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Order of appearence	Full citation	SRCosmos Link
1	Helfferich F, (1962) Ion Exchange, McGraw Hill, New York/San Francisco/Toronto/London.
2	Varon A, Iii W, (1964) 'Kinetics of Ion Exchange Kinetics in a Chelating Resin', The Journal of Physical Chemistry, 68, 2716-2718.
3	Leyden DE, Underwood AL, (1964) 'Equilibrium Studies with the Chelating Resin Dowex A-1', The Journal of Physical Chemistry, 68, 2093-2097.
4	Figura P, Mcduffie B, (1977) 'Characterization of the Calcium Form of Chelex-100 Resin for Trace Metal Studies', Analytical Chemistry, 49, 1950-1953.
5	Heitner-Wirguin C, Markovits G, (1963) 'Kinetics of Ion Exchange in a Chelating Resin Bio-Chelex-100. I. The Exchange of the Alkaline Earth Ions', J.Phys.Chem., 67, 2263-2266.
6	Turse R, Iii W, (1961) 'Kinetics of Ion Exchange in a Chelating Resin', J.Phys.Chem., 65, 1821-1824.
7	Gopala Rao M., Gupta A.K., Williams E.S. and Aguwa A.A. (1982) 'Sorption of Heavy Metals Ions on Chelex 100 Resin', American Institute of Chemical Engineers, Symposium Series, No. 219, 78, 103 –111.
8	Levenspiel O, (1993) Chemical Reaction Engineering, 2nd ed., Wiley Eastern, New Delhi.
10	Makarewicz PJ, Harasta L, Webb SL, (1981) 'Application of Shrinking Core Kinetics to Bone Demineralization', American Institute of Chemical Engineers, Symposium Series, No.202, 77, 141-149.
11	Loureiro JM, Costa CA, Rodrigues AE, (1988) 'Recovery of Copper, Zinc and Lead from Liquid Streams by Chelating Ion Exchange Resins', Chemical Engineering Science, 43, 1115-1123.

Keywords	chelating resin, ion exchange, swelling, shrinking core model
Abstract	In the present study the Pb2+ uptake by Lewatit TP-207 is examined in a batch type reactor, under different operating conditions. The effect of agitation (0-650 rpm) and temperature (35-65oC) is examined under the same Pb2+ concentration (500 mg/l). Agitation effect is more pronounced since by increasing the agitation rate from 0 to 650 rpm the uptake is increased by a factor near to 9, while by increasing the temperature from 30 to 65oC the uptake is increased by a factor near to 2. Temperature effect is more intense in the absence of agitation. Furthermore, the process is modeled using the shrinking core model. Sorption of heavy metals on a chelating resin is not an ordinary ion exchange process. It is the ion exchange accompanied by an ionic, non-reversible reaction. Levenspiel used a shrinking core model to describe the rate of fluid-solid non- catalytic chemical reactions. This model has been adapted in the present study to describe the sorption rates of Pb2+ on the chelating resin. The model is applied on batch reactor data, at 30oC and rigorous agitation (650rpm), under three different Pb2+ concentrations (100, 500 and 1000 mg/l). It is found that the process is controlled by the chemical reaction step rather than the diffusion processes (solid or liquid film diffusion). Despite the satisfactory application of the model on the experimental data, reaction rate constant is found to be concentration-dependent, a fact not expected from theory since the specific rate of the reaction is only temperature-dependent. Resin swelling concept is used in order to explain the results. Swelling of the resin is increasing the particle radius and according to the equations of the model, bead radius is affecting the fitting of the model on the experimental results. When resin beads are immersed into the solution, water uptake is taking place, almost immediately, resulting in a new “swollen” bead radius. This is not been taken into account in the related literature, as Levenspiel’s model is using a constant radius. Then, it can be proved that the rate constant is not concentration dependent as this dependence is a result of the change of particle radius due to swelling.
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Name	Affiliation	Home page	e-mail	Total pubs
Grigoropoulou HP	Laboratory of Chemical Process Engineering School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechniou, 15780, Athens, Greece		lenag@chemeng.ntua.gr	17
Inglezakis J	SC European Focus Consulting srl, Bacau, Romania		inglezakis@efcon-group.ro	9
Lozidou M				1