Photocatalytic Processes for the Removal of Dye - Green Chemistry for Dyes Removal from Wastewater - page 150

5.2.2 Bagasse
Bagasse is a lingocellulosic residue from the processing of sugarcane after
the sucrose extraction from crushed cane. It consists of approximately
40-45% cellulose and 30-35% hemicelluloses and 20-30% lignin [53]. Out
of the numerous applications of bagasse, adsorption of various pollutants
has been found to be one of the most attractive topics which have gained
the attention of researchers due to the low ash content of this material.
Ho and McKay [54] carried out an exhaustive study on the kinetics of
dye removal with bagasse pith. The adsorption capacity of the bagasse pith
was found to be 82.8 mg.g -1 for Maxilon Red and for Erionyl Red. Effects of
several parameters, such as adsorbent dose, initial concentration of the dye
solution, particle size of the adsorbent and temperature have been exten-
sively studied. Also, different kinetics models have been employed to fit
the experimental data, including pseudo-first-order, pseudo-second-order
and intraparticle diffusion model. They concluded that the sorption of dyes
onto bagasse pith is best described by the pseudo-second-order model. It
is notable that McKay et al. have also conducted research on the applica-
tion of pore diffusion model, which is out of the scope of this chapter [55].
The adsorption of several dyes by ball-milled sugarcane bagasse has been
studied by Zhang et al. [56,57]. By investigating the effect of initial dye
concentration, pH and adsorbent dosage, the adsorption capacity of the
bagasse was determined to be 38 mg.g -1 for Congo red, 43.5 mg.g -1 for
Rhodamine B and 27.8 mg.g -1 for Basic Blue 9. It has been observed that
an increase in the surface area of the adsorbent resulted in an enhanced
dye removal due to the provision of more active sites (see Figure 5.6).
The mechanism of adsorption has been well-described by conducting
Fourier transform infrared (FTIR) analysis. It was shown that the interac-
tions between the carboxyl and hydroxyl groups of bagasse with sulfonic
acid groups of Congo red and amine groups of Rhodamine B and Basic
Blue 9 were responsible for the uptake of the dye molecules. Tsai et al.
[58] impregnated the bagasse with zinc chloride followed by pyrolysis at
500 C under nitrogen atmosphere. The modification process has resulted
in the appearance of oxygen complexes, probably carboxyl and phenolic
hydroxyl groups, on the surface of the activated material, which would lead
to its hydrophilicity and surface acidity. The surface area analysis showed
that a large amount of micropores had been developed and the surface
area increased substantially when the impregnation ratio was raised to
more than 50 wt% (see Table 5.3). Although sufficiently high microporos-
ity was developed, the adsorption capacity remained very low (~5 mg.g -1 ).
Valix et al. [59] successfully prepared very high surface area activated
carbons with high dye uptake capacity. They carbonized the bagasse at a