Conjunctive Use of BTC and Batch Methods for Heavy Metal Transport

Abstract

Marginal sediments can be used to combat point-pollution by heavy metals in industrial zones. Such practice requires information on metal-concentration in the workshop discharge water. Knowledge about the reaction of the heavy metal with the sediment available in the landscape is of utmost importance. Modeling of batch experiments and breakthrough curves, BTC, supplies relevant information in this regard. We present the static batch results of Freundlich isotherms testing CdCl2 aqueous solutions equilibria with sandy loam sediments, along with column-data processed by the dynamic codes CfitM and CfitIM under saturated water flow conditions. Three Cd-concentrations (5, 20, and 40 ppm) were employed to investigate the conjunction of using two procedures for obtaining the pertinent parameters for the transport of such a heavy metal and the design of the adequate Cd-trap. The results showed the deviations of the two techniques due to differences in their theoretical concepts, mathematical formulation, and performance. The batch method showed utility in supplying first guesses for the retardation factor, R, to insert into the 4-parameter analytical code, CfitIM, applied for column BTC modeling. The iteratively-obtained-parameters of the Freundlich equation were then employed to generate the distribution coefficient, k d. The generated value was, in turn, used to get more fair guess for the retardation factor, R, to use as a fixed-value in the CfitIM code to get an in-depth insight into the BTC dynamics and to obtain the other pertinent model parameters. The BTC runs indicated that the concentration controls the distinctive adsorption and transport rate and behavior of the heavy metal in the sediment column. The most dilute solution offered the highest Cd impediment, as shown by the most significant values for the distribution coefficient, k d, and retardation factor, R. The malfunction of the sediment as a trap appeared at Cd-concentrations four to eight folds higher than the most dilute solution. However, the loamy sand trap is successful when fed with a dilute aqueous solution. A set of successive traps is to arrange in tandem lines when moderate to high concentration is to discharge from an industrial workshop. The results emphasize the utility of the mutual use of these two lab procedures for the design of adequate traps and landfills and the simulation of more complex situations in the field. The point-pollution control needs to continue running batch and BTC experiments and to carry out their corresponding modeling.