Determinazione della performance di membrane composite per la purificazione di gas

In questo elaborato vengono presentati i risultati di una attività sperimentale incentrata sulla ricerca di membrane a matrice mista per la separazione di gas da miscele. In questo lavoro viene descritta la preparazione di membrane in polisulfone e membrane a matrice mista polisulfone con ZIF-8 a quattro diversi caricamenti percentuali, PSf+ZIF-8 2%, 4%, 8% e 16%. Vengono anche esposti i risultati delle prove di caratterizzazione di tali membrane. E' stato condotto un esame attraverso microscopia elettronica a scansione (SEM) sulla sezione e sulla superficie delle cinque membrane. Sono esposti i risultati dei test di permeazione condotti attraverso un permeometro a volume costante. Le prove sono state fatte per tutte le membrane con sei diversi gas penetranti (H2, He, O2, CO2, CH4 e N2) a tre diverse temperature (35°C, 50°C e 65°C) ottenendo i valori dei coefficienti di permeabilità, solubilità e diffusività. Sono state calcolate le selettività ideali per ogni coppia di gas per tutte le membrane e le energie di attivazione. Sono stati fatti paragoni con i risultati di letteratura e ricercate correlazioni predittive per le proprietà di trasporto delle membrane in funzione di diversi parametri.

Solvent regeneration of activated carbon mixed-matrix membranes for the removal of micropollutants from wastewater

The constantly increasing demand of clean water has become challenging to deal with over the past years, water being an ever more precious resource. In recent times, the existing wastewater treatments had to be integrated with new steps, due to the detection of so-called organic micropollutants (OMPs). These compounds have been shown to adversely affect the environment and possibly human health, even when found in very low concentrations. In order to remove OMPs from wastewater, one possible technique is a hybrid process combining filtration and adsorption. In this work, polyethersulfone multi-channel mixed-matrix membranes with embedded powdered activated carbon (PAC) were tested to investigate the membrane’s adsorption and desorption performance. Micropollutants retention was analyzed using the pharmaceutical compounds diclofenac (DCF), paracetamol (PARA) and carbamazepine (CBZ) in filtration mode, combining the PAC adsorption process with the membrane’s ultrafiltration. Desorption performance was studied through solvent regeneration, using seven different solvents: pure water, pure ethanol, mixture of ethanol and water in different concentration, sodium hydroxide and a mixture of ethanol and sodium hydroxide. Regeneration experiments were carried out in forward-flushing. At first regeneration efficiency was investigated using a single-solute solution (diclofenac in water). The mixture Ethanol/Water (50:50) was found to be the most efficient with long-term retention of 59% after one desorption cycle. It was, therefore, later tested on a membrane previously loaded with a multi-solute solution. Three desorption cycles were performed after which, retention (after 30 min) reached values of 87% for PARA and 72% for CBZ and 55% for DCF, which indicates decent regenerability. A morphological analysis on the membranes confirmed that, in any case, the regeneration cycles did not affect either the membranes’ structure, or the content and distribution of PAC in the matrix.