Study On Bactericidal Effect Of The Modified Fenton Reagent And Its Regularity Of Hydroxyl Radical Production

The disinfection treatment is essential for drinking water,which usually by the way of adding chemical or using physical methods to reduce or eliminate the pathogens in the water.This study analyzed the strength and weakness of the present disinfectants.As the advantage of good effect,low cost and simple operation,the chlorine treatment has become the main method for water disinfection.However,the carcinogenic by-product of chlorine has large effect on the human.It is hoped to develop a safe and simple sterilization method to replace the commonly used chlorine treatment.The study introduced to develop a modified Fenton reaction by the use of organic acids and metal ions to form·OH,which the developed countries have started to pay attention on,and there is no report in China.This work is hoped to provide the theory to find a sterilization reagent that is kind to humans and the environment and widespread used,and lay the foundation for further research.E.coli was taken as the experimental strains to examine the bactericidal effect of the modified Fenton reagent.The results showed that(1)The higher concentration of L-AscA or acetic acid,the better bactericidal effect.But the E.coll.could not be entirely killed after 24h. (2)Although as little as 0.008 mM Fe²⁺was added in L-AscA,the E.coli was completely killed after 24h.The addition of Fe²⁺into Acetic acid improved the bactericidal effect,but the reagent of L-AscA and Fe²⁺is better at disinfection.(3)Under the condition of neutral salt in the modified Fenton reagent,low concentration of neutral salt had no effect on the disinfection,but high concentration can significantly hinder the sterilization.(4)With the mixing time increased,the reagent may decrease the bactericidal effect.Thus the reagent should be used for disinfection immediately after preparation.(5)The transition metal Cr³⁺, Mn²⁺,Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺were tried to added in L-AscA for experiment.And the combination of L-AscA and Cr³⁺,Fe²⁺,Cu²⁺ showed good bactericidal effects.Despite the reagent with Cu²⁺was very good at bactericide,as Cu²⁺is naturally toxic,the combination of L-AscA and Fe²⁺was considered as a good method for environment protection.With the spin trapping method,the generated·OH in modified Fenton reagents were detected by ESR.(1)Among the mixed reagents that have good bactericidal effects,only the combination of L-AscA and Cu²⁺could be detected the characteristic·OH-ESR spectrum.But when Cu²⁺added less than 0.002 mM,the spectrum couldn't be got.(2)When the density of E.coli or the contact time of E.coli and DMPO is changed in the L-AscA and FeSO₄ combination,the changes on ESR spectra are not obvious.It suggested that the E.coli influence the·OH generated ESR detection very small,not even.(3)In the mixture of L-AscA 0.01%, CuSO₄ 0.02mMand DMPO 1M,the most·OH was not generated at the beginning of the reaction but after 40min.At the same time,·OH could be continuously formed in a long time.(4)Only under aerobic conditions, the modified Fenton reagent of L-AscA and CuSO₄ could generated·OH effectively.(5)The combination of L-AscA0.01%and CuSO₄(0.001～0.02mM)were made up for ESR detection,from which a linear relationship was found between the peak height of·OH-ESR spectra and the Cu²⁺concentration.It showed that the formation of·OH is proportional with the Cu²⁺concentration under the experiment conditions.According to the SEM pictures,the E.coli death was not recognized by the cell surface damage.The results suggested that the·OH cause the inner injury,which is help to determine the direct mechanism of the killing.