Novel multi-metal containing MnCr catalyst made from manganese slag and chromium wastewater for effective selective catalytic reduction of nitric oxide at low temperature

Abstract

Abstract The disposal of manganese slag and chromium electroplating wastewater is a difficult problem worldwide. These wastes contain various transition metals, such as Mn, Cr, Fe, Ni and Cu. Thus, these wastes are also potential resources. In this work, a novel catalyst for selective catalytic reduction of nitric oxide was synthesized with the synergetic utilization of manganese slag and chromium wastewater for the first time. The catalyst was feathered by a multi-metal containing amorphous and crystal MnCr oxides. As a result, the manganese slag after ammonia activation increased the removal of nitric oxide from 25 to 61% at a temperature as low as 150 °C. The nitric oxide removal further increased to 97% after chromium wastewater precipitation. The enhanced efficiency lasted for more than 900 min. The results of X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy revealed that chromium wastewater increased the amount of amorphous Mn4+, which coupled to Cr3+. Moreover, the Ni, Fe and Cu in Mn slag and Cr wastewater were incorporated into the coupling, further enhancing the amount of acid sites and low-temperature activity. This catalyst was even more active than a reagent-synthesized MnCr catalyst. Therefore, the present research developed a new strategy to recycle transition metal-containing wastes and to synthesize catalysts for sustainable development.