Investigation of NO conversion by different types of sewage sludge chars under low temperature.
Investigation of NO conversion by different types of sewage sludge chars under low temperature.
复制标题
DOI：
10.1016/j.jenvman.2017.12.065
复制
发表时间：
2018-03
影响因子：
8.7
通讯作者：
Wen-yi Deng;A. Yin;Jingchen Ma;Yaxin Su
中科院分区：
文献类型：
--
作者：
Wen-yi Deng;A. Yin;Jingchen Ma;Yaxin Su
制备了不同类型的污泥半焦（S1）、HNO3洗涤半焦（S2）、KOH活化半焦（S3）和H2还原半焦，考察了它们在低温下对NO的转化性能。结果表明，污泥焦的比表面积对NO转化率的影响并不显著。S1的NO转化率高于S2和S3，这是由于S1中铁组分（主要是FeS和Fe2P）的还原作用。高温下的H2还原和随后的冷却气氛（H2或N2）对S1的活性都有很大影响。H2还原可促进铁组分的还原能力，因此S1的NO转化性能也得到显著提高。而S1上的NO转化率在O2存在下下降，这是因为铁组分在O2气氛中更快地被氧化。持续性试验结果表明，S1的活性随时间的延长而降低，但在N2气氛中煅烧后可恢复活性。CO和CO2的程序升温脱附（TPD）曲线表明，CO和CO2的释放主要来自酸酐、酚、酯和羧酸等含氧官能团的分解.此外，通过原位漫反射红外傅里叶变换光谱（DRIFTS）研究了S1−S3吸附和转化NO的机理。结果表明，在50 °C时，吸附在污泥焦上的NO主要转化为NO2，随着温度的升高，NO2逐渐被氧化为硝酸盐。最后，根据实验数据提出了NO转化的可能反应路线。
Different types of sludge chars, i.e. the original (S1), HNO3washed (S2), KOH activated (S3), and H2reduced chars, were prepared to investigate their performances for NO conversion under low temperature. Results indicated that the surface area of the sludge chars did not play key role on NO conversion. S1 showed the higher NO conversion performance than S2 and S3, due to the reducing effect of iron components in S1 (mainly FeS and Fe2P). Both H2reduction at high temperature and the followed cooling atmosphere (H2or N2) have great influences on the activity of S1. H2reduction can promote the reducing capacity of the iron components, thus the performance of S1 for NO conversion was also significantly enhanced. However, NO conversion over S1 decreased in the presence of O2, because the iron components were more quickly oxidized in O2atmosphere. Results of duration tests showed that the activity of S1 decreased with time, but it can be recovered by calcination in N2. The profiles of the temperature programmed desorption (TPD) of CO and CO2indicated that CO and CO2emissions are mainly from the decomposition of oxygen functional groups (OFGs), including anhydrides, phenols, esters, and carboxylic acid. Furthermore, mechanisms of NO adsorption and conversion by S1−S3 were explored by an in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It was found that NO adsorbed on the sludge chars mainly transferred into NO2species at 50 °C, and then NO2species were gradually oxidized to nitrate species with the increase of temperature. Finally, the possible reaction routes for NO conversion were proposed based on experimental data.