Materiali funzionalizzati per il recupero di composti ad alto valore aggiunto dalle acque reflue dei frantoi oleari ​

Over the past two years, global olive oil production has reached 2,73 million tons, mainly located in the Mediterranean area. The major issue of this activity is the production of high volumes of Oil mill wastewater (OMW) in a short period of time. OMW is characterized both by an acidic pH and by high concentrations of suspended solids and organic pollutants, which create an ecological and environmental issue. Reducing sugars determine important values of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD), exceeding the maximum concentrations established by D.Lgs n 152/2006 for wastewater. Whereas the presence of polyphenols reduces the degradation process of organic compounds promoted by microorganisms. The presence of the above-mentioned compounds makes it difficult to treat OMW by traditional oxidation methods. Hence, their removal from OMW before biological treatment is highly demanding. Additionally, since the antibacterial and antioxidant properties of polyphenols are already well known, a recovery strategy for further applications should be promoted. Based on these promises, this thesis work aims to develop, characterize and compare different microporous sorbents and their behaviour in removing reducing sugar, such as Glucose, and polyphenols (tyrosol and hydroxytyrosol, selected as representative compounds) from water. A SBA-15 was modified with (3-aminopropyl)-triethoxysilane (APTES) to specifically promote interactions towards -OH moieties of glucose and polyphenols and its absorption capacity was tested alongside traditional sorbents such as activated carbons and commercial primary and secondary amine (PSA). Several physicochemical techniques were used to characterize the modified SBA15, namely: thermogravimetric analysis and IR spectroscopy were used to obtain information about the surface, while X-ray diffraction and nitrogen gas adsorption were used to investigate morphology and pore size. To what concern removal tests, high-performance anion exchange chromatography (HPAEC) with pulsed amperometry detection (PAD) and a colorimetric procedure with Benedict’s reagent were used to determine glucose adsorption, while Folin-Ciocalteu colorimetric reaction was used for polyphenols. The adsorption properties were studied tuning various pH conditions and analyte concentrations. Although the three materials have different chemical-physical properties such as surface area or pore size, they are all applicable to the removal of these compounds. The results obtained showed that activated carbon, due to its high surface area of 1073 m2g-1, seems to be the most efficient in removing sugars and polyphenols. However, it lacks selectivity and its adsorption, which is completely irreversible, is on a long time scale. Instead, the commercial PSA, in addition to being the most expensive of the materials, only interacts with sugars, better at an acidic pH. In contrast, the functionalized material shows a good performance in the first hours with reversible adsorption, therefore its behaviour is studied. ​