A review: Biological technologies for nitrogen monoxide abatement

Removal pathways and mechanism of NO by Tetradesmus obliquus PF3 culture-based DeNOx system

Microalgae-based DeNOx technology, as an emerging approach for flue gas denitrification, is suitable for the deep treatment of NOx at medium to low concentrations. To address the ambiguity surrounding the removal pathways and mechanisms in the development of microalgae DeNOx technology, the pathways and mechanisms of NO removal within a microalgae cultivation system was investigated. By investigating the gas-liquid and liquid-solid nitrogen transfer pathways facilitated by algal cells, algal cells were found to play a pivotal role in NO removal by the T. obliquus PF3 cultivation system. Microalgae cells enhance NO transfer across gas-liquid phases via extracellular substance secretion, exogenous iron reduction, NO adsorption, and NO molecular absorption. During this process, NO is transformed in the liquid phase into molecular NO, ionic nitrate, and nitrite, as well as organically complexed NO. The soluble extracellular substances of T. obliquus PF3 are primarily composed of humic-like acids and fulvic-like acids, while bound extracellular substances are dominated by tryptophan and tryptophan-like proteins, both of which possess reductive properties conducive to iron reduction and NO adsorption/complexation. By employing ATP hydrolysis inhibitor HgCl2 and analyzing nitrogen balance in the system, It was revealed that the primary NO removal pathway involves NO dissolution and oxidation within the algal culture broth, with ionic nitrogen being the predominant form assimilated and utilized by algal cells from the solution. This study clarifies the NO removal pathways and mechanisms within the microalgae cultivation system, thereby providing a theoretical foundation for the advancement and process design of microalgae-based DeNOx technology.

Air pollution and breast cancer risk: a Mendelian randomization study

Previous research yields inconsistent findings on the association between air pollution and breast cancer risk, with no definitive causal relationship established. To address this, we conducted a two-sample Mendelian randomization study on data from the IEU open GWAS databases and the Breast Cancer Association Consortium to explore the potential link between air pollution (including PM2.5, PM2.5 absorbance, PM2.5-10, PM10, NO2, and NOx) and breast cancer risk. We found that PM10 (odds ratio (OR) = 1.39, 95% CI: 1.07-1.80, p = 0.013) and NOx (OR = 1.67, 95% CI: 1.16-2.41, p = 0.006) were significantly associated with elevated breast cancer risk. Furthermore, PM2.5 (OR = 2.10, 95% CI: 1.09-4.03, p = 0.027) and NOx (OR = 3.08, 95% CI: 1.24-7.64, p = 0.015) were significantly associated with an elevated risk of luminal B/HER2-negative-like cancer. Results were stable in sensitivity analyses. This suggested that controlling air pollution could potentially reduce breast cancer risk.

Optimization of Injection Source Settings for SNCR Numerical Simulation of Low-Water Content Biomass Boilers with Blending

In order to control NOx emissions and meet China's ultralow emission standards, a numerical simulation based on the computational fluid dynamics (CFD) approach is performed for the optimization of the reductant injection volume, number of injection sources, distribution, and injection direction for the flue gas denitrification process of a circulating fluidized bed boiler (CFB) blended with low-water content biomass in a 168 MW unit of a thermal power plant. Using the target power plant boiler entity as a template, a simplified geometric model is established, 1:1, and the mass fractions of each flue gas component set by the inlet boundary conditions are O22, H2O11.6, CO216.2%, and NO0.05%(about 134 ppm), and the reduction reactions under different optimized conditions are numerically simulated using the SNCR model in ANSYS Fluent 2021 R1. The simulation results under each condition were analyzed. The results show that the optimal ammonia-to-nitrogen ratio should be taken as NSR = 1.25, the denitrification efficiencies of 81.00, 81.63, and 82.74% at the three outlets are high, and the ammonia escapes of 1.76, 2.08, and 9.42 mg/s are within a reasonable range; increasing the number of injection sources can significantly reduce the disturbance of the flue gas flow field by reductant injection; the direction of injection is parallel to the direction of the flue gas flow, and the line of the injection source is orthogonal to the direction of the flue gas flow, which is conducive to the mixing of the reductant and flue gas; the optimized boiler denitrification efficiency reaches 74.2%, meeting the ultralow emission requirements of nitrogen oxides and ammonia escape.

Mass transfer vectors for nitric oxide removal through biological treatments

The reduction of nitric oxide (NO) emissions to atmosphere has been recently addressed using biological technologies. However, NO removal through bioprocesses is quite challenging due to the low solubility of NO in water. Therefore, the abatement of NO emissions might be improved by adding a chelating agent or a mass transfer vector (MTV) to increase the solubility of this pollutant into the aqueous phase where the bioprocess takes place. This research seeks to assess the performance of different non-aqueous phase liquids (NAPs): n-hexadecane (HEX), diethyl sebacate (DSE), 1,1,1,3,5,5,5-heptamethyl-trisiloxane (HTX), 2,2,4,4,6,8,8-heptamethylnonane (HNO), and high temperature silicone oil (SO) in chemical absorption-biological reduction (CABR) integrated systems. The results showed that HNO and HTX had the maximum gas-liquid mass transfer capacity, being 0.32 mol NO/kmol NAP and 0.29 mol NO/kmol NAP, respectively. When an aqueous phase was added to the system, the mass transfer gas-liquid of NO was increased, with HTX reaching a removal efficiency of 82 ± 3% NO with water, and 88 ± 6% with a phosphate buffer solution. All NAPs were tested for short-term toxicity assessment and resulted neither toxic nor inhibitory for the biological activity (denitrification). DSE was found to be biodegradable, which could limit its applicability in biological processes for gas treatment. Finally, in the CABR system tests, it was shown that NO elimination improved in a short time (30 min) when the three mass transfer vectors (HEX, HTX, HNO) were added to enriched denitrifying bacteria.