Modeling the influence of the operating conditions upon the sorption rate and the yield in the adsorption of lead(II)

Alkaline activated carbon from Coconut (Cocos nucifera) shells and acid activated carbon from Bois carré (Citharexylum fruticosum L.) seeds have been prepared and tested for the sorption of lead. The efficiency of the adsorption depends on the value of the rate constant k, relative to the sorption rate, and, depends also on the value of the equilibrium constant K, relative to the sorption yield. Higher are these constants, higher the adsorption efficiency. Moreover, the adsorption results depend on the operating conditions. So, the influence of temperature, initial pH, initial lead concentration and adsorbent dose on the rate constant and on the equilibrium constant are investigated onto these two activated carbons. The results show, for the activated carbon from Bois carré seeds, that increasing the temperature increases the sorption rate and decreases the adsorption capacity, increasing the pH increases the sorption rate while the sorption capacity remains constant, increasing the lead initial concentration decreases the sorption rate and increases the sorption capacity and increasing the adsorbent dose decreases the sorption capacity while the sorption rate passes through a maximum. Moreover, the study shows that linear equations describing the behavior of the rate constant and the equilibrium constant upon the operating parameters can be found. The knowledge of these equations will permit to determine the optimum operating conditions and to predict the sorption results under these operating conditions range (temperature, initial pH, initial concentration, adsorbent dose) without having to refer to supplementary experiments.