Study On The Characteristics Of Chemical Reaction Between Humic Acids With Different Levels Of Molecular Weights And Aluminum In Coagulation Process

Humic acids is a kind of mixture with complex structures, and it always brings aseries of hazards to human. With the help of financial assistance of the national sciencefund, by means of PDA、the analysis method of floc’s strength、FR、 GC-MSanalyses,this paper mainly study the reaction and characteristic of humic acids withdifferent levels of molecular weights and the aluminum. then we can provide anfundamental theory for the harm of waters caused by the humic acids.Raw material extract from lake sediment. IHSS recommended method forpurification of sediment to natural humic acid, and by elemental analysis (EA) C, O, N,H,S elements, accounting for the total98%. The ultrafiltration hierarchicalcharacterization of humic acid and organic carbon mass balance calculations, theresults show that humic acid with molecular weight>30k is much higher than others，Accounting for41.03％, molecular weight <1k substances less，Accounting for41.03％.From Pyrolysis GC-MS analysis result，we can come to the clusion that humicacids with different molecular weights level compose by a simple chain hydrocarbonsubstances(Acids, alkanes, alcohols, esters)、Aromatic substances and their derivatives,nitrogen-containing heterocyclic substances, as well as multi-ring naphthenes materialcomposition; The molecular structure of humic acids with molecular weights>30k arethe spatial structure of the macromolecular ring, and with a benzene ring, hydroxyl,carboxyl, methyl, and other functional groups; The molecular structure of humic acidswith molecular weights10k~30k are chain structure, a benzene ring with hydroxyl and carboxyl, the heterocyclic nitrogen atoms; The molecular structure of humic acids withmolecular weights5k~10k are relatively simple, mainly benzene ring-based bandstructure of the chain hydrocarbons and nitrogen atoms and small molecules, but alsocontains nitrogenous substances.By means of the fluorescence scan the reaction of humic acids with differentmolecular weights and the aluminum salt at two tipical pH(pH=5,pH=7).The resultsshowed that humic acids with molecular weights>30k、10k~30k have high removalrate. Accounting for80％、50％. With the decreasing of molecular weights, thefluorescence intensity of humic acid become lower. Removal of humic acids withmolecular weights5k~10k are difficult under that two pH conditions. Accounting for35％.humic acid with molecular weight>30k containing carboxyl, hydroxyl, aminebenzene ring connected to the carboxyl, hydroxyl can be removed by coagulation.humic acid with molecular weight10k~30k with the carboxyl and hydroxylfunctional groups are effectively remove.chain hydrocarbon to remove ineffective.humic acid with molecular weight5k~10k basically does not react with aluminum,nitrogen-containing heterocyclic nitrogenous substances can hardly be removed in thecoagulation process.Through PDA floc monitoring, micro-photography, image analysis and othermethods, discuss the structural characteristics of humic acid floc by fractal theory. Theresults show that with molecular weight decreasa the fractal dimension of flocs reduce.The floc fractal dimension at pH=7.0greater than that at pH=5.0.