pH对低温燃烧法合成钨酸铋光催化降解罗丹明B的影响

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余忠雄, 向垒, 钟方龙, 李彦文, 莫测辉, 蔡全英, 黄献培, 吴小莲, 赵海明. pH对低温燃烧法合成钨酸铋光催化降解罗丹明B的影响. 无机材料学报, 2015, 30(5): 535-541
YU Zhong-Xiong, XIANG Lei, ZHONG Fang-Long, LI Yan-Wen, MO Ce-Hui, CAI Quan-Ying, HUANG Xian-Pei, WU Xiao-Lian, ZHAO Hai-Ming. Effects of Solution pH on Photocatalytic Degradation of Rhodamine B Using Bismuth Tungstate Prepared by Low-temperature Combustion Method. Journal of lnorganic Materials,2015, 30(5): 535-541 复制到剪切板

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pH对低温燃烧法合成钨酸铋光催化降解罗丹明B的影响

余忠雄¹, 向垒^1,², 钟方龙¹, 李彦文^1,², 莫测辉¹, 蔡全英¹, 黄献培^1,², 吴小莲^1,², 赵海明^1,²

暨南大学 1. 环境学院, 广东省高校水土环境毒害性污染物防治与生物修复重点实验室

2. 生态学系, 广州 510632

莫测辉, 教授. E-mail: tchmo@jnu.edu.cn; 向垒, 博士. E-mail: wuxian622622@163.com

作者简介: 余忠雄(1989-), 男, 硕士研究生. E-mail: 792965158@qq.com

基金:国家自然科学基金(41173101, 41301337); 广东省自然科学基金重点项目(2011020003196); 广东省高校高层次人才项目; 东莞市科技计划项目(2012108102043)

摘要

以低温燃烧法制备钨酸铋(LCM-Bi₂WO₆), 并表征了其晶体结构、形貌特征、等电点及紫外漫反射谱, 同时以染料罗丹明B(RhB)为目标污染物(25 mg/L, pH=4), 考察了所制备Bi₂WO₆的吸附性能和光催化性能, 并探讨了RhB溶液pH(1、4、7、10)及酸度调节剂成分(盐酸和硫酸)的影响。结果表明, 所制备Bi₂WO₆为正交相, 吸收极限波长为455 nm, 禁带宽度为2.72 eV, 晶格粒径为14.7 nm, 等电点为3.43; 其对RhB的吸附和光催化效果强于水热法制备Bi₂WO₆和二氧化钛(TiO₂)。不同pH溶液中, LCM-Bi₂WO₆对RhB的吸附过程和光催化过程分别符合准二级动力学方程和一级动力学方程式, 且吸附平衡量(7.48~21.93 mg/g)和光催化速率常数(0.0197~0.1181 min^-1)均随pH降低而增大。LCM-Bi₂WO₆对RhB的光催化降解主要由·OH所致。光催化过程中, RhB紫外可见光谱的蓝移现象揭示LCM-Bi₂WO₆可通过脱乙基-共轭显色基团断裂途径降解RhB。以H₂SO₄调节酸度时, SO₄^2-离子可被Bi₂WO₆强吸附, 从而使得LCM-Bi₂WO₆对RhB的平衡吸附量( q_e为6.03 mg/g)和光催化速率( k_v为0.115 min^-1)远小于HCl调节( q_e为21.93 mg/g, k_v为0.1181 min^-1)时对RhB的平衡吸附量和光催化速率。

关键词: 低温燃烧法; 钨酸铋; 光催化; pH

中图分类号:TG174 文献标志码:A 文章编号:1000-324X(2015)05-0535-07

Effects of Solution pH on Photocatalytic Degradation of Rhodamine B Using Bismuth Tungstate Prepared by Low-temperature Combustion Method

YU Zhong-Xiong¹, XIANG Lei^1,², ZHONG Fang-Long¹, LI Yan-Wen^1,², MO Ce-Hui¹, CAI Quan-Ying¹, HUANG Xian-Pei^1,², WU Xiao-Lian^1,², ZHAO Hai-Ming^1,²

1. School of Environment, Jinan University, Key Laboratory of Water/Soil Toxic Pollutants Control and Bioremediation of Guangdong Higher Education Institutions, Guangzhou 510632,China

2. Department of Ecology, Jinan University, Guangzhou 510632, China

Fund:National Natural Science Foundation of China (41173101, 41301337); National Natural Science Foundation of Guangdong Province(2011020003196); High-Leveled Talents Project of Guangdong Province’s University; Scientific Research Program of Dongguan (2012108102043)

Abstract

Bismuth tungstate (Bi₂WO₆) was synthesized by low-temperature combustion method (LCM) and characterized by diffuse reflectance spectroscope (DRS), X-ray diffraction (XRD), scanning electron microscope (SEM) and Zeta potential. The effects of solution pH and acidity regulator types on the photocatalytic degradation of RhB by LCM-Bi₂WO₆ were investigated. Results showed that LCM-Bi₂WO₆ was an orthorhombic crystal and its wavelength of maximum absorption, forbid bandwidth, lattice size and isoelectric point were 455 nm, 2.72 eV, 14.7 nm and 3.43, respectively. Stronger adsorption and photodegradation of RhB (25 mg/L, pH=4) using LCM-Bi₂WO₆as photocatalyst was observed, compared with using TiO₂ or Bi₂WO₆ prepared by hydrothermal method as photocatalyst. Adsorption and photodegradation of RhB by LCM-Bi₂WO₆satisfied the pseudo-second-order kinetic equations and first order kinetic equations, respectively. Equilibrated adsorption capacity (7.48-21.93 mg/g) and photodegradation rate constants (0.0197-0.1181 min^-1) of RhB by LCM-Bi₂WO₆ were positively related to solution pH. Photocatalytic degradation of RhB by LCM-Bi₂WO₆ was mainly triggered by free hydroxyl groups (•OH). Blue shifts of RhB ultraviolet-visible spectrum indicated its degradation through ethyl removal and conjugated groups break pathway. Weaker adsorption ( q_e=6.03 mg/g) and photodegradation ( k_v=0.115 min^-1) of RhB by LCM-Bi₂WO₆using H₂SO₄ as acidity regulator were observed compared with using HCl ( q_e=21.93 mg/g, k_v=0.115 min^-1) as acidity regulator, because of SO₄^2-strong adsorption to LCM-Bi₂WO₆.

Keyword: low-temperature combustion method; Bi2WO6; photocatalysis; pH value

Show Figures

钨酸铋(Bi₂WO₆)是一种高效、低毒且稳定性好的光催化材料, 其禁带宽度较窄(仅为2.80 eV左右), 可利用近紫外光(300~400 nm)甚至是太阳光, 催化去除水中有机污染物^[1]。因此, Bi₂WO₆在水污染处理方面具有重要应用价值, 已成为研究热点问题^[2]。

Bi₂WO₆的制备方法主要包括固相反应法^[3]和水热法^{[4, 5, 6, 7]}等, 但这些方法大多反应复杂、耗时长、能耗大^[8], 探索Bi₂WO₆的新型制备方法十分必要^[9]。低温燃烧法(Low-temperature Combustion Method, LCM)是以可溶性金属盐(主要为硝酸盐)作为氧化剂, 以有机燃料(如氨基乙酸、尿素、柠檬酸等)作为还原剂, 将二者在一定温度下点燃后引发化学反应制备材料的方法^[10]。该方法制备材料的能量由反应体系放出的热量提供, 反应过程中放出大量气体, 使得制备材料质地疏松、不易结块, 是合成纳米材料的理想方法。另外, 该方法反应条件简单、均匀性高, 制备过程迅速, 可规模化生产应用^[11]。然而, 采用LCM制备Bi₂WO₆的研究鲜见报道^[12], 反应条件(如pH值等)对其光催化性能的影响报道亦少。

本工作以LCM制备Bi₂WO₆, 通过XRD衍射仪、扫描电镜(SEM)、Zeta电位仪和紫外-可见分光光度计等表征其晶体结构、形貌特征、等电点及紫外漫反射谱; 同时, 考察了溶液pH和酸度调节剂种类对Bi₂WO₆光催化降解模式污染物罗丹明B(RhB)的影响。

1 实验方法

1.1 试剂和仪器

硝酸铋(Bi(NO₃)₃· 5H₂O)和钨酸钠(Na₂WO₄· 2H₂O)为ACS级, 氨基乙酸(C₂H₅NO₂)、无水乙醇(C₂H₅OH)、氢氧化钠(NaOH)、盐酸(HCl)、硫酸(H₂SO₄)和罗丹明B(C₂₈H₃₁ClN₂O₃)均为分析纯。二氧化钛(TiO₂), 纯度99.5%, 购自杭州万景科技有限公司, 实验用水均为双蒸水。采用D/MAX型(Rigaku, 日本)XRD衍射仪(CuKα 、36 kV、20 mA)测定LCM制备Bi₂WO₆的结构特征, 测定波长λ 为0.15406 nm, 2θ 的扫描范围、速度和步长分别为20° ~70° 、8° /min和0.02° 。采用场发射扫描电镜(JSM-6330F, 日本)观察LCM制备Bi₂WO₆的形貌特征。采用带积分球的紫外可见分光光度计(U-3010型, 日本), 以BaSO₄为参比, 测定LCM制备Bi₂WO₆的紫外-可见漫反射光谱。准确配置pH为1~7的Bi₂WO₆悬浮液, 采用Zeta电位仪(nano-ZS, 英国马尔文)测定其Zeta电位, 并以pH值和Zeta电位进行线性拟合, 从而求得所制备Bi₂WO₆等电点。

1.2 样品制备

将2 mmol硝酸铋(Bi(NO₃)₃· 5H₂O)和1 mmol钨酸钠分别溶于2 mL硝酸(2 mol/L)和30 mL含一定量氨基乙酸(C₂H₅NO₂)的双蒸水中, 制得钨酸钠溶液和硝酸铋溶液。二者在200 mL烧杯中混合后得到乳白色悬浮液, 即纳米Bi₂WO₆的前驱体。将盛放Bi₂WO₆前驱体的烧杯在预热至200℃的控温电热板上加热反应并不断搅拌, 当温度达到C₂H₅NO₂的分解温度时, 反应体系开始自蔓延燃烧, 并伴随大量气体逸出, 此时烧杯中生成淡黄色疏松物质。待自蔓延反应完成后, 收集烧杯中生成的淡黄色疏松物质, 依次用蒸馏水和无水乙醇离心洗涤各3次后, 再置于60℃的恒温烘箱干燥后, 即得到Bi₂WO₆粉体(记作LCM-Bi₂WO₆)。另外, 采用水热法^[13]合成Bi₂WO₆(记作水热法- Bi₂WO₆)。

1.3 吸附性能

配制300 mL RhB溶液(25 mg/L), 加入0.3 g Bi₂WO₆, 在磁力搅拌(JB-2型, 上海)条件下(200 r/min), 避光进行吸附实验。每隔15 min取样1次, 过0.22 µ m滤膜, 滤液用TU-1810/1810S型紫外-可见分光光度计(普析通用, 北京)在λ =554 nm处检测其吸光度, 并根据标准曲线求出滤液中RhB的浓度。以时间(t)为横坐标, 吸附率(某时刻滤液中RhB的浓度与RhB溶液初始浓度之比)为纵坐标绘制曲线, 表征制备Bi₂WO₆对RhB的吸附性能。

1.4 光催化性能

配制300 mL RhB溶液(25 mg/L), 加入0.3 g Bi₂WO₆, 避光磁力搅拌30 min使之达到吸附-解吸平衡(根据吸附实验结果), 此过程为暗反应阶段。之后, 用125 W高压汞灯(GGZ-125型)作为反应光源(加365 nm滤光片, 保证光波长在300~400 nm), 在磁力搅拌器作用下(200 r/min)进行光催化实验(光反应阶段)。每隔15 min取样1次过0.22 µ m滤膜, 检测其吸光度, 并根据标准曲线求出滤液中RhB的浓度。以时间(t)为横坐标, 去除率(某时刻滤液中RhB的浓度与RhB溶液初始浓度之比)为纵坐标绘制曲线, 以此表征纳米LCM-Bi₂WO₆的光催化性能。同时, 根据上述实验方法和步骤, 分别进行水热法合成Bi₂WO₆以及二氧化钛(TiO₂)对RhB的光催化降解实验, 以此比较LCM-Bi₂WO₆、水热法-Bi₂WO₆以及TiO₂三者间光催化性能的差异。

1.5 溶液pH对吸附性能和光催化性能的影响

为了考察pH对LCM法制备Bi₂WO₆吸附性能和光催化性能的影响, 以0.1 mol/L盐酸(硫酸)或0.1 mol/L氢氧化钠分别调节RhB溶液pH为1、4 (RhB原溶液的pH)、7、10, 然后再分别测试吸附性能和光催化性能。

2 实验结果与讨论

2.1 物相表征

XRD分析显示, LCM-Bi₂WO₆各衍射峰(2θ )位置均与正交相Bi₂WO₆(JCPDS 39-0256)衍射峰位置一致, 无杂峰出现(图1(a)), 表明其均为纯正交相Bi₂WO₆。根据Debye-Scherrer公式计算晶粒粒径分别为14.7 nm。

扫描电镜(SEM)观察结果显示, LCM-Bi₂WO₆粉体呈不规则微粒状(图1(b)), 存在团聚现象。采用Zeta电位仪测定了不同pH条件下LCM-Bi₂WO₆的Zeta电位, 求出其等电点为3.43。根据LCM-Bi₂WO₆的紫外漫反射谱及切线法可知, 其吸收极限波长为455 nm, 用吸收极限波长与禁带宽度的关系式(1), 求得其禁带宽度为2.72 eV(图1(c))。

E_g= hc/λ ₀= 1240/λ ₀(1)

式中E_g为禁带宽度; h为普朗克常数, 其值为6.6218× 10^-34Js; c为光速, 其值为3× 10⁸m/s; λ ₀为吸收极限波长。

2.2 LCM法制备Bi₂WO₆的光催化性能

以RhB(pH=4, 25 mg/L)为目标降解物, 以水热法-Bi₂WO₆以及TiO₂为对照, 研究了 LCM-Bi₂WO₆的光催化性能如图2所示。结果显示, 暗反应阶段, LCM-Bi₂WO₆对RhB的吸附(13.81 mg/g)高于水热法-Bi₂WO₆(6.75 mg/g)和TiO₂(0.05 mg/g)。同样地, 在光反应阶段, LCM-Bi₂WO₆对RhB的降解效率也高于水热法-Bi₂WO₆和TiO₂。150 min内, LCM-Bi₂WO₆可对RhB完全脱色降解, 而水热法- Bi₂WO₆和TiO₂对RhB的脱色效率分别只有80%和62%。可见, LCM法制备Bi₂WO₆具有较强的光催化活性和应用前景。

2.3 pH对LCM法制备Bi₂WO₆的吸附性能的影响

不同溶液pH条件下, LCM-Bi₂WO₆对RhB吸附均较为迅速, 在30 min内即可达到吸附平衡(见图3), 且吸附过程均较好符合准二级动力学方程式(式(2)), 相关系数R²大于0.9995。

t/q_t=1/kq_e²+1/q_et (2)

式中t为采样时间(min), k为准二级动力学方程常数, q_e为平衡吸附量(mg/g)。

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	图1 低温燃烧法制备Bi₂WO₆的物相表征结果Fig. 1 Phase characterization of Bi₂WO₆ prepared by low-temperature combustion method (a) XRD pattern; (b) SEM image; (c) UV-Vis diffuse reflectance spectrum

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	图2 不同催化剂对RhB的光催化降解曲线Fig. 2 Photocatalytic degradation of RhB using different catalysts (a) Bi₂WO₆Bi₂WO₆ prepared by low-temperature combustion method; (b) Bi₂WO₆ prepared by hydrothermal method; (c) TiO₂

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	图3 不同pH条件下低温燃烧法-Bi₂WO₆对RhB的吸附曲线Fig. 3 Adsorption of RhB on Bi₂WO₆prepared by low teper ature combustion method at different pH solutions

值得注意的是, RhB溶液pH越低, LCM-Bi₂WO₆对其的平衡吸附量(q_e)越大。当RhB溶液pH=1时, LCM-Bi₂WO₆对RhB 的q_e值达到21.93 mg/g, 分别为pH=4、pH=7以及pH=10条件下的1.59倍、2.49倍以及2.93倍(表1)。有研究显示, Bi₂WO₆可通过电性引力以及其吸附活性中心吸附RhB, 其中pH越低, 活性中心作用越强^[14]。LCM-Bi₂WO₆的等电点为3.43, 当pH为1时, 其表面带正电, 难以通过电性引力吸附同样带正电的RhB, 但此时Bi₂WO₆酸性中心活性较强, 可通过对N原子孤对电子的共价作用强烈吸附RhB。随着溶液pH的升高, Bi₂WO₆表面正电荷逐渐减少, 负电荷增加, 其对RhB的电性吸附作用增强, 而共价吸附作用减弱。当pH为10时, Bi₂WO₆主要通过电性引力吸附RhB。由于酸性中心共价作用的强度远强于静电吸附作用。因此, pH越低, Bi₂WO₆对RhB吸附作用越强。

表1 不同pH条件下LCM-Bi₂WO₆对RhB的吸附动力学参数 Table1 Kinetics parameters of RhB sorption to Bi₂WO₆ prepared by low-temperature combustion method in different pH solutions

2.4 pH对LCM法制备Bi₂WO₆的光催化性能的影响

不同溶液pH条件下, 近紫外光对RhB的光降解过程(未添加纳米LCM-Bi₂WO₆)以及LCM- Bi₂WO₆对RhB的光催化过程均符合一级动力学反应方程式(式(3)), 且呈现RhB溶液pH越低, 其降解速率常数(k_v)越大的特征(图4)。此结果表明, 酸性越强越有利于LCM-Bi₂WO₆对RhB的光催化降解, 这与Bi₂WO₆吸附活性中心对RhB吸附作用随溶液pH降低而增强有关。文献[15]研究Bi₂WO₆近紫外光催化降解微囊藻毒素得到相同结果。

ln(C_t/C₀)=a-k_vt (3)

式中t为采样时间点(min), C_t(mg/L)为t时刻溶液中罗丹明B的浓度, C₀为初始浓度, a为一级反应动力学常数, k_v为一级反应动力学速率常数, 其值越大表明反应速率越快。

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	图4 不同pH条件下低温燃烧法-Bi₂WO₆对RhB的光催化降解曲线Fig. 4 Effects of solution pH on the photocatalytic degradation of RhB with Bi₂WO₆ prepared by low-temperature combustion method

值得注意的是, LCM-Bi₂WO₆对RhB的光催化速率常数在0.0203~0.1201 min^-1之间, 比近紫外光(未添加Bi₂WO₆)对RhB的光降解速率常数(0.0003~ 0.0081 min^-1)高1~2个数量级(表2)。为了表征LCM-Bi₂WO₆光催化降解机理, 考察了典型羟基自由基(· OH)捕获剂二甲基亚砜(DMSO)对其光催化降解RhB的影响。结果表明, 10%DMSO(v/v)显著抑制了LCM-Bi₂WO₆对RhB(pH=4)的光催化降解, 150 min内的降解抑制率高达75%(图5), 表明LCM-Bi₂WO₆对RhB的光催化降解主要由· OH所致。未添加LCM-Bi₂WO₆时, RhB的降解主要由近紫外光分解水分子产生的羟基自由基(· OH)造成, 此过程· OH产生速率较低, 故RhB降解速率较慢; 添加LCM-Bi₂WO₆后, 其价带电子吸收近紫外光, 激发跃迁至导带, 从而形成电子(e^-)-空穴(h⁺)对, h⁺与e^-分别与溶液中的水分子(H₂O)和溶解氧(O₂)反应生成· OH^[16], 这一过程产生· OH速率较快, 因而大幅提高RhB的降解速率。

图6显示了不同溶液pH条件下, LCM-Bi₂WO₆催化降解过程中RhB的紫外吸收光谱。不同pH溶液处理RhB的紫外-可见光谱在反应初期均出现吸收峰值降低的现象, 但未出现蓝移现象; 随着反应时间的增加, 各处理RhB的紫外-可见光谱吸收峰值继续下降, 并发生蓝移。溶液pH为1时, RhB吸收峰蓝移较少, 仅移至550 nm处; 而pH为4、7和10时, RhB吸收峰蓝移较多, 前两者吸收峰蓝移至530 nm处, 后者吸收峰蓝移至544 nm处。文献[17]研究显示, RhB特征吸收峰峰值(554 nm)的降低及其位置的蓝移分别指示RhB显色基团断裂和RhB氮原子所连乙基被脱除, 其中544和530 nm分别为RhB脱去一个乙基以及两个乙基生成中间产物的特征吸收峰。可见, LCM-Bi₂WO₆近紫外光催化降解RhB在反应初期以共轭显色基团直接断裂途径降解(途径Ⅰ ), 之后以脱乙基-共轭显色基团断裂途径降解(途径Ⅱ )。反应初期, RhB浓度较高, 作为光敏物质, 其在纳米LCM-Bi₂WO₆催化条件下吸收近紫外光, 直接发生共轭显色基团断裂的降解反应。随着反应时间的延长, RhB浓度逐渐降低, 光敏作用减弱, 且在Bi₂WO₆催化条件下, 溶液中产生大量· OH等活性氧化物质, 其脱去RhB分子上与N原子相连的乙基后, 才使RhB显色基团断裂, 即降解途径Ⅱ 。另外, 在强酸性条件下(pH=1), LCM- Bi₂WO₆对RhB的吸附/降解活性较强, RhB直接以途径Ⅰ 降解, 故其吸收峰值蓝移较少; 在强碱性条件下(pH=10), LCM-Bi₂WO₆对RhB的吸附/降解活性较弱, 故对RhB的脱乙基作用较弱, 经过150 min反应其吸收峰只迁移至544 nm处。

表2 不同pH条件下低温燃烧法-Bi₂WO₆降解RhB的动力学方程式 Table 2 Kinetics equations of RhB degradation using Bi₂WO₆prepared by low-temperature combustion method in different solution pH values

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	图5 DMSO对低温燃烧法-Bi₂WO₆光催化降解RhB的影响Fig. 5 Effects of DMSO on the photocatalytic degradation of RhB with Bi₂WO₆ prepared by low-temperature combustion method

2.5 不同pH酸调节剂对LCM-Bi₂WO₆光催化性能的影响

盐酸(HCl)和硫酸(H₂SO₄)均为常见的pH调节剂, 但是由于两者所带阴离子化合价态的差异, 调节同一反应溶液, 光催化效果可能相差很大。本实验考察了分别以0.1 mol/L HCl和0.1 mol/L H₂SO₄作为调节剂, 调节RhB溶液pH均为1时(调节时逐滴加入, 不存在回滴现象), LCM-Bi₂WO₆对二者处理的RhB光催化效果的差异。结果表明, 以HCl或H₂SO₄作为pH调节剂时, Bi₂WO₆对RhB的降解均符合一级动力学方程式(表3), 但在暗反应阶段, 前者处理Bi₂WO₆对RhB的吸附量为后者的3倍; 在光反应阶段, 前者处理中RhB降解速率常数(0.1201 min^-1)是后者处理的10倍(0.0117 min^-1), 即H₂SO₄为酸度调节剂不利LCM-Bi₂WO₆吸附和光催化降解RhB。同浓度的HCl和H₂SO₄调节相同溶液至同一pH时, HCl用量为H₂SO₄的2倍, 即调节完成后, 前者处理溶液中氯离子(Cl^-)浓度为后者处理中硫酸根浓度的2倍(SO₄^2-)。浓度较小的SO₄^2-, 抑制作用较强, 这与其酸性条件下在LCM-Bi₂WO₆表面的强吸附作用有关。图7表明, 以HCl或H₂SO₄调节酸度后, LCM- Bi₂WO₆ 的XRD图谱分别出现了H₂SO₄(JCPDS 74-1174)和氯化铝水合物的特征衍射峰(JCPDS 27-0011), 说明SO₄^2-和Cl^-吸附于LCM-Bi₂WO₆表面。同时, 当pH为1时, 带正电LCM-Bi₂WO₆(等电点为3.43)的吸附作用随阴离子化合价态呈指数增长^[18], 因此LCM-Bi₂WO₆更易吸附SO₄^2-。SO₄^2-的吸附, 一方面降低了对光的吸收利用, 另一方面影响其对RhB的吸附, 从而显著抑制Bi₂WO₆对RhB的光催化降解。

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	图6 不同pH条件下, 低温燃烧法-Bi₂WO₆光催化降解过程中RhB的紫外-可见吸收光谱图Fig. 6 UV-Vis absorption spectrum of RhB during its photocatalytic degradation with Bi₂WO₆ prepared by low-temperature combustion method in different pH solutions

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	图7 H₂SO₄(a)和HCl(b)酸度剂调节后低温燃烧法-Bi₂WO₆的XRD图谱Fig. 7 XRD patterns of Bi₂WO₆prepared by low-temperature combustion method using H₂SO₄ (a) and HCl (b) as acidity regulator

表3 不同酸度调节剂条件下低温燃烧法-Bi₂WO₆光催化降解RhB的动力学方程式 Table 3 Kinetics equations of RhB degradation with Bi₂WO₆prepared by low-temperature combustion method in different acidity regulators

1) 采用低温燃烧法制备获得的钨酸铋(LCM- Bi₂WO₆)对RhB的吸附和光催化效果强于水热法- Bi₂WO₆和TiO₂, 具有良好的应用潜力。

2) RhB溶液pH越低, LCM-Bi₂WO₆对RhB的吸附和光催化降解性能越强。LCM-Bi₂WO₆对RhB的光催化降解主要由· OH所致。

3) LCM-Bi₂WO₆可通过脱乙基-共轭显色基团断裂途径降解RhB。

4) 以HCl调节RhB溶液pH比H₂SO₄调节更有利于LCM-Bi₂WO₆对RhB的吸附和光催化降解。

参考文献

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[1]	ZHANG LI-SHA, WANG HUAN-LI, CHEN ZHI-GANG, et al. Bi₂WO₆ micro/nano-structures: synthesis, modifications and visible- light-driven photocatalytic applications. Applied Catalysis B-Environmental, 2011, 106(1/2): 1-13. [本文引用:1] [JCR: 5.825]
[2]	ZHANG LI-WU, ZHU YONG-FA. A review of controllable synthesis and enhancement of performances of bismuth tungstate visible- light-driven photocatalysts. Catalysis Science & Technology, 2012, 2(4): 694-706. [本文引用:1]
[3]	TANG JUN-WANG, ZOU ZHI-GANG, YE JIN-HUA. Photocatalytic decomposition of organic contaminants by Bi₂WO₆ under visible light irradiation. Catalysis Letters, 2004, 92(1/2): 53-56. [本文引用:1] [JCR: 2.244]
[4]	HUANG YI, SHEN YUE, WU JI-HUAI, et al. Synthesis and characterization of flower-like Bi₂WO₆ and its photocatalytic activity. Journal of Functional Materials, 2010, 41(1): 52-56. [本文引用:1] [CJCR: 0.588]
[5]	LAI SHU-TING, ZHANG PENG, ZHOU WU-YI, et al. Synthesis and properties of visible-light photocatalytic Bi₂WO₆ via microemulsion-assisted hydrothermal method. Journal of Inorganic Materials, 2012, 27(9): 945-950. [本文引用:1] [JCR: 0.537] [CJCR: 1.106]
[6]	LIU YU-MIN, LI ZI-JING, LV HUA, et al. Synthesis of hierarchical Bi₂WO₆ microspheres with high visible-light-driven photocatalytic activities by Sol-Gel-hydrothermal route. Materials Letters, 2013, 108(10): 84-87. ZHU ZHEN-FENG, YU HONG-GUANG, LI JUN-QI, et al. One step template-free synthesis of nest-like Bi₂WO₆ microspheres and enhanced photocatalytic activity. Journal of Functional Materials, 2012, 43(4): 409-413. [本文引用:1] [JCR: 2.224]
[7]	TANG PEI-SONG, CHEN HAI-FENG, CAO FENG. One-step preparation of bismuth tungstate nanodisks with visible-light photocatalytic activity. Materials Letters, 2012, 68(2): 171-173. [本文引用:1] [JCR: 2.224]
[8]	XU JIE-HUI, WANG WEN-ZHONG, SHANG MENG, et al. Efficient visible light induced degradation of organic contaminants by Bi₂WO₆ film on SiO₂ modified reticular substrate. Applied Catalysis B-Environmental, 2010, 93(3/4): 227-232. [本文引用:1] [JCR: 5.825]
[9]	SU XIN-TAI, YAN QING-ZHI, GE CHANG-CHUN. Recent developments of low-temperature combustion synthesis of ultrafine ceramic powder. Progress in Chemistry, 2005, 17(3): 430-436. [本文引用:1] [JCR: 0.67] [CJCR: 0.95]
[10]	LU LI-PING, ZHANG XI-YAN, BAI ZHAO-HUI, et al. Research progress of low-temperature combustion synthesis method. Journal of Changchun University of Science and Technology (Natural Science Edition), 2008, 31(3): 82-84. [本文引用:1]
[11]	ZHANG ZHI-JIE, WANG WEN-ZHONG, SHANG MENG, et al. Low-temperature combustion synthesis of Bi₂WO₆ nanoparticles as a visible-light-driven photocatalyst. Journal of Hazardous Materials, 2010, 177(1/3): 1013-1018. [本文引用:1] [JCR: 3.925]
[12]	SONG XU-CHUN, ZHENG YI-FAN, MA RONG, et al. Photocatalytic activities of Mo-doped Bi₂WO₆ three-dimensional hierarchical microspheres. Journal of Hazardous Materials, 2011, 192(1): 186-191. [本文引用:1] [JCR: 3.925]
[13]	SONG JI-MEI, WANG HONG, LI YA-PING, et al. Photocatalytic activity enhancement for 3D hierarchical Bi₂WO₆ microsphere and surface acidity. Science China Chemistry, 2013, 43(2): 163-170. [本文引用:1]
[14]	CHEN PENG, ZHU LING-YAN, FANG SHU-HONG, et al. Photocatalytic degradation efficiency and mechanism of microcystin-RR by mesoporous Bi₂WO₆ under near ultraviolet light. Environmental Science & Technology, 2012, 46(4): 2345-2351. [本文引用:1]
[15]	FU HONG-BO, PAN CHENG-SHI, YAO WEN-QING, et al. Visible- light-induced degradation of rhodamine B by nanosized Bi₂WO₆. Journal of Physical Chemistry B, 2005, 109(47): 22432-22439. [本文引用:1] [JCR: 3.607]
[16]	HE ZHONG, SUN CHENG, YANG SHAO-GUI, et al. Photocatalytic degradation of rhodamine B by Bi₂WO₆ with electron accepting agent under microwave irradiation: Mechanism and pathway. Journal of Hazardous Materials, 2009, 162(2/3): 1477-1486. [本文引用:1] [JCR: 3.925]
[17]	WANG CHUN-YING, ZHU LING-YAN, WEI MING-CUI, et al. Photolytic reaction mechanism and impacts of coexisting substances on photodegradation of bisphenol A by Bi₂WO₆ in water. Water Research, 2012, 46(3): 845-853. [本文引用:1] [JCR: 4.655]

2011

5.825

0.0

... 80 eV左右), 可利用近紫外光(300~400 nm)甚至是太阳光,催化去除水中有机污染物^[1] ...

2012

0.0

... 因此, Bi₂WO₆在水污染处理方面具有重要应用价值, 已成为研究热点问题^[2] ...

2004

2.244

0.0

Catalysis Letters. 2004, 92(1/2):53-56

Photocatalytic decomposition of organic contaminants by Bi₂WO₆ under visible light irradiation.

TANG JUN-WANG , ZOU ZHI-GANG , YE JIN-HUA.

An oxide photocatalyst Bi 2 WO 6 with corner-shared WO 6 octahedral layered structure was synthesized. Its band gap was determined to be 2.69 eV from UV–vis diffuse reflectance spectra. The photocatalyst showed not only the activity for photocatalytic O 2 evolution with the initial evolution rate of 2.0 μmol/h but also the activity of mineralizing both CHCl 3 and CH 3 CHO contaminants under visible light irradiation. Meanwhile, wavelength dependence of CH 3 CHO decomposition was observed, which indicated that the photocatalytic activity of the photocatalyst was in good agreement with its light-absorption ability.

... Bi₂WO₆的制备方法主要包括固相反应法^[3]和水热法^[4,5,6,7]等, 但这些方法大多反应复杂、耗时长、能耗大^[8], 探索Bi₂WO₆的新型制备方法十分必要^[9] ...

2010

0.0

0.588

2012

0.537

1.106

Journal of Inorganic Materials. 2012, 27(9):945-950

Synthesis and properties of visible-light photocatalytic Bi₂WO₆ via microemulsion-assisted hydrothermal method.

LAI SHU-TING , ZHANG PENG , ZHOU WU-YI

The novel Bi 2 WO 6 and Fe 3+ /Bi 2 WO 6 photocatalysts were fabricated separately via a reverse microemulsion method. The effect factors including synthesis temperature, pH value, molar ratio of water to surfactant (ω) and Fe 3+ doping on the structure, morphologies and photocatalysis performance of photocatalysts were studied in detail. These results show that Bi 2 WO 6 possesses a high degree of crystallinity of nano-spherical structure with the size of 15–25 nm. The photodegradation rate of methylene blue (MB) is 93.8% as the Bi 2 WO 6 photocatalyst was synthesized at 150℃. The results reveal that the photodegradation rate of MB reaches 97.8% as ω is 27. It is found that the photodegradation rate of MB for 1.03% Fe-doped Bi 2 WO 6 sample has increased to 90.2%, which is two times higher than that of pure Bi 2 WO 6 .

2013

2.224

0.0

Materials Letters. 2013, 108(10):84-87

Synthesis of hierarchical Bi₂WO₆ microspheres with high visible-light-driven photocatalytic activities by Sol-Gel-hydrothermal route.

ZHU ZHEN-FENG , YU HONG-GUANG , LI JUN-QI

Bi 2 WO 6 samples with hierarchical microspheres structures built by higher order 2D nanoplate alignment were successfully synthesized by sol–gel-hydrothermal route. The structures and morphologies of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis diffuse reflectance spectra indicated that as-prepared Bi 2 WO 6 with hierarchical microspheres structures had enhanced absorption in both UV and visible light areas. Photocatalytic activities of the samples were evaluated by the degradation of methylene blue (MB) under visible light irradiation. Due to the unique morphology and porous structure, the hierarchical Bi 2 WO 6 microspheres exhibited better photocatalytic activities than that of the Bi 2 WO 6 prepared by hydrothermal routes.

2012

2.224

0.0

Materials Letters. 2012, 68(2):171-173

One-step preparation of bismuth tungstate nanodisks with visible-light photocatalytic activity.

TANG PEI-SONG , CHEN HAI-FENG , CAO FENG.

Bismuth Tungstate (Bi 2 WO 6 ) nanodisks were synthesized using Bi (NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O as starting materials by a one-step hydrothermal process in the presence of ethylene glycol. The prepared sample was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), Brunauer–Emmett–Teller (BET) measurement, Fourier transform infrared spectroscopy (FTIR) and UV–visible diffuse reflectance spectrum (DRS). The prepared Bi 2 WO 6 nanodisks consist of fine particles and possess an optical band gap of 2.76 eV. The photocatalytic experiment demonstrates that the prepared Bi 2 WO 6 nanodisks exhibit high photocatalytic activity for decomposition of Rhodamine B under visible-light, which is ascribed to the unique shaped structures as well as narrow optical band gap.

2010

5.825

0.0

2005

0.67

0.95

2008

0.0

... 低温燃烧法(Low-temperature Combustion Method, LCM)是以可溶性金属盐(主要为硝酸盐)作为氧化剂, 以有机燃料(如氨基乙酸、尿素、柠檬酸等)作为还原剂, 将二者在一定温度下点燃后引发化学反应制备材料的方法^[10] ...

2010

3.925

0.0

Journal of Hazardous Materials. 2010, 177(1/3):1013-1018

Low-temperature combustion synthesis of Bi₂WO₆ nanoparticles as a visible-light-driven photocatalyst.

ZHANG ZHI-JIE , WANG WEN-ZHONG , SHANG MENG

References Figures and tables ADVERTISEMENT Journal of Hazardous Materials Volume 177, Issues 1–3 , 15 May 2010, Pages 1013–1018 Low-temperature combustion synthesis of Bi 2 WO 6 nanoparticles as a visible-light-driven photocatalyst Zhijie Zhang , Wenzhong Wang , , Meng Shang , Wenzong Yin Show more Choose an option to locate/access this article: Check if you have access through your login credentials or your institution Check access Purchase $41.95 doi:10.1016/j.jhazmat.2010.01.020 Get rights and content Abstract Visible-light-induced Bi 2 WO 6 photocatalyst has been successfully synthesized via a facile low-temperature combustion synthesis method, using glycine as the fuel. The photocatalytic activities of the as-synthesized samples were evaluated by the photodegradation of rhodamine B (RhB) and phenol under visible-light irradiation ( λ > 420 nm). The results showed that the molar ratio of fuel to oxidizer had an important influence on the photocatalytic activities of the products. When the molar ratio of fuel to oxidizer was 1, the photocatalyst exhibited the highest degradation efficiency, which can completely degrade RhB with a concentration up to 10 −4 M within 75 min. Besides decoloring, the markable reduction of chemical oxygen demand (COD) was also observed in the degradation of RhB, further demonstrating the photocatalytic performance of Bi 2 WO 6 . Additionally, the photocatalyst showed much enhanced visible photocatalytic efficiency, up to 94.2% in 4 h, than the bulk Bi 2 WO 6 powder (SSR) in the degradation of phenol.

... 另外, 该方法反应条件简单、均匀性高, 制备过程迅速, 可规模化生产应用^[11] ...

2011

3.925

0.0

... 然而, 采用LCM制备Bi₂WO₆的研究鲜见报道^[12], 反应条件(如pH值等)对其光催化性能的影响报道亦少 ...

2013

0.0

... 另外, 采用水热法^[13]合成Bi₂WO₆(记作水热法- Bi₂WO₆) ...

2012

0.0

... 有研究显示, Bi₂WO₆可通过电性引力以及其吸附活性中心吸附RhB, 其中pH越低, 活性中心作用越强^[14] ...

2005

3.607

0.0

Journal of Physical Chemistry B. 2005, 109(47):22432-22439

Visible- light-induced degradation of rhodamine B by nanosized Bi₂WO₆.

FU HONG-BO , PAN CHENG-SHI , YAO WEN-QING

Visible-light-induced photodegradation of rhodamine B over nanosized Bi 2 WO 6 has been observed. Bi 2 WO 6 exhibited a high photoactivity to photodegrade rhodamine B in the central pH solution under visible irradiation (λ > 420 nm). After five recycles for the photodegradation of rhodamine B, the catalyst did not exhibit any significant loss of activity, confirming the photocatalyst is essentially stable. The total organic carbon measurement displayed that a high degree of mineralization was achieved in the present photochemical system. The results of density functional theory calculation illuminated that the visible-light absorption band in the Bi 2 WO 6 catalyst is attributed to the band transition from the hybrid orbitals of Bi6s and O2p to the W5d orbitals. The Bi 2 WO 6 -assisted photocatalytic degradation of rhodamine occurs via two competitive processes: a photocatalytic process and a photosensitized process. The transformation of rhodamine is mainly via the photocatalytic process. Kinetic studies by using electron spin resonance and the radical scavenger technologies suggest that •OH is not the dominant photooxidant. Direct hole transfers and O 2 •- could take part in Bi 2 WO 6 photocatalysis. This study provided a possible treatment approach for organic pollutants by using visible light in aqueous ecosystems.

2009

3.925

0.0

... OH^[16], 这一过程产生#cod#x000b7 ...

2012

4.655

0.0