The development of membrane technology for gas separation processes evolved with the fabrication of so-called mixed matrix membranes (MMMs) as an alternative to neat polymers, in order to improve the overall membrane effectiveness. Once the mixed matrix membranes are used, the gas separation properties of the porous materials used as fillers are combined with the economical processability and desirable mechanical properties of polymer matrix. Mixed mesoporous silica/polymer membranes with high CO 2 and O 2 permeability and selectivity were designed and prepared by incorporating MCM-41 particles into a polymer matrix. Ordered mesoporous silica MCM-41 with high surface confirmed by BET analysis were obtained and functionalized with amino groups. In order to obtain the mixed membranes, the mesoporous silica was embedded into the polysulfone matrix (PSF). Flat mixed matrix membranes with 5, 10, and 20 wt% MCM-41 and MCM-41-NH 2 loadings have been prepared via the polymer solution casting method. The phase's interactions were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and thermogravimetry (TGA), while the gas separation performances were evaluated using pure gases (CO 2 , O 2 , N 2 ). The MCM-41/PSF and MCM-41-NH 2 /PSF membranes exhibited increased permeabilities for O 2 (between 1.2 and 1.7 Barrer) and CO 2 (between 4.2 and 8.1 Barrer) compared to the neat membrane (0.8 Barrer). The loss of selectivity for the O 2 /N 2 (between 6 and 8%) and CO 2 /N 2 (between 25 and 41%) gas pairs was not significant compared with the pure membrane (8 and 39%, respectively). The MCM-41/PSF membranes were more selective for CO 2 /N 2 than the O 2 /N 2 pair, due to the size difference between CO 2 and N 2 molecules and to the condensability of CO 2 , leading to an increase of solubility. Stronger interactions have been noticed for MCM-41-NH 2 /PSF membranes due to the amino groups, with the selectivity increasing for both gas pairs compared with the MCM-41/PSF membranes.

In order to meet the increasing energy demand and to decrease the dependency on coal, environmentally friendly methods for fly ash utilization are required. In this respect, the priority is to identify the fly ash properties and to consider its potential as raw material in the obtaining of high-value materials. The physico-chemical and structural characteristics of the fly ash coming from various worldwide power plants are briefly presented. The fly ash was sampled from power plants where the combustion of lignite and hard coal in pulverized-fuel boilers (PC) and circulating fluidized bed (CFB) boilers was applied. The fly ash has high silica content. Due to this, the fly ash can be considered a potential raw material for the synthesis of nanoporous materials, such as zeolites or mesoporous silica. The samples with the highest content of SiO2 can be used to obtain mesoporous silica materials, such as MCM-41 or SBA-15. The resulting mesoporous silica can be used for removing/capture of CO2 from emissions or for wastewater treatment. The synthesis of various porous materials using wastes would allow a high level of recycling for a sustainable society with low environmental impact.

The pyrolysis can be an attractive way to reduce the plastic waste and, in the same time, to obtain alternative conventional fuels. In this respect, four polymers (low-density polyethylene, high-density polyethylene, propylene and polystyrene) were used in the pyrolysis process. The experiments were carried out by using an in-house plant, which allowed a maximum test temperature of 450 �C. The product oil and the derived gas from the pyrolysis process were evaluated using different techniques, such as elemental analysis (EA), calorimetry, gas chromatography (GC), gas chromatography coupled with mass spectrometry (GC-MS). Furthermore, for a comparative study two catalysts, zeolite and lignite, were also used for the pyrolysis process, in order to observe their influences on the final products. The higher heating value obtained for the oil was in the 40.17-45.35 MJ/kg range, acceptable for the use of these oil as an alternative fuel for diesel engine. Also, the sulphur content from the obtained oil does not cause environment problems, being lower than the allowed limits (10 mg/L). In addition, the pyrolysis derived gas was rich in hydrocarbons, conducting to a high calorific value, in the 73.42 - 121.18 MJ/kg range.

The study aims to promote clean energy technologies that ensure the recycling and recovery of waste, namely the sewage sludge (SS), by converting it into products (e.g. oil, gas) with added value, contributing thus to reducing the negative impact on environment and health. An experimental setup was proposed in order to achieve the pyrolysis process, by varying the heating rate, (5�C/min, 10�C/min and 50�C/min). The resulted products, namely i) char - SSPyChar, ii) oil - SSPyOil and iii) gas - SSPyGas, were investigated in terms of elemental content, high heat value (HHV), low heat value (LHV) and emission factor (EF). The pyrolysis oils obtained with lower heating rate, 5�C/min and 10 �C/min, presented higher HHV, in comparison with the oils obtained at 50 �C/min, which were rich in water. These oils can have a negative impact on the environment, through their combustion due to their high content of N (6 wt%) and S (1.2 wt%), responsible for the formation of NOx and SOx. Pyrolysis gas revealed in its composition high contents of hydrocarbons (C1-C6), carbon dioxide (CO2) and hydrogen (H2). The highest HHV was obtained by using 5�C/min increment, namely 33.81 MJ/m3. Also, the pyrolysis gases had comparable energy values with natural gas, biogas or gases resulted from the plastic pyrolysis.

In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.