ODOUR REMOVAL USING ADSORBENT BEDS

Abstract

Adsorption process for waste water treatment has received much attention and is gaining lot of importance in the recent years as an efficient process. Adsorbents are used to remove organic impurities, particularly those that are non-biogradable or associated with taste, odour and colour. Although adsorption is applied most often as a tertiary treatment for impurities present in low concentration, recent physical - chemical processes use adsorption as a primary technique to remove soluble organics from the waste water. Among the various adsorbent employed for the purpose, activated carbn has found wide. acceptance by virtue of its high removal capacity and adaptability for a wide range of adsorbates. Adsorption of Pyridine and Acetic Anhydride onto Granular Activated Carbon (GAC) was studied in batch and continuous systems using synthetic waste-water. Suitability of GAC by isotherm equilibria and removal kinetics of adsorption process have been studied in batch experiments. Continuous tests in a fixed bed adsorption column have been carried out to fit Bohart-Adams Model and Hutchins Modification for particular . adsorbent and adsorbate combinations which predicts the solute concentration in bed as a function of time and bed height. Batch studies reveals that the adsorption isotherm isfavourable for the removal of Pyridine and Acetic Anhydride onto activated carbon. Freundlich isotherm constants are also evaluated. The equilibrium correlations can be written as :- For Pyridine q = 0.00219 C0.746 a = 0.026, CR = 0.995 Ac_etic Anhydride q = 0.00174 C0.859 a = 0.068, CR = 0.9851 Plot between q and I suggest that the intraparticle diffUsion is rate controlltng. Lagergr-en -plot-s at -41-i4f9-42ant_ initial concentration of odourous solution indicate a first order, rate kinetics for both the solutions. An effective odour removal of 99.7 % for Pyridine and maximum 93.4% for Acetic Anhydride have been obtained for maximum bed height taken as 120 cm in a down flow fixed bed column, when flow rate is 6.37 cm3/cm2 /min. The effect of bed height on the break through time is examined by the Bohart-Adams Model based on bed-depth retention time approach and Hutchins Modification. Its constants are evaluated and correlations are formed as :- For Pyridine CV V In t(Co/CE) - 11 z- (12!24 jt 1.175/V For Acetic Anhydride C V 1 ln{(Co/CE) - 1 } Z (13%8 j t 0.555/V Correlations for a different flow rate have been obtaind by bed depth- retention time approach. These correlations were satisfied when compared with experimental results.