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Your search keyword '"Ultraviolet light-emitting diodes (UV-LED)"' showing total 3 results
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3 results on '"Ultraviolet light-emitting diodes (UV-LED)"'

1. Effects of ultraviolet light emitting diodes (LEDs) on microbial and enzyme inactivation of apple juice.

Author

Akgün, Merve Pelvan and Ünlütürk, Sevcan

Subjects
*EFFECT of ultraviolet radiation on bacteria, *ENZYME inactivation, *APPLE juice, *ESCHERICHIA coli, *FRUIT juice pasteurization, *LIGHT emitting diodes
Abstract

In this study, the effects of Ultraviolet light-emitting diodes (UV-LEDs) on the inactivation of E. coli K12 (ATCC 25253), an indicator organism of E. coli O157:H7, and polyphneoloxidase (PPO) in cloudy apple juice (CAJ) were investigated. The clear (AJ) and cloudy apple juice were exposed to UV rays for 40 min by using a UV device composed of four UV-LEDs with peak emissions at 254 and 280 nm and coupled emissions as follows: 254/365, 254/405, 280/365, 280/405 and 254/280/365/405 nm. UV-LEDs at 254 nm achieved 1.6 ± 0.1 log 10 CFU/mL inactivation of E. coli K12 at UV dose of 707.2 mJ/cm 2 . The highest inactivation of E. coli K12 (2.0 ± 0.1 log 10 CFU/mL and 2.0 ± 0.4 log 10 CFU/mL) was achieved when the cloudy apple juice was treated with both 280 nm and 280/365 nm UV-LEDs. For clear apple juice the highest inactivation 4.4 log 10 CFU/mL obtained for E. coli K12 was achieved using 4 lamps emitting light at 280 nm for 40 min exposure time. For the same treatment time, the experiments using a combination of lamps emitting light at 280 and 365 nm (2lamp/2lamp) were resulted in 3.9 ± 0.2 log 10 CFU/mL reductions. UV-A and UV-C rays in combination showed a better inactivation effect on PPO than UV-C rays used separately. Residual activity of PPO in CAJ was reduced to 32.58% when treated with UV-LED in combination of UV-C (280 nm) and UV-A (365 nm) rays. Additionally, the total color change (ΔE) of CAJ subjected to combined UV-LED irradiation at 280/365 nm was the lowest compared to other studied processing conditions. This study provides key implications for the future application of UV-LEDs to fruit juice pasteurization. [ABSTRACT FROM AUTHOR]

Published
2017
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2. Investigation of the efficacy of the UV/Chlorine process for the removal of trimethoprim: Effects of operational parameters and artificial neural networks modelling

Author

Ying Shen Teo, Iman Jafari, Fei Liang, Youmi Jung, Jan Peter Van der Hoek, Say Leong Ong, and Jiangyong Hu

Subjects
Environmental Engineering, Ultraviolet Rays, Artificial neural network modelling, Pollution, UV/Chlorine, Trimethoprim, Water Purification, Kinetics, Reactive chlorine species (RCS), Machine learning, Environmental Chemistry, Ultraviolet light-emitting diodes (UV-LED), Neural Networks, Computer, Chlorine, Waste Management and Disposal, Oxidation-Reduction, Water Pollutants, Chemical
Abstract

The UV/Cl2 process (also known as chlorine photolysis, which is the combination of chlorine and simultaneous irradiation of UV light) is conventionally applied at acidic mediums for drinking water treatment and further treatment of wastewater effluents for secondary reuse. This is because the quantum yield of HO• from HOCl (ϕHO•, 254 = 1.4) is greater than the one from OCl- (ϕHO•, 254 = 0.278) by approximately 5 times. Moreover, chlorine photolysis in acidic mediums also tends to have lower radical quenching rates than that of their alkaline counterparts by up to 1000 times. The aim of this research is to investigate the applicability of the UV/Cl2 process by assessing its efficacy on the removal of trimethoprim (TMP) at not only acidic to neutral conditions (pH 6-7), but also alkaline mediums (pH 8-9). At alkaline pH, free chlorine exists as OCl- and since OCl- has a higher molar absorption coefficient as compared to HOCl at higher wavelengths, there would be higher reactive chlorine species (RCS) formation and contribution. TMP removal followed pseudo-first order kinetics and depicted that a maximum fluence based constant (kf′ = 0.275 cm2/mJ) was obtained using 42.25 μM (3 mg/L) of chlorine at pH 9, with an irradiation of 275 nm. At alkaline conditions, chlorine photolysis performance followed the trend of UV (275)/Cl2 > UV (265)/Cl2 > UV (310)/Cl2 > UV (254)/Cl2. RCS like Cl•, Cl2−• and ClO• contributed to the degradation of TMP. When the pH was increased from 6 to 8, contribution from hydroxyl radicals (HO• ) was decreased whilst that of RCS was increased. Application of UV (310)/Cl2 had the highest HO• generation, contributing to TMP removals up to 13% to 48% as compared to 5% to 27% in UV (254, 265, 275)/Cl2 systems at pH 6-9. Artificial neural networks modelling was found to be able to verify and predict the contribution of HO• and RCS conventionally calculated via the general kinetic equations in the UV/Cl2 system at 254, 265, 275 and 310 nm.

Published
2021

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