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随着社会发展,水资源短缺问题日益严重. 在众多水处理技术中,多相光催化氧化技术具有操作简便、有机物矿化效率高、催化剂能循环利用等优点,在有机废水资源化利用中具有广阔的应用前景[1 − 2].
多相光催化氧化体系中,氧化剂主要有过氧化氢(H2O2)和过硫酸盐(PS)两大类[3 − 4],催化剂则通常是将过渡金属离子(Fe3+、Cu2+、Co2+等)负载到不同的载体上(活性炭、多孔材料等)制备得到[5 − 7]. MCM-41硅基介孔分子筛具有骨架结构稳定、合成简便、孔道结构规则、孔径尺寸可调节、比表面积大等优点,是多相光催化剂载体开发研究的热点[8 − 10]. 将铁、铜等过渡金属负载到MCM-41介孔分子筛表面或掺杂进骨架之中,可以制备高效活化H2O2或PS降解有机污染物的多相催化剂[11 − 14]. Deng等[13]发现,Fe/MCM-41介孔材料对H2O2具有很高的光催化活性,相应的催化氧化体系能在120 min内高效降解MB染料. Schlichter等[14]合成了对PS有高催化活性的铜基MCM-41多相催化剂,对应的催化氧化体系能在2 h内有效降解MO染料. 此外,MCM-41介孔分子筛表面的负电性能够在一定程度上抑制OH−对活性组分的沉淀反应,从而有望拓展多相光催化氧化体系的pH适用范围[15 − 16].
空间位阻效应是影响氧化剂作用于有机污染物的重要因素[17 − 18]. 例如,杨欢欢[17]进行了硫酸根自由基降解全氟羧酸化合物的DFT计算,发现正是空间位阻效应导致体积较大的硫酸根自由基只能进攻未被氟原子包裹的端基碳原子. Lee等[18]在研究PS活化机制和活性物种形成途径时发现,更大的空间位阻使过二硫酸盐(PDS)对有机物的反应性较过一硫酸盐(PMS)更低. 目前,在多相光催化氧化领域中,缺乏空间位阻效应影响催化剂活化氧化剂的研究. 过硫酸盐(PS)与H2O2分子结构相似,H2O2上的一个H原子被HSO3−取代即为过一硫酸盐(PMS,HSO5−),若两个H原子全被HSO3−取代便得到同样具有对称结构的过二硫酸盐(PDS,S2O82-)[19]. 因此,HSO5−和S2O82-相较于H2O2具备更大的分子尺寸. 介孔分子筛催化剂在活化分子尺寸相差较大的PDS和H2O2时,空间位阻效应的差异会更为显著,但目前关于介孔分子筛催化剂构型对氧化剂PDS和H2O2活化影响的研究鲜见报道.
基于此,本文选取Fe-MCM-41和Cu-MCM-41作为多相光催化剂,选取同样具有对称结构但分子尺寸相差较大的H2O2和PDS作为氧化剂,构建了中性条件下的多相光催化氧化降解金橙Ⅱ体系,分析了催化剂构型、孔道尺寸和电负性对Fe-MCM-41和Cu-MCM-41活化H2O2和PDS能力的影响,揭示了Fe-MCM-41和Cu-MCM-41光催化活化H2O2和PDS的构-效关系,为介孔分子筛光催化剂的开发利用提供理论依据.
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SX2-4-10箱式电阻炉(上海实验仪器厂有限公司);PCX50C Discover多通道光反应系统(北京泊菲莱科技有限公司);UV-2300紫外分光光度计(中国上海天美科学仪器);Multi N/C 2100总有机碳分析仪(美国岛津分析仪器股份有限公司);Bruker D8 Advance型X射线衍射仪;麦克ASAP2460比表面积孔隙度分析仪;ZEISS GeminiSEM 300 扫描电子显微镜;Titan G260-300透射电子显微镜;Nano ZS90纳米粒度及zeta电位仪;电子顺磁共振波谱仪(EPR,EMX nano,Bruker 公司,德国).
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金橙Ⅱ(生物染色剂)、正硅酸乙酯(化学纯)、L-组氨酸购于阿拉丁化学试剂有限公司;十六烷基三甲基溴化铵、过硫酸钠购于上海麦克林生化科技有限公司;氨水、30%H2O2、氢氧化钠、乙醇购于西陇化工有限公司;磷酸氢二钠、磷酸二氢钠、异丙醇、叔丁醇、九水合硝酸铁、三水合硝酸铜购于国药集团. 以上试剂如无特殊说明均为分析纯,试剂溶液均用超纯水配置.
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Fe-MCM-41在室温下制备[8,12,20]:称取3.39 g九水合硝酸铁溶解于75 mL正硅酸乙酯(TEOS)和75 mL乙醇的混合液中,得到混合溶液A;称取25 g十六烷基三甲基溴化铵(CTAB)于1250 mL超纯水中,超声处理1 h使其完全溶解得到澄清液B;30 ℃条件下,将100 mL氨水缓慢加入澄清液B中,10 min后逐滴加入混合溶液A,滴加完成后持续搅拌16 h,得到凝胶C;将凝胶C于室温下静置老化24 h后过滤,产物用乙醇和超纯水反复离心洗涤至中性,80 ℃干燥至恒重;干燥后将产物研磨,放入马弗炉中于550 ℃煅烧6 h(升温速率5 ℃·min−1),自然冷却至室温后取出,充分研磨后得到Fe-MCM-41. 按照上述方法制备得到MCM-41(混合溶液A为75 mLTEOS+75 mL乙醇)和Cu-MCM-41(混合溶液A为1.77 g三水合硝酸铜+75 mLTEOS+75 mL乙醇).
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样品晶型采用Bruker D8 Advance型X射线衍射仪分析;样品比表面积使用麦克ASAP2460比表面积孔隙度分析仪测定;样品形貌使用ZEISS GeminiSEM 300扫描电子显微镜观察;样品孔道情况通过Titan G260-300透射电子显微镜拍摄分析;样品在不同pH条件下的zeta电位使用Nano ZS90纳米粒度及zeta电位仪测定.
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采用5,5-二甲基-1-吡咯啉-N-氧化物(DMPO)作为·OH、SO4−·和O2−·等活性物质的捕获剂,2,2,6,6-四甲基哌啶(TEMP)作为1O2的捕获剂,使用电子顺磁共振波谱仪(EPR,EMX nano,Bruker 公司,德国)检测.
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实验在PCX50C Discover多通道光催化反应系统中进行,恒温水浴控制反应温度为30 ℃;磁力搅拌系统转速设定为250 r·min−1;光通道底部光源为紫外灯(波长254 nm,功率5 W,光强59.6 lux). 反应条件:金橙Ⅱ浓度为0.2 mmol·L−1、pH值为6.8、催化剂用量为1 g·L−1、氧化剂浓度为10 mmol·L−1.
实验预先将催化剂和金橙Ⅱ溶液加入反应瓶中,无光条件下搅拌30 min达到吸附平衡;而后加入氧化剂,同时打开光源并开始计时,在设定的时刻取样、过滤(0.45 μm水系滤头)、测定.
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金橙Ⅱ浓度通过分光光度计在484 nm处测得吸光度,再经过标准曲线换算得到;总有机碳含量(TOC)采用总有机碳分析仪测定,取样后按体积比1:1加入终止剂(0.1 mmol·L−1Na2SO3,0.1 mmol·L−1 KH2PO4,0.1 mmol·L−1 KI,0.05 mmol·L−1 NaOH)[21 − 22]以终止反应.
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图1为MCM-41、Fe-MCM-41和Cu-MCM-41的X射线衍射图谱. 其中,图1a是样品在0.5°—10°小角区域的XRD图谱. MCM-41存在(100)、(110)和(200)的3个晶面的特征衍射峰,这说明合成的MCM-41具备有序六方介孔结构[12,23];与MCM-41相比,Fe-MCM-41的3个衍射峰位置和强度均没有明显变化,可见Fe掺杂后材料的介孔结构和有序性几乎没有变化;Cu-MCM-41的(100)晶面衍射峰强度明显降低,且(110)和(200)晶面的衍射峰基本消失,说明Cu的掺杂对材料的结构和有序性产生了较大的影响,但基本保留了MCM-41的介孔结构.
样品在10°—80°广角区域的XRD图谱如图1b所示. 3个样品均在23°左右有一个特征峰,即SiO2特征衍射峰,与样品主体为SiO2吻合;Fe-MCM-41没有发现铁氧化合物的衍射峰,表明铁元素高度分散在MCM-41骨架中;而Cu-MCM-41在2θ=35.5°、38.7°和48.7°处出现了CuO的特征峰,说明掺杂的铜元素既有部分分散在MCM-41骨架,还有部分以CuO的形式共存.
BET分析结果显示MCM-41、Fe-MCM-41、Cu-MCM-41的比表面积分别为1058 m2·g−1、1040 m2·g−1和951 m2·g−1. Fe-MCM-41比表面积相较于MCM-41几乎不变,进一步证明Fe的掺杂对MCM-41结构的影响很小;而CuO的形成则导致Cu-MCM-41的比表面积减小明显.
为进一步分析材料的形态,对MCM-41、Fe-MCM-41和Cu-MCM-41进行了扫描电镜(SEM)分析,结果如图2. 由图2可见,MCM-41呈现棒状或球状形态,Fe-MCM-41呈现椭球状或球状形态. Fe-MCM-41的Fe元素mapping图显示Fe元素均匀地掺杂到了分子筛骨架[24],这与XRD分析结果一致. 除椭球状和球状形态外,Cu-MCM-41还呈现了不规则纳米块状形态. Cu元素mapping图表明,纳米块状形态颗粒为铜的纳米颗粒或金属氧化物簇,结合广角XRD测试结果可以推断其为纳米CuO.
由以上表征可以推断,Fe-MCM-41为Fe元素均匀掺入MCM-41骨架内部的同晶替换型催化剂;Cu-MCM-41为Cu元素分布不均匀、部分以CuO形式结合在MCM-41骨架外的同晶替换和孤岛共存型催化剂.
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图3为MCM-41、Fe-MCM-41和Cu-MCM-41的透射电镜(TEM)图. 在50 nm标尺图中可以看到,3种材料均在孔道方向上呈现出六方排列的蜂巢结构,说明经Fe或Cu金属掺杂后,MCM-41的有序介孔特征结构能被保留,这与小角XRD分析结果一致. 进一步放大观察尺度,在20 nm标尺图中对材料的孔径进行测量. 每种样品分别随机选取3个孔道测量孔径,取平均值得到其平均孔径. 根据比例尺测出MCM-41平均孔径为2.14 nm,Fe-MCM-41和Cu-MCM-41平均孔径均为2.02 nm. BET分析对应3个样品介孔平均孔径依次为3.06 nm、2.97 nm、2.71 nm,孔径大小集中在3 nm左右,这与文献报道一致[8,25]. 一定量的金属掺杂会导致MCM-41介孔分子筛的孔容孔径减小[26].
理想状态且不考虑水合影响时,氧化剂H2O2和PDS最长径分别为0.48 nm和0.934 nm,对应球体模型最大截面积分别为1.81nm2和6.85 nm2(图4); Fe-MCM-41和Cu-MCM-41的平均孔径均为2.02 nm,即其正六边形孔道边长为1.166 nm,孔道面积为35.32 nm2. PDS能够同时通过分子筛孔道截面的分子数(5个)远少于H2O2(19个),显然催化PDS的过程会受到更大的空间位阻影响.
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Fe-MCM-41和Cu-MCM-41在不同pH条件下的zeta电位如图5所示. Fe-MCM-41和Cu-MCM-41的零电荷点分别为2和3,在近中性(pH=6.8)的实验条件下两种材料表面均带负电荷. 而H2O2分子呈电中性,不受电性影响;PDS带负电,会与同样带负电荷的材料相互排斥.
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Fe-MCM-41和Cu-MCM-41光催化H2O2和PDS降解金橙Ⅱ的结果如图6所示. 由图6可知,单独H2O2或PDS难以直接有效氧化降解金橙Ⅱ. 近中性和无光条件下,Fe-MCM-41和Cu-MCM-41均不能有效活化H2O2降解金橙Ⅱ;相同条件下,Fe-MCM-41和Cu-MCM-41能活化PDS降解金橙Ⅱ,反应120 min后二者脱色率分别为10%和15%.
紫外光照射下,不同体系中金橙Ⅱ脱色的一级动力学常数见表1. UV能够活化H2O2和PDS[21, 27],生成羟基自由基或硫酸根自由基使金橙Ⅱ脱色. 金橙Ⅱ在UV+H2O2和UV+PDS体系的脱色动力学常数分别为0.017 min−1和0.031 min−1,说明紫外光对PDS的活化效率远高于H2O2.
Fe-MCM-41光催化活化H2O2和PDS时,H2O2分子受空间位阻和电性影响微弱,能顺利通过Fe-MCM-41内部孔道并与活性组分充分接触而被高效活化;而PDS同时受到很强的空间位阻和电性排斥影响,难以高效通过催化剂孔道进入催化剂内部,同时催化剂会对紫外光造成遮挡,导致其不能被有效活化. 因此,UV+H2O2+Fe-MCM-41体系降解金橙Ⅱ的动力学常数为0.026 min−1,较UV+H2O2体系提升了52.9%;而UV+PDS+Fe-MCM-41体系降解金橙Ⅱ的动力学常数为0.028 min−1,较UV+PDS体系有所下降.
Cu-MCM-41构型为同晶替换和孤岛共存型,其光催化活化H2O2和PDS时会受到催化剂构型、空间位阻和电性的三重影响. H2O2分子虽然受空间位阻和电性影响较小,能高效通过Cu-MCM-41孔道与活性组分充分接触,但铜离子对H2O2的活化能力微弱[28],且催化剂会对紫外光造成遮挡,因此UV+H2O2+Cu-MCM-41体系中H2O2不能被有效活化;而PDS分子虽然受到较强的空间位阻和电性排斥干扰,不能高效通过孔道,但催化剂表面和孤岛组分CuO对PDS有较强的活化能力[29 − 30],所以Cu-MCM-41能高效活化PDS降解金橙Ⅱ. 由表1可见,UV+H2O2+Cu-MCM-41体系降解金橙Ⅱ的动力学常数仅为0.015 min−1,较UV+H2O2体系有所下降;而UV+PDS+Cu-MCM-41体系降解金橙Ⅱ的动力学常数达到了0.043 min−1,较UV+PDS体系提升了38.7%.
金橙Ⅱ在各体系中反应开始时和反应180 min时的矿化情况如图7所示,根据反应前后体系的TOC值可以计算不同体系反应180 min时金橙Ⅱ的矿化率. Fe-MCM-41和Cu-MCM-41对金橙Ⅱ有一定的吸附作用,使得反应开始时(暗吸附平衡)不同体系的TOC值略有差异. 近中性UV+H2O2体系反应180 min时,加入Fe-MCM-41可以将矿化率由43%提高至57%,而加入Cu-MCM-41会使矿化率降至40%;近中性UV+PDS体系反应180 min时,加入Cu-MCM-41可以将矿化率由48%提高至76%,而加入Fe-MCM-41会使矿化率降至45%.
上述结果说明,在近中性和紫外光条件下,Fe-MCM-41是活化H2O2的高效催化剂,而Cu-MCM-41是活化PDS的高效催化剂.
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通过淬灭实验研究各体系活性基团对金橙Ⅱ降解过程的贡献,结果如图8所示. 对于UV+H2O2+Fe-MCM-41体系,以异丙醇作为淬灭剂进行了淬灭实验. 异丙醇是·OH良好的淬灭剂,其与·OH的反应速率高达1.9×1010 L·(mol·s)−1[31]. 加入过量异丙醇后体系中金橙Ⅱ的降解几乎被完全抑制,说明UV+H2O2+Fe-MCM-41体系中·OH是降解金橙Ⅱ最主要的活性基团.
对于UV+PDS+Cu-MCM-41体系,分别以L-组氨酸(1O2、SO4−·和·OH的淬灭剂)[32 − 33]、乙醇(SO4−·和·OH的淬灭剂)[34 − 35]和叔丁醇(·OH的淬灭剂)[34 − 35]作为淬灭剂进行淬灭实验. L-组氨酸是1O2的淬灭剂(反应速率为 3.2 × 107 L·(mol·s)−1),其也能与SO4−·(反应速率为 2.5 × 109 L·(mol·s)−1)和·OH(反应速率为 5.0 × 109 L·(mol·s)−1)发生反应[32 − 33]. 乙醇与SO4−·和·OH的反应速率分别为1.6× 107—7.8 × 107 L·(mol·s)−1和1.1× 109—2.8 × 109 L·(mol·s)−1,而叔丁醇与SO4−·和·OH的反应速率分别为4× 105—9.1 × 105 L·(mol·s)−1和3.6× 109—7.6 × 109 L·(mol·s)−1 [33 − 35]. 由图8b可见,UV+PDS+Cu-MCM-41体系中加入以上淬灭剂后,金橙Ⅱ的降解均受到一定程度的抑制. 其中,L-组氨酸抑制效果最为突出,金橙Ⅱ的降解速率常数降至0.002 min−1(基础k=0.043 min−1);其次是乙醇,金橙Ⅱ的降解速率常数降至0.014 min−1;抑制效果最弱的是叔丁醇,金橙Ⅱ的降解速率常数仍有0.041 min−1. 以上结果说明,在UV+PDS+Cu-MCM-41体系中,主要活性物种为1O2和SO4−·.
为进一步鉴定体系生成的自由基,采用EPR对活性物种进行了测定. 以水为溶剂检测1O2、SO4−·和·OH,以二甲基亚砜(DMSO)为溶剂检测O2−·[36],结果如图9所示. UV+H2O2+Fe-MCM-41体系仅观察到了DMPO-·OH(1:2:2:1)复合物特征峰信号[36 − 37],说明该体系主要的活性物种为·OH. UV+PDS+Cu-MCM-41体系中检测到了DMPO-·OH(1:2:2:1)和DMPO-SO4−·(1:1:1:1:1:1)[36 − 37],证明该体系反应过程中产生了·OH和SO4−·(·OH是由SO4−·与水反应生成[30,36]). 另外,EPR图谱中观察到了DMPO-O2−·信号[38],表明该体系反应过程中有O2−·生成. 同时TEMP-1O2(1:1:1)[33]特征峰信号出现证明该体系中确有1O2生成.
结合淬灭实验结果,可知UV+H2O2+Fe-MCM-41体系主要活性物种为·OH,UV+PDS+Cu-MCM-41体系主要活性物种为1O2和SO4−·.
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基于以上分析,得到中性条件下Fe-MCM-41和Cu-MCM-41光催化H2O2和PDS的构-效关系,结果如图10所示. 对于Fe-MCM-41,首先紫外光将催化剂上的≡FeⅢ光解还原成≡FeⅡ(式1);H2O2受空间位阻和电性排斥影响小,能顺利通过催化剂内部孔道;催化剂表面和孔道内部的≡FeⅡ能与H2O2发生芬顿反应生成≡FeⅢ和·OH(式2)[21,39];催化剂上≡FeⅡ与≡FeⅢ的循环促进了H2O2持续分解生成·OH进而降解金橙Ⅱ;PDS由于受到空间位阻和电性排斥的影响,难以进入Fe-MCM-41孔道之中,加上催化剂对紫外光的遮挡,导致UV+PDS+Fe-MCM-41体系中PDS不能得到有效活化.
对于Cu-MCM-41,首先紫外光将同晶替换于骨架中的≡CuⅡ和孤岛CuO上的≡CuⅡ光解还原成≡CuⅠ(式3);PDS因为空间位阻和电性排斥难以进入催化剂孔道,但催化剂表面的≡CuⅠ和孤岛CuO上的≡CuⅠ可以快速活化S2O82-产生≡CuⅡ和SO4−·[40](式4);此外,过硫酸盐还可以进一步转化生成O2−·和1O2(式5-7)[33,36 − 37];体系中生成的1O2和SO4−·能高效氧化降解金橙Ⅱ;H2O2虽然能自由进出催化剂孔道,但铜离子活化H2O2的效果极差,且催化剂会对紫外光造成遮挡,因此在UV+H2O2+Cu-MCM-41体系中H2O2不能被有效活化.
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(1)在室温下制备了Fe-MCM-41和Cu-MCM-41,表征结果证明Fe-MCM-41为同晶替换型催化剂,Cu-MCM-41为同晶替换和CuO孤岛共存型催化剂.
(2)中性条件下,H2O2受空间位阻和电性排斥影响小,能被Fe-MCM-41孔道内外铁离子高效光催化,但难以被Cu-MCM-41中同晶替换和孤岛的铜离子高效光催化;PDS由于受到空间位阻和电性排斥的影响,难以进入Fe-MCM-41和Cu-MCM-41孔道之中,但Cu-MCM-41表面和孤岛上的铜离子能高效光催化PDS.
(3)中性条件下,Fe-MCM-41能高效光催化H2O2产生·OH降解金橙Ⅱ,Cu-MCM-41则能高效光催化PDS产生1O2和SO4−·降解金橙Ⅱ. UV+H2O2体系中加入Fe-MCM-41,金橙Ⅱ的脱色速率提升了52.9%,反应180 min时体系矿化率从43%提高到了57%;UV+PDS体系中加入Cu-MCM-41,金橙Ⅱ的脱色速率提升了38.7%,反应180 min时体系矿化率从48%提高到了76%.
中性条件Fe/Cu-MCM-41光催化活化H2O2/PDS的构-效关系
The structure-activity relationship of Fe/Cu-MCM-41 on photocatalytic activation of H2O2/PDS under neutral condition
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摘要: 本文在室温下制备了Fe-MCM-41和Cu-MCM-41,利用XRD、BET、SEM和TEM等手段对催化剂进行了表征. 选取金橙Ⅱ为探针分子、H2O2和PDS作为氧化剂,构建了多相光催化氧化体系,研究中性条件下Fe-MCM-41和Cu-MCM-41光催化活化H2O2和PDS的构-效关系. 结果表明,Fe-MCM-41为同晶替换型催化剂,Cu-MCM-41为同晶替换和CuO孤岛共存型催化剂. 中性条件下,H2O2受空间位阻和电性排斥影响小,能被Fe-MCM-41孔道内外铁离子高效光催化产生·OH,但难以被Cu-MCM-41中同晶替换和孤岛的铜离子高效光催化;PDS由于受到空间位阻和电性排斥的影响,难以进入Fe-MCM-41和Cu-MCM-41孔道之中,但Cu-MCM-41表面和孤岛上的铜离子能高效光催化PDS产生1O2和SO4−·. UV+H2O2体系中加入Fe-MCM-41,金橙Ⅱ的脱色速率提升了52.9%,反应180 min时体系矿化率从43%提高到了57%;UV+PDS体系中加入Cu-MCM-41,金橙Ⅱ的脱色速率提升了38.7%,反应180 min时体系矿化率从48%提高到了76%. 本研究为介孔分子筛光催化剂的开发利用提供理论依据.Abstract: In this study, Fe-MCM-41 and Cu-MCM-41 were synthesized at room temperature and were characterized by XRD, BET, SEM and TEM techniques. In the heterogeneous photocatalytic oxidation system, Fe-MCM-41 and Cu-MCM-41, Orange Ⅱ, H2O2 and PDS were selected as catalysts, modal pollutant and oxidants, respectively. The structure-activity relationship of Fe-MCM-41 and Cu-MCM-41 on photocatalytic activation of H2O2 and PDS under neutral condition was discussed. The results showed that the configuration of Fe-MCM-41 was isomorphous substitution, and the configuration of Cu-MCM-41 was isomorphous substitution coexisting with CuO island. Under neutral condition, it was easy for H2O2 to enter the pore of Fe-MCM-41 or Cu-MCM-41 since H2O2 was less influenced by steric hindrance and electrical repulsion. ·OH could be efficiently generated through H2O2 photo-activation by iron ions inside and outside the pore of Fe-MCM-41, but it was difficult for H2O2 to be efficiently catalyzed by copper ions in Cu-MCM-41. It was hard for PDS to enter the pore of Fe-MCM-41 or Cu-MCM-41 due to the higher steric hindrance and electrical repulsion under neutral condition, but the copper ions on the surface of Cu-MCM-41 and CuO island could efficiently photo-activate PDS to produce 1O2 and SO4−·. When Fe-MCM-41 was added into UV+H2O2 system, the enhanced efficiency of Orange Ⅱ decolorization rate could reach 52.9%, and its mineralization increased from 43% to 57% at 180 min. When Cu-MCM-41 was added into UV+PDS system, the enhanced efficiency of Orange Ⅱ decolorization rate could reach 38.7%, and its mineralization increased from 48% to 76% at 180 min. This study provided a theoretical basis for the development and utilization of mesoporous molecular sieve photocatalysts.
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Key words:
- MCM-41 /
- H2O2 /
- PDS /
- photocatalytic activation /
- structure-activity relationship.
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表 1 不同体系中金橙Ⅱ脱色的一级动力学常数
Table 1. The first order kinetics of Orange Ⅱ degradation under different systems
反应体系
Reaction systemk/min−1 R2 UV+H2O2 0.017 1.000 UV+H2O2+Fe-MCM-41 0.026 0.981 UV+H2O2+Cu-MCM-41 0.015 0.997 UV+PDS 0.031 0.991 UV+PDS+Fe-MCM-41 0.028 0.993 UV+PDS+Cu-MCM-41 0.043 0.992 -
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