Faculty Publications
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Item Selenium Biosorption and Recovery by Marine Aspergillus terreus in an Upflow Bioreactor(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2016) Raja, C.P.; Jacob, J.M.; Mohan Balakrishnan, R.M.Experiments were conducted to study the Selenium (Se) biosorption and recovery by marine Aspergillus terreus in an upflow bioreactor for a period of 8 days. The Se tolerance of the marine fungus was initially confirmed by visual and microscopic observations that evinced intact fungal cells in an Se-amended medium with sparse changes in the spore texture and cellular number by the seventh day of biosorption studies in the upflow bioreactor. Further, the effect of pH and contact time on the percentage of Se biosorption, in an upflow bioreactor containing fungal pellets, was investigated. It was analyzed that pH ranges of 6-7 and a contact time of 5 days resulted in 85-87% biosorption of Se by the fungal biomass. The interaction of the fungus with the induced Se stress in the medium was monitored regularly for studying the uptake of the metalloid and the possible biosynthesis of Se nanoparticles. Analyses using ultraviolet visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) studies revealed the formation of crystalline Se nanocrystals with an average diameter of 500 nm on the fungal cell wall. Fourier transform infrared (FTIR) spectroscopic analysis indicated the possible involvement of fungal protein groups that aid the binding of the biosorbed Se nanoparticles on to the fungal cell wall. © 2015 American Society of Civil Engineers.Item Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection(Elsevier B.V., 2017) Uddandarao, U.; Mohan Balakrishnan, R.M.Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II–IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2 + and Mn2 + in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV–Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem. © 2016 Elsevier B.V.Item Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri(Academic Press, 2018) Manirethan, V.; Raval, K.; Rajan, R.; Thaira, H.; Mohan Balakrishnan, R.M.The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. © 2018 Elsevier LtdItem Biosynthesis of cobalt oxide nanoparticles using endophytic fungus Aspergillus nidulans(Academic Press, 2018) Vijayanandan, A.S.; Mohan Balakrishnan, R.M.Metallic oxide nanoparticles have profound applications in electrochemical devices, supercapacitors, biosensors and batteries. Though four fungi were isolated from Nothapodytes foetida, Aspergillus nidulans was found to be suitable for synthesis of cobalt oxide nanoparticles, as it has proficient tolerance towards metal under study. The broth containing precursor solution and organism Aspergillus nidulans had changed from pink to orange indicating the formation of nanoparticles. Characterization by x-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray analysis (EDX) confirmed the formation of spinel cobalt oxide nanoparticles at an average size of 20.29 nm in spherical shape with sulfur-bearing proteins acting as a capping agent for the synthesized nanoparticles. The nanoparticles could be applied in energy storage, as a specific capacitance of 389 F/g showed competence. The study was a greener attempt to synthesize cobalt oxide nanoparticles using endophytic fungus. © 2018 Elsevier LtdItem Decolorization of Reactive Blue 220 aqueous solution using fungal synthesized Co3O4 nanoparticles(IWA Publishing 12 Caxton Street London SW1H 0QS, 2019) 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 mol-1. © IWA Publishing 2019Item Solar assisted photocatalytic degradation of organic pollutants in the presence of biogenic fluorescent ZnS nanocolloids(Elsevier Ltd, 2019) Uddandarao, P.; Hingnekar, T.A.; Mohan Balakrishnan, R.M.; Rene, E.R.The main aim of this study was to ascertain the photocatalytic degradation of organic pollutants present in aqueous phase using fluorescent biogenic ZnS nanocolloids produced from an endophytic fungus Aspergillus flavus. The degradation studies were carried out using different organic pollutants such as methyl violet (MV), 2,4-dichlorophenoxyacetic acid (2,4-D) and paracetamol (PARA) for 120 min, 270 min and 240 min, respectively, at pH varying from 3.0 to 11.0. The results from this study indicate that the degradation efficiency of ZnS nanocolloids for MV, 2,4-D and PARA were 87%, 33% and 51%, respectively, at the optimum concentration of 100 mg/L of the tested organic pollutants. At different time intervals, the samples were analyzed for their chemical oxygen demand (COD) and total organic carbon (TOC) contents. The reduction of COD and TOC were 78% and 74% for MV at 120 min; 55.5% and 57.2% for 2,4-D at 270 min and 47.6% and 44.5% for PARA at 240 min, respectively. The degradation pathway was determined based on the mass spectrum and the intermediates formed; in addition, the interaction between organic pollutants and nanocolloids was also elucidated based on atomic force microscopy (AFM) and fluorescence spectrum. © 2019 Elsevier LtdItem Photocatalytic degradation of p-nitrophenol using biologically synthesized ZnO nanoparticles(Springer Science and Business Media Deutschland GmbH, 2021) Kadam, V.V.; Shanmugam, S.D.; JagadeeshBabu, J.; Mohan Balakrishnan, R.M.The present work deals with the photocatalytic degradation of p-nitrophenol as it is a United States Environmental Protection Agency-listed priority pollutant and has adverse environmental and health effects. To eradicate the detrimental environmental impact of p-nitrophenol, the biologically synthesized ZnO nanoparticles were used as a photocatalyst. The degradation of p-nitrophenol was confirmed by decreasing the absorbance value at a characteristic wavelength of 317 nm using the UV-vis spectrophotometer. Reaction parameters such as ZnO photocatalyst concentration of 0.1 g/L at pH 11 in the presence of H2O2 (5 mM) were found to be optimum conditions for p-nitrophenol degradation. The photocatalytic degradation was slowly enhanced in the presence of H2O2 as an electron acceptor. The kinetics of nitrophenol degradation was studied, which follows the pseudo-first-order reaction. The photocatalytic degradation of p-nitrophenol was characterized by using total organic carbon, chemical oxygen demand, and high-performance liquid chromatography analyses. This method is found to be effective as it is environmentally friendly, free of toxic chemicals. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Zinc-decorated barium oxide nanorods for the effective sunlight-induced catalytic degradation of Irgalite violet dye(Springer Science and Business Media Deutschland GmbH, 2023) Ilango, I.; Susanna, D.; Gabriella, R.; Mohan Balakrishnan, R.M.; JagadeeshBabu, J.Simple and facile fabrication of barium oxide (BaO) and zinc-decorated barium oxide (ZnBaO) nanocatalysts was accomplished through a co-precipitation technique. Irgalite violet (IV) dye was subjected to sunlight-induced catalytic degradation using novel catalyst ZnBaO nanorods. The synthesized nanocatalysts were subjected to various analytical techniques, including FE-SEM/EDX, XRD and FTIR, for their comprehensive characterization. X-ray diffraction confirmed the crystallinity of BaO and ZnBaO nanocatalysts. The FE-SEM image of the ZnBaO nanocatalyst revealed the occurrence of distinct nanorods with a mean size of 22.5 nm possessing an aspect ratio of 4.95. A characteristic UV absorbance peak was observed at 310 nm for BaO and 380 nm for ZnBaO nanocatalysts. The substitution of Zn to BaO led to a favorable decrease in the band gap energy from 5.315 eV (BaO) to 2.6 eV (ZnBaO). The synthesized BaO and ZnBaO nanocatalysts were used in parametric studies by varying catalyst dosage, irradiation time, pH and initial dye concentration. The ZnBaO nanorods showed a maximum degradation efficiency of 99.9% at pH 11 with a catalyst dosage of 40 mg/50 mL containing 5 mg/L dye concentration. The recyclability studies showed that the ZnBaO nanorods could serve as a potential catalyst for degrading dyes. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Functionalization of β-cyclodextrin onto NiFe2O4 nanoparticles for the removal of ketoprofen and diclofenac from the aqueous solutions(Institute for Ionics, 2024) Ilango, I.; Mohan Balakrishnan, R.M.; Visvanathan, C.; Bui, X.-T.; Velusamy, P.A new β-CD functionalized nickel ferrite nanocomposite was synthesized and used to remove pharmaceutical drugs, such as ketoprofen (KF) and diclofenac (DCF). The co-precipitation approach was utilised to synthesize nickel ferrite (NFO) nanoparticles, which were then functionalized with TEOS to form NFO@SiO2; β-cyclodextrin was then functionalized using GPTMS as an interface to form NFO@SiO2@β-CD. FTIR, ZD, FE-SEM, EDX, TGA/DTG, VSM, BET, zeta potential and particle size analysis were then used to characterise the nanocomposites. The NFO@SiO2@β-CD has an average diameter of 109.1 nm, superparamagnetic behaviour, a mesoporous surface and a specific surface of 20.78 m2/g. The functionalized NFO@SiO2@ β-CD nanocomposite removed 94% of diclofenac in 5 min and 80% of ketoprofen in 360 min with the adsorption capacities of 8.46 and 0.54 mg/g, respectively. The obtained experimental datum for both the pollutants was fitted in kinetic and isotherm models, with the pseudo-second-order kinetic model and Freundlich adsorption isotherm showing the best fit with the highest regression of R 2 = 0.99. The nanocomposite was regenerated using 0.1 M NaOH and recycled for about four consecutive cycles in which the reduction in the removal efficiency of ketoprofen and diclofenac was observed to be 51.36% and 64%, respectively. These results suggested that the NFO@SiO2@β-CD nanocomposite could be used specifically to target the low-concentrated pharmaceutical pollutants. Graphical Abstract: Schematic representation of Functionalization of β-Cyclodextrin onto NiFe2O4 nanoparticles for the removal of ketoprofen and diclofenac from the aqueous solutions. [Figure not available: see fulltext.] © 2023, The Author(s) under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University.