Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Siirt Üniversitesi, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2021
Tezin Dili: Türkçe
Öğrenci: EBRU BATUR
Danışman: Sinan Kutluay
Özet:In this study, the performance of activated carbon derived from de-oiled black cumin (Nigella Sativa L.) waste biomass through chemical activation with zinc chloride (ZnCI2) using response surface methodology (RSM), in both volatile organic compounds (VOCs) removal and photovoltaic applications was evaluated. To this end, in the first stage, activated carbon production process was optimized using central composite design (CCD), an approach of RSM, based on factors such as activation time (30-60 min), activation temperature (400-600 °C) and impregnation ratio (black cumin waste/ZnCI2, 50-150% by weight), and iodine number as the targeted response. Furthermore, these important factors that affect activated carbon production were defined by an analysis of variance (ANOVA). For production of activated carbon, an activation time of 57 min, activation temperature of 550 °C and impregnation ratio of 105% were found to be optimum values and a high iodine number of 1055 mg/g was achieved under these conditions. Surface properties of activated carbon produced under optimum conditions were characterized by various analytical techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) surface area. The results showed that a significant amount of microporosity (53.93%) and mesoporosity (46.07%) occurred in the optimal activated carbon. Moreover, optimal activated carbon exhibited a highly porous structure with a specific surface area (SBET) of 1213.32 m2/g, total pore volume of 0.89 cm3/g and micropore surface area of 787.65 m2/g. Many industrial processes produce VOC pollutants that occur as multi-component systems. Therefore, investigation of comparative and competitive adsorption of VOCs is of practical and scientific importance. In this regard, in the second stage, comparative and competitive adsorption behaviours of benzene, toluene and xylene (BTX) vapor targeted as VOCs using optimal activated carbon in single-component, binary-component and ternary-component systems were elucidated. Compared to single-component system, in binary-component and ternary-component systems, depending on the initial concentration, BTX vapor exhibited highly different competitive adsorption capacity. Adsorption capacity of each component in multi-component systems is much less than that in single-component system. In addition, dynamic adsorption capacity of X-vapor onto optimal activated carbon in multi-component systems is higher than that of both B-vapor and T-vapor. These results may be attributed to the fact that adsorption selectivity of optimal activated carbon for X-vapor is higher than that for T-vapor and B-vapor. Also, the state of X-vapor > T-vapor > B-vapor observed in adsorption capacities in single-component, binary-component and ternary-component systems, can be explained by the competitive dominance of BTX vapor, binding energies of physisorption, molecular weights and methyl groups. The findings of this application will help to understand comparative and competitive adsorption behaviour between different VOC pollutants with respect to a specific adsorbent. Dynamic adsorption mechanism of BTX vapor onto optimal activated carbon was explained in detail by applying various kinetic and isothermal models to the experimental adsorption data. The BTX vapor removal processes that follow the reaction-based pseudo-first-order (PFO) kinetic model indicate the physical adsorption mechanism. In addition, based on evaluations of diffusion-based intra-particle diffusion and Boyd's film-diffusion kinetic models, it was concluded that the BTX vapor adsorption process was affected by the film-diffusion resistance (first stage) as well as the intra-particle diffusion resistance (after the BTX molecules diffuse through the gas film) until reaching equilibrium. Besides, overall mass transfer and film mass transfer factors were found to be higher than internal diffusion factor ([kLa]g > [kLa]f > [kLa]d) in BTX vapor adsorption, which showed that global mass transfer and film mass transfer were more effective than internal diffusion. In a cadmium sulfide (CdS) based solar cell, the CdS semiconductor plays a very important role as a sensitizer. It is of great importance to increase, with the support of activated carbon, photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications. Furthermore, activated carbon is included in the electrodes of photovoltaic devices as electro-conductive additives, and support for active materials. For these reasons, in the final stage, instead of undoped-doped CdS semiconductor materials that are frequently used in the literature, activated carbon supported CdS (CdS/activated carbon) and molybdenum (Mo)-doped CdS/activated carbon, lanthanum (La)-doped CdS/activated carbon and manganese (Mn)-doped CdS/activated carbon semiconductor materials of different concentrations (0.33%, 1% and 3% by weight) were produced through chemical precipitation using optimal activated carbon. The main objective of this application in the thesis was to determine how energy conversion efficiencies of undoped and doped CdS semiconductor materials varied in the presence of optimal activated carbon support material and interpret such observed effect in the light of literature. Produced pure CdS/activated carbon, Mo-doped CdS/activated carbon, La-doped CdS/activated carbon and Mn-doped CdS/activated carbon semiconductor materials were characterized by incident photon-to-current efficiency (IPCE), SEM, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) measurements. The studies carried out under this application clearly revealed the ability to increase photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications with the support of activated carbon. This study presents a new strategy to clarify comparative and competitive dynamic adsorption mechanism in single, binary and ternary-component systems of BTX vapor targeted as VOCs using biowaste-based activated carbon through RSM optimization and to increase solar cell efficiency of semiconductor-based solar cell structures derived by using activated carbon supported CdS semiconductor materials.