STUDIES ON REMOVAL OF SELENIUM FROM WATER BY ADSORPTION

Abstract

The present work involves the study of Se(IV) adsorption onto bagasse fly ash (BFA), rice husk ash (RHA), granular activated carbon (GAC) and powdered activated carbon (PAC). The adsorbents were coated with the ferric chloride solution for the effective removal. The physico-chemical characterization of the adsorbents has been carried out using standard methods e.g. proximate analysis, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), thermo-gravimetric (TGA) and differential thermal analysis (DTA), etc. Batch experiments were carried out to determine the effect of various factors such as adsorbent dose (w), initial pH, contact time (t), and temperature (1) on adsorption process. Results obtained from these studies have been analyzed by various kinetic models and isotherms. From the results it has been inferred that PAC is having highest removal efficiency among all the adsorbents used at natural pH. Se(IV) adsorption onto all the adsorbents used is high at lowpH values, and decreased with the rise in initial pH. Temperature study shows that the uptake of Se(IV) by all adsorbents is more at 293 K with in the temperature range studied. The parameters of Pseudo-First order, Pseudo-Second order kinetics, Weber-Morris infra particle kinetics have been determined. Equilibrium isotherms have been analyzed using Langmuir isotherm, Freundlich isotherm and Temkin isotherm and parameters have been calculated for all the isotherms. Error analysis has also been done using hybrid fractional error function (HYBRID) and Marquardt's percent standard deviation (MPSD). ii