Non-conventional Adsorbents for Dye Removal - Green Chemistry for Dyes Removal from Wastewater - page 380

and solution properties and vary with crystallinity, affinity for water, per-
cent deacetylation and amino group content [191-193]. Adsorption prop-
erties are also dependent on the type of material used and the uptake is
strongly pH-dependent. These problems can explain why it is difficult to
develop chitosan-based materials as adsorbents at an industrial-scale. In
their review, Crini and Badot [190] concluded chitosan-based materials
may be promising biosorbents for adsorption processes since they demon-
strated outstanding removal capabilities for dyes.
10.10 Biomass
The literature clearly shows a greater number of studies on the adsorption
of metal ions by biomass as compared with organic pollutants [215,216].
Indeed, biomass has received considerable interest in metal adsorption
due its excellent metal-binding capacities through various mechanisms
and interesting selectivity. However, attention has also been focused on
the interaction between dyes and biomass. Biosorbents derived from suit-
able microbial biomass can be used for the effective removal of dyes from
solutions since certain dye molecules have a particular affinity for bind-
ing with microbial species [217-223]. The use of biomass for wastewater is
increasing not only because of its high potential as a complexing material
due to its specific physicochemical characteristics, but also because of its
availability in large quantities and at low prices. A wide variety of micro-
organisms including algae, yeasts, bacteria and fungi are capable of decol-
orizing a wide range of dyes with a high efficiency. Fungi can be classified
into two kinds according to their life state: living cells to biodegrade and
biosorb dyes, and dead cells (fungal biomass) to adsorb dyes. Most of the
studies have concentrated on living fungi for biosorption of the dyes. There
are few studies on dye removal using dead fungal biomass, except in recent
years. Table 10.9 shows some of the adsorption capacities reported in the
literature. Fu and Viraraghavan [224-227] demonstrated that, compared
with commercial activated carbons, dead fungal biomass of Aspergillus
niger is a promising biosorbent for dye removal. Aksu and Tezer [228]
demonstrated uptake of 588.2 mg of Reactive Black 5 per g using Rhizopus
arrhizus biomass. Waranusantigul et al. [229] and Chu and Chen [230,231]
also reported the usefulness of biomass for the removal of basic dyes. The
biosorption capacity of fungal biomass could be increased by some pre-
treatment (by autoclaving or by reacting with chemicals). Other types of
biomass such as yeasts have been studied for their dye uptake capacities
[232,233]. Yeasts are extensively used in a variety of large-scale industrial