去灰分对生物炭理化性质及芳香族污染物吸附的影响  

Impact of deashing treatment on biochar physicochemical properties and sorption mechanisms of aromatic pollutants

作　　者：张萌 吕耀斌 朱一滔 施羲渊 李威[1] 李萍萍[1] 王喜龙[2] ZHANG Meng;LYU Yaobin;ZHU Yitao;SHI Xiyuan;LI Wei;LI Pingping;WANG Xilong(Co-Innovation Center for Sustainable Forestry in Southern China,College of Biology and the Environment,Nanjing Forestry University,Nanjing,210037,China;Laboratory for Earth Surface Processes,College of Urban and Environmental Sciences,Peking University,Beijing,100871,China)

机构地区：[1]南京林业大学南方现代林业协同创新中心,生物与环境学院,南京210037 [2]北京大学城市与环境学院,地表过程分析与模拟教育部重点实验室,北京100871

出　　处：《环境化学》2020年第11期3161-3170,共10页Environmental Chemistry

基　　金：国家自然科学基金(41701555,31700441);中国博士后科学基金(2020M671507);南京林业大学大学生创新训练计划项目(2019NFUSPITP0434)资助

摘　　要：本研究考察极性和非极性芳香族化合物1-萘酚和萘在以小麦秸秆为原料、不同炭化温度(300、400、500℃)下制得的原始生物炭以及去灰分处理后生物炭上的吸附,以探究生物炭的矿物组分对其吸附芳香族污染物的影响机制.结果表明,去灰分后,萘和1-萘酚在生物炭上的有机碳标化吸附分配系数Koc普遍增大(除了1-萘酚在300℃生物炭上的Koc值减小),吸附等温线的非线性程度增强,主要是由于去灰分改变生物炭的组成结构和表面性质.去灰分后,生物炭的整体极性略有提高,而表面极性明显降低,表明矿物组分影响生物炭中极性官能团的空间分布,有助于极性官能团在生物炭表面的向外暴露.与脂肪碳相比,原始和去灰分生物炭中的芳香碳组分对于萘和1-萘酚是更为有效的吸附位点,其与这些芳香族化合物间的疏水作用是主导吸附机制.去灰分潜在增加了生物炭的芳香碳含量,增强其芳香性;同时减少生物炭表面极性官能团的暴露,使得原来被屏蔽的疏水吸附域外露,促进与目标化合物的疏水作用,导致吸附强度(Koc)增大.除了疏水作用,1-萘酚结构中的极性官能团—OH能与矿物含氧表面或极性官能团形成氢键作用,对其在低温生物炭(300℃)上的吸附有重要贡献,去灰分后氢键作用减弱,导致吸附强度(Koc)下降.这说明生物炭中的无机矿物一方面可以通过特定作用机制有效结合芳香族有机污染物,该作用对总吸附的贡献与污染物性质、生物炭的制备温度和理化属性以及二者之间的主导作用机制有关;另一方面屏蔽有机组分上和孔内的有效吸附位点,抑制芳香族污染物在生物炭上的吸附,酸洗去灰分对生物炭吸附芳香族污染物的影响取决于这两个方面的平衡.To elucidate the mineral effects of biochars on their sorption for aromatic pollutants,sorption of a polar aromatic compound(1-naphthol)and a nonpolar one(naphthalene)by wheat straw-derived biochars obtained at different charring temperatures(i.e.,300,400 and 500℃)and the corresponding deashed biochars was investigated.The results showed that organic carbon-normalized distribution coefficients(Koc)and isotherm nonlinearity of naphthalene and 1-naphthol by biochars generally increased after deashing,except the Koc value of 1-naphthol on W300,attributed to alteration of biochar structures and surface properties caused by mineral removal.The increased bulk polarity and decreased surface polarity after deashing treatment indicated that minerals in biochars influenced the spatial distribution of polar functional groups within biochars and would benefit the external exposure of polar groups on the surface of biochars.The aromatic carbon components in the original and deashed biochars served as more effective domains for naphthalene and 1-naphthol sorption over the alkyl carbon ones;the hydrophobic interactions between these two aromatics and the aromatic components in biochars dominated their sorption by the tested biochars.Deashing increased aromatic carbon content of biochars and their aromaticity;such a process also reduced exposure of polar groups on biochar surfaces,which increased accessibility of aromatics to their hydrophobic carbon domains,thereby enhancing the hydrophobic interactions between biochars and aromatic compounds.Hence,sorption affinity(Koc)of naphthalene and 1-naphthol was enhanced.The polar—OH substitution in 1-naphthol structure was able to interact with mineral O-containing surface or polar groups via hydrogen bonds,which greatly contributed to its sorption on the low-temperature(300℃)biochar.Deashing treatment weakened the H-bonding interactions,which could account for higher Koc value of 1-naphthol by the original biochar obtained at 300℃than that by its corresponding deashed one.This

关 键 词：生物炭 芳香族污染物 吸附 去灰分 

分 类 号：X703[环境科学与工程—环境工程]