IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 04 Issue: 03 | Mar-2015, Available @ http://www.ijret.org 20 ADSORPTION BEHAVIOUR OF DEXTRIN ONTO ACTIVATED OYSTER SHELL C. I. O. Kamalu 1 , P. Oghome 2 , K. N. Nwaigwe 3 , E. E. Anyanwu 4 1 School of Engineering and Engineering Technology, Federal University of Technology, P. M. B. 1526, Owerri, Nigeria 2 School of Engineering and Engineering Technology, Federal University of Technology, P. M. B. 1526, Owerri, Nigeria 3 School of Engineering and Engineering Technology, Federal University of Technology, P. M. B. 1526, Owerri, Nigeria 4 School of Engineering and Engineering Technology, Federal University of Technology, P. M. B. 1526, Owerri, Nigeria Abstract The effect of initial dextrin concentration, contact time, pH, temperature and added calcium ion on the adsorption behaviour of dextrin onto oyster shell is investigated. The results obtained show that increase in concentration and temperature below the boiling point of dextrin enhances the adsorption process. It was found in this study that adsorption density varies with pH and is maximum within the range of 2 to 7. The plot of amount of dextrin adsorbed against the concentration of the adsorbate was hyperbolic which conforms to Legmir isotherm. The free energy of dextrin oyster shell adsorption system was found to be 13.23kg/mol and the specific area of the oyster shell for this work was 70.8m 2 /g. Keywords: Adsorption, dextrin, oyster shell, behaviour, crushing, drying -------------------------------------------------------------------***------------------------------------------------------------------- 1. INTRODUCTION Many adsorbents such as silica get, activated alumina, carbons, and zeolites have been found useful for different adsorbates in different separation technique (Wei, 1994). When molecules moved from a bulk fluid to an adsorbed phase, they lose degrees of freedom and the free energy is reduced. Adsorption in always accompanies by the liberation heat and for physical adsorption, the amount of heat is similar in magnitude normally associated with a chemical reaction (Charles, 1991) A number of investigators (Subramanian et al, 1988: Caesar, 1968, Weber, 2002) have studied the depression behaviour of starch and its derivatives in the flot6ation of hematite and quarts. Electrostatic interaction and hydrogen bonding have been suggested as a mechanism for the adsorption of polyelectrolytes by Miller et al 1983. according to clap et al, 1998 starch adsorption occurs via hydrogen bonding between the solid surface and the hydroxyl groups on the polymer. Their result showed that common starch in negatively charged in aqueous solution in the pH range of 3 to 11. The amount of dextrin adsorbed on quartz, however is clearly considerably than that on molybddenite. It was suggested that the adsorption process may be due to hydrophobic bonding with the polymer molecule displacing water molecules at the interface (Liu et al, 1989; Onuoha, 1995). Experimental evidence has shown that the external addition of metal ion enhances adsorption of starch. In the case of dextrin adsorption, the hydrophobic theory lies heavily on the fact that the minerals that adsorbs dextrin are hydrophobic which could be either anisotropic (tale and molybdenite) or heterogeneous (Hals, 1974). Dextrin dissolves in water to form a sticky solution. It is chiefly used in mixing glues, adhesives on postage stamps ad sticky paper for Steffen textiles to produce a “head” on beer and other carbonated beverages (Hals, 1974). Oyster is on edible bivalve mollusk (one with a two pieced shell). The two parts of an oyster shell are different in size and shape for example Pearl and Bermuda oysters (Gregg el al, 1982) Oysters live attached to occen bottom in hard-surface areas called oysters beds and are found in all temperature and tropical oceans. The three genera of oyster shells (pyenodonta, crassotrea, ostrea) are returned to the beds to provide places on which larvae may set. Cultivated oyster shell beds helps in avoiding depletion in the river beds. Crushed oyster shells are fed to chickens. The shells are also burned and slaked to make lime for fertilizer. Crushed oyster shells can be used as adsorbent (Peterson et al, 1991). Oyster shells are composed of carbonaceous materials, when of carbonaceous materials, when heated in absence of air, mush of the substance devolatilizes, leaving behind a prorous structure of carbon that usually, also, contains some hydrogen (Frish et al 1999). This may then be activated by controlled oxidation with steam or carbon dioxide to further open up the pores and increase total surface area. During the heating process, the oyster shell surface is exposed more by the expansion, which occurs. Also, heating reduces the layers together (Subramanian et al 1988; Caesar 1998). There are four ranges of temperatures at which characteristic transformation or changes are produced in a carbonaceous materials (such as oyster shell) when thermally heated (Healy et al 2002; Khasla et al, 2004). The aim of this study is to establish he adsorption mechanism of dextrin using