Adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions bioremediation from aqueous solution using unmodified and EDTA-modified maize cob

J.C Igwe,A.A Abia

doi:10.1590/s0100-46702007000100005

Abstract

The need to clean-up heavy metal contaminated environment can not be over emphasized. This paper describes the adsorption isotherm studies of Cd (II), Pb (II) and Zn (II) ions from aqueous solution using unmodified and EDTA-modified maize cob. Maize cob was found to be an excellent adsorbent for the removal of these metal ions. The amount of metal ions adsorbed increased as the initial concentration increased. Also, EDTA - modification enhanced the adsorption capacity of maize cob probably due to the chelating ability of EDTA. Among the three adsorption isotherm tested, Dubinin-Radushkevich gave the best fit with R² value ranging from 0.9539 to 0.9973 and an average value of 0.9819. This is followed by Freundlich isotherm (Ave. 0.9783) and then the Langmuir isotherm (Ave. 0.7637). The sorption process was found to be a physiosorption process as seen from the apparent energy of adsorption which ranged from 2.05KJ\mol to 4.56KJ\mol. Therefore, this study demonstrates that maize cob which is an environmental pollutant could be used to adsorb heavy metals and achieve cleanliness thereby abating environmental nuisance caused by the maize cob.

Highlights

The impact of heavy metal release into our environment is increasing as a result of population explosion, haphazard rapid urbanization, industrial and technological expansion, increased energy utilization and waste generation from domestic and industrial sources
We report the results of the adsorption isotherm studies for the bioremediation of Cd (II), Pb (II) and Zn (II) ions on unmodified and Ethylenediamine tetracetic acid (EDTA) modified maize cob
The activated and treated maize cob was EDTA-modified by a modified method previously reported [22]

Summary

Introduction

The impact of heavy metal release into our environment is increasing as a result of population explosion, haphazard rapid urbanization, industrial and technological expansion, increased energy utilization and waste generation from domestic and industrial sources. These have rendered many waters unwholesome and hazardous to man and other living resources [1]. Lead for instance, can interfere with enzyme activities and formation of red blood cells It can affect nerves and brain at low concentration. Heavy metals such as mercury, cadmium and chromium can bioaccumulate and through the food chain to toxic levels in man. Cadmium is responsible for kidney tubular impairment and osteomalacia [3]

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Results

Conclusion