| dc.description.abstract | Heavy metals exist in the ecosystem both naturally and due to anthropogenic activities and as
recalcitrant pollutants; they are non-biodegradable and cause acute and chronic diseases to
human beings and many lifeforms. As a result, the removal of heavy metals from aqueous
systems using sorbent materials produced from agricultural wastes is one of the new innovative
treatment techniques. In this study, the biosorption and desorption characteristics of heavy
metal ions from non-competitive and competitive aqueous solutions onto hybrid granular
activated carbon produced from maize residues were investigated. The efficient sequestration
of As(III) and Hg(II) ions from both monocomponent and bicomponent synthetic wastewater
was found to show dependence on the physicochemical properties of the biosorbent and the
studied independent biosorption process factors. The regenerated biosorbent could be reused
up to the eighth cycle for the sequestration of As(III) and Hg(II) ions from the synthetic
wastewater without significantly losing its adsorptive properties. The applicability of the
biosorbent synthesized from the maize residues for the simultaneous decontamination of heavy
metals found in real industrial wastewater as a function of several biosorption factors showed
that the biosorbent could competitively decontaminate over 96% of As, Hg, Pb, Cd, and Cr in
100 mL textile wastewater in batch mode. The regeneration of the spent biosorbent using 0.10
M HCl showed that the biosorbent is capable of being recycled and reused severally for the
sequestration of As, Hg, Pb, Cd, and Cr from the textile wastewater and even up to the ten
cycles for a duration of 4 h. The optimization of the competitive removal of As and Hg ions in
the co-existence of other heavy metals in the textile wastewater by the CCD-RSM resulted in
maximum removal efficiencies of 97.72 and 99.99%, respectively. The characterization of the
hybrid granular activated carbon using SEM, TEM, XRD, BET, and FTIR showed that the
biosorbent surface characteristics could facilitate the removal of heavy metals from the non competitive and competitive biosorption media. The main biosorption mechanism of the heavy
metal ions on the biosorbent was mainly chemisorption involving surface complexation.
Therefore, this novel biosorbent is found to be promising and could effectively be employed
for heavy metals remediation in aquatic environments. The outcomes of this study are expected
to make a significant contribution to the design of low-cost and efficient industrial wastewater
treatment systems such as a dynamic batch rector for heavy metal removal using locally
available bio-adsorbents. | en_US |
