ADSORPTION OF HEAVY METALS FROM AQUEOUS SOLUTION ONTO ACTIVATED CARBON DERIVED FROM Balanites aegyptiaca SEEDS

ABSTRACT

A series of batch experiments were conducted in order to investigate the feasibility of Balanites aegyptiaca seeds based activated carbon as compared with industrial activated carbon for the removal of chromium, lead, copper, cobalt, nickel, cadmium and manganese from aqueous solution by the adsorption process within 30 to 150 min contact time. The Activated samples were prepared using Zinc chloride and tetraoxophosphate V acid. Investigation was carried out by studying the influence of initial solution pH, adsorbent dosage and initial concentration of the various metal ions. The results obtained showed that the activated carbon of Balanites aegyptiaca seeds studied had relatively high adsorption capacities for these heavy metal ions. The percentage removal was Cr (VI), (64%, 70% and 71%), Cu (II), (75%,78% and 80%), Pb (II), (86%,69% and 69.61%), Cd (II), (69%, 72% and 69%), Ni (II), (72%, 78% and 77%), Co (II), (66%, 68% and 69%) and Mn (III), (80%, 79% and 77.8%) respectively. Adsorption equilibrium was established in 90 minutes for the heavy metal ions. The equilibrium data fitted pseudo- second order out of pseudo first order, pseudo second order, Natarajan and Khalaf and Elovich model tested. The investigation also showed that the adsorbents can effectively remove metal ions from similar wastewater and aqueous media

CHAPTER ONE

1.0        INTRODUCTION

1.1        Background of the Study

With rapid increase in global industrial activities, the pollution derived from uncontrolled substances containing heavy metals such as chromium, lead, copper and zinc has become a serious problem (Srivestava, Tyagi and Paul, 2010). Numerous metal ions such as that of chromium, copper, lead, manganese, mercury, cadmium, are known to be significantly toxic (Luqman, Najua, Zawani and Suraya, 2008). These heavy metals have harmful effect on human physiology and other biological systems when they exceed tolerance levels. It has been estimated that the toxicity due to metallic discharge annually into the environment far exceeds the

combined total toxicity of all radioactive, and organic waste released into source of drinking water (Badmus, Audu and Anyata, 2007; Abdul-salam and Adekola, 2005). The most widely used methods for removing heavy metals from wastewaters includes chemical precipitation, complexation, solvent extraction, membrane processes, ion exchange, and ultra filtration (Gupta,

Jain, Ali and Saini, 2003). However, most of these methods are either economically prohibitive, generation of secondary wastes (sludge) or too complicated for the treatment of metals (Jang, Seo and Bishop, 2005).

Consequently, there is the need to urgently find new technologies or materials for removing heavy metal ions from wastewater. However, adsorption processes have shown many advantages over the physicochemical methods. They are quite selective, effective, efficient, regenerative, no sludge formation, economical and above all they can remove various levels of soluble heavy metals in solution (Jihyun – Lim, Hee-Man Kang, Lee–Hyung and Seok-Ohko, 2008).

1.2       Scope of the Study

This research uses Balanites aegyptiaca seeds to prepare activated carbon. The adsorbent prepared was used for it´s adsorptive feasibility on chromium, lead, copper, cadmium, cobalt, nickel and manganese. The kinetics of these metal adsorptions on the seeds used was studied.

1.3       Justification of the Study

Heavy metal pollution has become one of the most serious environmental problems today. Billions of gallon of wastewater containing heavy metals are produced each year by textile industries, metallurgical plants, gas operations, industries, washing operations and other processes. Most of the chemical methods used in cleaning up these heavy metals are not effective. Micro-organisms have been used extensively in cleaning of heavy metals in the environment (adsorption) but plants have not been used extensively in removing heavy metals from the environment. This justifies the use of Balanites aegyptiaca seeds with surface modification to improve their metal removal performance and to add to their economic values, reduce the cost of waste disposal and most importantly to provide a potentially inexpensive alternative to the existing commercial activated carbon.

1.4        Aim and Objectives of the Study

The research is aimed at preparing Activated charcoal from Balanites aegyptiaca seeds using zinc chloride (ZnCl2) and tetraoxophosphoric acid (H3PO4) as activating agents, and at the same time using the prepared activated carbon to adsorb chromium, lead, copper, cadmium, cobalt, nickel and manganese from aqueous solution.

The objectives of this research were to:

(1) Prepare the activated carbon using Balanites aegyptiaca seeds

(2) Determine the Ash content of the Balanites aegyptiaca seeds

(3) Characterized the Activated carbon using bulk density, % burn off, % carbon yield,   pH and conductivity

(4) Evaluate the Adsorption capacity of activated carbon from Balanites aegyptiaca seeds to ascertain it´s carbon content effect on the heavy metal removal

(5) Study the Adsorption kinetics using pseudo first order, pseudo second order, Elovich model and Nataranja and Khalaf first order equation.

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