我国农用稀土光转换材料研究进展

概述了近年来我国农用稀土光转换材料的研究进展及目前存在的问题.重点介绍了转光剂的类型及研究现状,展望了稀土光转换材料的发展前景.     

Analysing the influence of visualisations in global environmental governance

Visualisations can highly contribute to the importance and authority of new ideas, concepts, and knowledge claims. Among the many visualisations, few become well-known and influential in environmental governance. Whilst these have been objects of specific research, this study questions what constitutes and underpins their influence. For this, the paper codifies influential visualisations and defines criteria for studying their visual characteristics. The criteria are applied to two case studies, the “traffic light” and the “planetary boundaries” diagrams. To increase the validity of the findings, the study also introduces two “failure cases” as a plausibility check.     

Formation characteristics of PCDD and PCDF during pyrolysis processes

In recent years, pyrolysis processes have become technologies developed to industrial scale and discussed as alternatives to the existing waste combustion technology. However, little information is published regarding PCDD/F formation characteristics during pyrolysis processes. Two common shredder fractions – industrial light shredder (ILS) and refrigerators (REF) – both with high chlorine and copper content were pyrolysed for this pyrolysis study using a pilot plant with a capacity of 100 kg/h. At oxygen concentrations below 2% and temperatures between 430°C and 470°C, considerable amounts of PCDD/F were formed during the pyrolysis. More than 90% of total TEQ was found in the oil fraction (gas phase). The PCDD/PCDF ratio and the homologue pattern differed significantly from those formed during waste incineration. Considering mono- to octachlorinated congeners, up to 400 times more PCDF were formed compared to PCDD. For the investigated pyrolysis conditions, the formation of low chlorinated congeners was highly favoured. The distribution of TEQ within the individual congeners were very similar in all investigated runs. More than 80% of total TEQ stem from 2,3,7,8-substituted T₄CDF and P₅CDF. The isomer pattern, however, did not show significant differences compared to the common waste incineration pattern suggesting that the basic formation routes are similar.     

Decomposition of aqueous chlorinated contaminants by UV irradiation with H2O2

In the present study, the decomposition rates of carbon tetrachloride (CCl₄) and 2,4-dichlorophenol (2,4-DCP) in water by the ultraviolet (UV) light irradiation alone and H₂O₂/UV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources (low and medium pressure Hg arc) in H₂O₂/UV processes. The low or medium UV lamp alone resulted in a 60%–90% decomposition of 2,4-DCP while a slight addition of H₂O₂ resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3–6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CCl₄, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CCl₄ at shorter wavelength (210–220 nm) is about 20 to 50 times higher than that at 254 nm. However, adding H₂O₂ to the medium pressure UV lamp system rendered a negative oxidation rate because H₂O₂ acted as a UV absorber being competitive with CCl₄ due to negligible reaction between CCl₄ and OH radicals. The results from the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants.     

污染源区结构特征对Tween 80去除DNAPL效果的影响

选择四氯乙烯（PCE）作为特征污染物,通过二维砂箱实验探究3种介质情景中,污染源区结构特征对Tween 80冲洗去除PCE的影响.采用透射光法监测PCE的运移及去除过程,定量测定PCE的饱和度.进而采用不连续的离散状与连续的池状PCE体积比（GTP）定量表征污染源区结构特征.结果表明,PCE在含透镜体介质中运移时,运移路径延长,离散状PCE增多.离散状PCE与Tween 80溶液的有效接触面积较大,被优先溶解去除,而细砂层上部的污染池的比表面积和接触面积较小,溶解能力有限,远比运移路径上的PCE难以去除.此外,初始离散状PCE较多,GTP较大,有利于池状PCE溶解转变为离散状PCE,PCE去除率增大.因此对于实际污染场地,需要详细分析DNAPLs污染源区结构特征,以助于评估表面活性剂冲洗技术的修复效率及试剂消耗.     

表面增强拉曼散射技术鉴别大肠杆菌和志贺氏菌的研究

以整个大肠杆菌和志贺氏菌为研究对象,通过和纳米银颗粒混合制片,利用表面增强拉曼效应检测并区分大肠杆菌和志贺氏菌.结果表明,未与纳米银颗粒混合的大肠杆菌和志贺氏菌没有明显的拉曼信号,而与纳米银颗粒混合后有明显的拉曼信号,二者有明显的区别,且重现性良好,可为鉴别大肠杆菌和志贺氏菌病原体研究及实际应用提供依据.     

Ag@AgCl催化剂的制备及可见光降解三聚氰胺

在超声波辅助作用下制备了Ag@AgCl可见光催化剂,采用紫外可见分光光度计、扫描电镜(SEM)对该催化剂进行了表征,该催化剂在可见光区有较强的吸收,粒径在微米级.以三聚氰胺为模型化合物测试其可见光催化性能.研究发现,该催化剂在可见光照下,不仅可以使三聚氰胺发生脱氨基反应,而且能使其环结构破坏,但却不能催化氰脲酸降解.通过除氧实验、空穴捕获、顺磁共振等实验测试,对其可能的催化降解机理进行了探讨.     

漂珠负载Ce掺杂Bi_2O_3光催化剂的制备及其处理含油废水性能

以漂珠为载体制备了Ce掺杂Bi_2O_3可见光响应催化剂。采用XRD、FTIR、SEM和DRS等表征手段对制备的催化剂进行了结构和形貌研究。以4#燃料油配制模拟含油废水,研究了催化剂在可见光作用下的光催化性能。表征结果显示:Ce掺杂Bi_2O_3成功负载到漂珠载体上,以四方相β-Bi_2O_3、α-Bi_2O_3和Ce O_2的形式存在;与空白Bi_2O_3相比,Ce掺杂Bi_2O_3固有的边带吸收波长拓展至544 nm。实验结果表明,在500℃条件下焙烧3 h制备的催化剂光催化效率最高,光照70 min时,油去除率可达88%。     

O(1D)与CF3Cl的反应研究

研究ＣＦ₃Ｃｌ－Ｏ₃体系在２５３．７ｎｍ 紫外光照射下所引发的Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应．Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应最终产物为ＣＦ₂Ｏ、Ｆ₂、Ｃｌ₂,并讨论了Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应机理．研究表明,在本实验条件的２５３．７ｎｍ 紫外光作用下,ＣＦ₃Ｃｌ自身不发生解离,同时Ｏ（³Ｐ）不与ＣＦ₃Ｃｌ发生反应．此外外加气体（氮气、氧气）对Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应有较强的淬灭作用     

上转换发光剂掺杂纳米TiO2的制备及可见光降解乙基紫的研究

合成了一种新型含有稀土金属Er的上转换发光剂40CdF₂·60BaF₂·1.6Er₂O₃,此上转换发光剂在488 nm可见光的激发下,产生了5个波长均小于387 nm的上转换紫外光发射峰.采用超声波分散的方法制备出了上转换发光剂掺杂的纳米TiO₂可见光光催化剂.利用X-射线衍射(XRD)及透射电镜(TEM)对催化剂进行了表征.以乙基紫染料为研究对象,研究了在(三基色灯下发出的)可见光的照射下该可见光光催化剂的催化降解性能,并与未掺杂的纳米TiO₂粉末的催化性能进行了对比.结果表明,作为掺杂成分的上转换发光剂可有效地将可见光转化为紫外光并被纳米TiO₂粉末吸收利用,在可见光照射12.0 h后乙基紫降解率达到了99.68%,大大高于未掺杂纳米TiO2时的降解率.