Deactivation and ultraviolet C-induced regeneration of photocatalytic oxidation air filters
Bibliographic record
Abstract
Ultra-violet photocatalytic oxidation has been regarded as one of the promising air purification technologies for improving indoor air quality. However, limited availability of experimental data in terms of photocatalyst deactivation and regeneration has hindered successful implementation of ultra-violet photocatalytic oxidation air cleaners in mechanical ventilation systems. The objective of this study is to obtain knowledge of the ultraviolet C-induced regeneration method, the simplest on-site approach, for the recovery of photocatalytic activity of photocatalytic oxidation filters after challenging ultra-violet photocatalytic oxidation systems with approximately 100 ppb of acetone or methyl ethyl ketone. Experimental observations of photocatalyst deactivation, and characterization of fresh and deactivated photocatalyst with the scanning electron microscope technique were presented. During the regeneration process, the production rates of formaldehyde, acetaldehyde, and acetone were hourly quantified under a short-term and a long-term ultraviolet C illumination. The regeneration performance was also examined and compared by testing the single-pass removal efficiency of regenerated photocatalytic oxidation filters by two methods: ultraviolet C illumination and O3-included ultraviolet C illumination. The results indicate that the ultraviolet C-induced regeneration method, superior to O3-assisted ultraviolet C method, plays a certain role in partial recovery of the photocatalytic activity. The degree of recovery would depend on the nature of contaminant gases previously processed in ultra-violet photocatalytic oxidation since different VOCs generate various types and amounts of surface adsorbed by-products, which resist regeneration at a different level.Graphical Abstract. UV-PCO represents a new generation technology for improving indoor air quality. However, little is known about photocatalyst deactivation and regeneration which is a major concern for the purpose of commercialization. The current objective is to explore the UVC-induced regeneration method, the simplest on-site approach, employed in an HVAC system. This work demonstrates a systematic evaluation of deactivation and UV-induced regeneration performance under the conditions relevant to the actual applications for two VOCs. In addition, the gaseous by-product generation rates and O3-assited UVC-induced recovery method were examined for the first time.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".