Biosorption and preconcentration of lead and cadmium on waste Chinese herb Pang Da Hai

The biosorption behavior of the solid waste Chinese herb Pang Da Hai (seeds of Sterculia lychnophera Hance) was studied as a sorbent for trace lead and cadmium. The solid waste Chinese herb Pang Da Hai has good sorption and desorption properties for Pb and Cd. The sorbed waste Chinese herb Pang Da Hai was both easily eluted with 0.1 mol l(-1) HNO(3) and easily digested with concentrated HNO(3). The extent of adsorption depends on pH, metal concentration, substrate concentration and the presence of interfering ions. The adsorption capacities were found to be 27.1 and 17.5 mg g(-1) for Pb and Cd. The relative standard deviation of the metal uptake experiment was found to be less than 10% for Pb(II) and Cd(II) using 100 microg l(-1) of metal ions and 20 mg substrate. Based on above, an ecofriend and low cost method for Cd and Pb preconcentration and determination with flame atomic absorption spectrophotometry was developed. The method was validated by the analysis of a standard reference material (GBW 08301). The results agree with those quoted by manufactures. It was used for 90-fold preconcentration of Cd and Pb from tap water and river water samples followed by flame atomic absorption spectroscopic (FAAS) determination with satisfactory results.