Advanced photochemical processes for the manufacture of nanopowders: an evaluation of long-term pilot plant operation

Based on our long term experience with the operation of a photochemical pilot plant, we propose an UV light-based technology for syntheses of nano-dimensional metal oxides (case study for ZnO,...

An investigation into the chemistry of HONO in the marine boundary layer at Tudor Hill Marine Atmospheric Observatory in Bermuda

Here we present measurement results of temporal distributions of nitrous acid (HONO) along with several chemical and meteorological parameters during the spring and the late summer of 2019 at Tudor Hill Marine Atmospheric Observatory in Bermuda. Large temporal variations in HONO concentration were controlled by several factors including local pollutant emissions, air mass interaction with the island, and long-range atmospheric transport of HONO precursors. In polluted plumes emitted from local traffic, power plant and cruise ship emissions, HONO and nitrogen oxides (NOx) existed at substantial levels (up to 278 pptv and 48 ppbv, respectively) and NOx-related reactions played dominant roles in daytime formation of HONO. The lowest concentration of HONO was observed in marine air, with median concentrations at ~3 pptv around solar noon and < 1 pptv during the nighttime. Considerably higher levels of HONO were observed during the day in the low-NOx island-influenced air ([NO2] < 1 ppbv), with a median HONO concentration of ~17 pptv. HONO mixing ratios exhibited distinct diurnal cycles that peaked around solar noon and were lowest before sunrise, indicating the importance of photochemical processes for HONO formation. In clean marine air, NOx-related reactions contributed to ~35 % of the daytime HONO source and the photolysis of particulate nitrate (pNO3) can account for the missing source assuming a moderate enhancement factor of 30 relative to gaseous nitric acid photolysis. In low-NOx island-influenced air, the contribution from both NOx-related reactions and pNO3 photolysis accounted for only ~30 % of the daytime HONO production, and the photochemical processes on surfaces of the island, such as the photolysis of nitric acid on the forest canopy, might contributed significantly to the daytime HONO production. The concentrations of HONO, NOx and pNO3 were lower when the site was dominated by the aged marine air in the summer and were higher when the site was dominated by North American air in the spring, reflecting the effects of long-range transport on the reactive nitrogen chemistry in the background marine environments.

PHYSICAL OR THEOLOGICAL APPROACH TO INVESTIGATE THE SHROUD IMAGE FORMATION BY UV RADIATION?

In this article, we ask ourselves if it is possible that Corona Discharge or Vacuum UV radiation may have been the tools to produce the Shroud body image. We are convinced that both are not appropriate mechanisms. In fact, the start of these processes is based on inconsistent hypotheses for the natural sciences, although all that follows is rational, reasonable and acceptable. However, the big initial mole remains. The complexity of this situation is such that it seems to be in a world in part Transcendent and in part Immanent. Therefore, independently from the possible results that in a next future could be obtained, due to identified photochemical processes, the Scientific Method cannot accept both the hypotheses and, consequently, the experiments. The same is also for the Theological approach which discards both proposals

Imposed dynamic irradiation to intensify photocatalytic reactions

Dynamic irradiation is a potent option to influence the interaction between photochemical reactions and mass transport to design high performant and efficient photochemical processes. To systematically investigate the impact of this parameter, the photocatalytic reduction of nitrobenzene was conducted as a test reaction. Dynamic irradiation was realized through provoked secondary flow patterns, multiple spatially distributed light emitting diodes (LEDs) and electrical pulsation of LEDs. A combined experimental and theoretical approach revealed significant potential to enhance photochemical processes. The reaction rate was accelerated by more than 70% and even more important the photonic efficiency was increased by more than a factor of 4. This renders imposed dynamic irradiation an innovative and powerful tool to intensify photoreactions on the avenue to large scale sustainable photochemical processes.

Application Limits of the Ferrioxalate Actinometer

<div>Evaluating the efficiency of newly designed photoreactors is crucial for systematic development and optimization of photochemical processes. A suitable tool is actinometry, prominently represented by the most widely studied and applied ferrioxalate system. However, such measurements show reproducible problems in the data consistency. This study scrutinizes these issues and approaches an experimental elucidation. An application limit for the ferrioxalate actinometer under intense irradiation was identified and experimentally validated. A drop of the quantum yield at high incident photon fluxes, generating high local concentrations of carboxyl radicals, leads to systematically wrong measurements. For reliable measurements with the ferrioxalate actinometry, a continuous operation mode or extensive mixing should be ensured.</div>

Application Limits of the Ferrioxalate Actinometer

<div>Evaluating the efficiency of newly designed photoreactors is crucial for systematic development and optimization of photochemical processes. A suitable tool is actinometry, prominently represented by the most widely studied and applied ferrioxalate system. However, such measurements show reproducible problems in the data consistency. This study scrutinizes these issues and approaches an experimental elucidation. An application limit for the ferrioxalate actinometer under intense irradiation was identified and experimentally validated. A drop of the quantum yield at high incident photon fluxes, generating high local concentrations of carboxyl radicals, leads to systematically wrong measurements. For reliable measurements with the ferrioxalate actinometry, a continuous operation mode or extensive mixing should be ensured.</div>

Photochemical treatments (UV/H2O2, UV/O3 and UV/H2O2/O3) and inverse osmosis in wastewater: Systematic review

Every year, the bodies of water receive millions of cubic meters of wastewater from municipal, industrial, agricultural or livestock discharges, treated in an inadequate way or without treatment. The objective of this study was to carry out a systematic review of the frequency of use and effectiveness of the main photochemical processes and the complementation with other treatments such as it is reverse osmosis, used in different types of wastewater effluents. We searched multiple electronic databases (2010-2021), using a stepwise searching approach, supplemented with hand searching. In vitro or in vivo English language publications, original studies, and reviews were included. The database was made up of a total of 100 articles that met the minimum selection criteria, of which 25 articles the maximum scores for analysis. These articles report the improvement in the elimination of pollutants when the treatments are used together and not individually, in relatively short times ranging from 30 minutes of radiation to 8 minutes of exposure to the treatments. Regarding the type of water that was treated, most of the articles report the decontamination of natural wastewater, that is, from the industry without treatment. The percentages calculated to identify research opportunities or gaps in relation to photochemical processes (UV/H2O2/O3). As proposed some authors, if any value of the percentage of pre-selected articles (PAA %) is less than the value of the percentage of failure (MAPAA %), a research opportunity is revealed not addressed by the literature. Based on the percentage results, it is observed that there are no gaps with respect to the photochemical processes or that there are possibly no updates reported in the literature yet.