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Abbattimento dei polifenoli nelle acque reflue di frantoio
No full textLo smaltimento delle acque reflue di frantoio (ARF) costituisce un serio problema per l’agricoltura mediterranea. Lo spargimento delle ARF sui terreni agricoli è la soluzione comunemente adottata. Alla lunga, però, tale soluzione ha effetti negativi sulla fertilità del suolo a causa della attività fitotossica e antimicrobica delle ARF, dovuta principalmente al contenuto in polifenoli. Lo scopo di questo lavoro è di verificare la realizzabilità di un processo di attenuazione della tossicità delle ARF, basato sulla polimerizzazione dei polifenoli promossa dagli ossidi di ferro e manganese presenti nella frazione argillosa del suolo agricolo e sull’incorporazione dei polimeri risultanti nella matrice umica. Il trattamento è stato effettuato in reattori miscelati e aerati con il suolo in sospensione. I risultati ottenuti mostrano che il trattamento è efficace in termini di rimozione della componente polifenolica, ma non altrettanto in termini di rimozione della fitotossicità. L’identificazione e la rimozione di altri composti fitotossici è pertanto necessaria per l’applicabilità del processo proposto
Abiotic oxidation of catechol by soil metal oxides
No full textThe mechanism of catechol oxidation by soil metal oxides is investigated in a slurry reactor. This abiotic transformation is shown to consist in a three-step process. The first step is a heterogeneous reaction. Catechol undergoes fast, partial oxidation at the expenses of Fe and Mn oxides contained in the soil. In the second step, reduced Fe and Mn are released into the aqueous solution and immediately complexed by catechol. Metal-catecholate complexes are stable at the very low dissolved-oxygen concentration levels attained under nitrogen sparging. The third step is a homogenous reaction. The highly reactive intermediate produced by catechol partial oxidation initiates catechol polymerisation. Under nitrogen sparging, the polymerisation process ends rather rapidly, thus yielding only partial conversion of the phenol and producing low-molecular weight, water-soluble polymers. Further oxidation of the metal-catecholate complexes formed in the second step only occurs under air sparging. Thus, reactive intermediates are formed at much higher concentration levels than those attained when nearly no oxygen is present in solution. The polymerisation proceeds at a much faster rate until, under the experimental conditions adopted, complete catechol conversion is attained and high-molecular-weight, insoluble polymers are produced
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
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