Kandasamy Bhuvaneswari

This study developed an integrated strategy for outdoor photo-fermentative biohydrogen production by Rhodopseudomonas pentothenatexigens KKU-SN1/1 through low-cost medium optimization, repeated-batch operation, modular bioreactor simulation, and biomass valorization. A sequential experimental design combining one-factor-at-a-time screening and a 2 × 2 factorial experiment was conducted under high-temperature conditions (40 °C). Headspace gas purging was unnecessary, while trace element supplementation increased cumulative biohydrogen production 2.3-fold, from 601 to 1356 mL-H₂/L. The vinegar-yeast extract medium achieved a cumulative biohydrogen production of 1832 mL-H₂/L and reduced the estimated substrate cost by 93.6% compared with the conventional formulation. Outdoor repeated-batch operation with 20% fermentation broth reuse retained 83.9% of the Cycle 1 biohydrogen production in the subsequent cycle. Experimental outdoor data were then used to simulate a modular clustered bioreactor system, which projected quasi-continuous hydrogen production over 68 days, with average and peak production rates of 60 and 84 mL-H₂/L/d, respectively. The residual biomass also showed potential for valorization, containing 66% protein, 0.37% carotenoids, 1.11% bacteriochlorophyll, and 0.01% coenzyme Q10. The integrated approach combines low-cost medium formulation, repeated-batch operation, modular bioreactor simulation, and biomass valorization, providing a framework for resource-efficient outdoor biohydrogen production within a circular bioeconomy framework.

This study developed and evaluated an autonomous UV-C robotic disinfection system for computed tomography (CT) examination rooms, assessing microbial inactivation efficacy and operational safety using bacterial and viral surrogates. Staphylococcus aureus ATCC 25923 and bacteriophage were used as surrogates. The UV-C robot, equipped with eight low-pressure mercury lamps (36 W, 254 nm), was tested in two phases: localized irradiation at exposure times of 2-8 minutes and whole-room disinfection across five critical surfaces during a 21-minute operational cycle. Residual ozone concentrations were continuously monitored throughout all trials. The UV-C robot achieved complete inactivation of bacteriophages within 4 minutes and a greater than 99.99% reduction (>4 log) in Staphylococcus aureus colony counts at the same exposure time. Ozone concentrations remained consistently below occupational exposure limits (maximum 0.0043 ppm vs. OSHA limit of 0.1 ppm) throughout all trials. This study provides the first comprehensive evaluation of autonomous UV-C robotic disinfection specifically designed for CT suite geometries, integrating both efficacy testing and real-time safety monitoring. The findings establish evidence-based protocols for implementing UV-C robotic disinfection in diagnostic imaging departments and support the clinical feasibility of such systems as adjuncts to standard infection control practices.

Indoor air pollution poses a significant public health risk, particularly in urban areas, where PM2.5 and airborne contaminants contribute to respiratory diseases. In Thailand, including Chonburi Province, PM2.5 levels frequently exceed safety thresholds, underscoring the urgent need for effective mitigation strategies. To address this challenge, we developed a hybrid air purification system incorporating a bioplastic-based photocatalytic film of polylactic acid (PLA) embedded with titanium dioxide (TiO₂) nanoparticles. For optimization, PLA films were functionalized with varying TiO₂ concentrations and characterized using SEM, FTIR, TGDTA, and UV–Vis. spectroscopy. A 5 wt% TiO₂ loading was identified as optimal and further enhanced with silver (Ag) nanoparticles to boost photocatalytic efficiency. The Ag/TiO₂/PLA biofilm was fabricated via a compound pellet formulation process followed by blown film extrusion. Various compositions, with and without Ag, were systematically evaluated for photocatalytic performance. The novel customized hybrid air purifier developed in this study is designed to enhance indoor air purification efficiency by integrating Ag/TiO₂/PLA biofilms into a controlled oxidation system. The air purification efficacy of the developed biofilm was evaluated through a controlled study on Staphylococcus aureus (S. aureus) removal under different treatment conditions: control, adsorption, photolysis, and photocatalytic oxidation. The impact of light intensity on photocatalytic efficiency was also examined. The photocatalytic oxidation of S. aureus was subjected to the first-order kinetic evaluation through mathematical modeling. Results demonstrated that the Ag/TiO₂/PLA biofilm significantly enhances indoor air purification, providing a sustainable, scalable, and energy-efficient solution for microbial decontamination and pollutant removal. This innovative approach outperforms conventional adsorption, adsorption and photocatalytic oxidation systems, offering a promising pathway for improved indoor air quality.

Hydrothermally assisted magnetic ZnO/Carbon nanocomposites were prepared using the selective biowaste of pomelo orange. Initially, the carbon aerogel (CA) was prepared hydrothermally followed by a freeze-drying method. Furthermore, the iron oxide nanoparticles were deposited onto the surface of carbon using the co-precipitation method and we obtained magnetic carbon nanocomposite, i.e., Fe₃O₄/C (MNC). Moreover, the ZnO photocatalysts were incorporated onto the surface of MNC composites using a hydrothermal process, and we obtained ZnO/MNC composites. The ZnO/MNC (55%), ZnO/MNC (65%) and ZnO/MNC (75%) composites were prepared by a similar experimental method in order to change the weight ratio of ZnO NPs. Using a similar synthetic procedure, the standard ZnO and Fe₃O₄ nanoparticles were prepared without the addition of CA. The experimental results were derived from several analytical techniques, such as: X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and diffuse reflectance spectroscopy (DRS-UV). The synthesized carbon, ZnO, Fe₃O₄, ZnO/MNC (55%), ZnO/MNC (65%) and ZnO/MNC (75%) composites were examined through the photocatalytic degradation of methylene blue (MB) under visible-light irradiation (VLI). The obtained results revealed that the composites were more active than carbon, ZnO and Fe₃O₄. In particular, the ZnO/MNC (75%) composites showed more activity than the rest of the composites. Furthermore, the recycling abilities of the prepared ZnO/MNC (75%) composites were examined through the degradation of MB under identical conditions and the activity remained constant up to the fifth cycle. The synthetic procedure and practical applications proposed here can be used in chemical industries, biomedical fields and energy applications.

A simple wet impregnation approach had been used to the successful preparation of different weight percentages of strontium/niobium doped Er₂O₃ nanoparticles. The X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HR-TEM), Fourier transformed infrared spectroscopy (FTIR), and UV-visible (UV) spectroscopy was used to analyze the samples as they were prepared. With Sr and Nb doping at Er₂O₃ nanoparticles, the XRD patterns intensity was shifted, and its positioning was also shifted as weight percentages of doped were increased. Similarly, the lattice d spacing values were also decreased. According to HR-TEM images, Er₂O₃ seems to have a two-dimensional hexagonal nanoplate-like structure as well as being a few nm in size. The photocatalytic activities of pristine and Sr/Nb doped samples were evaluated against the methyl orange (MO) and rhodamine B (Rh B) dyes under UV-visible light irradiation. Within seventy-five minutes of UV-Visible light irradiation, the five-weight percentage of Sr doped Er₂O₃ nanoparticles shows significantly enhanced photocatalytic degradation efficiency against Rh B dye. The synergistic effect of the strong metal-support interaction between the Sr and Er₂O₃ nanoparticles could be attributed to the improved photocatalytic activity of the prepared samples. The cyclic stability and radical trapping experiments were also investigated against the same reaction conditions.

Photocatalytic dye degradation has received more attention as an affordable and effective way to treat the dye polluted water. In the present chapter, we are going to discuss; (i) the preparation and photophysical characterization of g-C3N4 intercalated ZnO\\Mg-Al LDH, a novel ternary nanocomposite, and (ii) its visible light photocatalytic degradation activity against the methylene blue dye. LDHs are 2D materials composed of “brucite-like” cationic layers where an inclusion of trivalent cations presents an overall positive charge to the nanosheets. g-C3N4 is one of the organic semiconductor photocatalyst which active for several types of reactions such as CO2 reduction, water splitting, and degradation because of its stable, non-toxic, and earth-abundant nature. Mainly, the development of numerous 2D g-C3N4 nanosheets has been extensively used in the field of photocatalyst. By the combination heterojunction with 2D/2D interface can effectively improve the photocatalytic activity. The nitrogen-rich g-C3N4 intercalated ZnO\\Mg-Al LDH ternary nanocomposite formation could follow the direct dye degradation process and results enhance the visible light absorption. The enhanced photocatalytic activity is mainly due to the improved charge separation rate and high number of photogenerated electrons. The large number of photogenerated electrons and high charge separation efficiency are effectively influence the dye degradation efficiency.