Removal of Organic Dyes from Industrial Effluents: An Overview of Physical and Biotechnological Applications - Green Chemistry for Dyes Removal from Wastewater - page 21

for the removal of reactive dyes such as Reactive Blue, Reactive Red, Reactive
Violet and Reactive Yellow. Dead cells of test genera showed a higher uptake
than living cells due to an increased surface area and/or metabolic resistance
and Gram-negative bacteria had a higher adsorption capacity than Gram-
positive bacteria due to higher lipid contents in the cell wall portion.
A screening of bacteria with the ability of degrading several structurally
different dyes such as Poly R-478, Methyl Orange, Lissamine Green B and
Reactive Black 5 was carried out by Deive et al. [172].
Both aerobic and anaerobic strains were detected, but they have observed
that a facultative anaerobic strain was the one leading to the most promis-
ing results.
The decolorization ability of Anoxybacillus flavithermus in an aque-
ous effluent containing two representative textile finishing dyes (Reactive
Black 5 and Acid Black 48) was investigated. It has been observed that the
decolorization efficiency for a mixture of both dyes reached almost 60% in
less time than 12 h, which points out the suitability of the selected micro-
organism [173].
An effective decolorizing bacterial strain, Bacillus sp. , for Reactive
Black 5 (RB-5) was isolated by Wang et al. [174]. This bacterial strain
showed great capability to decolorize various reactive textile dyes, includ-
ing azo dyes. Optimum conditions for the decolorizing of RB-5 were deter-
mined to be pH 7.0 and 40 C. Bacillus sp., which grew well in medium
containing high concentration of dye (100 mg/L), provides approximately
95% decolorization in 120 h and has a practical application potential in the
biotransformation of various dye effluents.
On the other hand, the ionic forms of the dye in solution and the surface
electrical charge of the biomass depend on solution pH. Therefore, solu-
tion pH generally influences both the fungal biomass surface dye binding
sites and the dye chemistry in the medium [10,175-178].
Most textile and other dye effluents are produced at relatively high tem-
peratures and hence temperature will be an important factor in real appli-
cation of biosorption in the future. Arica and Bayramoglu [177] found that
heating the biomass, Lentinus sajor-caju, at 100 C for 10 min significantly
enhanced the biosorption capacity, while base-treatment with 0.1 M NaOH
lowered the biosorption capacity of the fungi to remove Reactive Red 120
and also the biosorption of dye increased with increasing temperature.
Aksu and Cagatay [179] reported that for R. arrhizus the biosorption of
dye increased with increasing temperature.
Hu [171] has investigated the ability of bacterial cells isolated from
activated sludge to adsorb reactive dyes, including Reactive Blue, Reactive