【作者】 程治良；

【导师】 黄玉明；

【作者基本信息】 西南大学 ， 分析化学， 2013， 博士

【摘要】 工业废水尤其是含内分泌污染物、偶氮染料及重金属废水的处理,一直备受关注,主要原因是这些污染物即使在较低的浓度也表现出较大的环境危害和毒性风险。在各种物化处理方法中,Ti02非均相光催化是处理难降解有机污染物的一种很有前景的方法,由于该方法具有可利用太阳能的优点而受到重视;空气吹脱法在去除废水中挥发性污染物方面因具有过程简单、成本较低等优点,得到广泛应用。但是,TiO2非均相光催化存在液相中光催化剂易于团聚、失活、分离回收困难,以及由于光催化剂团聚引起的反应体系中气—液—固相间传质限制与光源传递限制等问题；空气吹脱是一个涉及气—液相间传质的废水处理过程,由于实际废水处理过程中往往存在固体物质,使得常用的填料塔等气—液反应设备中存在填料结垢和堵塞等工程问题,其处理过程效率也有待提高。因此,研究这些废水处理过程中涉及的多相反应过程的强化方法,并开发与此相适应的新型反应器,对于废水处理技术的创新具有直分重要的意义。为此,本论文开展了超声波强化纳米TiO2多相光催化；循环流化床技术强化微米级稀土掺杂Ti02多相光催化；静态超重力场强化气—液反应等污染物处理过程的研究,对强化处理过程进行了详细分析,着重在反应器的结构设计、构—效关系量化、反应器结构优化、流型分析等方面,构建了超声波和流态化技术强化TiO2多相光催化和静态超重力强化气—液反应去除污染物的新方法。主要研究内容如下：1、设计了一种新的循环超声直接强化光催化反应器,以解决悬浮浆态TiO2光催化反应体系中纳米光催化剂易于团聚及其对间质量传递和光传递的限制问题。针对悬浮浆态TiO2光催化反应体系出现的光催化剂易于团聚失活的问题,研究采用超声场强化TiO2光催化多相反应过程,来提高处理效率。实验设计了一种新的循环式超声直接强化光催化反应器,用以处理偶氮染料——甲基橙,实验研究了过程操作参数对处理效果影响。研究表明,超声和光催化过程在该反应器中实现了有效协同,产生了明显的协同效应,处理效果优于两种单独过程处理效果之和。最优操作参数为超声功率600W、TiO2光催化剂浓度3g/L、循环流速4.05×10-2m/s、气流量200ml/min。在最优条件下,处理1h甲基橙的降解率可达91.74%,降解速率常数达3.96×10-2min-1,超声与TiO2光催两个反应过程之间的协同因子高达2.26。超声光催化处理过程中,光催化起主导作用,超声主要起协同强化作用,可提高污染物的降解效率,但并不改变前者的降解变化趋势。2、以稀土Gd掺杂的微米TiO2为光催化剂,结合固体流态化思想,设计了一种光源内置式气-液-固三相循环流化床光催化反应器,研究了内分泌干扰物—双酚A在该光催化反应体系中的降解,对处理过程进行了分析评价。构建了基于颗粒型TiO2光催化剂与流态化技术相结合的光催化处理新方法,解决了光催化体系中纳米催化剂难于回收利用的问题。针对悬浮浆态TiO2光催化反应体系存在的纳米光催化剂易于团聚失活、且难以分离回收,无法用于实际废水处理等缺点。提出了使用易于沉降分离的微米级稀土Gd掺杂TiO2光催化剂,与新设计的光源内置式气-液-固三相循环流化床相结合的光催化反应体系,颗粒流态化强化光催化反应过程,提高处理效果。实验以双酚A为模型物,先优化了新反应体系的操作参数；然后在最优操作条件下,从处理效果和沉降性能上与常用的P25-TiO2反应体系进行了对比：最后采用响应曲面法对新反应体系进行了优化。研究表明：对于新的反应体系,最优操作参数为Ti02浓度为4.5g/L,表观气速为7.83×10-3m/s,表观气速为8.65×10-3m/s。与常规的P25-TiO2粉末反应体系相比,该反应体系具有更好的光催化性能和光催化剂沉降性能,实际光催化效率是后者的3倍。通过响应曲面法建立的模型,可对该反应体系处理的效果进行优化和评估。3、水力喷射—空气旋流器(WSA)中射流流型分析,为利用静态超重力强化气—液反应处理污染物提供了过程调控与操作参数优化的基础。水力喷射空气旋流器是一种利用液体射流与气体旋流耦合场和静态超重力场强化气—液反应过程的新型高效反应器。由于其内部无填料和反应介质的高速旋转剪切流动,因而可以避免实际废水处理过程中设备内部填料的结垢和堵塞问题,具有自清洁功能。为了进一步提高静态超重力场强化气—液传质效率,认识射—旋流体系气—液传质机理,为反应过程调控与操作参数优化提供基础,首先采用了直接观察法对水力喷射—空气旋流器(WSA)中的射流流型进行了系统研究,绘制出了不同进口气速下射流流型图。然后,结合化学吸收法(CO2—空气-NaOH体系)测定了不同射流流型下的有效相界面积α,并将流型和α进行关联分析,以便证实流型划分的科学性。结果表明,在低射流流速(≤4.42m/s)下,液相射流随着进口气速增大,主要存在稳态射流、变形旋线射流、破碎旋线射流、雾化旋线射流、贴壁雾化旋线射流五种流型；在高射流流速(≥6.19m/s)下,射流主要出现稳态射流、破碎旋线射流以及雾化旋线射流三种流型。有效相界面积α与流型有关,雾化旋线射流下的α值大于其他流型下对应值,但低流速下的贴壁雾化,不利于气液两相充分接触、作用,对应α值较小。α值与射流流速有一定关系,随着射流速度的增大而略有增大,且随着射流流速增大至8.84m/s以上,增大的幅度变大。4、水力喷射—空气旋流器(WSA)的喷孔分布与结构优化,为实现静态超重力强化气—液反应过程的设备设计提供了依据。超重力场常用来强化气—液传质,但目前采用的主要是动态超重力设备旋转填充床,存在稳定性差、能耗高、易结垢的缺点。本课题组开发了一种利用液体射流场和气体旋流超重力场耦合强化气—液传质的新型静态超重力设备水力喷射—空气旋流器(WSA)。为了进一步提高WSA的传质性能,本章采取理论分析与吹脱氨实验相结合的方法,对其喷孔排布方式、喷孔间距、喷孔直径进行了优化研究。提出了基于同层相邻喷孔液相射流边界层相交于WSA中心排气管表面的临界孔间距lc和反映射—旋流耦合传质特性的准数,JC的概念及其计算方法。研究表明,在吹脱氨传质性能上,WSA的射流喷孔按正方形排列优于三角形排列；喷孔间距存在一个较优取值,其值约等于1.28lc；通过数据拟合,得到了JC的经验公式为JC=2.77×10-9Re0.37ReL1.18WeL-1.05,该式可较好地预测喷孔直径对WSA脱氨传质性能的影响。喷孔直径的最佳取值应按db=l0/6.39设计计算,l0为WSA的环隙宽度。5、水力喷射—空气旋流器(WSA)用于SO2还原处理高浓度含Cr(Ⅵ)废水,建立了SO2还原法处理含Cr(Ⅵ)废水新工艺。含Cr(Ⅵ)废水常采用S02还原处理,一般采用填料塔、板式塔等设备,存在气液传质效率低、投资大、易结垢、堵塞等问题。本工作以SO2为还原剂,采用静态超重力强化气液传质设务——水力喷射空气旋流器(WSA)对含铬废水进行直接还原处理,并考察了废水pH、液相射流流速、SO2浓度、Cr(Ⅵ)浓度等因素对处理效果的影响。研究结果表明：当SO2浓度为3582m/m3时,对Cr(Ⅵ)初始浓度为1134mg/L的模拟含铬废水,循环处理6min,Cr(Ⅵ)去除率可达99.9%以上。废水初始pH为碱性比其为酸性条件下,更有利于SO2的勺吸收,提高了SO2利用率,增强了处理效率。废水射流流速对处理效果的影响较小,但SO2和Cr(Ⅵ)的浓度对处理效果有明显影响。随着SO2浓度增大,处理效率增大；Cr(Ⅵ)的初始浓度增大,处理效率降低。研究结果为建立含硫气体还原处理含Cr(Ⅵ)废水新工艺提供了依据。更多还原

【Abstract】 Treatment of industry wastewater is a concern, especially for those pollutants that can not be treated by traditional biological methods, such as endocrine disruptors, azo dyes and heavy mental. Even with low concentrations, they can bring huge environmental pollution and toxic danger. These pollutants should be dealt by the physico-chemical treatment and process, in which photocatalysis using TiO2particles and air stripping process attract extensive attention for their simple processes, low cost and no need to add any chemical reagent. However, there exists low proficiency, few studies on the equipments and other problems. In order to solve these problems, in this thesis, physico-chemical treatment and process intensification of recalcitrant pollutants of azo dye, endocine disruping chemicals, ammonia and hexavalent chromium were investigated, and the thesis could be divided into five parts of contents:I Design a new circulating ultrasound directly-intensified photocatalytic reactor to solve the problems that the nanometer photocatalyst is easily agglomerated and limited the mass transfer in the suspension slurry reaction system of photocatalysis. In this chapter an original ultrasound (US) directly intensified photocatalytic reactor was designed to find a more efficient intensification manner for the scale-up of sonophotocatalytic process. Azo dye of methyl orange (MeO) was used as model pollutant using Degussa TiO2as the photocatalyst. The sonolytic, photocatalytic and sonophotocatalytic degradation of MeO in the new reactor and the synergistic effect between sonolysis and photocatalysis were investigated. Effects of operation parameters i.e., US power. TiO2dosage, liquid circulation velocity and air flow rate on degradation efficiency were investigated and optimized. The results showed that all parameters have optimal values for the sonophotocatalytic degradation of MeO, and the optimum conditions for the new process are US power600W, TiO2dosage3g/L, liquid circulation velocity4.05×10-2m/s and air flow rate0.2L/min. Under the optimum conditions,91.52%MeO had been degraded within1h, and the combination of sonolysis and TiO2photocatalysis exhibited an obvious synergetic effect.2The suspended slurry photocatalytic systems using TiO2nanoparticles can maximize the efficiency of photon utilization, oxidation rates and reactor throughput. However, the nanophotocatalysts easily agglomerate in slurry system, reducing the efficiency of photocatalytic process. It also exist separation problem of nanophotocatalysts using in the slurry system. In order to solve the problem, a new gas-liquid-solid circulating fluidized bed photocatalytic reactor (GLSCFBPR) with internally placed multi-layered UV lamps was developed and micrometer Gd-TiO2particles was chosen as the photocatalyst to intensify the treatment process. Hazardous substance bisphenol A (BPA) was chosen as the model pollutant to investigate the performance of this new photocatalytic system. The results showed that the photocatalytic degradation efficiency of the micrometer Gd-TiO2particles was similar to that of the nanometer P-25particles at their respective optimum dosage but the former could be easily separated out by gravity. After investigating the effects of process parameters on the photocatalytic BPA degradation, the response surface method (RSM) was further used for process optimization. The interactions among process parameters, i.e. TiO2concentration, superficial gas velocity and superficial liquid velocity were discovered and a related analysis was carried out to explore the underlying mechanism. A quadratic mathematic model was established and performed satisfactorily when used for prediction. The optimum conditions for this new process were as follows:TiO2concentration4.5g/L, superficial gas velocity7.83×10-3m/s and superficial liquid velocity8.65×10-3m/s. Under the optimum conditions,91.74%MeO had been degraded within1h, and the apparent degradation rate constant is3.96×10-2min-1. The synergy between photocatalysis and sonolysis is as high as2.26.3、Water-sparged aerocyclone (WSA) is new gas-liquid mass transfer equipment developed by our research group using of supergravity field of sparged air. In order to investigate the mechanism of the jet-sparged system of the WSA and improve its mass transfer performance, jet flow pattern and interfacial area (a) of the WSA were determined by directly observed method and the chemical reaction method with CO2-NaOH solution system. Then the transition of jet flow pattern and the a were correlated. The results show that jet flow pattern is mainly affected by jet velocity and air inlet velocity. There exists steady state je;, deformed spiral jet, broken spiral jet, atomized spiral jet and total atomized spiral jet in the WSA when the jet velocity is lower than4.42ni/s. Besides, when the jet velocity is higher than6.19m/s there exists only deformed spiral jet, broken spiral jet and atomized spiral jet. The a is related to jet flow pattern, and a is higher in atomized spiral jet than in the other jets. Moreover, the value of a increases with liquid jet velocity because of the gas-liquid intense interaction in WSA.4、In order to improve its mass transfer performance and establish design principles, spray hole distribution and jet hole diameter of the WSA was optimized by means of theoretic analysis and experimental method. A new concept, critical distance of spray holes,lc, and its calculation formula were put forward. A new dimensionless number, Jc, characterizing the mass transfer performance in the liquid jet-gas cyclone coupling field, was suggested. The results showed that the WSA with square arrangement of spray holes exhibited higher mass transfer efficiency than that with triangle arrangement of spray holes in air stripping of ammonia. The distance between adjacent spray holes of the WSA had obvious effect on volumetric mass transfer coefficient, the optimal distance was about1.28lc and the perforation area was about78%of the central tube height in the WSA. The mass transfer efficiency of the WSA increased with increasing jet hole diameter under a certain liquid jet velocity in air stripping of ammonia. However, excessive jet hole diameter will consume more energy for the reeireillation of wastewater. The optimum jet hole diameter could be calculated asdh=lo/6.39, herelo is the annular with of the WSA. To predict the effects of jet hole diameter on mass transfer characteristics in WSA, empirical formula for correlating the experimental data was developed, as Jc=2.77×10-9Reg0.37ReL1.18(?)eL-1.05.These results could be used as a guide for the design of WSA with good mass transfer performance.5、The removal of hexavalent chromium (Cr(Ⅵ)) from wastewater by sulfur dioxide(SO2) reduction was conducted in the water-sparged aerocyclone (WSA) reactor, and a satisfactory result was obtained. When chromium containing wastewater of1134mg/L was treated for6min with a gas containing SO2of3582mg/m3, more than99.9%Cr (Ⅵ) was removed. Alkaline Cr (Ⅵ) containing wastewater is beneficial to the absorption of SO2, increasing the efficiency of Cr (Ⅵ) reduction. Initial concentrations of SO2and Cr(Ⅵ) have significant influence on the efficiency of Cr (Ⅵ) removal, but wastewater jet velocity has less effects. Increasing SO2concentration increased Cr (VI) removal efficiency, whereas increasing Cr (Ⅵ) concentration decreased the treatment efficiency. Compared with the SO2reduction process conducted in some traditional gas-liquid reactors like packed towers, this SO2reduction process conducted in the WSA has obvious advantages such as no need for adjusting pH of wastewater to2～3before SO2reduction, easy operation and no Cr (OH)3scale deposited in reactor. So the investigation could provide a new sulfur dioxide reduction process for Cr (Ⅵ) containing wastewater using SO2containing gas.更多还原