REMOVAL OF CHROMIUM FROM ELECTRO- WASTEWATER BY ADSORPTION

Abstract

Chromium waste discharged from industries may consist of chromium in hexavalent and trivalent forms. These industries are aluminum anodizing and metal cleaning. chrome tanning, dyes manufacturing, electroplating etc. Hexavalent form believed to be more toxic and is known to be carcinogenic. The need For treatment of' industrial wastewater for hexavalent chromium removal prior to discharge to water ways is a big problem even today. Central Pollution Control Board (CPCB) and Bureau of Indian Standards (BIS) have the given the tolerance limits of various parameters for the wastewater of different industries. At present many methods are available for removal of chromium from waste water such as ion exchange, precipitation, membrane separation, reverse osmosis. adsorption, etc.; but adsorption by activated carbon still continues to be most widely used process because of its safe, environment friendly and easy process. The Cr(VI) adsorption experiments were carried out to analyze the influence of adsorbent dose, pH. initial Cr(VI) concentration, carbon-solution time and temperature. on the efficiency of Cr(VI) retention by activated carbons. The equilibrium data could be described well by Langmuir and Freundlich isotherm equations. A separation factor was used to judge the favorable adsorption. Thermodynamic parameters such as Gibbs free energy (AC), enthalpy (AHfi). and entropy (AS°) were also calculated. Characteristics of the activated carbon are done by XRD, SEM process and by proximate and ultimate analysis. The extent of adsorption and reduction processes depends on the porous texture, nature and preparation procedure of activated carbons