1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
Browse
2 results
Search Results
Item Photocatalytic Degradation of Diclofenac using Different Mixed Oxide Catalysts(National Institute of Technology Karnataka, Surathkal, 2021) Mugunthan, E.; Saidutta, M. B.; Jagadeeshbabu, P. E.Elimination of pharmaceutical compounds and their metabolites from the aquatic systems has been a tedious process. The various photocatalytic process using TiO2 as semiconductor photocatalysts has enormous potential to cope with the challenges in the removal of pharmaceutical compounds. However, the TiO2-mediated photocatalytic water treatment suffers from the faster rate of recombination and wide bandgap energy corresponding to UV light. Coupling with other semiconductor oxides has reportedly reduced the recombination rate and drawbacks of the short excitation range. In the present work, the degradation of diclofenac in the photocatalytic system is carried out by using different mixed oxide catalysts prepared by hydrothermal method. The heterojunction mixed oxide catalysts can improve the photocatalytic activity by reducing the recombination rate of charge carriers and enhanced the excitation ability of the coupled catalysts in the visible light region. A series of mixed oxide catalysts were prepared with different molar concentrations of TiO2-SnO2, TiO2-WO3, ZnO-WO3 and TiO2-CdS and were characterized by XRD, TEM, BET surface area and UV spectrophotometric analyses. Initially, the performance of a series of TiO2-SnO2 mixed oxide catalysts was studied. The photocatalytic efficiency was analyzed in the degradation of diclofenac and the degradation kinetics were extensively investigated. The influence of various parameters such as initial drug concentration, pH and catalyst loading was also studied. The TiO2-WO3 mixed oxide catalysts were tested for its photocatalytic efficiency and the results suggested that the series of prepared mixed oxide catalysts exhibited better catalytic activity than the pure TiO2 under visible light irradiation. The diclofenac degradation using ZnO-WO3 heterojunction catalysts under visible light irradiation were evaluated and the synthesized ZnO-WO3 mixed oxide catalyst produced better performance than the individual components of the photocatalyst. Degradation of diclofenac using TiO2-CdS mixed oxides shows that the presence of the optimum amount of CdS in the coupled heterostructure exhibited higher photocatalytic efficiency under visible light. Comparing the performance of all the mixed oxide catalysts, TiO2-WO3 mixed oxide catalysts displayed the best catalytic activity among others under optimum operating conditions. Degradation experiment data of all the mixed oxide catalysts well fitted to pseudo-first-order reaction and the rate constants were determined. The photocatalytic degradation of diclofenac was greatly affected by initial pH, catalyst dosage and initial diclofenac concentration. The degradation was highly effective under the acidic condition for all the prepared coupled photocatalysts and the surface charge property of photocatalysts played an important role in the adsorption of drug diclofenac onto the catalyst surface. The degradation reaction mechanisms of the mixed oxide catalysts were studied and it must be noted that the hydroxyl radicals and photogenerated holes were the main active species in the diclofenac degradation process. The charge transfer between heterostructure photocatalysts has been confirmed by the photoluminescence studies. LCMS was used to analyze the various degradation products formed during the irradiation and it is revealed that several MS peaks corresponding to partially degraded products were observed during the course of photocatalytic degradation of diclofenac. Mainly these observed degradation products were preceded by the attack of •OH radicals and hydroxylation reactions which was further followed by decarboxylation, dechlorination and C-N cleavage reactions.Item Study of new chitosan based derivatives for removal of heavy metals from wastewater(National Institute of Technology Karnataka, Surathkal, 2017) K, Balakrishna Prabhu; Saidutta, M. B.; Isloor, Arun MHeavy metals (such as Cu, Pb and Cr) are harmful contributors to pollution of fresh and marine aquatic bodies. Adsorption is a very efficient and popular technique used in wastewater treatment. Chitosan is a biopolymer derived from chitin, an abundantly occurring natural polymer in nature. As an adsorbent, use of chitosan in natural form is constrained by its inferior mechanical, chemical and swelling properties. In this study, four new chitosan derivatives were synthesized by grafting four ligands on chitosan with a view of improving its characteristics. Each ligand had a single pyrazole ring with two additional nitrogen atoms which are potential binding sites for heavy metal sequestration. Batch studies were carried out to determine the optimum pH for adsorption, the most fitting isotherm, the most fitting kinetic model and the relevant thermodynamic parameters. The maximum monolayer adsorption capacities obtained were 63.5 mg/g for Cr (VI), 91.7 mg/g for Pb (II) and 45.6 mg/g for Cu (II). The probable mode of adsorption was chemisorption. The pseudo-second order model fitted experimental kinetic data very well. The FTIR study revealed that amine, imine and hydroxyl groups participated in metal sequestration. The major decrease in the swelling property of the prepared derivatives makes them a promising choice for applications in practical water treatment contacting equipment. Polysulfone membranes blended with the new chitosan derivative CTSL-2 were prepared. The hydroxyl, amine and the imine functional groups present in the additive evidently increased the hydrophilicity of the surface of the blended membranes as confirmed by contact angle measurements. The contact angle of the blended membrane having 2 wt % additive was 62.55 ± 1 as compared to 70.01 ± 1 for neat polysulfone membrane. The blended membranes also showed a significant improvement in maximum pure water flux (351 Lm-2h-1 against 24 Lm-2h-1 of neat membrane). The BSA anti-fouling test exhibited improved anti-fouling characteristic of blended membrane (FRR of 56%). In the metal rejection study, the maximum rejections observed were 36%, 29% and 61% respectively for the three metals Pb (II), Cu (II) and Cr (VI). Overall, the incorporation of additive in polysulfone membranes demonstrated significant improvement in the permeation properties investigated.