1,721,005 research outputs found
Advanced treatment of industrial wastewater by membrane filtration and ozonization
No full textThe present paper deals with nanofiltration (NF), ultrafiltration (UF) and ozonization pilot scale tests for revamping and improvement of an industrial plant that treats wastewaters coming from a wide range of hazardous industrial processes. Tests demonstrated that the best treatment is NF whose feed stream comes from sand filters rather than first ozonization stage before final discharge of the effluent. NF rejection coefficients resulted to be 31% for TDS, 94% COD, 9% Cl-, 47% surfactants, 66% phenols and 91% SO4 2-. UF was tested as NF pre-treatment but results were not so promising in terms of rejection and permeate flux, as well as fouling reduction. Other experimental tests were carried out in order to understand where to recycle the NF retentate: the best treatment in terms of COD reduction and biodegradability was ozonization followed by recycling to the physico-chemical stage. In the same manner, it was found that ozonization of the NF permeate is the best process solution before final treatment and discharge of the effluent. © 2012 Elsevier B.V
Adsorption onto activated carbon for molybdenum recovery from leach liquors of exhausted hydrotreating catalysts
No full textThis paper investigated molybdenum recovery from acid leach liquors of exhausted hydrotreating catalysts. Adsorption onto activated carbon was used to separate molybdenum from other metals contained in these leach liquors, namely nickel, cobalt and vanadium. Kinetic tests using Mo-bearing solutions denoted that the rate of adsorption depends on the amount of Mo in solution with an estimated order of reaction of 0.9 +/- 0.3. Equilibrium sorption tests showed that metal accumulation presents a bell-shaped behaviour as pH changes with a maximum sorption capacity around pH 5. Preliminary test in column reactor fed with Mo-bearing solution confirmed the sorption capacity estimated in batch tests (0.230 g/g). Sorption tests in batch reactors using leach liquor ([Mo] = 3.06 g/L, [V] = 5.84 g/L, [Ni] = 4.48 g/L, [Al] = 1.77 g/L) denoted that Mo can be quantitatively and selectively removed from solution (99% removal for Mo, 24 +/- 2% for Al, 19% for V and 0% for Ni) with no significant reduction of sorption capacity towards Mo (0.250 g/g). Preliminary sorption-desorption cycles denoted that Mo removal was larger than 90% in each cycle, whilst the other metals were minimally removed (Al and V) or completely rejected (Ni). (C) 2011 Elsevier B.V. All rights reserved
Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation
No full textThis work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 22 full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H2O2 concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction.
Two series of precipitation tests for zinc are carried out: a 22 full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na2S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%.
Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%
Zirconia and alumina based catalysts for steam reforming of naphthalene
No full textThe present paper deals with experimentation of ZrO2 and Al2O3-supported catalysts for conversion of naphthalene, chosen as tar model compound of pyrolysis or gasification syngas. In particular, the reforming capacity of active metals and promoters such as Co, Ni, Fe, Cr, Ce and Pt was tested in a fixed bed reactor at temperature from 400 to 900 degrees C. As regards ZrO2-supported catalysts, the best results were achieved by the Ni/Fe/Pt catalyst with 96% naphthalene conversion, 78% and 280% as CO and H-2 production yield at 800 degrees C. Regarding Al2O3-supported catalysts, they were more active on average than the zirconia ones, achieving a very good performance even at 500 degrees C (90-100% naphthalene conversion, 30-40% CO yield and 300-350% H-2 yield at 550 degrees C). Influence of different amounts of alumina, montmorillonite and carbon on carrier composition as well as pellets' size were also studied. Both zirconia and alumina catalysts showed deactivation at higher temperatures due to coke deposition, resulting in a strong H-2 production drop. Regeneration of catalysts by O-2 and steam as well as activation by H-2 were also studied. The activated catalyst was able to convert more than 99% naphthalene at 450 degrees C with a CO and H-2 production yield of 26% and 420%, respectively. (C) 2012 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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