Faculty Publications
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Item Decolorization of Reactive Blue 220 aqueous solution using fungal synthesized Co3O4 nanoparticles(IWA Publishing, 2020) Valappil, R.S.K.; Vijayanandan, A.S.; Mohan Balakrishnan, R.M.In this work, the photocatalytic activity of the biosynthesized cobalt oxide (Co3O4) nanoparticle (NP) is investigated using a textile dye Reactive Blue 220 (RB220) and decolorization % was monitored using UV–Vis spectrophotometer. The photocatalytic activity has been observed maximum at alkaline pH of 9, NP dosage of 250 mg/L, and reaction time of 270 min. In the presence of UV light irradiation, a maximum dye concentration of 10 mg/L was treated effectively using 150 mg/L NP, and 67% decolorization was achieved. Reaction kinetics has been analyzed, and the reaction followed the pseudo kinetics model with an activation energy of 484 kJ mol1. © 2020 IWA Publishing.Item Black titania: Turning the surface chemistry toward visible-light absorption, (photo) remediation of hazardous organics and H2 production(Elsevier, 2022) Prekodravac, J.; Giannakoudakis, D.A.; Colmenares, J.C.; Nair, N.; Vasiljević, B.; Kepić, D.Environmental protection and energy conversion by state-of-the-art photocatalysts emerge as imperative in pursuit for ideal, sustainable, and green oriented solutions. However, major drawbacks in broader application of one of the most promising semiconductor photocatalyst, titanium dioxide (TiO2), lie in the need for enhancing visible-light absorption and elevating the photocatalytic reactivity. Toward these directions, narrowing the material band gap and functionalization of the surface chemistry are among the most prosperous materials design approaches. As reported in earlier work, the surface structure engineering proved to be an encouraging approach to endow optical and electrical properties of the TiO2-based material. For the first time, the black powder of TiO2 with a disordered lattice and hydrogen surface doping was obtained through hydrogenation under high pressure and temperature, consequently leading to narrowing the optical band gap to 1.54eV. The presented chapter aims to reveal in-depth all the literature available information related to the black titania synthesis in addition of sharing in details its prosperous physicochemical properties. Feature information related to the photocatalytic activity of black TiO2 as well as of the most crucial features will also be provided. Finally, the chapter will conclude with the derived significant benefits of such material properties in photocatalytic treatment of organic pollutants and hydrogen production. © 2023 Elsevier Inc. All rights reserved.Item Advanced two-dimensional heterojunction photocatalysts of stoichiometric and non-stoichiometric bismuth oxyhalides with graphitic carbon nitride for sustainable energy and environmental applications(MDPI, 2021) Sridharan, K.; Shenoy, S.; Girish Kumar, S.G.; Terashima, C.; Fujishima, A.; Pitchaimuthu, S.Semiconductor-based photocatalysis has been identified as an encouraging approach for solving the two main challenging problems, viz., remedying our polluted environment and the generation of sustainable chemical energy. Stoichiometric and non-stoichiometric bismuth oxyhalides (BiOX and BixOyXz where X = Cl, Br, and I) are a relatively new class of semiconductors that have attracted considerable interest for photocatalysis applications due to attributes, viz., high stability, suitable band structure, modifiable energy bandgap and two-dimensional layered structure capable of generating an internal electric field. Recently, the construction of heterojunction photocatalysts, especially 2D/2D systems, has convincingly drawn momentous attention practicably owing to the productive influence of having two dissimilar layered semiconductors in face-to-face contact with each other. This review has systematically summarized the recent progress on the 2D/2D heterojunction constructed between BiOX/BixOyXz with graphitic carbon nitride (g-C3N4). The band structure of individual components, various fabrication methods, different strategies developed for improving the photocatalytic performance and their applications in the degradation of various organic contaminants, hydrogen (H2) evolution, carbon dioxide (CO2) reduction, nitrogen (N2) fixation and the organic synthesis of clean chemicals are summarized. The perspectives and plausible opportunities for developing high performance BiOX/BixOyXz-g-C3N4 heterojunction photocatalysts are also discussed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Item Photocatalytic Reactor Modelling Incorporating Computational Fluid Dynamics (CFD) for Water and Air purification: A Concise Review(Springer, 2025) Pandey, P.; K, K.P.; Mohanan, S.; Surenjan, A.Photocatalysis is a potent, advanced oxidation process that is effective in converting hazardous organic contaminants into non-toxic end products, offering a sustainable solution for water and air purification. The degradation process in photocatalysis is primarily influenced by several critical factors, including the illumination source, catalyst (either in the form of a slurry or immobilized), the pH range, and reactor design. Numerous costly, time-consuming, and difficult-to-perform experiment trials are conducted in the laboratory to optimize these operating parameters. Computational fluid dynamics (CFD) can be used to surpass these limitations. CFD has several advantages compared to experimentation, such as the capability to conduct many simulations, efficient use of time, cost-effectiveness, and the ability to simulate challenging conditions (such as high temperature, high pressure, or hazardous environments) in various reactor designs. Furthermore, CFD enables the analysis of spatial and temporal variation in independent variables, including velocity variation, reactant concentrations, and light intensity, which provides insights into the reactor. CFD is a popular tool in the field of reactor design and optimization. Its applications include the analysis of flow patterns, the modelling of mass transfer phenomena, and the scaling up of reactor systems to provide efficient designs. This review aims to provide insight into the basic photocatalytic process, the correlation between the photoreactor concept, reaction kinetics, irradiation scenarios (irradiation modelling) and the photocatalytic process parameters (pollution degradation conditions, pollutant type and concentration, different hydrodynamic modelling). © The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2025.Item An optimization study on microwave irradiated, decomposition of phenol in the presence of H2O2(2009) Prasannakumar, B.R.; Iyyaswami, I.; Murugesan, T.Background: Removal of phenol from industrial waste waters involves basic techniques namely extraction, biodegradation, photocatalytic degradation, etc. Among the available processes, the oxidation of phenols using H2O2 is a suitable alternative because of low cost and high oxidizing power. The application of an oxidation process for the decomposition of stable organic compounds in waste water leads to the total degradation of the compounds rather than transferring from one form to another. Since oxidation using Fenton's reagent ismore dependent on pH, in this present work it was proposed to use H2O2 coupled with microwave irradiation. The effects of initial phenol concentration, microwave power and the irradiation time on the amount of decomposition were studied. Results: In the present work experiments were conducted to estimate the percentage degradation of phenol for different initial concentrations of phenol (100, 200, 300, 400 and 500 mg L-1), microwave power input (180, 360, 540, 720 and 900 W) for different irradiation times. The kinetics of the degradation process were examined through experimental data and the decomposition rate follows first-order kinetics. Response surface methodology (RSM) was employed to optimize the design parameters for the present process. The interaction effect between the variables and the effect of interaction on to the responses (percentage decomposition of phenol) of the process was analysed and discussed in detail. The optimum values for the design parameters of the process were evaluated (initial phenol concentration 300 mg L-1, microwave power output 668 W, and microwave irradiation time 60 s, giving phenol degradation 82.39%) through RSM by differential approximation, and were confirmed by experiment. Conclusion: The decomposition of phenol was carried out using H2O2 coupled with microwave irradiation for different initial phenol concentrations, microwave power input and irradiation times. The phenol degradation process follows first-order kinetics. Optimization of the process was carried out through RSM by forming a design matrix using CCD. The optimized conditions were validated using experiments. The information is of value for the scale up of the oxidation process for the removal of phenol from wastewater. © 2008 Society of Chemical Industry.Item Solar light induced photocatalytic degradation of Reactive Blue 220 (RB-220) dye with highly efficient Ag@TiO2 core-shell nanoparticles: A comparison with UV photocatalysis(2014) Khanna, A.; Shetty K, K.Ag core-TiO2 shell (Ag@TiO2) structured nanoparticles with Ag to TiO2 molar ratio of 1:1.7 were synthesized using one pot synthesis method and post calcination was carried out at 450°C for 3h to convert it from amorphous to crystalline form. The Ag core and TiO2 shell formation was confirmed by TEM and AFM. The particle size analysis revealed the average size of Ag@TiO2 as approximately around 30nm. EDS spectra showed the presence of O, Ag, and Ti elements. The improvement in optical properties was proved by DRS which showed significant red shift by Ag core in visible region. Ag@TiO2 exhibited better photocatalytic activity as compared to Degussa P25-TiO2, synthesized TiO2, and the Ag doped TiO2 photocatalysts under UV and solar light irradiation for degradation of Reactive Blue 220 (RB-220) dye. Higher rate of photocatalysis of RB-220 with Ag@TiO2 was obtained under solar light irradiation as compared to UV light irradiation, confirming the capability of the catalyst to absorb both UV and visible light. The kinetics of degradation of dye was found to follow modified Langmuir Hinshelwood (L-H) kinetic model. Ag@TiO2 can be recycled without much decline in the efficacy. Ag@TiO2 has been found to be the effective photocatalyst for degradation of water contaminated with azo dyes under both UV and solar light irradiations. © 2013 Elsevier Ltd.Item Solar light-driven photocatalytic degradation of Anthraquinone dye-contaminated water by engineered Ag@TiO2 core–shell nanoparticles(Bellwether Publishing, Ltd., 2015) Khanna, A.; Shetty K, V.K.Abstract: The Ag core–TiO2 shell (Ag@TiO2) nanoparticles were synthesized by one-pot synthesis method followed by calcination and characterized using X-ray diffraction and transmission electron microscopy. The Ag@TiO2 core–shell-structured nanocatalyst was evaluated for its photocatalytic activity towards the degradation of Acid Blue-129 (AB-129), an Anthraquinone dye under solar light irradiations. The nanoparticles were engineered for efficient photocatalytic degradation of AB-129 by varying the parameters such as catalyst composition, calcination temperature, and calcination time. The catalyst composition with Ag to Ti molar ratio of 1:1.7, calcination temperature of 450°C, and time of 3 h were found to be the optimum for the efficient photocatalytic degradation of AB-129. The efficacy of Ag@TiO2 was compared with commercial TiO2, synthesized nano-TiO2, and Ag-doped TiO2 for the photocatalytic degradation of AB-129 and enhanced dye degradation was obtained with Ag@TiO2. This enhanced activity of Ag@TiO2 may be attributed to the trapping of conduction band electrons in Ag core and subsequent discharge on supply of air. Solar photocatalytic degradation of AB-129 dye using Ag@TiO2 followed Langmuir–Hinshelwood kinetics. Ag@TiO2 can be exploited as an efficient catalyst for the degradation of dye and textile industry wastewater. © 2014, © 2014 Balaban Desalination Publications. All rights reserved.Item Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO2 Layers through Atomic-Layer Deposition(Wiley-VCH Verlag info@wiley-vch.de, 2015) Sridharan, K.; Jang, E.; Park, Y.M.; Park, T.J.Atomic-layer deposition (ALD) is a thin-film growth technology that allows for conformal growth of thin films with atomic-level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO2 layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO2 layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO2 nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO2 coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO2 coatings (?0.75-1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO2, and the photocatalytic activity to that of pure ZnO. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Novel RGO-ZnWO4-Fe3O4 nanocomposite as high performance visible light photocatalyst(Royal Society of Chemistry, 2016) Mohamed, M.M.J.; Shenoy, U.S.; Bhat, D.K.A novel RGO-ZnWO4-Fe3O4 nanocomposite is synthesized by a microwave irradiation method and its catalytic activity for the photo degradation of Methylene Blue (MB) is investigated. The prepared nanocomposites are characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible spectroscopy. The visible light photocatalytic activities of the prepared nanocomposites are investigated using a MB dye solution. It is noteworthy that RGO-ZnWO4-Fe3O4 nanocomposites exhibited relatively high photocatalytic activity compared to ZnWO4-RGO and pure ZnWO4 on MB in aqueous solution. This enhanced rate is due to the ability of the graphene in the RGO-ZnWO4-Fe3O4 composite to support carrier exploitation efficiently by tolerating the photo excited electron-hole pairs and thus encouraging oxidative degradation of the pollutants. This work could be extended to other organic pollutants as well and could provide new insights into ternary nanocomposites as high performance photocatalysts and their application in waste water treatment. © 2016 The Royal Society of Chemistry.Item Solar light mediated photocatalytic degradation of phenol using Ag core - TiO2 shell (Ag@TiO2) nanoparticles in batch and fluidized bed reactor(Elsevier Ltd, 2016) Shet, A.; Shetty K, K.V.Ag@TiO2 nanoparticles were synthesised using one pot method followed by calcination at 450 °C for 3 h and were tested for their photocatalytic efficacy in degradation of phenol both in free and immobilized form under solar light irradiation through batch experiments. Ag@TiO2 nanoparticles were found to be effective in solar photocatalytic degradation of phenol. The effect of factors such as pH, initial phenol concentration and catalyst loading on phenol degradation were evaluated and these factors were found to influence the process efficiency. The optimum values of these factors were determined to maximize the phenol degradation. The efficacy of nanoparticles immobilized on cellulose acetate film was inferior to that of free nanoparticles in solar photocatalysis due to light penetration problem and diffusional limitations. The performance of fluidized bed photocatalytic reactor operated under batch with recycle mode for solar photocatalysis of phenol with immobilized Ag@TiO2 nanoparticles was evaluated for large scale application. The performance was found to be dependent on catalyst loading and the optimum is governed by active catalyst sites and light penetration limitations. The photocatalytic degradation of phenol by Ag@TiO2 nanoparticles was only marginally influenced by the presence of small traces of chloride ions. Ag@TiO2 showed a better efficacy as solar photocatalyst than as UV photocatalyst in degradation of phenol. Solar light irradiation is recommended because solar energy, a readily available form of energy can be effectively harnessed for energy efficient, environment friendly and cost effective process. The kinetics of degradation of phenol was found to follow the nth order kinetics with order, n = 2.19 for solar photocatalysis. © 2016 Elsevier Ltd.