| Since the outbreak of the COVID-19 epidemic,the nucleic acid of the virus has been repeatedly detected as positive on the outer packaging of cold chain foods.Therefore,research on low-temperature disinfection technology for cold chain foods has received increasing attention.Acidic electrolyzed water（AEW）disinfectant has been widely studied due to its strong adaptability,high efficiency,and harmlessness.Therefore,this article aims to develop a new type of low-temperature acidic electrolyzed water（LT-AEW）disinfectant and conduct a detailed evaluation of its antifreeze temperature,disinfection effect,and practical application.The bactericidal effect of AEW is related to the effective chlorine content（ACC）in it,while ACC is affected by the electrodetic electrode evolution reaction activity in the anode region.Ir O2-Ta2O5 electrode has good chlorine and oxygen evolution activity,good stability,but low chlorine precipitation selectivity.In this paper,the Ir O2-Ta2O5 composite oxide was modified to improve the selectivity of chlorine evolution.Different metal oxides were modified to the surface of the Ir O2-Ta2O5electrode by magnetron sputtering technology and electrochemically tested.Among them,the Sn O2@Ir O2-Ta2O5 electrode had the best chlorine evolution selectivity,and its chlorine evolution oxygen potential differenceΔECER-OER was 354 m V,which was significantly higher than that of Ir O2-Ta2O5 electrode by 226 m V.Further Sn O2@Ir O2-Ta2O5 electrodes with different tin oxide contents were prepared by thermal decomposition.Among them,no Sn oxide diffraction peak was observed in the XRD spectra because of the reduced amount of modified tin oxide.XRF characterization found that the maximum loading of Sn element reached 54.165μg cm-2.XPS showed that there was a significant electron transfer between Ir,Ta and Sn,resulting in a change in their electronic structure.SEM analysis found that after the addition of tin oxide,the particle size on the electrode surface increased slightly,which could effectively increase the reaction area of the electrode.Electrochemical experiments showed that the chlorine evolution superpotential（271 m V）of Sn O2@Ir O2-Ta2O5-5 was 60 m V lower than that of Ir O2-Ta2O5 electrode at the same current density.Moreover,ΔECER-OER increased by 52 m V,indicating that the Sn O2@Ir O2-Ta2O5-5electrode has excellent CER selectivity.When AEW was prepared with Sn O2@Ir O2-Ta2O5-5 electrode,the electrolysis efficiency increased by 11.8%,the logarithmic killing value of Escherichia coli increased by 2.85log10(CFU·m L-1),and the KL of Bacillus subtilis increased from 2.98 to 4.92log10(CFU·m L-1).In this experiment,AEW was efficiently prepared using Sn O2@Ir O2-Ta2O5-5electrode,and AEW suitable for low temperature is further investigated below.Firstly,AEW is compared with different antifreeze agents,and it is concluded that20%wt Na Cl,25 wt%Ca Cl2,30 wt%EG,15 wt%EA and 35 wt%PG can make the antifreeze temperature of AEW reach-18°C.Then,the effects of antifreeze addition on the physicochemical properties of AEW were analyzed,and the results showed that 20 wt%Na Cl,25 wt%Ca Cl2,30 wt%EG and 35 wt%PG reduced ACC by 51%,75.7%,36.2%and 76.4%in AEW,respectively,while the addition of10 wt%EA to AEW could not detect ACC.Antifreeze has little effect on the p H of LT-AEW,but has a certain effect on the oxidation-reduction potential（ORP）of LT-AEW.The ORP values of LT-AEW decreased by 107,84,120 and 570 m V with increased Na Cl,Ca Cl2,EG and PG content,respectively.When the HCl O content is directly detected by ultraviolet spectrophotometry,it is found that the measured value is much larger than the actual content,and the HCl O content in different proportions of LT-AEW can be determined more accurately by adjusting the p H value of LT-AEW and combining the method of detecting Cl O-to calculate the HCl O content.After testing,the HCl O content in Ca Cl2-AEW accounted for an average of 48.1%in ACC,68.6%in Na Cl-AEW,82.3%in EG-AEW and 60.5%in PG-AEW.Perform low-temperature sterilization tests on E.coli at-1℃,-10℃and-18℃using Na Cl-AEW,Ca Cl2-AEW and EG-AEW.When the action time was 120 s,the KL value of ACC in Na Cl-AEW was greater than 100 mg/L for E.coli exceeding4.00 log10(CFU·m L-1).The KL value of ACC exceeding 120 mg/L in Ca Cl2-AEW exceeded 4.86 log10(CFU·m L-1);When the ACC value in EG-AEW reached95.51～106.85 mg/L,the KL value exceeded 5 log10(CFU·m L-1).The temperature and antifreeze content have little effect on the sterilization effect of LT-AEW.Through fluorescence microscopy and SEM analysis,it can be clearly observed that EG-AEW can damage E.coli cell membranes,allowing their contents to flow out,causing cell death.In the low-temperature field simulation test,the KL value of EG-AEW for E.coli attached to stainless steel sheet and corrugated cardboard at-18°C exceeded 3 log10(CFU·m L-1).In the LT-AEW stability test,it was found that the ACC of LT-AEW would decrease in a short time under the condition of sealing and protecting from light at room temperature,and it could be stored at 54°C for 11days after adding 0.01%sodium sulfamate.In addition to 35 wt%PG-AEW having almost no corrosion effect on metals,AEW,20 wt%Na Cl-AEW and 25 wt%Ca Cl2-AEW have a strong corrosion effect on iron paper clips,and 30 wt%EG-AEW makes paper clips have a slight corrosion phenomenon.In summary,compared with the above several different types of antifreeze,EG-AEW has a low influence on AEW,which is conducive to liquid maintenance in low temperature environment,has a low impact on the main bactericidal active ingredients in AEW,and has excellent sterilization effect,EG-AEW is suitable for disinfection and sterilization in low temperature environments such as cold chain food logistics. |
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