生物炭吸附雨水径流难生物降解有机氮效能及机制

有机氮（ON）在雨水径流氮素污染中起关键作用，但多数研究只关注可生物降解有机氮的生物转化去除，忽略了占比较高的难生物降解有机氮.以生物炭作为吸附剂，探究其对雨水径流典型难生物降解有机氮（吲哚）的吸附效能及机制.结果表明，原始生物炭对吲哚有较高的单位吸附量（45 mg·g^-1），生物炭投加浓度为0.4 g·L^-1时其表面平均吸附位点利用度最高.H₂O₂和NaOH改性生物炭对吲哚的吸附量是原始生物炭的1.3倍和1.6倍，吸附机制包括疏水相互作用、氢键和π-π电子供体-受体（π-π EDA）作用，以疏水相互作用为主，其中H₂O₂改性通过增加生物炭表面含氧官能团来加强氢键和π-π EDA作用，而NaOH改性生物炭通过大幅提高生物炭比表面积来加强疏水相互作用，故NaOH改性吸附效果更优.综上，生物炭对难生物降解有机氮具有较强去除作用，通过NaOH改性还能大幅提高效率，故在雨水径流氮素污染较高的地区把NaOH改性生物炭作为生物滞留池中的填料有着极大的应用潜力.

Effect and Mechanism of Biochar Adsorption on Unbiodegradable Organic Nitrogen in Stormwater Runoff

Organic nitrogen (ON) plays a key role in the nitrogen pollution of stormwater runoff; however, most studies only focus on the biotransformation removal of biodegradable ON, ignoring the unbiodegradable ON that occupies a high proportion of ON. In this study, biochar was used as adsorbent to investigate the mechanism and effect on the adsorption of typical unbiodegradable organic nitrogen (indole) in stormwater runoff. The results revealed that biochar had high unit adsorption on indole (45 mg·g^-1), and the dosage concentration of 0.4 g·L^-1 had the highest utilization of average adsorption sites. The indole adsorption after H₂O₂- and NaOH-modified biochar were 1.3 and 1.6 times that of the original biochar; the adsorption mechanism included hydrophobic interactions, hydrogen bonds, and π-π electron-donor-acceptor (π-π EDA) interactions; and hydrophobic interactions were the most important. H₂O₂-modified biochar strengthened the role of hydrogen bonds and π-π EDA by increasing the oxygen-containing functional groups of biochar, whereas NaOH-modified biochar strengthened the hydrophobic interactions by greatly increasing the specific surface area of biochar; thus, the adsorption of indole by NaOH-modified biochar was better. Therefore, biochar had a high removal on unbiodegradable ON, and the effect could be greatly improved by NaOH-modified biochar, which has considerable application potential in areas with high nitrogen pollution in stormwater runoff.