Adsorption behaviors of strategic W/Mo/Re from wastewaters by novel magnetic ferrite nanoparticles: Adsorption mechanism underlying selective separation.

Purification and recovery of strategic W/Mo/Re from wastewaters face a dual concern for resource recovery and environmental pollution. In this work, a novel manganese ferrite nanoparticles (MFO-NPs) was prepared from the low-grade manganese ore via pyrometallurgical transformation followed by nano sanding. The effects of pH, initial concentration, and reaction time on adsorption behaviors of simplex and mixed W/Mo/Re by MFO-NPs were investigated. Single anion adsorption indicated that molybdate and tungstate adsorption were consistent with the Langmuir isotherm model with the highest adsorption capacities of 41.985 mg/g and 85.61 mg/g, respectively; whereas rhenate was not adsorped. Selective separation indicated that W was firstly separated by MFO-NPs adsorption at pH of 5. After that, Mo was further adsorped by MFO-NPs at pH of 2-4 while Re was kept in the raffinate. The possible selective adsorption mechanism was based on the difference of electrostatic adsorption, polar adsorption, and complexing reaction between MFO-NPs and W/Mo/Re anions, which had various ionic forms under different pH values. Compared with the MFO-NPs prepared by wet chemistry methods, the novel MFO-NPs proposed in this work not only showed satisfactory adsorption capacity but had huge potential for the selective separation of W, Mo, and Re.