Wu Yajing, Chen Baoliang
Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
Sci Total Environ. 2019 Nov 15;691:595-604. doi: 10.1016/j.scitotenv.2019.06.501. Epub 2019 Jul 2.
Fulvic acid (FA) in soil ubiquitously affected the long-term benefits of biochars as soil amendments. The sorption of ionizable organic pollutants on biochars was complicated by FA because of the presence of ionic groups. To investigate the effect of FA coating on the interaction between biochars and 4-chlorophenol (4-CP), sorption isotherms at pH 4.0 and 12.0 and pH-sorption edge curves were generated. The biochars derived from platane wood were pyrolyzed at 300°C, 500°C and 700°C, resulting in low-, medium- and high-temperature biochars, respectively. The FA coating increased the surface area of the low-temperature biochar but decreased those of the medium- and high-temperature biochars. After coating biochars with FA, the aromaticity and the surface charge of the biochars decreased, but the content of oxygen-containing functional groups, especially carboxyl groups, on the biochar surfaces increased. The results from the sorption isotherm and pH-sorption edge curves showed that FA coating inhibited the sorption under alkaline conditions but did not change the sorption under acidic conditions, which indicated that coating by FA not only occupied the sorption sites but also strengthened the hydrogen bonding between 4-CP and biochars. As determined by characterization of biochars before and after coating, the number of carboxyl groups on the biochar surface increased after coating, which participated in hydrogen bonding with the hydroxyl groups of non-dissociated 4-CP. This research indicated that FA in the soil influenced the interaction between biochar with 4-CP, and the influences varied mainly due to the formation of hydrogen bonds at different pH values. This study could help us better understand the environmental behavior of biochar after aging, and provided a reference for sustainable utilization of biochar.
土壤中的富里酸（FA）普遍影响生物炭作为土壤改良剂的长期效益。由于离子基团的存在，FA使可电离有机污染物在生物炭上的吸附变得复杂。为了研究FA包覆对生物炭与4-氯苯酚（4-CP）相互作用的影响，生成了pH 4.0和12.0时的吸附等温线以及pH-吸附边缘曲线。由悬铃木木材衍生的生物炭在300℃、500℃和700℃下热解，分别得到低温、中温和高温生物炭。FA包覆增加了低温生物炭的比表面积，但降低了中温和高温生物炭的比表面积。用FA包覆生物炭后，生物炭的芳香性和表面电荷降低，但生物炭表面含氧官能团，尤其是羧基的含量增加。吸附等温线和pH-吸附边缘曲线的结果表明，FA包覆在碱性条件下抑制吸附，但在酸性条件下不改变吸附，这表明FA包覆不仅占据了吸附位点，还加强了4-CP与生物炭之间的氢键。通过对包覆前后生物炭的表征确定，包覆后生物炭表面羧基数量增加，其与未解离的4-CP的羟基形成氢键。本研究表明，土壤中的FA影响生物炭与4-CP之间的相互作用，且这种影响主要因不同pH值下氢键的形成而有所不同。该研究有助于我们更好地理解老化后生物炭的环境行为，并为生物炭的可持续利用提供参考。
