【作者】 李楠；

【导师】 王鹏；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 博士

【摘要】 二甲亚砜(DMSO)作为溶剂或中间体在医药、化工、电子等领域应用广泛,但二甲亚砜生产废水中残留的二甲亚砜在自然水体中易产生硫化氢、硫醚等有毒物质,而且难以用生物法处理;另一方面,二甲亚砜生产中氧化工艺段产生的高浓度亚硝酸盐废水毒性很强,采用生物法或常规物化方法均难以有效处理。针对二甲亚砜生产废水处理中存在的以上技术难题,本文将微波技术分别与催化湿式氧化工艺、Fenton氧化工艺和化学还原工艺相结合,利用微波高效、快速等技术特点,建立了三种微波强化水处理工艺并用于对二甲亚砜和亚硝酸盐的处理,均取得理想效果。首先以硝酸活化后的颗粒活性炭(GAC)作为载体,以铜作为活性组分,稀土元素铈作为助剂组分,采用分层浸渍焙烧法制备了CuOx-CeOy/GAC催化剂。结构分析结果表明,活性组分铜在催化剂表面主要是以Cu2O和单质的形式存在,变价的过渡金属元素和单质对微波能具有更好的吸收作用,可以强化催化湿式氧化反应。在催化剂表面,铈以CeO2、Ce2O3和CeO的形态共存,而且铈的加入无论在体相中和表面上均提高了铜元素的含量,其中铈在催化剂中的含量为0.56%,铜的含量为10.81%,助剂铈的加入还明显提高了催化剂表面活性组分的分散性,使晶粒粒径减小,增加了催化剂表面的活性点位,并使催化剂表面活性组分与载体结合的程度增强,使其稳定性和使用寿命得到显著提高。采用制备的CuOx-CeOy/GAC催化剂,建立了微波强化催化湿式氧化工艺对二甲亚砜进行处理。该工艺用于处理初始浓度为1000mg/L的二甲亚砜配水,可在pH值3~9范围内,反应3min后达到85%以上的二甲亚砜去除率,TOC去除率为24.4%。对微波强化催化湿式氧化处理二甲亚砜的作用机制进行了探索研究,采用分子荧光光谱法测定了反应体系中羟基自由基(·OH)的生成量,通过对比证明CuOx-CeOy/GAC催化剂的加入对对体系中·OH自由基的生成量有明显促进作用;微波辐照、催化剂和氧化剂三者间存在协同效应,可大大提高H2O2氧化体系内·OH的生成量,从而增强对废水中二甲亚砜的去除效率。研究开发了微波强化Fenton氧化处理二甲亚砜工艺。针对100mL初始浓度为1000mg/L的二甲亚砜配水,获得最佳工艺参数为:H2O2投加浓度450mg/L,H2O2与Fe2+摩尔比2,在微波功率100W条件下辐照5min,pH值在2~7范围时,对二甲亚砜的去除率可达95%以上,10min内TOC去除率为46.3%。基于静态实验结果,设计了微波强化Fenton氧化动态工艺系统,实现了含二甲亚砜废水在连续流条件下的高效处理。对于2L初始浓度为1000mg/L的二甲亚砜配水,最佳处理条件为:H2O2投加浓度为350~400mg/L,循环系统温度50~60℃、循环完成时间为8~10min和曝气速率5~20L/h,二甲亚砜的去除率可达99%以上。表观动力学研究结果证明,微波的“非热效应”使其对Fenton氧化体系的强化作用要明显优于传统水浴加热方式。根据二甲亚砜主要降解产物的浓度变化和TOC测定结果,在相同Fenton试剂投加量条件下,相比于传统常温搅拌条件下的Fenton氧化工艺,微波强化Fenton氧化工艺不仅可以大大缩短二甲亚砜的降解反应时间,而且对其中难降解的中间产物具有更高的氧化效率,从而获得更高的矿化度。针对二甲亚砜生产中氧化工艺段产生的高浓度亚硝酸盐废水,本文采用氨基磺酸作为还原药剂,建立了微波强化化学还原处理工艺。设计了微波强化化学还原连续流工艺系统,针对实际废水进行工程调试,在最佳工艺参数条件下亚硝酸盐去除率可达90%以上。研究表明,微波强化化学还原连续流工艺可节省药剂25%,系统水力停留时间由3h缩短至0.5h,吨水处理成本可节省近45%。原废水经处理后,绝大部分亚硝酸盐被还原生成无毒无害的N2而得到去除,同时其它反应产物均为一些无毒的无机化合物,废水中亚硝酸盐经处理控制在较低浓度后,毒性大大降低,可进一步采用生物法进行脱氮处理。本文将微波技术分别与催化湿式氧化工艺、Fenton氧化工艺和化学还原工艺相结合,对传统的高级氧化工艺和化学还原技术进行了改进,建立了三种新型的微波强化水处理工艺。与传统工艺相比,微波强化水处理工艺具有处理效率高,废水pH值适用范围宽、反应速度快、出水温度适宜,设备占地面积少,工艺操作简单等优点,易于实现自动化管理和工业化推广。本文的研究结果不仅为二甲亚砜生产废水中残存的二甲亚砜和高浓度亚硝酸盐的处理提供了有效的解决途径,而且为其它含有难降解有机物或高浓度亚硝酸盐的废水开辟了一类具有广阔应用潜力的新型水处理技术。更多还原

【Abstract】 Dimethyl sulphoxide (DMSO) is an organic solvent or intermediate, which has been widely used in the manufacture of products such as acridine, electronics, chemical industry and etc.. However, the residual DMSO in wastewaster of DMSO production will produce volatile and noxious compounds in natural water body, such as (CH3)2S or hydrogen sulfide (H2S). Furthermore the biological treatment of wastewater containing DMSO is known to be difficult. On the other hand, the effluents of oxidation section in DMSO production process contain high-concentration nitrite, which can’t be effectively removed by biological and physicochemical processes. To resolve the above technical problems with the treatment of wastewater in DMSO production process, catatlytic wet oxidation process, Fenton process and chemical reduction process were employed to combine with microwave technology. Based on the advantage of high efficiency and quickness under microwave irradiation, three efficient microwave enhanced process on wastewater treatment were established to treat with DMSO and nitrite. As a result, optimal removals were achieved after the treatment of the above microwave enhanced processes.In the first part of the paper, CuOx-CeOy/GAC catalyst was prepared by using impregnation-deposition method, in which GAC activated by HNO3 was used as carrier, Cu was used as activated composition and Ce was used as assistant composition. According to the results of structure analysis, Cu element existed in the form of Cu (elementary substance) and Cu2O and Ce element existed in the form of CeO2, Ce2O3 and CeO on the surface of CuOx-CeOy/GAC catalyst. It is believed transition metal with different valent states could adsorb more microwave energy, that would facilitate the catatlytic wet oxidation process. By the addition of Ce, the loading percentage of Cu increased both on the surface and in the catalyst. The loading percentage of Cu was 10.81% of the catalyst while Ce was 0.56%. In light of the assistant composition Ce, better dispersity and smaller size of Cu and Cu2O crystals could be achieved, that intensified the interaction between actived composition and carrier, increased the activated sites and enhanced the stability and useful life of catalyst. Microwave enhanced catatlytic wet oxidation process was established with the prepared CuOx-CeOy/GAC catalyst. Under the optimal process conditions, 100mL synthetic wastewater containing 1000mg/L DMSO was treated in the process and over 85% of DMSO and 24.4% of total organic carbon (TOC) had be successfully removed within 3min and pH range 3~9.The oxidation mechanism of microwave enhanced catatlytic wet oxidation process was also studied in the paper. The fluorescence technology was employed to measure the generation of hydroxyl radicals (·OH) in different processes and the compared results demonstrated the use of CuOx-CeOy/GAC catalyst played a key role in the the generation of hydroxyl radicals. The generation of·OH in microwave enhanced catatlytic wet oxidation process was much more than in other processes, which indicated synergistic effect existed among microwave irradiation, catalyst and H2O2. As a result, the removal efficiency of DMSO was obviously enhanced.Microwave enhanced Fenton process for DMSO treatment was also established in this paper. Under optimal conditions of [H2O2]0=450mg/L, H2O2/Fe2+ molar ratio=2, microwave power=100W, irradiation time=5min and pH=2~7, 100mL synthetic wastewater containing 1000mg/L DMSO was treated when over 95% of DMSO and 46.3% of TOC had be successfully removed. Based on the results of batch experiments, dynamic system for practical utility was devised, which realized the efficient treatment of DMSO-containing wastewater under continuous flow. The optimized operating parameters for dynamic system were [H2O2]0=400mg/L, system temperature=60℃, circulating finished time=10min and air flow rate=20L/h, which had achieved DMSO removal of 99.1%Obvious kinetic experiments were conducted to study the differences between microwave enhanced Fenton process and conventional heating assisted Fenton process. Compared with heating assisted Fenton process at equal temperature, enhanced DMSO removal in microwave enhanced Fenton process might be ascribed to the non-thermal effect under microwave irradiation. According to results of major degradation intermediates variation and TOC removal, microwave enhanced Fenton process couldn’t only shorten the degradation time for DMSO but also achieve much more removal of major degradation intermediates and TOC compared with Fenton process stirring at ambient temperature.In the final part of the paper, using sulfaminic acid as reductive chemical, microwave enhanced chemical reduction process was established to treat the practical nitrite-containing wastewater of high-concentration in DMSO production process. Based on the results of batch experiments, microwave enhanced chemical reduction continuous-flow process for practical utility was devised and achieved over 90% nitrite removal under optimal operating conditions. Compared with chemical reduction continuous-flow process without microwave irradiation, microwave enhanced chemical reduction continuous-flow process could save 25% sulfaminic acid, shorten the hydraulic retention time (HRT) from 3h to 0.5h, and save 45% cost for the treatment of every 1m3 wastewater. After treatment by microwave enhanced chemical reduction continuous-flow process, most nitrite in wastewater was converted into nitrogen gas and other reaction products were some innocuous inorganic compound. The concentration of nitrite was falling to a low level, which made it much less nocuous and suitable for further biological denitrification.In this paper, catatlytic wet oxidation process, Fenton process and chemical reduction process were combined with microwave technology to enhance the treating efficiency, and thus three new microwave enhanced processes were established for the treatment of DMSO or nitrite wastewater. The microwave enhanced processes for wastewater treatment take advantages in high treating efficiency, wide operational pH, quick reaction rate and proper effluent temperature. Furthermore the microwave enhanced processes need less occupation of land, operate easily, and is in favor of industrial popularity. The research results in this paper could not only provide a valid solution for DMSO and nitrite wastewater treatment in DMSO production process but extend series of new promising processes for the treatment of refractory and high-concentration nitrite wastewater in wide fields.更多还原