Prof. D. N. Singh

PANKAJ PATHAK

Ph. D.
Indian Institute of Technology Bombay, Powai, India pankajpathak18@gmail.com

DETERMINATION OF DISTRIBUTION COEFFICIENT OF SOIL-CONTAMINANT SYSTEM

Disposal of hazardous and toxic waste in geoenvironment has become a major challenge in the present day scenario. When contaminants present in these wastes come in contact with the soil, the 'soil-contaminant interaction' occurs and during this interaction, cations present in the contaminants are retained (termed as sorption) by the soil. This interaction can be quantified by employing a mathematical term 'Distribution coefficient', kd. A critical analysis of the existing literature indicates that the kd is influenced by several soil and contaminant specific parameters (viz., specific surface area, cation exchange capacity, percentage organic matter, percentage of fines, mineralogy, redox potential, type of ionic species and concentration, pH, temperature, and interaction time). Hence, determination of the kd becomes a tedious exercise mainly due to requirements of massive experimental investigations. This necessitates designing the tests appropriately, which can be done by employing the 'Taguchi method', a statistical method that can be employed to: (i) design the batch tests, (ii) identify the most critical parameter(s) that influence(s) the kd and (iii) predict kd. This analysis also helps in developing the 'lookup table', which would be of immense help for estimating the kd for a certain soil-contaminant system, under varied reaction conditions. Based on extensive batch tests on various soil-contaminant systems, guidelines for selecting appropriate concentration of the contaminant(s), to quantify soil-contaminant interaction have also been developed and recommended for precise determination of kd. In addition, kinetic and thermodynamic studies were performed to understand the rate and nature of reactions taking place in the soil-contaminant system.