Characterization Studies on Adsorption of Lead and Cadmium Using Activated Carbon Prepared from Waste Tyres

The aim of this work was to investigate the utilization of waste tire carbons as a low cost adsorbent for the removal of cadmium and lead ions from an aqueous solution. Surface functional groups would help in getting thorough knowledge about the adsorption capacity of the adsorbent. Thus, activated carbons were prepared from waste rubber tyres and characterized by means of field emission scanning electron microscopy, energy-dispersive X-ray and Fourier transform infrared spectroscopies. The FTIR spectra show that the adsorption peaks are shifted or disappeared and new peaks are formed which was due to the adsorption of lead and cadmium onto the adsorbent surface. It is evident that the characteristic adsorption peak of O-H stretching vibration was shifted from 3900 and 3075 cm-1 for lead and the asymmetrical stretching vibration at 3900 cm-1 was shifted to 3675 cm-1 for cadmium. This shift in peak indicates the interaction between metal ions and –OH groups of adsorbent due to the presence of alcohols, phenols, and carboxylic acid and which shows the decrease of free hydroxyl group content due to the interaction between lead cadmium with –OH groups of the adsorbent. SEM micrograph of adsorbent before adsorption is highly heterogeneous and the surface morphology of the adsorbent is rough. The pores were completely filled with the metal ions after the adsorption of lead and cadmium metals and the pores appear to be smooth. This observation indicates that the metal is adsorbed to the functional groups present inside the pores. From the XRD analysis, the CI index for raw, lead and cadmium loaded activated carbon of waste tyres were found to be 48.91%, 81%, and 54.9% respectively. These values clearly showed the increase in crystalline material present in the adsorbent after the adsorption of metal ions, which was due to the adsorption of metal ions onto the surface of the adsorbent.