Recycling of the anode from spent Ni-MH batteries for synthesis of the lanthanide oxysulfide/oxysulfate compounds used in an oxygen storage and release system

In this work, lanthanide oxysulfide/oxysulfate compounds, denominated as an oxygen storage and release system, have been synthesized from the anode electrodes of spent Ni-MH batteries. The rare earth metals have recovered by means of chemical precipitation as a mixture of La-2(SO4)(3), Ce-2(SO4)(3), and Nd-2(SO4)(3). The synthesis of (La.Nd)O2S.CeO2 have been carried out by subjecting a mixture of La-2(SO4)(3), Ce-2(SO4)(3), and Nd-2(SO4)(3) to a heat treatment in a reducing atmosphere up to 1000 degrees C. The (La Nd)O2SO4.CeO2 compounds have been obtained after thermal treatment of (La. Nd)O2S.CeO2 in a synthetic air atmosphere. The oxysulfide/oxysulfate compounds have been subjected to thermal cycles, respectively, in synthetic air as well as in an N-2-CO atmosphere. The thermogravimetric plot (TG) for (La.Nd)(2)O2S.CeO2 shows a mass gain of 14.98% w/w in a temperature range of 300-550 degrees C, which is due to the oxidation of (La.Nd)(2)O2S.CeO2 to (La.Nd)(2)O2SO4CeO2, where 2 mol of O-2 are added. Likewise, in the (La.Nd)(2)O2SO4CeO2 thermogravimetric plot, a mass loss of 17.16% w/w is observed in the range of 500-750 degrees C. This loss of mass can be associated with output of 2 mol of O-2 forming again the (La.Nd)(2)O2S.CeO2. The transformation of the (La.Nd)(2).O2S.CeO2 to (La.Nd)(2)O2SO4CeO2 causes an increase in the macropores. (C) 2014 Elsevier B.V. All rights reserved.