飞灰中二英热脱附行为的研究

研究了垃圾焚烧产生的飞灰中二噁英在隔绝空气受热条件下的热脱附行为及规律.通过气相和固体残留中二噁英的含量分析,推测了二噁英在不同温度条件下可能发生的几种化学反应和物理变化,同时研究了17种有毒二噁英的热脱附效率和飞灰的最佳热脱附条件.PCDD/Fs在200℃和300℃下平均脱附率分别为96.2%和95.5%,而400℃下的平均脱附率高达99.7%.结果表明,在300℃加热条件下,飞灰中的PCDD/Fs主要发生脱氯降解反应.在400℃下,飞灰中发生大量的前体合成反应,使PCDD/Fs含量显著增加.     

医疗废物焚烧飞灰二噁英的热处理研究

比较了医疗废物焚烧飞灰在温度200～450℃,流动氮气和静态空气气氛中二噁英气固相行为变化.在流动氮气条件下,固相二噁英随温度升高逐渐增加,350℃下飞灰二噁英浓度升至最高,毒性当量浓度和总浓度分别增加了46.0%和26.0%,随后随着温度升高,二噁英含量逐渐降低,450℃条件下浓度减少至最低,分别减少了86.8%和80.5%.在静态空气下,固相二噁英随温度至250℃条件下,飞灰二噁英浓度升至最高,毒性当量浓度和总浓度分别增加了20.7%和28.7%,随着温度进一步升高,二噁英含量逐渐降低,450℃条件下浓度减至最低,分别减少了99.5%和99.5%.气相只有少量二噁英产生,仅占总产生量的0.11%～2.16%.本实验研究飞灰的最佳热处置条件为:静态空气条件下,450℃处置1 h.本研究中,分解反应在PCDDs与PCDFs的降解过程起到主要作用,而脱氯与脱附仅为次要作用.     

V2O5-WO3/TiO2催化剂与活性炭混合降解气相二噁英

基于二噁英稳定发生装置,研究在低温条件下(160℃)V2O5-WO3/Ti O2催化剂与2种活性炭(煤基活性炭及椰基活性炭)的物理混合物对气相二噁英(毒性当量质量浓度为9.80 ng·m-3)催化降解作用.结果表明,在加入活性炭后,二噁英的脱除效率及降解效率都有一定提高(20%左右).与椰基混合物相比,虽然煤基混合物对二噁英的脱除效果较弱,但其降解效果更好.调整混合物的比例会造成二噁英脱除效率及降解效率的改变,总的来说,在提高催化剂的比例后,二噁英脱除效率略有下降,但降解效率会有较为明显的提升.当反应气氛中的氧体积分数为0%时,将严重影响催化剂活性,导致绝大部分二噁英被吸附在混合物中而无法被催化氧化,随着氧体积分数的提高,二噁英的降解效率将大幅提高.为了提高二噁英的降解效率,向反应系统引入200 mg·m-3的臭氧,实验结果表明在一定条件下臭氧可以提高二噁英的催化氧化效果,但同时会与混合物中的活性炭发生反应,影响混合物的使用寿命.引入臭氧后,当煤基混合物配比为1∶1,反应温度为200℃时,二噁英的脱除及降解效率达到最高,分别达到98.0%和94.8%,尾气中的二噁英的毒性当量质量浓度仅为0.51 ng·m-3.     

医疗废物焚烧飞灰二英的热处理研究

比较了医疗废物焚烧飞灰在温度200～450℃,流动氮气和静态空气气氛中二(噁)英气固相行为变化.在流动氮气条件下,固相二(噁)英随温度升高逐渐增加,350下飞灰二(噁)英浓度升至最高,毒性当量浓度和总浓度分别增加了46.0%和26.0%,随后随着温度升高,二(噁)英含量逐渐降低,450℃条件下浓度减少至最低,分别减少了86.8%和80.5%.在静态空气下,固相二(噁)英随温度至250℃条件下,飞灰二(噁)英浓度升至最高,毒性当量浓度和总浓度分别增加了20.7%和28.7%,随着温度进一步升高,二(噁)英含量逐渐降低,450℃条件下浓度减至最低,分别减少了99.5%和99.5%.气相只有少量二(噁)英产生,仅占总产生量的0.11%～2.16%.本实验研究飞灰的最佳热处置条件为:静态空气条件下,450℃处置1 h.本研究中,分解反应在PCDDs与PCDFs的降解过程起到主要作用,而脱氯与脱附仅为次要作用.     

水洗对焚烧飞灰中氯及重金属元素的脱除研究

为了研究水洗对飞灰中氯和重金属元素的脱除影响因素,确定水洗最佳参数并分析水洗的脱除机理,对飞灰的水洗过程进行了系统的研究。结果显示:当液固比为8、水洗时间10 min、水洗温度50℃、水洗1次时,氯的去除率达93.71%以上;水洗脱氯的过程包括溶解和脱附两部分,当液固比20 mL/g时,以脱附为主;同时飞灰中的重金属在水洗过程中也有不同程度的脱除,其中Pb的脱除率和在水洗液中的浓度较大。     

生活垃圾循环流化床焚烧锅炉飞灰中二噁英热解析特性研究

实际垃圾焚烧系统中飞灰会在尾部烟道堆积并在受热后发生二噁英的再生成、热降解及向烟气解析等协同作用.本文研究了半干法脱硫塔前生活垃圾焚烧飞灰在受热过程中二噁英的质量变化及其气固相分布情况,重点研究了反应温度、含氧量及硫胺基复合阻滞剂的添加等对飞灰中二噁英热解析特性的影响.试验结果表明,250℃时飞灰析出的气相二噁英很少,而450℃时气相二噁英的比例高达99.7%;氧含量对飞灰中二噁英的热解析特性影响较大,当氧含量为6%时,气相二噁英的析出量最大,达到2.87 ng·g-1;350℃时添加硫胺基复合阻滞剂后二噁英总量明显下降,表明阻滞剂能够抑制二噁英再合成,但气相中二噁英的比例从47.69%上升到87.50%.     

生活垃圾热解气化二噁英生成指示物浓度分布及关联模型研究

生活垃圾热解气化过程中二噁英在线监测关联模型缺失.本文研究了不同反应气氛、氯源条件下生活垃圾热解气化过程中二噁英及指示物氯苯、多环芳烃的排放特性,利用SPSS软件量化二噁英与前驱物氯苯、多环芳烃之间的相关性.结果表明,由于还原性气氛的抑制,热解气化条件下二噁英毒性当量要比氧化性条件下低60倍.此外,12种氯苯中1,2,3-TrCBZ (1,2,3-trichlorobenzene)可作为城市生活垃圾热解气化烟气中二噁英含量的优选指示物,并建立了气相PCDD/Fs (Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans)与1,2,3-TrCBZ浓度的线性相关模型.16种多环芳烃中BKF（苯并荧蒽）和DbA （二苯并蒽）与二噁英总量、毒性当量的关联性一般,R2在0.7左右.本研究可为热解气化条件下二噁英在线监测关联模型的建立提供理论指导.     

布袋除尘器和活性炭滤布对烟气中二噁英类的去除效果

通过实验研究了布袋除尘器、活性炭滤布吸附器以及二者的组合对小型垃圾焚烧炉烟气中二噁英类的去除效果.在炉膛温度850℃～900℃的条件下,3种方法对烟气中二噁英类的去除率分别为39.7%、61.9%、93.4%采用布袋除尘器+活性炭滤布吸附器能够在降低运行费用的同时使二噁英类的排放符合国家标准     

水泥窑协同处置生活垃圾焚烧飞灰过程中二噁英的迁移和降解特性

为了解生活垃圾焚烧飞灰中的二噁英在水泥脱氯预处理过程中的迁移特性以及在水泥窑内的热降解特性,依托北京市琉璃河水泥有限公司的生活垃圾焚烧飞灰水泥窑协同处置示范线,开展了生活垃圾焚烧飞灰的水洗脱氯预处理和水洗后飞灰向水泥窑投加的工程试验研究.结果表明:烘干烟气中和水泥窑窑尾烟气中二噁英排放浓度低于GB 30485—2013《水泥窑协同处置固体废物污染控制标准》中所规定的标准限值(以I-TEQ计)为0.1 ng/m~3,结晶氯盐中二噁英含量(以I-TEQ计)仅为2.8 ng/kg;以每h进入水洗罐的原飞灰中所含二噁英量为100%计,经过水洗处理后,99.97%的二噁英仍留在脱氯飞灰中,仅有0.08%和0.14%的二噁英分别通过烘干废气和结晶盐排出;以每h投入水泥窑窑尾烟室的飞灰所含二噁英为100%计,仅有0.82%、0.13%和0.002%的二噁英分别随窑灰、熟料、烟气排出,飞灰中的二噁英在水泥窑内的消减率达到了99%以上,实现了较为彻底的降解.     

活性炭催化剂混合物降解气相二噁英及混合物的再生

基于二噁英稳定发生系统,研究不同温度下(160、180、200℃)两种活性炭(煤基活性炭及椰基活性炭)与V<₂O₅-WO₃/TiO₂催化剂的物理混合物对高浓度气相二噁英(本文所有质量浓度均为毒性当量质量浓度,其毒性当量质量浓度为20.46ng·m^-3)的吸附降解作用.试验结果表明,混合物可以较大幅度的提高二英的脱除效率及降解效率,其中椰基混合物表现出较好的吸附性能,而煤基活性炭表现出较好的降解性能.当反应温度为200℃,使用煤基混合替代催化剂,二噁英降解率由56.4%上升至82.0%.将含有毒性当量质量浓度为1.539ng·g^-1的二噁英混合物置于200℃下,并采用混合气体(V_N2:V_O2=9:1)进行吹扫,发现经过10h后,混合物中二噁英的毒性当量质量浓度仅为0.296ng·g^-1,最终有76.5%的二噁英得到了降解,为混合物的循环利用提供可能性.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.     

Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment

Zeolite synthesized from fly ash （ZFA） without modification is not efficient for the purification of NH4＋ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 （≥0.9 mol/L） resulted in a limited maximum phosphate immobilization capacity （PIC）. It was concluded that through a previous mild acid treatment （e.g. 0.01 mol/L of H2SO4）, ZFA can be used in the simultaneous removal of NH4＋ and P at low concentrations simulating real effluent.