摘要
研究高效还原技术是去除废水中Cr(Ⅵ)的有效手段,本研究提出了一种新颖有前景的基于紫外(UV)活化甲酸(HCOOH)产还原性二氧化碳阴离子自由基(CO_2^(·-))去除Cr(Ⅵ)的方法.通过对比UV、HCOOH、UV/HCOOH三种体系对Cr(Ⅵ)还原效率和电子自旋共振(EPR)对体系中自由基的检测研究了其活化原理和还原机制.结果表明UV能显著活化HCOOH产生CO_2^(·-)(αH=19.08G,αN=15.86G,g=2.0036).此外,试验考察了主要影响因素对Cr(Ⅵ)去除效果的影响,包括初始Cr(Ⅵ)浓度、甲酸投加量、初始p H值、反应温度、有机污染物以及水中常见阴离子.结果显示当甲酸浓度为40mmol/L,Cr(Ⅵ)初始浓度为10mg/L,反应时间在60min内,UV/HCOOH体系对Cr(Ⅵ)的去除率能达到100%.在酸性条件下(pH≤3.5)能显著促进Cr(Ⅵ)的还原,且Cr(Ⅵ)去除效率随着初始HCOOH浓度和反应温度升高而增加.进一步研究表明,该体系下NO_3^-对Cr(Ⅵ)的还原有着显著的促进作用,而Cl^-、HCO_3^-和对硝基苯酚(pNP)则有抑制作用.不同温度下Cr(Ⅵ)去除率与时间关系的拟合结果表明,当反应时间t≥40min,UV/HCOOH体系去除Cr(Ⅵ)过程遵循准一级反应动力学,根据不同温度下对应的反应速率常数k,结合阿伦尼乌斯方程,计算求得准一级反应的活化能为15.9k J/mol.
It is well recognized that the development of highly efficient reduction is an effective way to remove Cr(VI)from wastewater.Herein,a novel carbon dioxide anion radical(CO2^-)production induced by UV-activated formic acid system is expected to offer a promising technology for removal of Cr(VI).In the present study,the activation and reduction mechanism have been investigated by comparing the reduction efficiency of the three reduction systems(UV、HCOOH、UV/HCOOH)and detection of electron paramagnetic resonance(EPR),which suggested that UV can significantly activate HCOOH producing CO2^-(αH=19.08G,αN=15.86G,g=2.0036).Moreover,the main influencing factors,including initial Cr(VI)concentration,dosage of formic acid,initial pH,reaction temperature,organic containments and common anions were also discussed,the results showed that percent Cr(VI)removal of 100%was obtained in 60min when the initial concentration of formic acid and Cr(VI)was 40mmol/L and 10mg/L,respectively.It was further revealed that percent Cr(VI)removal efficiency increased with the increase of formic acid concentration and reaction temperature,and appeared to be an acid-pH-favoured condition(pH≤3.5).NO3-could remarkably promote the reduction of Cr(VI),while Cl-,HCO3-and p-nitrophenol showed an inhibitory effects.From the fitting results of the removal kinetics data at different temperatures,it is clearly exhibited that the reduction of Cr(VI)by the UV/HCOOH system followed the pseudo-first order reaction kinetics after 40min.Arrhenius activation energy Ea were calculated as 15.9kJ/mol according to the rate constants k at different temperatures.
作者
秦宝雨
唐海
李强
王健
邢庭其
滕雪刚
徐建平
QIN Bao-yu;TANG Hai;LI Qiang;WANG Jian;XING Ting-qi;TENG Xue-gang;XU Jian-ping(School of Biochemical Engineering,Anhui Polytechnic University,Wuhu 241000,China)
出处
《中国环境科学》
EI
CAS
CSSCI
CSCD
北大核心
2018年第7期2505-2511,共7页
China Environmental Science
基金
安徽省自然科学基金(1608085ME118)
安徽省优秀人才基金(gxyqZD2016120)
芜湖市科技计划重点项目(2017yf22).
