Tannin adsorption characteristics of bed sediments of Edava-Nadayara and Paravur backwater systems, southwest coast of India

Abstract

The adsorption behaviour of tannin was investigated under varying factors like, time of contact, <i>p</i>H, salinity and the presence of anions such as chloride, chlorate, nitrate, acetate, sulphate and phosphate. The removal of tannin by sediments was found to be <i>p</i>H and salinity dependent. Adsorption of tannin by sediments increases with clay content associated with the samples. Maximum adsorption of tannin was observed at<i> p</i>H 5.0. The percentage removal of tannin increases with increase in salinity. The data indicated that the presence of phosphate ions play an important role in retarding the adsorption of tannin by sediments and phosphate effectively competes with tannin for adsorption sites on sediments. The applicability of Langmuir and Freundlich isotherm models has been tested. Sediments from non-retting zone possessed higher adsorption capacity based on the Langmuir maxima.