Competitive Removal of Lead Copper and Cadmium from Aqueous Solution onto Tea Waste

Abstract

Experiments were carried out to use tea waste to remove lead, copper and cadmium ions from aqueous solutions in single, binary and ternary systems. Batch biosorption studies were carried out to examine the biosorption capacity, pH value, agitation speed, and metal ions concentration. The biosorption process showed that the tea waste was an effective biosorbent for metal ions removal with the initial concentrations of 50 mg/l. The residual concentration of Pb (II), Cu (II) and Cd (II) were determined using Atomic Absorption Spectrophotometer. The optimum pH found for removal Pb (II) and Cd (II) ion occurred at pH 5 while for Cu (II) ion occurred at pH of 6 respectively. Zeta potential measurements for tea wastes indicated that the negative sites of tea waste gave the greatest zeta-potential value at pH 5. The effect of functional groups of tea waste was found by Fourier transformation infrared spectroscopy analysis. The results showed that the biosorption was a complex process and depended on the number and type of active groups. Carboxyl, amino, aromatic, hydroxyl and sulfonic groups were involved in this process. Pb(II) made a greater change in the functional groups of tea waste due to high affinity to this metal. The removal efficiencies for metal ions decreased in binary and ternary systems as compared with single system. The sequence for metal ions removal in single system was Pb > Cd > Cu; while in binary and ternary was Pb > Cu > Cd. In addition, the experimental data indicated that the biosorption of Pb(II), Cu(II) and Cd(II) ions fitted well the Langmuir isotherm for single system and extended Langmuir for binary and ternary system. Kinetic studies showed that a pseudo second order model was more suiTable. than the pseudo first order model.