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溴代阻燃剂(brominated flame retardants,BFRs)具有成本低、阻燃性能强及材料相容性好等优势,是产量最高的有机阻燃剂之一[1]. 其中,四溴双酚A(tetrabromobisphenol A,TBBPA)应用范围最广[2-3]. 目前TBBPA已在各种环境介质中被检出[4-7],且具有内分泌干扰性和生物毒性[8-9],因此TBBPA的处理研究已成为学者们关注的热点.
TBBPA的去除方法大致可分为物理法(萃取法和吸附法)、化学法(光降解法、超声波降解法、氧化法和还原法等)和生物法[10-14]. 其中,电催化还原技术具有降解效率高、反应条件温和、不生成有毒副产物等优点,被视为很有发展前景的有机物脱卤处理技术[15-17]. 催化剂是污染物成功降解的重要因素之一,而Pd具有较强的活化氢气的能力,且析氢电位较低,因此常被视为理想催化活性组分[18-19]. 现有研究通常将催化剂固定在电极表面并以此作为阴极电极,但存在活性组分利用率低的问题[20].
本文采用浸渍法将Pd负载到不同载体上,将制备的催化剂均匀分散于阴极反应池中对TBBPA进行电催化还原脱溴,研究了载体、负载量和电流大小对反应初活性的影响,并对催化剂的可重复利用性进行评估.
Pd/TiO2催化水体中四溴双酚A的电催化还原脱溴
Study on electrocatalytic reduction of tetrabromobisphenol A on Pd/TiO2 in water
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摘要: 以TiO2、Al2O3、CeO2和SiO2为载体,采用浸渍法制备Pd基催化剂,并通过透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电感耦合等离子体发射光谱(ICP-OES)等手段对催化剂的结构进行了详细表征. 以Pd/TiO2为催化剂,研究四溴双酚A(TBBPA)在阴极池的电催化还原. 结果表明,悬浮体系中Pd基催化剂的催化活性远高于固定体系;与其他载体相比,Pd/TiO2的电催化还原活性最高;反应过程符合Langmuir-Hinshelwood模型,受控于TBBPA在催化剂表面的吸附过程;随着恒定电流和Pd负载量的增大,TBBPA电催化还原反应的初活性呈现火山型变化规律;经过5次循环使用,Pd/TiO2催化剂仍能够完全去除TBBPA,具有良好的稳定性.Abstract: We prepared Pd based catalysts by the impregnation method with TiO2, Al2O3, CeO2 and SiO2 as the supports, and the structural properties of the catalysts were characterized by TEM, XRD, XPS and ICP-OES. The electrocatalytic debromination of tetrabromobisphenol A (TBBPA) was studied on Pd/TiO2. The results showed that the activity of Pd/TiO2 catalyst in suspension system was much higher than that in fixed system. The Pd/TiO2 catalyst had the highest electrocatalytic debromination activity among the test catalysts. The reaction process complied with the Langmuir-Hinshelwood model, and was controlled by the adsorption of TBBPA on the catalyst surface. With the increase of constant current and loading amounts of Pd, the initial activity of the catalyst for electrocatalytic reduction of TBBPA displayed a volcano-type dependency. Furthermore, complete debromination of TBBPA could be achieved on suspended Pd/TiO2 catalyst after five catalyst cycles, suggesting very high catalyst stability.
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Key words:
- electrocatalytic reduction /
- tetrabromobisphenol A /
- suspension system /
- Pd/TiO2.
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图 11 不同浓度叔丁醇对(a)TBBPA的电催化还原反应及(b)反应初活性的影响;不同电流条件下叔丁醇对(c)TBBPA的电催化还原反应及(d)反应初活性的影响
Figure 11. Effect of tert butyl alcohol with different initial concentration on (a) Electrocatalytic reduction of TBBPA and (b) Initial activity; Effect of tert butyl alcohol under different working current on (c) Electrocatalytic reduction of TBBPA and (d) Initial activity
表 1 催化剂的基本性质
Table 1. Basic properties of the catalysts
催化剂
CatalystPd实际负载量/ % a
Loading amount of PdPd平均粒径/ nm b
Average particle size of Pd表面电荷/ mV c
Surface chargePdn+/Pd0 Pd(0.45)/TiO2 0.45 1.78 N.D. 1.62 Pd(1.11)/TiO2 1.11 3.12 N.D. 1.38 Pd(1.99)/TiO2 1.99 3.63 -31.3 0.90 Pd(2.98)/TiO2 2.98 3.70 N.D. 0.61 Pd(2.15)/Al2O3 2.15 N.D. -33.0 N.D. Pd(2.04)/CeO2 2.04 N.D. -35.5 N.D. Pd(2.23)/SiO2 2.23 N.D. -36.4 N.D. 注:a电感耦合等离子发射光谱仪;b透射电子显微镜;c Zeta电位仪(pH=10.5);N.D.未测定 Notes:a ICP-OES; b TEM; c Zeta potentiometer(pH=10.5); N.D. means not determined. -
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