摘要
催化加氢脱氯是实现水中三氯生(triclosan,TCS)降毒去稳的有效方法.实际应用中,对贵金属催化剂的过度依赖和密闭的加压反应体系是制约该方法工业化应用的关键因素.本研究以阴极析氢反应产生的新生氢气(nascent H_(2),Nas-H_(2))作为雷尼镍(Raney Ni,R-Ni)催化剂的氢源,建立了温和条件下三氯生高效还原脱氯的催化加氢体系.结果表明,雷尼镍/新生氢气体系中三氯生的还原遵循准一级反应动力学,反应2.0 h后,三氯生的转化率为96.3%,脱氯率为68.8%.其中,雷尼镍活化新生氢气产生的吸附态氢原子(hydrogen adatoms,H^(*)_(ads))为反应性物种.为了深化三氯生加氢脱氯,向反应体系中引入超声波(ultrasonic,US),三氯生转化率及脱氯率分别增至99.0%和86.5%,新生氢气的原子利用率达到0.21%.超声增强的氢化性能归因于空化作用提高了雷尼镍催化活性,并将新生氢气泡破碎为易活化的纳米氢(nanoscale H_(2),Nano-H_(2))气泡,促进了H^(*)_(ads)的产生,增加了反应物种之间的有效碰撞次数.通过对反应中间产物的测定分析,提出了三氯生逐级加氢脱氯的反应去除机制,反应最终产物为2-羟基二苯醚.该研究可望应用于水中多卤代有机污染物的高效脱卤.
Triclosan(TCS)is a broad-spectrum antibacterial agent that has been widely used in medicines and personal care products,such as fungicide,disinfectants,soap,toothpaste,etc.Most of the products containing TCS after use enter the sewage treatment plant through domestic sewage.However,TCS entering the sewage treatment plant is only partially degraded due to its stable halogenated aromatic structure,and the remaining TCS and its by-products will enter the external environment.Studies have found that TCS in the aquatic environment exhibits significant biological toxicity to the growth and metabolism of algae,luminescent bacteria,zooplankton and fish.In addition,TCS will cause allergic dermatitis through direct contact with the human body through skin and oral cavity,and can also indirectly accumulate in the body through the food chain,thereby disrupting the body’s normal endocrine function.The development of efficient treatment technology for TCS in water has important theoretical significance and application value.Reductive dechlorination can effectively reduce the toxicity and stability of TCS(improve its biodegradability),and plays an important role in the restoration of TCS polluted water.The currently used reduction techniques include zero-valent iron reduction,electrochemical reduction,photochemical reduction and catalytic hydrogenation.Among them,catalytic hydrogenation has attracted wide attention due to its simple operation and high efficiency.However,its upscale application is being restricted by its excessive dependence on noble metal catalysts and the closed high-pressure environment constructed to improve hydrogenation efficiency.This work aims to improve the existing catalytic hydrogenation technology.Specifically,cheap and available Raney Ni(R-Ni)was selected as the hydrogenation catalyst,and tiny nascent H_(2)(Nas-H_(2))bubbles generated in situ by the cathode hydrogen evolution reaction were used as the hydrogen source.The effects of current density and catalyst dosage on TCS hydrodechlorination were studied.The experimental results showed that the reduction process of TCS in the R-Ni/Nas-H_(2)system followed a pseudo-first order reaction kinetics.The conversion and dechlorination ratios of TCS(C_(0)=30 mg/L)were 96.3%and 68.8%,respectively,within 2.0 h.Compared with the existing catalytic hydrogenation system,H_(2)consumption was significantly reduced(from≥10 m L/min to 1.05 m L/min),which was attributed to that the refined Nas-H_(2)bubbles were more likely to be activated by R-Ni due to their higher solubility and longer residence time in the reaction liquid.Furthermore,ultrasonic cavitation was introduced to achieve deep dechlorination of TCS.The conversion and dechlorination ratios of TCS increased to 99.0%and 86.5%,respectively,with 0.58 W/cm^(3)ultrasonic power density of the reaction solution,and the atom utilization ratio of Nas-H_(2)reached 0.21%.TCS reduction conformed to the catalytic hydrogenation mechanism of adsorption→activation→hydrogenation,and the hydrogen adatoms(H^(*)_(ads))were reactive species.The ultrasound-enhanced hydrogenation performance was attributed to the cavitation which improved the catalytic activity of R-Ni and blasted Nas-H_(2)into easily activatable nanoscale hydrogen(Nano-H_(2)),thereby promoting the production of H^(*)_(ads)and increasing the effective number of collisions between reactive species(H^(*)_(ads),TCS_(ads)).In addition,through the determination and analysis of the reaction intermediate products,the stepwise hydrodechlorination removal mechanism of TCS was proposed,and the final product was 2-hydroxydiphenyl ether.This research is expected to be applied to the efficient dehalogenation of polyhalogenated organic pollutants in water.
作者
王未来
吴雨
王凯旋
裴元生
牛军峰
Weilai Wang;Yu Wu;Kaixuan Wang;Yuansheng Pei;Junfeng Niu(State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University,Beijing 100875,China;Key Laboratory of Industrial Ecology and Environmental Engineering,Ministry of Education China,School of Environmental Science and Technology,Dalian University of Technology,Dalian 116024,China;Research Center for Eco-Environmental Engineering,Dongguan University of Technology,Dongguan 523808,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第15期1923-1932,共10页
Chinese Science Bulletin
基金
国家杰出青年科学基金(51625801)
广东省高校创新团队项目(2016KCXTD023)
广东省高等学校珠江学者岗位计划(2017)资助。
关键词
超声
雷尼镍
新生氢气
三氯生
还原脱氯
ultrasonic
Raney Ni
nascent H_(2)
triclosan
dechlorination
