Removal of Orange G Dye by Manganese Oxide Nanostructures

Two types of manganese oxide were investigated for the removal/degradation of Orange G (OG) dye in aqueous solution. One manganese oxide (pyrolusite) was obtained commercially and the other (birnessite) was prepared according to the polyol method by means of the oxidation of MnII hydroxide by H2O2. Both materials were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption at 77 K. The effects of agitation time, pH, and MnO2 dose on the degradation of OG by the birnessite and pyrolusite were evaluated. Approximately 90 and 99% decoloration of OG (10 mg L-1) was obtained after 30 min of stirring with 0.20 g L-1 of birnessite or pyrolusite, respectively. The decoloration and increased intensity of absorbance bands in the UV-visible spectrum were indicative of a degradation process that followed pseudo-first order kinetics. The findings demonstrated the high efficiency of different types of manganese oxides for removal of this organic pollutant from waters.

本研究针对水溶液中橙G（Orange G，OG）染料的去除与降解效果，考察了两种氧化锰材料的应用潜力。其中一种氧化锰为市售软锰矿（pyrolusite），另一种水钠锰矿（birnessite）则通过多元醇法，以过氧化氢（H₂O₂）氧化二价锰氢氧化物制备得到。采用X射线衍射（X-ray diffraction, XRD）、红外光谱（infrared spectroscopy, IR）、扫描电子显微镜（scanning electron microscopy, SEM）以及77 K下的氮气吸附-脱附法对两种材料进行了表征。考察了搅拌时间、溶液pH值以及二氧化锰投加量对水钠锰矿与软锰矿降解橙G的影响。当投加量为0.20 g·L⁻¹时，分别使用水钠锰矿与软锰矿搅拌30分钟后，对初始浓度为10 mg·L⁻¹的橙G溶液的脱色率分别可达约90%与99%。紫外-可见光谱中吸光度带的脱色行为与强度变化特征表明，该降解过程遵循准一级动力学规律。研究结果证实，不同类型的氧化锰均可高效去除水体中的该类有机污染物。