Soft and sour: The challenge of setting environmental quality standards for bioavailable metal concentration in Fennoscandinavian freshwaters

The European Union Water Framework Directive (WFD) requires member states to ensure that all inland and coastal waters achieve ‘good’ water quality status. To this end, the WFD has set environmental quality standards (EQS) or Water quality criteria (WQC) for priority pollutants that include the four metals Cd, Ni, Pb and Hg. Many states have also chosen to set EQS for Cu and Zn. The use of bioavailability models to set EQS, paves the way for accepting higher local metal concentrations in waters where metal bioavailability is deemed low. The Biotic Ligand Model (BLM) concept has been proposed as a tool for estimating metal bioavailability and for calculating local EQS in the EU guidance document. The BLM estimates metal bioavailability based on the dissolved metal concentration and key ancillary water chemistry parameters (acidity, hardness and organic carbon content). The BLMs developed so far, have only been validated for water chemistry input parameters typical of Central Europe. However, the pH, alkalinity and dissolved organic carbon levels of a significant fraction of Fennoscandinavian (Finland, Norway and Sweden) freshwaters are outside the calibration range of currently available BLMs. The levels of Ca²⁺, alkalinity and pH in 75%, 29% and 22%, respectively, of the ca. 2500 Fennoscandinavian freshwater bodies investigated in this survey were outside the calibration range of tested BLMs. Moreover, a comparison of the ability of the tested BLMs to predict the acute and chronic copper toxicity to Daphnia magna and Rainbow trout indicated that the BLMs should be used with caution outside their current validation range. We conclude that more work is needed to extend the application of BLMs in the practical risk assessment to encompass a broader range of European freshwater bodies.     

Fe-Mn/AC催化湿式过氧化氢氧化间甲酚

采用等体积浸渍法制备了一种新型Fe-Mn/AC催化剂,应用于催化湿式过氧化氢氧化(CWPO)间甲酚废水.通过SEM和XRF表征了其表面形态结构和元素组成,通过穆斯堡尔谱分析了催化剂中铁离子的存在形态,结果表明,新型Fe-Mn/AC催化剂中的铁以二价铁、三价铁以及四氧化三铁的形式存在.通过正交实验考察了CWPO降解间甲酚的影响因素,结果表明,各因素对间甲酚转化率影响的大小顺序依次为:底物初始p H值反应温度反应时间催化剂投加量.通过正交实验得到CWPO降解间甲酚的最佳反应条件.当间甲酚浓度为100 mg·L-1、反应温度为40℃、反应时间为40 min、催化剂投加量为0.6 g·L-1及底物初始p H值为3时,间甲酚转化率为99.8%,TOC去除率为28.3%.气相色谱/质谱联用没有检测到中间产物,气相色谱检测到CWPO降解间甲酚中间产物主要为乙酸和丙酸.     

Fe/Cu催化还原降解饮用水中溴氯乙腈的性能研究

为了降低饮用水在氯消毒过程中产生的消毒副产物(DBPs)溴氯乙腈(BCAN)对人体带来的健康危害,采用Fe/Cu催化还原的方法降解饮用水中低浓度的BCAN,考察了BCAN的降解效果和其影响因素,探讨了其降解机制及动力学规律.结果表明,Fe/Cu具有更强的还原降解BCAN的能力,与零价铁相比,Fe/Cu(质量比为10∶1)的降解效率是其1.5倍.随着Fe/Cu投加量的增加,BCAN的去除率有明显的提高,对于初始浓度为20μg·L-1的BCAN溶液,当Fe/Cu(质量比为10∶1)投加量由5g·L-1增加到10 g·L-1,反应150 min后,去除率由51.1%增加到89.5%.BCAN降解效率随着温度的升高逐渐提高,BCAN初始浓度的变化对Fe/Cu去除BCAN的去除效果影响不大,Fe/Cu降解BCAN符合一级反应动力学规律.     

不同硅铝比Fe-ZSM-5催化剂对氧化亚氮催化分解性能的研究

以不同硅铝比的H-ZSM-5分子筛为载体,采用离子交换法和化学气相沉积法制备Fe-ZSM-5催化剂,并用XRD、BET、TEM、UV-vis和NH3-TPD等表征手段对催化剂进行分析,研究催化剂中铁的存在状态.结果表明,分子筛的硅铝比影响铁在分子筛中的分布形态,化学气相沉积法和热离子交换法制得硅铝比为25的Fe-ZSM-5-25分子筛催化剂上均匀地分布着粒径为8 nm左右的纳米氧化铁颗粒,并且Fe-ZSM-5-25分子筛催化剂比Fe-ZSM-5-300更容易形成Fe3+x O y团簇.制得的Fe-ZSM-5分子筛催化剂催化分解氧化亚氮(N2O),结果表明,相同的制备方法,硅铝比小的Fe-ZSM-5-25催化剂对N2O分解活性更好;相同硅铝比的Fe-ZSM-5催化剂,采用化学气相沉积法制得的对N2O分解活性最好.另外,O2的存在对Fe-ZSM-5上N2O催化分解活性有抑制作用,而NO对N2O催化分解活性展示了一定的正效应.最后,经过100 h的连续反应,Fe-ZSM-5催化剂依然能够保持催化活性.     

CuO(-CeO2)/Al2O3催化剂对萘催化氧化性能研究

采用浸渍法制备了CuO/Al2O3、CeO2/Al2O3和CuO-CeO2/Al2O3这3种催化剂,通过氮吸附、SEM、XRD等手段对催化剂的结构及组成进行了表征,利用固定床反应装置考察了活性组分、气体流量、催化反应温度对萘催化氧化性能的影响.结果表明,18%CeO2/Al2O3的萘催化活性较低,18%CuO/Al2O3和9%CuO-9%CeO2/Al2O3的活性较高,两者在300℃时对萘的去除率分别达到91%和89%;CuO-CeO2/Al2O3催化剂具有比CuO/Al2O3更好的低温活性;气流量的变化对两种催化剂性能的影响不大.     

UV/O_3/Fe~(2+)处理垃圾渗滤液膜滤浓缩液实验研究

采用UV/O3/Fe2+工艺去除垃圾渗滤液膜滤浓缩液混凝出水中的COD,考察O3加入量、初始溶液p H、催化剂投加量、紫外光强度、反应时间等因素对废水处理效果的影响,确定适宜的工艺条件。实验结果表明,在O3氧化体系中UV和催化剂Fe2+的引入有利于浓缩液中有机物的降解。在臭氧加入量为1.3 g/h·L,Fe2+的投加量为80 mg/L,p H为3.0,紫外光强度为36W,反应时间为60 min的条件下,UV/O3/Fe2+体系对废水中COD的去除率可达79.96%,比单独的O3体系、UV/O3体系、O3/Fe2+体系分别提高44.43%、35.9%、18.75%。     

催化氧化技术在亚盐氧化中的应用

介绍了氨酸法脱硫工艺中传统的酸法分解亚硫酸铵-亚硫酸氢铵技术和目前国内较前沿的催化氧化亚硫酸铵-亚硫酸氢铵技术。分析了催化氧化过程中影响氧化率的主要因素及该技术实际应用效果。两种技术的比较显示催化氧化技术具有工艺流程简单,自动化程度高,氧化率高,处理成本低,氧化后硫铵液可直接回收利用等优点。     

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths

Binary oxide systems (CuCr₂O₄, CuCo₂O₄), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al₂O₃), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O₂, NO_x, H₂O, CO₂) and O₃ as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO₂. Oxidants used can be arranged with reference to decreasing their activity in a following series: O₃ ? NO₂ > H₂O > NO > O₂ > CO₂. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O₃ occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the “cold start” problem.     

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths

Binary oxide systems(Cu Cr2O4, Cu Co2O4), deposited onto cordierite monoliths of honeycomb structure with a second support(finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine’s gas exhausts(O2, NOx, H2 O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3 NO2> H2 O > NO > O2> CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively(in the presence of copper chromite based catalyst) even at closing to ambient temperatures.Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem.     

混凝/催化氧化/微电解三元组合技术处理油田压裂废液

油田压裂废液成分复杂、粘度高、COD高且难降解,对环境造成较大污染。提出了化学混凝/催化氧化/微电解三元组合技术处理压裂废液的新方法,确定了各步骤的最佳工艺条件。结果表明,压裂废液经化学混凝/催化氧化/微电解三元组合技术处理后,粘度降至1.5 m Pa·s,COD去除率98%,COD150 mg/L,达到国家污水排放2级标准。各单元过程形成的泥饼浸出液分析结果符合GB 18599—2001《一般工业固体废物贮存、处置场污染控制标准》第一类技术要求。