Simultaneous biodegradation of Ni-citrate complexes and removal of nickel from solutions by Pseudomonas alcaliphila.

The objective of this study was to study the simultaneous biodegradation of Ni-citrate complexes and removal of Ni from solutions by Pseudomonas alcaliphila. Adding excess citrate to 1:1 Ni-citrate complexes promoted the degradation of the complexes and removal of Ni. The alkaline pH generated by the metabolism of excess citrate caused partial dissociation of citrate from the Ni-citrate complexes, allowing degradation, and the released Ni was removed through bioaccumulation and precipitation. Addition of Fe(3+) enhanced the degradation of Ni-citrate complexes and removal of Ni from solutions. The displacement of Ni from recalcitrant Ni-citrate complexes by Fe(3+) and subsequent biodegradation of the degradable Fe(III)-citrate complex resulted in complete metabolism of citrate. The almost complete removal of Ni (>98%) can be attributed to the combination of coprecipitation with Fe(3+), bioaccumulation and precipitation. P. alcaliphila potentially could be applied in the treatment of effluent containing Ni-citrate complexes.