Study On Removal Of Acidic Orange ? And Alachlor With Iron-based Micro-nanomaterials

The water pollution caused by various chemicals has become one of the most serious problems in the world.Water pollution not only leads to deterioration of water quality,but also affects a series of ecological environment,such as soil and atmosphere.Moreover,it will threaten human health by affecting potable water and agricultural products.Therefore,we should not only prevent the discharge of wastewater,but also treat the polluted water to an appropriate standard.In the past few decades,scholars had developed a variety of micro-nanotechnologies to deal with wastewater.Researchers had synthesized various micro-nanomaterials for water remediation and treatment,and achieved a lot results.In this study,we synthesize zero-valent iron(mnZVI)material and zero-valent iron copper bimetal(mnFe/Cu)material with micro nano hierarchical structure,and they are respectively applied to the removal of azo dyes acid orange ?(AOII)and amide herbicide alachlor(Ala).1.Removal of acid orange II(AOII)with mnZVI:In air atmosphere.mnZVI can quickly and thoroughly remove the AOII,that is,20 mg/L AOII is completely removed by 0.17 g/L mnZVI in 120 s,and the rate constant is 0.031 s-1(800 times higher than that of the reported mnZVI,7000 times higher than that of the reported nZVI).The removal reaction conforms the pseudo first order kinetics.Almost all the acid orange II is removed within 90 s under Ar condition,and the reaction rate is 1.16 times faster than that under air condition.The high-resolution XPS spectra of mnZVI after aerobic reaction reveals that the surface iron oxide(FexOy)content is high,and hinders electron transfer.The result of ESR shows that the reaction of mnZVI and H2O instantly produces a large number of hydrogen radicals(·H)with high reduction activity.We systematically study the reaction mechanism and the degradation pathway of the acid orange II in the mnZVI/AOII/Air system by the results of aerobic/anaerobic experiment,UV-Vis,HPLC and theoretical calculation.2.Removal of alachlor(Ala)with mnFe/Cu:In air atmosphere,20 mg/L Ala is completely removed by 1 g/L mnFe/Cu within 30 min,and the rate constant is 11.36 times faster than that under Ar atmosphere.The removal rate of alachlor is 8 times higher than that of mnZVI,and the removal reaction fits the pseudo first-order kinetic model.After the hydroxyl radical(·OH)of the mnFe/Cu/Air system is captured by the tert-Butanol(TBA),the removal rate of Ala is reduced from 100%to 23%,indicating that the degradation of Ala is mainly oxidation of· OH.The rapid removal of Ala can be attributed to the following aspects:(1)The incorporation of zero-valent copper makes the material exhibit higher porosity and specific surface area;(2)Cu0 can reduce Fe3+ to Fe2+totally,Fe2+ can activate molecular oxygen and promote the process of Fenton reaction,and produce a great deal of ·OH;(3)The mnFe/Cu has a lower corrosion potential(-0.3 eV),which has a stronger electron donating ability.The dechlorination rate of Ala is 100%.Through analysis of the intermediate products by GC-MS,we propose the reaction mechanism of mnFe/Cu/Air Fenton-like system to degrade Ala and the degradation pathway of target pollutants.