their initial Ni adsorption rates.