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 Fe3+ enhanced the degradation of Ni–citrate complexes and removal of Ni from solutions. The displacement of Ni from recalcitrant Ni–citrate complexes by Fe3+ 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 Fe3+, bioaccumulation and precipitation. P. alcaliphila potentially could be applied in the treatment of effluent containing Ni–citrate complexes.