Studies on the adsorption of naphthalene and pyrene from aqueous medium using ripe orange peels as adsorbent

Abstract

The effectiveness of dried ground orange peels in adsorbing naphthalene and pyrene from an aqueous stream has been investigated in terms of variation in concentration, adsorbent dosage, agitation time and particle size. Experimental batch data was correlated by Freundlich and Langmuir isotherm models. The Freundlich isotherm best described the adsorption process as the adsorption data fitted well into the model. The adsorption capacity and energy of adsorption were obtained as 7.519mg/g and 0.0863mg-1, and 3.8168mg/g and 0.0334mg-1 for naphthalene and pyrene respectively. The adsorption from the aqueous solution was observed to be time dependent while equilibrium time was found to be 100 and 120 minutes for naphthalene and pyrene respectively. Adsorption increased with increase in adsorbent dosage and was maximum at between 5 to 7g for naphthalene and 6 to 8g for pyrene. The maximum adsorption was observed using a particle size of 2.0mm. The rate of adsorption using the first order rate expression by Lagergren for naphthalene and pyrene were 0.007 and 0.006 min-1 respectively. These results therefore suggest that naphthalene is more selectively adsorbed than pyrene using ripe orange peel as adsorbent.

KEY WORDS: Naphthalene, Pyrene, Adsorption, Adsorbent, Ripe orange peels.