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dc.contributor.authorSubbaramaiah, V.-
dc.date.accessioned2025-06-30T12:46:44Z-
dc.date.available2025-06-30T12:46:44Z-
dc.date.issued2013-06-
dc.identifier.urihttp://localhost:8081/jspui/handle/123456789/17341-
dc.description.abstractNitrogenous aromatic compounds such as pyridine, 2-picoline, aniline, etc. containing wastewater have gained more attention because of their toxicity and frequency in industrial wastewater. Pyridine is one of the parent chemical from which a series of chemicals are manufactured. It is used as a solvent in paint and rubber preparation, as an intermediate in making insecticides, pharmaceuticals and herbicides for agricultural applications. Picoline is used as a solvent in the synthesis of pharmaceuticals, resins, dyes and rubber accelerators. It is also used as an intennediate in the manufacture of insecticides, water proofing agents, niacin and niacinamide. Typical concentration of pyridine and its associated compounds in wastewater may vary in the range of 20-300 mg/i. Exposure to pyridine causes harmful effects on liver, kidneys, immune systems and reproductive functions; and it is a potential carcinogen. Aniline is widely used as a raw material in the production of plastic, paint, pesticides, dyes, etc. Aniline easily reacts in the blood to convert hemoglobin to methemoglobin, thereby preventing oxygen uptake resulting in cyanosis. Chronic exposure may cause decreased appetite, anemia, weight loss, nervous system effects, bone liver and kidney marrow damage. It is most frequently found in effluents from agrochemical, petrochemical, pesticide, dyestuff and pharmaceutical industries. United States environmental protection agency (USEPA) has listed pyridine and aniline in its priority list of pollutants. Various treatment methods including biological, physicochemical and thermal incineration can be used for removal of nitrogenous compounds. In addition, advanced oxidation processes (AOPs) such as catalytic wet air oxidation, ozonation, photocatalysis, catalytic wet peroxidation (CWPO), etc. have received wide attention in recent years for removal of refractory pollutants. Most of the AOPs rely on generation of hydroxyl radicals so as to oxidize majority of the complex chemicals present in the wastewater. However, each method has its own limitations and disadvantages. Catalytic wet peroxidation (CWPO) is well known process that can be used for the degradation organic pollutants with the help of homogeneous or heterogeneous catalysts using hydrogen peroxide as an oxidant under mild conditions with low energy consumption. it' Heterogeneous catalyst has recently gained more research efforts. Santa Barbara amorphous-15 (SBA-15) has received rapid attention in material science and catalysis since its inception, due to its straight forward synthesis route, narrow and controllable pore size, high surface area, high thermal stability, etc. SBA-15 itself does not show substantial catalytic activity unless appropriate active metal species are impregnated inside SBA-15. A review of literature shows that Cu and Ce impregnated SBA-15 have never been used for CWPO of any recalcitrant compound. Moreover, most of previous researchers didn't report on reusability of the catalysts which is very essential considering the high cost of SBA-15. Also, CWPO of wastewater containing individual or binary nitrogenous compounds like pyridine, picoline and aniline has not been reported earlier. The present study has been undertaken with following aims and objectives: To synthesize Cu and Ce impregnated SBA-15 material using triblock copolymer as a structural agent. • To perform physico-chemical characterization of the catalysts by N2 adsorption-desorption, temperature programmed reduction (H2-TPR), temperature programmed desorption (NH3-TPD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), UV-visible diffused reflectance spectroscopy (UV- DRS), and thermogravimetric analyzer (TGA) methods. • To evaluate catalytic activity of Cu/SBA-15 and Ce/SBA-15 for the individual or binary oxidation of pyridine, picoline and aniline using hydrogen peroxide as an oxidant. • To optimize the operating parameters such as catalyst dose, stoichiometric ratio of I-I202/compound, initial concentration and temperature for the CWPO of compounds present in aqueous solution. • To determine kinetic and thermodynamic parameters and operation cost of the CWPO process • To explore catalytic stability and recyclability of the synthesized catalyst and to investigate possible reaction mechanism of pyridine, picoline and aniline h CWPO process. • To utilize Taguchi's method for the optimization and interaction of parameters during CWPO of solutions containing binary nitrogenous compounds. I V In this study, Cu and Ce were impregnated on SBA-15 framework (Cu/SBA-15 and Ce/SBA-15), with different loading of Cu and Ce (5% Cu/SBA-15, 10% Cu/SBA-15, and 20% Cu/SBA-15; 2.5% Ce/SBA-15, 5% Ce/SBA-15 and 10% Ce/SBA-15). All the catalysts (Cu/SBA-15 and Ce/SBA-15) exhibited international union of pure and applied chemistry (IUPAC) type IV-isotherms nature indicating mesoporous structure having uniform pore size. As predictable, the presence of metals lead to corresponding decrease in BET surface area, pore volume, and pore diameter in metal-containing SBA-15. Ce/SBA-15 showed highly ordered meso-structure with pore diameter70-100 A and pore volume0.025 cm3/g. Cu/SBA-15 could be reduced at lower temperature, two main reduction peaks were observed at —560 and —640 K, first peak assigned to reduction of Cu2 to Cu, and the second peak assigned to subsequent reduction of Cu to Cu'. CuISBA- 15 catalyst exhibited all types of acid sites such as weak, medium and strong acid sites, however, only weak acid sites were observed in Ce/SBA-15. Cu loading on SBA-15 enhanced the surface acidity by the generation of Lewis acid sites. Morphology of all catalyst exhibited (SBA-15, Ce/SBA-15 and Cu/SBA-15) fiber type of structure. Cu and Ce were well dispersed on SBA-15 surface without pore blocking. Ce/SBA-15 and Cu/SBA-15 showed high thermal stability. CWPO was carried out by Cu/SBA-15 and Ce/SBA-15 catalyst for the oxidation of pyridine, picoline and aniline using 1-1202 as an oxidant at atmospheric pressure. Degree of mineralization of compounds was determined by total organic carbon (TOC) removal. Maximum oxidation of pyridine and picoline by Ce/SBA-15 and Cu/SBA-15 $ catalysts was achieved at natural p1-I. whereas maxinuim removal of aniline was attained at p1-I 4 for both types of catalysts. Temperature was found to be one of the important variables during the CWPO process. An increase in temperature was found to increase the mineralization of the nitrogenous compounds. The reaction kinetic data were generally best-represented by multi-step pseudo-first-order kinetic model. At optimum condition, 97% pyridine removal, 98% picoline and 96% aniline removal was achieved using Cu/SBA-15 as a catalyst. For Ce/SBA-15, 86%, 95% and 92% removal was observed for pyridine, picoline and aniline, respectively. Cu/SBA-15 showed better performance for the degradation of pyridine, picoline and aniline as compared to Ce/SBA-15. During CWPO process, excess H202 is added into the reaction. Redox processes (Cu -* Cu 2+ 3+ and Ce 4+ Ce ) taking place at the active sites inside the pores of SBA-15 generate peroxy radical (00H) and hydroxyl radical (OH). * These hydroxyl radicals have high oxidation potential and they react with organic compounds non-selectively converting them into many intermediates. Hydroxyl radical further reacts with intermediate compounds converting them into less toxic compounds such as CO2, H20. To understand the degradation mechanism clearly, intermediate compounds were identified and were found to be in good agreement with those reported in open literature. Based on this study, a mineralization mechanism of nitrogenous compounds by CWPO process was proposed. Catalyst reusability was investigated by wrapping the catalyst in PTFE membrane filter and using it for the oxidation of pyridirie, picoline and aniline. It showed stable performance without regeneration, with minimum leaching. Cu and Ce leaching was also measured after each cycle. Cu leaching was always less than 210 p.g/l while Ce leaching was always less than 400 p.g/l, which are within the permissible heavy metal concentration for discharge of wastewater in India. Estimation of treatment cost is an important aspect for implementation of any research work on plant scale. A rough economic analysis, in terms of estimation of the operating costs (in S/m3 wastewater), was done. The operation cost calculated included cost of chemical reagents for SBA- 15 synthesis, cost of reagents for CWPO process and the cost of energy. Operating cost of CWPO process was found to be higher for Ce/SBA- 15 catalyst as compared to that for Cu/SBA- 15. Binary component oxidation (pyridine-picoline and pyridine-aniline) was carried out by CuISBA-15 and Ce/SBA-15 catalysts using statistical optimization technique. Effect of significant parameters such as p1-I, catalyst dose, hydrogen peroxide dose and temperature were studied at three level using Taguchi's orthogonal array (OA) layout of L9 (34)• Temperature was found to be the most influential parameter followed by p1-I during CWPO of binary mixtures. Interaction between the parameters was found to be significant. For binary compound oxidation, the removal efficiencies were found to be in the range of -85-99% for all the systems studied. Cu/SBA-15 proved to be better catalyst as it promoted faster reaction rates, had higher 4.1 selectivity towards nitrogenous compounds degradation, good reusability and less operation cost.en_US
dc.description.sponsorshipINDIAN INSTITUTE OF TECHNOLOGY ROORKEEen_US
dc.language.isoenen_US
dc.publisherI I T ROORKEEen_US
dc.subjectNitrogenous Aromaticen_US
dc.subjectPharmaceuticalen_US
dc.subjectResinsen_US
dc.subjectRubber Preparationen_US
dc.titleCATALYTIC WET PEROXIDATION OF NITROGENOUS AROMATIC COMPOUNDSen_US
dc.typeOtheren_US
Appears in Collections:MASTERS' THESES (Chemical Engg)

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