Efficient and Rapid Removal of Nickel Ions from Electroplating Wastewater Using Micro-/Nanostructured Biogenic Manganese Oxide Composite

Manganese oxides reportedly exhibit pronounced adsorption capacities for numerous heavy-metal ions owing to their unique structural properties. Herein, a biogenic manganese oxide (BMO) composite was developed and used to remove Ni ions from Ni2+-containing electroplating wastewater. The formation of BMO and the micro-/nanoscale fine microstructure were characterized via scanning/high-resolution transmission electron microscopies and X-ray diffraction assays. Under the optimized conditions, with an adsorption temperature of 50 °C, pH 6, the BMO composite showed a 100% removal efficiency within a rapid equilibrium reaction time of 20 min towards an initial Ni2+ concentration of 10 mg L−1 and a remarkable removal capacity of 416.2 mg g−1 towards an initial Ni2+ concentration of 600 mg L−1 in Ni-electroplating wastewater. The pseudo-second-order equation was applicable to sorption data at low initial Ni2+ concentrations of 10–50 mg L−1 over the time course. Moreover, Freundlich isotherm models fitted the biosorption equilibrium data well. Fourier-transform infrared spectroscopic analysis validated that the removal capacity of the BMO composite was closely associated with structural groups. In five continuous cycles of adsorption/desorption, the BMO composite exhibited high Ni2+ removal and recovery capacities, thereby showing an efficient and continuous performance potential in treating Ni2+-containing industrial wastewater.