Degradation Of 1,4-dioxane In Groundwater With Ultrasound Enhanced Iron Ore Or ZVI Activated Persulfate Oxidation Process

1,4-Dioxane is widely used in chemical production,found in many contaminated sites.Dioxane is chemically stable and is difficult to be biodegraded in the environment due to its toxicity.Persulfate oxidation is a method that can have a high degree of degradation of refractory organic,and has been studied in the treatment of organic pollutants in groundwater.However,this method has not been reported to be used for the degradation of dioxane in groundwater.In this paper,biotite,tourmaline,pyrite and ZVI were selected as activated sulphate materials to compare their ability to activate persulfate to degrade dioxane.At the same time,the factors affecting the degradation of dioxane were studied from the aspects of material addition and ion in groundwater.The results are as follows:First,a preliminary comparison experiment was conducted on the negligence of four materials activated persulfate degradation dioxane.Only pyrite and ZVI can be applied to activated persulfate degradation of dioxane.The results show that biotite and tourmaline can not release enough iron ions into the solution,leading to the persulfate can not be fully activated.The degradation rates of dioxane in the two systems were less than 30%.The main components of pyrite are FeS₂,iron oxide and iron salts.FeS₂ not only can reduce the Fe³⁺ in the solution to generate a large amount of Fe²⁺,but also can directly activate the sulfate,so pyrite system degradation rate of dioxane as high as 92.3%.ZVI system degradation rate also reached 93%.The main component of ZVI is Fe0,and the iron oxide formed on the surface of ZVI.Adequate Fe0 can continuously reduce the Fe³⁺ in the solution,maintaining Fe²⁺ as high concentration,so that the persulfate is fully activated.Secondly,the effects of ultrasound on the degradation of dioxane from pyrite and ZVI activated persulfate were studied.Ultrasound can significantly improve the degradation rate of dioxane,especially in the pyrite system,the enhanced effect of ultrasound from 74% to 92.3%.In the ZVI system,part of Fe0 can be directly converted to Fe²⁺ under the impact of ultrasound.The impact of ultrasonic waves on the ZVI surface also increases the mass transfer efficiency.For the pyrite system,ultrasonic waves can make the pyrite particles broken,increasing the contact area with the solution,thereby enhancing the efficiency of FeS₂ involved in the reaction.In addition,the ultrasonic can also activate the sulfate to produce SO₄^-.Finally,the effects of the amount of material added and the degradation of dioxane on groundwater were studied.Increasing ZVI,pyrite dosage and persulfate concentration can improve the degradation rate of dioxane.However,when Fe²⁺ is too much,there will be Fe²⁺ inhibition of the phenomenon.The reason is the competitive consumption of Fe²⁺ on SO4·-,and due to the activation of a large number of SO4·-is not involved in the degradation process led to self-quenching.High concentration of CO₃^2-,Cl-concentration is not conducive to the degradation of dioxane.Both ions can react with SO4·-and produce CO₃^2-and Cl-with lower oxidation-reduction potential,and reduce the oxidation capacity of the system.In addition,CO₃^2-can also form complexes or precipitates with iron ions in the solution,reducing iron ion concentration.