Physical and chemical regeneration of zeolitic adsorbents for dye removal in wastewater treatment

Natural zeolite and synthetic zeolite, MCM-22, were employed as effective adsorbents for a basic dye, methylene blue, removal from wastewater. Two methods, Fenton oxidation and high temperature combustion, have been used for regeneration of used materials. It is found that MCM-22 exhibits equilibrium adsorption at 1.7 x 10(-4) mol g(-1), much higher than the adsorption of natural zeolite (5 x 10(-5) mol g(-1)) at initial dye concentration of 2.7 x 10(-5)M and 30 degrees C. Solution pH will affect the adsorption behaviour of MCM-22. Higher solution pH results in higher adsorption capacity. The regenerated adsorbents show different capacity depending on regeneration technique. Physical regeneration by high temperature combustion will be better than chemical regeneration using Fenton oxidation in producing effective adsorbents. Regeneration of MCM-22 by high temperature treatment can make the adsorbent exhibit comparable or superior adsorption capacity as compared to the fresh sample depending on the temperature and time. The optimal temperature and time will be 540 degrees C and 1h. The Fenton oxidation will recover 60% adsorption capacity. For natural zeolite, regeneration can not fully recover the adsorption capacity with the two techniques and the regenerated natural zeolites by the two techniques are similar, showing 60% adsorption capacity of fresh sample. Kinetic studies indicate that the adsorption follows pseudo-second-order kinetics.     

接触辉光放电等离子体处理有机砷废水

洛克沙砷（ROX）饲料添加剂在农业的普遍使用,导致大量的ROX进入自然水体,引起环境污染。为了修复含ROX废水,首次提出采用接触辉光放电等离子体（CGDP）氧化ROX,并考察了多种因素对ROX降解效果的影响。结果表明,ROX能被CGDP完全氧化降解,且As（V）是其最终降解产物;输入能量的增加利于ROX的氧化,而pH值对ROX的降解影响较小;在辉光放电最佳条件（输入能量58 W,pH 4.0）下,加入100 μmol·L-1 ROX,42 min内降解率为97%,As（V）的生成量可达95 μmol·L-1。此外,加入一定量的Fe（II）,因其可以通过利用CGDP原位产生的H2O2通过芬顿反应产生大量额外的·OH,而能显著地催化ROX转化为无机砷。通过自由基捕获实验,证明了·OH在ROX降解中起主要作用并探索了其氧化降解机理。     

我国主要城市大气重金属的污染水平及分布特征

为研究我国城市大气中重金属(As、Cd、Cr、Mn、Ni和Pb)的污染水平及空间分布特征,通过CNKI、万方、维普、Science Direct、Google Scholar和PubMed等数据库检索并收集于2000—2014年10月期间发表的关于我国城市大气中重金属质量浓度的文献. 按照拟定的筛选标准筛选出59篇文献纳入分析研究,共涉及29个省(区、直辖市)53个城市,有效样本量大于5 863个. 其中,大气重金属质量浓度均以PM₁₀(采样测定结果)计. 结果表明:我国城市大气中ρ(As)、ρ(Cd)、ρ(Cr)、ρ(Mn)、ρ(Ni)和ρ(Pb)分别为27.7、14.1、60.9、220、37.5和290 ng/m3,均超过GB 3095—2012《环境空气质量标准》、欧盟《空气质量标准》和WHO(World Health Organization,世界卫生组织)《欧洲空气质量指南》中相应重金属质量浓度的年均标准限值或参考限值. 我国城市大气重金属污染主要分布在北方的京津冀、环渤海地区以及南方的珠江三角洲地区. 其中,Cd污染多分布在南方城市,Mn污染主要集中在华北和华东地区,As、Cr、Ni、Pb 4种重金属没有明显的空间分布特征. 大气中As、Cd、Cr、Ni、Mn和Pb的主要来源是化石燃料燃烧、金属冶炼以及交通废气排放等,其中煤炭等化石燃料的燃烧是其共同的污染来源.      

1691—1692年陕西瘟疫发生原因初探

历史时期瘟疫的研究对现代瘟疫的防治具有重要的意义。本文选取陕西省为研究区域,在大量收集历史文献资料的基础上,初步考察了康熙三十至三十一年(1691—1692年)陕西瘟疫发生的情况,并着重分析了这次瘟疫爆发的相关原因。结果表明,干旱灾害、社会风俗、治疫政策等是瘟疫爆发的主要诱因。     

An assessment of the effectiveness and impact of electrokinetic remediation for pyrene-contaminated soil

The effectiveness of electrokinetic remediation for pyrene-contaminated soil was investigated by an anode-cathode separated system using a salt bridge. The applied constant voltage was 24 V and the electrode gap was 24 cm. Two types of soil （sandy soil and loam soil） were selected because of their different conductive capabilities. The initial concentrations of pyrene in these soil samples were 261.3 mg/kg sandy soil and 259.8 mg/kg loam soil After treatment of the sandy soil and loam soil for seven days, 56.8% and 20.1% of the pyrene had been removed respectively. Under the same power supply voltage, the removal of the pollutant from the sandy soil was greater than that from the loam soil, due to the higher current and lower pH. Further analysis revealed that the effectiveness of electrokinetic remediation was affected by the energy expenditure, and was associated with changes in soil properties.     

河北省承德地区秸秆堆肥特性及腐熟度评价

以河北省承德地区的油葵秸秆、玉米秸秆、大豆秸秆与鸡粪为原料,设置4种不同配比（F1、F2、F3、F4）,于2009年秋末接种EM菌进行堆肥试验.通过对堆肥过程中堆体的温度、含水率、NH4＋-N、NO3--N、pH值、C/N、T值的测定,研究了不同配比对堆肥腐熟度的影响.采用大白菜种子发芽指数（GI）评价了堆肥的腐熟度和...     

纳米氧化铜对酿酒酵母的细胞毒性机制研究

以模式生物酿酒酵母BY4741为研究对象,测定了不同粒径的纳米CuO(CuO-NPs)及常规CuO在SD-Ura培养基中的水合粒径和溶出的可溶性铜含量,研究了CuO-NPs、常规CuO和Cu2+对酿酒酵母的细胞毒性效应及胞内活性氧(Reactive Oxide Species,ROS)的产生.结果发现,CuO-NPs对酵母的细胞毒性远大于常规CuO,而Cu2的细胞毒性最强,不同粒径的CuO-NPs对酵母的细胞毒性无显著性差异.酵母受试不同形态的铜4h后,常规CuO有30.75％～51.25％的可溶性铜溶出,而CuO-NPs溶出的可溶性铜高达77.32％～ 100％,且溶出的可溶性铜受pH的影响.Cu2产生的ROS最多,CuO-NPs产生的ROS的平均荧光强度(Mean fluorescence intensity,MFI)在1265～2329之间,但两者之间无显著性差异,常规CuO产生的ROS的平均荧光强度最低,约1000.上述试验表明,CuO-NPs对酵母的细胞毒性主要是由可溶性铜和ROS引起的,团聚作用和尺寸效应对CuO-NPs的毒性影响不明显.该结果可为纳米金属氧化物的安全性评价提供科学依据.     

ZnO的制备及其光催化性能

分别采用草酸沉淀法和柠檬酸络合法制备了纤锌矿型ZnO,通过X射线粉末衍射仪、扫描电子显微镜和透射电子显微镜对ZnO的结构和形貌进行了表征,并研究了所制备的ZnO对溶液中甲基橙的光催化降解性能.实验结果表明:草酸沉淀法制备的ZnO为小颗粒堆积而成的空心类柱状体,柠檬酸络合法制备的ZnO为小球形颗粒;草酸沉淀法制备的ZnO...     

Interactions between engineered nanoparticles and dissolved organic matter: A review on mechanisms and environmental effects

Dissolved organic matter (DOM) is ubiquitous in the environment and has high reactivity. Once engineered nanoparticles (ENPs) are released into natural systems, interactions of DOM with ENPs may significantly affect the fate and transport of ENPs, as well as the bioavailability and toxicity of ENPs to organisms. However, because of the complexity of DOM and the shortage of useful characterization methods, large knowledge gaps exist in our understanding of the interactions between DOM and ENPs. In this article, we systematically reviewed the interactions between DOM and ENPs, discussed the effects of DOM on the environmental behavior of ENPs, and described the changes in bioavailability and toxicity of ENPs caused by DOM. Critical evaluations of published references suggest further need for assessing and predicting the influences of DOM on the transport, transformation, bioavailability, and toxicity of ENPs in the environment.     

粉煤灰制聚合氯化铝铁和白碳黑新工艺

采用粉煤灰制备聚合氯化铝铁和白碳黑.该法共分一次酸浸、碱溶、焙烧、二次酸浸4个阶段.实验确定的最佳工艺条件为:一次酸浸阶段酸溶温度100℃,碱溶阶段m(氢氧化钠):m(活化高硅渣)=0.6,二次酸浸阶段m(碳酸钠):m(灰渣A)=0.8、盐酸质量分数20%.在此条件下Fe~(3+)和Al~(3+)的总浸出率分别为96.54%和86.67%.主要产品聚合氯化铝铁的质量符合GB15892-2003<水处理剂聚氯化铝>的标准;产品白碳黑的质量符合GBl0517-89<沉淀二氧化硅>的标准.