REMOVAL OF SOME HEAVY METALS FROM CONTAMINATED SOILS USING TWO COMPLEXING AGENTS

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REMOVAL OF SOME HEAVY METALS FROM CONTAMINATED SOILS USING TWO COMPLEXING AGENTS

 

CHAPTER ONE

1.0 INTRODUCTION

Industrial development and urbanization have led to increase in the amount of solid wastes frequently discharged into the natural environment. This has increased the amount of many chemical substances in the environment. The chemical substances which are of great environmental interest are the heavy metals. Heavy metals are of special interest because of the major risks they contribute to the environment. They are toxic to humans as well as other organisms; they are released by metal-bearing soil constituents and migrate through the soil solution downward to the water table (Van Oort et al., 2006; Shina and Alok, 2010). The contamination by these metals is a threat to the quality of groundwater, if these metals are not properly treated. Unlike organic compounds that can be biodegraded with time or can be incinerated, metals are robust and remain a potential threat to the environment and human health for a long time (Hong et al., 2002). Soil and sediments are rich in these heavy metals since they are not subject to degradation phenomena. They can easily be suspended or dissolved by surface water, hence become available to plankton, nekton and deposit feeders. The consequence of this is that, they can enter the food chain and become concentrated in fish and other edible organisms (Di Palma and Mecozzi, 2007).

The environmental impact of soil contamination depends not only on the total amount of metals in the soil but mainly on their mobility and availability. This is influenced by leaching and interactions with other components of the ecosystem such as air and water. Soil washing remediation technology is used to remove undesirable contaminants in soil and sediments by dissolving or suspending them in a washing solution (Freeman and Harris, 1995; Moutsatsou et al., 2006; Weihua et al., 2010), and also by concentrating contaminants in small volume of soil through particle size separation (Detzner et al., 1998; McCready et al., 2003). This is based on findings that contaminants tend to bind either physically or chemically to clay, silt or organic soil particles.

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REMOVAL OF SOME HEAVY METALS FROM CONTAMINATED SOILS USING TWO COMPLEXING AGENTS