5. Effect of Adsorbent Dose The adsorption of the dyes on prawn waste biomass was studied by varying the sorbent concentration (0.1 to 0.4 g in 50 mL). The percentage of adsorption
increased as the adsorbent concentration increased shown in Fig. 4. This increase is due to the availability of larger surface area with more active functional groups at higher adsorbent dosages. 6. Adsorption Kinetics The chemical kinetic describes reaction pathways with time to reach the equilibrium whereas chemical equilibrium gives no information about pathways and reaction rates. In order to investigate the mechanism of adsorption, various kinetic models have been suggested. In this study, some of these models were investigated to find the best fitted model for the experimental data obtained. Adsorption kinetic data of MB are analyzed using the Lagergren pseudo-first-order rate equation [30]: . .
(6)
-1where q (mg g ) refers to the amount of dye adsorbed t at time t (min), and k is the rate constant. The rate ad constant k could be calculated from the slopes of the ad linear plots of log(q - q) verses t. etwhere k is the rate constant of second order adsorption. 2 Values of k and q were calculated from the plots of t/q 2 e vs t. Table 2 showed that the corresponding correlation 2 coefficient (R) values for the pseudo-second-order kinetic model were greater than those of pseudo-firstorder kinetic model indicating the applicability of the pseudo-second-order kinetic model to describe the adsorption.