Browsing by Subject "Titania"

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Open Access
A unified framework of response surface methodology and coalescing of Firefly with random forest algorithm for enhancing nano-phytoremediation efficiency of chromium via in vitro regenerated aquatic macrophyte coontail (Ceratophyllum demersum L.)
(Springer, 2024-06-11) Ali, Seyid Amjad; Gümüş, Numan Emre; Aasim, Muhammad
Nano-phytoremediation is a novel green technique to remove toxic pollutants from the environment. In vitro regenerated Ceratophyllum demersum (L.) plants were exposed to different concentrations of chromium (Cr) and exposure times in the presence of titania nanoparticles (TiO2NPs). Response surface methodology was used for multiple statistical analyses like regression analysis and optimizing plots. The supplementation of NPs significantly impacted Cr in water and Cr removal (%), whereas NP × exposure time (T) statistically regulated all output parameters. The Firefly metaheuristic algorithm and the random forest (Firefly-RF) machine learning algorithms were coalesced to optimize hyperparameters, aiming to achieve the highest level of accuracy in predicted models. The R2 scores were recorded as 0.956 for Cr in water, 0.987 for Cr in the plant, 0.992 for bioconcentration factor (BCF), and 0.957 for Cr removal through the Firefly-RF model. The findings illustrated superior prediction performance from the random forest models when compared to the response surface methodology. The conclusion is drawn that metal-based nanoparticles (NPs) can effectively be utilized for nano-phytoremediation of heavy metals. This study has uncovered a promising outlook for the utilization of nanoparticles in nano-phytoremediation. This study is expected to pave the way for future research on the topic, facilitating further exploration of various nanoparticles and a thorough evaluation of their potential in aquatic ecosystems.
Open Access
Enhanced photocatalytic NOx oxidation-storage over titania-metal oxide physical mixtures under UV and visible light
(2017-06) Çağlayan, Mustafa
Developing new technologies for the abatement of gaseous nitrogen oxides (NO, NO2, etc.) will still be one of the popular research fields; because fossil fuels (mainly coal and natural gas) will remain as the main energy sources for many decades to come. Although various technologies have been developed and implemented for DeNOx processes, alternative approaches are still open to discussion. Among these; Photocatalytic NOx Oxidation-Storage (PhoNOS) can offer promising opportunities to overcome this environmental challenge, as it can be utilized under ambient conditions with the help of UV and visible light irradiation. In this study; firstly, a new performance analysis method was developed other than the photonic efficiencies used in previous works. In this analysis method, a “DeNOx Index” was utilized. This index indicates the net change in total air pollution due to NOx species by comparing the relative contributions of NO and NO2 along with NO conversion and solid state NOx storage selectivity. This new method was first applied on previously studied TiO2-Al2O3 binary oxide samples (P2) synthesized by sol-gel co-precipitation method in comparison with commercially available Degussa P25 TiO2. Furthermore, TiO2-Al2O3 (P2) binary oxides were also physically/mechanically mixed with an alkaline earth oxide, CaO. Addition of CaO to P2 binary oxides decreased the NO conversion while enhancing the NOx storage. In order to alleviate the loss of NO conversion in CaO+P2 systems, physical mixtures of P25 TiO2 with two different commercial metal oxides (CaO and γ-Al2O3) were prepared and investigated. While CaO provides “higher alkalinity” (i.e. a desirable property for the solid state storage of acidic gaseous NOx species) than γ-Al2O3, mesoporous γ-Al2O3 can provide a higher porosity and specific surface area for the adsorption and storage of the oxidation products in the solid state. Considering these, binary or ternary mixtures with various compositions were prepared and catalytically tested under UV and Visible light irradiation. It was found out that the boosting effect of CaO on NOx storage is more significant than that of γ-Al2O3 for the binary oxides. On the other hand, it should be noted that ternary mixtures containing smaller amounts of titania with high performance can also be obtained by incorporating alumina into the mixture. In addition to these, performances of selected samples were studied under different humidity conditions and experimental durations. These experiments yielded interesting implications regarding NOx adsorption-oxidation phenomena on the investigated mixed oxide surfaces. Current findings indicate that further experiments are required to fully understand the fundamental mechanisms of photocatalytic NO oxidation and storage at the molecular level.
Open Access
NOx storage and reduction pathways on zirconia and titania functionalized binary and ternary oxides as NOx storage and reduction (NSR) systems
(Elsevier, 2014-08-01) Say, Z.; Tohumeken, M.; Ozensoy, E.
Binary and ternary oxide materials, ZrO2/TiO2 (ZT) and Al2O3/ZrO2/TiO2 (AZT), as well as their Ptfunctionalized counterparts were synthesized and characterized via XRD, Raman spectroscopy, BET, in situ FTIR and TPD techniques. In the ZT system, a strong interaction between TiO2 and ZrO2 domains at high temperatures (>973K) resulted in the formation of a low specific surface area (i.e. 26 m2/g at 973K) ZT material containing a highly ordered crystalline ZrTiO4 phase. Incorporation of Al2O3 in the AZT structure renders the material highly resilient toward crystallization and ordering. Alumina acts as a diffusion barrier in the AZT structure, preventing the formation of ZrTiO4 and leading to a high specific surface area (i.e. 264 m2/g at 973K). NOx adsorption on the AZT system was found to be significantly greater than that of ZT, due to almost ten-fold greater SSA of the former surface. While Pt incorporation did not alter the type of the adsorbed nitrate species, it significantly boosted the NOx adsorption on both Pt/ZT and Pt/AZT systems. Thermal stability of nitrates was higher on the AZT compared to ZT, most likely due to the defective structure and the presence of coordinatively unsaturated sites on the former surface. Pt sites also facilitate the decomposition of nitrates in the absence of an external reducing agent by shifting the decomposition temperatures to lower values. Presence of Pt also enhances partial/complete NOx reduction in the absence of an external reducing agent and the formation of N2 and N2O. In the presence of H2(g), reduction of surface nitrates was completed at 623K on ZT, while this was achieved at 723K for AZT. Nitrate reduction over Pt/ZT and Pt/AZT via H2(g) under mild conditions initially leads to conversion of bridging nitrates into monodentate nitrates/nitrites and the formation of surface OH and NHx functionalities. N2O(g) was also continuously generated during the reduction process as an intermediate/byproduct.
Open Access
The phase behavior and synthesis of mesostructured coupled semiconductor thin films : MESO-CdS-TiO2
(2009) Okur, Halil İbrahim
Mesostructured [Cd(H2O)4](NO3)2 - titania - P123 ((PEO)20(PPO)70(PEO)20, PEO = -OCH2CH2-, PPO = -OCH(CH3)CH2-) materials have been investigated by changing the [Cd(H2O)4](NO3)2 and titania content of the structures. This has been achieved by making thick samples by casting and thin film samples by spin coating of a butanol solution of [Cd(H2O)4](NO3)2, P123, nitric acid and Ti(OC4H9)4. The film samples are named as meso-xCd(II)-yTiO2, where x is the Cd(II)/P123 and y is TiO2/P123 mole ratios. Increasing the titania amount in the media has transformed the samples from LC-like to soft and then to rigid mesostructured materials. Changing the amount of [Cd(H2O)4](NO3)2 salt in the media only influenced the mesostructure, such that no change on the mechanical properties is observed. However, the synthesis of rigid mesostructured titania materials required controlled humidity. The rigid film samples were prepared first by spin coating and then by aging under a 50% humidity oven. The mesostructure remains stable upon H2S reaction, in the soft and rigid materials region. However, only rigid samples stand to removal of nitrates from the media that is important to keep the CdS nanoparticles stable in or on the pore walls of mesostructured film samples. The phase behavior of the meso-Cd(II)-TiO2, the structural properties of the meso-xCdS-yTiO2 samples, coordination and elimination of the NO3 - ions and the particle size of the CdS nanocrystallites were investigated using diffraction (XRD), spectroscopy (FT-IR, Raman and UV-Vis absorption, EDS) and microscopy (POM, SEM, and TEM) techniques.