二氧化氯的发生技术

本文对国内外ＣｌＯ２的发生技术进行了综合评述，详尽地介绍了作者自行研制的ＣｌＯ２发生技术和装置，认为我国推广应用ＣｌＯ２消毒处理饮用水的时机已经成熟。     

Model reactor for photocatalytic degradation of persistent chemicals in ponds and waste water

A laboratory scale flow-through model reactor for the degradation of persistent chemicals using titanium dioxide (TiO₂) as photocatalyst immobilized on glass beads is presented. In the test system with a volume of 18 L contaminated water is pumped to the upper part of the floating reactor and flows over the coated beads which are exposed to UV-radiation. The degradation of two dyes of different persistance was investigated. Primary degradation of methylene blue did not fit a first order kinetic due to coincident adsorption onto the photocatalyst and direct photolysis, resulting in a half-life of 6 h. A filtrate of a green algae suspension accelerated the colour removal. In contrast, reactive red 2 was degraded only by photocatalysis; neither adsorption nor direct photolysis led to a colour removal. The course of primary degradation followed a first order kinetic with a half-life of 18 h and a rate constant of 0.04 h⁻¹. Analysis of the degradation products indicated mineralization by detection of NO₂⁻ and NO₃⁻, accompanied by a decrease of pH and an increase of conductivity. A successful adaptation of the model reactor (scale 1:10) to dimensions required for surface waters and waste water treatment plants would be a costefficient and environmentally sustainable application of photocatalysis for the treatment of industrially polluted water and could be of relevance for third world contries, particularly those favoured by high solar radiation.     

植物SOD活性变化与其抗污能力的关系

研究了模拟酸雨、ＳＯ２单独与复合污染对水杉、杉木、龙柏３种抗污能力不同的植物ＳＯＤ活性、细胞汁酸度、细胞膜透性的影响。结果表明，ＳＯＤ的活性经污染后变化规律在不同植物有所不同，而这种变化与其抗污能力有关。ＳＯＤ活性升高者，其抗污能力强，反之则弱，与本底值大小无关。     

Intercomparison of reactive transport models applied to UO2 oxidative dissolution and uranium migration

Oxidative dissolution of uranium dioxide (UO₂) and the subsequent migration of uranium in a subsurface environment and an underground waste disposal have been simulated with reactive transport models. In these systems, hydrogeological and chemical processes are closely entangled and their interdependency has been analyzed in detail, notably with respect to redox reactions, kinetics of mineralogical evolution and hydrodynamic migration of species of interest.Different codes, where among CASTEM, CHEMTRAP and HYTEC, have been used as an intercomparison and verification exercise. Although the agreement between codes is satisfactory, it is shown that the discretization method of the transport equation (i.e. finite elements (FE) versus mixed-hybrid FE and finite differences) and the sequential coupling scheme may lead to systematic discrepancies.     

Acute and Chronic Toxicity of Chlorine Dioxide (ClO2) and Chlorite (ClO2ˉ) to Rainbow Trout (Oncorhynchus mykiss) (4 pp)

Goal, Scope and Background Chlorite (ClO2ˉ) is a primary decomposition product when chlorine dioxide (ClO2) is added during water treatment; therefore the toxic effects of both compounds on aquatic organisms are possible. Limited data are available concerning their toxicity to fish. The aim of this study was to investigate sensitivity of rainbow trout to acute and chronic toxicity of chlorine dioxide and chlorite, and to estimate the Maximum-Acceptable-Toxicant-Concentration (MATC) of those compounds in fish. Methods The acute and chronic toxicity of chlorine dioxide and chlorite to larval and adult rainbow trout was investigated in 96-hour to 20-day laboratory exposures evaluating the wide range spectrum of biological indices under semi-static conditions. Results and Discussion Median lethal concentration (96-hour LC50) values derived from the tests were: 2.2 mg/l for larvae; 8.3 mg/l for adult fish and 20-day LC50 for larvae was 1.6 mg/l of chlorine dioxide, respectively. Chlorite was found to be from 48 to 18 times less acutely toxic to larvae and adult fish, correspondingly. Both chemical compounds induced similar toxic effects in rainbow trout larvae during chronic tests (they affected cardio-respiratory and growth parameters), but chlorine dioxide had a higher toxic potency than chlorite. A significant decrease in the heart rate and respiration frequency of larvae was established. However, within an increase in exposure duration recovery of cardio-respiratory responses was seen to have occurred in larvae exposed to chlorite. Meanwhile, in larvae exposed to chlorine dioxide, a significant decrease in cardio-respiratory responses remained during all 20-day chronic bioassays. Chlorine dioxide also more strongly affected growth parameters of rainbow trout larvae at much lower test concentrations. Decreased rate of yolk-sack resorption occurred only in the tests with chlorine dioxide. Conclusions Maximum-Acceptable-Toxicant-Concentration (MATC) of 0.21 mg/l for chlorine dioxide and of 3.3 mg/l for chlorite to fish was derived from chronic tests based on the most sensitive parameter of rainbow trout larvae (growth rate). According to substance toxicity classification accepted for Lithuanian inland waters, chlorine dioxide and chlorite can be referred to substances of \moderate\ toxicity to fish. Recommendations and Outlook Due to its very reactive nature, chlorine dioxide is rapidly (in a few hours) reduced to chlorite, which is persistent also as a biocide but 16 times less toxic to fish, according to MATC. Therefore, it is much more likely that fish will be exposed to chlorite than to chlorine dioxide in natural waters. Presently accepted, the Maximum-Permitted-Concentration of total residual chlorine (TRC) in waste-water discharging into receiving waters is 0.6 mg/l. If this requirement will not be exceeded, it is unlikely that fish would be exposed to lethal or even to sublethal concentrations of chlorine dioxide or chlorite. Furthermore, chlorine dioxide does not generate toxic nitrogenous (chloramines) or carcinogenic organic residuals (trihalomethanes). All these properties make chlorine dioxide a more promising biocide than chlorine.     

紫外活化甲酸产二氧化碳阴离子自由基还原Cr (VI)的研究

研究高效还原技术是去除废水中Cr（VI）的有效手段,本研究提出了一种新颖有前景的基于紫外（UV）活化甲酸（HCOOH）产还原性二氧化碳阴离子自由基（CO₂^•;-）去除Cr（VI）的方法.通过对比UV、HCOOH、UV/HCOOH三种体系对Cr（VI）还原效率和电子自旋共振（EPR）对体系中自由基的检测研究了其活化原理和还原机制.结果表明UV能显著活化HCOOH产生CO₂^•-（α_H=19.08G,α_N=15.86G,g=2.0036）.此外,试验考察了主要影响因素对Cr（VI）去除效果的影响,包括初始Cr（VI）浓度、甲酸投加量、初始pH值、反应温度、有机污染物以及水中常见阴离子.结果显示当甲酸浓度为40mmol/L,Cr（VI）初始浓度为10mg/L,反应时间在60min内,UV/HCOOH体系对Cr（VI）的去除率能达到100%.在酸性条件下（pH≤3.5）能显著促进Cr（VI）的还原,且Cr（VI）去除效率随着初始HCOOH浓度和反应温度升高而增加.进一步研究表明,该体系下NO₃^-对Cr（VI）的还原有着显著的促进作用,而Cl^-、HCO₃^-和对硝基苯酚（pNP）则有抑制作用.不同温度下Cr（VI）去除率与时间关系的拟合结果表明,当反应时间t³;40min,UV/HCOOH体系去除Cr（VI）过程遵循准一级反应动力学,根据不同温度下对应的反应速率常数k,结合阿伦尼乌斯方程,计算求得准一级反应的活化能为15.9kJ/mol.     

钙法解吸并固定乙醇胺富液中CO2

针对醇胺类吸收剂富液中CO_2的解吸及后续处置所存在的不足,提出一种新型解吸方案——钙法.通过CO_2负荷试验和Ca(OH)_2投加量试验确定了该法理想处理负荷为0.84 mol·L-1,理想投加比例为C∶Ca=1∶1(摩尔比),此条件下反应15 min和30 min的解吸率达到52.17%和55.02%,这表明钙法矿化解吸乙醇胺富液中CO_2是可行的.在此基础上,进一步研究了pH、温度和搅拌强度对CO_2解吸固定效果的影响.试验结果表明,CO_2解吸率随着pH和搅拌强度的增加而增大,但当pH和搅拌强度增大到一定程度后,解吸率增长放缓甚至出现下降.较高的解吸温度尽管解吸率更大,但高温条件下无法达到矿化固定CO_2的目的.CO_2二次吸收负荷试验表明经钙法解吸后的MEA再生液具有良好的可重复使用性.     

巯基改性高岭土负载CeO2-CdS光催化降解结晶紫

为获得高效催化活性的光催化材料,实现偶氮类染料的高效降解,试验以巯基乙酸钠作为硫源和高岭土改性剂合成了巯基高岭土/CeO₂-CdS催化剂,并以降解结晶紫为模板反应,优化确定了巯基高岭土/CeO₂-CdS催化剂的制备条件.采用XRD（X射线衍射）、SEM（扫描电子显微镜）、TEM（透射电子显微镜）、FTIR（傅里叶红外光谱）和UV-Vis（紫外-可见光漫反射光谱）对催化剂进行了表征.结果表明:①催化剂是由巯基高岭土、立方相结构的CdS和萤石结构的CeO₂组成;②CdS和CeO₂的负载破坏了巯基高岭土的层状结构;③最优催化剂和巯基高岭土/CeO₂的可见光的响应范围分别为550和450 nm;④当CeO₂:CdS（摩尔比,下同）为4:6,巯基高岭土:CeO₂-CdS（质量比,下同）为1:3时,催化剂具有最优的光催化活性;⑤在50 mL结晶紫浓度为10 mg/L的溶液中,添加0.1 g最优催化剂后,采用350 W氙灯对其光照150 min时,结晶紫的降解率为95.1%;⑥最优催化剂具有良好的重复使用性能,重复使用5次时,对结晶紫的降解率为90.4%.研究显示,结晶紫降解的最终产物为CO₂和H₂O,催化剂对结晶紫的降解机理是以羟基自由基氧化为主和超氧基氧化为辅的共存氧化机理.      

ClO2杀灭拟柱孢藻过程中毒素释放行为与释放机理

试验考察了二氧化氯(ClO_2)杀灭拟柱孢藻过程中不同条件下柱孢藻毒素(CYN)随时间的释放规律,对释放量与时间数据进行曲线方程拟合,并以透射电镜观察不同反应时间拟柱孢藻细胞形态,对柱孢藻毒素的释放机理进行分析。结果表明,反应初期5 min内CYN释放率随时间延长快速提高,随后增长缓慢,30 min后趋于稳定。ClO_2投加量影响了CYN释放速率,1.0 mg/L ClO_2投加量时CYN释放率要高于0.5 mg/L和0.7 mg/L时,但在反应2 h后不同ClO_2投加量的CYN释放率趋于接近。拟柱孢藻初始浓度对CYN释放率的影响不明显。CYN释放率在酸性条件下高于中性和碱性条件。随反应温度升高,CYN释放率逐渐升高。各种反应条件下CYN释放量与反应时间的关系可以用曲线方程来表示。藻细胞形态随反应时间延长发生变化。ClO_2投加量增大,藻细胞结构的破坏程度加剧。在反应初期CYN释放是通过扩散作用而并非由细胞壁的破裂而致。     

Evaluating the e ects of granular and membrane filtrations on chlorine demand in drinking water

In this study, chlorine decay experiments were conducted for the raw water from Nakdong River that is treated by Chilseo Water Treatment Plant (CWTP) situated in Haman, Korea as well as the e uents from sand and granular activated carbon (GAC) filters of CWTP and fitted using a chlorine decay model. The model estimated the fast and slow reacting nitrogenous as well as organic/inorganic compounds that were present in the water. It was found that the chlorine demand due to fast and slow reacting (FRA and SRA) organic/inorganic substances was not reduced significantly by sand as well as GAC filters. However, the treated e uents from those filters contained FRA and SRA that are less reactive and had small reaction rate constants. For the e uents from microfiltration, ultrafiltration, and nanofiltration the chlorine demand because FRA and SRA were further reduced but the reaction rate constants were larger compared to those of sand and GAC filter e uents. This has implications in the formation of disinfection by products (DBPs). If DBPs are assumed to form due to the interactions between chlorine and SRA, then it is possible that the DBP formation potential in the e uents from membrane filtrations could be higher than that in the e uents from granular media filters.