The strain HB-4 was screened from heavy metal contaminated soil

identified as Serratia marcescens via 16S rDNA sequence analysis

and had a strong tolerance for Cd2+. This strain can grow well when the concentration of Cd2+ was up to 300 mg·L-1 and in that case the maximum adsorption capacity of Cd2+ was (154.7±0.9) mg·g-1. The effect factors of the adsorption of Cd2+ by using HB-4 were investigated

including the initial concentration of Cd2+

pH

salt concentration and coexisting ions. The results showed that there was no difference in the adsorption capacity when pH was ranged from 3.0 to 8.0. The same results can also be obtained at 8.0% NaCl solution and the removal efficiency were 98.7%±0.2% (Pb2+)

44.6%±0.6% (Zn2+)

52.7%±0.1% (Cu2+) and 64.2%±0.3% (Cd2+)

respectively

when Pb2+

Zn2+

Cu2+ and Cd2+ coexisted in solution. According to desorption experiment

the desorption rate was less than 2% and it demonstrated that HB-4 performed the best on adsorption of Cd2+. The distribution of intra-and extracellular cadmium was studied

as well as the results from SEM

XPS and FTIR. It suggested that the mechanism of adsorption of Cd2+ by HB-4 contained extracellular adsorption and intracellular uptake.