Heterogeneous Photocatalytic Degradation of N-Nitrosodiethylamine in Wash Water Unit of Carbon Capture Plants Using Tungsten Trioxide Based Catalysts PDF Download

Author: Obed Yeboah Boakye
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

Book Description
Post combustion carbon capture, a promising technology for capturing the superabundant CO2 produced by various industries has received much research and industrial attention. The use of amines for this capture process comes with its own disadvantage in that it degrades into other products some of which are harmful to the ecosystem upon its release into the environment. Chief of these degradation products are the mutagenic and carcinogenic nitrosamines which have received much research attention in both carbon capture processes and wastewater treatment plant processes. Several treatment methods such as biological methods, activated carbon, UV in conjunction with ozone or reverse osmosis and other catalytic destruction methods have be employed so far in treatment wastewater comprising of nitrosamines. However, in this study, an advanced oxidation process (AOP) named heterogeneous photocatalysis is used as a means of treating N-Nitrosodiethylamine (NDEA) wastewater stream using tungsten trioxide based catalysts. Tungsten trioxide (WO3) is synthesized using Thermal Treatment Method (TTM) and Hard Template Replication Method (HTRM) to help investigate the effect of morphological and structural property changes on the NDEA wastewater degradation process. WO3 was also impregnated with other metals such Lanthanum (La), Iron (Fe), Chromium (Cr) and Silver (Ag) to help improve its light absorption ability for the photocatalytic reaction. These synthesized catalysts were characterized using UV-Vis spectroscopic technique to obtain their light harnessing ability as well as their band gap energies. The surface area and pore structure of the pristine and doped catalysts were also investigated using the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) technique. The crystallinity of the catalysts and their crystallite sizes were determined by employing the X-ray Diffraction (XRD) technique. The surface morphology and catalyst composition were also investigated by employing the use of Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS). Photocatalytic NDEA degradation using the synthesized WO3 based catalysts was investigated as a function of three input factors viz. catalyst loading (0.5-5%), solution pH (5-9) and catalyst concentration (0.5-1 g/L) by using Face-Centred Central Composite Design (FCCCD) adapted from response surface methodology (RSM). Using NDEA degradation efficiency as response, a 17-run experiment matrix was generated by the chosen design to investigate the interaction effects of the three above-mentioned input variables. From the results, a compact quadratic model showing high significance (p 0.05) was developed by means of analysis of variance (ANOVA), It predicted the experimental results with good accuracy as seen from the good coefficients of determination values (R2 0.9). The pH of the solution (5) was found to be the most significant design factor having a positive impact on NDEA degradation as its value decreases. The mean degradation efficiency of NDEA was 86.48% for La/WO3, 84.03% for Cr/WO3, 88.90% for Ag/WO3 and 93.03% for Fe/WO3. Using wastewater effluent volume of 148 m3/day from the Boundary Dam amine processing unit as a basis for economic analysis, a total capital investment of $216,981.69 was estimated. It was projected that an annual operating cost of $513,884.85 will be required to run the photocatalytic waste treatment plant at a treatment cost of $10.59/m3. This study presents a foundation for future research into the scale up and eventual commercialization of this wastewater treatment technique.