The Construction Of Iron(?) Oxalate Fenton Like System For The Degradation Of Alachlor

The fast development of technology and science make people's lives become more convenient.However,the environmental pollution comes along and is getting worse day by day.The emission of industrial waste,Irrational using of pesticides and the emission of sewage make water pollution worse.It was reported that pesticides can be used to protect crops from grasses and pests.However,the irrational use of pesticides may result in the residual of some harmful ingredients in the soil.Through raining and run-off,these residual pesticides may enter water.Alachlor is a pre-emergence herbicide,which is widely used to control most annual grasses and many broadleaf weeds.Alachlor was detected in water all around the world because of its stability and solubility.Alachlor may hurt people's skin,eyes liver and it can even induce cancer with long-term exposure.However,alachlor can hardly completely photolysis in the natural environment Therefore,the development of novel processes for total degradation of alachlor is highly desire.Fenton oxidation process,which can generate ·OH by the reaction of ferrous ions and H2O2,shows great performance on the degradation of pollutants.It has attract great attention for the advantage of easy operation,low-cost,and mild reactive condition.But,several drawbacks are still existed,including the low utilization of H2O2,narrow pH response range(pH = 2.5-3.5)and the production of iron sludge.It was reported that Iron-organic complexes can prevent the production of iron sludge and realize the effective Fe3+/Fe2+ cycle which can promote the utilization of H2O2.However,the crystallized Iron-organic complexes used in Fenton like system have not been reported.Iron(II)oxalate,which has a one-dimensional(1D)chain composed of ferrous ions and oxalate,is a typical layered material.Because of the different assembly of one-dimensional chain by hydrogen bond,it has two crystals,?-FeC2O4·2H2O and?-FeC2O4·2H2O.Our group has demonstrated that a-FeC2O4·2H2O Fenton like system can degrade pollutants and it has wide pH response range,but it still shows low utilization of H2O2.Therefore,this paper is aiming to construct high efficient Iron(II)oxalate Fenton like systems and fully study its mechanism for the degradation of pollutants.Firstly,we used heating method in vacuum condition to synthesize FeC2O4 for the degradation of alachlor.We demonstrated tHat this process include both homogeneous'Fenton reaction and heterogeneous Fenton reaction.Compare with a-FeC2o4·2H2O,FeC2O4 show greater reactive activities on two types of reactions.By using trapping experiments,we found ·OH is the main reactive species.At the same time,we also used GC-MS to investigate the intermediates of alachlor and its degradation pathway.In addition,the TOC analysis show alachlor can be mineralized.Finally,we purposed the mechanism of H2O2 decomposition over FeC2O4 for degradation of alachlor.Though FeC2O4 Fenton like system shows great performance on the degradation of alachlor,it still has some disadvantages including a great deal of Fe2+ releasing from FeC2O4 and the narrow pH response rage.Therefore,we synthesized more stable?-FeC2O4·2H2O and constructed a Fenton like system in alkaline condition for the degradation of alachlor.Compare to ?-FeC2O4·2H2O system,?-FeC2O4·2H2O show higher reactive reaction.The control experiments demonstrated that the main active sites are Fe2+ on the surface of ?-FeC2O4·2H2O.XPS result shows ?-FeC2O4·2H2O is less likely to coordinate with hydroxyl ions(OH-)than a-FeC2O4·2H2O.That is the reason why ?-FeC2O4·2H2O show greater performance for the degradation of alachlor in alkaline condition.The intermediates of alachlor are also investigated.In summary,we demonstrated that Iron(?)oxalate Fenton like system has high reaction activities on the degradation of alachlor.This work also has theoretical significance on the application of Iron(?)oxalate Fenton like system in the actual environment.