1,720,982 research outputs found
Il trattamento chimico-fisico di tannini sintetici mediante l’utilizzo di coagulanti misti organici = Treatment of synthetic tannins by chemical coagulation through metallorganic coagulants
No full textI tannini sono composti presenti in molti tipi diacque di scarico e si caratterizzano per la loro scarsa biode-gradabilità. I tannini naturali sono facilmente eliminabili conun trattamento chimico fisico con l’uso di PAC o cloruro fer-rico, mentre i tannini sintetici non sono suscettibili di abbat-timento con simili trattamenti. Esistono, inoltre, numerosicomposti chimici polifenolici molto simili ai tannini che ven-gono difficilmente eliminati con il normale trattamento chi-mico fisico. L’attività di ricerca svolta è stata finalizzata allavalutazione dell’efficacia di alcuni coagulanti a base di resinesintetiche capaci di insolubilizzare anche parzialmente i tan-nini che possono poi essere abbattuti con la chiariflocculazio-ne tradizionale. In definitiva è stato messo a punto un coagu-lante misto di discreta efficacia.Tannins are present in several kind of wastewater as well as they are low biodegradable. Natural tannins are easi- ly removable by means of chemical-physical treatment proces- ses with PAC or ferric chloride, while the same process is not useful for the removal of synthetic tannins. Moreover, there are several polifenolic compounds (very similar to tannins) diffi- cult to remove by means of physicochemical treatment, as well. The aim of this paper was to test several coagulants based on synthetic resins suitable to partially insolubilize the tannins. Finally, a mixed coagulant with a valuable efficacy was set up
Il trattamento chimico-fisico di tannini sintetici mediante l’utilizzo di coagulanti misti organici = Treatment of synthetic tannins by chemical coagulation through metallorganic coagulants
No full textI tannini sono composti presenti in molti tipi diacque di scarico e si caratterizzano per la loro scarsa biode-gradabilità. I tannini naturali sono facilmente eliminabili conun trattamento chimico fisico con l’uso di PAC o cloruro fer-rico, mentre i tannini sintetici non sono suscettibili di abbat-timento con simili trattamenti. Esistono, inoltre, numerosicomposti chimici polifenolici molto simili ai tannini che ven-gono difficilmente eliminati con il normale trattamento chi-mico fisico. L’attività di ricerca svolta è stata finalizzata allavalutazione dell’efficacia di alcuni coagulanti a base di resinesintetiche capaci di insolubilizzare anche parzialmente i tan-nini che possono poi essere abbattuti con la chiariflocculazio-ne tradizionale. In definitiva è stato messo a punto un coagu-lante misto di discreta efficacia.Tannins are present in several kind of wastewater as well as they are low biodegradable. Natural tannins are easi- ly removable by means of chemical-physical treatment proces- ses with PAC or ferric chloride, while the same process is not useful for the removal of synthetic tannins. Moreover, there are several polifenolic compounds (very similar to tannins) diffi- cult to remove by means of physicochemical treatment, as well. The aim of this paper was to test several coagulants based on synthetic resins suitable to partially insolubilize the tannins. Finally, a mixed coagulant with a valuable efficacy was set up
La depurazione dei reflui degli impianti di produzione del biodiesel = Purification of waste from biodiesel production plants
No full textBiofuels production, particularly biodiesel, is an industrial activity whose budge is increasing rapidly. Industrial process produces wastewater with high organic carbon concentration from methyl alcohol, glycerine, fatty acids and a small amount of biodiesel, and high salts con- centration. These wastewaters are readily biodegradable but wastewater treatment plants need large volume in oxi- dation basins and chemical – physics treatments to elimi- nate carbon not readily biodegradable and to reduce salts concentration. Reverse osmosis treatment is an efficient remedy with plane membranes but it is an expensive treatment also for the reduction of concentrate. It’s possible to use less expensive treatment if salts concentration are reduced during industrial productive processes.La produzione di biocarburanti, in particolarebiodiesel, sta diventando una attività industriale sempre piùdiffusa. Il processo produttivo genera reflui ad alto caricoorganico contenenti metanolo, glicerina, acidi grassi e trac-ce di biodiesel nonché composti salini ad elevate concentra-zioni. Tali reflui sono facilmente biodegradabili ma hannonecessità di volumi e tempi di ritenzione notevoli ed infinenecessitano comunque di trattamenti chimico fisici per eli-minare la frazione residua bioresistente ed abbattere la sali-nità residua. I trattamenti ad osmosi inversa sono efficaci sesi usano le membrane piane ma risultano anche onerosidovendo poi ridurre il concentrato salino derivante dal trat-tamento a membrane. I trattamenti possono essere moltopiù semplici ed economici qualora si riesca a ridurre amonte la salinità dei reflui
The cosmic X-ray background level at its emission peak
No full textWe discuss an accurate measurement of the CXB in the 15-50 keV range performed with the Phoswich Detection System (PDS) instrument aboard the BeppoSAX satellite, whose results have already been recently reported elsewhere [1]. Unlike the recently reported 2-10 keV CXB measurements obtained with the imaging instruments aboard the X-ray satellites BeppoSAX, XMM-Newton, and Chandra that give CXB intensities systematically higher than those obtained with HEAO-1, using the BeppoSAX PDS pointings at high galactic latitude (|b|>15°) we measure a CXB spectrum and intensity level in the 15-50 keV energy band, which are consistent with those obtained with HEAO-1. Astrophysical consequences are discussed
The Cosmic X-ray Background at the peak of its emission: new results and implications
No full textWe discuss an accurate measurement of the CXB in the 15-50 keV range performed with the Phoswich Detection System (PDS) instrument aboard the BeppoSAX satellite, whose results have already been recently reported elsewhere [1]. Unlike the recently reported 2-10 keV CXB measurements obtained with the imaging instruments aboard the X-ray satellites BeppoSAX, XMM-Newton, and Chandra that give CXB intensities systematically higher than those obtained with HEAO-1, using the BeppoSAX PDS pointings at high galactic latitude (|b|>15°) we measure a CXB spectrum and intensity level in the 15-50 keV energy band, which are consistent with those obtained with HEAO-1. Astrophysical consequences are discussed
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
Possible physical explanation of the intrinsic Ep,i-“intensity” correlation commonly used to “standardize” GRBs
Full text linkIt is recognized that very likely the correlation between peak energy Ep and bolometric intensity is intrinsic to GRBs. However, its physical origin is still debated. In this paper, we will discuss a possible interpretation of the correlation in the light of a GRB prompt emission spectral model, GRBCOMP, proposed in [L. Titarchuk, R. Farinelli, F. Frontera and L. Amati, Astrophys. J. 752 (2012) 116]. GRBCOMP is essentially a photospheric model for the prompt emission of GRBs. Its main ingredients are a thermal bath of soft seed photons and a subrelativistically expanding outflow plasma, consequence of the star explosion. The emerging spectrum is the result of two phases: first, up to the photospheric radius, Comptonization of a subrelativistic electron outflow with thermal bath of soft photons, then, convolution of the Comptonized photons in the first phase with a Green function. The result of this convolution is consistent with different physical processes, in particular Inverse Compton. GRBCOMP has been successfully tested using a significant sample of GRB time resolved spectra in the broad energy band from 2keV to 2MeV [F. Frontera, L. Amati, R. Farinelli, S. Dichiara, C. Guidorzi, R. Landi and L. Titarchuk, Astrophys. J. 779 (2013) 175]
A comparison of the efficacy of organic and mixed-organic polymers with polyaluminium chloride in chemically assisted primary sedimentation (CAPS)
No full textCAPS is the acronym for chemically assisted primary sedimentation, which consists of adding chemicals to raw urban wastewater to increase the efficacy of coagulation, flocculation and sedimentation. The principal benefits of CAPS are: upgrading of urban wastewater treatment plants; increasing efficacy of primary sedimentation; and the major production of energy from the anaerobic digestion of primary sludge. Metal coagulants are usually used because they are both effective and cheap, but they can cause damage to the biological processes of anaerobic digestion. Generally, biodegradable compounds do not have these drawbacks, but they are comparatively more expensive. Both metal coagulants and biodegradable compounds have preferential and penalizing properties in terms of CAPS application. The problem can be solved by means of a multi-criteria analysis. For this purpose, a series of tests was performed in order to compare the efficacy of several organic and mixed-organic polymers with that of polyaluminium chloride (PACl) under specific conditions. The multi-criteria analysis was carried out coupling the simple additive weighting method with the paired comparison technique as a tool to evaluate the criteria priorities. Five criteria with the following priorities were used: chemical oxygen demand (COD) removal > turbidity, SV60>coagulant dose, and coagulant cost. The PACl was the best alternative in 70% of the cases. The CAPS process using PACl made it possible to obtain an average COD removal of 68% compared with 38% obtained, on average, with natural sedimentation and 61% obtained, on average, with the best PACl alternatives (cationic polyacrylamide, natural cationic polymer, dicyandiamide resin)
A comparison of the efficacy of organic and mixed-organic polymers with polyaluminium chloride in chemically assisted primary sedimentation (CAPS)
No full textCAPS is the acronym for chemically assisted primary sedimentation, which consists of adding chemicals to raw urban wastewater to increase the efficacy of coagulation, flocculation and sedimentation. The principal benefits of CAPS are: upgrading of urban wastewater treatment plants; increasing efficacy of primary sedimentation; and the major production of energy from the anaerobic digestion of primary sludge. Metal coagulants are usually used because they are both effective and cheap, but they can cause damage to the biological processes of anaerobic digestion. Generally, biodegradable compounds do not have these drawbacks, but they are comparatively more expensive. Both metal coagulants and biodegradable compounds have preferential and penalizing properties in terms of CAPS application. The problem can be solved by means of a multicriteria analysis. For this purpose, a series of tests was performed in order to compare the efficacy of several organic and mixed-organic polymers with that of polyaluminium chloride (PACl) under specific conditions. The multi-criteria analysis was carried out coupling the simple additive weighting method with the paired comparison technique as a tool to evaluate the criteria priorities. Five criteria with the following priorities were used: chemical oxygen demand (COD) removal > turbidity, SV60 > coagulant dose, and coagulant cost. The PACl was the best alternative in 70% of the cases. The CAPS process using PACl made it possible to obtain an average COD removal of 68% compared with 38% obtained, on average, with natural sedimentation and 61% obtained, on average, with the best PACl alternatives (cationic polyacrylamide, natural cationic polymer, dicyandiamide resin). © 2013 Taylor & Francis
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