Kinetic Modeling of Adsorption of Indigo Carmine (5, 5'- Disulfonic Indigotin) on Peat

Abstract

The kinetic of Indigo Carmine (5,5, adsorption on fibrous peat (FP) and decomposed peat (DP), have been investigated at different temperatures (283, 298, 313) K at pH 2. The effect of particle size was studied considering the variation of grain size of each peat (2000-850, 850-600 and < 600) nm.The fibrous peat shows higher adsorption capacity than the decomposed peat, while under the same work conditions.The kinetics of adsorption of 5,5'-DI is discussed using three kinetic models, the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model.The adsorption of 5, 5'-DI onto peat proceeds according to the pseudo second-order model and the correlation coefficients were very close to 1.At 283, 298 and 313 K the maximum sorption, q max,calc , for the initial concentration (C o = 4.05 × 10 -5 mol L -1 ) of 5,5´-DI were q max,calc is (5.57, 7.92 e 8.29) × 10 -4 g g -1 for fibrous peat and (5.29, 6.74 e 5.83) × 10 -4 g g -1 for decomposed peat.The intraparticle diffusion of 5,5'-DI molecules within the peat particles was identified as the rate-limiting step.