Solvent extraction of nickel ions from electroless nickel plating wastewater using synergistic green binary mixture of D2EHPA-octanol system

A study on the synergistic green solvent extraction of nickel ions from real electroless nickel plating wastewater using an organic phase containing a binary mixtures of Di (2-ethylhexyl) phosphoric acid (D2EHPA) and octanol in palm oil was conducted. The effects of diluent composition, synergist, carrier and stripping agent types and its concentrations were experimentally investigated and the optimum conditions were determined. Results revealed that both D2EHPA and octanol acted as a carrier and synergist, respectively. A significant synergistic effect occurred when the octanol helped destroy the dimer structure of D2EHPA for cation exchange mechanism with nickel ions, hence improving the nickel ions extraction up to 90% with the maximum distribution ratio of 8.8 under optimum condition of 0.7M D2EHPA and 15% (v/v) octanol in palm oil. Afterwards, the stripping experiment showed that nickel ions could be recovered from the loaded mixture of carrier using 1.0M nitric acid solutions. Besides, the slope analysis method showed that the nickel ions were extracted from weak acidic electroplating feed solution as nickel-D2EHPA-octanol complex and recovered as nickel nitrate complex in the stripping phase. Thus, it can be concluded that the green synergistic formulation containing binary mixtures of D2EHPA-octanol system is one of the promising approaches as well as a green and efficient separation method for nickel ions extraction from the real electroless nickel plating wastewater.