National Institute of Science & Technology, Palur Hills, Berhampur-761 008, India.
J Hazard Mater. 2010 Jun 15;178(1-3):804-13. doi: 10.1016/j.jhazmat.2010.02.011. Epub 2010 Feb 10.
Particulate matter (PM) emission from residual oil combustion typically consists of carbonaceous material accompanied by inorganic matter notably transition metal sulfates. Often a minor sulfide form is found in the coarse fraction while an oxide form is more common in the fine and ultrafine fractions. A composite comprising of nanoscale nickel ferrite dispersed on carbonaceous matrix has been obtained following liberation of metal sulfates from the fine PM--a novel method of turning harmful particulates into a functional nanocomposite without the need for elaborate preparation using expensive precursors. The nickel ferrite content in the composite varies with the Fe/Ni ratio in particulate, fuel type, and combustion condition. Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific atom pair correlations within the spinel ferrite from which the relative occupancy of the cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II) has strong preference for the octahedral site, while Fe(III) prefers both sites which is consistent with that of an inverted spinel ferrite.
残余油燃烧产生的颗粒物（PM）排放通常由碳质物质伴随着无机物质组成，特别是过渡金属硫酸盐。通常，在粗颗粒中发现少量的硫化物形式，而氧化物形式在细颗粒和超细颗粒中更为常见。在从细颗粒 PM 中释放出金属硫酸盐后，得到了一种由纳米级镍铁氧体分散在碳质基体上组成的复合材料，这是一种将有害颗粒物转化为功能性纳米复合材料的新方法，无需使用昂贵的前体制备复杂的方法。复合材料中的镍铁氧体含量随颗粒物中的 Fe/Ni 比、燃料类型和燃烧条件而变化。这种变化可能导致复合材料表现出不同的物理行为。使用 Fe 和 Ni K 边缘 XAFS 光谱研究了分散铁氧体的详细结构和阳离子分布。在尖晶石铁氧体中，从径向结构函数中识别出具有特定原子对关联的峰，从中可以辨别出阳离子在八面体和四面体位置上的相对占据。结果表明，Ni(II) 强烈倾向于占据八面体位置，而 Fe(III) 则优先占据两个位置，这与反尖晶石铁氧体一致。
