Air Purge Research Articles

Night cooling by hybrid ventilation – analytical predictions of the purge time

Many low-energy buildings rely on a night purge strategy during periods of excessively warm weather in order to flush out excess heat and thereby help prevent overheating on the following day. A typical purge utilises either a mechanical or a natural displacement ventilation strategy. However, we investigate purging by the simultaneous application of natural and mechanical ventilation, i.e. using a hybrid strategy. Hybrid ventilation is widely promoted as a means of overcoming the inherent limitations of both natural and mechanical ventilation, although relatively little is understood about its operation on a fundamental level. Such was the lack of knowledge on hybrid ventilation that even the time taken to complete a purge was not known at the outset of this work. Through the development of a mathematical model, supported by a series of laboratory experiments, we show that the time taken to purge a room using hybrid ventilation can be established analytically, and is controlled by two ratios: (i) the flow rate of the mechanical supply (the ‘forcing’) relative to the initial flow rate through the vents in the absence of mechanical forcing, and (ii) the ratio of the floor-level and ceiling-level vent areas. The analytical predictions show close agreement with our measurements. Supplementing a natural displacement ventilation strategy with even a modest mechanical supply can reduce significantly the time taken to purge warm air from a room. Some of the implications of our findings for preventing overheating in buildings by increasing the efficacy of a night cooling strategy are discussed. Practical Application This research is directly applicable to practitioners involved in the first-order design of hybrid ventilation systems – particularly designs which incorporate a ‘night purge’ regime. Governing equations are derived and the key parameters controlling the rate of purging of warm air are revealed, allowing informed first-order design decisions to be made without the need for expensive and time-consuming computational simulations.

Water Sample Collection Methods for 222Rn Analysis by Scuba Diving: Insights on Groundwater Flushing of Anchialine Cave Systems of the Yucatan Peninsula

AbstractRadon (222Rn) is a widely used tracer in groundwater and surface water studies. In some applications of radon, samples need to be collected from deep submerged areas or discharge points such as caves or springs, locations typically accessed by scuba diving. However, there are no established sampling methods for collecting water by scuba diving for Rn analysis. We assessed four underwater sample collection methods: (a) injection into a catheter bag followed by transfer to a bottle after the dive, (b) air purging and then filling of a bottle by allowing gas to escape, (c) air purging followed by gas escape, and then overfilling of water with a syringe, and (d) collection with a syringe followed by transfer to a bottle. The samples were collected from the anchialine caves of the Yucatan Peninsula which are the longest underwater cave systems. The samples were analyzed using the same Rn‐in‐air analyzer and protocols. Statistical comparison of sampling at the same location with different methods showed no significant differences in Rn activity. No collection method is superior in terms of measurement quality; operational simplicity is thus preferred. Statistically significant differences in activity were observed between fresh and saline samples from the same cave, with higher activities in the fresh samples, regardless of sampling method. The saline groundwater therefore has a lower residence time, suggesting vigorous landwards flow. Our assessment shows that in situ sampling of discrete water samples for Rn tracing by divers is a useful and powerful approach allowing the study of otherwise impossible sites.

Study on the effect of NO2 impurity gas on the performance and local current density distribution of PEMFC

The performance of proton exchange membrane fuel cells (PEMFCs) is affected by impurities, and airborne NO2 is a potential factor in the degradation of the performance and durability of PEMFCs. Herein, the effect of 50 ppb ∼ 5 ppm NO2 on PEMFC was investigated by the poisoning strategy of increasing concentration gradient, and the effect of NO2 on the local current density distribution was explored in both galvanostatic and potentiostatic states. The results showed that 2 ppm NO2 caused a significant voltage decay accompanied by an increase in activation impedance and mass transfer impedance. NO2 was decomposed into oxygen atoms and adsorbed NO on the Pt surface, occupying active sites, impeding oxygen reduction reaction, and further hindering mass transfer. Polarization curve results showed more pronounced voltage decay at high current densities. Polarization curve testing and clean air purging were effective in restoring the poisoned PEMFC. Moreover, it was proved that the poisoning effect is more severe in the inlet region, especially in potentiostatic state. Hence, it is suggested to operate in galvanostatic state, which has a positive impact on reducing the uneven performance caused by NO2. This study provides a reference for the prevention of PEMFC poisoning and performance recovery after poisoning.

Fluid retention in endoscopes: A real-world study on drying effectiveness

Outbreaks linked to inadequate endoscope drying have infected numerous patients, and current standards and guidelines recommend at least 10minutes of forced air for drying channels. This study evaluated a new forced-air drying system (FADS) for endoscopes. Drying was assessed using droplet detection cards; visual inspection of air/water connectors, suction connectors, and distal ends; and borescope examinations of endoscope interiors. Assessments were performed after automated endoscope reprocessor (AER) alcohol flush and air purge cycles and after 10-minute FADS cycles. Researchers evaluated drying during encounters with 22 gastroscopes and 20 colonoscopes. After default AER alcohol and air purge cycles, 100% (42/42) of endoscopes were still wet. Substantial fluid emerged from distal ends during the first 15seconds of the FADS cycle, and droplets also emerged from air/water and suction connectors. Following FADS cycle completion, 100% (42/42) were dry, with no retained fluid detected by any of the assessment methods. Multiple endoscope ports and channels remained wet after AER cycles intended to aid in drying but were dry after the FADS cycle. This study reinforced the need to evaluate the effectiveness of current drying practices and illustrated the use of practical tools in a real-world setting.

WASP: Wearable Analytical Skin Probe for Dynamic Monitoring of Transepidermal Water Loss.

Early diagnosis of skin barrier dysfunction helps provide timely preventive care against diseases such as atopic dermatitis, psoriasis, food allergies, and other atopic skin disorders. Skin barrier function is commonly evaluated by measuring the transepidermal water loss (TEWL) through stratum corneum due to its noninvasive characteristics. However, existing commercial TEWL devices are significantly affected by many factors, such as ambient temperature, humidity, air flow, water accumulation, initial water contents on the skin surface, bulky sizes, high costs, and requirements for well-controlled environments. Here, we developed a wearable closed-chamber hygrometer-based TEWL device (Wearable Analytical Skin Probe, WASP) and the related algorithm for accurate and continuous monitoring of skin water vapor flux. The WASP uses short dry air purges to dry the skin surface and chamber before each water vapor flux measurement. Its design ensures a highly controlled local environment, such as consistent initial dry conditions for the skin surface and the chamber. We further applied WASP to measure the water vapor flux from six different locations of a small group of human participants. It is found that the WASP can not only measure and distinguish between insensible sweating (i.e., TEWL) and sensible sweating (i.e., thermal sweating) but also track skin dehydration-rehydration cycles. Comparisons with a commercial TEWL device, AquaFlux, show that the results obtained by both devices agree well. The WASP will be broadly applicable to clinical, cosmetic, and biomedical research.

Removal of volatile organic compounds and odorous compounds for multilayer packaging recyclates using heated air purging

Multilayer packaging (MLP) is made from Polyethylene terephthalate (PET), Polyethylene (PE), Polypropylene (PP), Ethylene vinyl alcohol (EVOH), Polyvinyl chloride (PVC), and tie layer materials. MLPs are either burned or dumped in landfills after their use, which causes many hazards to humans and the environment. MLPs are recycled in recycling facilities and converted into pellets to reuse them. However, the MLPs are strongly contaminated by volatile organic compounds and odorous compounds, which prevents their use in high-end applications, i.e., cosmetics, packaging, etc. In the research work, a remediation strategy is proposed to reduce VOCs and odorous compounds from MLP recyclates using heated air oven treatments, which are also easily scalable to pilot and industrial scales. VOCs and odor are reduced significantly without compromising the product’s mechanical, thermal, and other properties.

IRON REMOVAL FROM LADEN BIOLEACHING SOLUTION BY PROCESSES OF SOLVENT EXTRACTION AND MAGNETITE SYNTHESIS

Laden leach solution, generated from bioleaching of pyrometallurgical copper slags with a mixed culture of moderately thermophilic bacteria in a bioreactor, contains several base metals (Cu, Co, Zn) and a very high concentration of iron (33,9 g/ L). Further processing of cobalt and zinc to the respective final products requires preparatory iron removal from the laden leach solution. The direct iron removal from that solution as goethite was unacceptable because of the significant co-precipitation of copper and cobalt from the solution. The main aim of this paper is to study magnetite (Fe3O4) synthesis as an approach for iron removal to a value-added product as a step of the processing of a laden solution generated due to the bioleaching of non-ferrous metals in a bioreactor. Ferrous iron oxidation to ferric state was efficient when the addition of H2O2 (30 %) was combined with maintaining the pH 3,1-3,3 with NaOH and air purging. Solvent extraction with 25 % D2EHPA and 7,5 % TBP dissolved in kerosene efficiently separated the dissolved iron and the base metals from the processed solution. However, in the presence of H2, the iron was stripped from the organic solvent with low acid consumption. The applied precise control of the chemical precipitation and oxidation processes at 50 degrees Celsius allowed the iron content (11,7 g/ L) in the stripping solution to be removed efficiently as magnetite (Fe3O4). Based on the chemical content of iron, copper and sulphur, the synthesised nanoparticles of magnetite could be applicable in many sectors (steel, chemical, and electronics).

Concentrating solar power at higher limits: First studies on molten nitrate salts at 600 °C in a 100 kg-scale hot tank

With focus on a higher heat-to-electricity conversion efficiency, future developments in the field of thermal energy storage are aiming at higher operational temperatures. For that, increased decomposition rates of nitrate and nitrite are the limiting factor. Until now only small-scale laboratory experiments have been performed at temperatures above 565 °C. This study presents the to our knowledge for the first-time experiment on the thermal stability of Solar Salt (60 wt-% NaNO3, 40 wt-% KNO3) at temperatures up to 600 °C with synthetic air purge gas flow in a 100 kg scale. The key to the received data is a build-in gas system with direct gas analyzer, a sample extraction system and post-analysis of salt samples, that allows determination of molten salt decomposition products. Our research provides clear evidence of the feasibility in elevating the reactor temperature to 600 °C.

Air-Purge Regenerative Direct Air Capture Using an Externally Heated and Cooled Temperature-Swing Adsorber Packed with Solid Amine

CO2 capture from air is crucial in achieving negative emissions. Based on conventional or newly developed high-enriching processes, we investigated the rough enrichment of CO2 from air via an externally heated or cooled adsorber (temperature-swing adsorption, TSA), along with air purge using double-pipe heat exchangers packed with low-volatility polyamine-loaded silica. A simple adsorption–desorption cycle was attempted in a TSA experiment, by varying the temperature from 20 °C to 60 °C using moist air, yielding an average CO2 concentration of product gas that was ~17 times higher than the feed air, but the CO2 recovery rate was poor. A double-step adsorption process was applied to increase CO2 adsorption and recovery simultaneously. In this process, substantial-CO2-concentration gas was used as the product gas, and the remaining gas was used as the reflux feed gas for adsorber. This method can provide a product gas with ~100 times higher CO2 concentration than raw gas, with a recovery ratio ~60% under the shortest adsorption/desorption time and the longest refluxing time of cycle operation. Therefore, the refluxing step significantly helped to enhance CO2 capture via adsorption from elevated-CO2-concentration recirculating gas. With this CO2 concentration, the product gas can serve as the CO2 supplement for the growing plant processes.

DLSU Initiatives and Challenges: Energy & Climate Change

De La Salle University is committed to reducing its impact on the environment and to promoting positive action that will help reduce its carbon footprint. In its vision-mission, it emphasizes the need to be “attuned to a sustainable earth.” This paper presents the different initiatives and challenges faced by the university, especially while still in a global pandemic. A number of initiatives have been undertaken to promote energy efficiency in campus operations and climate action, particularly regarding reducing greenhouse gas emissions. However, facing the COVID-19 pandemic and preparing campus operations for the gradual resumption of face-to-face classes have presented new challenges moving into the next normal. The need to address health and safety concerns has resulted in increased consumption of electricity. Challenges are experienced particularly in ensuring improved indoor air quality as well as allowing indoor-outdoor air exchange. The setting up of (a) air purifiers and/or additional auxiliary fans in high foot-traffic areas, (b) installation of HEPA filters and UV-C lamps into HVAC systems, (c) extended use of air conditioning units to allow purging of air before and at the end of activities, and (d) the opening of air exchange dampers in the University’s HVAC systems, are all expected to result in increased demand for electricity.

Online MEMS-Based Specific Gravity Measurement for Lead-Acid Batteries

Traditional methods for measuring the specific gravity (SG) of lead-acid batteries are offline, time-consuming, unsafe, and complicated. This study proposes an online method for the SG measurement to estimate the state-of-charge (SoC) of lead-acid batteries. This proposed method is based on an air purge system integrating with a micro electro mechanical system sensor. Through the proposed strategy, the SoC measurement achieves up to ±1% accuracy. The technique has an SG accuracy of ±0.002% which is better than the glass hydrometer accuracy of ±0.005% in the battery charge reading. The experimental results show that the high accuracy and precise measurements of SG and SoC can be conducted by using the proposed method.

Analysis of Ash Melting Temperatures of Agricultural Pellets Detected during Different Conditions

Agricultural and other residues are promising renewable energy sources. However, they can cause problems in combustion processes. One of these problems is also low ash melting temperatures. Except, the ash melting behavior can be impacted by many factors, such as ash preparation or used atmosphere. This article deals with comparing different atmosphere conditions during measurements of ash melting temperatures of three agricultural pellets: alfalfa, straw, and hay. The first one was oxidizing with compressed air and nitrogen. The second atmosphere was reduced with the air purge, and the last was only reduced, consisting of 60% carbon monoxide and 40% carbon dioxide. Differences between individual atmospheres were none, up to 9.8%. The most significant differences have appeared between oxidizing and reducing atmospheres. In general, the oxidizing atmosphere presents a less expensive way. More attention should be paid to the use of oxidizing atmosphere for applications in heat sources mainly due to its similarity to the combustion process. However, it would be suitable to realize more comprehensive research regarding ash preparation in different ways and with using of different types of fuel.

Temperature measurement and error analysis of the transverse plane of oil-jet-lubrication herringbone gear with infrared pyrometers.

Frictional power losses of high-speed and heavy-load herringbone gearboxes increase the temperature of the gearbox. Thus, real-time surface temperature measurement is significant for evaluating the gearbox lubrication design. A rotating gear test rig with an infrared pyrometer is developed in this paper to conduct real-time and accurate temperature measurements of the transverse plane of the oil-jet-lubrication herringbone gear. First, the influencing factors and measuring errors of surface temperature are analyzed using the infrared pyrometer. The emissivity of the measured surface of a gear tooth painted with matte black is experimentally calibrated. Second, the temperature measurement tests of the oil-jet-lubrication herringbone gear under different conditions are carried out. Measurement errors resulting from purge air pressure, purge air temperature, and oil-jet temperature are also experimentally studied. The results indicate that the purge gas flow can reduce the measurement errors of the infrared pyrometer resulting from oil mist with an appropriate purge air pressure and purge air temperature. Finally, a mathematical curve-fitting of the measurement results between the infrared pyrometer and thermocouple is carried out. The calculated temperatures by the curve-fitting formula are compared with the measured thermocouple temperature, with the relative differences being less than 1 °C. Thus, the curve-fitting formula is credible for the real-time measurement of surface temperature, while the relevant measuring method is also valuable for engineering applications of high-speed gear systems under oil-jet-lubrication conditions.

Development of nucleocapsid-specific monoclonal antibodies for SARS-CoV-2 and their ELISA diagnostics on an automatic microfluidic device

Coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has threatened public health globally, and the emergence of viral variants has exacerbated an already precarious situation. To prevent further spread of the virus and determine government action required for virus control, accurate and rapid immunoassays for SARS-CoV-2 diagnosis are urgently needed. In this study, we generated monoclonal antibodies (mAbs) against the SARS-CoV-2 nucleocapsid protein (NP), compared their reactivity using an enzyme-linked immunosorbent assay (ELISA), and selected four mAbs designated 1G6, 3E10, 3F10, and 5B6 which have higher reactivity to NP and viral lysates of SARS-CoV-2 than other mAbs. Using an epitope mapping assay, we identified that 1G6 detected the C-terminal domain of SARS-CoV-2 NP (residues 248–364), while 3E10 and 3F10 bound to the N-terminal domain (residues 47–174) and 3F10 detected the N-arm region (residues 1–46) of SARS-CoV-2 NP. Based on the epitope study and sandwich ELISA, we selected the 1G6 and 3E10 Abs as an optimal Ab pair and applied them for a microfluidics-based point-of-care (POC) ELISA assay to detect the NPs of SARS-CoV-2 and its variants. The integrated and automatic microfluidic system could operate the serial injection of the sample, the washing solution, the HRP-conjugate antibody, and the TMB substrate solution simply by controlling air purge via a single syringe. The proposed Ab pair-equipped microsystem effectively detected the NPs of SARS-CoV-2 variants as well as in clinical samples. Collectively, our proposed platform provides an advanced protein-based diagnostic tool for detecting SARS-CoV-2.

A novel gas removal method for the removal of C2H2 in calcium carbide slag slurry by fine bubbles combined with air purging: performance, mechanism, and in situ bubble imaging analysis

About 60% of carbon emissions in the cement industry come from the decomposition of limestone. As a key low-carbon technology of raw material substitution, calcium carbide slag (CCS, low-carbon calcareous material) can replace limestone to produce cement, desulfurizer, and other products, which can achieve carbon emission reduction and the upcycling of CCS. However, the release of residual C2H2 in CCS brings safety and environmental risks, which seriously restricts the upcycling of CCS. In this study, a novel gas removal method of fine bubbles (FBs) degassing was proposed for the removal of C2H2 in solid CCS particles, and an advanced in situ bubble imaging technology was used to investigate the performance and mechanism of C2H2 removal. The results indicated that approximately 70% of C2H2 (encapsulated C2H2) in CCS was difficult to remove by drying or slurrying. Under the optimal condition, the C2H2 removal efficiency was approximately 61.0%, and the amount of C2H2 released from the CCS slurry decreased by 92.9%. In the process of FBs degassing, large CCS particles in the CCS slurry were broken up into fine particles via the erosion mechanism, thus promoting the reaction of the encapsulated calcium carbide with water to produce C2H2. The generated C2H2 was dissolved in the slurry and could be quickly removed by FBs (<500 μm) with a fast mass transfer rate under the slight negative pressure. This work provides a novel gas removal method for effectively removing C2H2 in CCS and avoiding security and environmental risks, provides technical support for the upcycling of CCS, and provides a reference for the separation of other similar multiphase systems (e.g., gas–liquid/gas–liquid–solid, oil-liquid/oil-liquid–solid).

Enhanced adsorption-oxidation performance of PMo12 immobilized onto porous MCM-41 derived from rice husk for H2S at room temperature

In this study, a novel adsorbent (PMo12@RH-MCM-41) was synthesized through impregnation method using waste rice husk and phosphomolybdic acid (PMo12) as the silica source and active center, respectively. The regular fibrous-like structure of RH-MCM-41 with hierarchical pores provides a high percentage of exposed PMo12 sites, enhancing the desulfurization activity of PMo12. PMo12@RH-MCM-41 exhibited excellent desulfurization ability in comparison with PMo12 and RH-MCM-41, demonstrating the synergistic effect between PMo12 and RH-MCM-41. The efficient transformation of H2S to elemental S with a yield of 61.3 % was achieved at room temperature. The PMo12@RH-MCM-41 regenerated by hot air purging can maintain the stable desulfurization ability for more than 8 cycles. The mechanism analysis demonstrated the redox ability of PMo12 in the heterogeneous desulfurization system. This work provides important insights for the application of polyoxometalates in solid-phase desulfurization, and broadens high-value utilization patterns of agricultural waste biomass.

Novel Micro flow Sensor for Air Purge Method to Monitor the State of Charge of Lead Acid Battery

The foremost aim of the present research study is to measure specific gravity of lead-acid batteries and further know batterys state-of-charge (SoC). In this article, air purge method is used to monitor the status of a battery; back differential pressure is measured using MPX4006 DP MEMS pressure sensor. In air purge method, it is essential to adjust the rate of bubbles in acid. This can be achieved by controlling the compressors speed or controlling the air flow by controllers. When air purge tubes are inserted through a batterys cap, it is difficult to observe bubbles produced in the acid as the battery is nontransparent. If the bubble rate is too slow, the system lowers the output signal and hence stops working. During the calibration of the instrument, air flow measurement through the pipe is of prime importance. In this method, FS1012 MEMS gas flow sensor is used to monitor the discharged air flow. FS1012 is based on the thermo-transfer principle. Compared to the resistive technique, this flow sensor consists of a thermopile for air flow sensing whose signal-noise ratio is exceptional. The output of the sensor is exponential; signal conditioning circuit has been designed to get linear output 0 to 3.3 V standard range. The amplified output of signal conditioning circuit is monitored using TM4C123GXL arm controller. FS1020 is first time proposed to monitor the air flow of a small air purge probe used to monitor the state of charge of a lead-acid battery. FS1020 ensures an ideal flow of the air bubbler system, which improves the performance of the battery charge monitoring system. Conventional flow sensors for example, rotameter cannot be used for very low flow measurement; they are costlier as well as bulky. The minimum flow required to produce sufficient bubbles in acid is 0.50 liter per minute (LPM) which is measured by FS 1012.

Effect of air addition to the air electrode on the stability and efficiency of carbon dioxide electrolysis by solid oxide cells

In this study, the effect of air addition to the air electrode on the long-term stability and efficiency of solid oxide cells for CO2 electrolysis, with 23.8% CO as protective gas in the fuel electrode, has been investigated. The results show that without continuous purging of the air in the air electrode (Cell-1), the degradation rate was 8.37%/kh in the 1070 h electrolysis process, while with 5 L/min air supplied to the air electrode (Cell-2), the degradation rate was 24.41%/kh. Impedance analysis indicates that the degradation of Cell-1 was mainly because of the increase in O2− exchange polarization impedance, while the degradation of Cell-2 was caused mainly by the variation of ohmic impedance. The microstructural characterization indicated a decrease in active Ni in the fuel electrode in both Cell-1 and Cell-2, but the degree of nickel loss depended on the test time. At the outlet of the Cell-2, the appearance of carbon further explains the faster degradation rate, although the carbon deposition was not directly caused by the introduction of air into the air electrode. Energy spectral analysis shows that the air electrode in Cell-1 generated Sr rich phases, which indicates that the absence of air in the air electrode in the electrolysis process indeed causes more serious microstructure damage. The energy conversion efficiency could exceed 86% if the energy consumed for heating the air is ignored. This work provides a scenario for the application of solid oxide cells for CO2 electrolysis without air purging in the air electrode.

Study of droplet flow characteristics on a wetting gradient surface in a proton exchange membrane fuel cell channel using lattice Boltzmann method

Effective water management is essential to improve the performance of proton exchange membrane fuel cells (PEMFCs). A pseudopotential multiple relaxation time (MRT) multi-component lattice Boltzmann method (LBM) is used to simulate the droplet flow behavior in the channel with different wetting gradient surfaces under air purge. The model is verified by thermodynamic consistency, large density ratio and viscosity ratio, surface tension independent regulation, Laplace's law, and static contact angle test. The results indicate that the shape of the droplet moving on the surface with different wetting gradients changes differently, resulting in different pressure differences between the inlet and outlet of the flow channel. Considering only the discharge time, the surface with a continuous variation of contact angle from 140° to 100° has the best purging effect. The motion of two droplets on this surface is simulated, and it is found that the short distance and large size difference between the two droplets facilitate the rapid discharge of the droplets from the flow channel. However, the shorter the distance, the more violent the droplet deformation during the coalescence process and the greater the pressure difference caused.

Photodegradation of F–53B in aqueous solutions through an UV/Iodide system

Advanced reduction by strong reducing hydrated electrons is a promising approach to degrade per- and polyfluoroalkyl substances (PFAS). This research aimed to investigate the effectiveness of UV/Iodide system for 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA, F–53B) degradation in aqueous solutions. Results from this work demonstrated that UV irradiation with an addition of 0.3 mM KI resulted in 55.99% degradation of F–53B within 15 min and almost 100% within 2 h. The defluorination efficiency of F–53B in the UV/Iodide system was 2.6 times higher than that in the sole UV system after 2 h of irradiation. The degradation efficiency of F–53B was not significantly affected by air purging. The defluorination efficiency with air bubbling, however, was 14.57% lower than that with nitrogen purging. The photodegradation of F–53B in the UV/Iodide system could be well described by a pseudo-first-order kinetic model. Degradation rate constant of F–53B correlated positively with the initial concentration. At 20 μg/L, the pseudo-first-order rate constant was 5.641 × 10−2 min−1 and the half-life was 12.29 min. Higher initial concentration also required less energy input to achieve the same degradation efficiency. The detection and identification of degradation intermediates implied that destruction of F–53B started from dechlorination and followed by continuously “flaking off” CF2 units.