1,720,955 research outputs found
Transforming heavy metal sludge into spinel materials by high-temperature process
No full text重金屬污泥為有害事業廢棄物之一，若未妥善處理將會危害環境及人體健康。以熱處理技術將重金屬汙泥轉化為礦物結構或陶瓷材料，可安定穩定化汙泥中之重金屬，且具有將廢棄污泥轉化為有用資材之潛勢，例如尖晶石材料。由於重金屬污泥所含成分與尖晶石合成原料相似，故以熱處理程序將重金屬污泥轉化為尖晶石材料並同時達到安定穩定化之目的是值得期待的。
研究中除評估重金屬污泥轉化為高經濟價值尖晶石材料之可行性外，也嘗試應用微波加熱技術合成尖晶石材料。實驗中將探討反應溫度、加熱時間、微波功率及不同氧化物之影響，並分析合成產物之物化特性。尖晶石轉化效率、安定化效率、固相化學反應及不同氧化物競爭機制也將一併討論。最後將尖晶石合成技術應用於實場污泥上，證實其實際應用之可行性，且進行以尖晶石吸附重金屬之初步試驗，以達到廢棄物資材化之最終目的。
結果顯示以熱處理程序在3小時800 °C操作條件下，模擬污泥可被轉化為銅鐵尖晶石(CuFe2O4)與銅鋁尖晶石(CuAl2O4)材料。而銅鐵尖晶石具有低溫(800~900 °C) tetragonal相及高溫(> 1000 °C) cubic相兩種不同晶型；而銅鋁尖晶石只具有單一晶相。在溫度超過1100 °C之後，兩種尖晶石皆會分解為delafossite相(CuFeO2及CuAlO2)。在經過長時間TCLP的測試後，兩種含銅尖晶石皆可大幅降低銅的溶出並達到安定穩定化的效果，而銅鐵尖晶石之安定穩定化效果優於銅鋁尖晶石。以FTIR鑑定尖晶石在四面體與八面體結構的吸收波段，也可證明尖晶石的形成，並證實銅離子在結構中的擴散是形成不同晶相銅鐵尖晶石之主因。而低溫tetragonal相之尖晶石具有硬磁性；高溫cubic相之尖晶石則具有軟磁性。因不同處理條件下所產生不同特性之尖晶石，將會影響後續廢棄物資材化的方向。而在同時具有氧化鐵及氧化鋁的汙泥中，氧化銅會優先與氧化鐵形成銅鐵尖晶石，且尖晶石於高溫之分解情形也將受到雜質之影響。另外以混和式微波加熱技術可成功合成兩種尖晶石，且可大幅縮短反應時間及減少能源消耗，比傳統加熱方式更具優勢。
在後續應用結果方面，實場污泥在未經過調質前，可於800 °C時形成銅鋁尖晶石，但高溫時在雜質的干擾下，尖晶石不會分解為delafossite相。實場汙泥經過調值燒結後，銅溶出濃度可較未調值更低，證實以高溫合成尖晶石法可有效將實場重金屬汙泥轉化為尖晶石結構並達成安定穩定化之目標。而重金屬吸附及再利用實驗中，磁性銅鐵尖晶石可以靜電吸附移除五種重金屬離子(Cu2+, Pb2+, Cd2+, Ni2+及Zn2+)，五種金屬在12小時吸附時間的處理效率依序為92%, 90%, 81%, 80%及55%，移除效率會隨著pH增加而升高。再利用實驗也證實利用磁性分離技術可有效回收磁性吸附劑並重複使用，在六次重複試驗後，吸附效率仍可達80%。因此由上述結果可證實利用熱處理技術可將重金屬污泥轉化為尖晶石材料，除達到污泥安定穩定化之目標，也可達成廢棄物資源化再利用之最終目的。Heavy metal sludge from metal surface treatment, anodizing, plating, and printed circuit board manufacture are hazardous solid waste. Stabilizing metal sludge via thermal treatment has the potential to convert hazardous metal sludge into mineral phase and reusable product, such as spinel ceramics. Owing to the composition of the heavy metal sludge is similar to the precursors of spinel mineral, including divalent metal oxides and trivalent metal oxides, the sintering processes for stabilizing or transforming the metal oxides into spinel structure will be expected.
The goal of this study is to evaluate the technical feasibility of incorporating heavy metal sludge into high-value spinel ceramics by thermal process, and thus to reduce the environmental hazard and promote the economic value of solid waste. The study tried to apply thermal processes, including conventional way and microwave energy, on the transforamtion of heavy metal sludge. The effects of temperature, sintering time, microwave power and different oxides were investigated in the study. The reactive mechanisms of reactants and the feasibility of following applications were also discussed.
Results indicated that CuFe2O4 and CuAl2O4 were also effectively formed at around 800 °C by the ferric oxide and gamma alumina precursors with 3 h of short sintering, respectively. Transformation of CuFe2O4 was found on two crystallographic spinel structures: the low-temperature (800~900 °C) tetragonal phase (t-CuFe2O4) and the high-temperature (~1000 °C) cubic phase (c-CuFe2O4), and CuAl2O4 was only found one crystallographic structures during the thermal process. At higher temperatures (~1100 °C), the formation of cuprous ferrite delafossite (CuFeO2) and cuprous aluminate delafossite (CuAlO2) phase from the dissociation of spinel was also noted. Both CuFe2O4 and CuAl2O4 spinel had a better intrinsic resistance to the acidic environment when compared to the CuO phase according to results of the modified TCLP test. But the CuFe2O4 structure is more stable under acidic environment than the CuAl2O4 structure. The observation of tetrahedral and octahedral absorption bands from FTIR results proved the formation of spinel structure, and the shift phenomenon was also confirmed by the occupancy of cations in different sites. Tetragonal phase CuFe2O4 provided hard magnetic characteristic at low temperatures, and the cubic phase CuFe2O4 provided soft magnetic characteristics at high temperatures. Different characteristics of CuFe2O4 produced at different temperatures will affect further applications on the environmental engineering. In the sample with hematite and gamma alumina, copper oxide would prefer to incorporate with Fe2O3 for forming spinel structure. CuFe2O4 and CuAl2O4 spinel were also successfully synthesized by hybrid microwave process which could significantly reduce the processing time and energy. The raw heavy metal sludge without adjustment could be transformed into CuAl2O4 spinel at the temperature of 800 °C. However, the dissociation of CuAl2O4 was not observed at high temperature, which was due to the impurities existed in samples. The raw heavy metal sludge could also be transformed into CuAl2O4 and significantly decreased the Cu leaching concentration after adjustment by thermal process. The results confirmed that the spinel synthesized technique could be successfully applied to the filed heavy metal sludge to get the objective of stabilization.
The adsorption/reusability experiments demonstrated that CuFe2O4 particles could be used as a magnetic adsorbent by electrostatic attraction to remove various metal ions (Cu2+, Pb2+, Cd2+, Ni2+, and Zn2+). The removal efficiencies of Cu2+, Pb2+, Cd2+, Ni2+, and Zn2+ with 12 h of contacting time were about 92%, 90%, 81%, 80%, and 55%, respectively. The removal efficiency of Cu2+ and Pb2+ gradually increased with the increase of pH. The regeneration tests also showed that the removal efficiency of Cu2+ during six cycles was > 80%, and the magnetic CuFe2O4 particles could repeatedly be used for metal ions removal in aqueous environments. Therefore, transforming heavy metal sludge into spinel materials could not obtain only the objective of stabilization but also the reutilization of solid waste
Stabilization and phase transformation of CuFe2O4 sintered from simulated copper-laden sludge
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
