Abstract:
Contamination of water streams due to discharge of dye containing wastewater is a
worldwide problem. Adsorption is an effective and efficient method for removing dye stuff
from waste water. However high cost of commercial adsorbents limit its use in wastewater
treatment.
In this study potential of untreated sugarcane bagasse pith as a low cost adsorbent for
removal of Methylene Blue (MB); a basic dye, was investigated. Batch experiments were
conducted to determine the factors affecting dye removal. Results revealed that the
percentage of dye removal depends on adsorbent dosage, initial dye concentration of the
solution, solution pH and contact time. Distinctly low MB removal was observed at low
solution pH values (<4). At high pH values (4 to 10), high MB removal was obtained and
variation of percentage removal with pH was not significant. Equilibrium data fits to
Langmuir isotherm and highest dye uptake of 40mg/g was observed. Adsorption rate was
very rapid initially and gradually decreased with time.
Fixed bed column experiments were performed to study practical applicability and
characteristic ‘S’ shape breakthrough curves were obtained. Increase in breakthrough time
and bed capacity was observed when the bed height is increased. Fixed bed column data
were fitted to Bed Depth Service Time (BDST) model and Yoon Nelson model for different
bed heights.
In this work, new mathematical model was developed based on film-pore diffusion in non
equilibrium conditions to study the dynamics of the column for methylene blue adsorption.
Model consists of a system of partial differential equations (PDEs), accounts for the effects
of axial dispersion, film-pore diffusion, and external mass-transfer resistances. External mass
transfer coefficient calculated using kinetic data obtained from batch experiments was found
to be 0.7096 cm min-1 and this valve was used for model calculations. Using the model,
effect of bed height and initial concentration on breakthrough curves were predicted. Further,
concentration distribution along the radial direction of bagasse particles at different locations
of the bed was analyzed. This model was validated using experimental data obtained by
fixed bed column experiments.
