稀土在非TiO_2光催化剂的改性研究

近年来,运用稀土改性非TiO2光催化剂取得了显著成果.重点归纳、总结和分析了通过稀土离子单掺或共掺、稀土氧化物复合、上转换光催化与稀土固熔体等手段改性锌基、铋基光催化剂.简单介绍了稀土在钨基等其他基质的应用及新型稀土化合物光催化剂的构筑.发现稀土改性可以影响非TiO2光催化剂的晶格结构能带能、拓宽光谱响应范围和提高量子效率,是提高其光催化活性的有效途径.还对稀土在未来光催化的应用做了分析.     

改性纳米TiO2光催化剂的研究进展及表征方法

主要介绍了近几年来利用掺杂改性改善TiO2光催化性方面所取得的进展及常用的表征方法,并对其发展进行了展望。     

水热法制备高活性TiO2光催化剂的研究进展

简述了TiO2作为光催化剂应有的性质；着重介绍了高活性和超高活性TiO2光催化剂纳米粉体和薄膜的水热法制备研究情况；指出了该法尚须解决的问题及今后努力的方向。     

纳米TiO2光催化剂掺杂改性的研究进展

以光催化材料TiO2为研究对象,从金属、非金属掺杂及共掺杂改性出发,介绍了近些年来TiO2光催化剂与金属、非金属、双金属、双非金属、金属与非金属共掺杂的研究现状.研究发现:当对TiO2进行双元素共掺杂,且掺人元素及最适当时,能使TiO2的光催化性能进一步提高.     

低温合成TiO2/Fe3O4磁载光催化剂的光催化性能研究

采用化学共沉淀法合成的磁性纳米Fe3O4为磁核,以钛酸四丁酯为原料,通过溶胶-凝胶法,在较低温度下合成了TiO2/Fe3O4磁性光催化剂.利用XRD、TEM、SEM-EDX等分析方法对合成催化剂的相组成、形貌、粒度、元素分布等进行了表征;研究了不同焙烧温度及TiO2/Fe3O4比例对降解罗丹明B光催化活性及磁分离回收性能的影响.结果表明,在100、300和450℃焙烧温度下磁性光催化剂的催化活性依次降低,较低温度(100℃)制备的催化剂具备较高的催化活性;当TiO2质量分数处于67.3%～73.0%时,催化剂既具有较高的光催化降解活性也具有较好的磁分离回收性能;光催化剂TiO2/Fe3O4(100℃,TiO2质量分数70%)在循环使用5次后,在降解75 min时仍能达到对罗丹明B 99%的脱色率和90%的回收率.     

超声辅助分子自组装法合成硅胶负载TiO2光催化剂

超声辅助分子自组装法制备表面均匀和高催化活性的硅胶负载TiO2（TiO2-SiO2）光催化剂。采用XRD、SEM、FT-IR、PL等手段对制备产物晶型及形貌等进行了表征。以降解水中偶氮染料甲基橙为探针反应,评价了TiO2-SiO2的光催化活性。结果表明,500℃煅烧TiO2-SiO2的光催化活性最佳。     

稀土改性Ni/TiO_2光催化剂及其重复利用催化活性

用溶胶-凝胶法制备了La或Ce改性的0.3%Ni/TiO2(即La-Ni/TiO2或Ce-Ni/TiO2),考察了La-Ni/TiO2或Ce-Ni/TiO2在催化降解甲基橙水溶液过程中的重复利用性能,并用XRD、N2吸附-脱附以及XPS等手段对催化剂进行了表征分析。研究表明,适宜La和Ce掺杂量(La/Ti、Ce/Ti摩尔比)分别为0.15%和0.1%,适宜焙烧温度为400℃。在酸性条件下(pH=3),La-Ni/TiO2和Ce-Ni/TiO2与Ni/TiO2光降解甲基橙的能力相当,但La或Ce掺杂使Ni/TiO2催化剂的重复使用能力提高。催化剂上存在低结合能的低价钛离子(如Ti3+),低价钛离子的含量和结合能大小是衡量催化剂光催化降解活性的重要因素。可能是La或Ce使催化剂在使用过程中低价钛离子得到较好保留,从而使催化剂活性得到较好维持,催化剂重复使用性能提高。     

水热法合成Sb2O3／TiO2复合光催化剂

采用温和的水热法合成Sb2O3／TiO2纳米颗粒,并利用XRD、TEM对样品的晶型和形貌进行表征;以光催化降解甲基橙反应,研究了Sb2O3／TiO2的光催化性能。结果表明,用Sb2O3复合提高了TiO2的光催化活性,在140℃、水热反应12h的条件下,合成的0．5％Sb2O3／TiO2的光催化活性最佳。     

熔渣吸收TiO2夹杂物的研究

采用旋转动力学实验方法,模拟研究了含钛不绣钢连铸时熔融保护渣吸收TiO_2夹杂物的过程,探讨了CaO-SiO_2-CaF_2-BaO系渣中,CaF_2,BaO,TiO_2,Na_2B_4O_7,碱度(CaO/SiO_2)等因素对熔渣吸收TiO_2的速度以及CaTiO_3析出倾向的影响。     

在磷酸介质中水热合成纳米TiO2光催化剂

使用工业偏钛酸为前驱体，在磷酸介质中借助于水热合成方法，制备了二氧化钛纳米颗粒。通过透射电子显微镜（TEM）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、光催化活性检测仪等手段对所得的样品的形貌、晶型结构及光催化降解亚甲基蓝的性能进行了研究。结果表明，颗粒的形貌近似球形，所制得的产品均为锐钛矿相，在90℃下得到的纳米二氧化钛颗粒粒径为9nm，随着温度的升高得到的纳米晶粒逐渐变大（约17nm），且所得产品降解亚甲基蓝的能力较强。     

稀土出口价格与稀土储备

稀土出口价格和稀土储备是稀土研究的两个重要问题.从稀土的应用价值、相对稀缺性、生产的环境代价以及稀土供给的垄断特征,分析我国稀土出口应该有一个比较高的价格;从供求关系、市场结构、储备特征、储备对需求弹性和供给弹性的影响,分析储备对稀土出口价格的影响方向和影响效果;从储备的作用和稀土产业的未来发展目标,提出稀土储备的主要目的和方式.研究结果表明：稀土出口所形成的市场结构使我们丧失了稀土出口的议价能力;稀土国家储备在短期会对稀土出口价格提升产生一定的效果,但长期效果有限;稀土储备的主要目的应该是促进稀土应用产业的发展,并以稀土原矿（稀土资源）储备为主.     

A review of fractionations of rare earth elements in plants

Studies were carried out on several aspects of rare earth elements （REEs）, such as the theory and practice of their applications in agriculture, their geochemical behaviors in natural and agricultural ecosystems, the mechanisms for the increase of crop yield using REE fertilizer, and their toxicology. However, limited knowledge was available for the transfer processes and the features and mechanisms of distribution and fractionations of REEs inside plants. The characteristics of REE fractionations in plants can be used to ＂trace＂ the pathway of REE transportation from soils （solution） to plants. A better understanding of the mechanisms of REE fractionations was helpful to investigate the controlling factors, including both the internal and the external ones. The characteristics and mechanisms of REE fractionations in plants and their significance were reviewed. Furthermore, the prospect for these fields was discussed, in hope of providing a new way in studying the bioavailability of REEs and heavy metals.     

Local concentration of middle and heavy rare earth elements in the col on the weathered crust elution-deposited rare earth ores

This present study focused on investigating the content and relative enrichment multiple of rare earth elements(REEs) in different terrain of weathered ore body, and the value of light rare earth elements/middle and heavy rare earth elements(LREEs/HREEs), in order to understand the mobilization and redistribution of HREEs, Furthermore, the abrasion pH was investigated as well, The results show that the average contents of HREEs in the knap, ridge and col are 37.26, 61.71, and 271.3 μg/g, respectively. The value of LREEs/HREEs is decreased from 16.78 to 7.914 between knap and col and the relative enrichment multiple of HREEs is as follows: C_(Col-HREEs) C_(Ridge-HREEs) 0. It is indicated the HREEs is concentrated in the col and the enrichment degree of HREEs is stronger than the ridge and the knap. Rare earth elements fractionation is exhibited in the different terrain of weathered ore body. Based on this study, the finding that HREEs concentrate in the lower terrain of weathered crust elution-deposited rare earth ores, such as in the col, would become a marker or indicator to search for middle and heavy rare earth enriched zone.     

电感耦合等离子质谱法测定离子型稀土原矿中离子相稀土总量

采用电感耦合等离子质谱法(ICP-MS)直接测定离子型稀土原矿中离子相稀土总量,实验对浸取溶液、浸取溶液的浓度及用量、被测元素的同位素、样品酸度、内标元素、仪器的最佳工作参数进行了选择,建立了优化分析条件.单一元素标准加入的回收率为95%~105%,离子相稀土总量回收率为98.4%,相对标准偏差小于5%,测定范围为:0.010%~0.50%.方法准确可靠,操作简单,精密度和准确度都能满足分析要求.     

Dissolved rare earth elements estimation of ion-absorption rare earth ores using reflectance spectroscopy in south Jiangxi province,China

Ion-absorption rare earth ores are an important mineral resource in China. Nowadays, the unauthorized mining has become a serious problem, resulting in severe water pollution and the wastage of rare earth elements (REEs). Being able to estimate the concentration of dissolved REEs in water bodies near mines is essential for tackling this environmental problem. Conventionally, quantitative analyses of the contents of dissolved REEs are performed using laboratory-based techniques, which can be time consuming and costly. Spectral reflectance is a rapid and cost-effective means of characterizing the chemical compositions of light-absorbing materials. In this study, reflectance spectroscopy was performed on dissolved REEs, and the correlation between their reflectance characteristics and REE content was determined. A total of 50 aqueous media samples collected in south Jiangxi Province and 25 laboratory-produced aqueous media samples were tested, and their reflectance spectra and REE contents were measured using reflectance spectroscopy and inductively coupled plasma mass spectrometry, respectively. Next, the reflectance, differential reflectance, and absorption depth were analysed based on the REE content. Six diagnostic absorption features related to REEs are recognised in the visible and near-infrared wavelength regions, along with several smaller peaks. It indicates that the results of the absorption depth analysis are in accordance with the absorption spectra characteristics of the REEs, with the R² value being higher than 0.97. The intensity of each of the six absorption bands exhibits a linear correlation to the total REE content. Therefore, linear regression models can be derived for estimating the total concentration of REEs in aqueous media samples. What's more, the detection limit for REEs is determined to be about 30 μg/L. Thus, it can be concluded that reflectance spectroscopy is a suitable technique for estimating the concentration of dissolved REEs.     

Global rare earth resources and scenarios of future rare earth industry

It is known to all that China is abundant in rare earth resources.But rare earth deposits are really not that rare in the earth crust.In the five continents,i.e.Asia,Europe,Australia,North and South America,and Africa,there are about thirty four countries found to have rare earth deposits;Brazil might surpass China and rank the first in rare earth deposits.At present,investment in rare earth production was surged,there have been about 200 projects,and the total production for 25 of them would be more than 170 thousand tons after 2015,a multi-supply system on rare earths is being established worldwide.Cautions on the investment of rare earth production are involved.     

稀土元素对耐候钢元素偏析的影响

应用金属原位统计分布分析技术(OPA)研究了耐候钢铸锭中C、P、S、Cu、Si和Mn的宏观偏析规律,并分析了稀土元素对耐候钢中元素偏析的影响.结果表明,在30%～40%等轴晶率,20℃过热度下,元素C、S、P和Cu能产生严重的宏观偏析,C、S呈中心正偏析,P、Cu呈中心负偏析并伴随有反偏析,而Si和Mn的分布较为均匀.各个元素中心偏析位置完全相同.稀土元素在钢中的固溶度为10-5～10-4,固溶稀土元素可以细化枝晶,提高等轴晶率.钢中加入质量分数0.38%～0.55%的稀土元素可以有效改善C、S、P和Cu的宏观偏析.     

Inclusions modification in heat resistant steel containing rare earth elements

Based on the thermodynamic assessment of inclusions evolution, the modification experiments of inclusions containing rare earths were carried out in the Si–Mo furnace from 1600°C to 1500°C. The pure Si and Si–Al alloy were chosen as deoxidants under low and high initial oxygen content, respectively. The field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS) were employed to analyse the morphology and chemical compositions of inclusions in the samples. The spherical liquid Ce–Si–Al–O (Ce₄Si₅Al₅O_23.5) inclusions were observed in the steel, which was deoxidised by Si–Al alloy. The evolution mechanisms of inclusions were comprehensively discussed, and models for the formation of oxide inclusions were set up.     

Content of rare earth elements in Salvia miltiorrhiza bunge from different areas

Salvia miltiorrhiza bunge(SMB) has been widely used as a traditional Chinese medicine for a long time,and today more and more attention has been paid to the effective components in Chinese traditional medicine,especially to rare earth elements(REEs).14 kinds of REEs in SMB from different areas were analyzed by the methods of ICP-MS.The results showed that the total concentration of REEs(as REO,the same below) ranged from 8.43(as dry weight,the same below) to 37.30 mg/kg,and the concentrations of La,Ce and Nd were higher than 2 mg/kg except Nd in SMB from Beijing.So the total concentration of REEs in SMB was much higher than that in rice,corn and barley,which could be the mechanism of curative effect of SMB on cardiovascular cerebrovascular system,digestive system,respiratory system,countershock and antibiotic.The character of other elements and the content of REEs in soil from different areas should be responsible for the difference,but the allocation mechanism of REEs in SMB should be further studied.     

Effects of the accumulation of the rare earth elements on soil macrofauna community

The accumulation of rare earth elements(REEs)in soil has occurred due to the pollution caused by the exploitation of rare earth resources and the wide rare earth fertilizers in agriculture.The accumulation of REEs has a toxic effect on the soil macrofauna community.12study samples were collected near a mine tailings dam with a large amount of REEs by distance gradient sample method.The total concentration of REEs was analyzed and the results were compared with that of the sample from a control site.The effects of the amount of REEs in the soil on the soil macrofauna community were also analyzed.The results showed that the accumulation of REEs in soil was significant in the study area and its concentration was strongly correlated with the distance from the pollution source.One-way ANOVA analysis indicated the significant differences in soil macrofauna communities among the different sites.The ordination obtained through the redundancy analysis demonstrated that the concentration of REEs and the total nitrogen,total potassium and pH,had affected the soil macrofauna community.A small amount of REEs in the soil can promote the diversity of soil macrofauna,but a large amount of REEs can reduce its diversity.The insect groups of Carabidae and Dermaptera were comparatively sensitive to the concentration of REEs in soil,and could be used as an indicator of soil pollution of REEs.However,the Formicidae and Stibaropus formosanus exhibited a high tolerance to REEs in soil.We believe that it is very important for the soil environment protection to strictly control the application of the rare earth fertilizers in agriculture in China.