Biosorption
experiments were conducted using non-living biosorbents, crushed maize cob and
coconut husk to determine the effect of dosage and size on sorption of heavy
metals from wastewater. Particle sizes passing the 6.3 mm, 2.0 mm, 0.6 mm,
0.212 mm and 0.063 mm BS sieve sizes were used in the experiments. Solutions of
Cd (II), Pb (II), Ni (II), Cr (VI) and Cu (II), each prepared in different
concentrations of 10 mg/ml, 20 mg/ml, 30 mg/ml, 40 mg/ml and 50 mg/ml were
passed through the biosorbents. Results showed that coconut husk is a better
biosorbent than maize cob with maximum sorption of 71.6 % at particle size of
0.063 mm and dosage of 50 mg/ml, this was followed by Chromium with 64.5 %,
Lead with 56.8 %, Copper with 50.6 % and least by Nickel with 44.4 % all at 50
mg/ml. The test of hypothesis at 5 % level of significance showed that
calculated at 10 mg/ml, 20 mg/ml,
30 mg/ml, 40 mg/ml and 50 mg/ml corresponding to 0.911, 0.219, 0.212, 0.691 and
0.619 were less than the tabulated t,
the null hypothesis was chosen which indicated that there is no significant
difference in the sorption affinities of these heavy metals to coconut husk and
maize cob biosorbents. Coefficient of variation at various doses from 10 mg/ml
to 50 mg/ml were 0.1275, 0.1145, +0.1181, 0.1032 and 0.1021 which showed very
little variability. It was concluded that although there are differences in the
sorption capacities of these biosorbents and the affinities of these heavy
metals in attaching themselves on the surfaces of the biosorbents, the
differences are not significant.
