4.2.7. Different types of wastes sludges as adsorbent
Different industries produce sludge as by-products which have
been examined as adsorbents by various researchers. Chrome
sludge, a solid waste material from an electroplating industry, was
used as an adsorbent for As(V) removal by Lee and Lee [308].
The maximum sorption capacity of chrome sludge for As(V) was
reported as 21 mg/g. Chrome sludge was also tested to remove
dyes from aqueous solutions [309] and the results indicated that
the sludge had a better affinity for acid dyes than basic dyes.
Color removal of an aqueous solution containing water-based
inks, a mixture of resins, pigments, and dyes, was investigated by
using metal hydroxide sludge, which is a waste from the electroplating
industry by Netpradit et al.[310]. The maximum adsorption
capacity for the red ink was reported as 34.48 mg/g ofmetal hydroxide
sludge. Waste metal hydroxide sludge was used as low-cost
adsorbent for removing a reactive textile dye (Remazol Brilliant
Blue) by Santos et al. [311]. The maximum adsorption capacity of
91.0 mg/g was found at 25 ◦C and pH 7.
Sewage sludge has also been used to develop an effective adsorbent.
This adsorbent was employed for the removal of azo dye such
as Direct Dark Brown M and Acid Mordant Brown RH by Chen et