Abstract: A cadmium-resistant endophytic bacterium was isolated from reed rhizosphere and identified as Chryseobacterium rhizosphaerae SH-1. The minimum inhibitory concentration of Cd2+ was up to 450 mg/L, and microscopic observation showed that the cell surface adsorption mechanism was involved in the removal process of Cd2+. FTIR analysis showed that O-H, N-H, C-H, N≡C-,-NO2, C=S, P=O and S-O were all involved in the adsorption. The strain was immobilized using sodium alginate. The effects of contact time, pH and Cd2+ initial concentrations on Cd2+ adsorption by immobilized beads were investigated and the adsorption properties were also explored through adsorption kinetics. The result showed that the removal efficiency was over 93.24% while the initial Cd2+ concentration of 100 mg/L, contact time of 480 min and pH of 5.0. The isothermal adsorption characteristics of Cd2+ could be described by Langmuir isothermic adsorption model with the maximum theoretical adsorption capacity of 187.41 mg/g. On the other hand, the pseudo-second-order model well fitted the kinetic process of Cd2+ adsorption by immobilized SH-1 and the theoretical equilibrium adsorption capacity was 51.02 mg/g. The results showed that the immobilized endophytic bacterium SH-1 could be a great potential biosorbent.

Key words: endophytic bacterial, sodium alginate, immobilize, adsorption, cadmium ion