侯保林1,韩洪军2
(1. 湖南科技大学 页岩气资源利用湖南省重点实验室,土木工程学院,湖南 湘潭 411201; 2. 哈尔滨工业大学 环境学院,哈尔滨150090)
摘要:
为进一步去除煤化工废水生化出水中残留的有机污染物,采用以剩余污泥和铁泥为原材料制备的SAC-Fe作为催化粒子电极构建三维电Fenton体系深度处理煤化工废水,对过程参数进行优化,并探讨催化反应机理.结果表明:制备的SAC-Fe对煤化工废水生化出水中的污染物具有较高吸附性能,单位COD吸附容量为101.1 mg/g;采用RSM优化的三维电Fenton过程参数为电流密度16.78 mA/cm2、Fe浓度14.75 mmol/L、pH 3.92,此时TOC去除率为67.12%;通过体系内H2O2和·OH生成量分析,结合吸附作用探讨三维电Fenton深度处理煤化工废水的催化反应机理,SAC-Fe表现出较高的(电)催化活性,显著提升三维电Fenton体系内H2O2和·OH的生成量和生成速率,吸附作用提高·OH利用率和污染物降解率,进而提升三维电Fenton深度处理煤化工废水的效能.
关键词: 三维电Fenton 煤化工废水 深度处理 催化粒子电极 反应机理
DOI:10.11918/j.issn.0367-6234.201706024
分类号:X703
文献标识码:A
基金项目:国家自然科学基金(51704114);湖南科技大学页岩气资源利用湖南省重点实验室开放基金(E21721)
Advanced treatment of biologically pretreated coal chemical industry wastewater by three-dimensional electro-Fenton
HOU Baolin1,HAN Hongjun2
(1. Hunan Provincial Key Laboratory of Shale Gas Resource Utilization, School of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, Hunan,China; 2. School of Environment, Harbin Institute of Technology, Harbin 150090, China)
Abstract:
To further remove the organic pollutants residual in the biologically pretreated coal chemical industry wastewater, three-dimensional electro-Fenton system was established by involving Fe loaded sludge deserved activated carbon (SAC-Fe) from sewage and waste iron sludge, and was introduced in the advanced treatment of biologically pretreated coal chemical industry wastewater. Process parameters were optimized by response surface methodology (RSM) coupled with central composite design, and the catalytic reaction mechanism involved in system was discussed. Results show that SAC-Fe exhibited high adsorption performance to the pollutants in the wastewater. The maximum adsorption content calculated with Langmuir model was 101.1 mg/g. The optimal process parameters were determined as 16.78 mA/cm2 of current density, 14.75 mmol/L of equivalent Fe content and pH 3.92, with the observed TOC removal efficiency of 67.12%. The catalytic reaction mechanism was discussed based on the analysis of H2O2 and ·OH contents and adsorption effect. SAC-Fe exhibited high electro-catalytic activity in three-dimensional electro-Fenton system. SAC-Fe as catalytic particle electrode significantly promoted the production amount and rate of H2O2 and ·OH. Adsorption effect improved ·OH and organics removals. Thus three-dimensional electro-Fenton with SAC-Fe as catalytic particle electrode exerted excellent performance in the advanced treatment of coal chemical industry wastewater.
Key words: three-dimensional electro-Fenton coal chemical industry wastewater advanced treatment catalytic particle electrodes catalytic reaction mechanism
侯保林, 韩洪军. 三维电Fenton深度处理煤化工废水的催化反应机理[J]. 哈尔滨工业大学学报, 2018, 50(8): 45-50. DOI: 10.11918/j.issn.0367-6234.201706024.
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HOU Baolin, HAN Hongjun. Advanced treatment of biologically pretreated coal chemical industry wastewater by three-dimensional electro-Fenton[J]. Journal of Harbin Institute of Technology, 2018, 50(8): 45-50. DOI: 10.11918/j.issn.0367-6234.201706024.
![复制到剪切板](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/copy.gif)
基金项目 国家自然科学基金(51704114);湖南科技大学页岩气资源利用湖南省重点实验室开放基金(E21721) 作者简介 侯保林(1986—),男,博士,讲师;
韩洪军(1955—),男,教授,博士生导师 通信作者 侯保林, h3i3t0@126.com 文章历史 收稿日期: 2017-06-05
Contents -->Abstract Full text Figures/Tables PDF
三维电Fenton深度处理煤化工废水的催化反应机理
侯保林1
![通讯作者](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/REcor.gif)
![h3i3t0@126.com](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/REemail.gif)
1. 湖南科技大学 页岩气资源利用湖南省重点实验室,土木工程学院,湖南 湘潭 411201;
2. 哈尔滨工业大学 环境学院,哈尔滨150090
收稿日期: 2017-06-05
基金项目: 国家自然科学基金(51704114);湖南科技大学页岩气资源利用湖南省重点实验室开放基金(E21721)
作者简介: 侯保林(1986—),男,博士,讲师;
韩洪军(1955—),男,教授,博士生导师
通信作者: 侯保林, h3i3t0@126.com
摘要: 为进一步去除煤化工废水生化出水中残留的有机污染物,采用以剩余污泥和铁泥为原材料制备的SAC-Fe作为催化粒子电极构建三维电Fenton体系深度处理煤化工废水,对过程参数进行优化,并探讨催化反应机理.结果表明:制备的SAC-Fe对煤化工废水生化出水中的污染物具有较高吸附性能,单位COD吸附容量为101.1 mg/g;采用RSM优化的三维电Fenton过程参数为电流密度16.78 mA/cm2、Fe浓度14.75 mmol/L、pH 3.92,此时TOC去除率为67.12%;通过体系内H2O2和·OH生成量分析,结合吸附作用探讨三维电Fenton深度处理煤化工废水的催化反应机理,SAC-Fe表现出较高的(电)催化活性,显著提升三维电Fenton体系内H2O2和·OH的生成量和生成速率,吸附作用提高·OH利用率和污染物降解率,进而提升三维电Fenton深度处理煤化工废水的效能.
关键词: 三维电Fenton 煤化工废水 深度处理 催化粒子电极 反应机理
Advanced treatment of biologically pretreated coal chemical industry wastewater by three-dimensional electro-Fenton
HOU Baolin1
![Corresponding author](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/REcor.gif)
![h3i3t0@126.com](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/REemail.gif)
1. Hu'nan Provincial Key Laboratory of Shale Gas Resource Utilization, School of Civil Engineering, Hu'nan University of Science and Technology, Xiangtan 411201, Hu'nan, China;
2. School of Environment, Harbin Institute of Technology, Harbin 150090, China
Abstract: To further remove the organic pollutants residual in the biologically pretreated coal chemical industry wastewater, three-dimensional electro-Fenton system was established by involving Fe loaded sludge deserved activated carbon (SAC-Fe) from sewage and waste iron sludge, and was introduced in the advanced treatment of biologically pretreated coal chemical industry wastewater. Process parameters were optimized by response surface methodology (RSM) coupled with central composite design, and the catalytic reaction mechanism involved in system was discussed. Results show that SAC-Fe exhibited high adsorption performance to the pollutants in the wastewater. The maximum adsorption content calculated with Langmuir model was 101.1 mg/g. The optimal process parameters were determined as 16.78 mA/cm2 of current density, 14.75 mmol/L of equivalent Fe content and pH 3.92, with the observed TOC removal efficiency of 67.12%. The catalytic reaction mechanism was discussed based on the analysis of H2O2 and ·OH contents and adsorption effect. SAC-Fe exhibited high electro-catalytic activity in three-dimensional electro-Fenton system. SAC-Fe as catalytic particle electrode significantly promoted the production amount and rate of H2O2 and ·OH. Adsorption effect improved ·OH and organics removals. Thus three-dimensional electro-Fenton with SAC-Fe as catalytic particle electrode exerted excellent performance in the advanced treatment of coal chemical industry wastewater.
Key words: three-dimensional electro-Fenton coal chemical industry wastewater advanced treatment catalytic particle electrodes catalytic reaction mechanism
煤化工废水主要产生于煤制气洗涤过程,成分复杂,含有酚类化合物、含氮杂环化合物、多环芳烃、长链烷烃等多种有毒有机污染物,可生化性差,是一种典型的难降解工业废水[1].传统生化法处理后,废水中仍残留有大量有毒污染物,随着国家和行业对废水处理要求的提高,特别是“零排放”进程的推进,煤化工废水必须进行深度处理,以进一步去除废水中残留的有毒有害物质,净化水质.近年来,高级氧化技术(AOPs)在去除废水中难降解物方面受到越来越多的关注,特别是在工业废水深度处理中的应用.电Fenton具有原位生成Fenton试剂、Fe泥产量少、处理效能高等优点成为研究的热点,广泛应用于制药废水、染料废水、垃圾渗滤液等废水的深度处理[2-3].电Fenton利用阴极的电化学反应还原O2生成H2O2(式(1)),与投加的催化剂形成Fenton反应体系[4-5].由于电极(阴极)面积的限制,电Fenton体系普遍存在电流效率较低的问题[6-7].
${{\text{O}}_{\text{2(g)}}}\text{+2}{{\text{H}}^{\text{+}}}\text{+2}{{\text{e}}^{-}}\to {{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\text{.}$ (1)
电化学反应的实质是电极和电解液之间的非均相电子传递过程,电极的比表面积决定了电化学反应的速率[8],三维电极通过加入粒子电极以增大电极比表面积,从而加快电化学反应速率[9-10].目前,粒子电极的制备主要集中在碳质材料,但复杂的制备过程和较贵的原材料限制了碳质粒子电极的应用.电Fenton技术与三维电极耦合,将电Fenton的非均相催化剂和粒子电极合二为一,形成催化粒子电极,构建三维电Fenton体系,既可增加电极的比表面积,提高电化学反应的速率和H2O2生成量,又能增加H2O2催化活性位点,提升自由基产量[11],制备高效的催化粒子电极是构建三维电Fenton体系的核心.
剩余污泥是污水生化处理过程产生的不可避免的副产物,污泥的处理和处置已成为环保界关注的焦点问题.近年来,在污泥制备吸附材料、催化剂及催化剂载体等资源化利用方面进行了研究并取得了一定的成果[12].铁泥产生于传统Fenton、Fe/C微电解和其他物理化学过程,主要成分为铁和有机污染物,回用铁泥中的铁作为类Fenton催化剂的铁源已有相关研究.因此,可以利用剩余污泥和铁泥制备催化粒子电极,构建三维电Fenton,提高三维电Fenton的处理效能,实现污泥和铁泥的资源化利用.本文采用以剩余污泥和铁泥为原材料制备的催化粒子电极,构建三维电Fenton体系深度处理煤化工废水,采用响应面法(RSM)优化过程参数,基于吸附作用、体系内H2O2和·OH生成量探讨了三维电Fenton深度处理煤化工废水的催化反应机理.
1 实验 1.1 污水水质废水水样取自某煤化工厂污水处理站二沉池出水,该污水处理站采用多级AO工艺,废水水质指标如下:COD(176.58±7.26) mg/L,BOD5 (12.7±0.7) mg/L,总酚(35.21±1.90) mg/L,挥发酚(8.46±1.22) mg/L,TOC (48.66±3.42) mg/L,NH4+-N (3.34±0.16) mg/L,TN (52.26±2.12) mg/L,色度(300±20)倍,pH 6.5~7.5,生化出水的可生化性较差(BOD5与COD比小于0.08),难以采用生化法进行深度处理.
1.2 催化粒子电极的制备及性质以剩余污泥和铁泥为原材料采用一步热解法制备载铁污泥活性炭SAC-Fe(Fe loaded sludge deserved activated carbon),原材料中不添加铁泥制备污泥活性炭SAC作为对照;剩余污泥取自某污水处理厂,为未添加调理剂和未经脱水的污泥(含水率约99%,混合液悬浮固体浓度(MLSS)约1.1 g/L),铁泥取自某废水处理中试试验基地,铁泥样品为Fe/C微电解工艺沉淀的混合污泥.剩余污泥和铁泥经脱水和烘干后混合研磨,然后一步热解制备SAC-Fe,SAC-Fe呈现出孔状的碳质结构,主要元素为C、O、N、Fe,Fe催化物种以尖晶石结构的Fe3O4形式内嵌于碳质基体中,Fe与碳质基体通过化学键结合,SAC-Fe的详细制备过程和特性表征详见文献[11].
1.3 实验方法三维电Fenton采用圆柱形玻璃反应器,如图 1所示,有效容积2.0 L,阳极为Ti/Gd-SnO2,阴极为活性炭纤维(ACF),电极尺寸均为4.0 cm × 5.0 cm,电极间距为5.0 cm;阳极和阴极之间投加SAC-Fe作为催化粒子电极(第三极)构建三维电Fenton体系,SAC-Fe兼具粒子电极和催化剂的双重作用,催化粒子电极投加量为5.0 g/L.三维电Fenton深度处理煤化工废水实验前,将催化粒子电极和阴极在被处理水样中浸泡48 h,使催化粒子电极和阴极吸附饱和,然后进行三维电Fenton深度处理煤化工废水的实验;加入待处理水样,采用NaOH和H2SO4溶液调节水样pH,打开曝气泵和恒温搅拌装置,开启直流电源使电Fenton反应开始,在设定时间间隔取样,所取水样立即置于50 ℃水浴中30 min以去除未反应的H2O2和终止Fenton反应,经过滤后进行水质指标的分析.
Figure 1
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-1.jpg)
采用响应面法(RSM)耦合中心复合设计(CCD)进行过程参数的优化分析[13],选取电流密度、Fe浓度(Fe在整个反应器内的含量)、pH3个主要因素进行优化分析,利用Design expert软件进行CCD和RSM分析.
1.4 分析方法COD、总酚、色度采用标准方法分析;TOC采用TOC分析仪(TOC-VCPN,Shimadzu)测定;pH的测定采用Ph-3C酸度计;H2O2的测定采用碘量法;·OH采用荧光光谱检测分析[14],对苯二甲酸捕获·OH,生成具有荧光特性的物质,三维电Fenton电解液中加入对苯二甲酸,对苯二甲酸浓度为1.0,0.05 mol/L的Na2SO4为支持电解质,反应过程中取样,进行荧光光谱检测,激发波长315 nm,发射波长扫描范围360~520 nm,通过荧光强度表征·OH浓度.
2 结果与讨论 2.1 吸附性能催化粒子电极的吸附性能对三维电Fenton效能的影响较大,吸附作用是催化反应过程中的重要基元步骤[15],SAC-Fe和SAC对煤化工废水中COD的吸附等温实验如图 2所示.吸附实验数据与Langmuir吸附模型具有较好的拟合相关性(R2>0.995),说明SAC-Fe和SAC对废水中有机污染物的吸附以单层吸附为主,通过Langmuir模型计算得到SAC-Fe和SAC对废水中COD的吸附容量分别为101.1和112.6 mg/g,由于SAC-Fe和SAC由剩余污泥热解制备,SAC-Fe和SAC具有碳质的质地和良好的孔隙发育,因此,具有较高的吸附性能,SAC-Fe较SAC吸附容量降低的原因主要是孔隙结构的差异和比表面积的降低(SSAC:388.9 m2/g,SSAC-Fe:351.6 m2/g),吸附等温实验结果表明制备的催化粒子电极对废水中有机污染物具有较高的吸附性能,有助于污染物在催化粒子电极表面的吸附和富集,为(电)化学反应和污染物降解反应提供了反应界面和反应空间.
Figure 2
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-2.jpg)
2.2 三维电Fenton深度处理煤化工废水的效能SAC-Fe是内嵌Fe3O4活性催化物质的多孔碳质材料,催化活性与其碳质多孔材质和内嵌Fe3O4活性催化物种密切相关,SAC-Fe、SAC和Fe3O4 MNPs作为催化粒子电极/催化剂的体系处理效能如图 3所示(反应条件:电流密度15.0 mA/cm2,Fe浓度13.8 mmol/L,pH 7.0).
Figure 3
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-3.jpg)
采用SAC、Fe3O4 MNPs和SAC-Fe作为催化粒子电极/催化剂的体系反应120 min后COD去除率分别为24.54%、41.67%和64.37%,表明SAC-Fe作为三维电Fenton体系的催化粒子电极时具有较高的催化活性.
三维电Fenton的过程参数决定其深度处理煤化工废水的效能,电流密度、Fe浓度、pH是影响电Fenton处理效能的主要因素,采用响应面法(RSM)耦合中心复合设计(CCD)对各因素影响显著性进行分析和优化,结果如图 4所示.
Figure 4
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-4.jpg)
RSM的方差分析表明,pH对响应值的影响显著性较低,电流密度和pH交互作用对响应值的影响不显著.电流是三维电Fenton反应的主要驱动力,电流密度增加,电化学反应增强,但过高的电流密度会造成副反应的发生,如O2的四电子还原直接生成H2O(式(2))、H2O2在电极表面的氧化还原(式(3)和(4))、过量H2O2自捕获·OH(式(5))等[16],从而降低处理效能;Fe活性物种是三维电Fenton的催化剂,因此,Fe浓度对响应值影响显著性较高,但Fe浓度过高会造成SAC-Fe比表面积下降、Fe氧化物聚集、Fe活性物种捕获·OH等现象,降低三维电Fenton处理效能;由于SAC-Fe中具有H2O2催化活性的Fe活性位点固定在碳质基体上,形成非均相催化剂,且体系内H2O2原位持续生成,因此,pH对三维电Fenton的影响显著性降低;电流密度和Fe浓度的交互表现出协同作用,电流密度和Fe浓度是参与三维电Fenton体系的两个主要反应过程,同时提高电流密度和Fe浓度增强H2O2的电化学生成和H2O2催化分解,因此,电流密度和Fe浓度的交互作用具有较高的影响显著性.根据RSM模型分析得到优化的条件参数为:电流密度16.78 mA/cm2,Fe浓度14.75 mmol/L(折算为SAC-Fe中铁质量分数为16.5%),pH 3.92,此时TOC去除率为67.12%,优化的条件参数下三维电Fenton深度处理煤化工废水的效能见表 1.
${{\text{O}}_{\text{2(g)}}}\text{+4}{{\text{H}}^{\text{+}}}\text{+4}{{\text{e}}^{-}}\to \text{2}{{\text{H}}_{\text{2}}}\text{O, }$ (2)
${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\to \text{H}{{\text{O}}_{\text{2}}}\cdot \text{+}{{\text{H}}^{\text{+}}}\text{+}{{\text{e}}^{-}}\to {{\text{O}}_{\text{2(g)}}}\text{+2}{{\text{H}}^{\text{+}}}\text{+2}{{\text{e}}^{-}}, $ (3)
${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\text{+2}{{\text{H}}^{\text{+}}}\text{+2}{{\text{e}}^{-}}\to \text{2}{{\text{H}}_{\text{2}}}\text{O}, $ (4)
${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\text{+}\cdot \text{OH}\to \text{H}{{\text{O}}_{\text{2}}}\cdot \text{+}{{\text{H}}_{\text{2}}}\text{O}\text{.}$ (5)
表 1
![点击查看表格内容](http://hit.alljournals.cn/html/hitxb_cn/2018/8/images/table-icon.gif)
COD 176.58±7.26 46.55±1.61 73.64
总酚 35.21±1.90 0.95±0.12 97.30
挥发酚 8.46±1.22 0.11±0.02 98.70
TOC 48.66±3.42 16.00±0.92 67.12
色度 300±20 25±5 91.67
表 1 三维电Fenton深度处理煤化工废水的效能 Table 1 Treatment performance of three-dimensional electro-Fenton
2.3 H2O2和·OH生成H2O2的电化学原位生成和自由基的催化形成是(三维)电Fenton反应体系的主要步骤,直接影响(三维)电Fenton的处理效能[17],三维电Fenton体系中H2O2生成量如图 5所示.随着电解反应的进行,体系内H2O2浓度逐渐升高,反应60 min后体系内H2O2浓度趋近平衡,主要与H2O2的自分解和H2O2在电极表面的氧化还原有关;反应60 min时二维和三维电Fenton(SAC)体系内H2O2浓度分别为433.3和755.7 μmol/L,说明投加SAC催化粒子电极形成三维电Fenton后,体系内H2O2生成量显著增加,体系内氧化剂(H2O2)生成量的增加是电Fenton处理效能提升的基础.三维电Fenton体系中,催化粒子电极经极化后,相邻两个催化粒子电极之间形成微型电解池,电极面积和电催化活性位点大幅度增加,电化学生成H2O2的反应从阴极表面延伸到整个电解池,因此,三维电Fenton体系内H2O2生成量显著增加.
Figure 5
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-5.jpg)
三维电Fenton体系内形成的主要活性氧化物种是H2O2催化分解产生的·OH,·OH的生成量直接影响三维电Fenton的处理效能,三维电Fenton体系内·OH生成量的荧光检测如图 6所示.二维电Fenton体系内·OH生成量极低,主要是体系内未投加催化剂,电化学生成的H2O2未能催化分解形成·OH,且二维电Fenton体系内H2O2生成量较三维体系低.投加SAC形成三维电Fenton体系·OH生成量也较低,主要是SAC中缺乏催化H2O2分解的Fe活性物种,催化活性位点少,·OH生成量低.投加SAC-Fe作为催化粒子电极的三维电Fenton体系中·OH生成量远高于其他反应体系,一方面源于三维电Fenton体系内H2O2生成量的增加,另一方面是因为SAC-Fe中的Fe活性物种原位催化H2O2生成·OH,SAC-Fe既增加了反应电极表面积,提升了H2O2的生成量,又具有Fe氧化物的H2O2催化活性位点,使H2O2高效地催化分解产生·OH.因此,SAC-Fe作为催化粒子电极的三维电Fenton反应体系具有较高的H2O2和·OH生成量,同时表明SAC-Fe具有较高的电化学催化活性和H2O2催化活性,大幅提高三维电Fenton体系内H2O2和·OH的生成量,从而显著提升三维电Fenton深度处理煤化工废水的效能.
Figure 6
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-6.jpg)
2.4 反应机理三维电Fenton体系内,SAC-Fe作为催化粒子电极,兼具粒子电极和电Fenton催化剂的双重作用,由于催化活性位点固定在SAC-Fe上,反应为表面催化反应,基于吸附作用、H2O2和·OH生成分析,推测三维电Fenton深度处理煤化工废水的催化反应机理,如图 7所示.
Figure 7
![点击查看原图](http://hit.alljournals.cn/html/hitxb_cn/2018/8/PIC/hebgydxxb-50-8-45-7.jpg)
三维电Fenton开始于SAC-Fe的吸附,首先,由于SAC-Fe的吸附作用,大量活性O2分子和污染物向SAC-Fe表面扩散并富集于SAC-Fe上,保持较高的局部浓度;随后,活性O2通过两电子途径原位还原生成H2O2(式(1)),同时,原位生成的H2O2迅速被SAC-Fe表面和内部的Fe活性物质催化分解形成·OH(式(6)和(7)),最后,形成的·OH与有机污染物反应将其降解或彻底矿化(式(8)).由于废水污染物通过吸附作用富集于SAC-Fe上且具有较高的局部浓度,生成的·OH原位捕捉有机污染物将其降解或矿化,从而提高·OH的利用率和污染物的去除率.
$\equiv \text{F}{{\text{e}}^{\text{II}}}-\text{OH+}{{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\to \equiv \text{F}{{\text{e}}^{\text{II}}}-\text{OH}\cdot {{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\text{, }$ (6)
$\equiv \text{F}{{\text{e}}^{\text{II}}}-\text{OH}\cdot {{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}\to \equiv \text{F}{{\text{e}}^{\text{III}}}-\text{OH+}\cdot \text{OH+O}{{\text{H}}^{-}}\text{, }$ (7)
${污染物_{\text{(ads)}}}\text{+}\cdot \text{OH}\to 降解产物\text{/C}{{\text{O}}_{\text{2}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\text{.}$ (8)
由于Fe活性物种嵌入SAC-Fe多孔碳质基体中,且具有较高的暴露量和较多的活性位点,电化学反应生成的H2O2原位被催化形成·OH,大幅提高·OH的产量.SAC-Fe中的催化活性物种为尖晶石结构的Fe3O4,这种结构通过特殊的电子传递有利于FeII催化活性位点的再生.另外,Fe催化活性物种嵌入多孔碳质基体中,增强了Fe催化活性物种的分散度,增加了催化活性位点数量,因此,SAC-Fe作为催化粒子电极的三维电Fenton对处理煤化工废水具有较高的处理效能.
3 结论1) 以剩余污泥和铁泥为原材料制备的SAC-Fe催化粒子电极对煤化工废水生化出水中COD具有较高的吸附性能,通过Langmuir模型计算SAC-Fe对COD的吸附容量为101.1 mg/g.
2) 以SAC-Fe作为催化粒子电极构建的三维电Fenton体系深度处理煤化工废水,通过RSM分析了主要过程参数及其交互作用对三维电Fenton深度处理煤化工废水效能的影响,得到优化的过程参数分别为电流密度16.78 mA/cm2、Fe浓度14.75 mmol/L、pH 3.92,此时TOC去除率为67.12%.
3) 基于吸附作用、H2O2和·OH生成探讨了三维电Fenton的催化反应机理,SAC-Fe作为催化粒子电极同时提高了三维电Fenton体系内H2O2和·OH的生成量,SAC-Fe的吸附作用提高了·OH的利用率和污染物的降解率,进而显著提升了三维电Fenton深度处理煤化工废水的处理效能.
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