ABSTRACT The removal of heavy metals from industrial waste streams has become one of the most important applications in wastewater treatment in terms of protecting public health and environment. The recovery of metals present in the industrial effluents by adsorption onto natural materials constitutes a technological option increasingly studied throughout the world. However, the implementation of such process on an industrial scale requires the use of adsorbents easily available and inexpensive. Clay in these two forms natural and activated answers very well to these two requirements. The present research aimed the study of the capacity of fixing of cadmium present in aqueous solution, by two types of clay: natural and activated. The adsorption capacity of adsorbent was investigated using batch experiments. The influence of pH, temperature and adsorbent dose were investigated and the experimental data obtained were evaluated and fitted using adsorbent equilibrium isotherms. Adsorption isotherms of cadmium onto natural and activated clay were determined and correlated with common isotherm equations such as the Langmuir and Freundlich models. The Langmuir model agrees very well with experimental data. The thermodynamic parameters obtained indicated that the adsorption of cadmium ions onto natural clay was a spontaneous and an endothermic process.
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