In order to find the best-fit kinetics model of adsorption of acid dyes
onto CTMAB-Bent, the pseudo-first-order, pseudo-second-order,
intraparticle diffusion and Elovich kinetics model (Table 2) were applied
to test the experimental data. The pseudo-first-order kinetics
equation can describe the initial phase in adsorption process and with
the progressing of adsorption, the adsorption data may deviate the
fitted curve. The pseudo-second-order equation agrees with chemisorption
as the rate-control mechanism [40]. According to intraparticle diffusion
model, several mechanisms are involved and the adsorption
process can be characterized into three steps: external surface adsorption,
intraparticle diffusion which is the rate-limiting step, and the
final equilibrium which is very fast [37]. Elovich equation was used to
describe the rate of adsorption that decreased exponentially with an increase
in the amount of adsorbate but did not provide any mechanistic
information about adsorption process.