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Dye-based industries, particularly small
and medium scale, discharge their effluents into
waterways without treatment due to cost considerations. We investigated the use of biochars produced
from the woody tree Gliricidia sepium at 300 C
(GBC300) and 500 C (GBC500) in the laboratory
and at 700 C from a dendro bioenergy industry
(GBC700), to evaluate their potential for sorption of
crystal violet (CV) dye. Experiments were conducted
to assess the effect of pH reaction time and CV loading
on the adsorption process. The equilibrium adsorption
capacity was higher with GBC700 (7.9 mg g-1
) than
GBC500 (4.9 mg g-1
) and GBC300 (4.4 mg g-1
), at
pH 8. The CV sorption process was dependent on the
pH, surface area and pore volume of biochar (GBC).
Both Freundlich and Hill isotherm models fitted best
to the equilibrium isotherm data suggesting cooperative interactions via physisorption and chemisorption
mechanisms for CV sorption. The highest Hill sorption capacity of 125.5 mg g-1 was given by GBC700
at pH 8. Kinetic data followed the pseudo-secondorder model, suggesting that the sorption process is
more inclined toward the chemisorption mechanism.
Pore diffusion, p–p electron donor–acceptor interaction and H-bonding were postulated to be involved in
physisorption, whereas electrostatic interactions of
protonated amine group of CV and negatively charged
GBC surface led to a chemisorption type of adsorption. Overall, GBC produced as a by-product of the
dendro industry could be a promising remedy for CV
removal from an aqueous environment
