Isotherms parameters of MB adsorption on CP and MCA.Isothermal modelsParametersCPMCALangmuirQm (mg/g)103.09163.93KL (L/mg)0.059150.2155RL0.03206–0.24850.00901–0.08322R20.99990.9998FreundlichKF ((mg/g)(L/mg)1/n)60.219728.1993n5.12824.4923R20.84010.8925D–RQm (mg/g)91.5971147.8354KD (mol2/kJ2)2E−057E−07R20.87460.8954Qexp (mg/g)98.62163.01Full-size tableTable optionsView in workspaceDownload as CSV
Furthermore, a dimensionless constant, RL, obtained from Langmuir model was used to reflect the essential characteristic of the Langmuir model. The RL can be calculated from the constant KL ( Cao et al., 2014 and Zhou et al., 2014b).equation(4)RL=11+KLC0where C0 (mg/L) 5-Iodotubercidin the initial dye concentration in solution and KL (L/mg) is the Langmuir isotherm coefficients related to the free energy of adsorption.
The value of RL describes the tendency of the adsorption process, which is either unfavorable (RL > 1), liner (RL = 1), favorable (0 < RL < 1), or irreversible (RL = 0). Greater affinity between the adsorbent and the adsorbate is inferred when RL is smaller. The RL values were in the range of 0.03206–0.2485 for CP and 0.00901–0.08322 for MCA, which implies that the adsorption of MB onto both CP and MCA was a favorable and useful process. Moreover, the RL value for MCA was smaller than that for CP, thus it can be concluded that the affinity of the adsorbents to MB is enhanced after the introduction of the nano-size Fe3O4 onto the surface of CP, which is consistent with the results observed during the adsorption tests.