Bismuth Tungstate Photocatalysis for N-Nitrosamines Removal from Amine Washing Wastewater

The most practical way of reducing industrial carbon dioxide (CO2) emissions, which is the main contributor to global warming, is post-combustion CO2 capture using amine solvents. A large variety of degradation products are generated during the CO2 capture process. This is mostly due to amines reacting irreversibly with CO2, and other oxygenated compounds in the flue gas. Amine degradation products poses threat to human health and marine life. Amine degradation products like N-nitrosamines are carcinogenic and mutagenic. The formation of carcinogenic and mutagenic N-nitrosamines can obstruct the technology's industrial application. To reduce the impact on human health and marine life, identifying and treating carcinogenic, and mutagenic compounds like N-nitrosamines is extremely important. Photocatalysis, an Advance oxidation process (AOP) which uses UV light source and semiconductor catalysts is studied for degradation of organic and inorganic pollutants. Photocatalysis is used in this study for treating N-Nitrosodiethylamine (NDEA) with strong reactive hydroxyl radicals generated by UV/Visible light source and semiconductor photocatalyst bismuth tungstate (Bi2WO6). The semiconductor photocatalyst Bi2WO6 was studied in pure form and surface modified forms. Surface modification was done by altering hydrothermal synthesis temperature, hard template replication technique with templates such as porous silica KIT-6, transition metal impregnation like silver (Ag), Iron (Fe), Copper (Cu), Lanthanum (La). Various catalyst characterization techniques like Nitrogen adsorption–desorption measurements (BET method) used to determine the surface area, pore size and pore volume, X- ray diffraction (XRD) to determine the crystalline size of catalyst, UV-vis spectroscopy to analyze the light absorption property and band gap energy of the catalyst, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) to determine the surface morphology and composition of catalyst are used. The operational variables for photocatalytic degradation of NDEA are pH of the solution, catalyst dosing (gram/litre), metal impregnation (%). Stat ease Design expert software Version 13 was used for designing the experiments using a Face centered-central composite design (FC-CCD) in Response Surface Methodology (RSM). Different regression models have been used to fit the experimental responses and evaluated using F- statistic and p- value in Analysis of variance (ANOVA). By removing insignificant terms based on p-value, it was assessed that the quadratic model fits best for experimental responses with all metal impregnated catalyst. Impact of operational variable on photocatalytic degradation was analyzed using three dimensional interactive plots. For photocatalytic degradation of NDEA, pH of the solution is highly significant compared to other variables like catalyst dosing and metal impregnation. Optimization studies for maximum degradation of NDEA with operational variables were studies using RSM. The average degradation efficiency of NDEA is 89.2 % for Fe- Bi2WO6, 87.4% Ag- Bi2WO6, 86.9% for La- Bi2WO6 and 85% for Cu- Bi2WO6

Name thesis:degree_name

Master of Applied Science (MASc)

Level thesis:degree_level

Master's

Discipline thesis:degree_discipline

Engineering - Process Systems

Grantor dc:publisher

Faculty of Graduate Studies and Research, University of Regina

Year dc:date.issued

2021

Author dc:creator

• Maddineni, Vasu

Advisor dc:contributor.advisor

• Ibrahim, Hussameldin

Committee members dc:contributor.committeemember

• Henni, Amr
• Shirif, Ezeddin

Language dc:language.iso

en

DOI

https://doi.org/10.82465/4566

OAI identifier oai:identifier

oai:uregina.scholaris.ca:10294/14975