Sorption of lead from aqueous solutions by tea wastes.

Environmental contamination by heavy metals has long been a worldwide concern. Tea wastes, having porous surfaces with polar functional groups, could be a good sorbent for removal of Pb(II) from wastewaters. This study aimed to investigate the potential of tea wastes as a sorbent for removal of Pb(II) from solution and the underlying sorption mechanism. Tea wastes showed high removal efficiency for Pb(II) with a short equilibration time and high sorption capacity. The sorptive affinity increased with increasing solution pH and leveled off at about pH 5. Higher temperature led to a higher sorptive affinity, indicating the sorption being an endothermic process. Coexisting metal ions lowered the sorption of Pb(II) with an order of Ag(I)<Cu(II)<Al(III). Fourier transform infrared (FTIR) spectrometer and scanning electron microscopy (SEM) with an X-ray energy dispersion spectroscopy (EDS) accessory were used to examine the underlying mechanism of the Pb(II) sorption. Surface complex formation with carboxylic and amine groups and ion exchanges were observed to regulate the binding of Pb(II) to the tea wastes.