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Decolourisation of wastewater is important because of their detrimental effect on the health of
aqua-life and human beings that use receiving water body for domestic and industrial purposes.
This research was designed to evaluate biosorbent potential of Moringa oleifera seeds and seed
coat as alternative adsorbents for removal of Congo-Red dye from aqueous solution. M. oleifera
seeds and seed coat were ground with electric blender to obtain ground M. oleifera seed (GMS)
and ground M. oleifera seed coat (GMC). A portion of each of the ground samples were
activated with 5% NaOH solution to obtain activated M. oleifera seed (AMS) and activated M.
oleifera seed coat (AMC). GMS, AMS, GMC and AMC were used to adsorb Congo-Red dye
from aqueous solution. The adsorption isotherm is best fit with Freundlich isotherm. The free
mean energy E in Dubinin-Radushkevich (D–R) isotherm was between 1 kJmol-1 and 16 kJmol-1
suggesting physisorption adsorption process in all biosorbents used. Positive value of ΔS
indicated that there was increase in degree of disorderliness in adsorption process and positive
value of ΔH indicated endothermic nature of adsorption reaction as quantity of dye adsorbed
increases with increase in temperature from 28oC – 60oC. The negative value of ΔG showed that
adsorption reaction is spontaneous in all adsorption temperature used. All the biosorbents have a
very good potential to be used as adsorbents for removal of Congo-Red dye from aqueous
solution, since they all have percentage dye removal greater than 50%.
Keywords: Aqua-life; Biosorbent; Endothermic; Isotherm; Physiosorption