Removal of Ni(II) from strongly acidic wastewater by chelating precipitation and recovery of NiO from the precipitates.

• Ni(II) was efficiently removed from strongly acidic wastewater using DDTC. • Dithiocarbamate groups of DDTC react with Ni(II) to form DDTC Ni precipitates. • High-purity NiO can be obtained by calcination of DDTC Ni precipitates. • NO 2 , CS 2 , H 2 O, CO 2 , and SO 2 were released during the calcination process. Strongly acidic wastewater produced in nonferrous metal smelting industries often contains high concentrations of Ni(II), which is a valuable metal. In this study, the precipitation of Ni(II) from strongly acidic wastewater using sodium dimethyldithiocarbamate (DDTC) as the precipitant was evaluated. The effects of various factors on precipitation were investigated, and the precipitation mechanism was also identified. Finally, the nickel in the precipitates was recovered following a pyrometallurgical method. The results show that, under optimised conditions (DDTC:Ni(II) molar ratio = 4:1; temperature = 25 °C), the Ni(II) removal efficiency reached 99.3% after 10 min. In strongly acidic wastewater, the dithiocarbamate group of DDTC can react with Ni(II) to form DDTC Ni precipitates. Further recovery experiments revealed that high-purity NiO can be obtained by the calcination of DDTC Ni precipitates, with the nickel recovery efficiency reaching 98.2%. The gas released during the calcination process was composed of NO 2 , CS 2 , H 2 O, CO 2 , and SO 2. These results provide a basis for an effective Ni(II) recovery method from strongly acidic wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]