UV-C Light Irradiation Research Articles

Effectiveness of UV-C light irradiation on disinfection of an eSOS® smart toilet evaluated in a temporary settlement in the Philippines

Ultraviolet germicidal (short wavelength UV-C) light was studied as surface disinfectant in an Emergency Sanitation Operation System® smart toilet to aid to the work of manual cleaning. The UV-C light was installed and regulated as a self-cleaning feature of the toilet, which automatically irradiate after each toilet use. Two experimental phases were conducted i.e. preparatory phase consists of tests under laboratory conditions and field testing phase. The laboratory UV test indicated that irradiation for 10 min with medium–low intensity of 0.15–0.4 W/m2 could achieve 6.5 log removal of Escherichia coli. Field testing of the toilet under real usage found that UV-C irradiation was capable to inactivate total coliform at toilet surfaces within 167-cm distance from the UV-C lamp (UV-C dose between 1.88 and 2.74 mW). UV-C irradiation is most effective with the support of effective manual cleaning. Application of UV-C for surface disinfection in emergency toilets could potentially reduce public health risks.

Photocatalytic degradation of 2, 4, 6-Ttrichlorophenol with CdS nanoparticles synthesis by microwave-assisted sol-gel method

This paper reports the synthesis and characterization of photocatalyst CdS nanoparticles for investigation of photocatalytic degradation of 2,4,6-trichlorophenol. CdS nanoparticles were synthesized by the microwave-assisted sol-gel method and characterized by various techniques such as X-ray diffraction, filed emission scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy and UV-visible spectrophotometer. The average crystallite size was found to be 46 nm. The influences of catalyst amount, contaminant concentration, and pH of the reaction solution were evaluated and optimized. Highest degradation was obtained after 3hours UV-C light irradiation. The kinetic was evaluated in different contaminant concentrations under optimized conditions. It showed that the 2,4,6-trichlorophenol degradation reactions follow pseudo first order kinetic.

Improvement in photocatalytic activity of morphologically controlled Pd-supporting TiO2 particles via sol–gel process using inkjet nozzle

The purpose of the present study is to prepare palladium-supporting porous titania particles via a sol–gel process using an inkjet nozzle and to improve the photocatalytic activity of the particles. The morphology of titania particles produced by the sol–gel process using an inkjet nozzle was evaluated by scanning electron microscopy and nitrogen physisorption measurements. The photocatalytic activity of the obtained titania particles was evaluated using the changes in the concentration of a methylene blue solution under UVC light irradiation and the effect of palladium supported on the inner and outer surfaces of the titania particles on the photocatalytic activity was investigated.The titania particles prepared by inkjet processing exhibited spherical porous structures. The particle and pore size distributions of the obtained titania particles were more uniform than those of the titania particles prepared using the non-inkjet nozzle. The titania particles supporting palladium on the inner and outer surfaces exhibited a faster rate of photocatalytic degradation than the titania particles supporting palladium on only the outer surface, with anatase titania particles exhibiting the highest rate of photocatalytic degradation. Thus, we have successfully improved the photocatalytic activity of titania particles by supporting palladium on the inner and outer titania surfaces. This sol–gel process using an inkjet nozzle is an effective method for the preparation of porous titania particles supporting palladium on their inner and outer surfaces.

Antibacterial activities of gel-derived Ag-TiO<sub>2</sub>-SiO<sub>2</sub> nanomaterials under different light irradiation

Gel-derived Ag-TiO2-SiO2 nanomaterials were prepared by sol-gel process to determine their disinfection efficiency under UV-C, UV-A, solar irradiations and in dark condition. The surface morphology and properties of gel-derived Ag-TiO2-SiO2 nanomaterials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET specific surface area. The results showed that the average particle size of Ag-TiO2-SiO2 was around 10.9–16.3 nm. SiO2 mixed with TiO2 (the weight ratio of Si to Ti = 10:90) in the synthesis of Ag-TiO2-SiO2 by sol-gel process was found to increase the specific surface area of the obtained photocatalyst (164.5 m2g−1) as compared with that of commercial TiO2(P25) (53.1 m2g−1). Meanwhile, Ag doped in TiO2 (the mole ratio of Ag to TiO2 = 1%) decreased the specific surface area to 147.3 m2g−1. The antibacterial activities of gel-derived Ag-TiO2-SiO2 nanomaterials were evaluated by photocatalytic reaction against Escherichia coli bacteria (ATCC®25922). Ag-TiO2-SiO2 nanomaterials was observed to achieve higher disinfection efficiency than the catalyst without silver since both Ag nanoparticles and ions exhibit a strong antibacterial activity and promoted the e− – h+ separation of TiO2. The bactericidal activity of Ag-TiO2-SiO2 nanomaterial under light irradiation was superior to that under dark and only light. The reaction time to achieve a reduction by 6 log of bacteria of UV-C light alone and Ag-TiO2-SiO2 with UV-C light irradiation were 30 and 5 minutes, respectively. In addition, the superior synergistic effect of Ag-TiO2-SiO2 under both UV-A and solar light as compared to that under UV-C counterpart could be ascribed to the red-shift of the absorbance spectrum of the Ag doped TiO2-based catalyst.

Photocatalytic degradation of methyl orange and real wastewater by silver doped mesoporous TiO2 catalysts

Abstract The photocatalytic activity of silver doped mesoporous TiO 2 catalysts was evaluated for water treatment. Doped catalysts were prepared by impregnation-reduction with citrate using various Ag loadings (0.5 wt%, 1.5 wt% and 3 wt%) and characterized by X-Ray powder diffraction (XRD), BET and diffuse reflectance UV–vis spectroscopy (DR/UV–vis). Silver doped TiO 2 catalysts retain the physical properties of mesoporous TiO 2 and its hexagonal order. The degradation of methyl orange (MO) as a model organic pollutant and of a real wastewater effluent was carried out under UVC, UVB, UVA and simulated solar light irradiation. Mesoporous TiO 2 showed a better activity than P25 TiO 2 and photocatalytic performance of silver doped mesoporous TiO 2 was enhanced compare to undoped. The mineralization of the organic pollutant was investigated by total organic carbon (TOC) measurements. The 0.5 wt%Ag/TiO 2 exhibited the highest TOC abatement both for the mineralization of MO and of real wastewater under UV and simulated solar light. Moreover, the catalyst was stable and could be used repeatedly. Therefore, this catalyst is promising for photocatalytic wastewater treatment under solar irradiation, leading to a cheap technology for developing countries.

Microwave-assisted polyol synthesis and characterization of pvp-capped cds nanoparticles for the photocatalytic degradation of tartrazine

Polyvinylpyrrolidone capped cadmium sulfide nanoparticles have been successfully synthesized by a facile polyol method with ethylene glycol. Microwave irradiation and calcination were used to control the size and shape of nanoparticles. Characterization with scanning electron microscopy revealed a restricted nanoparticles growth comparing with the uncapped product, hexagonal phase and 48nm average particle size were confirmed by X-ray diffraction, and finally mechanism of passivation was suggested depending on Fourier transform infrared spectra.The efficiency of nanoparticles was evaluated by the photocatalytic degradation of tartrazine in aqueous solution under UVC and visible light irradiation. Complete degradation of the dye was observed after 90min of UVC irradiation under optimized conditions. Kinetic of reaction fitted well to the pseudo-first-order kinetic and Langmuir–Hinshelwood models. Furthermore, 85% degradation of the dye in 9h under visible light suggests that cadmium sulfide is a promising tool to work under visible light for environmental remediation.

Fullerene-modified silica materials designed for highly efficient dyes photodegradation

Dye photodegradation of fullerene-modified silica materials has been investigated for ecological purposes. The highly efficient photodegradation process for the removal of 45% and 90% methylene blue dye under VIS and UVC light irradiation, respectively has proved the potential photo-degradative properties of these fullerene-modified silica materials. The key parameters that control photodegradation are quite high specific surface area (395m2/g) of silica support, very low content of C60 (0.04%) and the size effect promoted by homogeneous dispersion of C60 nanoclusters (10nm) in SiO2 support. The enhancement of photodegradation efficiency is interpreted in terms of band gap energy and zeta potential values of the nanostructures under study.

Zero valent Ag deposited TiO2 for the efficient photocatalysis of methylene blue under UV-C light irradiation

Zero valent silver nanoparticle deposited TiO2 composite (Ag/TiO2) has been prepared and characterized by SEM, TEM, XPS and FTIR techniques. The photocatalytic property of Ag/TiO2 for the degradation of methylene blue (MB) was investigated under the ultraviolet-C light irradiation. The effect of various operation parameters such as solution pH, irradiation time, initial MB concentration and catalyst dose was also studied. The results indicated that an increase in solution pH boosted the photocatalytic degradation of MB by Ag/TiO2 reaching a maximum at pH9.0. The degradation of MB decreased from 96.66% to 45.76% with the rise in startup MB concentration from 3 to 13mg/L. An enhanced degradation of MB was noticed with the increment in the amount of composite from 0.025g to 0.1g and afterwards an increase in catalyst mass resulted in reduction in the degradation of MB. Moreover, Ni(II) amelioration in MB solution also showed an adverse effect on Ag/TiO2 activity.

Novel Floating Ag+-Doped TiO2/Polystyrene Photocatalysts for the Treatment of Dye Wastewater

Two different solvent-cast techniques, namely, impregnation and strewing, were used to immobilize silver-ion-doped titanium dioxide particles into and onto a polystyrene matrix. The developed floating photocatalysts were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy. The doped sheets were evaluated for their photocatalytic activity by the photodiscoloration of methylene blue dye in aqueous solutions at its natural pH under both ultraviolet (UV) and solar irradiation employing nonanchored and nonstirred conditions. The maximum color removal efficiency achieved by the doped strewn photocatalyst was about 94% and 83% under UVC (254 nm) light and solar irradiation, respectively. For the doped impregnated photocatalyst, the maximum photodiscoloration observed under UV light and sunlight was around 86% and 68%, respectively. The prepared photocatalysts can be easily recovered, and the photocatalytic activity was found to be sustained after three consecutive runs.

Synthesis, characterization and investigation photocatalytic degradation of Nitro Phenol with nano ZnO and ZrO2

ZnO and ZrO2 photo catalysts were synthesized by sol-gel auto combustion method. The products were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Structural and morphological properties of nano particles were investigated and the average crystalline size of ZnO and ZrO2 was obtained 44 and 51 nm, respectively. Also, photo catalytic degradation of Nitro phenol from aqueous solution by using nano scale ZnO and ZrO2 powders under UVC light irradiation was studied and degradation of Nitro phenol was 98% for ZnO in 40 minutes and 83% in 100 min for ZrO2.

Photo-Fenton-like treatment of K-acid: assessment of treatability, toxicity and oxidation products.

Photo-Fenton-like treatment of the commercially important naphthalene sulphonate K-acid (2-naphthylamine-3,6,8-trisulphonic acid) was investigated using UV-C, UV-A and visible light irradiation. Changes in toxicity patterns were followed by the Vibrio fischeri bioassay. Rapid and complete degradation of K-acid accompanied with nearly complete oxidation and mineralization rates (>90%) were achieved for all studied irradiation types. On the other hand, detoxification was rather limited and did not change significantly during photo-Fenton-like treatment. Several oxidation products could be identified via liquid chromatograph-mass spectrometer analyses, such as desulphonated and hydroxylated naphthalene derivatives, quinones, and ring-opening as well as dimerization products. Photo-Fenton-like treatment of K-acid with UV-C, UV-A and visible light irradiation occurred through a series of hydroxylation and desulphonation reactions, followed by ring cleavage. A common degradation pathway for photo-Fenton-like treatment of K-acid using different irradiation types was proposed.

Optimization of UV/inorganic oxidants system efficiency for photooxidative removal of an azo textile dye

In this paper, photooxidative removal of C.I. Basic Red 46 (BR46) as a model organic pollutant was investigated in the presence of UV/inorganic oxidants system. The aim of this study was to evaluate the efficiency of hybrid oxidant system including inorganic oxidant species such as persulfate (S2O82-), peroxymonosulfate (HSO5-), periodate (IO4-), bromate (BrO3-), and chlorate (ClO3-) under UV-C light irradiation. The effect of various inorganic oxidants concentration in different reaction times was predicted and optimized in the photooxidation process using response surface methodology. It was found that the concentration of inorganic oxidants significantly affected the removal rate of BR46. Modeling results showed that the predicted values of removal efficiency were found to be in good agreement with the experimental results with a correlation coefficient (R2) of 0.9462. Optimization results showed that maximum removal efficiency (95.51%) was achieved at the optimum oxidants concentration: BrO3- of 118 mg L−1, ClO3- of 24 mg L−1, S2O82- of 1035 mg L−1, HSO5- of 232 mg L−1 and IO4- of 267 mg L−1 in reaction time of 23 min. Effect of oxidants concentration on the photooxidative removal of BR46 was estimated by the response surface and contour plots. Furthermore, the photooxidative removal efficiency of hybrid oxidant system mode was compared with individual processes. The obtained results clearly demonstrated that experimental design approach was one of the useful and cost-effective methods for modeling and optimizing the efficiency of UV/inorganic oxidants system. Mineralization study showed 84.4% reduction in total organic carbon value after 90 min of process.

EFFECTIVENESS OF UV-C IRRADIATION ON GROWTH OF POST-INOCULATED LISTERIA MONOCYTOGENES ON FRESH-CUT BROCCOLI

Ultraviolet (UV) light irradiation has demonstrated positive effects as a postharvest treatment in prolonging the storage life of fresh produce and as a non-thermal method of inactivation of pathogenic microorganisms. The objective of this research was to study the effectiveness of UV-C light irradiation as a postharvest treatment on the subsequent attachment and growth of human pathogens on fresh produce. Fresh-cut broccoli is highly perishable and susceptible to deterioration and contamination by pathogenic microorganisms after harvest. Fresh-cut broccoli branchlets were treated with UV-C doses of 2.5 and 5 kJ/m2 and inoculated with Listeria monocytogenes at various times (0, 6 and 24 h) after treatment. Growth of the bacteria on UV-C treated surfaces of broccoli branchlets was evaluated by extracting and enumerating the microorganisms on day 3, 4, 6, and 8 after treatment. Results of the study show UV-C irradiation at a dose of 5 kJ/m2 was able to restrict the growth of L. monocytogenes in the samples inoculated 24 h post treatment, with no significant differences (P=0.05) in colour and weight loss of the broccoli compared to the control treatments. These results imply UV-C treatment may be effective not just in controlling pre-existing pathogens but also reducing the risk of post-harvest contamination. Previous studies have suggested that mild stress produced by UV-C light irradiation stimulates the synthesis of defence related phytochemicals in broccoli (such as glucosinolates) which also offer a variety of health benefits. It is not yet clear whether this mechanism is also responsible for the restriction of L. monocytogenes attachment and growth after UV-C irradiation.

The effect of He-Ne Laser and UVC irradiation on sperm head morphology and DNA of testis for albino mice(Mus musculus)

In vitro, He-Ne laser show a modifying response of cells to ionizing radiations. So there is a need to investigate this property in vivo.To investigate the effect of He-Ne laser (632.8nm) pre and post irradiation against the UVC (253.7nm) irradiation in vivo on the sperm morphology, and DNA of testis in Mouse. In this study Twenty adult albino male mice were divided into four groups, the first group was He-Ne laser irradiated, and the second group was UVC irradiated. The third group was pre-irradiated by He-Ne laser followed by UVC irradiation, with one hour time interval between the two irradiations. The fourth group was pre-irradiated by UVC then by He-Ne laser, with one hour separating the two irradiations. The He-Ne laser per-irradiation show a protection properties, which appeared on both sperm head abnormality and DNA damage against UVC light irradiation. Four sperm head abnormality features were found after each type of irradiation. But the He-Ne laser preirradiation against UVC irradiation lower the frequencies of sperm head abnormality, farther more reduce the DNA testis damaging. Both UVC and He-Ne laser irradiations revealed a toxic effect on sperm head morphology, but the HeNe laser was found less effective. The He-Ne laser protective properties was observed only when He-Ne laser irradiation was applied before the UVC irradiation.

Study of the Photodegradation Process of Vitamin E Acetate by Optical Absorption, Fluorescence, and Thermal Lens Spectroscopy

The stability of vitamin E acetate exposed to ultraviolet (UV) light was studied using three spectroscopic methods. An ethanol solution of vitamin E acetate was treated with either UVC light (254 nm) or UVA light (366 nm) during a period of 10 min followed by a study of UV–Vis optical absorption, then by fluorescence spectroscopy excitation by UV radiation at either 290 nm or 368 nm and, finally the solution was studied by thermal lens spectroscopy. Immediately, the same solution of vitamin E acetate was subjected to the UV irradiation process until completion of six periods of irradiation and measurements. UVC light treatment induced the appearance of a broad absorption band in the range of 310 nm to 440 nm with maximum absorbance at 368 nm, which progressively grew as the time of the exposure to UVC light increases. In contrast, UVA light treatment did not affect the absorption spectra of vitamin E acetate. Fluorescence spectra of the vitamin E acetate (without UV light treatment) showed no fluorescence when excited with 368 nm while exciting with 290 nm, an intense and broad emission band (300 nm to 440 nm) with a maximum at 340 nm appeared. When vitamin E acetate was treated with UVC light, this emission band progressively decreased as the time of the UVC light irradiation grew. No signal from UV-untreated vitamin E acetate could be detected by the thermal lens method. Interestingly, as the time of the UVC light treatment increased, the thermal lens signal progressively grew. Additional experiments performed to monitor the time evolution of the process during continuous UVC treatment of the vitamin E acetate using thermal lens spectroscopy exhibited a progressive increase of the thermal lens signal reaching a plateau at about 8000 s. This study shows that the vitamin E acetate is stable when it is irradiated with UVA light, while the irradiation with UVC light induces the formation of photodegradation products. Interestingly, this photodegradation process using the study of the thermal lens effect could be followed closely even though poor absorption of the photodegraded product of the vitamin E acetate was observed at the laser wavelength used. As the thermal lens method allowed for accurate monitoring of the extent of photodegradation of the vitamin E acetate, this study opens the photodegradation process as a new application to be added to the recent applications of thermal lens spectroscopy in chemical analysis.

Photocatalytic oxidation of 2,4,6-trinitrotoluene in the presence of ozone under irradiation with UV and visible light

Under irradiation in the presence of ozone the photocatalytic mineralization of 2,4,6-trinitrotoluene, proceeded at a significantly higher rates, compared to those in the presence of O 2 only and they depend on the UV light source energy. ► The effectiveness of the 2,4,6-trinitrotoluene (TNT) degradation, catalysed by nanosized Au/WO 3 /TiO 2 photocatalysts was accelerated upon adding O 3 to the oxygen. ► In the presence of O 3 the rate constants of TNT destruction increased from 6 to 21 times. ► Doping of the semiconductor materials with gold nanoparticles increases 1.4–2.2 times the rate constants of TNT mineralization. The photooxidation of 2,4,6-trinitrotoluene (TNT), catalysed by nanosized photocatalysts: TiO 2 , WO 3 /TiO 2 , Au/TiO 2 and Au/WO 3 /TiO 2 was studied under irradiation with UV or visible light in the presence of O 2 or O 2 –O 3 mixture. The photocatalysts were characterized by the BET, XPS, TEM methods and adsorption of the model pollutant. The effectiveness of the processes of under UV-A, UV-C and visible light irradiation destruction in the presence of O 3 , photocatalysed by the WO 3 /TiO 2 , Au/TiO 2 and Au/WO 3 /TiO 2 samples is considerably higher than that registered in process, occurring with pure TiO 2 . Thus in the presence of O 3 the rate constants of 2,4,6-trinitrotoluene photooxidation under UV-A, UV-C and visible light irradiation catalysed by Au/WO 3 /TiO 2 are respectively 2.1, 1.4 and 6.2 times higher than that registered with pure TiO 2 . On the other side the ozone rate constants of 2,4,6-trinitrotoluene photooxidation under UV or visible light irradiation are also much higher than those, registered in the presence of O 2 only. Thus under UV light irradiation the O 3 rate constants of 2,4,6-trinitrotoluene photooxidation, catalysed by Au/WO 3 /TiO 2 are 6 times higher, while under visible light they are 11 times higher than those with oxygen only. Under irradiation with UV-A, UV-C and visible light in the presence of ozone a synergistic effect has been registered, expressed most strongly in the case of TNT destruction, photocatalysed by Au/WO 3 /TiO 2 . Doping of the semiconductor materials with gold nanoparticles increases 1.4–2.2 times the rate constants of 2,4,6-trinitrotoluene mineralization, compared to the undoped samples, which is due to more efficient separation of the electron–hole charges generated upon irradiation.

Investigation of the effect of sol–gel synthesis variables on structural and photocatalytic properties of TiO 2 nanoparticles

In the present study, titanium dioxide nanoparticles were synthesized by sol–gel method, from various precursors in some solvents under different synthesis conditions such as solvent percent, water percent, reflux temperature, reflux time, sol drying method and calcination temperature. Structure, size, band gap and specific surface area of nanoparticles were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis reflectance spectroscopy (DRS) and BET analysis methods. The photocatalytic activity of TiO 2 was evaluated in the photodegradation of C.I. Acid Red 27 as a model contaminant from textile industry under UV-C light irradiation. Results indicate that structure and photocatalytic activities are functions of precursor type, solvent type and other synthesis conditions. TiO 2 nanoparticles synthesized in the presence of methanol as solvent and titanium (IV) isopropoxide as precursor under 3 h reflux at 80 °C with sol thermal drying and calcination temperature of 450 °C indicate high photocatalytic activity in comparison with TiO 2–P25 (Degussa Co.).

Application of the UV-C photo-assisted peroxymonosulfate oxidation for the mineralization of dimethyl phthalate in aqueous solutions

In this study, the degradation of dimethyl phthalate (DMP), taken as model compound for phthalate esters, by the photo-assisted peroxymonosulfate (PMS) process was investigated. The high oxidation potential of hydroxyl and sulfate radicals generated by the activation of PMS under UV-C light irradiation was used to completely oxidize aqueous DMP solutions. Experiments were conducted at varying initial pH values (3.0, 6.0, and 9.0) and PMS concentrations (0-60 mM) to evaluate the effect of different reaction conditions on DMP treatment performance with the PMS/UV-C process. It was observed that lowering the initial reaction pH slightly improved the degradation rate of DMP. On the contrary, TOC abatements were slightly enhanced with increasing initial reaction pH. An adequate (optimum) PMS concentration of 40 mM resulted in the fastest and highest DMP degradation rates and efficiencies, respectively. At an initial concentration of 100 mg L(-1), more than 95% DMP removal was obtained after only 20 min under PMS/UV-C treatment conditions. For the proposed adequate PMS concentration (40 mM) the lowest electrical energy per order (EE/O) value was calculated as 2.9 kW h m(-3) order(-1).

Fenton oxidation treatment of tannery wastewater and tanning agents: synthetic tannin and nonylphenol ethoxylate based degreasing agent

In the present experimental work, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreasing wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes. FO and PFC oxidation experiments were performed in batch reactors for 30 min at pH 3 ± 0.2 and 40–45°C, considering the actual temperature and pH values of retanning bath effluents. For the FO experiments the effect of varying Fe2+ and H2O2 concentrations and UV-C light irradiation on oxidation measured by the parameters COD, UV254 and UV280 absorbancies was studied. Toxicity of untreated and FO, PFC-treated synthetic solutions to the freshwater cladoceran Daphnia magna was also tested. PFC provided appreciably high COD (>80%) and UV254 and UV280 (>90%) removals for ST. The toxicity could be drastically reduced in the PFC-treated ST sa...

Thermal stability and inactivation of hepatitis C virus grown in cell culture

BackgroundHepatitis C virus (HCV) is a blood-borne flavivirus that infects many millions of people worldwide. Relatively little is known, however, concerning the stability of HCV and reliable procedures for inactivating this virus.MethodsIn the current study, the thermostability of cell culture-derived HCV (HCVcc, JFH-1 strain) under different environmental temperatures (37°C, room temperature, and 4°C) and the ability of heat, UVC light irradiation, and aldehyde and detergent treatments to inactivate HCVcc were evaluated. The infectious titers of treated viral samples were determined by focus-forming unit (FFU) assay using an indirect immunofluorescence assay for HCV NS3 in hepatoma Huh7-25-CD81 cells highly permissive for HCVcc infection. MTT cytotoxicity assay was performed to determine the concentrations of aldehydes or detergents at which they were no longer cytotoxic.ResultsHCVcc in culture medium was found to survive 37°C and room temperature (RT, 25 ± 2°C) for 2 and 16 days, respectively, while the virus was relatively stable at 4°C without drastic loss of infectivity for at least 6 weeks. HCVcc in culture medium was sensitive to heat and could be inactivated in 8 and 4 min when incubated at 60°C and 65°C, respectively. However, at 56°C, 40 min were required to eliminate HCVcc infectivity. Addition of normal human serum to HCVcc did not significantly alter viral stability at RT or its susceptibility to heat. UVC light irradiation (wavelength = 253.7 nm) with an intensity of 450 μW/cm2 efficiently inactivated HCVcc within 2 min. Exposures to formaldehyde, glutaraldehyde, ionic or nonionic detergents all destroyed HCVcc infectivity effectively, regardless of whether the treatments were conducted in the presence of cell culture medium or human serum.ConclusionsThe results provide quantitative evidence for the potential use of a variety of approaches for inactivating HCV. The ability of HCVcc to survive ambient temperatures warrants precautions in handling and disposing of objects and materials that may have been contaminated with HCV.