摘要
为揭示生物吸附过程中Cr(Ⅵ)的还原转化机理,以改性玉米秸秆(corn stalk based anion exchanger, CS-AE)为模型吸附剂,通过XPS、13C-NMR和FT-IR等手段表征吸附Cr(Ⅵ)前后的材料表面组成和结构,并结合对吸附溶液中总有机碳(TOC)、总氮(TN)、硝态氮(NO3--N)等产物分析,探讨Cr(Ⅵ)还原的电子供体及可能反应路径.通过批吸附实验证实了CS-AE吸附去除Cr(Ⅵ)过程中存在Cr(Ⅵ)还原转化现象,在实验条件下10%～35%被吸附Cr(Ⅵ)还原转化为Cr(Ⅲ),且大部分(> 65%)Cr(Ⅲ)产物被固定在CS-AE表面.XPS表征中Cr 2p3/2谱图分析证明了Cr(Ⅲ)的大量存在,且N 1s、C 1s和O 1s谱图分析发现CS-AE与Cr(Ⅵ)反应后表面含氮物质特别是季铵基相对含量降低.13C-NMR和FT-IR表征也进一步地说明了吸附Cr(Ⅵ)后CS-AE表面季铵基减少,羧基结构有所增加,表明了季铵基是Cr(Ⅵ)还原转化的主要电子供体基团.吸附反应后溶液中TOC、TN和NO3--N含量随Cr(Ⅵ)初始浓度增加而增加,与Cr(Ⅲ)生成量呈正相关关系,可以确认CS-AE表面季铵基被Cr(Ⅵ)氧化,主要反应路径为季铵基经过碳-氮键氧化断裂,形成有机胺进入溶液,且部分有机胺被Cr(Ⅵ)进一步氧化为硝酸盐.
In this work,modified corn stalk(CS-AE) was used as model adsorbent to study the electron donor groups involved in Cr(Ⅵ)reduction to Cr(Ⅲ) during adsorption process in aqueous solution.Batch adsorption experiments showed the formation of Cr(Ⅲ) both in liquid solution and solid adsorbent.Approximately 10%-35% adsorbed Cr(Ⅵ) was reduced to Cr(Ⅲ),and most(> 65%) of formed Cr(Ⅲ) was bound to CS-AE.X-ray photoelectron spectroscopy(XPS),nuclear magnetic resonance(13 C-NMR) and Fourier transform-infrared spectroscopy(FT-IR) were employed to characterize surface element composition and functional groups of CSAE.XPS characterization showed that N content in CS-AE surface decreased after reaction with Cr(Ⅵ) as well as the relative content of quaternary ammonium groups,indicating quaternary ammonium group was oxidized by Cr(Ⅵ) as electron donors.13 C-NMR and FT-IR also found that the decrease of quaternary ammonium groups and a little increase of carboxylic groups.Determination results of total organic carbon(TOC),total nitrogen(TN) and nitrate(NO3--N) in adsorption solution suggested that TN,NO3--N,TOC content increased with initial Cr(Ⅵ) concentration and exhibited positive correlations with the production of Cr(Ⅲ)(P<0.05).This implied the possible oxidation pathways of quaternary ammonium by Cr(Ⅵ) included the break of C-N linkage between quaternary ammonium and CS-AE structure followed by the formation of organic amine which was subsequently oxidized to nitrate in solution.
作者
曹威
王镇乾
敖涵婷
苑宝玲
周真明
陈星欣
CAO Wei;WANG ZhenQian;AO HanTing;YUAN BaoLing;ZHOU ZhenMing;CHEN XingXin(College of Civil Engineering, Huaqiao University, Xiamen 361021, China)
出处
《中国科学：技术科学》
EI
CSCD
北大核心
2019年第3期301-310,共10页
Scientia Sinica(Technologica)
基金
国家自然科学基金项目(批准号:51408235)
福建省自然科学基金项目(编号:2016J01193
2015J01209)
福建省高校产学合作重大项目(编号:2018Y4101)
泉州市高层次人才创新创业项目(编号:2017Z025)资助
关键词
改性玉米秸秆
六价铬
吸附
还原转化
电子供体
modified corn stalk
Cr(Ⅵ)
adsorption
reduction transformation
electron donors
