Removal of heavy metals (Cd and Pb) from aqueous solutions by adsorption using synthetic tobermorite prepared from bio-municipal wastes as adsorbent

Contamination of waters by discharge of heavy metals such as Lead (Pb), Cadmium (Cd), Zinc (Zn) etc. from various industrial activities poses a great threat to humans, plants and animals, and thus the need for their removal from waste waters. In this work, synthetic tobermorite was prepared using waste soda-lime-silica glass as silica precursor while snail shell ash was used as source of calcium oxide. Several compositions were formulated with varying combination of soda-lime glass and snail shell ash. The bodies were sintered at 950oC in an electric muffle furnace. Analyses such as scanning electron microscopy (SEM/EDS) and Fourier Transform Infra-red Spectroscopy (FT-IR) was used to assess the microstructure and functional groups present in the developed tobermorite. The synthetic tobermorite was further immersed in aqueous solutions containing heavy metals (Pb2+ and Cd2+) whilst parameters such as temperature, contact time, pH, adsorbent dosage, adsorbate concentration were used to assess the performance of the synthetic tobermorite. The results of the morphology shows that the tobermorites possess irregular and spherical shaped grain with coated water films while the EDS shows the presence of Ca and Si with small amount of Al confirming tobermorite while the FT-IR indicates Ca – O – Si and Si – O – Si as main functional groups. The adsorption experiment performed shows the tobermorite is effective in removal of heavy metals (Pb2+ and Cd2+) studied in this work. However, their performance was impaired at increase in temperature above room temperature.