Browsing by Author "Ranjith, Kugalur Shanmugam"
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Item Open Access Highly selective surface adsorption-induced efficient photodegradation of cationic dyes on hierarchical ZnO nanorod-decorated hydrolyzed PIM-1 nanofibrous webs(Elsevier, 2020) Ranjith, Kugalur Shanmugam; Satılmış, Bekir; Huh, Y. S.; Han, Y. -K.; Uyar, TamerSelectivity of catalysts toward harmful cationic pollutants in industrial wastewater remains challenging but is of crucial importance in environmental remediation processes. Here, we present a complex network of a hydrolyzed polymer of intrinsic microporosity (HPIM)-based electrospun nanofibrous web with surface functional decoration of ZnO nanorods (NRs) as a hierarchical platform for selective and rapid degradation of cationic dyes. Over a single species or binary mixtures, cationic dyes were selectively adsorbed by the HPIM surface, which then rapidly degraded under simultaneous photoirradiation through the ZnO NRs. Both HPIM and ZnO exhibited high electronegative surfaces, which induced the selectivity towards the cationic dyes and rapidly degraded the pollutants with the production of reactive oxygen species under photoirradiation. Further, as a free-standing web, the catalytic network could be easily separated and reused without any significant loss of catalytic activity after multiple cycles of use. The hierarchical platform of ZnO/HPIM-based heterostructures could be a promising catalytic template for selective degradation of synthetic dyes in mixed wastewater samples.Item Embargo Membrane based electrospun poly cyclodextrin nanofibers coated with ZnO nanograins by ALD Ultrafiltration blended photocatalysis for degradation of organic micropollutants(Elsevier, 2023-11-15) Ranjith, Kugalur Shanmugam; Yıldız, Zehra İrem; Khalily, Mohammad Aref; Huh, Y. S.; Han, Y.; Uyar, TamerMembranes with simultaneous selective adsorption functionality and excellent photocatalytic response have been proposed for water remediation, especially for treating textile and industrial wastewater. However, state-of-the-art membranes are easily fouled by pollutant adsorption that impacts their reusability. Here we report the development of a crosslinked electrospun poly-cyclodextrin (Poly-CD) nanofiber (NF) membrane coated by atomic layer deposition (ALD) with ZnO nanograins for the removal of pollutants from wastewater. The inherent high affinity of poly-CD NFs favored the selective adsorption of cationic impurities, and the reactive oxygen species produced by photoirradiation of the ZnO surface effectively degraded adsorbed contaminants. The NFMs has signifies that, even under the dark, they have a removal efficiency of around 80% which may be due to the high adsorption nature. Further, these NFM are highly reusable while decorating the ZnO nanograins on the NFM, which degraded the adsorbed pollutant and opened up the active site to further adsorb the dye molecule on the poly-CD surface. Under the static mode, the ZnO(100)@poly-CD NFM achieved the highest MB removal efficiency of 94.3%, followed by ZnO(25)@poly-CD, ZnO(200)@poly-CD, and poly-CD, which had removal rates of 91.3%, 87.7%, and 83.1%, respectively in 120 min of photoirradiation. Modulating the photocatalytic reaction in a flow channel, ZnO(100)@poly-CD nanofibrous membranes (NFMs) achieved 2.19-fold higher removal efficiencies (98.6% in 60 min) in a flow-through filtration system than under static conditions (a non-filtration method). Furthermore, the flow-through mode promoted the mass transfer of pollutants through NFMs, which increased reactive oxygen species production by inhibiting electron-hole recombination. Furthermore, the inherent self-cleaning function conferred by the photocatalytic activity of surface ZnO increased membrane structural stability and provided a faster removal rate.Item Open Access ZnO-TiO2 composites and ternary ZnTiO3 electrospun nanofibers: the influence of annealing on the photocatalytic response and reusable functionality(Royal Society of Chemistry, 2018) Ranjith, Kugalur Shanmugam; Uyar, TamerThe developments in environmental remediation based on the advanced oxidation processes of catalyst surfaces still endure the burden of the effective recombination of photoinduced charge carriers. The construction of defect band levels with heterostructural phases of catalytic nanostructures is a tenable strategy for separating photogenerated charge carriers and for minimizing carrier recombination. Herein, we explain an effective carrier separation rate with extended light absorption using electrospun ZnTi-based semiconducting nanofibers, which feature as composites and ternary form for their structural geometry. We explain the effective surface functionality with the design of the ZnO-TiO2 composite and ZnTiO3 as a function of the annealing temperature on electrospun fibers, and their commendable visible catalytic properties with the presence of defect states for degrading organic pollutants. The constructed ZnTiO3 in the form of nanofibers induced a narrow band gap of 3.01 eV as compared with its individual counterparts (ZnO (3.27 eV) and TiO2 (3.17 eV)). However, the composite functionality has an advantage in inducing discrete defect levels with the carbon impurities for favorable extended visible absorption with a similar morphological nature. Under visible irradiation, the ternary form of the nanofibers exhibited a photocatalytic degradation performance of around 72.45% and the composite fibers exhibited one of around 95.82% in 125 min due to the scrutinized function of the defect states that maximize the interfacial charge transfer between ZnO-C-TiO2 and delay the carrier recombination rate. The reliable mechanism behind the charge transfer of the photogenerated carriers was supported by trapping experiments of two different geometrical nanostructures on degrading organic pollutants. The interesting results obtained from the stability and reusability studies were that the ZnO-TiO2 composite nanofibers have a notably surface photocorrosive nature after catalytic reaction but the ternary ZnTiO3 form of the nanofibers has a stable surface stability with stable reusable catalytic functionality for up to 20 consecutive cycles. Constructing the nanostructures with tunable surface structural natures anticipates the broad possibilities in the photocatalytic realm for achieving improved visible catalytic responses with stable and reusable functionality over their single counterparts.