Faculty Publications
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Item Reusable floating polymer nanocomposite photocatalyst for the efficient treatment of dye wastewaters under scaled-up conditions in batch and recirculation modes(John Wiley and Sons Ltd vgorayska@wiley.com Southern Gate Chichester, West Sussex PO19 8SQ, 2019) Das, S.; Mahalingam, H.BACKGROUND: In the last decade, research on floating photocatalysts has increased rapidly with polymer substrates being a popular choice. However, most of the published work is on very small volumes and there is very little work on scale-up of such systems. RESULTS: Polystyrene–titanium dioxide nanocomposite floating films were prepared using a facile solvent casting method and tested for the photocatalytic degradation of four different dyes under UV irradiation. The prepared film was characterised by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES) and profilometry. Scale-up studies were done in batch mode under optimised conditions, and for the larger reactor volume, the effect of recirculation was studied. Complete decolourisation of the model dye (Remazol Turquoise Blue) was observed within 80 min in the scaled-up batch process. In the recirculation mode, for a much larger volume of the dye solution, around 75% decolourisation in 6 h was observed. The reusability of the photocatalytic film was tested, and the results promise a minimum decolourisation efficiency of around 70%. Finally, total organic carbon (TOC) and liquid chromatography mass spectrometry (LC-MS) analysis were used to assess the degradation of the dye. The maximum TOC reduction observed was around 25% possibly due to the complex nature of the dye used in this study. The intermediate products of degradation were identified, and a tentative mechanism is suggested. CONCLUSION: This work demonstrates the recirculation aspects of the photocatalytic reactor under the scaled-up conditions for a complex dye. The prepared film showed excellent stability with satisfactory wastewater decontamination under UV irradiation even after repeated use. © 2019 Society of Chemical Industry. © 2019 Society of Chemical IndustryItem Novel immobilized ternary photocatalytic polymer film based airlift reactor for efficient degradation of complex phthalocyanine dye wastewater(Elsevier B.V., 2020) Das, S.; Mahalingam, H.Reduced graphene oxide (rGO) as well as graphitic carbon nitride (g-C3N4) catalysts were synthesized and a physical admixture of rGO and g-C3N4 along with TiO2 in the ratio of 1:1:1 by weight was immobilized in a polystyrene film using the facile solvent casting method. An internal loop airlift reactor with a working volume of 1.2 litres incorporating the prepared polymer-based photocatalytic film was designed and tested for the photocatalytic degradation of remazol turquoise blue dye synthetic wastewater. The reactor parameters affecting the photocatalytic activity such as airflow rate and Di/Do (ratio of draft tube diameter to outer tube diameter) were evaluated. The successful operation of the reactor obtained using the ternary immobilized catalyst mixture film gave 92.25% total organic carbon reduction and 94% decolourization within 140 min, compared to 91% decolourization by the slurry form within 40 min. Complete and quicker decolourization of the dye was also demonstrated under the influence of O3 or H2O2. The immobilized catalyst was successfully reused four times. The ternary catalyst admixture employed in this work and the unique design of the photocatalytic reactor helps to increase the degradation rate of toxic textile effluents thus making it suitable for larger scales of treatment. © 2019 Elsevier B.V.Item Highly efficient solar light-driven BiOX (X=Br/Cl/I) and BiOY heterojunction (Y=Br/Cl) nano photocatalysts in suspended and immobilised forms for malachite green dye wastewater treatment(Springer Science and Business Media Deutschland GmbH, 2023) Mishra, S.; Manjunatha, M.; Mahalingam, H.A novel BiOY (Y = Br/Cl) heterojunction nanocatalyst was synthesised chemically and compared with three different BiOX (X = Br/Cl/I) nanocatalysts as well as a physical admixture of BiOBr/BiOCl catalysts in the photocatalytic degradation of malachite green dye wastewater under solar irradiation in both suspended and immobilised forms using polysulfone as the substrate. Catalyst characterisation was done by a particle size analyser, SEM/EDX, XRD, FTIR, and DRS. In the suspended form, BiOBr showed 100% degradation within 70 min, BiOCl showed 99.3%, and BiOI showed 11.2% degradation within 120 min, and it is found to follow pseudo-first-order kinetics. In the immobilised form, BiOBr showed 89.1%, and BiOCl showed 83.4% degradation within 180 min under sunlight. The degradation measured by TOC reduction for these catalysts in suspended form was 67.4%, 57%, and 40%, affirming BiOBr as the best among these catalysts. The performance of the immobilised chemically synthesised BiOY and physical admixture catalysts were 88% and 14%, respectively. The enhanced activity in the chemically synthesised immobilised BiOBr/Cl catalyst can be attributed to the effective charge separation at the heterojunction interface. These photocatalysts are very active under solar light and hence suitable for the efficient degradation of other recalcitrant organic contaminants. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Item Utilization of torrefied rice husk and deoiled cashew nut shell cake biomass waste for removal of hazardous Reactive Violet 5 dye(Springer, 2025) Suriyakumar, S.; Mahalingam, H.; Sudhakar, R.D.Torrefied biomass is a renewable, sustainable, carbon–neutral fuel that is replacing coal in many areas. This organic source has increased surface area and porosity, making it an effective adsorbent. Only a very few works have been reported in the literature on exploring the use of torrefied biomass and its ash as inexpensive adsorbents for the removal of dyes. In this work, rice husk and deoiled cashew nut shell cake in its torrefied and ash forms have been employed as adsorbents for Reactive Violet 5 dye removal. Thus, four adsorbents were synthesized and characterized by BET, SEM, XRD, and FTIR. The optimum parameters for maximum dye removal efficiency were 0.8 g/L adsorbent dosage, pH 2.0, and 40-min contact time for batch experiments using 100 mL of 10 ppm dye solution. The maximum adsorption capacity of torrefied rice husk, torrefied deoiled cashew nut shell cake, torrefied rice husk ash, and torrefied deoiled cashew nut shell cake ash were 108.58 mg/g, 88.38 mg/g, 68.0 mg/g, and 29.97 mg/g, respectively. Torrefied rice husk exhibited the best fit with the Freundlich isotherm, whereas other adsorbents fitted best with the Langmuir isotherm. The non-linear pseudo-second-order model gave the best fit. The intraparticle diffusion model showed that adsorption involves multiple diffusion stages. The thermodynamic parameters indicated that the process was spontaneous, feasible, and exothermic. These eco-friendly materials can be efficiently used in dye removal, thus paving the way for torrefied biomass or its ash to be used as low-cost adsorbents for large-scale wastewater treatment. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.