商用V/W/Ti系脱硝催化剂表面SO3生成的反应机理

基于燃煤烟气SO₃生成与排放给电厂运行及大气环境带来的严重影响,研究了一种在役典型商用蜂窝型V/W/Ti系脱硝催化剂表面的SO₃生成反应动力学及反应机理.结果表明,反应温度与SO₂浓度是影响催化剂表面SO₃生成的关键因素.在SO₂浓度为400×10^-6时,当反应温度从300℃升至360℃,SO₂-SO₃转化率从0.2%提高至0.65%,温度达到400℃后,催化剂表面V₂O₅活性增加更为显著,SO₂-SO₃转化率从0.65%增2.3%,SO₃生成反应的表观速率常数增加近3倍.SO₃在催化剂表面的生成路径为：SO₂与V⁵⁺-OH反应生成中间产物VOSO₄与HSO₄^-,随后进一步反应生成SO₃.SO₂主要通过其在催化剂表面的吸附、转化过程影响SO₃的生成,其本征动力学反应级数为0.52.O₂的本征动力学反应级数为0,SO₃生成反应可以在无O₂条件下进行,O₂存在会促进反应进行,但不会改变反应路径.     

Enhanced activation of peroxydisulfate by strontium modified BiFeO3perovskite for ciprofloxacin degradation

A series of Sr-doped BiFeO₃ perovskites (Bi_1-xSr_xFeO₃, BSFO) fabricated via sol-gel method was applied as peroxydisulfate (PDS) activator for ciprofloxacin (CIP) degradation. Various technologies were used to characterize the morphology and physicochemical features of prepared BSFO samples and the results indicated that Sr was successfully inserted into the perovskites lattice. The catalytic performance of BiFeO₃ was significantly boosted by strontium doping. Specifically, Bi_0.9Sr_0.1FeO₃ (0.1BSFO) exhibited the highest catalytic performance for PDS activation to remove CIP, where 95% of CIP (10 mg/L) could be degraded with the addition of 1 g/L 0.1BSFO and 1 mmol/L PDS within 60 min. Moreover, 0.1BSFO displayed high reusability and stability with lower metal leaching. Weak acidic condition was preferred to neutral and alkaline conditions in 0.1BSFO/PDS system. The boosted catalytic performance can be interpreted as the lower oxidation state of Fe and the existence of affluent oxygen vacancies generated by Sr doping, that induced the formation of singlet oxygen (¹O₂) which was confirmed as the dominant reactive species by radical scavenging studies and electron spin resonance (ESR) tests. The catalytic oxidation mechanism related to major ¹O₂ and minor free radicals was proposed. Current study opens a new avenue to develop effective A-site modified perovskite and expands their application for PDS activation in wastewater remediation.     

Review on heterogeneous oxidation and adsorption for arsenic removal from drinking water

The long term exposure of arsenic via drinking water has resulted in wide occurrence of arsenisim globally, and the oxidation of the non-ionic arsenite (As(III)) to negatively-charged arsenate (As(V)) is of crucial importance for the promising removal of arsenic. The chemical oxidants of ozone, chlorine, chlorine dioxide, and potassium permanganate may achieve this goal; however, their application in developing countries is sometimes restricted by the complicate operation and high cost. This review paper focuses on the heterogeneous oxidation of As(III) by solid oxidants such as manganese oxide, and the adsorption of As(V) accordingly. Manganese oxide may be prepared by both chemical and biological methods to achieve good oxidation performance towards As(III). Additionally, manganese oxide may be combined with other metal oxides, e.g., iron oxide, to improve the adsorption capability towards As(V). Furthermore, manganese oxide may be coated onto porous materials of metal organic frameworks to develop novel adsorbents for arsenic removal. To achieve the application in engineering works, the adsorbents granulation may be achieved by drying and calcination, agglomeration, and the active components may also be in situ coated onto the porous materials to maintain the oxidation and adsorption activities as much as possible. The novel adsorbents with heterogeneous oxidation and adsorption capability may be carefully designed for the removal of arsenic in household purifiers, community-level decentralized small systems, and the large-scale drinking water treatment plants (DWTPs). This review provides insight into the fundamental studies on novel adsorbents, the development of innovative technologies, and the demonstration engineering works involved in the heterogeneous oxidation and adsorption, and may be practically valuable for the arsenic pollution control globally.     

重铬酸钾法测定化学需氧量的实验条件优化

以降低成本、减少二次污染、提供多元化实验条件为主要出发点,开展GB 11914-89中氯离子掩蔽剂加入量和催化剂种类等优化实验研究。结果表明:采用按比例加入的方式可以降低硫酸汞使用量,m[HgSO4]:m[Cl-]=10∶1即可达到有效掩蔽效果;在标准样品、地表水和一般废水的COD测定中,硫酸镍、硫酸铝钾和磷酸二氢锰作为硫酸银的替代物具有一定的可行性,建议最低加入量为4g/L。     

燃煤机组SCR脱硝催化剂的研究进展

选择性催化还原(SCR)是目前控制氮氧化物排放的主要技术。本文介绍了锅炉炉后脱硝系统的布置位置及工艺条件、已经工业化的氨选择性高温还原钒催化剂的特点,以及近年来低温脱硝催化剂的研究现状。指出我国脱硝催化剂应提高还原剂的选择性,开发新型低温催化剂应重点考察烟气中的水、二氧化硫及硫酸氢铵等对催化剂的影响。     

共沉淀法制备铜系催化剂及其稳定性的研究

主要介绍了利用共沉淀方法制备铜系催化剂,并考察了制备过程中各个工艺参数对铜系催化剂稳定性的影响。通过优化催化剂的设计和制备方法,可有效地改善Cu2+的溶出问题,使该类催化剂具有广阔的应用前景。     

Pyrolysis of low-density polyethylene using synthetic catalysts produced from fly ash

Catalytic pyrolysis of low-density polyethylene (LDPE) was investigated using various fly ash-derived silica–alumina catalysts (FSAs). FSAs were prepared by a simple activation method that basically includes NaOH treatment of fly ash by a fusion method, followed by an aging process. A series of LDPE pyrolysis experiments was conducted and the catalytic performance of FSAs was assessed in terms of the degradation temperature and the simulated boiling point distribution of the liquid products. The effects of synthesis conditions such as NaOH/fly ash weight ratio and aging time were examined by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET) surface area analyzer, and scanning electron microscope to clarify the controlling factors affecting the catalytic activity. To obtain catalyst with high activity, it is necessary to produce sufficient silica and alumina species that can be easily co-precipitated into solid acid catalyst by destruction of the fly ash structure and to optimize the activation time for catalyst synthesis to prevent the transformation into inactive phases. The catalytic performance of FSA obtained from optimal conditions was equivalent to that of commercial catalysts, demonstrating the effectiveness of the catalyst.     

均相/异相催化剂光降解垃圾渗滤液效果的研究

垃圾渗滤液是一种复杂有毒的、生化降解性差的高浓度有机废水,高级氧化技术具有氧化能力强和无二次污染等特点,被认为是处理难降解有机污染物最有应用前景的方法.本研究在500 W汞灯、25℃、2.5 h反应条件下,对比了TiO_2、K2S2O_8、K2S2O_8/Fe2+、施氏矿物、施氏矿物/H2O_2、Fe2+/H2O_26种催化剂组合光化学处理垃圾渗滤液的效果.结果表明,施氏矿物/H2O_2和Fe2+/H2O_2光催化降解垃圾渗滤液中有机污染物的效果优于其它催化剂组合,渗滤液中CO_D去除率分别为41.6%和46.5%,TO_C去除率分别为76.0%和78.1%.然而,Fe2+/H2O_2组合在光催化处理垃圾渗滤液后会产生大量难以沉降的Fe(O_H)3絮状物,且渗滤液色度明显增加,由初始的40倍上升到175倍.而施氏矿物/H2O_2组合则避免了上述问题,色度去除率达100%,被认为是一种具有应用前景的光化学降解垃圾渗滤液的催化剂组合.     

我国电石法生产聚氯乙烯行业汞排放清单

提出了我国电石法聚氯乙烯(PVC)生产全生命周期汞排放清单的计算方法。采用低汞触媒有盐酸脱吸工艺、高汞触媒有盐酸脱吸工艺、高汞触媒无盐酸脱吸工艺的汞输入因子分别为0.045 g/kt、0.091 g/kt和0.122 g/kt,回收产品的汞输出分布因子分别为95.37%、81.97%和97.18%。估算得到:2010年我国电石法PVC生产汞输入量792.8~814.8 t;回收的产品汞705.9~724.4 t,通过大气无组织排放、管道残留以及其他未知途径汞排放79.6~82.8 t;废水汞排放1.3 t;固体废物汞排放3.6~3.7 t;废酸汞排放2.5~2.6 t。回收的产品汞是汞输出的主要途径。     

MTO废催化剂SAPO-34的再生

采用干凝胶转化法对甲醇制烯烃(MTO)废催化剂SAPO-34进行再生,将SAPO-34分子筛晶化所需的硅、铝、磷原料同时作为黏结剂使用,经干凝胶转化制备出再生催化剂,并对催化剂进行了表征及MTO反应活性评价。表征结果显示,再生催化剂的晶体结构、微观形貌、粒径分布、孔结构、耐磨性及酸中心均得到了恢复与改善,磨损指数可达0.35%/h。实验结果表明:在催化剂加入量为1.0 g、进气中甲醇质量分数为95%、甲醇质量空速为3 h-1、反应温度为450℃、反应压力为常压的条件下,再生催化剂的甲醇转化率接近100%,双烯(乙烯和丙烯)选择性较废催化剂提高了约3百分点,可达87%以上;同时,再生催化剂的寿命也较废催化剂有了明显改善。