Cadmium and copper adsorption on bentonite: effects of pH and particle size

Lúcia Helena Garófalo Chaves,Gilvanise Alves Tit

doi:10.1590/s1806-66902011000200004

Abstract

Reactions of heavy metals with clay minerals are important in determining metal fates in the environment. However, the adsorption process of these metals by the bentonite has been extensively investigated. The objectives of this work were to assess the ability of bentonite clay to adsorb cadmium and copper and to study the effects of pH and particle size upon these metals adsorption. Adsorption isotherms were obtained from batch adsorption experiments, with increasing cadmium and copper concentrations (5-200 mg L-1). To find out the effects of pH and particle size on adsorption, the experiments were conducted at pH 4; 5 and 6 using particles sizes of < 0.5 mm and 0.5 to 2.0 mm . The difference between initial and final cadmium and copper concentrations was assumed to be the amount adsorbed by bentonite. The bentonite adsorbed more copper than cadmium, both metals adsorption increased with increasing pH for both particle sizes. No effect of particle size was observed. Experimental data were best fitted to Langmuir model.

Highlights

IntroductionHeavy metals are stable and persistent environmental contaminants since they cannot be degraded or destroyed (LACIN et al, 2005)
Pollution by heavy metals is a serious environmental problem facing life of earth
The adsorption isotherms are important in determining the adsorption capacity of cadmium (Cd) and copper (Cu) by the natural bentonite

Summary

Introduction

Heavy metals are stable and persistent environmental contaminants since they cannot be degraded or destroyed (LACIN et al, 2005). They may be present in soils from a variety of sources and can represent a potential hazard to humans and the environment if they are readily released into soil solution or are other-wise available to biological processes. If such metals are bound up in relatively inert and insoluble compounds, the danger they represent is reduced substantially (SNEDDON et al, 2006). The persistence and mobility of those elements in soils is determined largely by the extent of adsorption by soil particles

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