No abstract

In this work the use of chestnut shell as an adsorbent of the cadmium ions present in some industrial wastewaters was studied. Various pre-treatments were performed to increase the sorption capacity of the material and simultaneously avoid the coloration of the water due to soluble polyphenols. The effect of the pre-treatments was evaluated using the pre-treated material to adsorb Cd 2+ ions under specified conditions. The influence of the pre-treatment agent (water, sodium hydroxide, sulphuric acid, formaldehyde and sodium chloride) and of the operating conditions (temperature and time) on the sorption capacity of the pre-treated material was analysed using the pseudo-second order kinetic model. Equilibrium sorption capacities from 2.50 to 7.11 mg Cd 2+ /g oven-dried shell were achieved. The optimal results were obtained by pre-treating the shell with a 4% NaOH aqueous solution for 24 h at room temperature. Under these conditions an adsorption percentage of 98.6% was obtained and 80% of the maximum sorption capacity was reached in less than 1 h. X-ray photoelectron spectrometry (XPS) surface measurements were performed to compare the chemical composition of the pre-treated materials. Additionally, FTIR and XPS were used to analyze the functional groups involved in Cd binding.