Kinetic and isotherm study of basic red dye adsorption by axonopus compressus
Abstract
The utilization of Axonopus compressus is introduced as a new absorbent for the
removal of cationic dye, BR 46 from the aqueous solution. Various parameters,
including pH (3-11), initial solution concentration (50-250 mg L-1), temperature (30-
60 °C), adsorbent dosage (0.2-1.00 g), were used to study the effects on BR 46
biosorption. The results appeared that the adsorption process took place well in alkaline
condition with optimum pH 9. The adsorption rate decreased when the temperature
increases showing the adsorption process is exothermic. The adsorption is favour with
increase in adsorbent dosage and initial dye concentration. However the percentage of
removal decreased once the amount of dosage reaches more than 0.6 g. The equilibrium
data fitted better in Freundlich model, although it also can fit into Langmuir model
demonstrate that the adsorption occurs at heterogeneous sites and multilayer biosorption.
The maximum monolayer biosorption capacity was 78.74 mg/g with the degree of
adsorption 2.17 mg/g. The adsorption process followed the pseudo-second order kinetic
model showing chemisorption was involved during adsorption process. Intra-particle
diffusion model was used to test the mechanism of rate-determining factor. The results
showed that intra-particle diffusion was not the only rate-determining step during
adsorption