Study On The Mechanism Of Fulvic Acid Mediating Iron/arsenic Migration Conversion

Fulvic acid(FA)is an important part of humus,which has an important influence on the reduction and dissolution of iron(Fe)oxides and the migration and transformation of arsenic(As)in the environment under the action of microorganisms.Goethite and hematite are two common iron(hydrogen)oxides in nature,and their environmental geochemical behavior is usually coupled with the migration and transformation of As.This paper focused on the study of the interfacial behavior of FA–As-bearing iron ore,and constructed microbial–FA extracted from lignit(FAL)/plant peat(FAP)–As-bearing goethite/hematite composite system,and carried out differential mechanism study of FA mediated Fe/As migration and conversion by microbial action.Comparing the synchronous change characteristics of Fe/As,the fluorescence spectra,FTIR in various experimental systems under different conditions.Revealing the differential mechanism of Fe/As migration and transformation of different sources of FA under different influencing factors.In order to provide further experimental evidence for FA mediated Fe/As biogeochemical cycling.The main findings are as follows.1.The results indicated that FA can significantly promote the Fe/As reduction driven by microorganisms,since the Fe/As with added FA has about twice as many electrons as the without FA,and FA as an electron shuttle,has a stronger reduction effect on Fe/As than as an electron donor.2.The results showed that FAL has a stronger ability to mediated Fe/As reduction than FAP.Since the peak intensity of FA-like fluorescence peak in FAL is stronger than that of FAP,and electron transfer ability of FAL is stronger than that of FAP,therefore,FAL mediates the reduction of Fe/As better than FAP under the same conditions.3.FA mediated Fe/As reduction is closely related to the type of arsenic-bearing iron ore.Goethite is more easily reduced than hematite due to its low crystallinity,large specific surface area and high content of functional groups.Therefore,the Fe/As reduction level of the arsenic-bearing goethite ore group is higher than that of the arsenic-bearing hematite group.4.It was found that hydroxyl,carboxyl,aromatic,aldehyde,ketone,and aliphatic groups were the main electron-donating groups.It is calculated that the relative peak areas of various functional groups account for hydroxyl groups(23～38%),carboxyl groups,aromatic groups,aldehydes and ketones(8～24%),and aliphatic groups(9～15%).Based on the relative peak area ratios of the above functional groups,a general sequence of redox ability of each group was derived: hydroxyl group >carboxyl group,aromatic group,aldehydes,ketones > aliphatic group,indicating that hydroxyl group is the primary key group involved in Fe/As reduction under the present experimental conditions.5.In the experimental system,Fe reduction promotes As reduction,which provides experimental corroboration for the study of the driving mechanism of Fe on As cycle due to Fe gaining electrons before As.