Study On The Combined Effect Of Weak Magnetic Field And Anions On Chromium Removal From Water By Zero-valent Iron

The treatment of chromium pollution water was one of the problems that need to be solved urgently.The zerovalent iron?ZVI or Fe⁰?was widely used to eliminate chromium pollution due to its low price,low toxicity and convenient use.However,the normal zerovalent iron removal of Cr?VI?was less reactive and Cr?VI?could cause surface passivation of the zerovalent iron rapidly.To address the issue,this paper combined predecessors research,conducted the batch experiment and the continuous flow experiment,explored the influence and mechanisms of typical ions in natural water to ZVI removal Cr?VI?in the presence of WMF The results showed that:?1?The combined effect of weak magnetic field and anions could enhance the removal of Cr???by zerovalent ironIn ultrapure water with few electrolytes,the effect on the removal of pollutants by zerovalent iron with or without WMF was very weak.Perchlorate or nitrate anion with WMF could improve Cr???removal significantly.Chloride and sulfate could improve the activity of ZVI significantly eventhough without WMF,its promote effect has been amplified further more with WMF.For these four anions,the combined effect of weak magnetic field and anions appeared a hyperbolic change with increasing concentration of anion and tend to be stable finally.In addition,the combined effect varied as SO₄^2->Cl^->ClO₄^->NO₃^-from strong to weak.?2?The combined effect of WMF and anions has broad perspective on various contaminants removal by ZVI,and the simultaneous migration of anions and ferrous was the mechanism of combined effect.For different mechanism of pollutant removal by ZVI,such as As?III?,Se???,Sb?V?,WMF and anions could still increase corrosion rate of ZVI significantly,enhance removal efficiency effectively.Magnetic field gradient force was the major driving force to weak magnetic field promoted the activity of zerovalent iron,the paramagnetic ferrous ion moved along the magnetic lines towards the place with higher magnetic field flux intensity under the magnetic field gradient force,the existence of anions is the precondition for maintaining the continuous migration of ferrous.In order to maintain the electrical neutrality in the solution,anions would move along with the ferrous and maintain the constant corrosion of the zerovalent iron then improved activity.?3?Under the circumstance of continuous flow,the combined effect of WMF and anions still exist and had a long-term stability.Under the condition of continuous flow,conducting experiment with distilled water,Cr leak out through water in a short time before adding sulfate.Then sulfate was introduced,the combined effect of WMF and sulfate could keep the flow concentration of Cr kept under water quality standard following a long time.In solid phase,Fe mainly existed as Fe₃O₄,and there are obvious(Cr_0.336Fe_0.664)?OH?₃,Cr_0.336Fe_0.664OOH and other Fe-Cr complexes in the column with presence of weak magnetic field.Preparation simulated groundwater water or actual groundwater water for test,we had same conclusions.