1,721,005 research outputs found
SCUOLA ESTIVA DI RICERCA EDUCATIVA E DIDATTICA CHIMICA “ULDERICO SEGRE” Riflettere sulle conoscenze per favorire un apprendimento significativo
No full textNei giorni 10-15 Luglio 2010 è stata organizzata a Ferrara una scuola di ricerca educativa e didattica chimica “Ulderico Segre” .
L'organizzazione è stata a carico della Società Chimica Italiana, divisione di Didattica della Chimica e del progetto laurre Scientifiche in collaborazione con il referente locale, prof. M.C. Pietrogrande.
Alla Scuola hanno partecipato circa 20 giovani ricercatori universitari e personale non strutturato (dottorandi e assegnisti).
L’obiettivo della scuola è mostrare che per migliorare la propria professionalità di docente è necessario svolgere attività di ricerca in didattica o saper adattare i risultati
conseguiti da altri ricercatori.
La scelta del tema di riflessione di questa edizione è stata motivata dall’importanza dei modelli per interpretare e prevedere le proprietà delle sostanze e le loro trasformazioni e dalla consapevolezza che la modellizzazione, pur essendo uno
strumento molto efficace, non è tuttavia priva di insidie sul piano didattico a causa del rischio di confondere le rappresentazioni dei fenomeni con i fenomeni stessi.
Il metodo di lavoro nella Scuola si basa sulla massima interazione tra tutti i partecipanti: un numero limitato di lezioni frontali, seguite da dibattiti, confronti e lavori di gruppo su contenuti di particolare rilevanza concettuale. L’obiettivo è duplice: valutare l’accessibilità dei contenuti considerati e riflettere sui diversi possibili approcci al processo di
insegnamento/apprendimento
Determination of volatile and non-volatile organic acids in technical sugar solutions by ion-exclusion chromatography
No full textVolatile and non-volatile organic acids present in sugar process juices were separated by ion-exclusion chromatography on an HPICE-AS1 cation-exchange column (H+ form) using both dilute hydrochloric acid and 2-propanol-water solutions of tridecafluoroheptanoic acid. Coupled with an anion-exchange micromembrane suppressor, a conductivity detector made it possible to reveal citric, tartaric, gluconic, malic, lactic, succinic, glycolic, formic, acetic and pyrrolidonecarboxylic acid in the presence of inorganic acids and non-ionic organic matter. In sugar process juices subjected to alkaline and/or oxidative treatment, increasing concentrations of the major acid components, i.e., acetic, formic and lactic acid, can be measured. The analysis is performed in the presence of sucrose and a simple clean-up by rapid batch treatment with a cation exchanger (H+ form) is sufficient to remove proteins and cations. The multiple standard addition procedure is used for calibration. © 1991
Chromosorb 101 as a packing material for reversed-phase chromatography
No full textA procedure for preparing a Chromosorb 101 liquid chromatographic column is described. Some column parameters such as the permeability, efficiency and peak asymmetry factor were calculated. The elution of some benzene and phenol derivatives from the polymeric column with different mobile phases was performed. The results showed that some gas chromatographic adsorbents such as Chromosorb 101 can be used as packings for high-performance liquid chromatographic columns. The behaviour of these styrene copolymers resembles that of a C18 silica bonded phase. © 1987
Absolute characterization of colloids by field-flow fractionation
No full textThe fundamental aspects of Field-Flow Fractionation (FFF) techniques in their features of being absolute characterization techniques for colloids - particles, macromolecules and molecular assemblies - are reviewed. The different physico chemical properties which can be determined, are classified as key, primary or secondary quantities according to whether they are obtained respectively from a single FFF measurement, from additional informations and/or measurements about the analyte or from differential measurements about different analytes using a given FFF method. Emphasis is given to the stepwise hypotheses required in determining different physicochemical properties. The different possible procedures for obtaining primary quantities for both monodisperse or quasi-monodisperse species and distributions of primary quantities for polydisperse species are described. Advantages and drawbacks are reported
Enviromental problems related to leachates from U.S.W. dumps: treatment with Eneasi- an enzymatic biochemical activator complex
No full textCharacterisation of River Po particles by sedimentation field-flow fractionation coupled to GFAAS and ICP-MS
No full textA procedure for elemental composition determination of water-borne rixer particles (Po River) on both sizefractionated
and unfractionated submicron particles (0.1 1 lam) by graphite furnace atomic absorption spectroscopy
tGFAAS) and inductively coupled plasma-mass spectrometry (ICP-MSI is reported. Sample fractionation was
performed using sedimentation field-flow fractionation (SdFFF). The distribution of relative mass vs. particle size was
determined using UV detection. Fractions were collected over a narrow size range for scanning electron microscopy.
With this combination of techniques the mass, elemental composition, and shape distributions can be ~btained across
the size spectrum of the sample.
The size distributions of the major elements (A1, Fe) were determined by coupling both GFAAS and ICP MS
techniques to the SdFFF. The procedure was validated using a reference chty sample. Satisfactory agreement was
found between both the GFAAS and ICP MS aluminium signal and the UV detector signal. Some discrepancies were
observed in the Fe/AI ratios when comparing GFAAS and ICP MS. Thus further investigation is in order to fully
assess the role of SdFFF-ICP MS and SdFFF-GFAAS techniques for elemental characterisation of aquatic colloids.
Both GFAAS and ICP MS signals unambiguously indicate a significantly higher Fe content in the lower size range,
which is consistent with previous investigations.
Trace element levels in unfractionated Po River particles, determined by both GFAAS and ICP MS, show good
agreement. The high levels of Cu, Pb, Cr and Cd found associated with the colloidal particles underlines the signiticance
of the environmental role played by the suspended matter in rivers in both highly industrialised and intensively
cultivated areas
Experimental approaches for size-based metal speciation in rivers
No full textA review of the different methodologies employed to fractionate and characterize riverine suspended particulate
matter is presented. The importance of size-based metal speciation is underlined and the possibility of studying
it by the Sedimentation Field Flow Fractionation (SdFFF) technique is illustrated. The studies on the metal
load in river Suspended Particulate Matter (SPM) performed over the last ten years are critically reviewed
focusing on the different methods employed to collect, concentrate and size-fractionate samples. The fact that
there is no homogeneity in methods and data collection in this field is underlined. Among the different
fractionation techniques, Field Flow Fractionation (FFF) methodologies have proved to be a good approach to
study the role of SPM in metal load and transport. The possibility of studying size-based metal speciation using
the SdFFF technique is presented and the importance of metal speciation in rivers is underlined
EFFECTS OF THERMAL TREATMENTS AND OF CARRIER GAS MOISTURE ON THE POROUS POLYMER ADSORPTION PROPERTIES
No full textEFFECTS OF THERMAL TREATMENTS AND OF CARRIER GAS MOISTURE ON THE POROUS POLYMER ADSORPTION PROPERTIE
SPLITT cell separation of polydisperse suspended particles of environmental interest
No full textSplit-flow thin (SPLITT) cell, continuous two-way separation has been investigated for the separation of particulate matter of environmental interest. The basic SPLITT cell operation equation is reconsidered and the effects of the particle porosity, dimension, shape and density are discussed. Suspensions of porous silica, kaolin and montmorillonite in the submicron to micron diameter range were separated by means of the SPLITT cell with appropriate carrier composition. The results of the separations were checked by use of optical and scanning-electron microscopy and are discussed with reference to the basic equations for SPLITT cell working conditions. Optimum results were in agreement with the theoretical expressions as long as the pertinent SPLITT separation expression was employed. Quantitative results from SPLITT cell separations were compared with those obtained by the classical static sedimentation procedure; the agreement and discrepancies found are discussed
Influence of thermal pre-treatment on adsorption properties of porous polymer air samplers
No full textA study of the influence of thermal pre-treatment on the adsorption properties of various polymers (Porapak Q, Chromosorb 101, 102 and Tenax GC) is reported. The linear extrapolation of ln Vg against 1/T is examined in the context of the preheating temperatures. At higher temperatures, chromosorb 101 and 102 show a polarity increase, while Porapak Q shows a decrease. For styrene copolymers, the function ln Vg versus 1/T is fully linear only when the pre-heating temperature coincides with the temperature limit suggested by the manufacturers. Pre-heating temperatures between 200 and 300°C do not influence the adsorption characteristics of Tenax GC, for which the function ln Vg, versus 1/T is always linear. © 1983
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