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.

The contribution of the Finite Volume Point Dilution Method to the determination of solute mass flux in an alluvial aquifer.

Groundwater represents one of the most important resources of the world and it is essential to prevent its pollution and to consider remediation intervention in case of contamination. According to the scientific community the characterization and the management of the contaminated sites have to be performed in terms of contaminant fluxes and considering their spatial and temporal evolution. One of the most suitable approach to determine the spatial distribution of pollutant and to quantify contaminant fluxes in groundwater is using control panels. The determination of contaminant mass flux, requires measurement of contaminant concentration in the moving phase (water) and velocity/flux of the groundwater. In this Master Thesis a new solute flux mass measurement approach, based on an integrated control panel type methodology combined with the Finite Volume Point Dilution Method (FVPDM), for the monitoring of transient groundwater fluxes, is proposed. Moreover a new adsorption passive sampler, which allow to capture the variation of solute concentration with time, is designed. The present work contributes to the development of this approach on three key points. First, the ability of the FVPDM to monitor transient groundwater fluxes was verified during a step drawdown test at the experimental site of Hermalle Sous Argentau (Belgium). The results showed that this method can be used, with optimal results, to follow transient groundwater fluxes. Moreover, it resulted that performing FVPDM, in several piezometers, during a pumping test allows to determine the different flow rates and flow regimes that can occurs in the various parts of an aquifer. The second field test aiming to determine the representativity of a control panel for measuring mass flus in groundwater underlined that wrong evaluations of Darcy fluxes and discharge surfaces can determine an incorrect estimation of mass fluxes and that this technique has to be used with precaution. Thus, a detailed geological and hydrogeological characterization must be conducted, before applying this technique. Finally, the third outcome of this work concerned laboratory experiments. The test conducted on several type of adsorption material (Oasis HLB cartridge, TDS-ORGANOSORB 10 and TDS-ORGANOSORB 10-AA), in order to determine the optimum medium to dimension the passive sampler, highlighted the necessity to find a material with a reversible adsorption tendency to completely satisfy the request of the new passive sampling technique.

Mechanochemical solvent-free synthesis of Sn-β Zeolite and Ag2O/TiO2 catalysts

Preparations of heterogeneous catalysts are usually complex processes that involve several procedures as precipitation, crystallization and hydrothermal treatments. This processes are really dependent by the operative conditions such as temperature, pH, concentration etc. Hence the resulting product is extremely affected by any possible variations in these parameters making this synthesis really fragile. With the aim to improve these operations has been decided to exploit a new possible strong environment-respectful process by mechanochemical treatment, which permits to carry out solvent free-solvent synthesis exploiting the Mixer Mill MM400 (Retsch) in order to have reproducible results. Two different systems have been studied in this kind of synthesis: a tin β -zeolite tested in a H-trasnfer reaction of cyclohexanone and a silver on titania catalyst used in the fluorination of 2,2 dimethyl glucaric acid. Each catalyst has been characterized by different techniques in order to understand the transformations involved in the mechanochemical treatment.

Synthesis of Metal-Binding Ligand-Containing Copolymers, Nanoparticles and Blends

In this thesis we developed three copper-containing systems. Copper shows intriguing abilities in photocatalysis, however, one of the major limitations of many copper complexes is that photochemical properties might be quenched in solution caused by π-interactions between solvent and solute, due to Jahn-Teller distortion in the excited state. As such, we herein seek to synthesise copper heteroleptic complexes that will subsequently be nanoprecipitated with a polymer. This will allow the polymer to encase the complex and prevent the solvent-induced quenching. Subsequently, the preparation of blends of polymer with the aforementioned copper complexes, at different weight ratios is sought. The preparation of the blend is particularly interesting as the catalytic properties are anticipated to be inferior on account of the low surface area. However, owing to the polymer matrix better, mechanical properties are anticipated. The blends can combine the mechanical properties of the polymer and the luminescence of the complex, with the advantage that the polymer matrix can also prevent quenching from oxygen. As final task, we developed a copper-containing monomer. The synthesis of a monomer that contains copper and can be excited under ultraviolet (UV) light is particularly interesting.