A rhizobial isolate was recovered from the root nodule of the faba bean (Vicia faba L.) grown in sludgecontaminated
fields in Upper Egypt. The isolate was identified as Rhizobium leguminosarum bv. viciae on
the bases of phenotypic characteristics and sequences of the gene encoding 16S rRNA. The isolate was
resistant to heavy metal stress in decreasing order Ba2þ (80 ppm), Zn2þ (70 ppm), Co2þ (50), Al3þ
(40 ppm), Ni2þ (30 ppm), and Cd2þ (10 ppm). The rhizobial isolate was used as an efficient biosorbent for
Cd2þ and Co2þ removal from aqueous solutions. The maximum adsorption capacities for Cd2þ and Co2þ
biosorption calculated from the Langmuir adsorption isotherm were 135.3 and 167.5 mg g1, respectively.
The adsorption isotherm for both heavy metals fit well with the Langmuir isotherm rather than the
Freundlich model with correlation coefficient (r2>0.98). This study indicates that the R. leguminosarum
bv. viciae isolate STDF-Egypt19 can be useful as an inexpensive and efficient bioremediation technology
to remove and recover heavy metal ions from an aqueous solution.