Degradation Of Sodium Dodecylbenzene Sulphonate And Atrazine By Zero-valent Iron Combining With Potassium Permanganate To Activate Sodium Persulfate

Sodium dodecylbenzene sulphonate?SDBS?,as a typical surfactant,will hinder the self-purification of water body.Once SDBS enter the water body,a large number of non-disappearing foams will produced,which suspend on the water surface and block the water-air interface.Long-term exposure to SDBS can cause serious damage to aquatic organisms Atrazine?ATZ?,as a common herbicides,is highly toxic to low-water animals,even low-level long-term exposure could interfere with the endocrine system of the organism.Nowadays,the efficient removal of these two pollutants,especially the advanced oxidation technology,has become a key problem.The advanced oxidation techniques based on sulfate radical have attracted great attention from researchers in recent years.Zero-valent iron?Fe⁰?can be used as a reducing agent as well as adsorbent and precipitant for pollutants in the environment and has been studied more frequently with hydrogen peroxide,sulfite,persulfate,and so on.Meanwhile,potassium permanganate?PM?and its reduction products(such as Mn⁴⁺,Mn³⁺,Mn²⁺,etc.)can be used to treat some refractory organic pollutants by activating persulfate?PS?or with zero-valent iron.However,there are few studies on zero-valent iron combined with potassium permanganate activated sodium persulfate to remove pollutants.In this research,Fe⁰-PS-PM process was used to remove SDBS and ATZ simulated wastewater.The single-factor experiments and orthogonal tests were used to determine the optimum process conditions of Fe⁰-PS-PM process.According to the degradation of pollutants from seven control tests of PS,PM,Fe⁰,PS-PM,Fe⁰-PM,Fe⁰-PS and Fe⁰-PM-PS,the surface morphology and elemental composition of Fe⁰ particles after reaction with Fe⁰ and Fe⁰-PM-PS systems were compared with electron microscopy-X ray energy dispersive spectroscopy?SEM-EDS?and the crystalline phase composition of the flocculant produced by the reaction of Fe⁰-PM-PS system were analyzed by X ray diffractometer?XRD?.The degradation mechanism of Fe⁰-PS-PM process to pollutants was preliminarily explored.The main results are as follows:?1?The single factor tests of degradation of SDBS by Fe⁰-PS-PM process showed that the concentration of Fe⁰,PM,PS,pH and the PM-PS feeding times had an effect on the removal rate of COD_Cr and TOC in the SDBS simulated wastewater.When the Fe⁰concentration increased from 5 g/L to 13 g/L,the COD_Cr degradation rate increased from39.1%to the maximum of 86.0%which was 53.1%higher than that without Fe⁰.When the concentration of Fe⁰ continued to increase to 20 g/L,the degradation rate of COD_Crr was reduced to 80.7%.The PM concentration increased from 5 mmol/L to 15 mmol/L,and the COD_Cr degradation rate increased from 82.7%to 96.3%which was 26.1%higher than that without PM system.PM concentration continued to increase to 25 mmol/L,and COD_Cr degradation rate decreased to 79.9%.When the concentration of PS increased from 5 mmol/L to 10 mmol/L,and the COD_Cr degradation rate increased from 48.3%to95.8%which was 39.6%higher than that without PS system.PS concentration continued to increase to 25 mmol/L,and COD_Cr degradation rate decreased to 86.3%.The removal rate of COD_Cr in acid solution was better than alkaline system,and the removal rate was98.3%when the simulated wastewater d id not adjust pH?about 8.55?.With the same amount of PM-PS added,the removal rate of COD_Cr increased with the number of feeding times.When the feeding times were 4,the COD_Cr removal rate reached 98%,which was 47%higher than the one-time dosing.Orthogonal test results showed that the concentration of zero-valent iron and sodium persulfate had a significant effect on the removal of SDBS without adjusting the pH of simulated wastewater.The order of influence of each factor was:Fe⁰ dosage>PS concentration>feeding times>PM concentration,and the optimum Fe⁰ dosage was 13 g/L,the concentration of PM was15 mmol/L,the concentration PS was 10 mmol/L and the PM-PS feeding times were 4.?2?The single factor?pH,Fe⁰ concentration,PS concentration,PM concentration,feeding times?tests of ATZ simulated wastewater by Fe⁰-PM-PS process showed that ATZ had a better degradation effect under acidic conditions,and the stronger the acidity,the higher the degradation rate of ATZ.When the original water did not adjust to pH,the degradation rate of ATZ was 80%.When the concentration of Fe⁰ increased from 0 g/L to10 g/L,the degradation rate of ATZ increased to a maximum of 90.4%.At a Fe⁰concentration of 12.5 to 20 g/L,the ATZ degradation rate gradually decreased from 88.6%to 78.3%.When the PS concentration was increased from 0 to 10 mmol/L,the degradation rate of ATZ increased to the maximum of 94.4%.The PS concentration continued to increase to 20 mmo/L,and the degradation rate did not increase significantly.When the concentration of PM was 2.5 mmol/L,the degradation rate of ATZ reached90.1%.The PM concentration continued to increase to 20 mmo/L,and the degradation rate did not increase significantly and the reaction rate constant k did not change much.The removal rate was 17.6%higher than that at one time with 3 of PM-PS feeding times.The orthogonal test results showed that when the PM-PS feeding times were 3 and the pH and potassium permanganate concentration had a significant effect on the degradation of ATZ.The influence degree of each factor was ranked as follows:pH>PM concentration>PS concentration>Fe⁰ dosage.The optimum pH was 5,Fe⁰ dosage was 10g/L,the concentration of PM was 2.5 mmol/L and the concentration of PS was 10mmol/L.?3?The combination of Fe⁰,PM and PS in the removal process of SDBS or ATZ has a synergistic effect.The removal mechanism is mainly oxidation and reduction,accompanied by adsorption and precipitation.Application of Fe⁰-PM-PS process to treat other refractory,toxic and hazardous waste water has good prospects.