【作者】 康艳红；

【导师】 薛向欣；

【作者基本信息】 东北大学 ， 冶金资源与生态环境， 2009， 博士

【摘要】 硝基苯(NB)是环境中典型的持久性有机污染物(POP),由于其高度的稳定性和杀菌性,普通的生物、化学方法很难将其降解。本文从环境污染防治和半导体催化材料制备的低成本出发,提出以钛精矿、高钛渣和含钛高炉渣作为催化材料降解硝基苯,研究光、电、超声、热氧化等对硝基苯降解的协同作用,分析光、电、超声、热氧化条件下的硝基苯催化降解反应机理和动力学,优化硝基苯降解条件,评价了处理后硝基苯废水的BOD、COD、TOC等生化指标。(1)以含钛矿物为催化剂,利用365 nm高压汞灯、365 nm低压汞灯、254 nm低压汞灯和室内自然光处理含硝基苯废水,并用高效液相色谱(HPLC)分别对产物进行了分析。实验结果表明,光源对硝基苯的降解能力为365 nm高压汞灯>254nm低压汞灯>365 nm低压汞灯,室内自然光对硝基苯无降解作用。365 nm的高压汞灯作用下,90 min硝基本降解率达100%,总有机碳去除率为78.52%,有降解中间产物℡间硝基酚产生,并未达到深度降解。含钛矿物对硝基苯降解具有一定的光催化活性,催化能力为高钛渣>钛精矿>攀钢渣>承钢渣,与矿渣的含钛量成正相关。在pH 3-11的范围内,酸度变化对硝基苯降解率的影响不显著,酸性条件稍有利于反应进行。(2)以含钛矿物催化剂粉体1%的碳糊电极为工作电极,对硝基苯在三电极体系中进行电化学测量,实验结果表明：硝基苯在碳糊电极上发生不可逆还原反应,产物为苯胺,不发生氧化反应。硝基苯在电极上的还原反应由扩散步骤控制,在酸性介质中,室温下硝基苯电还原的表观活化能为14.11 kJ·mol-1,其活化能较低,表明硝基苯较易在碳糊电极上还原。在惰性双电极体系中,硝基苯还原为苯胺的反应符合一级动力学方程,反应表观速率常数k=0.01895 min-1。实验条件下,当电解时间达40 min时,BOD5/COD值由0.07提高到0.57,可以采用生物化学方法处理电解后硝基苯废水。(3)以含钛矿物为催化剂,利用钛基尺寸不变阳极(DSA)类金属氧化物电极对含硝基苯类废水进行了电化学深度氧化处理,并用高效液相色谱分别对阴、阳极产物进行了分析。实验结果表明,硝基苯去除机理为：在自由基作用下,按硝基苯→硝基酚类→苯酚类一二氧化碳、水的途径降解。在30 V电压下,电解25 min后硝基苯阴、阳极降解率均可以达100%。通过对降解产物的COD分析,阳极在30 min后有机物降解彻底,可以实现污染物零排放；随着电化学催化降解时间的延长,阴极降解产物BOD5/COD逐渐增加,20 min后具有可生化降解性。(4)以含钛矿物为催化剂,用超声法对含硝基苯废水进行了降解研究,用高效液相色谱仪对降解产物进行了分析,实验结果表明：超声条件下含钛矿物可以催化降解硝基苯,当超声频率为45 kHz,高钛渣催化剂加入量为18.0 g·L-1时,140 min后硝基苯降解率达100%；在超声产生的自由基作用下,硝基苯降解产物为二氧化碳和水,没有其它副产物产生；单独超声条件下,硝基苯的降解符合一级反应速率方程,表观速率常数kUS=0.00407 min-1；超声催化条件下,硝基苯降解速率方程符合d[NB]/dt=kUS[NB]+kseckpt[NB]。硝基苯经超声处理后可生化性提高,超声频率45 kHz,处理180 min后,硝基苯溶液的BOD5/COD与硝基苯原溶液BOD5/COD相比,提高了近10倍,具有生物化学处理的可能性。(5)利用H202为氧化剂,高温密闭条件下对硝基苯废水进行了降解研究。通过正交实验,分析了氧化剂种类、硝基苯初始浓度、反应温度和反应时间对硝基苯降解率的影响。利用高效液相色谱仪分别对降解过程产物进行了分析,实验结果表明：H202在密闭高温条件下形成的自由基攻击硝基苯分子,硝基苯降解过程按硝基苯→硝基酚类→二氧化碳和水的途径进行,降解过程中产生的微量邻、间、对硝基酚类物质不会累积,符合报道的硝基苯与自由基反应的降解产物特点,而NaClO体系产生的邻苯二酚,是氧化剂氧化产物。H202热氧化硝基苯的降解反应符合一级动力学方程,反应表观速率常数K=0.0073 min-1。更多还原

【Abstract】 Nitrobenzene (NB) is a typical and environmental persistent organic pollutant (POP). Purification of wastewater contaminated with this pollutant is very difficult using general biological and chemical methods, since it is usually stable and disinfectant. In this work, concentrated titania ore, high-titania slag and titania-bearing furnace slag were used as the raw material for catalysts, aiming at an integrated utilization of resources and low-cost fabrication of semiconductor material. The removal efficiency of nitrobenzene catalyzed by titania-containing Slag under light, electricity, ultrasound thermal oxidation was investigated. The kinetics and mechanism of NB degradation under the conditions of light, electricity, ultrasound and thermal oxidation were analyzed. The conditions of reaction for nitrobenzene degradation were optimized, and BOD, COD, TOC of nitrobenzene wastewater were evaluated after the treatment.(1) Removal efficiency of nitrobenzene catalyzed by titania-containing slag under 365 nm high pressure mercury lamp,365 nm low pressure mercury lamp,254 nm low pressure mercury lamp and solar light in room was investigated. The products were also analyzed by high performance liquid chromatography (HPLC). The results showed that the effect of light source on the degradation of nitrobenzene is 365 nm high-pressure mercury lamp> 254 nm low pressure mercury lamp> 365 nm low pressure mercury lamp. However there is no degradation of nitrobenzene under solar light in room.100% of NB removal could be reached after 90 min under 365 nm high pressure mercury lamp. Total organic carbon removal rate was 78.52%. NB was ultimately oxidized to CO2 and H2O without other by-products by the action of free radicals provided by the ultrasound-catalysis. There is a by-product—m-nitrophenol produced. Titania-containing slag can remove nitrobenzene catalytically in the presence of light. The order is high-titania slag> concentrated titania ore> pangang slag> chenggang slag. Changes in acidity of the degradation rates of nitrobenzene were not significant in the range of pH from 3 to 11. Slightly acidic condition was conductive to reaction.(2) Electrochemical measurements of nitrobenzene aqueous solution under carbon paste electrode (containing 1% catalyst powder) as the working electrode was investigated. The results showed that the reaction of nitrobenzene which was reduced to aniline on the electrode was irreversible direct electrode reaction. Nitrobenzene electrode reactions were controlled by the diffusion steps. In acidic medium, the apparent activation energy of reduction of nitrobenzene to aniline is 14.11 kJ·mol-1 at room temperature. Its activation energy is lower, indicating NB reduction was easy on carbon paste electrode. In the inactive electrode system, the reaction factor of NB reduction to aniline was first-order. The observed rate constant k’ was 0.01895 min-1. BOD5/COD values increased from 0.07 to 0.57 after 40 min under experimental conditions, which made it possible that NB wastewater was treated by biodegradation(3) Removal efficiency of nitrobenzene was investigated by electrochemical advanced oxidization using dimensionally stable anode (DSA) basis Ti as electro-catalytic electrode and titania-containing slag. The products in anode and cathode were also analyzed by HPLC. The removal mechanism of nitrobenzene can be postulated from the results that nitrobenzene degradation follows the steps as nitrobenzene→p-nitrophenol→phenol→CO2 and H2O on the action of free radical.100% of NB removal could be reached after 25 min under 30 V when high-titania slag was used as catalyst. The products in anode were completely removed after 30 min on the analysis of COD value which showed no discharge of contaminants. With the extension of reaction time, the BOD5/COD value of product in cathode increased gradually and NB aqueous solution obtained biotransformation capability after 20 min.(4) Removal efficiency of nitrobenzene catalyzed by titania-containing slag under ultrasound was investigated, and the products were also analyzed by HPLC. The results showed that titania-containing slag can remove nitrobenzene catalytically in the presence of ultrasound. When 18.0 g·L-1 high-titania slag was used as catalyst, the removal efficiency of NB could reach 100%after 140 min under 45 kHz ultrasonic frequency. NB was ultimately oxidized to CO2 and H2O without other by-products by the action of free radicals provided by the ultrasound-catalysis. The reaction factor of NB degradation by ultrasound action was first-order. The observed rate constant kus was 0.00407 min-1. The corresponding reaction equation by ultrasound in the presence of high-titania slag is-d[NB]/dt=kUS[NB]+kseckpt[NB].Biotransformation increased after treatment of ultrasound. BOD5/COD value of NB wastewater treatmented 180 min under 45 kHz ultrasonic frequency increased nearly 10 times than original solution. NB aqueous solution obtained biotransformation capability.(5) Removal of nitrobenzene (NB) was investigated by using H2O2 as oxidizer and the reaction products were analyzed by HPLC. The effects of catalysts, initial concentration of NB, reaction temperature and time on NB degradation were studied by orthogonal layout experimental design. The results showed that free radical formed by H2O2 in thermal oxidized condition could attack the NB molecule, and NB degradation follows the steps as nitrobenzene→nitrophenol→carbon dioxide and water. There was no accumulation of the trace intermediate products of o-, m-, p- nitrophenol. The products were in accordance with radical characteristics of degradation products. However, in NaClO medium system, oxidation product is catechol, in accordance with oxidation product. The nitrobenzene degradation kinetics was first-order and the observed reaction rate constant k’ was 0.0073 min-1更多还原