Activation Of Persulfate For Water Disinfection: Efficiency And Mechanisms

Depletion of water qualit y due to contamination of water bodies by recalcitrant compounds and microbial pathogens has become a serious global problem with increasing populations and uncertain global climate changes.In efforts to improve water qualit y,the inactivation of waterborne pathog ens for provision of safe potable water has bee n taken as a priorit y in health programs,as huge occurrence of mortalit y especiall y i n developing countries originating from microbial contaminated water.Unfortunatel y,Traditional water disinfection methods such as chlorination,ozonation and UV irradiation have many drawbacks and associated disad vantages.For example,a number of microorganisms are resistant to UV irradiation and chlorination;the high cost and safet y conce rns of ozonation limit its practical application;the formation of carcinogenic disinfection byproducts?DBPs?by chlorination and ozonation has become another serious environmental problem.Therefore,mor e safe and “green” water disinfection technologies are highly desired to achieve costeffective inactivation of pathogens and elimination of disinfection debris.The advanced oxidation technology based on activated persulfate has attracted much attention in recent years due to its strong disinfection abilit y,energy saving and environmental protection,no generation of toxic by-products and self-purification of the system.However,there are still limitations due to the currentl y used methods of activating persulfate,such as stabilit y,repeatabilit y,leaching and fouling of activators.In addi tion,the complexit y of these catal ysts increases the practical cost of mass production.Therefore,the work of this paper is to find an environmentall y friendly activation method and study its sterilization mechanism.The main research contents of this th esis are as follows:?1?Activate the persulfate with environmentall y-friendl y renewable visible light,and use the model strain E.coli K-12 to evaluate the inacti vation abilit y of the VL/PS system.107cfu/m L of the bacterial can be completel y inactivated within 120 min.·SO4-was the main active ROS in the system was detected by EPR and scavengers experiments.The mechanism of bacterial inactivation in system was studied.The levels of several antioxidant enz ymes and intracellular ROSs during the bacterial inactivation process were monitored,and the damage of chromosomal DNA was observed.From the scanning electron micrograph of bacteria,bacterial damage and even mineralization were observed,and according to these,a visible light activated PS st erilization mechanism was proposed.In addition,the versatilit y of the VL/PS system to inactivate other pathogens was studied,as well as the simulation of inactivation effects in natural water.?2?A composite magnetic?Fe₃O₄?carbon material with good visible light absorption and large specific surface area was synthesized by a simple method.It was then used to activate PS to inactivate the model strain E.coli K-12 in water.Under the synergistic effect of visible light,108 cfu/m L of bacterial can be completel y inactivation within 40 min.The scavengers experiment and EPR were also used to verify the bactericidal mechanism of the system,and the bacterial structure and DNA damage were also detected.The mechanism of activated PS bactericidal by visible light synergistic composite magnetic carbon material was proposed.