Galbreath K C, Toman D L, Zygarlicke C J, Huggins F E, Huffman G P, Wong J L
Energy and Environmental Research Center, University of North Dakota, Grand Forks, USA.
J Air Waste Manag Assoc. 2000 Nov;50(11):1876-86. doi: 10.1080/10473289.2000.10464230.
The chemical speciation of Ni in fly ash produced from approximately 0.85 wt % S residual (no. 6 fuel) oils in laboratory (7 kW)- and utility (400 MW)-scale combustion systems was investigated using X-ray absorption fine structure (XAFS) spectroscopy, X-ray diffraction (XRD), and acetate extraction [1 M NaOAc-0.5 M HOAc (pH 5) at 25 degrees C]-anodic stripping voltammetry (ASV). XAFS was also used to determine the Ni speciation of ambient particulate matter (PM) sampled near the 400-MW system. Based on XAFS analyses of bulk fly ash and their corresponding acetate extraction residue, it is estimated that > 99% of the total Ni (0.38 wt %) in the experimentally produced fly ash occurs as NiSO4.xH2O, whereas > 95% of the total Ni (1.70 and 2.25 wt %) in two fly ash samples from the 400-MW system occurs as NiSO4.xH2O and Ni-bearing spinel, possibly NiFe2O4. Spinel was also detected using XRD. Acetate extracts most of the NiSO4.xH2O and concentrates insoluble NiFe2O4 in extraction residue. Similar to fly ash, ambient PM contains NiSO4.xH2O and NiFe2O4; however, the proportion of NiSO4.xH2O relative to NiFe2O4 is much greater in the PM. Results from this and previous investigations indicate that residual oil ash produced in the 7-kW combustion system lack insoluble Ni (e.g., NiFe2O4) but are enriched in soluble NiSO4.xH2O relative to fly ash from utility-scale systems. This difference in Ni speciation is most likely related to the lack of additive [e.g., Mg(OH)2] injection and residence time in the 7-kW combustion system.
利用X射线吸收精细结构（XAFS）光谱、X射线衍射（XRD）和醋酸盐萃取[25℃下1M NaOAc - 0.5M HOAc（pH 5）] - 阳极溶出伏安法（ASV），研究了实验室规模（7kW）和公用事业规模（400MW）燃烧系统中由约0.85wt%硫残留（6号燃料）油产生的粉煤灰中镍的化学形态。XAFS还用于测定在400MW系统附近采集的环境颗粒物（PM）中的镍形态。基于对大量粉煤灰及其相应醋酸盐萃取残渣的XAFS分析，估计实验产生的粉煤灰中总镍（0.38wt%）的>99%以NiSO4·xH2O形式存在，而400MW系统的两个粉煤灰样品中总镍（1.70和2.25wt%）的>95%以NiSO4·xH2O和含镍尖晶石（可能是NiFe2O4）形式存在。利用XRD也检测到了尖晶石。醋酸盐萃取出大部分NiSO4·xH2O，并将不溶性NiFe2O4浓缩在萃取残渣中。与粉煤灰类似，环境PM中含有NiSO4·xH2O和NiFe2O4；然而，PM中NiSO4·xH2O相对于NiFe2O4的比例要大得多。本次及先前研究的结果表明，7kW燃烧系统中产生的残油灰缺乏不溶性镍（如NiFe2O4），但相对于公用事业规模系统的粉煤灰而言，其可溶性NiSO4·xH2O含量更高。镍形态的这种差异很可能与7kW燃烧系统中缺乏添加剂[如Mg(OH)2]注入和停留时间有关。
