Construction of K and Tb Co-doped MnO2 nanoparticles for enhanced oxidation and detoxication of organic dye waste.

Developing low-cost and efficient materials for dye pollutant removal under mild condition remains a great challenge. Here K+ and Tb3+ co-doped porous MnO2 (K-Tb-MnO2) nanoparticles with tailored properties including crystal structure, surface area and catalytic activity have been synthesized. Experimental results reveal that K-Tb-MnO2 nanoparticle has higher specific surface area, Mn3+ content and surface oxygen vacancies than pristine MnO2 nanoparticle and single-doped MnO2 materials, showing the uniqueness of dual-doped metal ions. Using methyl blue (MB) as a model pollutant, its removal efficiency by K-Tb-MnO2 nanoparticles within 5 min is 93.6%, which is 18, 8.3, and 2.9 times higher than that of MnO2, K-MnO2, and Tb-MnO2 nanomaterials, respectively. Oxalic acid triggered MnO2 material dissolving assay and FT-IR spectrum suggested that remarkable performance of K-Tb-MnO2 nanoparticle toward MB removal can be attributed to a combined effect of adsorption (16% MB removal) and catalytic degradation (84% MB removal). Moreover, K-Tb-MnO2 nanoparticle mediated MB degradation is demonstrated to be a combination of non-radical oxidation by Mn3+ and radical-participated degradation, with 1O2 as the main species. And the intermediates and pathways of MB degradation were studied by liquid chromatography-mass spectrometry. Importantly, cell viability experiment suggests that the toxicity of MB dye could be efficiently alleviated after the treatment with K-Tb-MnO2 nanoparticle. These results demonstrate the great potential of the novel K-Tb-MnO2 particles to be used as a highly effective nanomaterials to reduce the risk of dye wastes toward the environment and human health.